CA1279408C - System for configuring, automating and controlling the test and repairof printed circuit boards - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A method and apparatus for configuring, automating and controlling the testing and/or repair of printed circuit boards is presented. The apparatus includes one or more test and/or repair stations and conveyor units to transport PCB's and other components required to test and/or repair such printed circuit boards between such stations. The printed circuit boards are mounted in standardized carriers which facilitate intermixing different sizes and shapes of boards without requiring adjustment of the conveyor units. The other components such as the fixture assemblies required to electrically access the printed circuit boards are adapted to also be transportable by the same conveyor units. The apparatus further includes an automation interface to efficiently and accurately load and unload the PCB's and other required components to and from stages of certain stations, buffering stages associated with each station for temporarily storing PCB's and other components, and a distributed control system to facilitate the parallel processing of different types of PCB's in accordance with a dynamic priority rating system and a preemptive scheduling technique.

Description

Docket ~o. CIIl-103 ,~

SYSTEM FOR CONFIGURING, AUTOMATING AND CONTROLLI~G
THE TEST ~ND REPAIR OF PRINTED CIRCUIT BOARDS

Back~round of the Invention This invention relates generally to testin~
and/or repairing of printed circuit boards and more particularly to the configuring, automation and con~rol of a multiple station test and/or repair facility.
(The term printed circuit board as used herein refers generically to electrical circuit~ which are constructed on or within supporting strata. The use of this term is not intended to limit this invention to electrical circuits having conductive members formed by '~ "printing" technique~ nor to circuits formed on or ~ 15 within a supportin~ stratus o~ any specific : construction).
: In oraer to test such printed circuit boards (PCBs) it is necessary to establish electrical connection between the test equipment and selected - 20 nodes within the electrical circuits of the PCB.
Conventionally this electrical connection is acccmplished with a ~ixture assembly upon which.the PCB

i~ positioned. The fixture assembly incorporates a plurality of conductive probes (traditionally re~erred to a~ a bed of nails) which are selectivel~ positioned therein to correspond to predetermined electrical nodes on the PCB. After the PCB i8 positioned upon the fixture assembly the probes are biased into electrical contact with such nodes~ The various probes of the fixture as~embly are in turn electrically connected to ~timulus and measurement means within the te~t equipment which stimulate the nodes and which mea~ure the response~ which occur at the nodes of the PCB under te~t as a result of such stimulus. A separate fixture as~embly i~ generally required for each different PCB
to be tested due to the variation of the circuits of the PCB and of the electrical nodes located therein.
Since the electrical connection between the electrical nodes of the PCB and the test system is very critical, since the trend i8 to design PCBs with electrical nodes which are very densely packed, and since there is such a variation in the size and configuration of the di~ferent PCBs, the accurate loading or positioning of a PCB with respect to the ~ixture assembly and the accurate loading and positioning of the fixture assembly as well as the electrical connection of the fixture assembly to the stimulus and measurement means of the test equipment have typically been manual proces3es which make up an exce6~ively large proportion of the total te~t time. Attempts to automate such processes through the u~e of robotic arms or univeral fixtures have been limited due to the required accuracy, the inherent variablllty in the size, ~hape, complexity, and fragility of ~CBs, and the associated C08t and complexity of the robotic arm~ and the universal fixtures. Once a robotic arm is programmed it is al~o extremely difficult to alter the configuration of the operating modules between which the robotic arm i8 tasked to repetitively perform. Furthermore, neither the robotic arms nor the universal fixtures have achieved much ~uccess with reducing the amount of time required to load and position the fixture as~embly, load and po~ition the PCB with reRpect to the fixture assembly, maXe the electrical connection with the PCB, remove the PCB from the fixture a~sembly, and prepare the test equlpment for testing the next PCB
(especially if the next PCB has a different configuration). The~e concerns are compounded when multiple t86t and/or repair stations are employed in a test sy~tem.

Summary_of the Invention The present invention provide~ an apparatus and a method for quicXly configuring, automating and controlling the routing, testing and/or repairing of PCBs which substantially minimizes the aforementioned : 20 limitations and which can be used to automatically ~elect, transport, and loa~ the fixture assembly or comparable circuit means required to test or repair a given PCB; transport and position the PCB to be tested or repaired with respect to the circuit mean~;
electrically connect the same to the circuitry adapted to selectively te~t the electrical circuit~ of the PCB;
initiate the testing of the PCB determine in view of an interpretation of the test results whether the PCB
being tested is accepta~le, defective, or requires ` 30 additlonal testing or repair conduct the additional tests or remove the PCB from the circuit means and tran~port the PCB to another area with~n the test or repair system corresponding to the determined status of the PCB: determine whether there are other PCBs to be tested or repaired which will utilize the ~ame circuit means presen-tly loaded within the test system, and if so, sequentially transport and position one of such PCBs with respect to the circuit means or otherwise unlo~d the circuit means; and de~ermine whether there are other PCBs to be tested or repaired which require a different circuit mean~, and ~f so, select and load the appropriate circuit means, etc. It should be emphasized that ~he sy~tem according to the present invention i~ not ~trictly limited to testing Pcss. As will become apparent, stages can be advantageously included within the system to manufacture or repair PCBs, e.g. to insert or remove part~, to maXe adjustments to partsl to solder or unsolder parts, to burn in parts, etc. To emphasize the avallability of lS the3e alternative operations, this disclosure utilizes the terminology "test and/or repair" to generically refer to ~uch operations. For the saXe of brevity and readability such alternative language has not, however, been repeated in each and every instance. The failure, there~ore, to ~pecifically refer to both term~ should not be viewed as intentionally limiting the reference, for example, to strictly test operations.
The testing and/or repair of a PCB may requixe multiple stages and, therefore, the movement of the PCB from one stage to another. According to the present invention, reconfigurable modular conveyor units and automation interfaces are provided to efficiently transport and accurately load a PCB, for example, onto a selected test stage prior to the test and for removing the PCB from the test ~tage after the te~t. In the preferred embodiment of the system accordin~ to the present invention, the system further includes control means to efficiently route the PCB
through the various ~tages required to test and/or repair a given PCB. In its preferred embodiment the present invention further include~ mounting the PCB
within a carrier which is adapted to uniquely position and restrain the PCB therein. The carriers are adjustable to accommodate various shapes and sizes of PCBs and are adapted to facilitate the movement of the Pcs~ into and out of the various test stages of the test sy~tem by the automated conveyor means. The carriers include structure which in cooperation with other elements of the te~t system facilitate the precise positioning of the PCB with respect to the circuit means.
The invention further contemplates: the adaption of test fixture assemblies and vacuum cover assemblies (which a~emblies along with other items useful in PCB test and/or repair, and the PCB carriers are referred to herein as "components") for transport by the same conveyor system; control mean~ for coordinating, in accordance with a dynamic priority rating system and a preemptive scheduling technique, the transport of PCBs and associated components; an automation interface for loadin~, unloading, precisely positioning, and producing electrical enga~ement of a PCB and related components at a test stage; and buffering stage~ capable of holding and storing multiple PCBs and components. Other significant features of the invention are: its modularity which facilitates flexible configuring and extension of the test system; it~ ability to transport and automatically load te~t fixtures as well as printed ~ircuit boards wh~ch signifi~antly enhances the automation of the test process: and its automated programming capability which USe8 interactlve graphic~ to lay out a coniguration of the ~ystem and automatically generates ~he ~ystem interconnections andtcontrol programs needed to operate the so configured system.

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Description of the Accompanyin~ Drawings The present invention will be further descibed hereinafter with reference to the accompanying drawings wherein: -Figure 1 is a perspect.ive view of a testing system according to the present inven~ionr Figure la illustrates transport of a component between stations in a test an~/or repair system of the present invention;
Figure lb depicts alternate configurations of the cystem of Fig. 1.
Figure 2 is a perspective view of a carrier according to the present invention;
Figures 3 and 4 are partial sectional views ta~en along lines 3-3 and 4-4 respectively, of Fi~ure 2:
Figure 5 i.5 a partial end view of a conveyor unit according to the present invention:
Figure 5a depicts a pre.~erred component drive mechanism of a conveyor unit Figure 5b presents four views of a conveyor unit of the present inventlon;
Figure 5c i8 a partial sectional view taken along lines 5c-5c of Fig. 5;
- 25 Figure 5d pre6entQ five views of a conveyor unit having component rotational capabilitie~;
Figure 5e i~ a partial perspective view illustra~ing a component stop mechanism of a conveyor unit;
Figure 6 i8 a per~pective view of an automation interface according to the present invention;
: Figure 6a ~chematically depicts component movemen~ in a works~ation of the pre~ent invention:

Figures 6b, 6c and 6d are perspective views depicting sequential movement of a component into an automation interface;
Figure~ 7 and 8 are partial sectional views taXen along lines 7-7 and 8-8 respectively, of Figure 6;
Figure 7a i8 an exploded view of the driven roller mechanism of an automation interface;
Figure 7b is a top plan view of said drlven roller mechanism depicting, in phantom, displacement of the roller:
:~ Figures 7c and 7d are partial sectional and perspective views, respectively, depicting drive mechani~ms for the guide rails of an automation lS interface;
Figure 9 is a perspective view of a fixture assem~ly according to the present invention;
Figure 9a presents four views of the fixture assembly of Fig. 9;
Figure 9b is an exploded view illustrating the alignment of a stacked arrangement of components with an automation interface at a test stage:
Figure 9c is an exploded view of the fixture assembly of Fig. 9;
Figure 10 is a partial sectional view showing the relative po~itioning and location of the cover assembly, PCB, carrier, fixture a~sembl~, and circuitry connecting the same to a te~t stage:
Figure 11 is a perspective Vi2W of a cover aggembly according to the present invention;
Figure~ lla present a flow chart illustrating the operatlon o the.automation interface of the present invention~
Figure llb is an i~ometric view illustrating a mechani~m for varying the elevation of a cover a~sembly in an automation interface, F'igure llc illustrates the sandwiching of a PCB between two fixture as~emblie~;
Figure 12 i8 a perspective view of a buffering stage according to the present invention;
Figure~ 12a-12c are simplified perspective views illustrating the operation of a buffering stage in a workstation;
Figure 13 is a partial section view taken along line A-A of Figure 12 J
Figure 13a is an elevation showing the relationship between a buffering stage and conveyor units on either side thereof;
Figure 13b is an exploded view of drive wheel lS mechanisms of a buffering stage;
Figur0 13c is a top plan view of a buffering stage;
Figure 13d illustrates examples of a multi-station test and/or repair system constructed according to the present invention;
Figure 14 i8 a functional block ~iagram illustrating the interconnection of the various modules according to the present invention;
Figure 14a depicts an example of a decision tree for a type of PCB;
Figure 14b 1~ a block diagram of a typical control system of t~e pre~ent inventio~;
Figure lS i8 a flow chart illustrating the various ~teps of a method according to the present invention: and Figure 15a is a flowchart depicting a dynamic priority rating and preemp~ive schedulin~ ~ystem of the present invention.
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- 8a -For convenience of presentation, the following of the foregoing figures appears out of consecutive order and in the location stated: Figures 5, 5a and 5c follow Figure 6; Figures 5b(i)-(iv~ follow the sheet comprising Figures 5a and 5c; Figures 5d(i)-(v) follow Figures 5b(i)-(iv); Figure 5e follows Figures 5d(i)-(v); Figures 7a and 7b follow Figure 8; Figure 7c follows Figures 7a and 7b; and, Figure 7d follows Figure 7c.
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~, , Detailed Description of the Invention A perspective view illustrating various functional mod~les of the test system lO according to the present invention is provided in Figure 1.
Depending upon the complexity and type of circuit or PCB being tested ~t may be neces~ary to u~e multiple test stage~. It may also be necessary to use various combinations of test stages in different sequences to reliably locate the faults which might be present ~ therein. As can be seen, the ~ystem 10 can include such multiple test stages, for example, stages lla and llb~ The tes~ stage~ 11 can be identical, or they can - be of different types, e.g. functional, in-circuit, combinational, special device or component testers, bare board testers, etc. Such testors and the computer controllers employed to operate them are commercially available and therefor are not described in detail herein. Although Figure 1 illustrates two te~t stages 11, the present invention is not intended to be limited to this number nor to the descriptions provided above.
Conveyor meanR are provided to load and unload such PCBs and other transportable components from the test and/or repair stages and to transport such components there between. The conveyor means of the present ~5 ~nvention employs plug together, modular conveyor units which are specifically adapted to afford flexibility in the configuration of the test system lO. Conveyor unit 12 iq a linear conveyor which moves components in two directions, io e., ~owards as well as away from a ~tage.
It should b~ noted that such forwards and backwards motion i~ not commonly found in typical automated production lin~s whl~h generally transport the items - under process in one^common direction. A more complex motion is however re~uired to enable conveyor unit 12 ~5 to be utilized to transport components both in~o as well as out of a test stage 11, as i~ included in the present invention. To aford an even more flexible test and rep~ir system, a conveyor unit 13 is provided incorporating the capability for the rotational movement of the components in addition to linear movement. The need for the rotational movement capability of conveyor units 13 is illustrated in Figure la where an example transportable component 202 i8 trans~erred from the test station llh to a repair 3tation 15 (only the applicable portion of the system 10 being shown). The figure shows the progress of the transportable component 202 at intervals of time, not necessarily equal, as it i8 ~ransported through the system. In Figure la~iv), a conveyor unit 13 is shown lS a~ it is rotating 90 degrees counterclockwise in order to redirect the path of the transportable component 202. In Figure la~vi), another conveyor unit 13 is shown rotating 90 degrees clockwi~e to alter the path of the transportable component 202 once again. That the conveyor units 12 and 13 transport components in two directions i8 ap~arent in that the transportable component 202 in Figure la could al50 be transported from the repair ~tation 15 to the test station llb.
Direct routing paths are in fact available between any two ~tation~ in a system 10. Various combination~ of conveyor units 12 and 13 can be utilized to facilitate multiple arrangement~ of test stages 11 in order to optimize the te~t ~ystem 10 to the particular user requiremen~s, Utilizing different types of conveyor units 12 and 13 not only provides increased efficiency, but additionally allow~ a user to reduce the cost of the te~t ~ystem by utilizing the less expensive linear conveyor 12 for those application~ when rotational movement is not required. For example, the two conveyor units 12 labelled 200 and 201 in Figure la(i) do not need to rotate, and the less expensive conveyor unit 12 can be used. It al~o allows the user to ea~ily alter the configuration of the test system 10 as the requirements change.
Staqes other than test stages 11 can be included within the test system 10. For example, - Figure 1 illustrates a repair stage 15, such as a model 404 repair system which i~ commercially available from the Factron/Schlumberger division of Fairchild Camera and Instrument Corporation~ This repair stage 15 incorporates a repair and adjustment capability as well as a testing capability. A PCB can be diverted to stage 15 when repair (e.g. desoldering and replacement of components) or adjustments (e.g. repositioning of knobs or switches within the PCB) are required prior to completing the testing of the PCB. In addition, manual probing of the PCB may be accomplished such as may be required, for example, to trace a fault indicated as being on a common node having multiple connections thereto.
Buffering or set-up stages 16 are also included in system 10 to afford a smooth flow of components in and out of the variou6 te~t or re~air stages. The buffering stages 16 can also be utilized to form a storage Rtation S or PCBs and other components and in an input/output station 80 for the test system 10. A~ shown, the input/output station 80 also includes a conveyor module 12 and bar code reader 81 (the operation of which will be described herelnafter) and facilitates the loading and unloading o component~ into and out of the tes~ system.
As illustrated in ~i~. 1, as~ociated with each test stage 11, i8 an automation interface 38 which facilitateE the load~ng and electrical engagement of te~t fixture a6semblies and PCBs on the testor. The ~: .

