JPS638432B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a circuit board insulation testing method and apparatus for detecting the mutual insulation state of circuit patterns constituting a predetermined circuit provided on a circuit board.

Generally, a circuit board such as a printed wiring board has a large number of conductive circuit patterns 1, 2,
3...n are adjacent, and adjacent circuit patterns may be short-circuited due to defects in the manufacturing process. Therefore, it is necessary to detect short-circuit defects.

In the past, these short-circuit failures were detected visually or manually using a tester, but as electronic equipment becomes more highly integrated, the circuit patterns on printed wiring boards become more dense, and smaller precision equipment becomes more dense. Due to computerization, printed wiring boards with minute high-density wiring are being mass-produced in a wide variety of types. For this reason, it has become impossible to detect unnecessary points by visual inspection, and methods and devices for detecting short-circuit points using electrical automatic calibration means have been devised and put into practical use.

FIG. 2 shows an insulation test circuit diagram as an example of the configuration of a conventional defect detection means, where T is a measurement circuit, P ₁ ,
P ₂ ...Pn are detection probes corresponding to circuit patterns 1, 2, ... n on the circuit board shown in Fig. 1, S ₁ , S ₂ ...Sn are detection probes P ₁ , P ₂ , ...
...It is a circuit changeover switch in which switching contacts d ₁ , d ₂ ...dn are connected to Pn, respectively, and fixed contacts b ₁ , b ₂ ...
...bn is connected to one terminal A of the measurement circuit T,
The fixed contacts C ₁ , C ₂ ...Cn are connected to the other terminal B of the measuring circuit T, and the open contacts a ₁ , a ₂ ...an, which are always in contact with the switching contacts d ₁ , d ₂ ...dn, are connected to the other terminal B of the measuring circuit T. have.

With this configuration, when performing an insulation test between two circuit patterns, detection probes P ₁ , P ₂ are used for circuit patterns 1, 2...n on the circuit board.
...Pn is brought into contact with the circuit changeover switches S ₁ , S ₂ ...
...Switch one of Sn so that switching contact di contacts fixed contact bi, and switch operation so that detection probe pi is connected to terminal A, and the detection probe to which terminal A is connected comes into contact. Using the circuit pattern as a reference, switch all other independent circuit patterns sequentially so that the contact di contacts the fixed contact ci, connect it to the B terminal, and connect it to the measurement circuit T. By detecting the insulation state between the AB terminals, short circuits between the reference circuit pattern and all other patterns can be detected. Similarly, by sequentially connecting a reference circuit pattern to terminal A and, in each case, sequentially connecting an independent circuit pattern other than the reference circuit pattern to terminal B, an insulation test between all circuit patterns can be performed. In this case, in order to avoid duplication of insulation tests between circuit patterns, a unique address 1, 2...n is assigned to each detection probe, and n-1, n-2,... …Insulation test up to 1, n-2, n- for address n-1
It is sufficient to always perform the insulation test toward lower addresses, such as the insulation test up to 3...1.

However, such conventional insulation testing methods have the following drawbacks.

(b) First, it is necessary to perform the operation of selecting and testing all circuit patterns with a changeover switch for any reference circuit pattern for each independent circuit pattern. If there are N, the number of switching operations reaches NC ₂ =N(N-1)/2. For example, if N=200, 19,900 switching operations are required, resulting in an enormous amount of time and complicated operations. In addition,
If the changeover switch is configured with a semiconductor switch,
Although it is possible to shorten the time, it is difficult to significantly shorten the time due to the capacity of the printed wiring board and the running time of the control program.

(b) Also, the number of changeover switches required is equal to the number of independent circuit patterns, and in the case of semiconductor switches in particular, they are generally not bidirectional, so two switches are required for each direction of current flow per circuit pattern. Including the circuits to control these switches required a large amount of cost.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method and apparatus for testing the insulation of a circuit board, which solves the above-mentioned drawbacks and can be tested at low cost, easily operated, and in a short time.

