NL1004510C2 - Method for manufacturing a test adapter as well as test adapter and a method for testing printed circuit boards. - Google Patents

Description

Method for manufacturing a test adapter as well as test adapter and a method for testing printed circuit boards.

The invention relates to a method for manufacturing a test adapter, for electrically conducting coupling of measuring surfaces present in a test device with test surfaces present on a printed circuit board to be tested, which test adapter comprises a substrate with on one side first contact surfaces in a configuration corresponding to the measuring surfaces and on the other side second contact surfaces in a configuration corresponding to the test surfaces, in which electrically conductive paths are applied to and through contacts in the substrate with which the first and second contact surfaces are electrically connected to each other. Printed circuit boards are understood to mean all plates provided with electrically conductive strips, regardless of the manner in which these strips are formed and applied, not exclusively printed strips. Such test-15 adapters are used for measuring substrates with printed wires, so-called printed circuit boards. These printed circuit boards are used in almost all electrical appliances. Test surfaces should not only include special surfaces, for example on which components are placed, but also arbitrary places on the paths of the wiring. Due to the progressive miniaturization in the electronics industry, the printed circuit boards are getting smaller and the track densities of the electrically conductive tracks, which form the wirings, keep increasing. Before these printed circuit boards are used, they must first be measured, among other things, to check that there are no unwanted short-circuits between the strips or to check whether the applied strips have been interrupted. Test devices 25 exist for measuring circuit boards. These test devices are equipped with measuring surfaces that are coupled via a test adapter to the test surfaces on the printed circuit board to be tested. Since each circuit board with a different track pattern requires a separate test adapter and many different circuit boards are required in the electronics industry, many different test adapters are also required. Because the track densities and thus also the densities of the test surfaces on the printed circuit board are increasing, the test adapters can no longer be made at acceptable prices. Other test methods exist, but these are either too expensive or testing with these methods takes too much time to test J004510 2 economically. Failure to test at an acceptable cost is currently a major unresolved problem.

An object of the invention is to provide a method for manufacturing a test adapter of the type described in the preamble with which printed circuit boards with large densities and small dimensions of the test surfaces can be tested at an acceptable cost. To this end, the method according to the invention is characterized in that the electrically conductive strips are applied to the substrate by means of screen printing. With screen printing technique, very fine tracks with large track densities can be applied to a substrate in a relatively inexpensive manner. 10 Screen printing in itself is a known technique, but the application of this technique for the manufacture of test adapters is completely new and although the testing of printed circuit boards is a recognized and major problem, where solutions are feverishly sought, the solution is not rather be searched in this direction. Although it is not possible to suffice with the usual screen printing devices, it is obvious that special adjustments have to be made in order to make the existing screen printing techniques suitable for applying the very small webs and surfaces. In particular, these adjustments involve increasing the accuracy of the process steps, for example, by using optical alignment means to position the screens accurately relative to the substrate, and decreasing the tolerances of the screens used and refining the screen grids.

Because the densities of the test surfaces have increased sharply, the current through-contacting of substrates is no longer sufficient, because in diameter smaller through-contacting is required than can be obtained with the known techniques. To also provide a solution for this, an embodiment of the test adapter 25 according to the invention is characterized in that the through-contacts are formed by making holes in the substrate, after which a negative pressure is applied to a first side of the substrate and to the the other side of the substrate is exposed to electrically conductive material. Due to the underpressure, preferably a vacuum, the material is sucked through the very narrow holes in order to fill the holes and obtain the through-contacts. The application of the electrically conductive material in the holes hereby can also be effected by screen printing.

Preferably, the insertion and suction of the electrically conductive material 1004510 3 takes place in the holes such that protuberances of the electrically conductive material are formed on the first side of the substrate at the location of the holes. These protuberances can then function as contact points for making contact with the test surfaces on the printed circuit board to be tested or with the measuring surfaces of the test device.

5 With even greater densities of the test surfaces on the printed circuit boards to be measured, the positioning of the screens must be done so precisely that this requires highly advanced techniques. This greatly increases the costs of manufacturing the test adapters. At very large densities it may even occur that there is insufficient space between the contact surfaces to provide the contact surfaces with 10 connecting tracks. An embodiment of the method according to the invention with which these costs can be limited and with which contact surfaces with very high densities can also be provided with connecting tracks, is characterized in that the electrically conductive paths are applied in several layers one above the other, before applying a next layer an insulating layer 15 is applied to the previous layer, which is contacted in a number of places. By distributing the web pattern over different layers, it is possible to provide it with connecting tracks even at very high densities of the contact surfaces.

