JPH0442622B2 - - Google Patents

Description

[Detailed Description of the Invention] (1) Technical Field of the Invention The present invention relates to a through-hole inspection method and apparatus for optically detecting defects such as pinholes occurring on the inner wall of the through-hole of a printed board. .

(2) Background of the technology The through-hole plating method is widely used to connect the front and back conductors of double-sided printed boards or to connect the interlayer conductors of multilayer printed boards. In this through-hole plating method, holes are pre-drilled in an insulating substrate on which conductors are laminated, and a plating layer is chemically or electrically formed on the inner wall of the through-hole to electrically connect the conductors. However, since 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, defects such as pinholes and cuts often occur in the plating layer where through holes are formed. If the defects in the plating layer are large, this leads to poor electrical continuity between the conductors, which poses a major problem in terms of the reliability of the printed board. Therefore, it is desired that defects in such through holes can be easily and reliably inspected.

(3) Problems with conventional technology Conventionally, through-hole inspection methods for printed circuit boards were
The through-hole portion of the printed board on the side illuminated by the inspection light source is masked, and the light that is diffused by entering the board material of the printed board from the non-masked portion is used to determine whether or not the light is leaking into the through-hole. Defects such as pinholes in through holes can be detected by using a detector.

However, with this conventional method, it is not possible to know the presence or absence of a through hole and its position. Therefore, when the board material part of the printed board is indexed to the inspection position, the light that has passed through the inside of the board material is detected by the photodetector, and as a result, it is judged as if there is a through-hole defect. In addition to that,
If the index position of the through hole to the inspection position is shifted and the land portion faces the photodetector, even if the through hole has a defect, it will be determined that there is no defect.

(4) Purpose of the Invention The present invention solves the above-mentioned conventional problems, and makes it possible to detect the presence or absence of through-holes, their position, and the presence or absence of defects, and also improves the reliability and efficiency of through-hole inspection. The object of the present invention is to provide a method and device for inspecting through holes in printed circuit boards.

(5) Structure of the Invention In order to achieve the above object, the printed board through-hole inspection method of the present invention masks one end opening of the through-hole formed in the printed board with a filter, and illuminating the printed board with an illumination device that emits both a first specific wavelength light that passes through the filter and a second specific wavelength light that does not pass through the filter; When the light detection means receives the first specific wavelength light that has passed through the filter and through the through hole, it outputs a first output signal via a comparator, and When the light detection means receives the second specific wavelength light that has propagated into the through hole through the defect in the through hole, it outputs a second output signal via a comparator, and the first and second outputs The defect signal is generated from the signal output means when the logical product of the signals is established.

A through-hole inspection device for a printed board according to the present invention is a through-hole inspection device for a printed board in which a light-transmitting substance is used as a substrate material and a metal through hole is formed on the entire inner wall of a through hole provided in the substrate material, and the device includes the above-mentioned steps. a first filter 5 disposed on one side of the printed board so as to mask one end opening of a through hole formed in the printed board, which transmits a first specific wavelength light and does not transmit a second specific wavelength light; , an illumination device 6 that emits both the first specific wavelength light and the second specific wavelength light from the mask surface side.
a condensing lens 7 disposed on the other side of the printed board and condensing the light passing through the through hole; a half mirror 8 installed on the optical axis of the condensing lens 7; A second filter 9 that transmits only light of a specific wavelength; a first photodetector 10 that detects the transmitted light of the second filter 9 and detects the presence or absence and position of a through hole; and the half mirror 8. a third filter 11 installed on the reflected optical axis and transmitting only the second specific wavelength light; and a second filter 11 that detects the transmitted light of the third filter 11 and detects defects in the through hole. Photodetector 1
2, a first comparator 13 connected to the output of the first photodetector 10, a second comparator 14 connected to the output of the second photodetector 12, and the first comparator 13 and an AND circuit 15 connected to the output of the second comparator 14.

(6) Examples of the invention Examples of the invention will be described below with reference to the drawings.

FIG. 1 shows an example of a through-hole detection device for a printed board according to the present invention. 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 resin. A through hole 4 is formed to electrically connect the front and back conductors (land portions) by forming a plating layer 3 on the inner wall of the through hole 2a drilled in the substrate material. has been done.

