DE102011056371B4 - Device for checking conductor structures - Google Patents

Abstract

Device (1) for testing a conductor structure, the device (1) having a plurality of measuring points (2) on a first side (3) and the device (1) having an electrically conductive material (5 ), which is in electrically conductive connection with the plurality of measurement points (2), characterized in that the electrically conductive material (5) forms an electrically conductive connection of the plurality of measurement points (2) with one another.

Description

The invention relates to a device for testing a conductor structure for interruptions or short circuits. In particular, the invention relates to a device for checking printed circuit boards and cables.

Printed circuit boards, for example, are checked for manufacturing control by means of a "continuity test" for faulty and missing connections. In this case, the conductor tracks of the circuit boards are tested against each other at least two different points of one or two different tracks via a resistance measurement.

The common testing machines can be divided into the group of "in-circuit testers" and the group of "flying probers". The "flying probes", also called finger probes, have two or more individual test fingers, which scan the circuit boards step by step. The advantage of this variant is that to test different circuit boards, the tester does not have to be mechanically adapted to the particular circuit board to be tested. Thus, smaller series can be tested inexpensively. However, this type of testing machine requires long testing times, which is the major drawback of the flying probers. The "in-circuit testers", also called parallel testers, use adapters equipped with spring pins or fine so-called rigid needle adapters, which are able to check all test points of the printed circuit board at once. As a result, significantly less time is required to test the entire circuit board compared to the flying probes. The main disadvantage of this type of test, however, lies in the high cost of the required adapter.

The DE 10 2009 004 555 A1 discloses an apparatus for testing printed circuit boards, the test arrangement having test contact elements in a predetermined regular grid. In addition, the device requires no special adaptation to the particular type of printed circuit board to be tested.

Although the illustrated test device allows faster measurements compared to the finger tester, however, it requires a multiple displacement of the test arrangement for contacting all the test points located on the respective printed circuit board, whereby several test passes are necessary in comparison to the parallel testers. Furthermore, a high needle density, as the tester described has generally error-prone in use and costly to manufacture.

The US 4 571 542 A shows a method and apparatus for inspecting printed circuit boards using a pressure-sensitive, electrically conductive, elastic plate. The plate has no electrical conductivity in an undeformed state. The plate becomes electrically conductive in the thickness direction only when it is compressed in this direction. For this purpose, the elastic plate is pressed at areas by test electrodes, which are opposite to electrically conductive areas of the circuit board. In this way, the plate becomes selectively electrically conductive in the thickness direction, so that an electrical connection is made from the test electrode via the indented region of the plate to a region to be tested on the printed circuit board.

The US 2005 146 336 A1 shows an electrical resistance measuring connector, an electrical resistance measuring apparatus for printed circuit boards, and a method of measuring electrical resistance. In this case, the connecting element is arranged on a Leiteplatte to be tested. Furthermore, the connecting element comprises electrode pairs, which are brought via an anisotropically conductive plate with the electrodes of the circuit board to be tested in combination.

It is therefore an object of the invention to enable a rapid measurement of the electrical connections of the printed conductors on a conductor structure even without specially adapted adapters. It is further desirable that the susceptibility to errors is minimized and the manufacturing costs are reduced.

This object is achieved by a device according to independent claim 1 and a system according to independent claim 10. Advantageous developments of the device can be found in the respective dependent claims.

A device according to the invention has, for testing a conductor structure on a first side, a multiplicity of measuring points and, on a second side, an electrically conductive material which is in electrically conductive connection with the multiplicity of measuring points. The electrically conductive material forms an electrically conductive connection of the plurality of measuring points with one another. In this case, the measuring points can be arranged arbitrarily or at defined intervals, for example grid-shaped. With the device according to the invention, conductor structures can be checked for faulty or missing contacts of the respective printed conductors. In this case, the electrically conductive material of the second side of the test apparatus is brought into contact with the conductor structure to be checked, so that the electrically conductive material of the second side preferably completely touches the corresponding surface of a conductor pattern.

The surface of a conductor structure to be tested is usually provided with a solder resist, which serves to ensure that the solder remains clean on the intended surfaces during soldering and that tin does not settle between adjacent conductor tracks. The end points of the interconnects are excluded from the solder resist and thus form the electrical contacts of the conductor structure, which are contacted by the tester. If the surface of the conductor structure to be tested is not provided with solder mask, the test apparatus contacts the conductor structure optionally over its entire length.