An advantageous embodiment for shielding the web pattern is characterized in that a further substrate provided with 20 further contacts is applied to the electrically conductive webs. Another favorable embodiment of this is characterized in that the electrically conductive paths are covered with an electric insulating layer which is contacted at the location of the contact surfaces. In order to obtain good contact possibilities with the printed circuit board or test device, in this latter embodiment, preferably, elevations of the electrically conductive material are formed at the through-contacted places in the insulating layer.

The invention also relates to a test adapter for electrically conducting coupling of measuring surfaces present in a test device with test surfaces present on a printed circuit board to be tested, comprising a substrate with first contact surfaces on one side in a configuration corresponding to the measuring surfaces and on the other side, second contact surfaces in a configuration corresponding to the test surfaces, wherein the first and second contact surfaces are electrically connected to each other via electrically conductive paths and through contacts.

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In order to be able to test printed circuit boards with very high track densities, the test adapter according to the invention is characterized in that the electrically conductive tracks are present in several layers one above the other with contacted insulating layers in between. By distributing the electrically conductive paths which form the connection tracks for the contact surfaces over different layers, contact surfaces with higher densities can be provided with connection tracks. Laying the electrically conductive paths in different layers is new with test adapters. This seemingly obvious solution has not been obvious since test adapter manufacturers have never come up with this solution despite the urgent need for test adapters with greater contact patch densities. Partly due to the new method of manufacturing test adapters described above, it has become possible to apply the web patterns in multiple layers at an acceptable cost.

An advantageous embodiment of the test adapter, in which the track pattern is well shielded, is characterized in that the substrate is built up of two plate parts between which the guide tracks are located. Another favorable embodiment of this is characterized in that the conducting tracks are covered with an electrical insulating layer contacted at the location of the contact surfaces. In order to obtain good contact possibilities with the printed circuit board or test device, a further embodiment of the latter test adapter is characterized in that elevations of the electrically conductive material are present at the 20 contacted places in the electrical insulation layer. Yet a further embodiment with which good contactings can be obtained is characterized in that protrusions of the electrically conductive material are present at the contacted places in the substrate.

The invention furthermore relates to a method for testing printed circuit boards, in which a printed circuit board to be tested provided with test surfaces is placed between two parts of a test device provided with measuring surfaces, wherein at least one test is placed between the printed circuit board and the test device adapter provided with contact surfaces for electrically coupling the test surfaces to the measuring surfaces, after which the two parts of the test device are brought together and the contact surfaces come into contact with the test and measuring surfaces. In the known methods for testing printed circuit boards, for the purpose of making contact between the contact surfaces of the test adapters and the measuring surfaces of the printed circuit board, resilient elements are used, which are usually arranged on or under the contact surfaces, such as electrically conductive springs on the contact surfaces or contact surfaces on elastic foil, with a recess in the substrate under the contact surfaces. These resilient elements complicate the construction of the test adapter and, in terms of miniaturization, cannot keep pace with the progressive miniaturization of the printed circuit boards under test. This miniaturization of the test surfaces, and therefore also the required reduction in the dimensions of the contact surfaces of the test adapters, leads to considerable and as yet unsolved problems in the construction of these resilient elements.

A further object of the invention is to provide a method for testing printed circuit boards of the type described above, wherein proper contacting between the test adapter and the printed circuit board to be tested is obtained. To this end, the method for testing printed circuit boards according to the invention is characterized in that a uniform pressure is exerted on the test adapter and is thereby elastically deformed, whereby the contact surfaces of the test adapter are brought into contact with the test surfaces of the test adapter. testing circuit board. By making use of the elastic (substantially compressible) properties of the test adapter, the so-called stamping effect, no additional resilient elements are required, so that the problems with regard to the miniaturization of the resilient elements do not arise either. This is a completely new approach to circuit board testing, previously using resilient elements. Sufficient existing conventional materials for test adapters will suffice. These already have sufficient elasticity.

An embodiment of the method for testing printed circuit boards according to the invention is characterized in that a printing plate is arranged between the test device and the test adapter via which the pressure is uniformly transferred. This ensures a uniform contact pressure, which ensures that all contact surfaces also make contact with the test surfaces.

In order to ensure that a sufficient contact pressure is present, a further embodiment is characterized in that the pressure with which the test adapter is pressed against the printed circuit board to be tested is measured by at least one pressure sensor.

The invention will be explained in more detail below with reference to illustrative embodiments of the test adapter according to the invention shown in the drawings.

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Hereby shows:

Figure 1 shows a schematic representation of a test device with adapters, printing plates and a printed circuit board to be tested;

Figure 2 shows a cross-section of a first embodiment of a test adapter 5 according to the invention;

Figure 3 shows a cross-section of a second embodiment of a test adapter according to the invention;

Figure 4 shows a step in the method according to the invention in which electrically conductive material is placed in holes in the substrate of the test adapter; Figure 5 shows a top view of a screen for applying a layer of the web pattern of the test adapter; and

Figure 6 shows a further step in the method according to the invention in which elevations are applied to the contacted places.

