Method and system for testing a printed circuit board populated with components, using a needle adapter

Abstract

The invention relates to a method for testing a printed circuit board populated with components, using a needle adapter, the needles of which are connected to signal electronics, wherein, in a first method step, sample signal curves, in particular target signal curves, or sample frequency spectra are determined, wherein, in a second method step subsequent to the first method step, first contact points of the printed circuit board are electrically contacted by the needles, wherein a first of the needles of the needle adapter is used to couple a high-frequency signal into the contact point of the printed circuit board that is contacted by the first needle, - wherein the signal curves thereupon caused at the other needles of the needle adapter are compared with sample signal curves and are monitored with respect to whether a permissible extent of deviation is exceeded - or wherein the frequency spectra, of signal curves, which are thereupon caused at the other needles of the needle adapter are compared with sample frequency spectra and are monitored with respect to whether a permissible extent of deviation is exceeded.

Description

[0001] Method and system for testing a printed circuit board populated with components using a needle adapter

[0002] Description:

[0003] The invention relates to a method and a system for testing a printed circuit board populated with components using a needle adapter.

[0004] It is generally known that high manufacturing quality can be achieved by subjecting the manufactured products to inspection.

[0005] A method for testing circuit boards is known from EP 618453 A2.

[0006] A test system for a circuit carrier is known from DE 102006 021 569 A1.

[0007] From DE 102007 007 339 A1 a method for locating faults on electronic printed circuit boards is known.

[0008] The invention is therefore based on the objective of further developing a method for testing a printed circuit board, whereby a comprehensive inspection of the printed circuit board can be carried out with as few contact points as possible.

[0009] According to the invention, the problem is solved in the method according to the features specified in claim 1 and in the system according to the features specified in claim 11.

[0010] Important features of the invention in the method for testing a printed circuit board populated with components using a needle adapter whose needles are connected to signal electronics are that in a first process step, sample signal waveforms, in particular target signal waveforms, or sample frequency spectra, in particular target frequency spectra, are determined, wherein in a second process step arranged temporally after the first process step, the needles electrically contact first contact points of the printed circuit board.

[0011] ISI \ EIDOPAT 27.03.2025 wherein a high-frequency signal is introduced and / or coupled into the contact point of the circuit board contacted by the first needle of the needle adapter by means of a first of the needles,

[0012] - wherein the signal waveforms produced on the other needles of the needle adapter, in particular voltage signal waveforms, are compared with sample signal waveforms and are monitored for exceeding a permissible level of deviation and / or wherein the frequency spectra of signal waveforms produced on the other needles of the needle adapter, in particular voltage signal waveforms, are compared with sample frequency spectra and are monitored for exceeding a permissible level of deviation.

[0013] The advantage here is that the coupled high-frequency signal propagates via the traces and components of the populated circuit board, and the signal waveforms or frequency spectra of the signal waveforms that then occur at the other contact points represent a characteristic step response. Thus, the step response is characteristic of the populated circuit board and changes significantly if a short circuit occurs between two traces, a solder joint fails or was not manufactured flawlessly, or if a component is defective.It is particularly advantageous to compare not only the signal waveforms but also the frequency spectra with patterns, since this way, for example, a signal waveform that only shows permissible deviations from a pattern signal waveform, but has an impermissibly large deviation from a pattern frequency spectrum, is recognized as impermissible and thus an error is detected.

[0014] In an advantageous embodiment, the high-frequency signal is a Dirac pulse and / or the high-frequency signal exhibits a Dirac pulse-shaped voltage signal and / or the high-frequency signal is an electrical voltage pulse generated by a controllable switch of the signal electronics, and which is as similar as possible to an ideal Dirac pulse. It is advantageous that all frequencies are coupled in with essentially the same intensity, and therefore the frequency spectra represent the frequency-dependent attenuation along the path from the contact point through which the Dirac pulse is coupled in to the contact point contacted by another needle, from whose signal a respective frequency spectra is determined.Errors or changes to solder joints or contact points, or replacement of components with functionally equivalent but not identically designed components, cause changes regarding the conductor inductances and capacitances of the conductor tracks and thus also changes in the frequency-dependent attenuation.

