JP2004271538A - Electronic circuit inspection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inspection device enabling the inspection of a parallel-connected low-impedance circuit which is difficult to determine by an inspection with application of a DC or AC minute signal and further a flexible electronic circuit inspection device. <P>SOLUTION: This electronic circuit inspection device 10 comprises a pulse signal source 15 for applying a pulse signal to a circuit to be inspected, an analog/digital converter 11 for analog-digital converting a transient response signal to the pulse signal of the circuit to be inspected, a microprocessor 12 for arithmetically processing the digitally-converted transient response signal, extracting the frequency of a vibration waveform based on the peak time or zero-cross time of the transient response signal waveform, and comparing it with the vibration frequency of a normal circuit, thereby determining the abnormality of the circuit to be inspected, and a display device 14 for displaying the inspection result of the circuit to be inspected. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention generally relates to an electronic circuit inspection apparatus, and more particularly to an inspection apparatus applied to inspect a connection failure of low impedance elements connected in parallel.

  In the manufacturing process of electrical appliances equipped with electronic circuits, actual inspections at the actual product level are performed at the board unit level for the purpose of detecting electronic circuit failure or early failure. ing. 2. Description of the Related Art Conventionally, there is an in-circuit tester as an automatic inspection device at a substrate single level.

  The inspection method is to supply a weak DC or AC signal to the device or circuit to be inspected, measure the impedance value in a steady state, and compare it with preset non-defective data. This is a method for inspecting an electronic component connection failure.

  In the circuit shown in FIG. 1, when an attempt is made to inspect a disconnection failure of the diode 2 to be inspected, a weak DC or AC signal conventionally supplied by an in-circuit tester is supplied to measure the impedance value in a steady state. In this method, the characteristic between the base and the emitter of the NPN transistor 1 connected in parallel with the diode 2 to be inspected (a characteristic in which current flows easily from the base to the emitter and a current does not flow in the reverse direction) overlaps with the NPN transistor 1 in the steady state. Even if the impedance value is measured at the above, the change cannot be captured.

  In the case of a PNP transistor instead of an NPN transistor, the same applies when a diode is connected in parallel between the base and the collector in the forward direction.

  An object of the present invention is to solve the above-mentioned problem and to provide an automatic inspection apparatus for diodes connected in parallel in a forward direction.

  An electronic circuit inspection apparatus according to the present invention includes a pulse signal source that applies a pulse signal to a circuit under test, an analog-to-digital converter that converts a transient response signal of the circuit under test to the pulse signal from analog to digital, and the digital conversion. The calculated transient response signal is subjected to arithmetic processing, the frequency of the vibration waveform is extracted based on the peak time or the zero crossing time of the transient response signal waveform, and is compared with the vibration frequency of the normal circuit to determine the abnormality of the circuit under test. And a display device for displaying the test result of the circuit under test.

The present invention applies a pulse signal to a circuit under test and performs a test based on the resulting transient response signal waveform. Therefore, a low impedance circuit connected in parallel which is difficult to determine by applying a DC or AC small signal is difficult. Inspection is possible.
Further, since the abnormality is determined using the change generally occurring due to the abnormality of the circuit under test as an index, a versatile electronic circuit inspection device can be provided.

Embodiment 1 FIG.
FIG. 1 is a measurement circuit diagram of the automatic electronic circuit inspection device according to the first embodiment of the present invention, FIG. 2 is a diagram showing a step signal waveform output from a pulse signal source 15, and FIG. FIGS. 4 and 5 are diagrams showing a rectangular signal waveform, and FIGS. 4 and 5 are diagrams showing output transient response waveforms measured on the secondary side 3b of the transformer 3. FIG. The circuit under test shown in FIG. 1 is, specifically, an electronic circuit element related to the inspection method of the present invention extracted from a choke coil current control type self-excited inverter circuit. The pulse signal source 15 is for supplying a pulse signal to the circuit under test in order to perform a test, and the transient response of the circuit under test is measured as a voltage waveform change from both ends of the transformer secondary 3b. .

  In the circuit operation, first, when the step pulse waveform shown in FIG. 2 is supplied from the pulse signal source 15, a transient change occurs in the current flowing through the primary side 3a of the transformer 3 in response to the voltage step change. Here, a positive signal is applied to the anode of the diode 2. This current change causes a current change on the secondary side 3b of the transformer due to the transformer induced phenomenon, and is measured as a voltage waveform from both ends of the secondary side 3b of the transformer.

