JPH0697624A - Inspection method of printed wiring board - Google Patents

Abstract

PURPOSE:To inspect through holes in a wide domain by one visual field, without visual inspection from just above the through holes, improve visual recognition capability, shorten inspection time, and enhance the reliability of inspection process such as reduction of oversight. CONSTITUTION:On one main surface side of a printed wiring board 1, a mask 3 which is formed by the same pattern as many through holes 2 and has light transmission parts 3a colored red. On the other main surface side of the printed wiring board is arranged 1, a mask 4 which is formed by the same pattern as many through holes 2 and has light transmission parts 4a colored blue is arranged. From the one main surface side, light is casted by using a surface emitting light source 5, and the part between the printed wiring board 1 and the mask 4 is irradiated with light from auxiliary light sources 6a, 6b. On the other main surface side, color change on the mask 4 is detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for inspecting a printed wiring board, and more particularly to a method for inspecting the appearance of through holes formed in a large number in the printed wiring board.

[0002]

2. Description of the Related Art Conventionally, an operator holds a printed wiring board by handling and the through-hole portion is directed toward a light source for the visual inspection of the through state of through holes and the side wall surface of the through holes formed in the printed wiring board. When the light passed through the through holes, it was visually confirmed that the through holes were in the through state, and the through states of almost all the through holes were visually confirmed. However, a large number of through holes, for example, 5,000 on a printed wiring board of about 30 cm square.
In the case of a high-performance printed wiring board in which about 0 to 10,000 through holes are formed, it takes time to confirm the presence or absence of penetration of the through holes, and unconfirmed parts (unrecognized parts) easily occur, which is reliable. It had the disadvantage of poor sex.

The diameter of a typical through hole is 0.39 m
From about m, the hole diameter of the through hole of the specification that requires high functionality is about 0.15 mm, and it is expected that the number of processes will be greatly increased in the process of confirming the opening of the through hole. Further, since the diameter is small, it is difficult to confirm the penetration state because the light from the light source cannot pass through the through hole unless the light is emitted at a right angle to the main surface of the printed wiring board.

That is, to explain with reference to FIG. 5, the printed wiring board 1 is arranged on the light source 5 in parallel with the surface emitting light source 5, and the printed wiring board 1 is viewed from directly above the through hole 2A on the printed wiring board 1 to the lower side. Although the penetration state of the through hole 2 is to be confirmed, when there is an operator at the point A, the through holes 2B and 2C are viewed from an oblique direction, and the penetration state cannot be confirmed. The inspection is performed by moving the worker to the first position or moving the printed wiring board 1 so that each through hole is directly above the worker's visual point A.

[0005]

However, in the above-mentioned conventional inspection method, the visual inspection of the through state of the through hole of the printed wiring board which is highly functionalized is performed visually, so that the inspection time increases and There was a problem that oversight was likely to occur and the inspection accuracy was poor. Therefore, according to the present invention, it is possible to check the penetration state of a wide range of through holes in a single visual field without visually observing the through holes immediately above, and to improve the visibility, and to shorten the inspection time and reduce the oversight of inspection. An object of the present invention is to provide a method for inspecting a printed wiring board, which enables improvement in process reliability.

[0006]

According to the inspection method of the present invention, a printed wiring board has, on one main surface side thereof, a light transmitting portion formed in the same pattern as a large number of through holes and colored in a predetermined color. A second mask having a first mask and a light-transmitting portion formed in the same pattern as a large number of through holes and colored in a color different from the predetermined color on the other main surface side of the printed wiring board. And irradiating light from the one main surface side to the main surface of the printed wiring board at a substantially right angle through the first mask, and at the same time, applying light between the printed wiring board and the second mask. Irradiation is performed, and the color change on the second mask is detected on the other main surface side.

In another inspection method according to the present invention, a first mask having a light-transmitting portion formed in the same pattern as a large number of through holes is closely arranged on one main surface of the printed wiring board, and the printed wiring board is also provided. A second mask having a large number of through holes and an opaque portion formed in the same pattern is closely arranged on the other main surface of the board, and one main surface side of the first mask is attached to the main surface of the printed wiring board. Light is radiated through the mask at a substantially right angle, and leaked light from the light transmitting portion of the second mask is detected.

