WO1999041964A1

WO1999041964A1 - Component assembler

Info

Publication number: WO1999041964A1
Application number: PCT/EP1998/004986
Authority: WO
Inventors: Daniel Peana; John O'halloran; Billy Diggin
Original assignee: Motorola B.V.
Priority date: 1998-02-12
Filing date: 1998-07-13
Publication date: 1999-08-19
Also published as: GB2321133A; GB9802959D0; GB2321133B; JP2002503890A; IE980557A1; EP1053665A1

Abstract

An apparatus for placing components on a substrate is provided, the apparatus comprising: (i) one or more component holders for placing components on the substrate, the said component holder(s) being mounted on one or more bars; (ii) a pair of guide rails, the bar(s) being mounted on the guide rails by means of mounts which can move along the guide rails; (iii) control means for setting a variety of orientations of the component holder(s) relative to the substrate by varying the locations of the moveable mounts on the guide rails. The apparatus can be used to assemble components onto printed circuit boards. The apparatus provides high components onto printed circuit boards. The apparatus provides high component placement precision, mechanical simplicity and a high component through-put.

Description

1

Component assembler

Technical Field

The invention concerns apparatus and methods for component placement during the manufacture of arrays of components.

Background

Arrays of components may be assembled for many purposes. Typically,

'packages' and discrete circuit components are placed on a substrate, such as a printed circuit board.

These components may take a great variety of forms and shapes. For example, integrated circuits may be of the dual in-line pin (DIP) form. Other components such as capacitors, resistors, sensor packages or piezoelectric sound transducers may have to be added to a printed circuit board to form a particular circuit.

A variety of machines is available for assembling arrays of components. These machines tend to have certain common features. Amongst these is some form of feeder mechanism for bringing components to the machine, i.e. to the location where the component array is to be assembled. Some arrangement of picking and transporting device(s) will then take an individual component from the feeder mechanism and place it on the substrate on which the component array is being assembled.

Known component assembling machines are often very complex. The machine must be able to place a component at a point in space which must be reached by movement in all three dimensions. Additionally, each component must be correctly oriented for placement on the substrate. Clearly, an incorrectly oriented component may have its leads inserted into the wrong sockets on the printed circuit board. The leads may alternatively be bent or broken during the act of inserting the component.

A known prior art component placement device includes actuators for moving a placing head in all three dimensions. This allows the head to be moved in each of the V, y and 'z' directions. The head itself has a motor or other rotating mechanism mounted on it which can rotate a component prior to placing it on the substrate. This motor or other rotating mechanism therefore puts the component which it holds into the correct orientation prior to placement on the substrate. This orientation is conventionally termed the 'theta' axis.

Figure 1 shows a highly simplified view of a prior art component placement apparatus. The placing head 12 carries a motor 14. Motor 14 rotates a component into the correct orientation prior to placement on a printed circuit board. Motor 12 therefore sets the orientation angle 'theta' for the component.

The other elements shown in figure 1 are:

(i) A pair of guide rails 2 and 4; (ii) A cross-member 10, which carries the placing head 12. The placing head 12 may be slideably mounted on the cross-member 10. The cross-member 10 forms substantially a right angle with each of the guide rails 2 and 4.

(iii) Two mounts, 6 and 8. The mounts serve to join the cross-member 10 to the guide rails 2 and 4.

In operation, a component is first picked up from the component feeder mechanism by an engagement member which is part of the placing head 12.

The engagement member may, for example, be constituted by a set of jaws or fingers mounted on the motor 14. The engagement member is not shown on figure 1, and would be obscured from sight by the motor 14 in the view of the apparatus shown in figure 1. The placing head 12 in figure 1 is moved to the point where it overlies the printed circuit board onto which the component is to be placed. This movement is facilitated by movement of the mounts 6 and 8 along their respective guide rails 2 and 4. Before the component is placed onto the substrate, the motor 14 rotates the component until its orientation is correct for placing on the printed circuit board.

