JPS59125695A - 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 FI1 Technical Field of the Invention The present invention relates to a printed circuit board in which defects are detected by diffusing light into the substrate material of a printed board and detecting the diffused light leaking into the through ball from a through ball defective part. This invention relates to a plate through-hole inspection device.

(2) Background of the technology The through-ball mating method is widely used to connect the front and back conductors of a double-sided printed board or to connect the glabella conductors of a multilayer printed board. The through-ball plating method involves drilling holes in an insulating substrate laminated with conductors in advance, and creating a plating layer chemically or electrically on the inner wall of the holes to electrically connect the conductors. However, because the plating layer is micron-level thick, the inner wall surface of the through hole is extremely uneven, and the diameter is small, defects such as pinballs and cuts may occur in the plating layer that forms through balls. This often occurs, and 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 circuit board. Therefore, it is desired to be able to easily and reliably inspect such through ball defects.

(3) Conventional technology and problems Conventionally, the through-ball inspection method for printed circuit boards involves illuminating one side of the printed board with a light source, which allows the light that is incident on the board side to be diffused into the through-hole through the through-pole defect. The presence or absence of defects was inspected by detecting the transmitted light with a photodetector installed on the opposite side of the printed board.

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

(4) Purpose of the Invention 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 the presence/absence of the inner layer conductor pattern and the thickness of the board material. It is an object of the present invention to provide a through-pole inspection device for printed l-boards that can reliably detect the presence or absence of through-pole defects regardless of the conditions.

(5) Structure of the Invention In order to achieve the above object, the printed board through-hole inspection device of the present invention has defect detection illumination light sources provided on both sides of the printed board facing each other, and the light from both of the illumination light sources. A light shielding means is provided to allow the light to enter the inside of the printed circuit board from both sides at the same time, and to shield direct light directed from the illumination light source to the through pole.

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

FIG. 1 shows a first embodiment of a through-pole inspection apparatus for printed boards according to the present invention, and 1 is a printed board 1 to a board to be inspected, and a substrate material 2 constituting this printed board 1 is, for example, A through hole 2a is made of a light-transmitting material made of glass fiber impregnated with Evogishi resin, and is bored in the substrate material 2.
A through hole 6 is formed to electrically connect the surface 84 body (land portion) 4 and the inner layer conductor pattern 5 by forming a knob layer 3 on the inner wall.

A plurality of defect detection illumination light sources 7 and 8 for partially illuminating both sides of the substrate material 20 are arranged along the periphery of the front and back conductors 4 on both upper and lower sides of the pudding 1F2.1, which is shaped like this. For each of the light sources 7 and 8, a red light that easily transmits through the inside of the substrate material 2 is used. Further, in the central part surrounded by the light sources 7 and 8, trapezoidal cylinder-shaped prisms 9 and 10 whose outer peripheral surfaces are mirrors are arranged with their axes aligned, and each prism 9 is connected to the light sources 7 and 8, respectively. A light source 12 for through hole detection is arranged on the lower surface side of the lower prism 1O, and light 12a from this light source 12 is used to prevent the light from entering the through ball 6. The light passes through the lower prism 10, the through ball 6, and the upper prism 9 in order. The light source 12 uses light of a different wavelength from that of the light source 7.8, for example, green light.

Further, a color separation filter 13 is arranged at an angle of 45 degrees on the light output side of the upper prism 9, and this color separation filter 13 transmits red light and reflects green light. A photodetector 14 for defect detection is arranged on the transmission optical axis of the separation filter 13, and a color separation filter 13
``Niruko is a photodetector 1 for through-hole detection''
At the same time, on the output side of each photodetector 14 and 15, a binarization circuit 16 is arranged to binarize the signal sent out depending on the presence or absence of incident light into rl, , J, and rOJ.
．． 17 are connected respectively, and each binarization circuit 16.17
The binary signal of is input to the AND circuit 18, and the AND circuit 1
When the logical condition No. 8 is satisfied, a defect signal S is sent out.

Next, the 93 works 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, the light sources 7 and 8 emit red light 7a,
When the light 8a is irradiated onto both sides of the printed board 1, the light 7
The beams a and 8a enter the substrate material 2 and are diffused. Here, the light 7a incident from the upper surface of the substrate material 2 is diffused into the inside of the substrate material 2, and the light amount distribution in the thickness direction within the substrate material 2 due to this light 7a is shown by the solid line ■ in FIG. As shown in FIG.
The light quantity distribution in the thickness direction within J2 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, as shown by the broken line H in FIG. Therefore, when the board 2 is illuminated from both the upper and lower sides by the light sources 7 and 8, the characteristics of the solid line I and the dashed line ■ are combined to give the light intensity distribution characteristic shown by the dashed line ■, which is necessary and sufficient for detecting defects in the through ball 6. The amount of light can be secured.