[0008]

In the inspection of the through state of the through hole, the light emitted from the light source is transmitted through the light transmitting portion of the first mask, and if the light transmitting portion is colored red, for example, The transmitted light of the mask of 1 changes to red light,
By passing through the through hole and further through the light transmitting portion of the second mask, if the light transmitting portion is colored blue, for example, the light transmitted through the second mask is changed to black light. To do. Here, if the portions other than the light transmitting portion of the second mask are processed to be black, if the through hole is in a penetrating state, black display is performed over the entire surface of the second mask. On the other hand, if there is filler in the through hole, the first
Since the red light transmitted through the light-transmitting portion of the mask is unable to pass through the through hole, the light radiated to the gap between the printed wiring board and the second mask is transmitted through the light-transmitting portion of the second mask and is blue. Illuminate the surface of the second mask as light. It is possible to detect that the through hole in that portion is not in a penetrating state by the color display using the blue light.

In detecting the presence / absence of a pinhole in the through hole, the light transmitted through the light transmitting portion of the first mask and entering the through hole has the second exit at the through hole.
Since it is shielded from light by the non-transmissive part of the mask, it is optically sealed in the through hole. Here, if there is a pinhole, the light sealed in the through hole leaks into the printed wiring board from the pinhole, travels through the base material containing epoxy resin as a main component, and enters the dark field state. The light transmitting portion of the second mask is brightened. This makes it possible to detect the presence of a pinhole in the through hole at that portion.

[0010]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a configuration diagram for explaining an embodiment of a printed wiring board inspection method according to the present invention. In the figure, a large number of through holes 2 are formed in the printed wiring board 1, and at the time of a visual inspection for confirming the through state of these through holes 2, one main surface (lower surface in the drawing) of the printed wiring board 1 side A mask 3 and a mask 4 on the other main surface (upper surface in the figure) side.

A large number of light transmitting portions 3a are formed on the mask 3 in the same pattern as the through holes 2 formed in the printed wiring board 2. The light transmitting portion 3a is colored red, for example. The color of the light transmitting portion 3a is not limited to red, and may be another color such as blue or green. Similarly, the mask 4 has a large number of light transmitting portions 4
a is formed. The light transmitting portion 4a is colored blue, for example. As with the mask 3, the color of the light transmitting portion 4a is not limited.

As shown in FIG. 1, these masks 3 and 4 are arranged in such a manner that the light transmitting portions 3a and 4a are located on the same center line with respect to the through hole 2. Then, the surface emitting light source 5 is arranged, for example, on the lower surface side of the printed wiring board 1, and the surface emitting light source 5 is connected to the printed wiring board 1.
The light should be emitted almost at right angles to the main surface of. As a result, with respect to the light emitted from the surface emitting light source 5, the light transmitting portion 3a, the through hole 2, and the light transmitting portion 4a are located on the same optical path. In addition, the gap between the printed wiring board 1 and the mask 4 is irradiated with light by the auxiliary light sources 6a and 6b. In this example, as a light source for irradiating the through hole 2 of the printed wiring board 1,
Although the surface emitting light source 5 is used, the light emitting source is not limited to the surface emitting light source as long as it is a light source capable of irradiating light into the through hole 2 and can be changed according to technically required specifications.

Next, a method of inspecting the through state of the through hole 2 in the above structure will be specifically described. The light emitted from the surface emitting light source 5 is transmitted through the light transmitting portion 3a of the mask 3, and the light transmitting portion 3a is colored red. Pass 2. Here, when the filling material exists in the through hole 2, it becomes a non-penetrating through hole 2a and cannot pass through. Even though it is not completely filled, the amount of light that passes through is reduced.

The red light passing through the through hole 2 is transmitted through the light transmitting portion 4a of the mask 4, but since the light transmitting portion 4a is colored blue, it is transmitted through the light transmitting portion 4a. By doing so, it changes to blackish light.
Here, since the light transmitted through the light transmitting portion 4a is changed to black by treating the portions other than the light transmitting portion 4a of the mask 4 to be black, if all the through holes 2 are in the penetrating state, the printed wiring is The surface of the mask 4 viewed from the upper surface side of the plate 1 is entirely in a black color display.