Summary of the Invention

A component placement apparatus in accordance with the invention comprises: at least one component holder for placing a component on a substrate, the said component holder being mounted on a first linear support; second and third linear supports, the said first linear support being mounted on the said second and third linear supports by first and second moveable mounts respectively; the first and second moveable mounts being moveable along the second and third linear supports; and control means for setting a variety of orientations of the component holder relative to the substrate by varying the locations of the said first and second moveable mounts on the said second and third linear supports.

The or each component holder of the component placement apparatus may further comprise an engagement member for engaging, holding and releasing components of various shapes and sizes. The second and third linear supports may have their axes lying substantially parallel.

One or both of said first and second moveable mounts may be movable along the second and third linear supports by means of actuators operated by the control means. The component holder(s) may be moveable along the first linear support by means of an actuator or actuators operated by the control means. The first linear support may be connected to the first and second moveable mounts by first and second joints respectively, the first and second joints permitting the angle between the first linear support and the respective one of the second and third linear supports to vary.

One of the said first and second joints may hold the first linear support slideably and the other joint may then hold the first linear support without allowing sliding movement along the direction of the first linear support's axis.

In one detailed arrangement of the invention, a rigid bar constitutes the said first linear support, four component holders are mounted on this rigid bar, a microprocessor constitutes the control means and there are two electrical actuators, each driving one of the moveable mounts independently of the other moveable mount under the control of the said microprocessor so as to set the orientation of the component holders relative to the substrate. There are no motors or other rotation means mounted on the component holders themselves.

In an embodiment in which the first linear support, or bar, can translate along its axis with respect to both mounts, the component placement apparatus may further comprise at least one actuator which translates the first linear support in the direction of its own axis.

The component placement apparatus may further comprise a fourth linear support, the said fourth linear support bearing further component holders and being mounted on the said second and third linear supports by third and fourth moveable mounts respectively.

The component placement apparatus may further comprise a further pair of linear supports serving as guide rails, onto which one or more further linear supports are mounted transversely on slideable mounts. The invention allows a greatly simplified mechanical and electro-mechanical construction in comparison with prior art arrangements such as that shown in figure 1.

In particular, the lack of a motor or other active rotating mechanism on the placing head results in: (i) One motor fewer in the device;

(ii) Less wiring, since there is no need to provide power connections to a motor in the placing head; (iii) A much fighter placing head.

As a consequence of (iii), the bar on which the placing head is mounted and the guide rails which support the bar can be of a lighter construction. The reduction in the weight of the bar leads to less inertia in this element of the apparatus. This reduced inertia allows more rapid acceleration and deceleration, which therefore leads to a higher operating speed of the entire apparatus and greater substrate throughput.

A further advantage of the arrangement of the invention lies in the precision with which the orientation of a component can be set. This depends on several parameters of the apparatus. Principally it depends on:

(i) The precision with which the mounts can be located on their respective guide rails; and

(ii) The design of the bar which is mounted on the two guide rails. In particular the length and rigidity of the bar are critical design parameters here.

Brief description of the drawings

Figure 1 shows a simplified view of a prior art component placement apparatus.

Figure 2 shows a simplified view of a component placement apparatus in accordance with the present invention. Figure 3 shows the main elements of a component placement apparatus in accordance with the invention, including peripheral apparatus.

Figure 4 shows an enhanced version of the embodiment of the invention shown in figure 3.

Figure 5 shows a kinematic diagram which illustrates clearly the most basic principle of the invention.

Figure 6 shows a detailed kinematic diagram illustrating the principle of one embodiment of the invention.

Figure 7 shows the main elements of a component placement apparatus functioning in accordance with the principles illustrated in figure 6, including peripheral apparatus.

Figure 8 shows an enhanced version of the embodiment of the invention shown in figure 7.

Detailed description of the preferred embodiment

Figure 2 shows simplified plan views 2A-2D of an embodiment of the present invention.

In particular, figure 2A shows component holders 12,14,16 and 18 held by a bar 10. Bar 10 forms a first linear support. Each component holder includes an engagement member for grasping, holding and eventually releasing an individual component.

