JPH0697254B2 - Circuit board inspection method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a circuit board inspection method, and more particularly to a novel inspection method for an in-circuit tester.

[Conventional example]

In the inspection of the circuit board by the in-circuit tester, a board fixing device called a fixture is used. Many probes corresponding to the measurement points of the circuit board to be inspected are implanted in this fixture, and while the measurement signal is given through the probe, the response signal is detected and, for example, a non-defective product pre-absorbed from a non-defective board. By comparing the data with the detection signal, the quality of the circuit board is determined. That is, basically, a specific probe is connected to a measurement signal source, and a detection signal is obtained from a predetermined probe corresponding to it.
There are several ways to do this.

Brute force method: This tests all between each probe, for example 4 resistors as shown in FIG.
When testing the network of R1 to R4, AB, AC, AC
Each test step of D, B-C, B-D, and C-D will be taken.

Short and open group tests:
When absorbing good product data from a good board, create a group of probes below a certain level (short group) for a specific probe, and at the time of inspection, the probes within that group are below a certain level and other groups When it is open between and, it is judged as a good product.

Pin-to-pin test: Especially when there are single items such as L, C, R,
Measure between the probe pins. As for the example of FIG. 2, the test between AB, BC, CD, DA is performed.

[Problems to be solved by the invention]

The above-mentioned brute force method is relatively simple in terms of program, but the number of measurement points increases as the number of measurement points increases, resulting in a lack of high speed. On the other hand, a short of
Opening is fast to some extent, but if it is determined to be defective, the existence of the defective component is difficult to grasp and it is inconvenient for repair. According to the pin-to-pin test at that point, the position of the defective part can be accurately grasped and it is convenient for repair, but the program is complicated and the design takes a lot of time and effort. In that case, the first problem is that the program creator knows not only the measurement method but also the properties and characteristics of the part to be measured. It means that it cannot be created.

The present invention has been made in view of the above conventional circumstances,
An object of the invention is to provide a circuit board inspection method which does not require complicated program design and can inspect a large number of measurement points at high speed.

[Means for solving problems]

In order to achieve the above-mentioned object, in the present invention, a plurality of (N) probes that come into contact with a measurement point of a circuit board to be measured, and a measurement signal source that supplies a measurement signal to the circuit board to be inspected via the probes And a signal detecting section for detecting a response signal output from the circuit board side to be inspected through the probe, and switching means for connecting the probe to either the measurement signal source or the signal detecting section. In the circuit board inspection method for determining the quality of the circuit board to be inspected by comparing the detection signal output from the signal detection unit with a predetermined reference signal, N-1 of the probes are used as the measurement signals. The impedance of each measurement point is measured by connecting it to the source and connecting the remaining one to the above-mentioned signal detection part and doing this for each probe. It is characterized by determining the quality with the value of the impedance.

[Action]

Prior to the inspection, non-defective product data (reference data) serving as a determination reference is taken in from the non-defective product substrate. This data acquisition work is performed by switching the probe as described above.
The impedance is measured for each of the measurement points and its value is stored in memory. In this way, it is preferable to absorb data from a plurality of non-defective substrates and average them to determine non-defective data as a criterion.

Then, the actual board inspection is started. That is, the probe is applied to each measurement point on the circuit board to be inspected, and the probe is switched in the same order and under the same conditions as when the non-defective product data is absorbed, and the impedance at each measurement point is measured. Then, the measured impedance value and non-defective product data are compared to determine whether the measured impedance value is within the allowable range.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the schematic diagram shown in FIG.

The figure shows four probes 1 to 4 corresponding to the respective measurement points A to D of the circuit network of FIG. That is,
The probe 1 is implanted in a fixture pinboard (not shown) so as to correspond to measurement points A, 2 to B, 3 to C, and 4 to D, respectively. Each probe 1
There are two changeover switches 1a, 1b; 2a, 2b;
3a, 3b; 4a, 4b are connected in parallel. Each probe 1
Reference numerals 4 to 4 are connected to the measurement signal source, for example, an AC power source 5 via one of the switches 1a, 2a, 3a and 4a. Also,
Each of the probes 1 to 4 is connected to the signal detector 6 via the other switch 1b, 2b, 3b, 4b. In this embodiment, the signal detection unit 6 is composed of a current-voltage converter. An A / D converter 8 is provided on the output side of the signal detector 6 via an amplifier 7.
Is connected, and the converted data is processed by the CPU (central processing unit) 9. Also, the switches 1a to 4b are also connected to the CPU 9
It is controlled by.