According to the present invention, a so-called 4-color classification method is used, in which a plane divided into several figures can be painted in at least four colors if adjacent figures are always painted in different colors. All circuit patterns on the map that have the same shape as the circuit patterns on the circuit board are classified by four colors, and insulation inspection is performed between the circuit patterns on the circuit board that correspond to the circuit patterns classified in different colors. A second circuit pattern that is adjacent to the first circuit pattern among the circuit patterns on the map and has a possibility of shorting with the first circuit pattern is colored in a different color from the first circuit pattern. Next, a third circuit pattern that is adjacent to the second circuit pattern and excluding the first circuit pattern that has the possibility of short circuit with the second circuit pattern is colored differently from the first and second circuit patterns. color, then adjacent to the third circuit pattern and the third
The first and second circuit patterns have the possibility of short circuit.
The fourth circuit pattern excluding the circuit pattern is colored differently from the first, second, and third circuit patterns, and all the circuits on the circuit board corresponding to the circuit patterns of the same color on the above map are colored. The pattern is short-circuited to form one test terminal, and the insulation test is sequentially performed between two of the four terminals.

Next, one embodiment of the present invention will be described with reference to FIGS. 3 and 4. Figure 3 is a diagram of the circuit pattern of the printed wiring board shown in Figure 1, with circuit patterns 1 and 2.
...A part of n is classified using four colors, and in the diagram, the diagonal lines represent red, the horizontal lines represent blue, the grid represents green, and the white background represents yellow. Circuit patterns can always be classified using different colors, such as red and blue, or green and blue. For example, circuit patterns 2, 3, 4, 6, 7, and 8 are likely to cause a direct short circuit to circuit pattern 1, which is classified in red, and these are all classified in colors other than red. In the circuit pattern, 2 and 7 have no possibility of being directly short-circuited, so they are classified with the same yellow color, but 2 and 3 and 2 and 4 have the possibility of being directly short-circuited, so they are classified in colors other than yellow and red. 3 and 4 are also classified in blue and green because they need to be classified and there is a possibility that they may be directly shorted. Furthermore, since there is no possibility that circuit pattern 5 will be directly short-circuited with circuit pattern 1, it may be classified using the same red color as circuit pattern 1.

FIG. 4 shows an example of an insulation test circuit according to the present invention, and T indicates measurement circuits P ₁ , P ₂ . . . P ₁₂ indicate portions 1, 2 .
...12 and circuit patterns 1, 2 in Fig. 3...12
These are the detection probes corresponding to each. Fixed contacts _{b 1} , b ₂ of circuit changeover switches S 1 , S ₂ , S ₃ , S ₄ ,
b ₃ and b ₄ are connected to terminal A of measurement circuit T, fixed contacts C ₁ , C ₂ , C ₃ and C ₄ are connected to terminal B of measurement circuit T, and switching contacts d ₁ and d ₂ are connected to terminal B of measurement circuit T. , d ₃ , and d ₄ are always in contact with the open contacts a ₁ , a ₂ , a ₃ , and a ₄ . Furthermore, the switching contact _{d 1} of the circuit switching switch S 1 is electrically connected to the detection probes P ₁ , P 5 , and P 11 corresponding to the circuit pattern groups 1, ₅ , and ₁₁ classified in red in FIG. Therefore, P ₁ , P ₅ , and P ₁₁ are always shorted. Similarly, switching contact d ₂ connects d ₃ to the detection probe group corresponding to the circuit pattern group classified in yellow.
is electrically connected to the detection probe group corresponding to the circuit pattern group classified in blue, and _d4 is electrically connected to the detection probe group corresponding to the circuit pattern group classified in green, and is classified by the same color. The detection probe groups corresponding to the circuit pattern groups that have been detected are always in a short-circuited state.