On the other hand, when there is a non-penetrating through hole 2a or there is a defect in the through hole 2, the red light transmitted through the light transmitting portion 3a of the mask 3 cannot pass through the through hole portion, The light applied to the gap between the printed wiring board 1 and the mask 4 by the auxiliary light sources 6a and 6b is transmitted through the light transmitting portion 4a of the mask 4. As for the transmitted light, since the light transmitting portion 4a of the mask 4 is colored blue,
It becomes blue light and illuminates the surface of the mask 4.

Therefore, the non-penetrating through hole 2a,
In the printed wiring board 1 including the defective through hole 2, only the through hole portion is displayed in blue, so that the unpenetrated through hole 2a and the defective through hole 2 can be reliably identified. As a result, in the visual inspection, the visibility can be improved, so that the inspection accuracy can be improved and the reliability of the inspection process such as the reduction of the inspection time can be improved.

To explain the present invention schematically, when the through hole 2 is normal, as shown in FIG. 2, the light emitted from the surface emitting light source 5 transmits the red processed light of the mask 3. After being converted into red light by passing through the portion 3a, the light passes through the through hole 2 and is transmitted through the blue-processed light transmitting portion 4a of the mask 4 to be visually recognized as blackish light. On the other hand, if the through hole 2 has a defect, as shown in FIG. 3, the light emitted from the surface emitting light source 5 passes through the red-processed light transmitting portion 3a of the mask 3, but there is a defect. When the light is blocked or dimmed by the through hole 2, the amount of light that discolors by passing through the blue-processed light transmitting portion 4a of the mask 4 is eliminated. Therefore, the light from the auxiliary light sources 6a and 6b passes through the gap between the printed wiring board 1 and the mask 4 and passes through the blue-processed light transmitting portion 4a of the mask 4, and as a result, the defective through hole is passed. The part of the hole 2 is visually recognized as blue light.

FIG. 4 is a block diagram for explaining another embodiment of the method for inspecting a printed wiring board according to the present invention. This inspection method is introduced into the manufacturing process of a printed wiring board. In the present embodiment, in the through hole 2, the pinhole 10 caused by non-plating when the plating layer 7 is formed.
The case where it is applied to the inspection of the presence or absence of a and 10b is shown. In the figure, a mask 8 is closely arranged on one main surface (lower surface of the drawing) of the printed wiring board 1 and a mask 9 is closely arranged on the other main surface (upper surface of the drawing).

In the mask 8, a light transmitting portion 8a having substantially the same diameter as that of the through hole 2 formed in the printed wiring board 1 is arranged and formed in the same pattern as the through hole 2. On the other hand, in the mask 9, an opaque portion 9a having a diameter substantially the same as or slightly larger than that of the through hole 2 is arranged and formed in the same pattern as the through hole 2. As shown in FIG. 4, these masks 8 and 9 are arranged in such a state that the light transmitting portion 8a and the non-transmissive portion 9a are positioned so that they are located on the same center line with respect to the through hole 2. Then, the surface emitting light source 5 is arranged, for example, on the lower surface side of the printed wiring board 1, and the surface emitting light source 5 irradiates the main surface of the printed wiring board 1 with light at a substantially right angle.

Next, a method for inspecting the presence / absence of the pinholes 10a, 10b of the through hole 2 in the above structure will be specifically described. The light emitted from the surface emitting light source 5 is incident on the through hole 2 of the printed wiring board 1 by passing through the light transmitting portion 8 a of the mask 8. Here, since the exit of the through hole 2 (upper surface side of the substrate) is shielded by the opaque portion 9a of the mask 9, the incident light is optically sealed in the through hole 2. At this time, the pinholes 10a, 1
When 0b is present, the sealed light is emitted from this pinhole 1
0a, 10b leaks to the inside of the printed wiring board 1, penetrates through the base material mainly composed of epoxy resin, and passes through the mask 9
The light is transmitted to the outside from the light transmitting portion 9b.