On one side of the printed circuit board 1 thus constructed, a filter 5 is provided to mask the opening at one end of the through hole 4.
are arranged in close contact with each other, and this filter 5 allows only light of a specific wavelength, for example, green light, to pass therethrough. In addition, on the side where the filter 5 is arranged,
Light (for example, green) that passes through the filter 5,
An illumination device 6 is arranged that emits both light of a wavelength that does not pass through the filter 5, for example, red light. Note that the green light from the illumination device 6 is configured to illuminate only the portion of the filter 5.
Reference numeral 7 denotes a condensing lens placed on the other side of the printed board 1 facing the through hole 4 to be inspected, which condenses the light passing through the through hole 4. A photodetector 10 that detects the presence and position of the through hole 4 is installed on the optical axis of the half mirror 8 and a filter 9 that transmits only green light. A photodetector 12 is installed above to detect defects in the through hole 4 through a filter 11 that transmits only red light.
Further, comparators 13 and 14 are connected to the output sides of both the photodetectors 10 and 12, respectively, and these comparators 13 and 14 detect whether the respective photodetectors 10 or 12 detect the position or defect of the through hole 4. When detected, that is, when the output signal of the photodetector 10 or 12 exceeds the reference value provided in the comparator 13 or 14, the output is set to "1", and each comparator 13,
The output of 14 is input to an AND circuit 15, and when a logical condition of this AND circuit 15 is satisfied, a defect signal S is sent out.

Note that the above reference value is based on the output signal output from the photodetector 10 or 12 when light reaches the photodetector 10 or 12 through the through hole.
The value is selected to cause the comparator 13 or 14 to output a signal of "1". Therefore, since a signal of "1" is not generated from the comparator 13 or 14 at a position other than the through hole, the AND circuit 1
A signal from 5 to 1 (defective signal) is not generated.

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

When one of the through holes 4 of the printed board 1 is indexed to the inspection position, when green and red lights 16 are irradiated from the illumination device 6 toward the bottom surface of the printed board 1, the green light illuminates the through hole 4. The light passes through the filter 5 that masks the light, passes through the through hole 4, and reaches the condenser lens 7. The transmitted green light is condensed by a condensing lens 7 and projected onto a filter 9 through a half mirror 8, while being reflected by the half mirror and projected onto a filter 11.

Here, since the filter 11 does not pass green light, the photodetector 12 does not operate. On the other hand, since the filter 9 passes green light, the light is detected by the photodetector 10, which not only detects the presence of the through hole 4 at the index position but also detects the position of the through hole 4. The output signal from the photodetector 10 is input to a comparator 13 and compared with its reference value. When the output signal from the photodetector 10 exceeds the reference value, the comparator 13 signals an output signal of "1".

Further, when the lower surface of the printed board 1 is illuminated with red light from the illumination device 6, the light enters the substrate material 2 and is diffused. At this time, if there is no defect such as a pinhole in the through hole 4, the diffused light will not leak into the through hole 4, and therefore the photodetector 1
2 is never operated.

However, if there is a defect 3a in the through hole 4, the light diffused within the substrate material 2 leaks into the through hole 4 through the defect 3a. This light passes through filters 9 and 11 to the lens 7 and half mirror 8, respectively.
It is projected towards. At this time, the filter 9 does not transmit the red light, so the photodetector 10 is not activated by the light, but the filter 11 transmits the red light, so the light is detected by the photodetector 12. . When the signal output from the photodetector 12 exceeds the reference value of the comparator 14, the comparator 14 outputs a signal of "1".

When the outputs of the comparators 13 and 14 both become "1" and the logical condition of the AND circuit 15 is satisfied,
It is determined that there is a defect in the through hole 4 indexed to the inspection position, and a defect signal S is sent out.

In addition, if the through hole 4 is not positioned to the inspection position or is significantly deviated, red light passing through the substrate material 2 may not be detected by the photodetector 1.
Even when the defect signal S is detected by 2, the defect signal S is not sent out.

