JPS59125694A - Through hole inspecting device for printed board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (1) 1 Technical Field of the Invention The present invention detects defects by inputting and diffusing light into the substrate material of a printed circuit board and detecting the diffused light leaking from the defective portion of the through hole into the through hole. This invention relates to a through-hole inspection device for printed circuit boards.

(2) Background of the Technology The through-hole plating method is widely used for connection between the front and back conductors of a double-sided printed board or for connection VC of interlayer conductors of a multi-node Y printed board. In this through-hole coating method, holes are pre-drilled in an insulating substrate on which all conductors are laminated, and a chemical or electrical (C plating layer is formed on the inner wall surface of the hole) to create an "electrical connection" between the conductors. Although it is a thing,
The plating layer has a thickness on the order of microns, the inner wall surface of the through hole is extremely uneven, and the diameter is small, so defects such as pinholes and cuts often occur in the plating layer that forms the through hole. Large defects in the plating layer lead to poor electrical continuity between conductors, which poses a major problem in terms of reliability of the printed board. Therefore, it is important to be able to easily and reliably inspect such through-hole defects.

(3), Prior Art and Problems Conventionally, in the through-hole inspection method for printed circuit boards, one side of the printed board is illuminated by a light source, and the diffused light enters the board material and passes through the through-hole defects. By detecting the transmitted light using a photodetector installed on the opposite side of the printed board, the presence or absence of defects was fully inspected.

However, in the conventional method as described above, although it is possible to determine whether there is a defective portion in the through hole or not, it is not possible to determine where in the through hole the defective portion is located.

(4) 0 Purpose of the Invention The present invention solves all of the above-mentioned conventional problems, and is a through-hole inspection device for printed circuit boards that is capable of detecting not only the presence or absence of a defective part in the through-hole, but also the position of the defective part. The purpose is to provide

(5) 6 Structure of the Invention In order to achieve the above object, the printed board through-hole jaw inspection device of the present invention provides illumination with mutually different wavelengths that illuminates the upper and lower surfaces of the printed board and the outer periphery of the through-hole separately. A light source, a light detection means for separately detecting both light and its amount when the light incident and diffused into the inside of the substrate material from each of the illumination light sources leaks into the through hole; and circuit means for determining the position of the defect within the through hole based on a signal corresponding to the amount of light.

(6) Examples of three inventions Embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows an example of a printed board through-hole inspection device according to the invention, in which 1 is a printed board to be inspected, and a substrate material 2 constituting this printed board 1 is made of, for example, glass fiber and epoxy. It is made of a light-transmissive material impregnated with resin, and a plated layer 3 is formed on the inner wall of a through hole 2a drilled in the substrate material 2, thereby forming a front and back conductor (land portion) 4.
A through pole 5 is formed to electrically connect the two.

A filter 6 that masks the lower end opening of the through hole 5 is disposed on the lower surface side of the printed board 1, and this filter 6 only transmits light of a specific wavelength, for example, blue light. be. On the side where the filter 6 is disposed, there is a defect detection light that emits both light (e.g., blue) that passes through the filter 6 and light of a wavelength that does not pass through the filter 6 (e.g., red light). A device 7 is provided, and of the light emitted from the illumination device 7, the positive and colored light that passes through the filter 6 enters the through hole 5 and becomes light for detecting the through hole position. The red light that is not blocked by the filter 6 is irradiated onto the back surface of the substrate material 2 as illumination light that illuminates the entire surrounding area of the through hole. Reference numeral 8 denotes an illumination light source for defect detection, which is located on the upper surface side of the printed circuit board 1 and illuminates the upper surface of the substrate material 2 located around the through hole 5. It emits light of a different wavelength from the irradiation light of the illumination device 7, for example, green light. Reference numeral 9 denotes a truncated conical cylindrical light shielding member disposed in a central portion surrounded by the illumination light source 8 so as to face the through hole 5; this light shielding member 9 prevents the irradiated light from the illumination light source 8 from entering the through hole 5 This is to prevent it from entering. 10 (is a lens that focuses the light emitted from the through hole 5, and this lens 10
On the rear optical axis, there are a color separation filter 11 that transmits green and red light and separates the blue light by total reflection, and a color separation filter 12 that transmits the green light sound and reflects and separates the red color. A photodetector 13 is installed on the reflected optical axis of the color separation filter 11 to detect the position of the through hole 5 by detecting blue light. The output signal is applied to one input terminal of the comparator 14, and the reference potential Vr is applied to the other input terminal of the comparator 14. Further, a photodetector 15 is installed on the reflected optical axis of the color separation filter 120 to detect a defect in the lower part of the through hole 5 by detecting red light. A photodetector 16 is installed on the transmitted optical axis to detect a defect in the upper part of the through hole 5 by detecting green light. The output signals are sent through separate buffer amplifiers 17 and 18'e to analog/digital converters (hereinafter referred to as A/D converters).
19.20, and two comparators are connected to both A and /D converters 9.20, which compare the magnitudes of their output signals and determine the extent of defects. The output signal of the comparator 2J is input to the defect position display section 22. Further, the comparator 21 is provided with an output signal from the comparator 14 as an operation command, and operates only when the through hole 5 is detected. Furthermore, stage position information S is added to the defect position display section 22 from an X-Y stage control means (not shown).

Next, the operation of this embodiment configured as described above will be explained.