According to the present invention, the board inspection is performed as follows. First, non-defective data used as a criterion is obtained from non-defective substrates. That is, a non-defective substrate is set in a fixture (not shown), and a pressing device (not shown) is also operated to set the probes 1 to 4 to measurement points A to D of the non-defective substrate.
Contact. And the switches 1a to 4a on the AC power supply 5 side
Among them, the switch 1a is “open”, the other switches 2a to 4a are “open”, and the switch 1b on the signal detector 6 side is
Of 4b, switch 1b is "closed", other switches 2b-4b
Is "open". As a result, the measurement points B, C, and D have the same potential, and only the measurement point A has a low potential with respect to them. Therefore, in this example, current flows from the measurement points B and D toward the measurement point A. become. This current is converted into, for example, a voltage by the signal detector 6, amplified by the amplifier 7 in a predetermined manner, and then converted into digital data by the A / D converter 8. This data is the impedance at the measurement point A of the non-defective board, and the CPU 9 stores this non-defective data in the memory 10 as reference data of the measurement point A. Next, of the switches 1a to 4a on the AC power supply 5 side, the switch 2a is "open" and the other switches 1a, 3a, 4a are "closed".
In addition, among the switches 1b to 1d on the signal detector 6 side, the switch 2b is “closed” and the other switches 1b, 3b, 4b are “open”. As a result, the impedance at the measurement point B is detected and the data is stored in the memory 10 as reference data at the point B. Thereafter, the impedances at the measurement points C and D are obtained in the same manner, and the data is stored in the memory 10 as the reference data at the points C and D. In this way, the good product (reference) data as the determination reference is absorbed from the good product substrate, but it is preferable to obtain the data from a plurality of good product substrates and use the average value thereof.

After that, the circuit board to be inspected is set on the fixture and the board inspection is performed. That is, the switch 1a on the side of the AC power supply 5 according to the same switching order as described above.
4a and switches 1b to 4b on the side of the signal detector 6 are switched to measure the impedance at each measurement point A to D of the circuit board to be inspected, and the measured data is stored in the CPU 10 in the memory 10. The reference data is compared. In this case, the reference data has a predetermined range, if the measurement data is within the range, "GO" is displayed on the display device 11 such as a CRT to indicate that the inspection has passed, and if the measured data is out of the range, the defective product is defective. Is displayed, for example, “NG” is displayed.

Although an AC power supply is used as the measurement power supply in the above embodiment, it may be a DC power supply. Further, although the comparison reference value is obtained from the non-defective substrate, in some cases, for example, data at the time of design or data described in the specification may be used.

〔The invention's effect〕

As described above, according to the present invention, of the N probes, (N-1) probes are connected to the measurement power source side, and the operation of switching the remaining one probe to the signal detector side is performed. Since the impedance at each measurement point is detected repeatedly and the pass / fail judgment is made based on that value, the pin number of the probe corresponding to each mounted component can be specified as in the past, and depending on the case, which It is not necessary to compose a complicated program such as whether to use a guard pin or the like, and even a person who does not have much knowledge about the measuring method of each component can inspect the board. Further, since the determination is made for each measurement point, the location of the defective portion can be known accurately, and the effect is remarkable.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining the present invention, and FIG. 2 is a circuit diagram showing an example of a circuit to be inspected. In the figure, 1 to 4 are probes, 5 is a measurement power source, 6 is a signal detector, 8 is an A / D converter, 9 is a CPU, and 10 is a memory.

Claims (1)

[Claims] 1. A plurality of (N) probes contacting a measurement point of a circuit board to be measured, a measurement signal source for supplying a measurement signal to the circuit board to be inspected through the probes, and the circuit board side to be inspected. A detection unit that includes a signal detection unit that also detects the response signal that is output via the probe and a switching unit that connects the probe to either the measurement signal source or the signal detection unit, and outputs the detection signal from the signal detection unit. A circuit board inspection method for determining the quality of a circuit board to be inspected by comparing a signal with a predetermined reference signal, wherein N-1 of the probes are connected to the measurement signal source and the remaining Connect one to the signal detector, and do this for each probe to measure the impedance at each measurement point. A method for inspecting a circuit board, which comprises determining.