Figure 1 shows a test setup for testing printed circuit boards. The test arrangement comprises a test device 1 provided with measuring surfaces 3. The printed circuit board 5 to be tested in this example is a printed circuit board printed on both sides with test surfaces 7 on each side. The test surfaces 7 have a different configuration than that of the measuring surfaces 3 and have a much greater density than the measuring surfaces. A test adapter 9 is provided between each side of the printed circuit board 20 5 and the test device 1 for coupling the test surfaces 7 to the measuring surfaces 3. The test adapter 9 consists of a substrate 11 with first contact surfaces 13 on one side. in a configuration corresponding to the measuring surfaces 3 and on the other side second contact surfaces 15 in a configuration corresponding to the test surfaces 7. The first and second contact surfaces are electrically connected to each other by electrically conductive paths 17. Between test adapters 9 and test 25 device 1 there are units 19 with resilient compensation pins 21, which electrically couple the first contact surfaces 13 to the measuring surfaces 3 and absorb any height differences. These units 19 are usually required to bridge the distance between the two parts of existing test devices 1 and the test adapters 9. These units may be omitted if new test devices are used which are specially designed for these new test methods. For testing, the two parts of the test device 1 shown are brought together, the test adapters 9 being pressed against the test surfaces 7 with their second contact surfaces 15. The contact pressure must be 1004510 7 sufficiently large and uniform to ensure that all test surfaces 7 make contact with the second contact surfaces 15. This is achieved by passing between test adapters 9 and units 19 or, in the absence of the units, the test device 1 arranges printing plates 20. These printing plates 20 must be very rigid and for this purpose are made of, for example, solid aluminum. The test adapters 9 are elastically deformed by pressing, so that the contact surfaces 15 are pressed against the test surfaces 7. To ensure that a sufficiently large pressure is applied, the pressure between the test adapters 9 and the printed circuit boards 5 to be measured is measured by means of pressure sensors 22.

Figure 2 shows a cross-section of a first embodiment of the test adapter 9 according to the invention. The substrate 11 of the test adapter 9 is composed of two plate parts 23, 25 between which the guide tracks 17 are located. On one side of the substrate, the first contact surfaces 13 are in a configuration corresponding to the measuring surfaces 3. On the other side, the second contact surfaces 15 are in a configuration corresponding to the test surfaces 7. The plate parts 23, 25 are contacted through. These through-contacts 27, 29 are formed by electrically conductive material present in holes 31, 33, with protrusions 35,37 on the outer sides of the substrate 11. The electrically conductive paths 17 are arranged in several layers 39 one above the other. The spaces 41 between the sheets 17 in a layer are filled with an insulating material. Insulating layers 41 are provided between these layers 39 and are provided at a number of places with through-contacts 43. The top plate part 25 can optionally also be omitted. Instead, it is preferable to provide elevations at the through-contacted locations of the upper insulating layer in order to improve contact with the measuring surfaces.

Figure 3 shows a cross-section of a second embodiment of the test adapter according to the invention. With this test adapter 45, the electrically conductive paths 47 are all in one layer 49 on the substrate 51. Between the paths 47 there is insulating material 53. The layer 49 is covered with an electrical insulating layer 55. At the location of the contact surfaces 57 this insulating layer 55 is contacted. Elevations 59 of the electrically conductive material 30 are provided at the through-contacted locations. These elevations 59 form the second contact surfaces 57.

Figure 4 shows a step in the manufacturing process of the first embodiment of the test adapter shown in Figure 2. Prior to this, 8 holes 31 have been made in the substrate 11 1004510. These can be made by mechanical drilling or with a laser or water jet. The space 61 under the substrate 11 is evacuated. Then a screen 63 is applied to the substrate 11 with only openings 65 at the locations of the holes 31. With an rubber strip 67, an electrically conductive paste 69 is then passed through the openings 65 in the holes 31. As a paste, for example, a paste with a conductive polymer or a silver paste can be used. Due to the vacuum present at the bottom, the paste 69 is drawn into the holes 31, which improves the filling of the holes. During this process, protuberances 35 of the conductive material as shown in Figure 2 are formed on the underside of the substrate.