-12~

construction and operation o~ automation interface 38 will be described in detail hereinafter. As shown in the plan view of Fig. lb(i), each test stage ll, together with it~ associated automation interface 38 and the immediately preceeding conveyor module 12 and buffering stage 16 define a test station TS.
Similarly, repair stage 15 and immediately preceeding conveyor module 12 and buffering stage 16 define a repair station RS.
Physically interconnecting the repair (RS), test (TsJ~ input/output (I/0) and storage (S) stations of test system lO is a transport system, generally denoted 18, consisting of a suitable arrangement of plug together conveyor units 12 and 13. The transport system allows direct routing of PCBs and other component~ from any station to any other station, in either direction, under the control of a ~aster control unit and distributed controllers. To illustrate the modularity of the system lO, alternate configurations of the system lO are shown in Figure lb in which all the same stations are used in three different configurations. Figure lb~i) shows the configuration of the system lO in a plan view as a reference. As an example, it may be desireable to interchange the locations of storage station S with the test station TSb in a particular application. This configuration is shown in Figure lb(ii). As a further example, it may be desireable to interchange the locations of the storage station S and the test station TSb, and al~o the repair station RS and ~he test station TSa. This configuration is shown in Figure lb(iii). In addition, each of the pictured configurations can be expanded to include additional conveyor units, buffering stages and/or test/repair stages, e.g. at the locations denoted "X" in Figures lb(i), (ii) and (iii). A

~ignificantly expanded sy3tem i3 shown in Fig. 13d. In the preferred embodiment of the invention, the number, type and physical layout of stations is determined based on the number of PCBs to be tested and/or S repaired, the number of test/repair stages required to process the PCBs and the physical ~pace requirements of the application. The details of the control system and the overall operation of te~t system 10 will be more fully explained after a detailed description of the - 10 system hardware is presentedO
To facilitate the movement of various PCBs throughout the te~t system 10 the present invention utilizes a carrier 20, which is ~est illustrated in Figure 2. The carrier 20 is designed to be adjustable to accommodate a wide range of sizes and configurations of PCBs 19. By utilizing adjustable carriers 20 the test system 10 can accommodate various ~izes and configurations of PC8s without requiring manual intervention or downtime to adjust the remainder of the test system 10 for a specific size or configuration PCB. By combining thls feature with other aspects of the present invention, the test system 10 of the present invention can concurrentl~ accommodate or intermix different PCBs 19, e.g. different shape~ and sizes. This i5 particularly useful and cost effective for users who do not consistently test a large volume of the same PCBs 19. The carrier 20 includes a frame having interconnected members 22a, 22b, 22c an~ 22d circum~cribing and thereby defining an interior area sufficiently large to accommodate the PCBs 19 which are intended to be tested. At least two of the interconnected members 22a and 22c are generally parallel to each other ~nd form opposing supports for tw~ suspension beams'23, The suspension beams 23 are mounted in a manner which facilitates the lateral -14~

adjustment of the suspension beams 23 along the members 22a and 22c tSee Fig. 3). The interior surface of each of the members 22a and 22c has a longitudinal channel 24 therein which i~ adapted to loosely receive the distal ends of the suspension beams 23. Such distal end~ include a threaded bore having a corresponding set ~crew 25 engaged therein. Tightening such set screw 25 against one of the ~ide walls orming such channel 24, whlch side wall i8 extended to overlap such bore, cause~ the displacement of the beam 23 within the channel 24 to a position in which it is frictionally engaged with the opposing side wall of the channel 24.
Loosening such set screw 25 affords the movement of the suspension beams 23 within the channels 24. The beams 23 can thus be displaced with respect to each other to ~ccommodate varying lengths (or widths) of the PCB.
One or more ~upport bracket~ 26 are adjustably mounted on each of the beams 23 and adapted to engage the edges of a PCB l9. The brackets 26 (See Fig. 4) include ~prings 30 which can be biased toward the beams 23 to frictionally engage the beams 23 but which can also be pivoted to a position spaced from the beams 23 to release the brackets 26 from frictional engagement with the beams 23 and afford the movement of the brackets 26 along the beams 23 in order to adjust for differing sizes and shapes of PCBs. The edge of the brackets 26 which is proximate to the PCB l9 has a groove 28 therein which is adapted to receive an edge of the PCB
l9. Similarly, the proximate end 31 of the spring 30 is al~o adapted to receive this edge of the PCB l9.
The bracket 26 is designed such that the ab~ence of a PCB l9 will allow tha spring 30 to pivot toward it~
spaced position thereby releasing the beam 23. The insertion of a PCB lg between the proximate end 31 of the spring 30 and the groove 28, however, biases the sprin~ 30 to engage the beam 23. The re~ilience of the 3pring 30 also securely captures the PCB 19 bet~een the grove 28 and the proximate end 31 of the sprin~ 30.
Since a typical PCB may have components mounted at varying position~ adjacent its outer edge it i8 po~sible with the present invention to adjust the brackets 26 along the beam 23 to a position which minimizes interference with these component~. The parallel ~ide members 22a and 22c also facilitate the tran~port of the carrier 20 by the conveyor units 12 and 13. For this purpose at least one surface 21 of the generally parallel side members 22a and 22c of the carrier 20 is substantially planar and has a coefficient of friction promoting the transport of the carrier 20 by the conveyor units 12 or 13. Furthermore the side members 22a and 22c include a projecting ridge 29, the operation of which, as well as the operation of the planar surface 21 will become apparent as a result of the description of the conveyor units ~supra). Each of the carriers 20 also contain structure to accurately locate the carrier~ 20 when they are positioned within any of the various stages 11 or 15 making up the system 10, as will be explained. In the embodiment illustrated the location holes 27 provide this locating structure.
As has already been discus~ed the conveyor units 12 and 13 provide for the transport of components, e.g. the~carriers 20 and the PCBs therein between the various ~tageq 11 and 15 of the test ~ystem 10. Although a variety of drive means can be utilized to transport the components, the illustrated embodiment (See Fig. 5~ employ~ driven rollers 32 which establish frictional contact with the extsrior planar surface on the members 22a or 22c of the carriers 20, or similar ~urface3 provided on other component~ to be transported. The rollers 32 are driven in a conventional manner by a dc motor 34. The driven rollers 32 are supported on gu~derails 91 on chassis 31 in a conventional manner and positioned adjacent both the oppo~ing ends of the conveyor units 12 or 13 to maintain control over a tran~ported carrier 20 as it pa~ses in either direction into or out of one conveyor unlt 12 or 13 to an adjacent conveyor unit 12 or 13, or into and out of a test stage 11 or a repai~ stage 15, as is applicable. The direction of travel of the rollers 32 is determined by the polarity of the dc motor 34. Guide rails 91, also supported upon the chassis 31 in a conventional manner and located adjacent opposing sides of the path of the carrier 20, contain channels 92 which are adapted to receive the projecting ridges 29 of the carriers 20 or similar pro~ectlng ridges on other transported components, thereby guiding as well as supporting the components.
In the illustrated embodiment of the drive means, (see Figure 5a) a belt 203 and pair of sprockets 204 or similar devices are use~ to transfer the rotation of the dc motor 34 fro~ a fir~t roller 32, mounted on the roto~ 33 of motor 34, to a second roller 32. Openings 205 in the guide rail 91 allow the rollers 32 to contact the exterior planar surfaces of members 22a or 22c of the carriers 20 when the pro~ecting ridges 29 of the carrier 20 are captive inside channels 92. As described hereinafter, the same drive scheme may be advantageously employed in buf~erinq stage 16 and automation interface 38.
Figures 5b~i), (ii), (iiij, and (iv) show a conveyor unit 12 in side, front, and top views and in perspective, respectively. In Figure 5b(iv), a carrier 20 i Q shown outside of the conveyor unit. This figure is included to illustrate how a carrier 20 is presented ~2~

