JPH049252B2 - - Google Patents

Description

[Detailed Description of the Invention] [Summary] Through-hole inspection for printed boards that detects defects by diffusing light into the substrate material of the printed board and detecting the diffused light leaking into the through-holes from defective parts of the through-holes. Regarding the equipment, in order to solve the technical problems that exist with single-sided illumination in through-hole defect inspection of printed circuit boards, we have developed a system in which a conductive layer is formed on the entire inner wall of a printed board at a predetermined position on a light-transmissive substrate near the through-holes. In response to the incidence of light on the light-transmitting substrate and the through-hole to be inspected, and the incidence of light on the through-hole to be inspected, a through-hole position signal and the light to the light-transmitting substrate A through-hole inspection device detects defects in through-holes by positioning a detection system for outputting a through-hole defect display signal in response to the incidence of a through-hole and a through-hole to be detected for each defect. , a defect detection illumination light source provided on both sides of the printed board for simultaneously making light incident on the light-transmitting substrate from both sides of the printed board; and a defect detection illumination light source provided from both of the defect detection illumination light sources. A light shielding means for shielding each light beam from entering the through hole of the defect detection target is provided.

[Industrial application field]

The present invention relates to a through-hole inspection device for a printed board that detects defects by diffusing light into the substrate material of the printed board and detecting the diffused light leaking into the through-hole from a defective portion of the through-hole.

Through-hole plating is widely used to connect front and back conductors of double-sided printed boards or to connect 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 forming the through hole. 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.

[Conventional technology]

Conventionally, the through-hole inspection method for printed circuit boards involves illuminating one side of the printed board with a light source.
As a result, the light diffused into the board material passes through the through-hole defective part, and the light transmitted through the through-hole is detected by a photodetector installed on the opposite side of the printed board, thereby inspecting for the presence or absence of defects. was.

[Problem to be solved by the invention]

However, with this conventional method, if the board material is thick and the diameter of the through hole becomes narrower and longer, or if there is a wiring pattern with a wide area inside the board such as a multilayer printed board, the printed board will be damaged. With only single-sided illumination, it is difficult to detect defects near the surface opposite to the light source, and it is therefore necessary to turn over the printed board once inspected and inspect it again.

The present invention solves the above-mentioned conventional problems, and makes the light intensity distribution of the incident diffused light almost uniform in the thickness direction of the printed circuit board material, and eliminates through-hole defects regardless of the presence or absence of an inner layer conductor pattern and the thickness of the board material. An object of the present invention is to provide a through-hole inspection device for a printed board that can reliably detect the presence or absence of a printed board.

[Means to solve the problem]

The present invention provides for the incidence of light into the light-transmissive substrate near the through-hole in which a conductive layer is formed on the entire inner wall surface of the light-transmissive substrate at a predetermined position of the light-transmissive substrate of a printed board, and the transmission of light to the light-transmissive substrate. A system for outputting a through-hole defect display signal in response to an incident light, and a through-hole inspection device that detects defects in through-holes by positioning each through-hole to be detected as a defect. a defect detection illumination light source provided on both sides of the printed board for simultaneously making light incident on the light-transmissive substrate from both sides of the printed board; A light shielding means for shielding light from entering the through hole of the defect detection target is provided.

[Effect]

By positioning a light input device that makes light enter the through-hole to be inspected in a printed board and its photodetection system, and using the light detection system to detect the light that has entered the through-hole to be inspected, the through-hole to be detected can be detected. A hole position detection signal is obtained by a known method used in the device of the present invention, and at the same time as the position detection or at a different time, a defect detection illumination light source provided on both sides of the printed board is sent to the printed board. A through-hole defect display signal is generated from the photo-detection system indicating the presence or absence of a defect in the through-hole based on whether or not the light reaches the photo-detection system that acts as a through-hole defect detection by simultaneously inputting light into the light-transmissive substrate of the through-hole. is output.

Based on this through-hole defect display signal and the position detection signal, a signal indicating whether or not a defect has occurred in the through-hole to be inspected is outputted.

Each operation for outputting this signal is performed for each defect detection target through hole.