Therefore, in this embodiment as described above, the through hole is masked with a filter 5 that transmits only light of a specific wavelength, and the light that passes through the filter 5 and the light that does not pass from this mask side are separated. By illuminating both sides and determining a defect when the light from both sides passing through the through hole is detected by the photodetector, the through hole can be reliably inspected for defects, and the inspection efficiency can also be improved. ,
The presence or absence of a through hole and its position can also be detected.

FIG. 2 shows another embodiment of the present invention, in which, as in the case of FIG. 1, one end opening of a through hole 4 formed in a printed board 1 is masked with a filter 5 that transmits only green light. As shown in FIG. 2a, first, the lower surface of the printed circuit board 1 is illuminated with green light 17 from the filter 5 side, and the light passing through the filter 5 is detected by a photodetector 18 provided at a position opposite to the through hole. The presence and position of the through hole 4 is detected. Next, as shown in FIG. 2b, the lower surface of the printed board 1 is illuminated with red light 19 instead of green light, and if there is a defect 3a in the through hole 4 at this time, it will enter the inside of the board material 2. The diffused light leaks into the through hole 4 through the defect 3a, and is detected by the photodetector 18.

In this embodiment, the logical configuration for defect determination is somewhat more complicated than that of the above embodiment, but
In other respects, the same effects as in the above embodiment can be obtained.

(7) Effects of the Invention As explained above, the through-hole inspection device of the present invention can detect the presence or absence of a through-hole and its position, and can also detect the presence or absence of a defect. This has the effect of improving inspection efficiency.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram showing an example of a printed board through-hole inspection device according to the present invention, Fig. 2 a, b
FIG. 2 is a configuration diagram showing another implementation of the present invention. Explanation of symbols 1 is printed board, 2 is board material, 4
5 is a through hole, 5 is a mask filter, 6 is a lighting device, 8 is a half mirror, 9 and 11 are filters, and 10, 12, and 18 are photodetectors.

Claims (1)

[Scope of Claims] 1. Masking one end opening of a through hole formed in a printed board with a filter, and transmitting a first specific wavelength light that is arranged on one side of the printed board and passing through the filter, and the filter. The printed board is illuminated with an illumination device that emits a second specific wavelength light that is not transmitted, and a light detection means arranged on the other side of the printed board is transmitted through the filter and passes through the through hole. When the first specific wavelength light is received, a first output signal is outputted through a comparator, and the second specific wavelength is propagated into the through hole via the substrate material of the printed board and the defect in the through hole. outputting a second output signal via a comparator when the light detection means receives light; and generating a defect signal from the signal output means when a logical product of the first and second output signals is established; A through-hole inspection method for printed circuit boards, which is characterized by: 2. In a through-hole inspection device for a printed board in which a light-transmitting substance is used as a substrate material and a plating through-hole is formed on the entire inner wall of a through-hole provided in the substrate material, a through-hole is formed in the printed board on one side of the printed board. a first filter 5 disposed so as to mask an opening at one end of the through hole, which transmits a first specific wavelength light and does not transmit a second specific wavelength light; an illumination device 6 that emits both light and the second specific wavelength light;
a condensing lens 7 disposed on the other side of the printed board and condensing the light passing through the through hole; a half mirror 8 installed on the optical axis of the condensing lens 7; a second filter 9 that transmits only light of a specific wavelength; a first photodetector 10 that detects the transmitted light of the second filter 9 and detects the presence or absence and position of a through hole; and the half mirror 8. a third filter 11 installed on the reflected optical axis and transmitting only the second specific wavelength light; and a second filter 11 that detects the transmitted light of the third filter 11 and detects defects in the through-hole. Photodetector 1
2, a first comparator 13 connected to the output of the first photodetector 10, a second comparator 14 connected to the output of the second photodetector 12, and the first comparator 13 and an AND circuit 15 connected to the output of the second comparator 14. 3. The printed board through-hole inspection apparatus according to claim 2, wherein the first specific wavelength is green light and the second specific wavelength is red light. 4. The printed board through-hole inspection apparatus according to claim 2, wherein the illumination device 6 emits the first specific wavelength and the second specific wavelength at the same time.