to the conveyor unit. The carrier 20 i~ presented to the conveyor unit 12 by an adjacent conveyor unit 12 or 13, buffering stage 16 or automation interface 38 (not shown).
Fig~re 5c shows an enlarged section taken along lines 5c-5c of Figure 5. The frictional contact between the outer periphery of rollers 32 and the planar ~urfaces of members 22a or 22c of carrier 20 is clearly shown. As the rotor 33 of dc motor 34 rotates, a force is applied to the carrier 20 by rollers 32 causing it to move. As shown in Figure 5c, the carrier would move into or out of the page. The dc motor 34, rollers 32, belt 203 and sprockets 204 are supported on the guide rail 91 in conventional manner (not shown).
It should be noted that although a carrier is pictured, a fixture as~embly (Figure 9) or a cover assembly (Figure 11) could be pictured instead of the carrier and would be moved in identical fashion.
In order to change the direction of transport by other than 180 degrees, the conveyor unit 13 having component rotational capabilities, includes a stepper motor 95 and associated conventional bearing and gearing mechanisms or their equivalent (not shown), to rotate the chassis 31, supporting the roller~ 32, about a vertical axis "V". Figures 5d(i), (ii), (iii), (iv) and (v) show side, front, top, perspective and ro~ated top views, respectively, of the conveyor unit 13. In Figure 5d(v), the chassi~ 31 i~ shown rotated by some amount. The stepper motor 95 and associated bearing and gearing mechanisms or their equivalent (not shown) - are used to effect the pictured rotation~ The stepper motor is microproce 30r controlled to allow flexibility in the OrientatiGn of the chassi~ 31 and con~equently the path along wh~ ch component~ are tran~ported. The necessity for flexibility in the path for components was previougly de~cribed in conjunction with Fig. la.
The 3peed and polarity of the dc motor 34 and therefore the driven roller~ 32, are microprocessor controlled to afford controlled, bi-directional motion in the path along which a given component is transported. Conveyor unlt 12 and conveyor unit 13 are ~ub~tantially identical except that conveyor unit 12 exclude~ the stepper motor 95 and its a sociated mechanism. Each of the conveyor units 12 and 13 also includes appropriate sensors (see Fig. 14) to d~termine the presencs and location of a carrier 20 or other transported component therein. Similarly sensors also determine the relative positioning of the chassis 31 of the rotatable conveyor unit 13. The position of the chassis 31 of conveyor unit 13 can be sensed, for example, when the chassis is rotated to 0, 90, 180 and 270 degrees from a reference orientation. This can be accomplished witn mechanical, optical, magnetic, capacitive, or other type of conventional sensors. If the test system 10 requires a ? conveyor unit to stop or hold the transport of a carrier 20 or other transported component, stop solenoids are also provided at the entrance and exit ends of such conveyor units. When actuated the moveable element of such ~olenoids is interposed within the path oP the carrier~ 20 to prevent further motionO
Flgure 5e shows a portion of a conveyor unlt 12 or 13 with a stop solenod 206. The moveable element of the fiolenoid 206 is show~ removed from the path of motion of ~he fixture as~embly 47 so as to allow its motion, and in phantom the moveable element i8 shown interposed in the path of the fixture assembly 47 so a~ to prevent lts mo~ion. A ixture a~sembly 47 is pictured to illustrate that the fixture a~qsembly 47 is tran~ported ln a conveyor unit 12 or 13 in the same manner as a carrier ~See Fi~ure 5c~. The conveyor unit~ 12 and 13 are adapted to be utilized in modular for~. For example, one of the conveyor units 13 can contain a conveyor controller or microprocessor (See Figure 14) which can provide control for some predetermined quantity of slave conveyor units 12. These slave conveyor units 12 can ~imply be plugged into the master conveyor controller and such controller can be programmed with the location and identity of the additional conveyors 12 and 13 being utiliæed within the te~t system 10 and plugged therein, thereby - avoiding the need ~or redundant microprocessors within each oP the slave conveyor units 12. Each slave conveyor unit will, however, contain drivers, sensors, and stop~ to the extent required, such as have been described above.
The test system of the present invention also include~ an automation interface 38 (See Fig. 6) which interfaces the test stages 11 with the conveyor units 12 or 13. Similarly a ~uitably configured automa~ion interface can be provided to interface repair or other stage~ to the transport system 18 via a buffering stage 16 tmore fully described hereinafter). The automation interface 38 of the pre~ent invention i8 adapted to be utilized with existing testers such as are now commercially available, The automation interface 38 incorporates mechanisms to transport components by imparting a force to the side of the component via a roller ~as is done in the conveyor units 12 and 13) as well as mechanismq to change the elevation of components after they are captive in the automation - interface 38. These two functions are illustrated in Figure 6a which shows a test worX station. The figure shows a side view of a conveyor unit 12, buffering st~ge 16, and an automation lntexface 38 on a test ~tage lla, with movement of a fi~ture assembly 47 shown in phantom. The fixture a~sembly 47 is pictured in four positions: A, B, C and D. The four positions represent location~ the fixture a~sembly 47 would occupy at distinct intervals in time aq the work station is operated. The figure illustrates that an eRsentially horizontal motion of the component transports the component between the buffering stage 16 and conveyor unit 12, and between the conveyor unit 12 and the automation interface 38 and that an essentially vertical motion i8 used to elevate the component between the operating level of the conveyor unit 12 and the operating level of the te~t stage lla. The mechanisms to perform these functions will be discussed in detail hereinafter. The automation interface 38 contains a driven roller 39 similar to those utilized by the conveyors 12 and 13. The driven roller 39 is positioned to engage the exterior planar surfaces of parallel side member~ 22a and 22c of the carrier3 20 as the carriers 20 exit from the conveyor units 12 or 13.
In t~is manner the roller 39 can maintain control of the carriers 20 or other components when the roller~ 32 of the conveyor units 12 or 13 have lost effective control. This i8 illustrated in Figures 6b, 6c and 6d where a carrier 20 is shown at distinct intervals of time during its transportation into an automation interface 38. Shown are the carrier 20 with a PCs 19, a conveyor unit 12, and relevant portions of the automation interface 38 on top of a receiver 56 and test stage 11. Much of the mechanism of the automation interface 38 is not shown so that the function of the roller 39 can be clearly seen. In Figure 6b, a carrier 20 with a PCB 19 is shown entering the conveyor unit 12. The buffering stage 16, in the preferred embodiment of the invention, i8 adjacent to the conveyor unit 12 at the end oppo~ite the automation f9~

interface 38, a~ ~hown in Fig. 6a. At the interval of time illustrated by Figure 6b, the motion of the carrier 20 is being controlled by the conveyor unit 12, wherein the roller~ 32 are engaging the carrier 20. In Figure 6c, the carrier 20 is shown in such a position that the rollers 32 of the conveyor unit 12 no longer engage the carrier 20 and consequently have lost effective control. However, roller 39 of the automation interace i8 now engaging the side of carrier 20 and exercising control over carrier movement. At least one roller is always in contact with carrier 20, 80 that it i8 alway~ un~er control.
In Figure 6d the carrier 20 is shown fully supported in ide the automation i~terface 38. It is clear from Figure~ 6a through 6d that although co~ponents must be elevated between different operatin~ levels, the roller 39 can be fixed at the operating level of the conveyor unit 12 or 13. It should be noted that although a carrier 20 and PCB l9 are ~hown in Figures 6b through 6d, a ~ixture assembly 47 or cover assembly 62 could have been shown. In the preferred embodiment of the invention, the components are transported to the automation interface in 5uch a manner as to create the assembly shown in Figure lO. The driven roller 39 is driven by dc motor 96, which i9 also under microprocessor control. DC motor 96 i8 mounted upon a ~upporting column 97 by a bracket 98. See Fig. 7a.
The supporting column 97 is in turn rotatably mounted upon a bracXet assembly 99 which is a~fixed to the frame lO0 of the automation interface 38. The frame 100 is an essentially planar, rectangular surface c~rcum~cribing an es6entially rectangular opening, upon which the structure and m~chanisms of the auto~ation in~erace are mountedO Also mounted upon the bracket as~embly 99 is a solenoid lOl or similar device which can be actuated to extend an arm 102 to the position indicated by 102a (as shown by dashed lines in Fig. 7).
The arm 102 is pivotably connected to the supporting column 97. Thexefores the extension of the arm 102 will rotate the column 97 through the slotted extension arm 207. Such rotation of the column 97 will pivot t'ne dc motor 96 to a position 96a where the driven roller 39 passes through an opening 208 within the rails 44 and frictionally engages the carriers 2G. The rotation of column 97 and subsequent displacement of the roller 39 to a position labelled 39a is illustrated in the top view of Figure 7b. The purpose of this displacement will be discussed later. The opening 208 in the rails 44 is illustrated in Figures 6b through 6d. Similarly the retraction of the arm 102 will disengage the driven roller 39 from the carriers 20. The automation interface 38 further contains elevator means 40 (See Fig. 7c and 8) which i8 adapted to raise and/or lower the components with respect to the operating level of the conveyor unit~ 12 or 13. In the preferred embodiment the elevator means 40 comprise two spaced rails 44 which are substantially parallel to each other which elevate at the same rate such ~hat ~he ~wo ~paced rail3 44 remain essentially parallel, and that the plane defined by the two spaced rails 44 remains essentially horizontal throughout the travel of the rails 44. Each of the rails 44 contains a longitudinal channel 45 therein which iQ adapted to receive and ~: support the projecting ridge 29 extending along the side members 22a and 22c of the carriers 20. This is illu~trated in Fig~. 6b-6d. The rails 44 are themselves supported on air cylinders 43 or the liXe which afford the relatlve movement of the rails 44 from a ~o~ition supporttng the carrier~ 20 to a po~ition where the raiis 44 are spaced from the carriers 20.
~' This motion is illustrated in Figure 7c. The rails 44 are shown spaced from a fixture assembly 47, and in phantom in a position where they would be supporting the fixture assembly ~7. ~he necessity for this motion is apparent in that in order to deposit a component and/or elevate the rails 44 to some other operating level, they must be spaced from the side of the fixture assembly. The necessity to elevate the rails 44 to some other operating level arises from the need to stack components as shown in Figure 10. The air cylinders 43 are in turn supported by the shuttle member~ 42 of lead screw mechanisms 41, and the lead screw mechanisms 41 are driven by a stepper motor 36 which is microprocessor controlled. A drive belt 35 in combination with various pulley~ are driven by motor 36 ,~ and in turn drive lead screw mechanisms 41 located at each of the opposing corners of the rails 44. Rotation of the multiple lead screw mechanisms 41 by the motor 36 will raise or lower the rails 44 in a controllable manner. This is shown ~chematically in Fig. 7d. The rails 44 can therefore be positioned at the operating level of the conveyors 12 and 13, and the air cylinders ~3 can be actuated to move the rails 44 to the position - at which they can support the carriers 20. In addition solenoid 101 can be actuated to bring the driven roller 39 into frictional en~agement with the carrier 20 through the opening 208 in the rail 44, ~ince the roller 39 and rails 44 are at the operating level of the adjacent conveyor unit 12 or 13. The purpose of 30 the solenoid lOl and pivotably mounted brarket S7 shown in Figures 7 and 7a is now clearly visible. Since the rails 44 are elevated between the operating level of the adjacent conveyor unit 12 or 13 and a level which is below that level ~as seen ln Figure 7c) the roller 39 must be removed from contacting the side of the component which is supported inside the rails 44 in order to raise or lower that component. A carrier 20 can then be transported by the driven rollers 32 of the conveyor units 12 or 13 and/or the driven rollers 39 of the automation interface 38 into the channels 45 of the rails 44 as seen in Figures 6b~6d. Conventional ~echanical stops or solenoids (See Fig. 14) can be utilized to ensure the carrier 20 is fully transported and accurately positioned within the rails 44 aa seen in Fig. 6do The solenoid 101 can then retract the driven roller 39 and the lead screw mechanisms 41 can be driven to raise or lower the carrier 20 from the operatlng level of the conveyor unit 12 or 13 to the operating level of the test stage 11. The automation interface also includes appropriate sensors (See Fig.
14) similar to those described with regard to the - conveyor units to determine the presence of a carrier 20 or other transported component therein. Similarly, sensors are also available to determine the positioning of the elevator means 40 and the rails 44.
As has already been stated, PCB testers traditionally use fixturing assemblies to achieve electrical contact with the PCBs under test.
Traditionally, these fixture assemblie~ are manually loaded onto the testerq and the probes therein are electrically connected to the various stimulus and measurement means included within the testers. The PCBs which are to be tested are then individually and manually placed llpon such a fixture assembly and accurate~y located with respect to the probes. A
detailed discussion of a fixturing system such as is de~cribed above i8 ~et forth in U.S. Patent 4,352,061 ~hereinafter "061 Patent"). Such a fix-turing assembly as is taught by the 061 Patent can be adapted !

r^--~ . .

to permit its transport by the conveyor units 12 and 13, buffering stages 16 and automation interface 38.
The fixture assembly is best illustrated in Figures 9, 9a and 10. In Figure 9 the fixture assembly 47 i5 shown in perspective with a portion cut away to expose the interior structure of the assembly. A complete picture of the fixtur~ assembly 47 i9 shown in the bottom, side, front and top views, respectively, of Figures 9a(i), (ii), (iii) and (iv). In Figure 10, a partial section is shown of a fixture assembly 47, a carrier 20 and a cover assembly 62 aq they would be configured just prior to invoking a test. The stacked arrangement of component3 is shown restiny on a receiver 56, which would be supported by the test station 11. It should be noted that each of the three components (fixture assembly 47, carrier 20 an~ cover as3embly 62) would be transported to the automation interface 38 by the oonveyor units 12 and 13 and buffering ~tages 16, as required, and that each would be lowered to an operating level by the elevator means of the automation interface so as to produce a desired stac~ed arrangement of components, e.g. a~ shown in Fi~ure 10. The fixture assemblies 47, adapted according to the present invention, include a frame 48 having interconnected members 48a-48d circumscribing and thereby defining an interior are~ sufficiently large to accommodate the larger PCBs which are intended to be tested. The frame 48 has at least 2 parallel side members 48a and 48c adapted to afford the transport of the fixture assembly 47 by the conveyor units 12 and 13, buffering stage 16 and automation interface 38. For this purpose at least one surface on each of the parallel side members 48a and 48c of the ~ixture assembly ~7 i~ substantially planar and ha~ a coefficient of friction which will promote the transport of the fixture assembly 47 by the conveyor units 12 or 13, buffering stage 16 and automation interface 3B. slde member3 48a and 48c also include a projecting ridge 58 which will be received by the aforementioned channels 45 of the automation interface and 92 of the conveyor units. In addition, location holes 52 similar to those de~cribed within the carrier 20 are also added to facilitate locating the fixture assembly 47 with respect to the automation interface 38. The means by which the fixture a~sembly 47 is located with respect to the automation interface 38 is illustrated in Figure 9b. In the figure, distances a and b show that the location of the automation - interface 38 is referenced to receiver 56 via the two column~ 60. The two col~mns 60 also reference the fixture assembly 47, carrier assembly 20 and cover assembly 62 with respect to the receiver 56. Hence, the fixture assembly 47 is referenced to the automation interface 38. Supported within the frame 48 is a non-conductive plate 49. Typically this plate 49 is manufactured from materials having characteristics resulting in a plate 49 which is both lightweight and yet capable of withstanding substantial forces without signifi~ant deformation. One such material is manufactured and sold by General Electric Company under the de~ignation G-10 epoxy glass cloth, although comparable glass, paper vr cloth laminates are also useable~ A predetermined array of electrical probes 51 are supported within and pass through thi~ plate 49.
These probes 51 are po~itioned in a pre-arranged pa~tern to correspond with selected nodes on the PCB 19 which i~ to be tested. ~s has already been described, this pattern will typically be uniqu-e for each type or model of PCB 1~ whlch i~ to be tested. The array o~
; 35 probe~ 51 is electrically connected to an array o po~ts 53 which are supported within a contact panel plate 5~. Either individual wiring or a personality or universal matrix platen concept such as is described in the 061 Patent could be utilized to provide this electrical connection. The contact panel plate 54 is also constructed from materials similar to those de~cribed with respect to plate 49, and is similarly affixed to the frame 48. Spacers 55 between plate 54 and plate 49 ensure that plates 54 and 49 remain substantially parallel and rigid. A view of a fixture assembly 47 is shown in Figure 9c. All of the componen~s of the assembly are shown except the means of electrical connection between the array of probes 51 and the array of posts 53. The test stages ll contain a receiver 56 also having an array of probes 57 which correspond to the array of posts 53. The probes 57 of the receiver 56 are electrically connected to the various stimulus and measurement mean3 included within the test stages ll. Actuating means (not shown) such as the vacuum described in the 061 Patent are utilized to draw the posts 53 of the contact panel 54 toward the probes 57 of the receiver 56 thereby establishing electrical connection between the probes 57 of the 'receiver 56 and the posts 53 o~ the fixture assembly : 25 47. Alternative actuating means (not shown) such as electronic motors, hydraulic cylinders, lever mechanisms, camming mechanism~, etc. can also be utilized to establi~h this electrical connection.
In a manner already described with regard to the carriers 20, the fixture assemblies 47 can be transp,orted by the conveyor units 12 and 13 to a desired automation interface 38 of the required stage ll.' Slmilarly the elevator means 40 o~ the automation in~erface 38 can be u~ed ~o ral~e or lower tha ~ixture as~embly 47 from the operating level of the conveyor units 12 and 13 to a level where the contact panel plate 54 can be brought into preliminary engagement with the receiver 56. Simultaneously the air cylinders 43 supporting the rails 44 can be actuated to cause the rails 44 to release the projecting side members 58 of the fixture a~semblie3 47. The exact po~itioning of the fixture assemblies 47 with respect to the stages 11 is achieved by including guide columns 60 within the test stages lla and llb~ These guide columns 60 cooperate with the location of the location holes 52 within the fixture assembly 47 to accurately position the fixture assemblies 47. See Fig. 9b. Pref~rably either the column~ 60 or the holes 52 are tapered to ensure engagement.
- 15 A PCB 19, positioned within a carrier 20, can then be transported to the test stage in a manner already described and po~itioned upon the fixture a~sembly 47. See Figures 9b and 10. Once the PCB is loaded upon a fixture assembly 47, the test systems' actuating means, e.g. a vacuum, is utilized to draw the PCB 19 and the fixture assembly 47 toward the receiver 56 and thereby compress the spring loaded probes of the fixture assembly 47 to ensure electrical connection between the fixture assembly 47 and the conductive paths of the PCB 19. To ensure that a vacuum can be drawn between the PCB 19 and the fixture assembly 47 the preferred embodiment of the present invention utilizes a cover assembly 62 (See Fig. 11) which includes a frame 64 having interconnected member~
64a-64d circumscribing and thereby defining an interior area sufficiently large to accommodate the PCBs 19 which are intended to be tested. At 1 ast two of the interconnected members 64~ and 64c have at lea~t one surface whlch i8 ~ub~antially planar and which ha~ a coefficient of friction promoting the tran~port of the .