Therefore, it is very useful for solving problems such as uncertainty in defect inspection and an increase in the amount of inspection work that occur when through-hole defects are inspected by illuminating one side of a printed board.

〔Example〕

FIG. 1 shows a first embodiment of a printed board through-hole inspection apparatus according to the present invention, in which 1 is a printed board to be inspected, and a substrate material 2 constituting this printed board 1 is made of glass fibers, for example. By forming a plating layer 3 on the inner wall of a through hole 2a drilled in the substrate material 2, the front and back conductors (land parts) 4 and the inner layer conductor pattern 5 are formed. A through hole 6 for electrical connection is provided.

A plurality of defect detection illumination light sources 7 and 8 for partially illuminating both sides of the board material 2 are disposed on both upper and lower sides of the printed board 1 in such a manner as to extend along the periphery of the front and back conductors 4, respectively. Each light source 7
For 8 and 8, a red color that easily passes through the inside of the substrate material 2 is used. Furthermore, in the center area surrounded by the light sources 7 and 8, trapezoidal cylindrical prisms 9 and 10 whose outer circumferential surfaces are mirrors are arranged with their axes aligned, and each prism 9 is connected to the light sources 7 and 8. A light source 12 for detecting the through hole is arranged on the lower side of the lower prism 10, and light 12a from this light source 12 is used to prevent the light 12a from entering the through hole 6. The light passes through the prism 10, the through hole 6, and the upper prism 9 in order. The light source 12 uses light of a different wavelength from that of the light sources 7 and 8, for example, green light.

Further, a color separation filter 13 is arranged at an angle of 45° on the light exit side of the upper prism 9,
This color separation filter 13 transmits red light and reflects green light, and a photodetector 14 for defect detection is arranged on the transmission optical axis of the color separation filter 13. A photodetector 15 for through-hole detection is arranged on the reflected optical axis of the photodetector 15, and the output side of each photodetector 14, 15 receives a signal that will be sent out depending on the presence or absence of incident light. Binarization circuit 1 that binarizes into “1” and “0”
6 and 17 are connected to each other, and this binarization circuit 1
The binary signals 6 and 17 are input to the AND circuit 18, and when the logical condition of the AND circuit 18 is satisfied,
A defect signal S is sent out.

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

When one of the through holes 6 of the printed board 1 is indexed to the inspection position, when red lights 7a and 8a are irradiated from the light sources 7 and 8 toward both sides of the printed board 1, the lights 7a and 8a The light enters the substrate material 2 and is diffused. Here, the light 7a incident from the upper surface of the substrate material 2 is diffused inside the substrate material 2, but
The light intensity distribution in the thickness direction within the substrate material 2 due to this light 7a has the characteristic that it is largest on the upper surface side of the substrate material 2 and decreases linearly toward the lower surface side, as shown by the solid line in FIG. , Similarly, light 8a
The light intensity distribution in the thickness direction within the substrate material 2 is
As shown by the broken line in the figure, it exhibits a characteristic that it is largest on the lower surface side of the substrate material 2 and decreases linearly toward the upper surface side. Therefore, the substrate material 2 is connected to the light sources 7 and 8.
When the illumination is performed from both the upper and lower sides, the light intensity distribution characteristic shown by the dashed-dotted line is obtained by combining the characteristics of the solid line and the broken line, and a sufficient amount of light can be secured for detecting defects in the through hole 6.

Here, if there is a defective part 3a such as a pinhole on the inner wall of the through hole 6, a part of the light diffused within the substrate material 2 leaks into the through hole through the defective part 3a, and this light 19 is transmitted to the upper prism 9 and The signal passes through the color separation filter 13 and is detected by the photodetector 14 and converted into an electrical signal, which is then binarized by the binarization circuit 16 and applied to one input terminal of the AND circuit 18.

On the other hand, when the through hole 6 reaches the inspection position, the green light from the light source 12 is transmitted to the lower prism 10.
After passing through the through hole 6 and further passing through the upper prism 9, the light is reflected by the color separation filter 13 toward the photodetector 15 and detected by the photodetector 15. Thereby, the presence of the through hole 6 at the inspection position is converted into an electrical signal by the photodetector 15, which is then binarized by the binarization circuit 17 and applied to the other input terminal of the AND circuit 18. Two inputs of AND circuit 18 are both “1”
, the through hole 6 indexed to the inspection position
It is determined that there is a defective part 3a in the area, and a defect signal S is sent out.