Each engagement member may be suitable for use with a variety of shapes and sizes of component. The engagement member may be constituted by a set of jaws or fingers and it may use a Vacuum' suction arrangement. The engagement member may include a process related placement arrangement, such as a heater to enable bonding of the components after placement.

Also shown in figure 2B are two parallel guide rails, 2 and 4. Guide rails 2 and 4 form second and third linear supports. The guide rails are generally parallel.

First and second moveable mounts 6 and 8 are shown, one on each of the guide rails 2 and 4. These movable mounts can slide along their respective guide rails. In the embodiment shown, each mount can be driven along its guide rail independently of the other mount. A variety of relative positions of the two mounts is thus possible. A control means, which is not shown in figure 2, controls actuators to drive each mount to the desired position.

The component holders may be designed to pick up a variety of components. These components arrive from a feeder mechanism which is not shown in figures 1 and 2. The components need to be placed on a substrate which can consist, for example, of a printed circuit board.

For simplicity, the substrate can be considered to He in the plane containing the guide rails 2 and 4. Furthermore, in this embodiment, the orientation of the substrate relative to the guide rails is constant whilst components are being placed onto the substrate. However, the scope of the invention includes an arrangement where the substrate itself is on a further mount which can change its orientation during the assembly of the components onto the substrate.

In operation, the substrate is located in the region between the guide rails. A component holder, e.g. component holder 14, moves to pick up a first component from the component feeder. This movement consists of a movement of the first and second mounts 6 and 8 along the guide rails 2 and 4 respectively. There may also be movement of the component holder 14 along the bar 10 and/or movement of the bar 10 along its own longitudinal axis. Once component holder 14 has collected a component for placement on the substrate, it moves to the substrate. This movement is achieved in a similar manner to that explained above for the action of moving the component holder to a position where it can pick up a component from the feeder mechanism.

The actuators which move the first and second mounts 6 and 8 along their respective guide rails 2 and 4 can position the ends of bar 10 at any point along the length of the guide rails.

The bar can be positioned such that it makes substantially a right angle with the guide rails. However, the actuators are also able to control the first and second mounts 6 and 8 independently. The mounts 6 and 8 can therefore be positioned such that the bar 10 is not perpendicular to the guide rails 2 and 4. Exactly this situation is illustrated in figures 2B and 2C.

The bar 10 in each of figures 2B and 2C is not perpendicular to guide rails 2 and 4. The slight angle which the bar makes with respect to a perpendicular bisector of each guide rail is marked as theta in each of figures 2B and 2C.

Clearly the angle theta depends on the relative positions of mounts 6 and 8 on their respective guide rails 2 and 4. By incremental movement of one or both of mounts 6 and 8, the angle theta can be set with very fine resolution.

When the component holder 14 holds a component for insertion into a substrate, the angle theta determines the exact orientation of the component. The invention therefore allows the setting of an exact orientation for a component to be inserted, by precise positioning of mounts 6 and 8. Clearly the control means which controls the position of mounts 6 and 8 therefore has control over the orientation of a component held by any or all of the component holders 12,14,16 and 18.

The mounts 6 and 8 are designed such that bar 10 can take a variety of angles relative to the line of the guide rails 2 and 4. At least one of the mounts 6 and 8 allows the bar 10 to slide within it to facilitate this. This allows the bar to occupy orientations such as those in figures 2B and 2C, where the distance separating the mounts 6 and 8 is greater than in the position shown in figure 2A.

It is also possible for the bar 10 to be arranged to slide along its axis, i.e. to slide in both of mounts 6 and 8. An actuator could then translate bar 10 along the bar's own axis. This motion would either add to or replace the movement of each individual head 12,14,16 or 18 relative to the bar by actuators.

Clearly, the invention shown in figures 2B and 2C does not require the component holders 12,14,16, or 18 to have an active component rotating mechanism, such as a motor, on them. The component holders can therefore be lighter. In turn the bar 10, supports 6 and 8 and guide rails 2 and 4 can be of a fighter construction whilst providing the same rigidity. If the moving parts have lower mass then the moving system has lower inertia, allowing more rapid acceleration and deceleration. This in turn increases the throughput of the component placement apparatus and thus reduces the cost.