That is, in the appearance inspection of the through hole 2, when the pin holes 10a and 10b are present in the through hole 2, the light from the surface emitting light source 5 is transmitted through the light transmitting portion 8a of the mask 8 to the inside of the through hole 2. Since it is introduced into, the periphery of the printed wiring board 1 is in a dark field state.
The light leaked from the pinholes 10a and 10b brightens the periphery of the through hole 2 in the dark field state on the main surface of the printed wiring board 1 opposite to the surface emitting light source 5. Therefore, when inspecting for the presence of the pinholes 10a and 10b,
Since it is possible to easily check the presence or absence of the pinholes 10a and 10b without checking the through holes 2 one by one, the inspection time required for the appearance inspection can be shortened and the inspection rate (pinhole discovery rate) can be improved. it can.

[0022]

As described in detail above, according to the present invention, the light transmission formed on one main surface side of the printed wiring board in the same pattern as a large number of through holes and colored in a predetermined color. While arranging the first mask having a section,
On the other main surface side of the printed wiring board, a second mask having a light transmitting portion formed in the same pattern as a large number of through holes and colored in a color different from the predetermined color is arranged.
Light is radiated from one main surface side at a substantially right angle to the main surface of the printed wiring board, and light is radiated between the printed wiring board and the second mask, and the second main surface side is irradiated with the light. By detecting the color change on the mask, the through hole part and the non-penetrating part are displayed by color, and a wide range of parts can be inspected in one visual field.
The visibility can be improved, and the reliability of the inspection process can be improved by shortening the inspection time and reducing the oversight of the inspection.

Further, a first mask having a plurality of through-holes and light-transmitting portions formed in the same pattern is closely arranged on one main surface of the printed wiring board, and the other main surface of the printed wiring board is arranged on the other main surface. , A second mask having an opaque part formed in the same pattern as many through holes and a light-transmitting part other than the through-hole is closely arranged, and is substantially perpendicular to the main surface of the printed wiring board from one main surface side. Illuminate the
By detecting the leaked light from the light transmitting portion of the second mask, it is possible to easily inspect for the presence of pinholes without having to check each through hole individually. The time can be shortened and the pinhole detection rate can be improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram according to an embodiment of an inspection method according to the present invention.

FIG. 2 is a schematic diagram when a through hole is normal.

FIG. 3 is a schematic view when a through hole is abnormal.

FIG. 4 is a configuration diagram according to another embodiment of the inspection method according to the present invention.

FIG. 5 is a configuration diagram showing a conventional example.

[Explanation of symbols]

 1 Printed wiring board 2 Through hole 2a Non-through hole 3,4,8,9 Mask 5 Surface emitting light source 6a, 6b Auxiliary light source 10a, 10b Pinhole

Claims (2)

[Claims] 1. An inspection method for inspecting the appearance of a large number of through holes formed in a printed wiring board, which is formed in the same pattern as the large number of through holes on one main surface side of the printed wiring board. A first mask having a light-transmitting portion colored in a predetermined color is arranged, and the plurality of through-holes are formed in the same pattern on the other main surface side of the printed wiring board and have the predetermined color. A second mask having a light-transmitting portion colored in a color different from that of the first mask is provided, and light is emitted from the one main surface side at a substantially right angle to the main surface of the printed wiring board through the first mask. A printed wiring, which is irradiated with light and is irradiated between the printed wiring board and the second mask to detect a color change on the second mask on the other main surface side. Board inspection method. 2. An inspection method for inspecting the appearance of a large number of through holes formed in a printed wiring board, which is formed on one main surface of the printed wiring board in the same pattern as the large number of through holes. A first mask having a light transmitting portion is closely arranged, and a second mask having an opaque portion formed in the same pattern as the plurality of through holes is closely arranged on the other main surface of the printed wiring board. Then, light is radiated from the one main surface side to the main surface of the printed wiring board at a substantially right angle through the first mask, and leak light from the light transmitting portion of the second mask is detected. A method for inspecting a printed wiring board, which is characterized in that