One of the through holes 5 of the printed board 1 has an X-
When the red, blue, and green lights from the illumination device 7 and the illumination light source 8 are irradiated onto both the upper and lower surfaces of the printed board 1 while the Y stage is indexed to the inspection position, the printed board 1 is
The red light 7a and green light 8a incident on the inside of the substrate (second interior) are diffused. However, the light intensity distribution in the thickness direction within the substrate material 2 due to this has the characteristic that it is largest on the lower surface side of the substrate material 20 and decreases linearly as it goes toward the upper surface side +fC, as shown by the solid line l in Fig. 2. Similarly, the light intensity distribution in the thickness direction within the substrate material 2 due to the green light 8aV is largest on the upper surface side of the substrate material 2, as shown by the broken line H in FIG. 2, and decreases toward the lower surface side. Therefore, it exhibits a linearly decreasing characteristic.

On the other hand, if the through hole 5 is indexed to the inspection position, the blue light 7b transmitted through the filter 6 will be transmitted through the through hole 5.
After passing through the blue light and being focused by the lens 10, it is reflected by the color separation filter 11 toward the blue light detector 13, and the light detector 13 converts the blue light into a negative signal. By adding 4 VC to all comparators, it is determined that the through pole 5 is at the inspection position, and a signal is sent from the comparator 4 for comparison. Set U21 to the operating state.

In such a state, if there is a defective part 3a in the lower part of the inner wall of the through hole 5 indexed at the inspection position i, the red and q green lights incident and diffused into the substrate material 2 will have the light intensity shown in FIG. The light enters the through hole 5 from the lower defective portion 3a according to the distribution characteristics (1) and (H). Among these, the red light passes through the lens element 0 and the color separation filter element 1, and then is reflected by the color separation filter 12 toward the photodetector 15, where it is converted into an electrical signal according to the amount of light, and After being amplified by the buffer amplifier 17, it is converted into a digital signal by the A/D converter 19. On the other hand, after the green light passes through the lens 10 and the color separation filters 11 and 1.2, it is detected by the photodetector 6 and converted into an electrical signal according to the light amount V, which is sent to the buffer amplifier 18 and sent through the A/D. converter 2
0 and converted to a digital quantity.

At this time, as is clear from the light intensity distribution characteristics shown in FIG. / larger than the value of signal B output from D converter 20. As a result, comparator 2 is more sensitive to signal B than it is to signal B.
It is determined that the hole is too thick, the entire LIK signal is sent out from the output line, and this signal is added to the defect position display section 22, thereby indicating that there is a defective portion 3a at the bottom of the through hole 5.

If the defective part 3a is located at the upper part of the inner wall of the through hole 4 (because the amount of green light is larger among the light that passes through the entire defective part 3a and enters the through hole 5, The values of the signals A and H converted into digital quantities by the p and '/D converters 19 and 20 according to this light intensity become A<B. As a result, when the comparator 21 determines that A<B, A signal rl is sent to the output line L2, and by adding this signal to the defect position display F!1322, it is indicated that there is a defective portion 3a on the upper part of the inner wall of the through hole 5.

Furthermore, when the defective part 3a is located in the middle of the through hole 4, the amounts of red and green light that pass through the defective part 3a and enter the through hole 5 are almost equal, and accordingly The signal levels converted by the photodetectors 515.16 are approximately equal. Therefore, when both of these analog signals are converted into digital quantities by the respective A/D converters 9 and 20 and then applied to the comparator 21 V, the comparator 21 determines that idA=B and outputs the output line L3. At the same time as the signal is sent out, the defect position display section 22 displays that the defective portion 3a is located in the middle of the through hole 5.

Therefore, according to this embodiment having the above-mentioned configuration, it is possible to detect not only the presence or absence of a through-hole defect but also the position where the defect occurs.

Note that it goes without saying that the means for determining the defect position in the present invention is not limited to the circuit system shown in the above embodiment.

(7) As described in detail in 1 of the invention, according to the present invention, the upper and lower surfaces corresponding to the through holes of the printed board are illuminated with illumination light having different wavelengths, and this illumination light passes through the inside of the board material and enters the through holes. Since it is designed to detect the entire difference in the amount of light when it leaks, it is possible to detect not only the presence or absence of a defective part within the through-hole, but also the position of the defective part.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a printed board through-hole inspection apparatus according to the present invention, and FIG. 2 is a characteristic diagram of light quantity distribution in the thickness direction of a printed board substrate material according to the present invention. Explanation of the symbols 1 is pudding)ffl, 2 is the substrate material, 3 is the plating layer, 3a
li defect part, 5 is a through hole, 6 is a filter, 7 is an illumination device, 8 is an illumination light source, 1o lens, 11.12 is a color separation filter, 13 is a photodetector for detecting the position of the through hole, 14 is a comparator , 15 is a lower defect detection photodetector, 16 is an upper defect detection moonlight detector, 19.20 is A/
A D converter, 21 a comparator, and 22 a defect position display section. Patent applicant Fujitsu Limited

Claims (1)

[Claims] Illumination light sources with different wavelengths that separately illuminate the outer circumference of the through hole from the top and bottom surfaces of the printed board, and both lights when the light that is incident and diffused into the board material from each of the above illumination light sources leaks into the through hole. A through-hole in a printed board, comprising a light detection means for detecting the amount of light and a light amount separately, and a circuit means for determining the entire position of a defect in the through-hole based on a signal corresponding to the light amount from the light detection means. Inspection equipment.