9LR~O~

cover member 62 by the conveyor units 12 and 13, buffering stage 16 and automation interface 38. Side member~ 64a and 64c also include a projecting ridge 63.
Fr~me members 64b and 64d contain location holes 61 analogou~ to those o the carrier and fixture assembly.
Suspended across within the frame 63 is a sealing diaphragm 65 which is constructed of a resilient mater~al Ruch as that utilized in the construction of ~urgical gloves. This diaphragm 65 is supported within the frame 64 in a manner restricting passage of the atmosphere between the frame 64 and the diaphragm 65.
The diaphragm 65 is adequately elastomeric such that it is capable of envelopln~ the Pcs 19 in a manner similar to ~hrink wrap parkaging, without damaging the components on the PCB or without itself becoming damaged. The use of such ~over assembly 62 affords the elimination of custom edge seals and ~asket~ which are required by conventional fixtures. In a manner already discus~ed, the cover assembly 62 can be transported by the conveyor units 12 and 13, buffering 3tage 16 and automation interface 38 to an appropriate stage lla or llb.
Since the cover assemblies 62 are not PC~
specific and will function with practically all PCBs 19 and ~ixture assemblie~ 47, the automation interface 38 of the present invention is adap~ed to include separate lifting means (See Figure~ 6 and llb) for the cover a~emblies 62~ These lifting means include a lifting carriage 85 having interconnected members forming a substantially U-~haped configuration. Two legs of the carriage 85 are sub3tantially parallel and have solenoid3 87 (or comparable deviceq) mounted thereon which are adapted to engage cover suppor~ holes-88 within the frame 64 of the cover a~embly 62. The lifting carriage 85 i~ ~upported on an air cylinder 89 ~'~7~

and slide mechanism 90. Once a cover assembly 62 has been transported to a given automation interface 3B, the carriage 85 can be lowered over the cover assembly 62, and the solenoids 87 can be actuated to engage the support holes 88, thereby locking the cover assembly 62 to the carriaye 85. The air cylinder 89 can then be actuated to lift the cover assembly 62 within the slide 90 above the operating level of the conveyor unit, thereby clearing the path for the tran~port of additional carriers 20 and fixture assemblies 47 without requiring the unloading and transport of a cover assembly 62 for every chanye in carriers 20 or fixture assemblies 47O Obviating the need to repetitively transport a cover assembly 62 between an automation interface 38 and a buffering stage 16 further reduces the time taken by the system 10 of the present invention to test and/or repair PCBs. To facilitate the vacuum seal, either the frame 64 of the cover asseJnbly 62 or the frame 22 of the carrier 20 - 20 contains appropriate gasket means to create a seal between the carrier 20 and the cover assembly 62 when the two are placed adjacent to one another. In the preferred embodiment the diaphragm 65 i8 extended over the frame 64 to provide such gasket means. Similarly either the frame 22 of the carrier 20 or the frame 48 of the fixture assembly 47 will also contain appropriate gasket means 67 to ~eal the space there between when the carrier 20 (and PCB 19) i8 placed upon the ixture assembly 47. Likewise gasket means 68 are interposed between the fixture assembly 47 and the contacting surface of the te~t stage 11. It is apparent to one s~illed in the art that such gasket means in cooperation with the cover as~embly 62 will facilitate a ~ealed chamber which can be evacuated ln order to draw the diaphrag~ 65 downward in re~ponse to the greater atmospheric pressure above the diaphragm 65 resulting from the vacuum, and thereby force the PCB 19 and the fixture assembly 47 toward the ~eceiver 56.
Suitable sensors (not shown) are included with the present invention to ensure the presence of an adequate vacuu~, which i~ also an indication that the fixture assembly 47 and the PCB have been drawn into contact.
An example is now provided showing how the automation interface 38 operates with fixture assemblies 47, carriers 20, cover assemblies 62, conveyor units 12 and buffering stages 16 in Figure lla. This figure illustrates the sequence of events for te~ting two diPferent types of PCBs. These two types are called type A and type B. In the example, 2 PCBs of type A and 1 PC8 of type B are tested. The fixture assemblie~ associated with each of these PCB
types are called fixture A and fixture B respectively.
It is assumed that all of the necessary components for the two tests are present in the buffering stage 16 adjacent to the conveyor unit 12 which is itself adjacent to the test 3tage lla and llb. (See Figures 1 and 6a) Discussion is provided hereinafter as to how and when the components are delivered t~ the appropriate buffering stage 16 and how the buffering stage 16 facilitates the transport of components. Also discussed later is the scheme used to decide which PCB
type (A or B) is to be given the highest priority in term~ of utilization of the test stage 11. The example illustrates only the phyRical operations and motions that take place in order to test the threa ~pecific PCBs in this discussion.
Gen~rally, as shown in Fig. lla, components required to perform the desired test are transported to, loaded into and aligned in the automation interface 38, the test is invo~ed, and then components no longer 3~

needed are unloaded and transported from the automation interface. In the illustrated example, the cover assembly 62 is employed to test all three boards and fixture A used in the test of both Type A PCBs. More particularly, as depicted in Fig. lla, test fixture A
is fixst transported to automation interface 38, aligned and engaged with receiver 56. Cover assembly 6~ i8 ~ext transported to and loaded into the automation interface. The irst Type A PCB i~ then transported to the automation interface and aligned with fixture A. The test i~ then invoked followed by unloading and transport of the first PCB Type A from the automation interface. The second PCB Type A can ~hen be transpor~ed to the automation interface, aligned with fixture ~, tested, unloaded, and transported from the automation interface. To test the Type B PCB, fixture A is unloaded and transported out of the automation interface and fixture B then transported in and aligned and enga~ed with receiver 56, The Type B PCB can then be transported to the automation interface, aligned with fixture B, tested, and finally unloaded and transported out of the automation interface.
In Figure lla, the procedure labelled (i) is expanded in Figure lla(i) to show the low-level operationR needed to tran~port a component from the buffering stage 16 to the automation interface 38.
Since this sequence of operations is repeated for different components, it i8 generalized for any component. Similarly, the low-level operations needed to load a fixture assembly onto the test ~tage, load a cover assembly into the automation interface, load a PCB onto a fixture assembly, invo~e a test of a PCB, unload a PCB from a fixture assembly, transport component~ from the automation interface to the o~

buffering stage 16, and unload a fixture from the test stage are labelled (ii) through (viii), and are detailed in Figure~ lla(ii) through lla(viii), respectively.
In Figure lla(i), the following operation~
taXe place to transfer a component from the buffering stage to the automation interface. The number de~ignations corre~pond to the blocXs in the Figure.
(1) The rails 44 of the automation interface 38 are elevated to the operating level of the conveyor unit 120 (See Figure 7c) The number of motor steps required to elevate the rail~ to this level is known by the workstation controller.
(2) The rails are extended so that the slots 45 in the rail~ can support the projecting ridges 58 of the fixture assembly 47, the projecting ridges 29 of the carrier 20, or the projecting ridges 63 of the cover assembly 62.
(3) The arm 98 of the as~embly in figures 7 and 7a iq extended by actuating the solenoid 101 so that the roller 39 will contact the side of a component when lt is captive in and supported by the rails 44.
The side~ of components include: sides 48a or 48c of the fixture assembly 47, sides 22a or 22c of the carrler 20, and side~ 64a or 64c of the cover a~sembly 62.
~4) The dc motor 96 attached to arm 98 is energized in a controlled fashion so as to cause the component to move into the automation interface 38.
(5) The dc motor 34 in the conveyor unit 12 iQ energized in a controlled fa~hion so as to cause the ~omponent to move ~oward the automation in~erface 38.
Whan the side o~ the component contact~ the roller 32 in the conveyor unit 12, it i8 transported through the conveyor unit 12. ~See Figure 5e~ (The buffering stage ~ -34-16 causes the component to contact the rollers 32, but th~ exact method is discussed later.~ When the component exits the conveyor unit 12, one of its sides contacts the roller 39, and it is driven into the automation interface. (See Figures 6b, 6c and 6d).
(6) The dc motor 34 is de-energized.
(7) The dc motor 96 is de-energized.
(8) The arm 98 is retracted by actuating the solenoid lOl, so that the roller 39 is not in contact with the side of the component.
In Figure lla(ii), the following opera~ions take place to load a fixture onto a test stage:
(9) The rails 44, supporting the fixture assembly, are lowered by the stepper motor 36, via a system of belts, (See Figure 7d) until the contact panel plate 54 is brought into preliminary engagement with the receiver, and the fixture assembly is supported by the receiver. The number of motor steps required to vary the elevation of the fixture assembly in this manner is known by the worXstation controller.
(10) The rails 44 are retracted so that the fixture is no longer supported by the rails (See Figure 7c).
(11) The means to establish electrical connection between the probe~ 57 of the receiver 56 and the posts 53 of the fixture assembly 47 i5 now activated. The fixture i5 now ready to be used for testing.
In Figure lla(iii) the following operations take place to load a cov~r assembly into the automation interface:
(12) The rails 44, supporting the vacuum cover assembly 62~ are now lowered until the vacuum cover assembly 62 i3 supported by the fixture as~embly 47. The number of stepper motor steps required ~o effect this motion i8 known by the workstation controller.
(13) The rails 44 are retracted. (See Figure 7c) (14) The lifting carriage 85 is lowered until it contacts the cover assembly 62.
(15) The solenoids 87 are extended, engaging the support holes 88.
(16~ The lifting carriage 85 is raised, carrying the cover assembly 62, locked to it by the solenoids 87. Figure llb shows the cover assembly 62 loc~ed to and raised by the lifting carriage 85.
In Figure lla(iv), the following operations taXe place to load a PCB onto a fixtur~ a~sembly:
(17) The rails 44, supporting a carrier 20 and PCB 19, are lowered until the carrier 20 is resting on the fixture assembly 47. The number o stepper motor steps to do this i~ known by the workstation controller.
(18) The rails 44 are retracted. (See Figure 7c) In Figure lla(v), the following operations take place to invoke the testing of a PCB:
(19) The lifting carriage 85, to which the cover assembly 62 is attached, is lowered until the cover assembly rests on the carrier 20.
(20) The chamber beneath the vacuum cover diaphragm 65 is evacuated establishin~ electrical contact between the probes 57 of the fixture assembly and the nodes of the PCB.
- (21) The test is executed. This f~nction is carried out by commercially available equipment.
(22~ The chamber beneath the vacuum cover diaphragm 65 is allowed to return to atmospheric pressure at the completion of the test.

