WO2000079295A1

WO2000079295A1 - Apparatus for testing electronic components accommodated in a carrier strip

Info

Publication number: WO2000079295A1
Application number: PCT/NL2000/000442
Authority: WO
Inventors: Johannes Nicolaas Peperkamp
Original assignee: Johannes Nicolaas Peperkamp
Priority date: 1999-06-23
Filing date: 2000-06-23
Publication date: 2000-12-28
Also published as: NL1012420C2

Abstract

Apparatus for testing one or more electronic components (2), particularly integrated circuits, which are accommodated in a carrier strip (1) and whose terminal pins (3) are electrically separated from one another, the apparatus at least comprising supporting means (6) for supporting the carrier strip (1), a test head (8) which has an essentially fixed position with respect to its surroundings and has one or more contacts (9) designed for electrically connecting terminal pins (3) of the one or more electronic components (2) to a tester and drive means for bringing at least terminal pins (3) of the electronic components (2) into contact with the test head (8), wherein the test head (8) comprises a printed circuit board (8), said printed circuit board (8) comprising the one or more contacts (9). An apparatus of this type has a very durable and yet simple and inexpensive test head.

Description

Short title: Apparatus for testing electronic components accommodated in a carrier strip

The present invention relates to an apparatus for testing one or more electronic components, particularly integrated circuits, which are accommodated in a carrier strip and whose terminal pins are electrically separated from one another, the apparatus at least comprising supporting means for supporting the carrier strip, a test head which has an essentially fixed position with respect to its surroundings and has one or more contacts designed for electrically connecting terminal pins of the one or more electronic components to a tester and drive means for bringing at least terminal pins of the electronic components into contact with the test head.

An apparatus of this type is known in the prior art. For example, GB-A-2 320 965 discloses a method and an apparatus for testing electronic components which are still accommodated in a leadframe. The test equipment disclosed in this document comprises a stationary test head with one or more auxiliary test heads on its underside. Each of these auxiliary test heads comprises a number of electrical contact pins which are aligned with the terminal pins of the electronic components to be tested. During a measurement, a leadframe with the components is pressed against the test head from underneath, the terminal pins coming into contact, in the process, with the contact pins of the auxiliary test head. In this case, the terminal pins are moved towards the test heads by the entire lead frame being displaced.

The known test heads have a number of important drawbacks. For example, their construction, involving the contact pins, is comparatively complicated and expensive. In addition, the contact pins are subject to wear due to the frequent contact being made with the terminal pins of the components. Moreover, the contact pins are subject to a slight bias by e.g. a spring, which may lead to problems of non- reproducible behaviour. As the terminal pins are relatively delicate parts, which moreover, for example, may bend, yet nevertheless must come into unambiguous contact with the contact pins, the risk of a defect or a malfunction during a test will become unacceptably large even after a relatively small number of tests. As early as that the test head must be replaced. It is an object of the present invention to overcome the abovementioned problems, the invention to this end being characterized in that the test head comprises a printed circuit board, said printed circuit board comprising the one or more contacts . The invention thus provides an apparatus for testing electronic components, which comprises a test head of a very simple, inexpensive and flexible design, enabling very frequent unambiguous and reproducible electrical contact to be ensured in a simple manner. Since no wear-prone, movable pins are required with the electrical contact itself, a test head of an apparatus according to the invention is able to survive up to 500,000 test cycles without any problems. Test heads of apparatuses according to the prior art are often replaced after about 100,000 to at most 200,000 test cycles. Moreover, the test head according to the invention can be replaced very quickly.

In this context reference is also made to US-A-5-008-615. This American patent discloses an apparatus for testing ICs in a leadframe. The apparatus comprises a membrane test head having a large number of contacts, a tester which is connected to the test head, and drive means for moving the test head towards and away from the terminal pins of the ICs to be tested. The membrane test head comprises a special, flexible PCB material such as UPILEX , which is relatively expensive. The drive means comprise an inflatable bladder which can be leakage- prone and moreover precludes the option of varying the pressure force for each terminal pin. Moreover, it is highly disadvantageous to move the test head, since the tester is consequently less reliable owing to moving leads and the like. Additionally, the number of test cycles will be considerably lower.

The design of the test head according to the invention is not particularly restricted. For example, it can be curved or even corrugated, as long as the terminal pins of the electronic components can be brought into contact with the contacts on the printed circuit board.