After this, the electrically conductive strips are applied to the substrate in one or more layers by means of screen printing. This is described with reference to Figures 5 and 6. In this process step, a second layer of electrically conductive strips is applied after a first layer 71 and an insulating layer 73 have already been applied to the substrate 11 before this. The web pattern and the places to be contacted are arranged as openings 15 75 in a screen 77, see figure 5. The screen 77 consists of a grid of very fine wires 79 on which a cover layer 81 is applied. In figure 6, this screen 77 is positioned on the already present layers 71 and 73 on the substrate 11. This positioning has to be done very accurately and is therefore preferably done in an automated mechanical manner. Then, with a rubber strip 83, electrically conductive material 85 is pasted into the openings 75 in paste form. It may be desirable to have this take place in a number of strokes. This ironing, too, should preferably be carried out automatically in a mechanical manner. After this, with a further screen, which only covers the just-formed webs and through-contact points, the space between these webs and through-contact places is filled with insulating material, again preferably by screen printing. Known materials can be used for the electrically conductive paste in the printed circuit board and screen printing technology. The same goes for the insulation materials.

Although the invention has been elucidated with reference to the drawings in the foregoing, it should be noted that the invention is by no means limited to the embodiments shown in the drawings. The invention also extends to all embodiments deviating from the embodiments shown in the drawings within the scope defined by the claims. For example, the test adapter 1004510 9 can of course also be used in test devices for testing printed circuit boards printed on one side. Also, the method for testing printed circuit boards with test adapters other than the test adapter according to the invention can be carried out as long as use is made of the so-called stamping effect in which the contact is effected by elastic deformation and not by resilient elements.

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Claims (15)

1. Method for manufacturing a test adapter, for electrically conductive coupling of measuring surfaces present in a test device with test surfaces present on a printed circuit board to be tested, which test adapter comprises a substrate with first contact surfaces on one side in a configuration corresponding to the measuring surfaces and on the other side second contact surfaces in a configuration corresponding to the test surfaces, in which electrically conductive paths are applied to and through contacts in the substrate with which the first and second contact surfaces are electrically connected to each other, characterized in that the electrically conductive paths are applied to the substrate 10 by screen printing. Method according to claim 1, characterized in that the through-contacting is formed by making holes in the substrate, after which a negative pressure is applied on a first side of the substrate and electrically conducting material in the holes on the other side of the substrate. is brought. Method according to claim 2, characterized in that, during the introduction of the electrically conductive material, protuberances of the electrically conductive material are formed on the first side of the substrate at the location of the holes. Method according to claim 1, 2 or 3, characterized in that the electrically conductive strips are applied in several layers one above the other, whereby before the next layer is applied, an insulating layer is applied to the previous layer, which layer is applied to a number of places is contacted. Method according to claim 1, 2, 3 or 4, characterized in that a further substrate provided with through-contacting is applied to the electrically conductive paths. Method according to claim 1, 2, 3 or 4, characterized in that the electrically conductive strips are covered with an electric insulating layer which is contacted at the contact surfaces. Method according to claim 6, characterized in that elevations of the electrically conductive material are formed at the through-contacted places in the insulating layer. Test adapter, for electrically conductive coupling of measuring surfaces present in a test device with test surfaces present on a printed circuit board to be tested, 1004510 comprising a substrate with first contact surfaces on one side in a configuration corresponding to the measuring surfaces and on the other side second contact surfaces in a configuration corresponding to the test surfaces, wherein the first and second contact surfaces are electrically connected to each other via electrically conductive paths and through-contacts, characterized in that the electrically conductive paths are present in different layers one above the other, with insulating layers contacted between them. Test adapter according to claim 8, characterized in that the substrate is made up of two plate parts between which the conducting tracks are located. Test adapter according to claim 8, characterized in that the conducting tracks 10 are covered with an electrical insulating layer contacted at the contact surfaces. Test adapter according to claim 10, characterized in that elevations of the electrically conductive material are present at the through-contacted locations in the electrical insulation layer. Test adapter according to claim 8, 9, 10 or 11, characterized in that protrusions of the electrically conductive material are present at the contacted places in the substrate. 13. Method for testing printed circuit boards, wherein a printed circuit board provided with test surfaces is placed between two parts of a test device provided with measuring surfaces, wherein at least one test adapter provided with contact surfaces between the printed circuit board and the test device for electrically coupling the test surfaces to the measuring surfaces, after which the two parts of the test device are brought together and the contact surfaces come into contact with the test and measuring surfaces, characterized in that on the test adapter a uniform pressure is applied and thereby elastically deformed, whereby the contact surfaces of the test adapter are brought into contact with the test surfaces of the printed circuit board to be tested. Method according to claim 13, characterized in that a pressure plate is applied between the test device and the test adapter, via which the pressure is uniformly transferred. Method according to claim 13 or 14, characterized in that the pressure with which the test adapter is pressed against the printed circuit board to be tested is measured by at least one pressure sensor. 1004510