~-36-(23) The lifting carriage 85, supporting the cover a~sembly 62 i~ raised.
In Figure lla(vi), the following operations take place to unload a PCB from a fixture:
(24) The rails 44 are extended. (See Figure 7c) (25) The rails 44, supporting a component, are elevated to the operating level of the conveyor unit 12. The number of motor ~teps required to effect thi~ motion is known by the worXstation controller.
In Figure lla(vii~, the following operations take place to transport components from the automation interface 38 to the buffering stage 16. This sequence i~ similar to that illustrated in Figure lla(i) except the order is reversed.
(26) The arm 98 is extended by actuating the solenoid 101, making contact between the side of the component and the roller 39.
~ 27) The dc motor 34 in the conveyor unit 12 is energized in a controlled manner so as to cause components to move toward the buffering stage 16.
(28) The dc motor 96 in the automation interface 38 is energized in a controlled manner so as to cause components to move toward the buffering stage 16.
Steps (27) and (28) cause the component to move toward the buffering stage 16. The buffering stage 16 cooperates with the conveyor unit 12 so as to move the component completely off the conveyor unit 12.
This cooperation is discussed later.
(29~ rrhe dc motor 95 is de-energized.
(30) The dc motor 34 is de~energized.
The second PCB type A is then loaded onto the type A ixture in the automation interface, tested, and unloaded and transported from the automation interface.

In the example, PCB type~ A are no longer going to be te~ted. Con~equently, fixture A mu~t be exchanged for fixture B on the test ~tage. It ~hould be noted that in this example, the same cover as~embly 62 i5 used with both PCB types A and B. The carriage lift a~sembly 85 can be u~ed to raise the cover assembly 62 above the operating level of the adjacent conveyor unit 12, making it possible to exchange ixtures without removing the cover a~sembly 62 from the automation interface 38. This decrea~e3 the time required to set up the test stage for a different PCB type, and makes the operation of the system more efficient.
In Fig. lla(viii) the following operations ta~e place to unload a ixture a~sembly from a test ~tage ~o that it can be tran~ported out of the automation interface:
(31) The rails 44 are retracted. (See Figure 7c) - (32) The rails 44 are lowered to a height which will facilitate the engagement of the rails with the pro~e~ting ridge 58 of the fixture assembly 47.
(See Figure 7c) This height, and the number of stepper motor ~teps which correspond to it, are known by the worXstation controller.
(33) The means to establish electrical contact between the probe~ 57 of the receiver 56 and the po3t8 53 of the contact panel 54 are deactivated.
(34) The rail~ 44 are extended.
(35) The rails 44, ~upporting fixture A, are elevated to the operating level of the conveyor unit 12. The number of motor ~teps required to effect this motion i~ known by the worksta~ion controller.
The step ~hown in Figures lla(i), (ii) and (~v) - (viii) are then repeated for the type B PCB.

It should be noted that the system lO of the present invention can also be utilized with double-sided ~CBY, i.e. PCBs which have nodes on both opposing surface~ which must be acces~ed in order to S te~t the PCB. In this event a second fixture assembly 47' is transported and positioned adjacent the PC~ to be tested, i.e. the PCB is ~andwiched between the two fixture assemblies. See Fig. llc. In the preferred embodiment the array of probes 51' of the upper fixture assembly 47' are electrically connected to an array of posts 53'. Such posts 53' of this upper fixture assembly are, however, supported in plate 54' exterior to that portion of its surface area which is directly opposi~e the PCB when the PCB is positioned adjacent thereto. In addition the lower fixture assembly 47 contains an array of probes 51 which are adapted to contact the post~ 53' of the upper fixture assembly when the vacuum or other actuating means draws the ~arious components together.
It should be noted that circuit means other than the fixture assemblies 47 thus far described can be utilized as part of the present invention to achieve electrical contact with the selected nodes of the PCB
to be tested.
A~ has previously been discussed, the present invention include~ one or more buffering stages 16.
The buffering stages serve as an interface which connect the various te~t, repair, input/output, 3torage and other stations that make up a system to the common transport system 18. From the example illustrated in Figure lla, one can see that the buffering stages can be used to store (or "buffer"~ components that are used in the test station. Similarly, in the preferred embodiment, component~ can be buffered at each station.
For this reason e~ery test, repair etc. station ~7~

includea and is joined to the transport sy~tem 18 through a buffering stage 16. From Figure la, it i8 apparent that components are transported into and out o buffering stage~ 16. It is also apparent that only one component can be transported in a conveyor unit 12 or 13 at a time, and consequently the buffering stages 16 provide a location where components can be buffered until the conveyor units are free. (The methodology or allocating the conveyor units i~ discussed later.) Since the transport system 18 transports components at an elevation which can be diferent from the elevation in the workstations, the buffering ~tages provide a means to vary the elevation of components between the two levels. Such buffering stages 16 (See Figs. 12 &
13) include a large receptacle 70 having internal wall portion~ 71 forming a plurality of slots or cells adapted to receive and support the carriers 20, the fixture assemblies 47 and the cover assemblies 62, in a manner permitting them to move interchangeably in or out of the receptacle 70. The receptacle 70 i~
supported within a frame 72 so as to be moveable in a generally upward or downward direction with respect to the operating level of the conveyor ~nits 12 or 13.
Typically this movement is achieved by driven pinion gears 73 rotatably mounted on opposing sides (only one iQ shown) of the receptacle 70. The pinion ~ears 73 are driYen by a conventional stepper motor (not shown).
Corresponding ~lotted racks 75 which are adapted to engage such pinion gears 73 are fixed to the two adjacent sides (only one i~ qhown) of the frame 72. In this manner the rotation of the pinion gears 73 hy the ~tepper motor will move the receptacle 70 in either an upward or downward direction, to afford the positioning of the receptacl~ 70 with any preselected one of its cells at the operating level of ~he conveyor units 12 or 13. The operation of a bufferinq stage 16 as it relates to adjacent conveyor units 12 is illustrated in figures 12a through 12c. In these figures, the frame structure of the buffering stage is not 6hown so that the functionality can be better illustrated. The dc motors, stepper motor, rack and pinion gear of the buffering stage 16 and the drive mean~ of the conveyor units (dc motor 34, belt 203, sprocke~s 204 and rollers 32) are also not shown.
In Figure 12a, a carrier 20 is shown driven partly into a conveyor unit 12 labelled "left". Fi~ure 12b shows the carrier partially driven into the receptacle 70, where the projecting ridges 29 of the carrier 20 are supported by the Rlots in the internal wall portions 71. The means by which the carrier is driven into the receptacle 70 is discussed later. In Figure 12CI the receptacle 70 is shown elevated so that the carrier is at the operating level of the conveyor unit labeled "right", and the carrier 20 is shown as it is being transported from the buffer stage 16 to this conveyor unit. To facilitate the accurate and aligned movement of the receptacle 70 it is mounted with respect to the frame 72 by a plurality of bushings 77 slideably supported on columns 78 which are in turn affixed to frame 72. The buffering stage~ 16 also - contain two drive wheels 76 driven by a dc motor in the ~ame manner as has previou~ly been described with respect to the conveyor units. These drive wheels 76 are pivotally mounted on frame 72 at the operating level of the conveyor uni~s 12 and 13. To provide clearance for the receptable 70, ~o that it can be driven up and down loaded with component~ withln the frame 72, by the stepper motor via the rack and pinion mechanism, a solenoid 79 or comparable device is used to pivot the drive wheels 76 in a manner similar to that described with regard to the automation interface 38, from a position at which they are in frictional contact with the parallel side members of either the carrier 20, the cover as~embly 62, or the fixture assembly 47 which i~ within the cell of the receptacle 70 po3itioned at the operating level of the conveyor units 12 and 13, to a second position which is spaced from the receptacle 70. It ~hould be noted that the receptacle 70 contains cut out portions within the wall portions 71 to permit the drive wheels 76 to intrude within the interior of the receptacle 70 so a~ to contact the variou~ carriers 20, fixture as~emblies 47 and cover assemblie~ 62 located therein. The ~tepper motor of the buffering stage is controlled by the wor~station controller to facilitate the exact vertical positioning of the receptacle. The timely pivotal action effected by solenoids 79 and controlled rotation of the drive wheels 76 are al~o controlled by the workstation controller. Appropriate sensors of the types ~lready deqcribed are included (See Fig. 14) to verify the presence of a carrier 20 or other tran~ported article within the cell~ of the receptacles 70. Similarly sen~ors also verify the relative positioning of the receptacles 70 and the drive wheels 76.
It should be noted that buffering stage~q 16 are also designed to be modular, and a variety of configurations are therefore po~sible. For example, multiple slave buffering stages 16 can be stacked adjacent one another for mass storage of cover a~semblies 62, fixture assemblies 47, and carriers 20.
In this configuration it i~ useful to have separate drive wheel~ 76 and a corresponding dc motor on the side of the buffering ~tage 16 proximate to a conveyor un~t, and separate drive wheels 76 and a corresponding dc motor on the side of the buffering stage 16 proximate to adjacent buffering stage 16. This afford3 more accurate control over the carriers 20, fixture assemblies 47, and cover assemblies 62 as they are being transported between adjacent buffering stages 16.
The drive wheels 76 in buffering stages of such a storage station 5 are preferably all at the same vertical height. It is also possible with this configuration to utilize a master buffering stage controller or microproces~or connected to multiple ~lave buffering stages (5ee Fig. 14). This concept has already been discussed with respect to the conveyor units 12 and 13. The ~lave buffering stages while containing similar motors, sensors, and stops, do not lS require separate microproce~sors. Alternatively, or in addition, buffering stages 16 can be utilized as interface devices to individual repair or test stages.
Thi~ configuration can shorten overall testing and repair time since, as an example, a batch of carriers 20 containing PC8s 19 requiring the same fixture assembly 47 can be ~tored proximate a given test stage and immediately ~equenced through that test stage as it becomes available. In this configuration it i~ useful to have separate drive wheels 76 and a corresponding dc motor operating at different vertical level3 within the buffering ~tage 16. The conveyor unit3 12 and buffering stage 16 shown in Figure 13a illustrate how - the drive wheels 76 in the buffering stage 16 are positioned at the operating level of the adjacent conveyor unit~ 12, and that a conveyor unit which is part of a workstation (labelled right~ can be at a different level from one which is part of the transport system 18 (labelled left). In this figure, the two dc motors 209 are shown at the operating levels of the two conveyor units. These motor~ are each mounted to a ~-q~

respective bracket 98' which is mounted upon a ~upporting column 97' (See Figure 13b). The 3upporting column 97' is in turn mounted to the frame 72. The other drive wheels 76, similarly mounted to supporting column~ 97'', are mounted to the opposite side of the buffering stage 16. Figure 13b further illus~rates the pivotal movement imparting mechanisms which are identical to that of the automation interace. Figure 13c shows view B~B from Figure 13. In this figure, the four drive wheels 76 are shown. It should be remem~ered that typically the drive wheels near the bottom of the figure are positioned at a different level fro~ those near the top of the figure. In Figure 13c, one ~et of drive wheels 76 is shown in dashed line~ at the extended positions 76a wherein the wheels are contacting the parallel side members of the carrier 20. From this figure, it is apparent that by energizing the dc motor 209 when the associated drive wheel~ 76 are contacting the side of the carrier, the carrier will be moved. In Figure 13c, this motion will be toward the top or bottom of the page. For example components could enter and exit the buffering stage 16 from or to an adjacent conveyor unit at the conveyor operating level, while at the same time entering from or exiting to an adjacent te~t stage at the operating level of such test ~tage.
When the test system 10 according to the present invention is initially installed the User will be required to identify certain information about the system configuration and the PCBs tha~ are to be tested and/or repaired. This information includes the type of test stages llt repair stages 15, conveyor units 12, conveyor units 13, and buffering stage3 16 ~hereinafter referred to generically a~ "modules") which will maXe up the system 10, as well as the relative location of IZ ~4~

each of these modules within the ~ystem 10. It is possible with this system 10 to create a large variety of dlfferent physlcal configurations using the standard modules as described. Several example configurations S are ~hown in Fig. 13d. It also seems very likely that an installed system may be modified from time to time for purposeR such as the addition of new modules or the creation of additional or alternate paths to high volume modules, etc. In a traditional automation ~ystem these changes would require the user to experience a relatively long period of production shut-down in order to make several mechanical and/or - software revisions to be able to use the newly configured system. An important benefit of.the present inventi.on is that such changes are possible with a minimum of down-time and virtually no software changes.
Since this ~ystem i~ comprised of a relatively small set of modules whose functions are known, any configuration of the system can be reduced to a list of modules, their types, and the necessary relationship between them with regard to control and orientation.
Rather than force the user to determine the desired layout by paper and pencil methods and later input a fairly large amount of data, the.present invention provides a convenient method for arranging the modules of a system and at the same time automatically capture the required data to operate the system 10. During the initial start-up the master control unit 17 presents the user with a grid pattern on a graphical display device, and a menu upon which the various potential modules are repreqented schematically, e.g. by icon~.
These icon~ may be selected by the user and placed on the grid. In .this manner a co~figuration may be built up ~n an interactiYe way which represents the deqired configuration of the system. The user may remove and ,~2r~