Without contact of the test apparatus to a conductor structure, the electrically conductive material determines the electrical resistance between two measuring points. The contact between the end points of a conductor track and the electrically conductive material influences the electrical resistance between two measuring points. The resulting by the contact with a conductor structure electrical resistances between the respective measuring points result in their overall view, a specific image of the circuit board to be tested. By comparing this image with a corresponding desired image, which can be determined, for example, by calculation, "short circuits, interruptions or faulty conductivity of the corresponding conductor tracks of the conductor structure can then be detected.

In comparison to known test devices, this requires fewer test operations in order to successfully check all relevant electrical connections of the conductor tracks. As a result, faster measurements are possible overall.

Another advantage of using a layer of electrically conductive material is that it does not require accurate positioning of the device under test. The measurement image of a resistance measurement is compared with a target image. A resulting possible offset between measured and target image can be computationally compensated.

In a preferred embodiment, the electrically conductive material is completely or almost completely in contact with the surface of the conductor structure to be tested, whereby a complete or almost complete testing of the conductor structure is possible.

A device according to the invention preferably has a measuring device which is connected to the electrically conductive material via the measuring points. The measuring points can be connected via cables to the measuring device. Alternatively, the measuring device can also be mounted directly on the first side of the device. In this case, the measuring points are part of the measuring device. The number of measuring points depends on the required measuring accuracy or on the test specimens to be measured. Preferably, the distance between the measuring points on the first side is 0.5 mm; 1 mm; 2 mm; 3 mm; 4 mm or 5 mm or any other suitable value, whereby a density of up to 400 measuring points per cm ^{2 is} achieved. The individual measuring points are then connected to the measuring device via one or more multiplexers, so that each measuring point can be selected individually. The measuring device can perform individual measurements or several measurements simultaneously.

In a further preferred embodiment, the device consists of at least two layers, the first layer being a plate, the plate having measuring points on a first side and having contact points on a second side, which points of contact with the second layer comprising the conductive material be in electrically conductive connection. In this case, the second side of the first layer adjoins the second layer either directly or via one or more connecting layers.

In a preferred embodiment, the first layer is a rigid plate which imparts rigidity to the entire device. In a further embodiment, the first layer is a flexible plate so that the test device as a whole achieves a desired stiffness while still remaining flexible. For this purpose, the first layer is preferably stiffer than the second layer.

The measuring points of the first side of the first layer are connected in a preferred embodiment by means of through-contacting with the second side and thus with the second layer, consisting of conductive material. As a result, the conductive material forms an electrically conductive connection between the measuring points, which is influenced by the conductor tracks of the conductor structure. The plated-through hole can preferably be realized by an internally metallized bore in the first layer. If the measuring points are part of the measuring device, the measuring device is integrated in the first layer of the device or sits on it.

In a further preferred embodiment, the measuring points are connected via needles to the electrically conductive material. In this case, a first end of the needles represents the measuring points, which are connected to a measuring device. The needles are held in position by the first layer to each other. They pass through the first layer and penetrate into the second layer, the electrically conductive material. The second layer penetrating part of the needles thus represents the contact points of the first layer.

In a preferred embodiment, the first layer can be connected to the second layer in a form-fitting manner, for example by screwing.

In a further preferred embodiment, the first layer may be materially bonded to the second layer. In this case, the second side of the first layer is connected by electrically Zeitfähigen adhesive with the second layer. Preferably, the electrically conductive adhesive has an electrical conductivity which is equal to or similar to the conductivity of the second layer. Alternatively, the adhesive may not be electrically conductive. It must be ensured that an electrically conductive connection between the measuring points and the second layer is given, so that the contact points of the first layer are not covered by the adhesive. Alternatively or additionally, the second layer can also be melted onto the second side of the first layer.

In a further preferred embodiment, the first layer can also be positively connected to the second layer. In this case, the two layers are just on top of each other. In this case, the second layer is held, for example, by a guide on the first layer in the edge region. If the test device comes into contact with a conductor structure, a frictional connection between the first and the second layer as well as the second layer and the conductor structure is produced by a contact force which presses the two layers in the direction of the conductor structure. This frictional connection ensures the electrically conductive connection between the measuring points via the electrically conductive material or via the conductor tracks of the conductor structure.