With the above configuration, when performing an insulation test between circuit patterns, all detection probes P ₁ , P 2 ...P ₁₂ corresponding to circuit patterns 1, ₂ ... 12 on the printed wiring board in Fig. 1 are contacted. Then, short-circuit all the circuit patterns on the printed wiring board that correspond to the circuit patterns of the same color on the diagram in Figure 3 to form one test terminal, and connect the circuit changeover switch S ₁ in the same way as the conventional insulation test circuit. , S ₂ , S ₃ , and S ₄ to connect two of the four terminals to the measuring circuit T in sequence. For example, contact contact piece d ₁ of circuit initial switch S ₁ with fixed contact piece b ₁ and connect all detection probe groups corresponding to circuit pattern groups classified in red to terminal A of measurement circuit T. , then the switching contacts di of circuit changeover switches S ₂ , S ₃ , and S ₄ are fixed contacts.
By sequentially operating the detection probes corresponding to the circuit pattern groups classified as yellow, blue, and green so that they are in contact with terminal B and detecting the insulation state between both terminals A and B, red It is possible to perform insulation tests between circuit patterns classified by , and circuit patterns divided by blue, yellow, and green. Similarly, if the insulation test is performed on the combination of two circuit pattern groups from among the four circuit pattern groups, then the printed wiring board corresponding to all the circuit patterns colored on the map in FIG. This means that all insulation tests have been performed between two circuit patterns that are adjacent to each other and have the possibility of being directly short-circuited.

In this embodiment, the circuit changeover switch has been described as a mechanical switch, but it goes without saying that it may be constructed as a semiconductor switch.

As described above, in the present invention, regardless of the number of independent circuit patterns on a circuit board to be inspected for insulation, four
In order to conduct an insulation test between circuit pattern groups classified as
₄ C ₂ =6 times is enough, and the time required for the test is dramatically shortened compared to the conventional insulation testing method, and the operation is also extremely easy. For example, when the number of independent circuit patterns is 200, the time required for testing is 4C ₂ /200C ₂ =6/19900. In addition, compared to the conventional insulation testing method, which required as many circuit changeover switches as the number of independent circuit patterns, the present invention requires only four switches (eight in the case of semiconductor switches), which reduces the cost of parts constituting the test circuit. is significantly reduced. Furthermore, if the circuit changeover switch is replaced with a semiconductor switch and the switching operation is performed automatically, there is an advantage that the circuit for controlling the group of these switches can be of a simple configuration.

In the above explanation, the present invention was applied to the insulation inspection of printed wiring boards. The present invention can also be widely applied to plates and the like. In addition, in this example, insulation inspection of a printed wiring board with a circuit pattern on one side was explained, but even in the case of a printed wiring board with circuit patterns on both sides and conduction through through holes, all circuit patterns can be divided into four pattern groups. It is possible to design a printed wiring board in such a way that circuit patterns that have the possibility of directly shorting each other when classified as such belong to different pattern groups, and that the insulation testing method of the present invention can also be applied to double-sided printed wiring boards. Of course.

[Brief explanation of the drawing]

Figure 1 is an example of a circuit pattern of a general printed wiring board, Figure 2 is a schematic diagram of the configuration of a conventional insulation test circuit,
Figures 3 and 4 are explanatory diagrams of the present invention, and Figure 3 is a circuit pattern map of a printed wiring board classified in four colors: diagonal lines are red, horizontal lines are blue, white backgrounds are yellow, and grids are Figure 4 shows the insulation test circuit. Codes in the figure: 50... Insulating substrate, 1, 2, 3...
...12: Circuit pattern, P ₁ , P ₂ ... Pn: Detection probe, S ₁ , S ₂ ... Sn: Circuit changeover switch, a ₁ ,
a ₂ ... an: Fixed contact piece, b ₁ , b ₂ ... bn: Fixed contact piece,
C ₁ , C ₂ ... Cn: Fixed contact piece, d ₁ , d ₂ ... dn: Switching contact piece, T: Measuring part, A, B: Terminal.

Claims (1)

[Scope of Claims] 1. A first circuit pattern of a circuit board, a second circuit pattern having a short circuit possibility with the first circuit pattern, and a second circuit pattern having a short circuit possibility with the second circuit pattern. A third circuit pattern excluding the first circuit pattern, and a fourth circuit pattern excluding the first and second circuit patterns that may have a short circuit with the third circuit pattern. Short-circuit each terminal and consider each terminal as one test terminal.
A circuit board insulation testing method characterized by sequentially testing insulation between two of four terminals. 2. It has at least four circuit changeover switches, a measurement circuit that detects the insulation state between two terminals, and a number of detection probes corresponding to the circuit patterns to be tested on the circuit board, and detects circuit patterns that may have a short circuit. 1. An insulation testing device for a circuit board, characterized in that when the circuit board is separated into at least four circuit patterns, detection probes corresponding to the four circuit patterns are short-circuited.