Furthermore, the sophisticated wiring which is required to supply a motor on the component holder in the prior art arrangement of figure 1 does not need to be provided in the apparatus according to the invention.

An additional advantage of the arrangement of figure 2 is the accuracy with which theta can be set. If a motor were provided on a component holder such as 14, the motor would need to be of very high quality to provide a precise orientation for a component which it held. The precision with which theta can be set with the arrangement of figure 2 depends on the precision with which mounts 6 and 8 can be positioned on their respective guide rails 2 and 4. In general terms, the precision with which mounts 6 and 8 can be located is extremely high. 10

The precision with which theta can be set also depends on the length of bar 10 and separation of guide rails 2 and 4. This follows from simple geometric considerations. To provide greater precision, the component placement apparatus can be designed with a longer bar 10 and more widely separated guide rails 2 and 4.

Figure 2D reproduces the view shown in figure 2A Figure 2D also includes two superposed dotted representations of the same bar 10 offset at an angle relative to the perpendicular line joining the guide rails. These dotted representations in figure 2D correspond to those shown in figures 2B and 2C.

The control means of the invention directs the various movements necessary to pick up and to place each component on the substrate. Preferably this control means consists of a microprocessor. A suitably programmed industriεd Pentium processor or PowerPC is adequate for this purpose.

Figure 3 shows a plan view of the main and peripheral elements of a component assembly machine in accordance with the invention. Figure 3 shows guide rails, mounts and two bars of the types already explained in connection with figure 2.

In figure 3, the feeder mechanism which supplies components to the component assembly machine has been shown. See the upper part of figure 3. This feeder mechanism brings a number of components simultaneously to the location of the component assembly machine. The feeder mechanism may run slightly below the working surface of the component assembly machine. The feeder trays would therefore pass under the working level of the component assembly machine when the components have been removed from them.

The component assembly machine includes a number of component extractors. Each component extractor serves to take a component out of the feeder mechanism and move it to a point and an orientation from which one of the component holders can collect it. These component extractors provide 1 1

centring of the component and set a coarse value for the 'theta' orientation of the component, prior to collection of the component by the component holder. The orientation provided by the component extractor can be relatively coarse because the invention allows a further, more precise setting of the component's orientation by the procedure explained above in connection with figure 2.

Figure 4 adds to the arrangement of figure 3 an additional pair of bars with multiple component holders. The provision of further bars and component holders further increases the rate at which components can be loaded onto substrates.

Although the additional bars shown in figure 4 are shown as being mounted on the same guide rails as shown in figure 3, this need not be the case. A further pair of guide rails could be provided. The bars 10 on one pair of guide rails 2, 4 should be able to move without contacting the bars on the other pair of guide rails. Clearly further guide rails and bars could be provided as required.

Figure 5 is a kinematic diagram. This illustrates more clearly the most basic principle of the invention, without the detail of figures 2-4. Although figure 5 is not necessarily a scale representation of a real machine, it is clear that angle theta can take on a wide range of values. The upper limit of the value of theta is mainly constrained by the lengths of the guide rails and bar which are practicable. Also, the precision to which theta can be set is partly determined by the separation between the guide rails and the length of the bar 10. The greater the separation between the guide rails and the greater the length of bar 10, the greater the precision with which theta can be set.

The description of figures 2B and 2C above made clear that at least one end of bar 10 must be able to slide within one of the mounts 6 and 8. Embodiments of the invention in which one end of bar 10 is fixed have been shown in figures 6- 8. 12

A detailed kinematic diagram is shown in figure 6. This diagram shows the right end of the bar mounted on a pivot. This pivot however prevents the bar from sliding along its length. The left end of the bar can also pivot relative to the guard rail which defines the X2 direction. It can however also slide through the mount which connects it to this guide rail. As the relative positions of the two mounts change, the angle theta changes. To accommodate these changes, the left end of the bar slides through its mount. Clearly, the bar pivots relative to both mounts as theta changes.