In particular, the printed circuit board is essentially planar. This ensures the simplest design possible by virtue of using standard PCB material.

If the terminal pins of the electronic components have not yet been formed, ie. still lie in the plane of the leadframe, it may be necessary to arrange recesses in the test head. These recesses should be aligned in such a way with the components to be tested that the components during the test can be accommodated at least partially in these recesses and contact becomes possible between the terminal pins and the contacts on the test head. Alternatively, the terminal pins can be bent, with the aid of press-on means shown schematically, from the plane of the leadframe against the contacts of the test head.

If, on the other hand, the terminal pins have already been formed, ie. being bent from the plane of the leadframe, the test head can comprise a continuous planar printed circuit board. The contacts can, for example, be in the form of small, electrically conducting bosses or "bumps" on the printed circuit board. Preferably, the one or more contacts are essentially planar. Thus the geometry of the contacts is very precisely defined, and because of the larger surface area is more resistant to wear. Planar contacts can be achieved, for example, with the aid of an etching technique. This involves processing a conductive printed circuit board in such a way, that the unwanted sections are etched away and the desired sections such as contacts and connector tracks remain behind. This technique is generally known in the prior art.

The material for the contacts can be selected from the materials known in the prior art. Of course, this material should be electrically conducting. Advantageously, the one or more contacts on the printed circuit board comprise nickel- diamond powder or a hard gold alloy. These materials ensure highly wear-resistant and corrosion-resistant contacts. Thus the apparatus according to the invention can function for longer periods without interruption, with less risk of malfunctions and defects . To achieve an electrical contact between the contacts and the terminal pins, it is in principle sufficient to establish a physical contact between these. It is therefore only necessary to move the terminal pins or the entire carrier strip in such a way that the terminal pins of the components come into contact with the contacts of the test head.

Advantageously, however, the apparatus further comprises press-on means which are aligned with the terminal pins of the electronic components to be tested, in order to press the terminal pins onto the one or more contacts. Thus, unequivocal electrical contact between terminal pins and contacts is ensured even more effectively. The press-on means can, for example, comprise a component which is able to press two or more terminal pins simultaneously against the associated contacts. Preferably, however, they are press-on pins which are aligned with the terminal pins of the electronic components to be tested.

In particular, the press-on means are coupled to a resilient element in order to be able to adjust the pressure force thereof. Electronic components are often fragile, and the terminal pins can easily break off or be damaged. It is therefore important to limit the maximum pressure force, particularly if terminal pins have not been formed quite in accordance with specifications. In particular, the apparatus forms part of an aligning apparatus for mechanically processing terminal pins of electronic components. Precisely because electronic components are fragile, they can still be damaged when terminal pins undergo mechanical processing. Indeed, it is advantageous for the electronic components to be tested after the terminal pins have undergone mechanical processing. Thus the risk of electronic components which have been tested and found acceptable yet being damaged during subsequent processing is greatly reduced. A specific embodiment of an apparatus according to the invention is characterized in that it further comprises bracing means which are able to support at least one of the electronic components to be tested. The bracing means serve to support an electronic component to be tested, eg. an IC, during the downward movement towards the test head. If a component is suspended in the leadframe in a skewed position, the bracing means ensure that the component will nevertheless readopt a correct position with respect to the test head. This is achieved as a result of that section of the component which first comes into contact with the bracing means experiencing the largest counteracting (elastic) force. As a result, an unsuitable position with respect to the test head is largely corrected. In many cases, the bracing means will therefore fulfill a positioning function.

Advantageously, the bracing means comprise one or more resilient bracing pins which extend through the printed circuit board. The bracing pins are able to be resilient, for example, by virtue of an elastic plate disposed thereunder. The spring force can be adjusted by a rigid backing plate of suitable thickness being disposed below the elastic plate. Thus it is possible for each of the bracing pins separately to act, with an adjustable spring force, on the components to be tested. In particular, the package of an IC can be aligned with respect to the printed circuit board. The printing circuit board in this case is provided with suitably aligned holes for the bracing pins .

The position adopted by the test head in the apparatus according to the invention with respect to the electronic components to be tested is not particularly restricted. For example, the test head can be located above or underneath the components or even next to them. Preferably, the test head is located underneath the electronic components to be tested. Thus an apparatus according to the invention can be employed in a simple manner in a standard so-called "trim and form" apparatus. With these trim and form apparatuses, use is often made of mould equipment with a stationary lower mould and a movable upper mould, the components to be processed being supported by the lower mould during the processing steps and being moved between the lower and upper mould in the periods during the processing steps .