[0015] In an advantageous embodiment, the pattern signal waveforms are determined in the first process step by electrically contacting first contact points of at least one pattern printed circuit board with the needles of the needle adapter, in particular wherein the pattern printed circuit board is identical in construction to the printed circuit board, wherein a high-frequency signal is coupled into the contact point of the pattern printed circuit board contacted by the first needle by means of the needle or a first of the needles of the needle adapter.

[0016] - wherein the resulting signal waveforms, in particular voltage signal waveforms, are recorded and stored as sample signal waveforms, or wherein the resulting frequency spectra of the signal waveforms, in particular voltage signal waveforms, are recorded and stored as sample frequency spectra.

[0017] The advantage here is that a high-frequency signal, especially a Dirac pulse, can propagate widely in the populated circuit board, and therefore an entire sub-area can be monitored in a single process step for unacceptably large deviations from a target value.

[0018] In an advantageous embodiment, the first process step is executed multiple times, with an identical sample circuit board being used for each execution. The sample signal waveforms are determined by averaging the sample signal waveforms obtained during each execution. An advantage of this approach is that a permissible deviation can be taken into account. Since a different sample circuit board is used for each execution of the first process step, a permissible deviation can be derived from the multiple executions. Exceeding this permissible deviation triggers a warning message during the execution of the second process step.

[0019] In an advantageous design, a warning message is displayed and / or forwarded if the permissible deviation limit is exceeded. The advantage here is that safety can be increased.

[0020] In an advantageous embodiment, the respective prototype circuit board is assembled and manufactured flawlessly with flawless components. The advantage here is that the respective prototype circuit board is guaranteed to be free of defects, and thus, during subsequent measurements on a circuit board, it can be determined by comparison with good values ​​whether a permissible deviation has been exceeded.

[0021] In an advantageous embodiment, the signal electronics comprise a neural network to which the high-frequency signal and the signal waveforms, particularly voltage waveforms, detected at the needles are fed. In the first process step, the neural network, acting as a learning phase, teaches the signal waveforms or frequency spectra of sample circuit boards to represent acceptable states. In the second process step, the neural network monitors the signal waveforms or frequency spectra of the circuit board for deviations exceeding a permissible level. An advantage of this approach is that the first process step allows for simple training or instruction of the neural network.

[0022] In an advantageous embodiment, the second process step is repeated multiple times, wherein, instead of using the first needle, a different needle of the needle adapter is used to introduce and / or couple a high-frequency signal into the contact point of the printed circuit board contacted by the first needle. The advantage here is that even greater reliability can be achieved, since areas of the printed circuit board that are far from the respective coupling point contribute only minimally to the response, i.e., to the signal waveforms or frequency spectra.

[0023] In an advantageous embodiment, the process steps are repeated, with another printed circuit board being used instead of the first, which also has the initial contact points, and further contact points on the second printed circuit board being configured, in particular according to the different functionalities. An advantage of this is that the printed circuit boards of an entire series of printed circuit boards can be tested with a single needle adapter, especially with the same needle adapter.

[0024] Key features of the system, particularly for carrying out the aforementioned method, are that the system comprises a printed circuit board populated with components and a needle adapter whose needles are connected to signal electronics, in particular wherein the needles electrically touch and / or contact first contact points of the printed circuit board, wherein a first of the needles of the needle adapter introduces a high-frequency signal into the contact point of the printed circuit board contacted by the first needle, wherein the signal electronics are designed such that the signal waveforms, in particular voltage signal waveforms, detected by the signal electronics at the other needles of the needle adapter are compared with reference signal waveforms and are monitored for exceeding a permissible level of deviation, or that the frequency spectra of signal waveforms detected by the signal electronics at the other needles of the needle adapter,In particular, voltage signal waveforms are compared with sample frequency spectra and monitored for exceeding a permissible level of deviation.

[0025] The advantage here is that by coupling in a high-frequency signal, a large area of ​​the circuit board can be tested.

[0026] In an advantageous embodiment, the system includes a template circuit board which can also be contacted by the needle adapter at the first contact points, so that template signal waveforms or template frequency spectra can be acquired and stored. It is advantageous that the system includes not only the needle adapter, but also the circuit board and at least one template circuit board, wherein the signal electronics of the needle adapter store the good values ​​or the knowledge of the good values ​​and therefore then perform the test by comparing them with the actual values ​​acquired on the circuit board. Further advantages arise from the dependent claims. The invention is not limited to the combination of features of the claims.For the person skilled in the art, further meaningful combination possibilities of claims and / or individual claim features and / or features of the description and / or the figures arise, in particular from the problem statement and / or the task arising from comparison with the prior art.