Here, if there is a defective part 3a such as a vinyl pole 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 color. The signal passes through the separation filter 13, is detected by the photodetector 14, and is converted into an electrical signal, which is then converted into a binary signal by the binarization circuit 1G and applied to one input terminal of the ant' circuit 18.

On the other hand, when the through ball 6 is indexed to the inspection position, the green light from the light #i12 passes through the lower prism 10, passes through the through hole G, and then passes through the upper prism 9. , is reflected by the color separation filter 13 toward the photodetector 15 and detected by the photodetector 15. As a result, the presence of the through ball 6 at the index position is detected, and at the same time, the position of the through ball is also detected, and after being converted into an electrical signal by the photodetector 15, it is binarized by the binarization circuit 17. , is applied to the other input terminal of the AND circuit 18. When the two manpowers of the AND circuit 18 both reach 11'', it is determined that there is a defective portion 3a in the through ball 6 indexed to the inspection position, and a defect signal S is sent out.

Therefore, in this embodiment having the above-mentioned configuration, since the illumination is made from both the upper and lower surfaces of the pudding l-Fj,1, even if there is an inner layer conductor pattern, the defective part 3a is not in the through hole. No matter which part of the wall there is, the defective part 3a
It is possible to reliably detect defects, and there is no need to turn over the pudding 1 to board that has been inspected once and shift the inspection again as in the conventional method, and it is possible to detect defects with a single inspection.

FIG. 3 shows a second embodiment of the invention. In this embodiment, a printed board 1 having soufflé holes 6 is placed on an X-Y stage 20 made of a glass plate, and a light source 7 for detecting defects is emitted from a light source 7 placed on the upper part of the printed board 1. The light (red) is converted into parallel light by the lens 21 and partially illuminates the through ball 6 from the top surface, and the lens 21 and the printed board 1
A mask 22 that prevents light from the light source 7 from entering the through hole 6 is placed between them. Further, the light emitted from the defect detection light source 8 installed on the lower surface side of the X-Y stage 20 is converted into a parallel light beam by a lens 23, and this parallel light beam is bent by a mirror 24 toward the lower surface of the pudding 1 to the plate 1, and the light source The mirror 24 is designed to face the irradiation light from the through hole 6 and to prevent parallel light from entering the through hole 6, and to avoid defects in the through hole 6. The mirror 25 is arranged to reflect light 19 leaking from the portion 3a, and the light reflected by the mirror 25 is imaged on a defect detection photodetector 28 through a mirror 26 and a lens 27.

According to this embodiment configured in this way, the same effects as the embodiment shown in FIG. Accordingly, an XY stage 20 made of a glass plate can be interposed, and the pudding 1 can be easily supported.

Further, FIG. 4 shows a modification of the print slope illumination means corresponding to FIG. 3 of the present invention, in which
A glass 20a whose cut surface is oblique to the plane of the glass plate (X-Y stage 20) is bonded to a part of the glass plate that also serves as the stage 20, and reflective films 29 and 30 are interposed on the bonded surface, This both reflections 1ff29. 30 (This guides the light 19 leaking from the defective portion 32 of the through-hole 6 to a defect detection detector (not shown) (functions as a reflection system) and also directs the one reflective film 29 to the printed board illumination light 31
The rope acts as a mask to prevent the through ball G from entering the through ball G.

In this embodiment, mirrors 25, 26, not shown in FIG.
can at least be omitted.

(7) Effects of the Invention As detailed in section 2, according to the present invention, since the printed board is illuminated from both sides, the amount of incident diffused light increases by υ in the thickness direction of the printed board substrate material. The distribution can be made almost uniform, which makes it possible to reliably detect the presence or absence of through-ball defects in a single inspection regardless of the presence or absence of an inner layer conductor pattern and the thickness of the board material, and also improves the efficiency of through-hole inspection of printed circuit boards. There is an effect that can be done.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing a first embodiment of a through-pole inspection device for printed boards according to the present invention, FIG. FIG. 4 is a block diagram of a through hale inspection device showing a second embodiment of the present invention, and FIG. 4 is an explanatory diagram showing a modification of the print slope illumination means corresponding to FIG. 3. Explanation of symbols 1 is a printed board, 2 is a board (, (, 3 is a plating layer, 3a is a
is a defect iJi, 6 is a through ball, 7.8 is an illumination light source for defect detection, and 14.15 is a photodetector. Patent applicant Supervised by Fujitsu Limited - Koikyo 1, Figure 1, Figure 2

Claims (1)

[Claims] In a through-hole inspection device that detects defects by diffusing light incident on the substrate material of a printed board and detecting the diffused light leaking from the defective part of the through-hole, an illumination light source for defect detection is provided opposite both sides of the printed board. are provided respectively, and the light from this side illumination light source is simultaneously incident into the inside of the substrate material of the pudding board from both sides, and a light shielding means is provided for blocking direct light directed toward the through ball from the illumination light source. Through-ball inspection equipment for printed boards.