EP1364222A1

EP1364222A1 - Method and device for testing the quality of printed circuits

Info

Publication number: EP1364222A1
Application number: EP02714042A
Authority: EP
Inventors: Werner Reisinger
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-02-22
Filing date: 2002-02-20
Publication date: 2003-11-26
Also published as: CA2439167A1; US6881595B2; WO2002067002A1; JP2004522967A; BR0207772A; DE10290637D2; CN1498346A; US20040164742A1

Abstract

The invention relates to a method and to a device for testing electronic circuits or the parts thereof on printed circuits. The inventive method comprises the following steps: (a) detecting the radiation that is emitted by the surface of the printed circuit, (b) converting the detected radiation to data that represent a surface structure and/or depth structure of the printed circuit, (c) comparing the data of the surface structure and/or the depth structure with stored data of a desired state of the surface structure and/or depth structure, and (d) determining any deviations between the data of the detected surface structure and/or depth structure and the data of the desired state of the surface structure and/or depth structure.

Description

Method and device for quality inspection of printed circuit boards

The present invention relates to a method and a device for quality testing of printed circuit boards, according to the respective preamble of claims 1 and 10, respectively.

For the quality control in the manufacture and assembly of printed circuit boards, a mechanical method is known which mechanically scans a test specimen with hundreds of contacts, using shadow masks and using contacts made of special alloys. Individual circuits are contacted for quality testing and their function is tested by an electrical test adapter.

However, electrical testing using contacts and test adapters specially produced for this purpose is complex and prone to failure. The positioning of the contacts in a test adapter is becoming increasingly difficult due to the miniaturization of the electronic assemblies. Since a special test adapter has to be built for each new type of printed circuit board, enormous costs are incurred. Building a medium-sized test adapter, for example, requires the production of around 500 special contacts. The time required for such a set-up is approx. 0.5 days. The costs for this are on average DM 500.00 and quickly rise to more than DM 1,000.00 for SMD layouts. For small series of, for example, 20 pieces of printed circuit boards, it is often not worth investing an additional DM 25.00 testing costs per printed circuit board and an additional production day for a product price of DM 20.00 per piece. This applies in particular to pre-series, since the next test series often changes the layout and thus the arrangement of the test contacts. Changes in the layout of the printed circuit board therefore mean costs incurred for changes to the electrical test adapter or its new construction. However, if based on an inspection of the circuit board, you run the risk of losing the saved costs several times in the case of faulty production.

A special test algorithm is used for the electrical test using the test adapter. If, for example, a conductor is narrowed, this is acknowledged with the test result "error-free", i.e. such production errors are not recognized. Parasitic approaches are also not recognized, which can lead to unusable products, particularly in the case of circuits for high-frequency applications. Likewise, non-centric holes are not recognized as errors.

Another disadvantage of the previous test method is that the electrical test only takes place at the end of the production process, so that a very late fault detection is only possible. The risk of producing a faulty series increases with the number of layers. The probability of defective production is therefore much higher with an 8-layer multilayer circuit board than with a 2-layer circuit board. So far, a multilayer circuit board has to be completely produced in order to be able to determine that the first layer was faulty. The restrictions described above with regard to the undetectable errors cannot be excluded anyway.

Storing electrical test adapters requires a great deal of logistical effort from circuit board manufacturers. It is not known which test adapters are needed when, where or at all again. Stored test adapters must be findable again. After a long storage period, the contacts may require maintenance.

The invention has for its object a method and an apparatus of the above. Provide ways that are improved in terms of reliability and flexibility of the quality inspection with reduced costs at the same time.

This object is achieved according to the invention with a method of the above type with the method steps specified in claim 1 and with a device of the above Kind with the features characterized in claim 10 solved. Advantageous embodiments of the invention are described in the further claims.

According to the invention in a method of the above. The following steps are provided:

(a) detecting radiation emanating from a surface of the circuit board,

(b) converting the detected radiation into data which represent a surface structure and / or depth structure of the printed circuit board,

(c) comparing the data of the surface structure and / or the deep structure with stored data of a desired state of the surface structure and / or deep structure and

(d) determining deviations between the data of the detected surface structure and / or depth structure and the data of the target state of the

Surface structure and / or deep structure.