replace modules, select new module type3, and reconfigure the module orientations until the configuration appear~ as desired. The configuration may be an entirely new layout, or an exi~ting configuration may be recalled and "edited" to achieve the desired result. A configuration may be "saved" at the request of the user ~o be used either a~ the default or controlling configuration file for the new system or as reference when con~idering more than one po~ible configuration for the 3ystem. Once the desired physical layout has been determined by the user a verification routine may be invoked. The verification routine applies a set of design rules regarding module placements and orientation to be certain that the proposed configuration is operable.
An example would be that a corner of the transport system must contain a conveyor unit 13 with rotation capability. Should an error be located the user i3 informed of the conflict and the input phase is reinstated. After passing the rule check the user i~
then prompted for the additional data required to define the configuration which i3 not ascertainable from the graphic repre~entation, such a~ controller ID
numbers and the desired interconnections of slave~
units to master controllers. Once this in~ormation is entered a user may re~uest the 3ystem 10 to print out a configuration listing. ~his listing describes the configuration, for example, a list of the modules u~ed by type, a connection list for cables (including power, logic, air, etc.) by module, e~c. Thi3 listing aid~
the user in the actual physical connection of a new configuration. By u ing this interactive method new configuration3 may be efficiently created by the u3er, and the resulting data file will automatically contain the required information to allow the system 10 to be ` ~279~8 -4~-controlled without requiring any additional input or changes to the control system software.
Once the configuration is established a software routine within the operating system recognizes the icons and provide~ each module with a unique identity code (typically based upon the controller ID).
The routine then identifies the interconnections between the modules and const~ucts all the possibLe paths between the various modules indica~ed and the re~uired operation of the various modules to facilitate these paths. The operating system utilizes this information to con~truct a table which correlates all the ways to get from the various starting modules (e.g.
buffering stage 16) at which a component may be located to the various destination modules (e.g. test stage 11) to which a component will be transported. Such technique~ as a~e required to formulate this information are commonly available as evidenced by a text entitled, "Compute~ Algorithms", written by Sara Baase, and published by Addison Wesley, 1978. A file, here-inafter referred to as the system configuration file, is created containing this configuration and path information.
This file is stored either in the memory associated with the master control unit 17 or a host computer interfaced with the master control unit 17, or within a disk file which can be provided as an input to the master control uni-t 17 when the system 10 is to be used. This modular approach of the present invention and the ease in which configuration changes can be programmed or specified, affords the user flexibility to easily adapt the configuration of the system 10, to tailor the system 10 to the particular user require-ments.

Prior to testing and/or repairing PCBs with the system 10, the user i8 also required to input information pertaining to the various types of PcsS
which are to be tested, and the testing sequenCe which will be required to process each PCB type. Each step in the ~equence i~ performed by some test or repair stage which provide~, a~ a re~ult, a coded indicator (interpreted by the master control unit 17) to determine which of po ~ible alternate steps of the sequence i~ to follow. For example, a specific type of PCB might need to be tested first with a functional tester. If it fails ~hese tests, (as indicated by the result supplied by the tester) the PC8 may secondarily be te~ted on an in-circuit tes~er. Alternatively, the results may indicate that the PCB need~ to be transported to a repair station instead of the in-circuit tester. After repairs and/or adjustments are made to the PCB it may be routed to the functional tester to repeat the tests which it previously failed.
Simila~ly, certain test results may require the performance of certain tasks such as manually probing various nodes of the PCB. The PCB would therefore have to be routed to a module affording such tasXs. Thus a unique proceq~ 3equence is determined for each type or batch of PCB which is to be tested. This information i8 stored as a deci ion tree or similar device, where the process step~ form the node of the tree and the coded indicators determine the branches between nodes.
The sequence information and a base priori~y code (associated with the PCB type and used by the system in processing PCBs of this type~ are stored ln a file, hereinafter referred to as the process ~equence file, which can be provided as input to the master control uni~ 17. The deci~ion tree includes all the various sequential event3 which can take place in order to test ~Z~4~8~8 that PCB type. The path throu~h the tree for a particular PCB i dictated by the actual results of each event (i.e. process step) as they occur. As i8 apparent, the tree will typically have multiple branches due to the alternative results which might occur at a given node, e.q. pass, fail, etc. Methods for creating, storing and performing operations on such "tree" structures are readily available as evidenced by a text entitled "Data Type~ and Structures" by C.C.
Gotlieb and Leo R. Gotlieb publi3hed by Prentice Hall ih 1978 (reference chapters 6 and 7).
An example process sequence file is shown in Figure 14a. In this figure, each node of the tree is shown as an overlapping group of labelled boxes. With each node in the tree, there are identified the process name (e.g. functional te~t, repair), the physical location in the sy~tem where the process can take place (e.g. test ~tage lla or test stage llb, repair stage 15) and a reference to any associated components (e.g.
a particular type of fixture assembly 47) required to "fiet-up" and complete the proce~ of that node. The coded indicators associated with the results of the proces~ are indicated as triangles with internal label~. The results of each operation are used to - 25 determine which step will occur next for a particular board being proce~ed. The results are supplied to the master control unit by the workstation controller~ via the host and are not the detailed output of the test stage. A base priority is as~ociated with each process sequence file. The priority i~ u~ed as described hereinafter to regulate resource allocation between board typeq. In addition, a file i~ created which contains a look-up table or similar device correlating a PCB type to a fixture as~embly 47 which corresponds to such PC~ type. Thi~ fil~, hereinafter referred to ~ 79~8 as a fixture correlation file, i8 also provided as input to the master control unit 17. Also included within the fixture correlation file i8 a liQting of any other components such as cover assemblies 62 or upper fixture assemblies 47' which will be required to test and/or repair that PCB type. Typically the process sequence file and the ~ixture correlation file will correlate the PCB type to the corresponding components by utilizing a serial number located on the PCB, of which certain digits refer to the PCB model or type, and the remaining digits uniquely identify each individual PCB of that type. In the preferred embodiment, thiQ serial number is associated with the particular carrier in which the PCB is mounted. The carrier is uniquely identified by a bar code sticker permanently affixed to the carrier which can be automatically scanned by the test system 10 according to the present invention. Thus once the bar code for a given PCB is scanned, the operating system can search the process sequence file through the master control unit 17 and ascertain the various station~ within the test syQtem which will be required to test that particular PCB 19. Similarly the fixture correlation file can alRo be ~earched to identify the other components which will be required to teQt that PCB. A
mesQage can be displayed to the operator to make certain that the correct fixture assemblies 47 and, depending upon the size of the batch o~ PCB~ to be tested, an adequate number of cover assemblies 62 and flxture assemblies 47, etc., are loaded within test system 10. In the preferred embodiment, fixture as~emblie~ 47 and cover as~emblies 62 are stored within a storage staton S when not in use. The carriers 20 (containing the PCB~ 19 which are to be te~ted) can then be individually inserted into the te~t system 10 , - - .
' .

or these components can be stored within a buffering ~tage 16 and automatically transported by the conveyor means. In the preferred embodiment a file, hereinafter referred to as the component location file, is created containing component location information and i8 maintained by the ma~ter control unit 17. In this manner the loading and unloading of the various t~t stages 11 and 15 and the transport of the various fixturing assemblies 47, cover assemblies 62, and PCB~
1~ 19 can be facilitated by the master control unit 17 in conjunction with diQtributed controllers of the test system 10. It ~hould be noted that the information thus far described a~ being required as input can be provided through standard input (e.g. Xeyboards, lS magnetic storage devices, LAN connection~ with another computer, etc.) interfaces (See Fig. 14) to the master control unit 17.
In the preferred embodiment of the present invention, a component input/output station 80 is included within the system 10. The basic input/output station 80 comprises a conveyor unit 12 combined with a bar code reader 81 and buffering stage 16. Since the carrier 20, the fixture assembly 47 and the cover assembly 62 all have the same outer configuration, the input/output station 80 can be utilized as a system input/output device for all components. Accordin~ly, a bar code can be placed on all component~ to provide an identity to the master control unit 17. Upon insertion of a component into the input/output station 80, the bar ~ode reader 81 would scan the component and input the erial number associated with the component to the master control unit 17. The master control unit 17 could then ascertain a destination for th-e component by examining the proces~ sequence file, e.g. an empty cell within a bufferin~ stage 16, and direct the conveyor units to transport the component to that cell. The identifying number for the component and a code identifying the destination, e.g. the buffering stage 16 and the particular slot within that stage are stored in the component location file. As the components are processed by the system 10 this component location file is dynamically updated to provide an indication of the current location of each of the components.
Reference is now made to Figures 14b, 15 and 15a for a description of the overall operation of test system 10. During start-up of the test system 10 the master control unit 17 reads the system configuration file to determine what modules exist within the test system 10 as well as their functions and relative locations. The master control unit 17 then initializes the system configuration by interrogating each of these various modules over the networX 14 and determining ` whether the modules are on-line and functioning. If a particular module is not functioning the user is so informed. This module can then be mapped out of the system or the malfunction can be corrected as determined by the user. The control programs for each - of the ~icroprocessors located within the various modules are then downloaded from the master control unit 17.
Figure 14b depicts a control structure for the system 10 of Figure 1, in a block diagram fashion.
The master control unit 17 i8 shown at ~he top of the - figure with local area network 14 connecting it to the various controllers. Each station of the system 10 is equipped with a microprocessor controller.
Additionally, each conveyor unit 13 contains a microprocessor controller for it and some number of slave conveyor units 12. This distributed controller 3s epproach gives the maeter ccntrol un~t 17 ccntrol over , ., all aspects of the system lO without requiring that all - software be executed on the master control unit.
In the preferred embodiment, the controller for storage station S i5 housed in one of the buffering stages 16 making up the station. This controller operates the buffering stages 16 on direction from the master control unit 17 to effect the storage and retrieval of componentsO
The controller for each conveyor unit 13 is hou~ed in the base of the unit and controls the conveyor unit 13 and slave conveyor unit~ 12 on direction from the master control unit 17. In the preferred embodiment each conveyor unit 13 in a system is equipped with a microprocessor controller. The master control unit 17 coordinates activity between the controllers of the conveyor units 13 to effect the transfer of components between stations of the system 10 .
Each test station containing a test stage 11 contains a microprocessor controller. In the preferred embodiment, the controller operates the buffering stage 16, the conveyor unit 12, the automation inter~ace 38, and the test stage lla or llb of the station on direction from the master control unit 17. The controller additionally ascertains, through an interface with the test ~tage, the result of any test which is performed. ~his result (for example PAS5/FAIL) is later used by the master control unit 17 i~ routing the PCB 19 to any subsequent station.
The microprocessor controller in the repair station controls the buffering stage 16, the conveyor unit 12, the I/O device, and the repair stage 15 in the repair station, on direction from the master control unit. In a manner ~imilar to the test station, the controller in the repair station also appraises the master control unit 17, via the host, of the completion of any repair activity to facilitate the routing of the repaired PCs 19.
The input/output station 80 contains a microp~ocessor controller which controls the buffering ~tage 16, the conveyor unit 12, and the bar code reader 81 of the input/output station on direction from the master control unit 17. In the case of the input/output ~tation 80 the microprocessor controller also appraises the master control unit 17 of the arrival of a carrier containing a PCB 19 to be processed. In the message, the bar coded identity of the carrier 20 and the PCB 19 are provided to the master control unit 17. These items of information are maintained by the master control unit 17. The master control unit 17 also maintains the process sequence file which contains routing information and a base priority for the new PCB 19. The identity information i8 used in accordance with the proce3s sequence file to control the path taXen by the PCB 19 in respon~e to the result~ from the stations to which it is sent.
The preferred embodiment of the present invention utilizes substantially identical microproceqsors in the various modules and stores the specific control program~ for the variou~ types of modules in memory or in a file which can be down loaded to the variou~ microproces~ors as required. Each of the microprocessors i~ equipped with a ROM based monitor program which execu~e~ on power-up and readies the microprocessor to receive command3 over the network 14. The specific control programs which are downloaded are determined by the configura~ion of the ~ystem and the 3pecific module~ employed. This concept along with - the master/slave concept already discussed with regard to the conveyor units and the buffering stages affords the user lower costs and added flexibility for easily reconfiguring the system to tailor it to the particular requlrements present. Furthermore it eliminates the need for fixed memory or disk drives at each module.
Once the various control programs are loaded, the moveable members of the various modules are "homed" to Xnown positions, and the appropriate sensors are interrogated to ensure that such homing has occurred.
~fter every module has been checked and initialized in this manner the user is informed that the system is ready for use.
Testing and/or repair of PCBs within the test system 10 is done on a priority basis, with the intent of keeping the test and repair stages occupied to the fullest feasible extent. Through one of the various input devices, the user associates a base priority code for the PCB type dependent upon production requirements. When a PCB is entered into the system 10 as previously described it is assigned the priority code which was provided as input to the master control unit 17 as part of the process sequence file for Pcss of this type. As has been previously stated, the master control unit 17 in combination with the bar code reader has already ascertained the identity and type of the PCB being supplied to the system 10 for test and/or repair. In the preferred embodiment of the present invention thi~ priority code i8 dynamicO That is, a PCB awaiting an operation to be performed at a particular stage or module will have it~ priority code or rating increased as a function of the time it is waiting. This prevents a PCB from being held at a given stage or module in the system for an unlimited period of time such as might be the case when it is preempted by a large batch of hi~her priority PCBs.
The PCB returns to its base priority, i.e. that taken ~'~79~

from the process sequence file, after the required operation has been performed at that particular module or stage. Since the PCBs must share the various modules, a pre-emptive scheduling technique i8 employed, in which operations on PCBs having the highest priority will generally be processed first.
Scheduling algorithms to implement a pre-emptive type system are readily available as evidenced by a text entitled "Operating System Principles" by Brinch 10~ Hansen, published by Prentice Hall in 1973 treference chapter 6).
A flowchart illustrating the dynamic priority scheme for any given PCB and the preemptive scheduling technique for using the dynamic priority to schedule the use of a test/repair station is provided in Figure 15a.
The essential purpose of the control system of the present invention is to track and control the movement of PCBs between the various workstations. A
mix o~ different board types must be tracked and controlled simultaneously. In a fully automatic manner the PCBs are routed from station to station with any necessary setup being performed as required. The method of establishing the rules, i.e. process sequence files, used to guide the different types of PCBs through the test and repair system, was described ` earlier. An example of how the rules are applied by the master control unit will now be provided. It should be remembered that although PCB routing is the primary func~ion o the master control unit, it is by no means its sole activity. Monitoring the ~tatus of work~tations and conveyor units is continuous as well as providing status reports on production and equipment to a factory HOST computer on demand.