Therefore, in this embodiment having the above-mentioned configuration, since the printed board 1 is illuminated from both the upper and lower surfaces, even if there is an inner layer conductor pattern, the defective portion 3a is not exposed to any of the inner walls of the through hole. Even if the defective portion 6a is present in the defective portion, it is possible to reliably detect the defective portion 6a, and there is no need to turn over the printed board that has been inspected once and inspect it again as in the conventional method, and it is possible to detect the defect with a single inspection.

FIG. 3 shows a second embodiment of the invention. In this embodiment, a printed board 1 having through holes 6 is placed on an X-Y stage 20 made of a glass plate, and light ( red)
The light from the light source 7 is prevented from entering the through hole 6 between the lens 21 and the printed board 1, while the lens 21 converts the light into parallel light to partially illuminate the through hole 6 from the top surface. A mask 22 is placed. In addition, a defect detection light source 8 installed on the lower surface side of the X-Y stage 20
The light emitted from the light source 7 is converted into a parallel light beam by a lens 23, and this parallel light beam is irradiated by a mirror 24 toward the lower surface of the printed board 1, facing the irradiation light from the light source 7. A mirror 25 is disposed midway in the direction of the light irradiated by the mirror 24 to prevent parallel light from entering the through hole 6 and to reflect the light 19 leaking from the defective portion 3a of the through hole 6. The emitted light passes through a mirror 26 and a lens 27 and is imaged onto a defect detection photodetector 28.

According to this embodiment configured in this way, in addition to obtaining the same effects as the embodiment shown in FIG. X- made of glass plate
The Y stage 20 can be interposed, and the printed board 1 can be easily supported.

Further, FIG. 4 shows a modified example of the printed board illumination means corresponding to FIG. A glass 20a that is oblique to the plane of the (X-Y stage 20) is bonded, and reflective films 29 and 30 are interposed on the bonded surface. In addition to functioning as a reflection system that guides the leaked light 19 to a defect detection photodetector (not shown), the one reflective film 29 is used as a reflection system to guide the printed board illumination light 3.
1 is made to function as a mask to prevent the intrusion into the through hole 6.

In this embodiment, the mirror 2 shown in FIG.
5 and 26 can be omitted at least.

〔Effect of the invention〕

As described in detail above, according to the present invention, since the printed board is illuminated from both sides, the light intensity distribution of the incident diffused light in the thickness direction of the printed board substrate material can be almost equalized, and therefore, the inner layer conductor Regardless of the presence or absence of a pattern and the thickness of the board material, the presence or absence of defects in through-holes can be reliably detected in a single inspection, and the efficiency of through-hole inspection of printed circuit boards can also be improved.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention, and FIG.
The figure is a characteristic diagram of the light intensity distribution in the thickness direction of the printed board substrate material according to the present invention, FIG. 3 is a diagram showing the second embodiment of the present invention, and FIG. It is an explanatory view showing a modification. In Figures 1 to 4, 1 is a printed board;
2 is a substrate material, 3 is a plating layer, 3a is a defective part, 6 is a through hole, 7 and 8 are illumination light sources for defect detection,
14 and 15 are photodetectors.

Claims (1)

[Scope of Claims] 1. Incidence of light into the light transmissive substrate near the through-hole in which a conductive layer is formed on the entire inner wall surface of the light transmissive substrate at a predetermined position on the light transmissive substrate of the printed board; A system for outputting a through-hole defect indication signal in response to incident light, and a through-hole inspection device that detects defects in through-holes by positioning each through-hole to be detected as a defect. , a defect detection illumination light source provided on both sides of the printed board for simultaneously making light incident on the light-transmissive substrate from both sides of the printed board; and a defect detection illumination light source provided from both of the defect detection illumination light sources. A through-hole inspection apparatus for a printed circuit board, comprising a light shielding means for shielding each light beam from entering a through-hole to be detected for a defect.