This has the advantage that in automated, mechanical circuit board manufacture and assembly with high effectiveness and quality, assembly errors as well as defects in the structure and size of the circuit boards themselves can be recognized. Due to the non-contact functionality, considerable cost reductions are achieved. Quality controls can be carried out quickly and reliably. This results in cost and time savings in comparison with conventional test methods, whereby the invention can also be used economically in small series production due to an additional high degree of flexibility. There is no need to position individual sensors. A miniaturization required to adapt to the structures of the circuit boards to be tested is possible at any time. There is no mechanical structure for individual test specimens. The test facility is ready for use in a few minutes, which drastically reduces test costs. If the layout of the circuit boards to be tested changes, only new data needs to be read in to update the test device. As a result, inexpensive, tested printed circuit boards are achieved even with small quantities. The test result guarantees practically 100% freedom from errors and provides an unprecedented level of quality. Improperly etched conductor tracks and unclean soldering points on Pieces of printed circuit board are recognized as well as non-centric holes or incorrectly milled dimensions of the circuit board. Since the test method according to the invention can be used quickly, easily and inexpensively between all production steps, series production errors can be excluded. This achieves a significant production advantage with the expensive multilayer printed circuit boards. Due to the easy manageability of data, large quantities of different test objects can be stored in a small space. In addition, it is possible to meet the quality-related requirements, for example in aerospace technology. In addition, proof of quality can be provided for all individual manufacturing processes for each individual product.

The recorded data as well as the data of the target state are preferably data in digital form.

After step (d), the deviations are expediently compared with corresponding tolerance bands, and depending on this comparison, a test result is generated “error-free” for the printed circuit board if the deviations are within the tolerance bands, or “defective” if the Deviations are at least partially outside the tolerance bands.

In a preferred embodiment, the surface structure and / or deep structure is detected in step (a) by means of electromagnetic waves reflected from and / or transmitted by the surface, in particular in the frequency spectrum of visible light, X-rays, radar rays, microwave rays and / or infrared radiation ,

From corresponding changes in temperature over time, one can conclude from the structural conditions at the surface and in depth that heat radiation emitted by the surface is detected in step (a) and in step (b) from a change in the heat radiation via the Time the surface structure and / or depth structure is analyzed. To carry out a dynamic measurement, the circuit board is heated or cooled during the measurement in step (a).

For example, the detection in step (a) is carried out by means of a thermo-optical difference measurement.

The deviations from step (b) are stored on a mass storage device for appropriate circuit board-specific documentation.

A test that can be carried out particularly quickly is achieved by the data of the desired state of the surface structure being a layout of the printed circuit board designed during the planning.

A device of the above. Art is characterized according to the invention by a sensor for detecting a radiation emanating from a surface of the circuit board, a device for converting the detected radiation into data which represent a surface structure and / or depth structure of the circuit board, a device for comparing the data of the surface structure and / or the deep structure with stored data of a desired state of the surface structure and / or deep structure and a device for determining deviations between the data of the detected surface structure and / or deep structure and the data of the desired state of the surface structure and / or deep structure.

This has the advantage that in automated, mechanical circuit board manufacture and assembly with high effectiveness and quality, assembly errors as well as defects in the structure and size of the circuit boards themselves can be recognized. Due to the non-contact functionality, considerable cost reductions are achieved. Quality controls can be carried out quickly and reliably. This results in cost and time savings in comparison with conventional test methods, whereby the invention can also be used economically in small series production due to an additional high degree of flexibility. There is no need to position individual sensors. A miniaturization required to adapt to the structures of the circuit boards to be tested is possible at any time. A mechanical one There is no setup for individual test objects. The test facility is ready for use in a few minutes, which drastically reduces test costs. If the layout of the circuit boards to be tested changes, only new data needs to be read in to update the test device. As a result, inexpensive, tested printed circuit boards are achieved even with small quantities. The test result guarantees practically 100% freedom from errors and provides an unprecedented level of quality. Improperly etched circuit traces as well as unclean soldering points on assembled circuit boards are recognized as well as non-centric holes or wrongly milled dimensions of the circuit board. Since the test method according to the invention can be used quickly, easily and inexpensively between all production steps, series error productions can be excluded. This achieves a significant production advantage with the expensive multilayer printed circuit boards. Due to the easy manageability of data, large quantities of different test objects can be stored in a small space. In addition, it is possible to meet the quality-related requirements, for example in aerospace technology. In addition, proof of quality can be provided for all individual manufacturing processes for each individual product.

A device for comparing the deviations with corresponding tolerance bands is expediently provided, which, depending on this comparison, generates a test result "error-free" for the printed circuit board if the deviations are within the tolerance bands, or "error-prone" if the deviations are at least partially are outside the tolerance bands.

In a preferred embodiment, the sensor is designed to detect electromagnetic waves, in particular in the frequency spectrum of visible light, X-rays, radar rays, microwave rays or infrared radiation, and is arranged in such a way that it detects electromagnetic waves reflected by and / or transmitted by the printed circuit board , For example, the sensor is designed to detect heat radiation from the surface of the printed circuit board and the device for converting the detected radiation into data which represent a surface structure and / or deep structure of the printed circuit board is designed such that this device changes the heat radiation via the Time at a specific location on the circuit board and / or the surface structure and / or depth structure is analyzed via the surface of the circuit board.