The invention will be explained below in more detail with reference to the accompanying drawing, in which: Figure 1 shows a plan view of three integrated circuits in a leadframe;

Figure 2 shows a schematic sectional view of an apparatus according to the invention for testing electronic components;

Figure 3 shows a perspective view from below of an embodiment of the test head; and

Figure 4 shows a perspective exploded view of part of a lower mould of an apparatus according to the invention. In Figure 1, 1 indicates a mount for integrated circuits 2, a so-called leadframe. In the integrated circuits 2, the terminal pins 3 are electrically separated from one another, as indicated. The integrated circuits are each still connected to the leadframe 1 by four narrow connecting bridges 4. Also present in the leadframe 1 are alignment holes 5 which are used to bring the leadframe 1 in a suitable position and thus align the ICs 2 in an apparatus according to the invention.

Figure 2 shows an apparatus according to the invention. Here, 6 indicates a supporting arrangement which serves to support the leadframes 1. Present in said supporting arrangement

6 are positioning pins 7, intended to position the leadframe 1 and consequently the integrated circuit (s) 2.

8 denotes a test head which is stationary with respect to its surroundings and has contacts 9. The test head comprises a planar printed circuit board. Additionally, the terminal pins of the ICs have already been formed here. The contacts 9 are electrically connected, by means of continuous channels 10 through the test head 8, to electrically conducting tracks 11 which in turn can suitably be connected to a tester (not shown) . 12 indicates press-on pins which serve to press the terminal pins 3 of the ICs 2 against the contacts 9. The press- on pins 12 are connected to one another by means of a connector 13. The assembly of connector 13 and press-on pins 12 is pressed on by means of a resilient element 14 which, for example, can be in the form of a plastic part or a resiliently mounted part.

As can be seen in Figure 2, the terminal pins 3 of the ICs have already been suitably formed in accordance with the intended use thereof. Said forming and mechanical machining of the terminal pins is carried out in apparatuses suitable for this purpose, for example in so-called "Trim and Form" apparatuses. Preferably, said processing and the test procedure are effected in one and the same apparatus, the testing advantageously taking place after the mechanical processing of the terminal pins.

The use of the apparatus according to the invention firstly involves positioning a leadframe 1 with ICs 2 in the apparatus by aligning the alignment holes 5 by means of the pins 7. Thus the leadframe 1 is supported by the support arrangement 6. Then the press-on pins 12 are moved downwards by means of the resilient part 14 with the aid of drive means not shown in any detail, as a result of which the terminal pins 3 are unambiguously brought into electrical contact with the contacts 9. Then the integrated circuit 2 can be tested by a suitable tester which can be connected to the conductor tracks 11. It will be evident that any required number of ICs can be tested simultaneously, as can, of course, a single IC. In each case, a suitable number of test heads needs to be present. 15 indicates an end stop which serves to limit the movement of the assembly of supporting plate 13 and press-on pins 12. The presence of an adjusting plate 17 above the resilient part 14 advantageously enables the maximum pressure force to be adjusted, as terminal pins and electronic components are very delicate parts. Adjustment of the pressure force can be effected, for example, by a suitable choice of the thickness of the adjusting plate.

It will be evident that the press-on pins 12 are advantageously electrically insulated with respect to one another. To this end, the pins themselves can be made of electrically insulating material. Apart from pins it is equally possible, of course, to employ press-on strips or the like. 16 indicates a fixed supporting arrangement for the test head.

24 schematically indicates a set of bracing pins, and 25 schematically indicates a resilient plate. These two parts will be explained in more detail in conjunction with the description of Figure 4.

Figure 3 shows a drawing, in a perspective view from below, of a test head 8 suitable for use in an apparatus according to the invention. The test head 8 comprises channels 10 which are connected, via interconnection tracks 18, to contact points 19 which can be connected to the tester. 20 indicates suction ports to allow any contamination to be removed by suction with the aid of suitable extraction equipment. The test head 8 as shown in Figure 3 is suitable for testing 8 ICs simultaneously .