Figure 7 shows a similar arrangement to that shown in figure 3, but which functions as shown in principle in figure 6. Elements in figure 7 which correspond to those in figure 3 are not described again here.

The bars' mounts in figure 7 have been shown in the configuration explained above in connection with figure 6. The right end of each of the two bars shown can only pivot on its mount. The left end of each bar can however both pivot and slide within its mount. In the arrangement of figure 7, each of the four component holders on each bar can move along the bar. Thus when one or more component holders picks up a component from the feeder mechanism, the component holders move to the component extractor located above the feeder mechanism concerned. As the bar moves from the feeder mechanism to the location where substrates are fed through the component assembly machine, each component holder can slide along the bar on which it is mounted in order to prepare for placing its component on the substrate.

The exact sequence of component placement would be determined by the person skilled in the art and programmed into the microprocessor of the control unit. The basic parameters available to make this decision are the number of component feeders, the number of bars and the number of component holders on each bar. In the example of figure 7, there are a total of 18 component feed lines and two bars. There are four component holders on each bar, giving a total of eight component holders. 13

The skilled person would need to program the control means to drive the actuators of the arrangement of figure 7. These actuators are the mechanism by which the bars and component holders are driven to the correct locations and theta orientations to place components.

Figure 8 shows an arrangement of four bars. The arrangement of figure 8 corresponds largely to that of figure 4, but which functions as shown in principle in figure 6. However, the right ends of the bars are anchored to their mounts such that they can pivot but not slide through their mounts along their own axes. The left ends of the bars can both pivot on and slide through their mounts. Once again, the arrangement of figure 8 corresponds to the detailed kinematic diagram of figure 6.

The embodiments of the invention shown in figures 2-8 are not limiting, and the person skilled in the art would understand that other embodiments fall within the scope of the appended claims.

Claims

14Claims

1. A component placement apparatus comprising:

at least one component holder for placing a component on a substrate, the said component holder being mounted on a first linear support;

second and third linear supports, the said first linear support being mounted on the said second and third linear supports by first and second moveable mounts respectively;

the first and second moveable mounts being moveable along the second and third linear supports; and

control means for setting a variety of orientations of the component holder relative to the substrate by varying the locations of the said first and second moveable mounts on the said second and third linear supports.

2. The component placement apparatus of claim 1, the or each component holder further comprising an engagement member for engaging, holding and releasing components of various shapes and sizes.

3. The component placement apparatus of claim 1 or claim 2, further comprising the second and third linear supports having their axes lying substantially parallel.

4. The component placement apparatus of any previous claim, further comprising one or both of said first and second moveable mounts being movable along the second and third linear supports by means of actuators operated by the control means. 15

5. The component placement apparatus of any previous claim, further comprising the or each component holder being moveable along the first linear support by means of an actuator or actuators operated by the control means.

6. The component placement apparatus of any previous claim, further comprising the first linear support being connected to the first and second moveable mounts by first and second joints respectively, the first and second joints permitting the angle between the first linear support and the respective one of the second and third linear supports to vary.

7. The component placement apparatus of claim 6, wherein one of the said first and second joints holds the first linear support slideably and the other joint holds the first linear support without allowing sliding movement along the direction of the first linear support's axis.

8. The component placement apparatus of claim 6 or claim 7, further comprising:

a rigid bar constituting the said first linear support;

four component holders mounted on the said rigid bar;

a microprocessor constituting said control means; and

two electrical actuators, each of the actuators driving one of the said first and second moveable mounts independently of the other moveable mount, under the control of the said microprocessor.

9. The component placement apparatus of any of claims 1-6, further comprising at least one actuator which translates the first linear support in the direction of the first linear support's own axis. 1 6

10. The component placement apparatus of any previous claim, further comprising a fourth linear support, the said fourth linear support bearing further component holders and being mounted on the said second and third linear supports by third and fourth moveable mounts respectively.

11. The component placement apparatus of any previous claim, further comprising a further pair of linear supports serving as guide rails, onto which one or more further linear supports are mounted transversely on slideable mounts.