In a preferred embodiment, the electrically conductive material is foam with graphite inclusions such as carbonaceous polyurethane foam. Alternatively, the electrically conductive material may also be made of electrically conductive rubber. This graphite and / or soot particles give the rubber its electrical conductivity. Furthermore, the layer of electrically conductive material can also consist of silicone with conductive inclusions (such as, for example, silver and copper or nickel graphite, for example under the name "Conductive Rubber 5750" by Holland Shielding Systems). In addition, the electrically conductive material may also consist of a layer of electrically conductive paint (for example, under the name of Charles Water ^® -71 016, available from Farnell) which is applied directly to the first layer.

It follows, inter alia, that the second layer of the test apparatus and thus the electrically conductive material is in contact with the entire or almost the entire surface of the conductor structure to be tested.

In a preferred embodiment, the electrically conductive material has a resistivity greater than about 0.0001 Ωm, more preferably greater than about 0.01 Ωm. More preferably, a resistivity is in a range of about 0.0001 to about 70 Ωm. Particularly preferred is a resistivity in a range of about 0.001 Ωm to about 50 Ωm. Also particularly preferred are resistivities in the ranges of about 0.002 Ωm to about 40 Ωm or even about 0.01 Ωm to about 30 Ωm. The resistivity may vary depending on the type of material used. The resistivity of the electrically conductive material should be significantly higher (at least 1, better 2, 4, 6 or 8 orders of magnitude) than that of the material used for the conductor structure to be tested (such as copper).

In a preferred embodiment, the electrical resistance between two measurement points located about 1 cm apart on the first side of the test apparatus is between about 10 Ω and about 1000 Ω, more preferably between about 10 Ω and about 100 Ω if the test apparatus is not is in contact with a conductor structure to be tested. Thus, the resistance to be measured is also over the length of a conventional circuit board (about 40 cm) in an area that can be measured easily and inexpensively.

The thickness of the electrically conductive material may be chosen so that for a given material with a certain resistivity, the resistance between two measurement points (without contact with a conductor structure to be tested) reaches approximately a desired value.

When using certain electrically conductive foams their specific resistance can be adjusted via the contact pressure. The actual resistance can then be determined by a reference measurement in the edge region or via a measurement in which there is no contact with a conductor structure.

In preferred embodiments, is as an electrically conductive material, the conductive intermediate layer of ESD mats (for example, from 3M ^® or Multicomp ^® or Vermason ^®) or Vermason ^® under the name "Vermafoam Conductive Polyurethane Foam" or Rubena ^® under the Designation "Rubber MA 519" (graphite and carbon black rubber) or "Conductive rubber 5750" by Holland Shielding Systems (rubber with silver, nickel, silver-plated glass, silver-plated aluminum or graphite).

In a preferred embodiment, the electrically conductive material is a mat consisting of one of the materials listed above.

In a preferred embodiment, the electrically conductive material is compressible (preferably elastically compressible). For example, the compressibility of the material is such that the material at a contact pressure of 0.1 N / cm ² and a thickness of z. B. 2 mm in thickness by 0.2-0.5 mm compress. As a result, the electrically conductive material has a flexibility which makes it possible to touch the surface of planar as well as uneven conductor structures and thus to influence the electrically conductive connection between the measuring points via the electrically conductive material through the corresponding conductor tracks of a conductor structure. By a contact force, the flexible electrically conductive material is deformed such that it comes into contact with all or almost all traces. In this way, even unevenness, which can be caused by deformation or by the use of solder resist on the circuit boards, can be compensated. In addition, bumps that can occur due to contamination can be overcome. If the test device is released from the conductor structure to be tested, the flexible electrically conductive material resumes its original shape. Accordingly, in a subsequent measuring operation, a conductor structure having a different surface finish can be tested, without the measuring device having to be specially adapted to the new conductor structure. The test device can thus be used independently of the surface condition of the conductor structure to be tested.

The electrically conductive material may be divided into a plurality of electrically isolated zones. As a result, for example, a plurality of conductor structures, which are each contacted by a zone of the electrically conductive material, can be tested at once.

Conductor structures that can also be checked with a test device according to the invention are also wires of cables or lines used as electrical conductors. These can also be checked according to the invention for short circuits, interruptions or faulty conductivity. The connectors, which are located at the cable ends, brought into contact with the electrically conductive material. This can be done by pressing the connectors to the electrically conductive material. The male part of a plug connection can preferably be pressed directly onto the electrically conductive material, while adapters for guiding out the contacts can be used for the contact openings of the female part.

In this case, no fixed position must be maintained for the position of the connectors on the electrically conductive material, but it can be mathematically compensated for shifts relative to a reference position.