The test head 8 is preferably made from a sufficiently strong PCB material, for example FR4 or polyimide. The pads and conductor tracks are preferably an electroplated metal layer, for example a hard gold alloy on a chemically deposited base layer 10. To achieve even greater wear resistance, some other hard, conductive and corrosion-resistant material such as sintered nickel-diamond powder is suitable. The pads and tracks can be through-connected to a test system, possibly via connectors and optionally via an intermediate module in which electric circuits for reference values and/or electric switches and/or electric filters are located.

Figure 4 shows an exploded perspective view of part of a lower mould of an apparatus according to the invention. Here, 8 is a test head according to the invention which is fastened to the fixed mounting plate 16 by means of fastening means 21. It can be clearly seen that simple removal of fastening means 21 allows the test head 8 (printed circuit board) to be replaced, thus greatly shortening the down-time of the apparatus. The fixed supporting arrangement 16 can again be accommodated in a larger fixed base plate (not shown) .

12 again indicates press-on pins which, by means of suitable holes in part 23, can be aligned with the terminal pins of an electronic component to be tested. The press-on pins are able to be resilient by virtue of resilient elements 14. The spring force can be adjusted by a suitable choice of the thickness of plate 17.

22 indicates the electric connection parts which at one end make contact with the contact points 19, not visible here, of the test head 8 and at its other end make contact with a tester (not shown) . The contact points 19 are visible, on the other hand, in Figure 3. 24 indicates bracing pins designed to support an IC (not shown) . The bracing pins 24 are resiliently sprung by means of resilient plate 25. The spring force of the resilient plate 25 can be adjusted by means of shim 26. The bracing pins 24 serve to support an electronic component, for example an IC, as it moves downwards towards the lower mould half. If such an IC is suspended in a skewed position in a leadframe 1, part of the package of the IC would be first to come into contact with (some of) the bracing pins 24. As a result of said bracing pins 24 even then starting to exert a reaction force, the position of the IC 2 with respect to the test head 8 will be corrected. Thus, a correct position of the IC 2 during testing is ensured, and the terminal pins 3 on the IC 2 will all simultaneously, and with equal pressure, make contact with the pads 9 of the test head 8.

The reaction force of the bracing pins 24 must be adjustable as a function of the type of IC 2 and of the type of terminal pins 3. This can be achieved by a suitable choice of the thickness of shim 26. A thicker shim causes a greater reaction force to be exerted. Since correct positioning of the IC 2 and the terminal pins 3 is thus ensured, and the spring force exerted by the bracing pins 24 is accurately known, reliable electrical contact with high reproducibility of the contact resistance is ensured. This allows each IC 2 to be tested reliably.

Claims

C L A I M S

1. Apparatus for testing one or more electronic components (2) , particularly integrated circuits, which are accommodated in a carrier strip (1) and whose terminal pins (3) are electrically separated from one another, the apparatus at least comprising supporting means (6) for supporting the carrier strip (1), a test head (8) which has an essentially fixed position with respect to its surroundings and has one or more contacts (9) designed for electrically connecting terminal pins (3) of the one or more electronic components (2) to a tester and drive means for bringing at least terminal pins (3) of the electronic components (2) into contact with the test head (8), characterized in that the test head (8) comprises a printed circuit board (8), said printed circuit board (8) comprising the one or more contacts (9) .

2. Apparatus according to claim 1, characterized in that the printed circuit board (8) is essentially planar.

3. Apparatus according to claim 1 or 2, characterized in that the one or more contacts (9) are essentially planar.

4. Apparatus according to one or more of the preceding claims, characterized in that the one or more contacts (9) on the printed circuit board (8) comprise nickel-diamond powder or a hard gold alloy.

5. Apparatus according to one or more of the preceding claims, characterized in that it further comprises press-on means (12) which are aligned with the terminal pins (3) of the electronic components (2) to be tested, in order to press the terminal pins (3) onto the one or more contacts (9) .

6. Apparatus according to one or more of the preceding claims, characterized in that the press-on means (12) are coupled to a resilient element (14) in order to be able to adjust the pressure force thereof.

7. Apparatus according to one or more of the preceding claims, characterized in that the apparatus further comprises bracing means (24, 25, 26) which are able to support at least one of the electronic components to be tested.

8. Apparatus according to claim 7, characterized in the bracing means comprise one or more resilient bracing pins (24) which extend through the printed circuit board (8) .

9. Apparatus according to one or more of the preceding claims, characterized in that the apparatus forms part of an aligning apparatus for mechanically processing terminal pins (3) of electronic components (2) .