-~6-Basically the routing control portion of the master control unit software i8 an infinite loop, repeatedly examining the status of each printed circuit board within the control of the system and acting on S any changes provided by workstation activity. This loop can be regarded as having two sections as shown in Figure 15a. The top section determines all PCBs which have completed a step in their processiny and ascertains the next required step. The bottom section applies load balancing and priority guidelines in order to determine which PCBs will be granted workstation time to proceed and which must wait.
As earlier discussed in connection with the creation of process sequence files, PCBs which are handled by the system are regarded as progressing in a step by -qtep fashion. At the completion of a step, the product "asks" for the next step based on the result of the first, thereby taking a "route" determined by actual events. The steps are regarded as "proce~se~"
which may be any required action at some point in the manufacturing or testing o~ the PCB. These processes can be performed by workstations, with perhaps several stations being able to perform a process by virtue of a "setup" change. For example, several workstations may contain test equipment which can be used to perform tests on different types of PCBs with appropriate fixtures and test programs. Workstations are regarded aR the system resources with processes competing for themO The determination of which workstations are performing some process for a given PCB type and for how long, i.e. a preemptive scheduling technique, is - what will now be described.
A workstation which has performed some proce~s step on a PCB notifie~ the Master Control Unit, via the host, of the completion of that step and any ~'~7~4~

associated results, for example, pass or fail in the case of a testing step. Those PCBs for which such a completion message has been received since the last pass through the loop are considered ready to advance.
For each such PCB the appropriate process sequence file i~ referenced, with different PCB types perhaps having different process sequence files. From the process sequence file for each PCB a determination is made of the next step or procsss required for the PCB, a base priority associated with the process sequence file i5 attached to the PCB, and a "bid" for that process is registered on behalf of the PCB. This sequence is repeated for all PCBs which have been deemed ready to advance with the distinction that each PCB left waiting by the last pass through the loop has an increment applied to its priority before a new bid i3 registered.
This is done to prevent a PCB with a low base priority from waiting indefinitely for higher priority PCBs to be processed.
Once all the bids for processes have been regi~tered, the next section (labeled as "for every bidding process" in Figure 15a) applies the priorities of the bids in order to make a selection of which processes will be performed at workstations. The selection may be done in essentially the following manner. Each process step for which a bid has been registered has associated with its process sequence file, a list of the worXstations which may be used to per*orm that process, and also the identity of any fixture which might be required by the station.
Contention for workstation time may be resolved by granting time to the proceRs for which the total bid is highe~t, That is the sum of all ~he bids. If the worXstation in contention is currently serving the highest bidder, PCB~ requiring that step are advanced ~Z7~38 and will be physically routed to that station. In the case of more than one station serving a function, PCBs are routed to the station with the least product in its station buffer to keep stations balanced.
If the workstation in contention is serving another process step, it may be preempted. This means that any fixture change required will be invoked as well as any program changes needed by the station equipment.
These stepR are repeated for all processes requesting worXstation time. PCBs which cannot be serviced at the end of thi~ section are delayed and reconsidered in the first section of the next pass through the loop as noted earlier.
In its preferred embodiment the system lO
will process multiple PCBs in parallel. For ~implicity and clarity purposes, the discussion which follows will view the system 10 from the perspective of a single highest priority PCB under test. It should be noted, however, that generally other high priority PCBs are being processed concurrently, i.e. in parallel. The configuration file and appropriate process sequence files for ~uch highest priority PCB are read by the master control unit 17. These files have been provided as input to the master control unit 17 by one or more of the alternatives previously described. The master control unit 17 will determine from these files the station which i5 required to perform the first testing or repair operations to such highest priority PCB.
Similarly, the required other components, e.g., the fixture assembly 47 and cover assembly 62 for repairing and/or testing such PCB will also be established by reading the fixture correlation file. The master control unit 17 will then read the component location file to determine if such components are within the ~L~d7~' ~

system and the present location of the required components and the PCB. If such components are not within the system 10 the user will be instructed to input such components. These other components required to test such highest priority PCB are then automa~ically tran~ported to the required module. The ma~ter control unit 17 i~ designed to interrogate on a periodic basis the various sensors included within the system 10 to update the location information (as contained within the component location file) for all components within the system 10 and ensure that the required components are present and accounted for and that on a real time basi~ two or more components (e.g.
carriers 20, fixture assemblies 47 and cover assemblies 62) never try to occupy the same space at the same time. Similarly the appropriate sensors will also be interrogated for the status of each of the modules within the sy~tem 10 which form the various paths available to tran~port the components, to ensure that the modules are functioning, available, and properly positioned for such transport. Methods for controlling the use of resources such as conveyor units and fixture assemblies by competing tasks (PCBs in this application) are readily adaptable from methods outlined for computer peripheral control in such text as "Operating System Design, The XINU Approach" by / Douglas Comer, published by Prentice Hall in 1984 (reference chapters 12 and 16). In this manner the optimum aYailable path to such test and/or repair stages can be established for each component and the proces~ of transporting such highe~t priority components from their present location to the required te t and/or repair stages will begin. From the-information contained in the configuration file, the master control unit 17 can ascertain the rotations of ' :

the rotating conveyor unit 13 and the direction of rotation of the dc motors 34 in the conveyor units 12 and 13 required to transport these components to the specified stages 11 or 15 and the instructions which will be required to be issued on the network 14 to the appropriate drivers within the various modules to perform the transport. Accordingly the master control unit 17 will timely activate the appropriate drivers to perform ~uch transport. Similarly the appropriate sensors can be activated or interrogated to ensure that the required actions have ~aken place. This drive and sensor information is conveyed to and from the master control unit 17 via the networ~ 14. Concurrently the component location file is dynamically upaated as a result of such sensor information to, as previously described, continually track the location of the variou~ components within the system. The master control unit 17 is therefore kept current as to whether a required module has performed the required operation.
After such operation has been performed, and depending upon its priority rating the PCB will eventually be transported to the required test or repair station according to the order specified by the process sequence file. When all the requ~red components are present at the specified test or repair station 11 or 15, the master contrcl unit 17 or the host computer to which it is connected will activate the station to begin performing the required operationsO In the preferred embodiment the management of test data is performed by a host computer, not part of the present invention, interfaced with the master control unit 17 via the network 1~. The particular test programs which are required to test the PCB are stored within the host computer and downloaded as required. The identity of the appropriate test program is part of the process sequence file. Furthermore the host can track the test history o the PCBs being processed in order to create management reports for the user.
The completion and results of the tests of a given PCB at a given workstation (e.g. PASS/FAI~) are conveyed to the master control unit by the controller of that workstation. The master control unit 17 via the process sequence file determines the next event or operation which is to occur. Assuming an adequately high priority, the required conveyor ~nit activation will be analyzed and carried out according to *he process as has been described to facilitate this next event or operation. The master control unit 17 will thus read the process sequence file and ascertain the next test or repair stage required. If no additional - test or repair operations are required, e.g. the PCB is finally accepted or rejected, the PCB will, according to its priority rating, be transported to the buffering stage 16 of the component I/0 station 80 for removal from the test system 10 as indicated by the process sequence file for PCBs of that type. If additional test or repair operations are required, the appropriate stages and modules will be interrogated and selected.
In addition, the master control unit 17 will determine the associated components which will be required and which have been specified within the fixture correlation file. These may or may not be the same components used for the first test. If the appropriate fixture assemblies 47, cover assemblies 62, etc. are already within the system, their current location will be known by an entry within the component location file, otherwi~e such components and the relevant lo~ation information must be provided via one of the above mentioned input devices. A priority rating is effectively give~ to the fixture assembly 47, cover ~Z~ 8 assembly 62, etc., based upon the current priority rating of the PCs being tested. Finally, the activation of the conveyor units which will be required to transport the components to such specified test or repair stage will be determined and initiated.
This process is ~epeated until such time as all test and repair operations to be performed by the system 10 have been completed. In the same manner as has already been described, the completed PCBs 19 and 19 associated components are transported to the buffering stage 16 of the component I/0 station 80 for removal.
- lf required, the system 10 will also allow the manual removal of a PCB and associated components at a test or repair stage 11 or 15. If this is done the master control unit 17 must be informed of such removal via the miscellaneous I/0 devices discussed, e.g. a bar code reader. It should be noted that, typically, fixture assemblie~ 47 and cover assemblies 62 will remain at a given test station until the tests requiring such components at that station are completed or until the master control unit 17 determines that the particular station will be required to test a higher priority PC8. This may, or example, occur when the ~um of the priority codes for all the PCBs 19 of the same type (i.e., a new batch) which are being entered into the system 10 exceeds the sum of the priority codes for all of the PCBs 19 of the type currently under test (i.e., the batch being tested). In this event the fixture and/or cover presently in that station may be temporarily bumped or replaced by those required for the higher priority batch, as depicted in - ~ig. lla.
Thus the system 10 according to the present -invention is able to concurrently and automatically process PCBs of different types, sizes, shapes, and ,.~. , ~.

~2~

configurations with little or no manual intervention required. It i9 able to do so in an accurate, timely, and cost effective manner, with maximized throughput, thereby substantially eliminating the aforementioned limitations associated with the prior art. It must be understood that the description of the present invention as et forth above does not attempt to recite all the advantages associated therewith nor does it attempt to recite in detail all the structure employed.
Furthermore, for the sake of clarity and understanding, certain operations and the detailed structure of various components, which are considered to be within the scope of one skilled in the art in light of the teachings set forth herein, have not been discussed.
Having thus described several embodiments of the present invention, it must also be ~nderstood that changes may be made in the configuration, size, makeup, shape, or order of some of the parts, circuit~, or methods described herein without departing from the present invention as recited in the appended cl~ims.

Claims (51)

1. A method for automating and controlling the testing of PCBs comprising the steps of:
determining the configuration of the stages within a test system having at least one test stage, as well as the available paths between such stage , and providing said paths and configuration as an input parameter to a controller, associating a unique identity to each type PCB to be tested, associating a unique identity to a corresponding circuit means for each such PCB
type, which circuit means are adapted to make electrical connection between selected nodes of the electrical circuits of a PCB of such type and electrical circuits of said test stage adapted to stimulate such nodes and measure the response of such nodes to such stimulus when a PCB of such type, such circuit means and such stimulus and measurement circuits are brought into operative engagement, correlating the PCB identity for each PCB
type to the corresponding circuit means identity, and providing said correlation as an input parameter to said controller, determining a process sequence to test each type of PCB, said sequence identifying the operations required and the order in which such operations will be required, and providing said sequence as an input parameter to said controller, determining the PCB type of a PCB to be tested and providing the determined PCB type as an input parameter to said controller, transporting the PCB to be tested to stages within said system with conveyor means adapted to interface with and interconnect such stages, under control of said controller so as to implement operations at said stages according to the order determined by said process sequence determination for said determined PCB type, and along the path determined by said paths and configuration determination, transporting under control of said controller said correlated and corresponding circuit means for said determined PCB type to the test stage with said conveyor means, according to the order as identified by said process sequence determination, and along the path identified by said paths availability and configuration determination, operatively engaging such PCB, such circuit means, and such stimulus and measurement circuits of such test stage, initiating operation of such test stage to stimulate selected nodes of such electrical circuits of the PCB, and measure the response of selected nodes of such electrical circuits of the PCB to said stimulus, and indicating to said controller a result of such test stage operation.

2. A method as claimed in claim 1 wherein said step of associating a unique identity to each type of PCB to be tested comprises assigning a serial number to each PCB at least a portion of which is unique to the PCB type and said step of associating a unique identity to a corresponding circuit means comprises assigning a serial number to such circuit means at least a portion of which is unique to such circuit means type, and wherein said step of correlating the PCB identity to the corresponding circuit means identity comprises having said PCB type portion of said PCB serial number correspond to said circuit means type portion of said circuit means serial number.

3. A method as claimed in claim 1 wherein the step of determining the configuration of the stages within a test system comprises designing the configuration on an interactive graphics display and automatically generating a corresponding system configuration file.

4. A method as claimed in claim 1 wherein the step of transporting the PCB to such stages comprises mounting the PCB within a carrier and adapting such carrier to support PCB of different sizes and configurations while maintaining substantially the same the outer configuration of side members of the carrier and lateral dimension of the carrier.

5. A method as claimed in claim 4 wherein the step of transporting the PCB to such stages further comprises interconnecting such stages with bi-directional modular conveyor units and adapting such conveyor units to transport such carrier.