[0027] The invention will now be explained in more detail with reference to schematic illustrations:

[0028] Figure 1 schematically sketches a system according to the invention for carrying out a quality inspection of a populated printed circuit board 4 in a side view.

[0029] Figure 2 shows a corresponding system schematically unfolded in oblique view.

[0030] As shown in the figures, the system has a printed circuit board 4 equipped with components 5, which is electrically contacted at first contact points 3, in particular solder joints or through holes, by a needle adapter having an adapter plate 1 equipped with needles 2.

[0031] After contact is established, one or more of the needles 2 are brought to an electrical potential and the potential that arises on one or more other needles 2 of the needle adapter is detected and compared with a target potential assigned to each of these needles 2.

[0032] In this way, a manufacturing defect during the assembly of circuit board 4 can be detected, and a corresponding warning can be displayed and / or forwarded. Appropriate signal electronics are arranged on the adapter board 1, which generates the aforementioned potentials and transmits them to the corresponding pins 2, or detects the potentials at the other pins 2 and compares them with the target potentials.

[0033] In a further process step, a potential is then applied to one or more other needles, and the resulting potential is again detected at the remaining contact points contacted by the needles 2, in particular solder joints or through holes.

[0034] Instead of potentials, temporal potential profiles can also be used, whereby the resulting recorded temporal potential profiles are compared with target potential profiles. According to the invention, some of the contact points arranged on the circuit board 4 are not contacted by the needles 2. Thus, improved quality control would be possible by contacting these unused contact points 3.

[0035] According to the invention, however, not all available contact points 3 are used, but only a subset of them.

[0036] A series of printed circuit boards, each having the first contact points for contact with the needles 2 of the needle adapter but otherwise being constructed differently and thus having different functionalities, can therefore be tested with the same needle adapter.

[0037] However, in order to achieve a sufficiently high quality despite the small number of first contact points of the needles, a high-frequency signal, in particular a Dirac pulse, is introduced at a first contact point and the voltage signals that arise at the other needles 2 are recorded or a frequency spectrum of the voltage signals is generated.

[0038] These voltage signals or frequency spectra are compared with corresponding target voltage signals or frequency spectra, which were previously recorded and stored on a flawlessly assembled printed circuit board, in particular a prototype printed circuit board.

[0039] In this way, the response to a Dirac pulse is determined by the exceeding of an unacceptably high degree of deviation from the corresponding signals of a flawless, component-populated prototype circuit board.

[0040] In further process steps, a Dirac pulse can then be coupled to another needle 2, and the signal profiles or frequency spectra that develop at the other contact points contacted by the needle adapter are also monitored for exceeding a permissible level of deviation, especially in comparison to those of the flawless prototype circuit board.

[0041] The advantage of the invention lies in the fact that a series of differently populated printed circuit boards can be checked for defects with very high accuracy using only a few needles 2 and the same needle adapter. The needles 2 are tapered with increasing distance from the adapter plate 1. The contact points 3 are designed as metallized through-holes into which the needles can be inserted to establish electrical contact. In further embodiments of the invention, the Dirac pulse is also used as a synchronization signal, wherein the Dirac pulse represents a time zero or a reference point, and the acquired signal waveforms or frequency spectra are processed with respect to this point in time, and the stored signals or spectra of the defect-free prototype printed circuit board are also referenced to this point in time.

[0042] In further embodiments of the invention, the signal electronics comprise a neural network that is trained on the signals or spectra of the prototype circuit board and to which the acquired signals or spectra are subsequently fed. Due to the large number of needles and associated signal waveforms or spectra, only a small amount of programming effort is required when using the neural network.