A device for cooling or heating the circuit board during the measurement, in particular a laser, is provided for carrying out a dynamic measurement.

For example, the device is designed to carry out a thermo-optical difference measurement.

For documentation of the test results on a circuit board-specific basis, the device additionally has a mass memory for storing the deviations.

In a particularly preferred embodiment, the sensor is at least a pyro sensor or a thermal imaging camera. Alternatively, the sensor comprises a laser.

A test station that can be set up quickly, easily and inexpensively is achieved in that the device for converting, the device for comparing and the device for determining deviations are designed in a computer. This means that only software and a database have to be adapted to the circuit board to be specifically tested. Hardware adaptation of the test device to the layout of the circuit board is completely eliminated.

The invention is explained below with reference to the drawing. In the single figure, this shows a schematic block diagram of an exemplary embodiment of a device according to the invention for executing the method according to the invention. The exemplary embodiment of a device 10 according to the invention for testing printed circuit boards 12 with a surface structure 14, which can be seen from the FIG A device 22 for comparing the digital data of the surface structure 14 with digital data of a desired state of the surface structure stored in a memory 24 and for determining deviations between the digital data of the detected surface structure 14 and the digital data of the desired state of the surface structure from the memory 24. These deviations are stored in a mass memory 26 and fed to a device 28 for comparing the deviations with corresponding tolerance bands, which are stored in a memory 30. Depending on this comparison, the device 28 for the printed circuit board 14 generates the test result “error-free” if the deviations are within the tolerance bands, or “faulty” if the deviations are at least partially outside the tolerance bands.

This test result is stored on the mass storage device 26, displayed on a display device 32, fed to a printer 34 which prints out a log online, and is passed on to a process control 36. The process control 36 automatically sorts the printed circuit board 12 out of the production line if it receives the test result "faulty" from the device 28.

The sensor 18 is, for example, an optical sensor which records electromagnetic waves 38 from the visible spectrum, infrared range, X-rays, radar rays after reflection on the surface structure 14 of the printed circuit board 12 and feeds them to an image processing or image recognition device 16.

Because of the simple and inexpensive construction of the test device 10, it may be provided for the printed circuit board 12 at several points in the production process. For example, in the manufacture of printed circuit boards 12 with multiple Ren layers after each layer production, the surface structure 14 are checked.

The comparison data in the memory 24 are the data of the layout from the design of the printed circuit board 12. Today, this design is produced exclusively by computer, so that this layout data is immediately available as digital data and, if appropriate, is only converted accordingly for the comparison in the device 22 Need to become. In other words, the sensor 18 is used to query a material structure 14 of the printed circuit board 12 as an actual value without contact and to compare it with a target value, namely the layout data of the CAD design of the printed circuit board. The tolerance bands in memory 30 then specify permissible deviations of the actual values according to the detected surface structure from the target values according to data memory 24. If values fall outside the tolerance bands, the circuit board 12 is classified as faulty by the device 28 and can be pulled out of the ongoing process immediately. Possibly. the process controller 36 provides a correction of process parameters in order to counteract a systematic error on the printed circuit boards 12. If it is necessary for service personnel to intervene in the production process, the process control 36 stops the production and gives a corresponding indication. This effectively prevents undesirable and possibly costly production of rejects.

It has proven to be particularly advantageous that the method according to the invention and the device according to the invention carry out the test without contact. Since no mechanical contacts between the test device 10 and the test object, namely the printed circuit board 12, are necessary, the test device 10 does not have to adapt the hardware to the layout of the printed circuit board 12. The only adaptation takes place at the software level, in particular with the data in the memories 24 and 30. The testing device 10 can be adapted to changes in the layout by simple mouse clicks.

The printout from the printer 34 and the data in the memory 26 are used for documentation, it being possible in a simple manner to also subsequently carry out all the test results from various points in the production process. lent to a specific circuit board. In this way, a complete test report with proof of correct production can be attached to the finished printed circuit board. The data in the mass storage device 26 can be stored indefinitely without special storage costs and possibly made available worldwide via the Internet.

An interface between sensor and computer only has to be created once and is independent of the type and layout of the circuit board.

A thermo-optical difference measurement is particularly preferred. For this purpose, heat radiation emanating from the surface of the printed circuit board 12 is detected by the sensor 18 and evaluated in the device 16. Conclusions can be drawn here both on the surface structure and on the depth structure of the printed circuit board 12. For example, there is an analysis of the change in heat radiation over the surface of the circuit board, i.e. the different heat radiation at different locations on the circuit board, from which a surface structure can immediately be taken. Alternatively or additionally, the printed circuit board 12 is heated and the change in the heat radiation is determined at certain locations, i.e. in other words, a warming gradient. For example, vias in the circuit board, i.e. in general in the broadest sense the depth structure within the circuit board can be checked. Due to the larger, heat-absorbing mass, a fully developed through-contact will heat up more slowly than an incomplete via, so that the latter can be identified in a contactless, simple and quick manner. Instead of measuring the change in heat radiation over time during heating, the change in heat radiation over time during cooling can also be recorded after the circuit board has been heated. In this case, for example, a complete plated-through hole will cool down more slowly than an incomplete plated-through hole because of the larger mass, which contains a larger amount of heat, so that the last-mentioned faults on the printed circuit board 12 can be determined easily, quickly, contactlessly and non-destructively even after the printed circuit board 12 has been completed are.