The invention further relates to a system for testing a conductor structure, which is composed of two devices according to the invention. In this case, the devices are arranged relative to one another in such a way that the second layer of the first device faces the second layer of the second device. The conductor structure to be tested is arranged between the second layer of the first device and the second layer of the second device. The distance between the two opposing parts is reduced until the second layers of the first and the second part touch the conductor structure to be tested. In this case, an upper side of the conductor structure with the second layer of the first part and a lower side of the conductor structure with the second layer of the second part are brought into a frictional connection. This frictional connection ensures the electrically conductive connection between the measuring points of the first and second part of the test apparatus via the electrically conductive material and the corresponding conductor tracks on the first or second side of the conductor structure.

In a preferred embodiment, in a system as described above, in the event that printed conductors extend from the upper side of the conductor structure, for example by means of plated-through, to the underside of the conductor structure (plated-through printed circuit boards), the measuring points of the first part of the testing device can also be counteracted the measuring points of the second part are measured. With reference to the drawings, the invention will be explained in detail below. It shows:

1 Schematic structure of a first embodiment of a one-sided inspection device according to the invention;

2 Schematic structure of a second embodiment of a one-sided inspection device according to the invention;

3 Schematic structure of an embodiment of a test system according to the invention (two-sided tester);

4 Schematic structure of the first embodiment of a one-sided test device according to the invention for testing an electrical cable.

From the illustration according to 1 is the construction of a first embodiment of the test apparatus 1 for schematically measuring one-sided measurement of a conductor structure. The tester 1 has a plate 7 on, on the first page 3 a housing 10 is appropriate. Inside the case 10 and on the first page 3 the plate 7 there is a measuring device 6 , which with measuring points 2 on the first page 3 the plate 7 via a multiplexer 13 in contact.

The measuring points 2 are on the plate 7 arranged in a grid pattern. The distance between the measuring points is 0.5 mm. Next are the measuring points 2 from the first page 3 on the second page 4 the plate 7 plated through. Through the via 9 creates an electrically conductive connection between the measuring points 2 the first page 3 the plate 7 and contact points 11 on the second page 4 the plate 7 ,

The second page 4 the plate 7 is over an electrically conductive adhesive 8th cohesively with an electrically conductive mat 5 made of foam with graphite inclusions. The measuring points 2 stand with the electrically conductive mat 5 via the via 9 , the contact points 11 and the electrically conductive adhesive 8th in electrically conductive connection.

In addition, the electrically conductive mat 5 an elastic behavior on. Due to the elastic properties of the electrically conductive mat 5 adapts to both flat and uneven PCB to be checked. For this purpose, the test device is pressed onto a printed circuit board. Will the electrically conductive mat 5 then detached from the circuit board, it returns to its original shape.

The electrically conductive mat 5 has a resistivity of 40 Ωm. The resistivity of the electrically conductive mat 5 sets an initial resistance value between the measuring points 2 stuck together. Comes the electrically conductive mat 5 In contact with a conductor structure to be tested in the course of a resistance measurement, this influences the resistances between the measuring points 2 among themselves.

2 schematically shows the structure of a second embodiment of a tester 1 for one-sided measurement of a conductor structure. The tester 1 has a plate 7 on, which consists of an insulating material. The device 1 points further needles 29 on which perpendicular in the plate 7 stuck. The needles 29 stand out on the second page 4 the plate 7 out.

The ends of the needles 29 , form on the first page 3 the plate 7 the measuring points 2 , At these measuring points is a multiplexer 13 connected, which via a connecting cable 12 with the measuring device 6 connected is. Alternatively, the measuring device 6 , as in 1 shown, also directly with the measuring points 2 communicate and immediately on the first page 3 the plate 7 be arranged. Also the arrangement chosen here of a multiplexer, which on the measuring points 2 sits and over a connecting cable 12 with the measuring device 6 can be connected in the in 1 shown device 1 be used.

To the plate 7 borders a layer consisting of electrically conductive material 5 , This layer 5 is on the second page 4 the plate 7 melted and thereby forms with her a cohesive connection.

The parts of the needles 29 , which on the second page 4 the plate 7 protrude, forming the contact points 11 , These are stuck in the layer of electrically conductive material 5 , creating an electrically conductive connection between the needles 9 with each other via the electrically conductive material 5 consists.

3 schematically shows the structure of a third embodiment of a system for double-sided testing a printed circuit board. There are two devices 1 . 1b for one-sided testing of a conductor structure. The first device 1 has a measuring device 6 on which via a multiplexer 13 with contact points 11 connected is. The measuring device 6 and the multiplexer are from a housing 10 surrounded, which on the first page 3 the plate 7 is appropriate.