  In the transient response waveform measured from both ends of the secondary side 3b of the transformer, when the diode under test 2 is connected, the vibration of the waveform attenuates in a short time as shown in FIG. On the other hand, when the diode under test 2 is not connected, the vibration of the decoy waveform shown in FIG. 5 continues for a clearly longer time than in FIG. Therefore, the change in the state of the circuit under test can be determined from the transient phenomenon waveform measured from both ends of the secondary side 3b of the transformer.

  As shown in the measurement circuit diagram of the inspection device in FIG. 1, the determination method is as follows: a transient response waveform measured from both ends of the secondary side 3b of the transformer is input through the analog-to-digital converter 11; The electrical connection failure of the diode under test 2 is determined by comparing with a determination value preset in the memory 13. The determination result is displayed on the display device 14.

  In the method of setting the determination value, a waveform by a normal circuit is measured, and the setting is performed based on the waveform displayed on the display device 14. Further, a plurality of set values can be registered according to the inspection object and can be easily selected, so that versatility can be provided.

  Although the present embodiment has been described by taking as an example the determination of the quality of the connection of the diode, the inspection target is not limited to this and can be widely applied to an electronic circuit in which a transient response waveform differs due to an abnormality. In particular, the present invention can be applied to an inspection target such as a low-impedance element connected in parallel, which is difficult to determine by applying a small DC or AC signal. Further, since there is no need to apply the actual current voltage to the circuit to be inspected, there is no possibility that the circuit board will be broken during the inspection.

Embodiment 2 FIG.
This embodiment describes a specific method of calculating and determining a transient response waveform by the microprocessor 12. In the example of the diode connection failure described in the first embodiment, the difference between the normal waveform and the abnormal waveform mainly appears as a difference in the duration of the vibration waveform. In such a case, a method of integrating the effective value or the rectified value of the transient response waveform and determining the difference in the duration of the vibration waveform based on the magnitude of the integrated value is suitable. If an analog operation processing circuit such as an effective value circuit, a rectifier circuit, and an integration circuit is provided in front of the analog-to-digital converter 11 so as to perform the analog signal processing instead of the operation by the microprocessor 12, the microprocessor 12 Can be reduced, and the determination processing time can be shortened. Further, it is possible to perform a higher-speed processing of a response waveform as compared with the processing by a microprocessor.

  As another method of calculating and determining the transient response waveform, a method of determining whether the envelope of the response waveform is within a preset range based on the response waveform of the normal circuit can also be applied. According to this method, a more general characteristic of the inspection target waveform can be inspected, so that a highly versatile inspection apparatus can be realized.

  Further, as another method, a method of extracting the time interval of the peak of the response waveform or the interval of the zero crossing time and inspecting the frequency of the vibration waveform can be applied. Since an abnormality in the circuit connection often involves a change in the resonance frequency, a highly versatile abnormality inspection can be performed by comparing and judging the vibration frequency of a normal circuit.

FIG. 2 is a measurement circuit diagram of the automatic electronic circuit inspection device according to the first embodiment of the present invention. FIG. 3 is a diagram showing a waveform of a step signal output from a pulse signal source 15. FIG. 4 is a diagram illustrating a rectangular signal waveform output from a pulse signal source 15. FIG. 7 is a diagram illustrating an output transient response waveform measured on a secondary side 3b of the transformer 3; FIG. 7 is a diagram illustrating an output transient response waveform measured on a secondary side 3b of the transformer 3;

Explanation of reference numerals

  DESCRIPTION OF SYMBOLS 1 NPN transistor, 2 to-be-inspected diode, 3a transformer primary side, 3b transformer secondary side, 4 capacitor, 5 low resistance, 10 test equipment, 11 analog-digital converter (ADC), 12 microprocessor, 13 memory, 14 display , 15 signal source.

Claims (1)

A pulse signal source that applies a pulse signal to the circuit under test, an analog-to-digital converter that converts the transient response signal to the pulse signal of the circuit under test from analog to digital, and arithmetically processes the digitally converted transient response signal. A microprocessor that extracts the frequency of the vibration waveform based on the peak time or the zero crossing time of the transient response signal waveform and compares the frequency with the vibration frequency of the normal circuit to determine whether the circuit under test is abnormal; An electronic circuit inspection device comprising: a display device for displaying an inspection result.

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