Claims

claims:

1. A method for testing electronic circuits or parts thereof on a printed circuit board, the following steps (a) detecting a starting from a surface of the printed circuit board

Radiation,

(d) determining deviations between the data of the detected surface structure and / or deep structure and the data of the desired state of the surface structure and / or deep structure.

2. The method according to claim 1, characterized in that the data in step (b) and the data of the desired state in step (c) are digital data.

3. The method according to claim 1 or 2, characterized in that after step (d) the deviations are compared with corresponding tolerance bands and a test result "error-free" is generated as a function of this comparison for the circuit board if the deviations are within the tolerance bands , or "error-prone" is generated if the deviations are at least partially outside the tolerance bands.

4. The method according to at least one of the preceding claims, characterized in that in step (a) the surface structure and / or depth Structure is detected by means of electromagnetic waves reflected from and / or transmitted by the surface, in particular in the frequency spectrum of visible light, X-rays, radar rays, microwave rays and / or infrared radiation.

5. The method according to at least one of claims 1 to 3, characterized in that in step (a) radiated heat radiation is detected and in step (b) from a change in heat radiation over time at a certain location on the circuit board and / or the surface structure and / or depth structure is analyzed via the surface of the printed circuit board.

6. The method according to claim 5, characterized in that the circuit board is heated or cooled during the measurement in step (a).

7. The method according to claim 5 or 6, characterized in that the detection in step (a) is carried out by means of a thermo-optical differential measurement.

8. The method according to at least one of the preceding claims, characterized in that the deviations from step (b) are stored on a mass storage device.

9. The method according to at least one of the preceding claims, characterized in that the data of the target state of the surface structure are a layout of the printed circuit board designed during planning.

10. Device (10) for testing electronic circuits or their parts on printed circuit boards (12), characterized by a sensor (18) for detecting a radiation emanating from a surface of the printed circuit board (12), a device (20) for converting the detected radiation In data representing a surface structure (14) and / or depth structure of the printed circuit board (12), a device (22) for Comparing the data of the surface structure (14) and / or the deep structure with stored data of a desired state of the surface structure (14) and / or deep structure and a device (22) for determining deviations between the data of the detected surface structure (14) and / or deep structure and the data of the desired state of the surface structure (14) and / or deep structure.

11. The device (10) according to claim 10, characterized in that the data in step (b) and the data of the desired state in step (c) are digital data.

12. The device (10) according to claim 10 or 1 1, characterized in that a device (28) for comparing the deviations with corresponding tolerance bands is provided which, depending on this comparison for the circuit board (12) produces a test result "error-free" , if the deviations are within the tolerance bands, or "faulty" if the deviations are at least partially outside the tolerance bands.

13. The device (10) according to any one of claims 10 to 12, characterized in that the sensor (18) for detecting electromagnetic waves, in particular in the frequency spectrum of visible light, X-rays, radar rays, microwave rays or infrared radiation, is formed and arranged in such a way that he reflected from the circuit board and / or detected by this transmitted electromagnetic waves.

14. The device (10) according to any one of claims 10 to 12, characterized in that the sensor (18) is designed to detect heat radiation from the surface of the circuit board (12) and that the device (20) for converting the detected radiation into Data representing a surface structure (14) and / or depth structure of the printed circuit board (12) is designed in such a way that this device (20) results from a change in the heat radiation over time at a specific location on the printed circuit board (12) and / or the surface structure (14) and / or depth structure is analyzed via the surface of the printed circuit board (12).

15. The device (10) according to claim 14, characterized in that a device for cooling or heating the circuit board during the measurement, in particular a laser, is provided.

16. The device (10) according to claim 14 or 15, characterized in that it is designed to carry out a thermo-optical differential measurement.

17. The device (10) according to at least one of claims 10 to 16, characterized in that it additionally has a mass storage device (26) for storing the deviations.

18. The device (10) according to at least one of claims 10 to 17, characterized in that the sensor (18) is at least one pyrosensor or a thermal imager.

19. The device (10) according to at least one of claims 10 to 18, characterized in that the sensor (18) comprises a laser.

20. The device according to at least one of claims 10 to 19, characterized in that the device (20) for converting, the device (22) for comparing and the device (22) for determining deviations are designed in a computer.