6. A method as claimed in claim 5 wherein the step of determining the available paths between such stages comprises including sensors within such conveyor units adapted to determine the present status of such conveyor units and interrogating such sensors.

7. A method as claimed in claim 5 wherein the step of transporting said correlated and corresponding circuit means comprises adapting such circuit means to maintain substantially the same outer configuration of side members and lateral dimension as such carrier, thereby affording the transport of such circuit means by such conveyor units.

8. A method as claimed in claim 7 wherein the step of operatively engaging such PCB, such circuit means, and such stimulus and measurement circuits comprises providing an automation interface at said test stage having structure adapted for:
conveying such circuit means from a first operating level to an operating level of such test stage, positioning such circuit means at a known position with respect to such test stage, electrically connecting such circuit means to the stimulus and measurement circuits of such test stage, and conveying such carrier from the first operating level to an operating level of such test stage, positioning such carrier as a known position with respect to such test stage, electrically connecting selected nodes of the PCB
mounted within such carrier to such circuit means.

9. A method as claimed in claim 5 further comprising mounting a vacuum sealing member within a supporting frame and adapting such frame to maintain substantially the same outer configuration along side members of the frame and lateral dimension as such carrier, thereby affording the transport of such sealing member by such conveyor units.

10. A method as claimed in claim 9 wherein the step of operatively engaging such PCB, such circuit means and such stimulus and measurement circuits comprises adapting such test stage to include an automation interface having structure adapted for:
conveying such circuit means from a first operating level to an operating level of such test stage and positioning such circuit means at a known position with respect to such test stage, conveying such carrier from the first operating level to an operating level of such test stage and positioning such carrier at a known position with respect to such test stage, conveying such vacuum sealing member from the first operating level to an operating level of such test stage, and positioning such sealing member at a known position with respect to such test stage, and actuating a vacuum to draw the PCB, the circuit means and at least a portion of the stimulus and measurement circuits together, thereby electrically connecting such circuit means to the stimulus and measurement circuits of such test stage and electrically connecting selected nodes of the PCB mounted within such carrier to such circuit means.

11. A method as claimed in claim 1 further comprising determining of another PCB exists which is to be tested and which has an identity which is also correlated to the identity of the circuit means currently at such test stage, transporting such other PCB to such test stage, operatively engaging such other PCB, such circuit means, and such stimulus and measurement circuits of such test stage, initiating operation of such test stage to stimulate selected nodes of such electrical circuits of such other PCB, and measure the response of selected nodes of such electrical circuits of such other PCB to said stimulus, and indicating to said controller a result of such test stage operation on such other PCB.

12. The method of claim 1 wherein multiple PCBs are processed by the stages of the system and further comprising the step of: determining the sequencing of PCBs by the system in accordance with a dynamic priority rating system and preemptive scheduling technique.

13. The method of claim 12 wherein said multiple PCBs are processed in parallel and each PCB is assigned a priority rating which increases from a base rating as a function of waiting time for the particular operation and returns to said base priority rating when the operation has been performed.

14. The method of claim 1 wherein said process sequence comprises a decision tree in which a subsequent operation is determined by the results of the previous operation and wherein the controller operates the conveyor means, and initiates operation of the stages in accordance with said decision tree.

15. The method of claim 1 wherein the controller tracks the location of the PCB in the test system.

16. A method for automating operations to be performed on a PCB in a multi-station system, comprising the steps of:
associating a unique identity to each type PCB to be operated upon, identifying the particular type of PCB to be operated upon to a controller, determining the configuration of the system and the availability of stations in the system to perform such operations, as well as an available direct path between each pair of such stations, and providing said availability and configuration determination as an input parameter to said controller, determining a desired process sequence for performing such operations, said sequence identifying operations and the order in which the operations are to be performed depending upon the results of the previous operations, and providing said sequence as an input parameter to said controller, transporting the PCB to stations in the system with conveyor means adapted to interface with and interconnect such stations, under control of said controller according to the order determined by said process sequence determination, and along direct paths between available stations determined by said availability and configuration determination, and operatively engaging such PCB in such stations according to the order as identified by said process sequence.

17. A method as claimed in claim 16 further comprising:
associating a unique identity to corresponding circuit means for such PCB type, which circuit means a adapted to make electrical connection between selected nodes of the electrical circuits of such PCB and electrical circuits of certain of such stations when such PCB
and such circuit means are brought into operative engagement, correlating the PCB identity to the corresponding circuit means identity, and providing said correlation as an input parameter to said controller, transporting said correlated and corresponding circuit means to such certain stations with said conveyor means adapted to interface with said stations, according to the order as identified by said process sequence determination, and along the path identified by said availability and configuration determination, and operatively engaging such PCB and such certain stations with said circuit means.

18. The method of claim 16 wherein the step of determining the configuration of the system comprises designing the configuration on an interactive graphics display and automatically generating a corresponding system configuration file.

19. The method of claim 16 wherein the step of transporting the PCB to the stations comprises:
mounting the PCB within a carrier having protruding side ridges, and interconnecting the stations with bi-directional modular conveyor units adapted to support the carrier by its side ridges and to impart motion to the carrier, as directed by said controller.

20. The method of claim 16 wherein multiple PCBs are processed by the stations of the system simultaneously and further comprising the step of:
determining the order of processing of PCBs by the system in accordance with a dynamic priority rating system and a preemptive scheduling technique.

21. An apparatus for automating a tester of the type utilized for the testing of PCBs, which tester includes stimulus means for generating a pre-determined signal adapted to stimulate pre-determined nodes of the PCB and sensor means for measuring the response of such nodes to such signal, said apparatus comprising:
circuit means for establishing electrical connection between such nodes of the PCB and such stimulus and sensor means, means for positioning and supporting the PCB
at a known position with respect to such circuit means, common conveyor means for transporting at least some portion of said circuit means and the PCB to and from said tester, and automation interface means for automatically loading and unloading said portion of said circuit means onto the tester and the PCB onto and from said positioning and supporting means.

22. An apparatus as claimed in claim 21 further comprising a carrier for mounting a PCB
therein, said carrier being adapted to accommodate a range of sizes and configurations of PCBs without requiring an adjustment of said conveyor means, and wherein said portion of the circuit means comprises a fixture assembly having substantially the same exterior configuration along its sides as said carrier.

23. The apparatus of claim 21 further comprising:
a buffering stage for storing multiple PCBs, said buffering stage being located at an end of said conveyor means opposite the automation interface, and a control means for controlling the operation of said buffering stage, conveyor means, automation interface and said tester.

24. Apparatus for automating the testing of PCBs comprising:
a test stage having receiver means;
circuit means for establishing electrical connection between said receiver means and predetermined nodes of an electrical circuit on a PCB to be tested: and automation interface means for automatically loading and unloading and precisely positioning said circuit means on said receiver means, and for automatically loading and unloading and precisely positioning the PCB on said circuit means.

25. The apparatus of claim 24 further comprising:
conveyor means for conveying said circuit means and PCBs to and from said automation interface means; and control means for synchronizing the operation of said test stage, automation interface means, and conveyor means.

26. An apparatus as claimed in claim 25 further comprising carriers for mounting said PCBs, said carriers being adapted to accommodate a range of sizes and configurations of PCBs and being standardized in width and side configuration.

27. An apparatus as claimed in claim 26 further comprising:
vacuum means for drawing a PCB into contact with said circuit means after said automation interface means has loaded said PCB onto said circuit means, and cover means for sealing any openings in the PCB which might otherwise prevent the operation of said vacuum means; and wherein said automation interface is capable of supporting and adjusting the elevation of said cover means, and said cover means is adapted to be transported by said conveyor means.

28. An apparatus as claimed in claim 27 further comprising buffering means for storing PCBs to be tested, said buffering means being adapted to selectively feed carriers supporting PCBs to said conveyor means.

29. A carrier for use with a multistation test system of the type utilized for testing and/or repair of PCBs and having conveyor means interconnecting said stations, aid carrier comprising:
a frame and means for supporting a PCB
therein, which means is adapted to accomodate a range of sizes and configurations of PCBs without requiring an adjustment of said frame, said frame having two opposed generally parallel side members, each of said side members being provided with a longitudinally extending laterally protruding ridge for riding within opposed channels of the conveyor means, and at least one of said side members having a surface disposed substantially perpendicular to the direction of lateral protrusion of its ridge and adapted to be engaged by drive means of said conveyor means.

30. Automation interface apparatus for use on a PCB test stage comprising:
first means for receiving and precisely depositing a test fixture assembly on a test stage;
second means for receiving and precisely positioning a PCB to be tested on said test fixture assembly third means for receiving vacuum cover means, supporting said vacuum cover means in a non-interfering elevated position and, on command, superimposing said vacuum cover means over said PCB to facilitate vacuum drawing of said PCB into electrical connection with said test stage through said fixture assembly: and fourth means for expelling said PCB, fixture assembly and cover means from said apparatus.

31. A modular conveyor unit for use in transporting a component having protruding side ridges and especially suitable for use in a PCB test and/or repair system, comprising:
a generally horizontal chassis supporting a pair of parallel substantially vertical spaced apart guide rails, the guide rails defining opposed longitudinally extending channels adapted to receive the projecting side ridges of the component: and reversible drive means supported by said chassis for engaging a surface of said component and imparting motion to said component in a longitudinal direction.

32. The conveyor unit of claim 31 further comprising means for controllably rotating the chassis about a generally vertical axis to a new orientation.

33. The conveyor unit of claim 31 wherein said surface comprises a generally vertical side surface of the components the drive means comprises a pair of driven rollers, one near each end of one of said guide rails; and further comprising stop means supported by the chassis and operational to selectively prevent further motion of a component in said unit.

34. The conveyor unit of claim 32 further comprising:
first sensor means for sensing the presence of a component in said unit; and second sensor means for sensing the orientation of said rotated chassis.

35. The conveyor unit of claim 34 further comprising a controller for controlling the drive means, first and second sensor means, and rotating means of said unit, and drive means and first sensor means of adjacent conveyor units.

36. Buffering stage means for storing components, and especially suitable for use in a PCB
test and/or repair system comprising:
receptacle mean having a plurality of generally horizontally disposed cells, each cell being adapted to receive and support a component therein;
frame means supporting said receptacle means for bidirectional movement relative to said frame means along a generally vertical axis;
first drive means for controllably moving said receptacle means relative to said frame means;
second drive means for selectively engaging a component in any of said cells and controllably expelling said component from the cell; and sensor means for sensing the presence of components within said cells and the relative position of the receptacle means with respect to said frame means.

37. The buffering stage means of claim 36 wherein each component has protruding side ridges and each cell is configured with side channels adapted to receive said ridges; and said second drive means comprises at least one drive roller positioned to selectively engage a generally vertical side surface of a component.

38. An automated multistation system for performing operations upon PCBs, at least one of said operations requiring another component, comprising:
an input/output station for loading and unloading PCBs and other components into and out of said systems;
a plurality of work stations;

a transport system interconnecting all of said stations for transporting PCBs and said other components directly between any selected stations in either direction: and control means for supervising transport of said PCBs and other components by said transport system, operation of said input/output station and activation of said work stations.

39. The automated system of claim 38 wherein said transport system comprises an arrangement of interconnected modular conveyor units, each of said units being capable of selectively imparting movement in opposite directions to a PCB located thereon.

40. The automated system of claim-39 wherein at least one of said conveyor units is capable of rotating a PCB located thereon.

41. The automated system of claim 40 wherein said control means includes a conveyor controller associated with one of said conveyor units, said conveyor controller controlling the operation of more than one of said conveyor units.

42. The automated system of claim 38 wherein said control means further comprises:
interactive graphic means to assist in developing and visually display a desired configuration of the system, and means connected to said interactive graphic means for automatically generating a system configuration file identifying system interconnections and control programs for the desired displayed configuration.

43. The automated system of claim 38 wherein said transport system is adapted to transport components and wherein said components comprise:

a universal carrier for mounting individual PCBs, said carrier being adaptable to accomodate a range of sizes and configurations of PCBs; and fixture assemblies.

44. The automated system of claim 43 wherein said components further comprise vacuum cover assemblies and all of said components have in common an exterior configuration which facilitates transportation by said transport system.

45. The automated system of claim 38 wherein said control means routes a PCB to stations in accordance with: a process sequence identifying the operations required and the order of performance of said operations for the particular type of PCB being processed, and the results of prior operations on said PCB.

46. The automated system of claim 45 wherein multiple PCBs are processed in parallel and wherein said control means implements a dynamic priority rating system and pre-emptive scheduling technique for the multiple PCBs.

47. The automated system of claim 46 wherein said control means tracks the location of the PCBs and monitors the status of the stations and transport system.

48. The automated system of claim 38 further comprising automated buffering stage means associated with at least one of said stations, said buffering stage means being capable of temporarily storing multiple PCBs and interfacing with said transport system.

49. The automated system of claim 48 wherein a different automated buffering stage means is associated with each station; and further comprising a storage station comprising tandem buffering stage means.

50. The automated system of claim 48 wherein at least one of said work stations comprises a test station: said test station comprising a test stage, automation interface means for loading and unloading PCBs on said test stage, and buffering stage means; and wherein said control means includes a test station controller providing coordinated control over the operation of the buffering stage means, and automation interface means, and activation of the test stage.

51. The automated system of claim 38 wherein said control means comprises a master control means and a network of distributed individual station control means and transport system control means.