[0043] Reference symbol list

[0044] 1 adapter plate 2 needles

[0045] 3. Contact point, in particular solder joint or through hole

[0046] 4 circuit boards

[0047] 5 components

Claims

Patent claims:

1. A method for testing a printed circuit board populated with components using a needle adapter whose needles are connected to signal electronics, wherein in a first method step sample signal waveforms, in particular target signal waveforms, or sample frequency spectra, in particular target frequency spectra, are determined, wherein in a second method step arranged temporally after the first method step, the needles electrically contact first contact points of the printed circuit board, characterized in that a high-frequency signal is introduced and / or coupled into the contact point of the printed circuit board contacted by the first needle by means of a first of the needles of the needle adapter. - wherein the signal waveforms produced on the other needles of the needle adapter, in particular voltage signal waveforms, are compared with sample signal waveforms and are monitored for exceeding a permissible level of deviation and / or wherein the frequency spectra of signal waveforms produced on the other needles of the needle adapter, in particular voltage signal waveforms, are compared with sample frequency spectra and are monitored for exceeding a permissible level of deviation.

2. Method according to claim 1, characterized in that the high-frequency signal comprises a Dirac pulse-shaped voltage signal and / or that the high-frequency signal is an electrical voltage pulse generated with a controllable switch of the signal electronics, which is as similar as possible to an ideal Dirac pulse.

3. A method according to one of the preceding claims, characterized in that in the first method step the pattern signal waveforms are determined by electrically contacting first contact points of at least one pattern printed circuit board with the needles of the needle adapter, in particular wherein the pattern printed circuit board is identical in construction to the printed circuit board, wherein a high-frequency signal is coupled into the contact point of the pattern printed circuit board contacted by the first needle by means of the needle or a first of the needles of the needle adapter. - wherein the resulting signal waveforms, in particular voltage signal waveforms, are recorded and stored as sample signal waveforms, or wherein the resulting frequency spectra of the signal waveforms, in particular voltage signal waveforms, are recorded and stored as sample frequency spectra.

4. Method according to one of the preceding claims, characterized in that the first method step is carried out multiple times, wherein a structurally identical sample circuit board is used as the sample circuit board in each instance, wherein the sample signal profiles are determined by averaging the sample signal profiles determined during the multiple executions.

5. Method according to one of the preceding claims, characterized in that a warning information is displayed and / or forwarded after the permissible degree of deviation has been exceeded.

6. Method according to one of the preceding claims, characterized in that the, in particular each, sample printed circuit board, in particular each, is free of defects and is equipped and manufactured with defect-free components.

7. Method according to one of the preceding claims, characterized in that the signal electronics comprise a neural network to which the high-frequency signal and the signal waveforms detected at the needles, in particular voltage signal waveforms, are fed, wherein in the first method step, as a learning phase, the neural network teaches the signal waveforms or frequency spectra of sample printed circuit boards as good condition and in the second method step monitors the signal waveforms or frequency spectra of the printed circuit board for exceeding a permissible level of deviation.

8. Method according to one of the preceding claims, characterized in that the second method step is in particular repeated several times, wherein instead of with the first needle a high frequency signal is introduced and / or coupled into the contact point of the circuit board contacted by the first needle with a respective other needle of the needle adapter.

9. Method according to one of the preceding claims, characterized in that the method steps are repeated, wherein instead of the printed circuit board, a further printed circuit board is used which also has the first contact points, wherein further contact points of the further printed circuit board are designed, in particular according to the different functionalities.

10. Method according to one of the preceding claims, characterized in that the system has a template circuit board which is also contacted by the needle adapter at the first contact points, so that template signal waveforms or template frequency spectra are captured and stored.

11. System, in particular for carrying out a method according to one of the preceding claims, wherein the system comprises a printed circuit board populated with components and a needle adapter, the needles of which are connected to signal electronics, in particular wherein the needles electrically touch and / or contact first contact points of the printed circuit board. characterized in that a first of the needles of the needle adapter introduces a high-frequency signal into the contact point of the printed circuit board contacted by the first needle, wherein the signal electronics are configured such that the signal waveforms, in particular voltage signal waveforms, detected by the signal electronics at the other needles of the needle adapter are compared with reference signal waveforms and are thereby monitored for exceeding a permissible level of deviation, or that the frequency spectra of signal waveforms, in particular, detected by the signal electronics at the other needles of the needle adapter, are Voltage signal waveforms are compared with sample frequency spectra and monitored for exceeding a permissible level of deviation.

12. System according to claim 11, characterized in that the system has a pattern circuit board which can also be contacted by the needle adapter at the first contact points, so that pattern signal waveforms or pattern frequency spectra can be detected and stored.

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