The measuring points 2 are on the plate 7 arranged in a grid pattern. The distance between the measuring points is 0.5 mm. The measuring points 2 on the first page of the plate 7 each form a via 9 an electrically conductive connection with the contact points on the second side 4 the plate 7 ,

On the second page 4 the plate 7 is an electrically conductive material 5 melted. The connection between the electrically conductive material 5 and the second page 4 the plate 7 can also be implemented by screwing, a guide in the edge region, electrically conductive or electrically non-conductive adhesive.

The opposite second device 1b deviates from the first device 1 in so far as they do not have a measuring device 6 having. The multiplexer 13b the second device 1b is via a connection cable 12 with the measuring device 6 the first device 1 connected. The devices are arranged in such a way that the layers of electrically conductive material 5 . 5b stand opposite. Between these layers, a conductor structure to be tested can be arranged. The distance between the two layers of conductive material 5 . 5b can be reduced so much that the layer 5 the first device having a first surface of the conductor pattern and the layer 5b the second device with a second surface of the conductor structure in contact. Here are the measuring points 2 . 2 B each device with each other via the electrically conductive material 5 . 5b in electrically conductive connection, which is influenced by the conductor tracks of the adjacent conductor structure.

In addition, the measuring points can also 2 . 2 B the two devices 1 . 1b stand in electrically conductive connection with each other and are tested against each other.

4 schematically shows the structure of the first embodiment, for testing an electric cable 14 , This is the plug 15 in the electrically conductive material 5 pressed. Contacts of coupling 16 of the electric cable 14 be through an adapter 17 led out. The adapter 17 gets into the electrically conductive material 5 pressed.

LIST OF REFERENCE NUMBERS

1

Tester

2

measuring point

3

First page of the plate

4

Second side of the plate

5

Electrically conductive material

6

measuring device

7

plate

8th

Electrically conductive adhesive

9

via

10

casing

11

Contact points

12

connection cable

13

multiplexer

14

Electric cable

15

plug

16

clutch

17

adapter

Claims (10)

Contraption ( 1 ) for testing a conductor structure, wherein the device ( 1 ) on a first page ( 3 ) a plurality of measuring points ( 2 ), and the device ( 1 ) on a second page ( 4 ) an electrically conductive material ( 5 ), which with the plurality of measuring points ( 2 ) is in electrically conductive connection, characterized in that the electrically conductive material ( 5 ) an electrically conductive connection of the plurality of measuring points ( 2 ) forms with each other. Contraption ( 1 ) according to claim 1, characterized in that the device ( 1 ) a measuring device ( 6 ), which exceeds the measuring points ( 2 ) with the electrically conductive material ( 5 ) connected is. Contraption ( 1 ) according to one of the preceding claims, characterized in that the device ( 1 ) consists of at least two layers, wherein the first layer is a plate ( 7 ), whereby the plate ( 7 ) on a first page ( 3 ) Measuring points ( 2 ) and on a second page ( 4 ) Contact points ( 11 ), which with the second layer containing the conductive material ( 5 ) are in electrically conductive connection. Contraption ( 1 ) according to claim 3, characterized in that an electrically conductive connection between the measuring points ( 2 ) and the contact points ( 11 ) a via ( 9 ). Contraption ( 1 ) according to claim 3, characterized in that an electrically conductive connection between the measuring points ( 2 ) and the contact points ( 11 ) Comprises needles which are incorporated in the electrically conductive material ( 5 protrude). Contraption ( 1 ) according to one of claims 3 to 5, characterized in that the first layer with the second layer via an electrically conductive adhesive ( 8th ) connected is. Contraption ( 1 ) according to one of claims 3 to 5, characterized in that the first layer is connected to the second layer via an electrically insulating adhesive. Contraption ( 1 ) according to one of claims 3 to 7, characterized in that the second layer is melted onto the first layer. Contraption ( 1 ) according to one of the preceding claims, characterized in that the electrically conductive material ( 5 ) is an electrically conductive foam or an electrically conductive rubber or electrically conductive paint. System for testing a conductor structure comprising a first device ( 1 ) according to one of the preceding claims and a second device ( 1 ) according to one of the preceding Claims, wherein the devices ( 1 ) are arranged relative to each other such that the second layer of the first device ( 1 ) of the second layer of the second device ( 1 ), so that a conductor pattern to be tested can be interposed therebetween.

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