JPH11108997A - Electronic circuit-inspecting apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inspect a parallel-connected low-impedance circuit which is hard to judge with the application of a d.c. or a.c. minute signal, by applying a pulse signal to the circuit to be inspected and inspecting on the basis of a resulting transient response signal waveform. SOLUTION: When a step pulse waveform is supplied from a pulse signal source 15, a transient phenomenal change is brought about in response to a voltage step change to a current flowing at a primary side 3a of a transformer 3. A positive-polarity signal is impressed to an anode of a diode 2. The current change generates a current change at a secondary side 3b of the transformer because of a transformer induction phenomenon. The current change is measured as a voltage waveform from both ends of the secondary side 3b of the transformer. A measured transient response waveform is attenuated in vibration in a short time if the diode 2 to be inspected is connected. Unless the diode 2 to be inspected is connected, the vibration continues for a long time. Therefore, a state change of the circuit to be inspected can be judged from the transient phenomenal waveform.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention 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 a low impedance element connected in parallel.

[0002]

2. Description of the Related Art In a manufacturing process of an electric appliance on which an electronic circuit is mounted, if an actual inspection is performed at an actual product level, the electronic circuit may be destroyed or an early failure may be detected at a substrate single level. Has been tested. 2. Description of the Related Art Conventionally, there is an in-circuit tester as an automatic inspection apparatus at a single substrate level.

In the inspection method, a weak DC or AC signal is supplied to an element or a circuit to be inspected, an impedance value in a steady state is measured, and the printed value is compared with preset non-defective data. This is a method for inspecting a connection failure of an electronic component on a substrate.

[0004]

In the circuit shown in FIG. 1, when an attempt is made to check for an open circuit failure of the diode under test 2, a weak DC or AC signal conventionally provided by an in-circuit tester is supplied. In the method of measuring the impedance value in the steady state, the diode under test 2
Because the characteristic between the base and the emitter of the NPN transistor 1 connected in parallel with the characteristic (the characteristic that the current easily flows from the base to the emitter and the current does not flow in the reverse direction) overlaps, the impedance value in the steady state is measured. Cannot capture that change.

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 problems and to provide an automatic inspection device for diodes connected in parallel in a forward direction.

[0007]

According to a first aspect of the present invention, there is provided an electronic circuit inspection apparatus comprising: a pulse signal source for applying a pulse signal to a circuit under test; and a transient response signal of the circuit under test to the pulse signal. An analog-to-digital converter for performing analog-to-digital conversion; and a micro-processor for performing arithmetic processing on the digitally-converted transient response signal and comparing it with a determination value set based on a transient response signal of a normal circuit to determine an abnormality of the circuit under test. And a display device for displaying a transient response signal waveform of the circuit under test or the normal circuit and a test result of the circuit under test.

In an electronic circuit inspection apparatus according to a second configuration of the present invention, the pulse signal source generates a step pulse waveform, a rectangular pulse, or a rectangular pulse waveform.

In a third aspect of the present invention, in the electronic circuit inspection device, the microprocessor calculates a duration of an oscillation waveform of a transient response signal of the circuit under test.

According to a fourth aspect of the invention, there is provided an electronic circuit inspection apparatus, wherein the microprocessor calculates an integral value of an effective value or a rectified value of a transient response signal waveform of the circuit under test.
This is used as an index of the duration of the signal waveform of the transient response signal.

According to a fifth aspect of the present invention, there is provided the electronic circuit testing apparatus according to the first aspect of the present invention, wherein the microprocessor is configured such that an envelope of a transient response signal waveform of the circuit under test is within a preset range based on a response waveform of a normal circuit. It is to determine whether or not.

According to a sixth aspect of the present invention, in the electronic circuit inspection apparatus, the microprocessor extracts the frequency of the vibration waveform based on the peak time or the zero crossing time of the transient response signal waveform of the circuit under test, and This is to make a comparison with the vibration frequency.

According to a seventh aspect of the present invention, there is provided an electronic circuit inspection apparatus comprising: a pulse signal source for applying a pulse signal to a circuit under test; and an effective value or a rectified value of a transient response signal of the circuit under test with respect to the pulse signal. An analog-to-digital converter for performing an analog-to-digital conversion of an output signal of an effective value circuit or a rectifier circuit for performing an arithmetic operation, and comparing an output signal of the analog-to-digital converter with a determination value set based on a transient response signal of a normal circuit; And a display device for displaying a transient response signal waveform of the circuit under test or the normal circuit and a test result of the circuit under test.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION

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. Pulse signal source 15
Is for supplying a pulse signal to the circuit under test in order to perform the test, and the transient response of the circuit under test is
It is measured as a voltage waveform change from both ends of the secondary side 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 phenomenon 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 is
Due to the transformer induced phenomenon, a current change occurs on the secondary side 3b of the transformer, and a voltage waveform is measured 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 apparatus in FIG. 1, 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 and the microprocessor 12 After the arithmetic processing, the electrical connection failure of the diode 2 to be inspected 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 judgment 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 object to be inspected is not limited to this, but can be widely applied to electronic circuits 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 In the present embodiment, a specific method of calculating and determining a transient response waveform by the microprocessor 12 will be described. 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 the difference in the duration of the vibration waveform. In such a case, it is suitable to integrate the effective value or the rectified value of the transient response waveform and determine the difference in the duration of the vibration waveform based on the magnitude of the integrated value. Also,
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 and is performed as analog signal processing instead of the operation by the microprocessor 12, the operation of the microprocessor 12 The processing can be reduced, and the determination processing time can be reduced. Further, the processing of the response waveform can be performed at a higher speed than the processing performed by the 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. An abnormality in circuit connection is often accompanied by a change in resonance frequency. Therefore, by comparing and judging a vibration frequency of a normal circuit, a highly versatile abnormality inspection can be performed.

[0023]

According to the electronic circuit inspection apparatus according to the first and second configurations of the present invention, a pulse signal is applied to the circuit to be inspected, and the inspection is performed based on the resulting transient response signal waveform. Inspection of low-impedance circuits connected in parallel, which is difficult to judge by inspection by applying an AC small signal, is possible.

According to the electronic circuit inspection apparatus according to the third and fourth configurations of the present invention, the abnormality is determined by the duration of the vibration waveform of the transient response signal of the circuit under test, so that the versatile electronic A circuit inspection device can be provided.

According to the electronic circuit inspection apparatus according to the fifth and sixth configurations of the present invention, the abnormality is determined using the change generally occurring due to the abnormality of the circuit to be inspected as an index. An electronic circuit inspection device can be provided.

According to the electronic circuit inspection apparatus of the seventh aspect of the present invention, the arithmetic processing of the transient response signal waveform of the circuit under test is performed by the analog arithmetic processing circuit. You can save time. In addition, it is possible to perform a higher-speed response waveform calculation process as compared with a waveform calculation process by a microprocessor.

[Brief description of the drawings]

FIG. 1 is a measurement circuit diagram of an automatic electronic circuit inspection device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a waveform of a step signal output from a pulse signal source 15;

FIG. 3 is a diagram showing a waveform of a rectangular wave signal output from a pulse signal source 15;

FIG. 4 is a diagram showing an output transient response waveform measured on a secondary side 3b of a transformer 3;

FIG. 5 is a diagram showing an output transient response waveform measured on the secondary side 3b of the transformer 3.

[Explanation of symbols]

1 NPN transistor, 2 diode under test, 3a
Transformer primary side, 3b Transformer secondary side, 4 capacitors, 5 low resistance, 10 test equipment, 11 analog-digital converter (ADC), 12 microprocessor, 13 memory, 14 display, 15 signal source.

Claims (7)

[Claims] 1. A pulse signal source for applying a pulse signal to a circuit under test, an analog-to-digital converter for converting a transient response signal of the circuit under test to the pulse signal from analog to digital, and the digitally converted transient response signal And a microprocessor for comparing the determined value based on the transient response signal of the normal circuit with the determined value to determine the abnormality of the circuit under test. An electronic circuit inspection device comprising: a display device for displaying a circuit inspection result. 2. The electronic circuit inspection apparatus according to claim 1, wherein said pulse signal source generates a step pulse waveform or a rectangular pulse waveform. 3. The electronic circuit inspection device according to claim 1, wherein the microprocessor calculates a duration of a vibration waveform of a transient response signal of the circuit under test. 4. The microprocessor according to claim 3, wherein the microprocessor calculates an effective value or an integrated value of a rectified value of a transient response signal waveform of the circuit under test, and uses the integrated value as an index of a duration of the signal waveform of the transient response signal. The electronic circuit inspection device according to the above. 5. The electronic circuit according to claim 1, wherein the microprocessor determines whether an envelope of a transient response signal waveform of the circuit under test falls within a preset range based on a response waveform of a normal circuit. Inspection equipment. 6. The microprocessor according to claim 1, wherein the microprocessor extracts a frequency of the vibration waveform based on a peak time or a zero-cross time of a transient response signal waveform of the circuit under test, and compares the frequency with a vibration frequency of a normal circuit. Electronic circuit inspection equipment. 7. A pulse signal source for applying a pulse signal to a circuit under test, and an output signal of an effective value circuit or a rectifier circuit for calculating an effective value or a rectified value of a transient response signal of the circuit under test with respect to the pulse signal. An analog-to-digital converter for performing an analog-to-digital conversion; An electronic circuit inspection apparatus comprising: a processor; and a display device for displaying a transient response signal waveform of the circuit under test or a normal circuit and a test result of the circuit under test.