JPS5899768A - Detecting device for short-circuiting place in substrate pattern - Google Patents

Abstract

PURPOSE:To detect a short-circuiting place in a pattern by applying a signal current to a circuit pattern from a low-frequency oscillator, and by detecting a magnetic flux by a detecting coil. CONSTITUTION:Output terminals 9 and 10 from a low-frequency oscillator 8 are connected to the component terminal insertion holes 6 and 7 of a pattern to be inspected on a printed wiring substrate, respectively, and then a detecting coil 15 connected to a level detector 11 is approached to patterns 12 and 13 on the printed wiring substrate. While a pointer of the level detector 11 being watched, the coil 15 is moved along the short-circuiting patterns on the substrate 14 to be inspected. Then, a signal current flows through places a b c f g of the short-circuiting patterns 12 and 13 and a magnetic field is generated around the sections. Thus, a short-circuiting place (c) can be found simply in a short time without damaging the substrate to be inspected at all by the detecting coil 15.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pattern short-circuit detection device on a printed circuit board. The output can be easily detected by connecting the output to the board to be inspected and searching with a detection coil and a level detection section.

Conventionally, methods for detecting unnecessary short circuits caused by bridges or incorrect wiring on printed circuit boards include:
Measure the resistance by visual inspection, or by peeling off a part of the pattern resist on the printed circuit board to be inspected as shown in Figure 1, and first applying the gloves 4 and 5 of the resistance value measuring device 3 to that part 1.2. Measure and then measure another one on the wiring pattern again.
- Peel off a part of the resist (2' in Figure 1) and measure the resistance value between the patterns using the same measuring method as above,
If the value at this time is smaller than the previous measured value, it means that you are approaching an unnecessary short circuit, so a method such as repeating this process many times to pinpoint the short circuit is performed. ing. -However, these methods produce complex patterns.

When the time comes, a great deal of time and effort is required. In addition, in the method of measuring the resistance value, since the absolute value of the resistance value itself is small, it is necessary to take into account errors caused by the way the pulleys are connected, and in order to obtain accuracy. This method is problematic in practice because it requires a dog and a large amount of money. Furthermore, when using this method, it is necessary to peel off the patterned resist, so it is inevitable that the printed wiring board to be inspected will be damaged. In some cases, it may be necessary to cut the pattern, which may result in major damage, making it extremely difficult.

In view of the above point 5, the present invention provides a device that can easily detect short circuits that cause distortion occurring on a wiring board for a short period of time without damaging the board. An embodiment of the present invention will be explained using FIGS. 2-4.

As an example of the present invention is shown in FIG. 2, after connecting the output terminals 9p and 10 from the low frequency oscillator 8 to the component terminal insertion holes 6°-7 of the pattern to be inspected on the printed wiring board, the level detector Detection coil 15 connected to pattern 11 is brought close to patterns 12 and 13 of the printed wiring board. Then, while watching the needle of the level detector 11, the coil 16 is traced along the short circuit pattern on the board 14 to be inspected. In the above configuration, the board to be inspected 14 is short-circuited by the output of the oscillator 8, and the a-b-c-f-
A signal current flows through g, and a magnetic field is generated around it. Here, a7b-d, e-f-g are copper foils that are originally necessary, and are unnecessary layers that create a short circuit. Therefore, when the detection coil 16 is brought close, the magnetic flux passing through the coil 15 changes, and an electromotive force is generated due to electromagnetic induction phenomenon. The relationship between the magnetic field generated by the current flowing on the short circuit pattern and the electromotive force generated in the detection coil 16 will be explained. When a current flows through the conductor J as shown in Figure 3, the magnetic field H at a point a distance r from the conductor J is H-I/2πr ('/m)...
......(1). In this magnetic field, the detection coil 1
5, the electromotive force E generated in the detection coil 16 becomes as shown in FIG. On the other hand, the electric current of equation (1) is lm5inωt ・・・・・・・・・・・・
...(3), equation (1) becomes H=lm5inωt//2. .

Then, when we differentiate this with respect to t, we get: From this, when we substitute equation (6) into equation (2), we get E
Knee・Inω・cosωt/2zr −・・・・・・
......(6).

- From this equation (6), since the oscillation frequency of the oscillator 8 is constant (ω - constant), - the electromotive force generated in the detection coil 16 is the distance r between the detection coil 16 and the conductor (copper foil). is inversely proportional to. That is, the closer the detection coil 1-5 is to the short-circuit pattern ya-b-c-f-g in FIG. 2, the more the electromotive force increases. Then, the meter of the level detector 11 connected to the detection coil 15 fluctuates greatly. For example, as shown in FIG. 2, when the detection coil 16 is moved from point a to direction b while looking at the detector 11 along the pattern on the board to be inspected 14, it passes the zero point and moves toward point d. , where the detector 110 level decreases. This shows that the 0 point is connected to the gfe pattern.

This eliminates unnecessary bridges between patterns.

It is possible to determine the short-circuit location C due to incorrect wiring or the like. Furthermore, according to this method, it is also possible to detect short circuits caused by thin whiskers on a pattern that are difficult to see with the naked eye.

As described above, according to the present invention, it is possible to easily find unnecessary short circuit parts on a wiring board in a short time and without damaging the board to be inspected, which is extremely valuable in practice. It's expensive, yes.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining a conventional method for detecting a short circuit on a wiring board, FIG. 2 is a block diagram of a circuit board pattern short circuit detection device according to an embodiment of the present invention, and FIG. The figure is a diagram for explaining the relationship between the magnetic field and distance caused by a current flowing through a conductor, and FIG. 4 is a diagram for explaining the relationship between the magnetic field and electromotive force. 6, 7... Conductive pattern component terminal insertion hole, 8...
...oscillator, 9*10...oscillator output terminal,
11...Lehel FJ Outer, 12. '13...
... Pattern, 14 ... Board to be inspected, 16
゛...Detection bow il. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
figure

Claims (1)

[Claims] The mutually independent first . The second pattern is composed of an oscillator having connection terminals connected to respective arbitrary points of the second pattern, and a level detector having a coil for detecting the oscillation signal from the oscillator and displaying the electromotive force generated in the coil; Connect the connection terminal of the oscillator to the first. A circuit board pattern short-circuit detection device, which is connected to two arbitrary locations on a second pattern, and detects the presence or absence of the oscillation signal by applying the oscillation signal to the pattern of the printed circuit board using the coil.