JPH1154945A - Multilayered printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayered printed wiring board in which thickness of the prepreg layers that are laminated between outer and inner wiring layers can be inspected simply by a visual means. SOLUTION: The wiring board is provided with a double sided substrate 11 on both sides of which wiring layers L2 and L3 having a specified pattern for each are formed, respectively. At least one of the two wiring layers, L2, is specified as an inner wiring layer, above which an outer wiring layer L1 is formed, laminating prepreg layers 12 and 13 between the layer L1 and the layer L2. A pattern D1 for prepreg layer detection is formed at a specified position of the surface of the inner wiring plane, and a window W1 is formed in the outer wiring layer so that pattern D1 can be observed visually through prepreg layers 12 and 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer printed wiring board, and more particularly, to a method for visually inspecting the thickness of a prepreg layer laminated between an outer wiring pattern and an inner wiring pattern. The present invention relates to a multilayer printed wiring board.

[0002]

2. Description of the Related Art In general, a multilayer printed wiring board is formed by stacking another wiring pattern via a prepreg layer on a wiring pattern of a double-sided board as a core material. The interlayer insulation between them must be higher than other interlayer insulation. As one example, FIG. 8A shows a four-layer printed wiring board having such an irregular layer configuration.

That is, this four-layer printed wiring board includes a double-sided board 1 as a core material having inner layer wiring patterns L2 and L3 on both sides, and one of the inner layer wiring patterns L2
An outer wiring pattern L1 is formed on the prepreg layer 2 with the prepreg layer 2 interposed therebetween.

An outer wiring pattern L4 is also formed on the other inner wiring pattern L3 of the double-sided substrate 1 via the prepreg layer 3. In this case, the outer wiring pattern L3 is located between the inner wiring pattern L3 and the outer wiring pattern L4. The prepreg layer 3 is made thicker than the prepreg layer 2 in order to increase the interlayer insulation. That is, if the prepreg layer 2 is formed of one prepreg, the prepreg layer 3 includes two prepregs 3a and 3b.

[0005]

The prepreg is made of an electrically insulating resin plate having a thermal adhesive property. Since the thickness of one prepreg is about 0.05 to 0.20 mm, the prepreg after the laminating press is used. It is very difficult to visually confirm the number of the layers.

For this reason, the thickness of the printed wiring board is measured by a measuring device after the laminating press to determine the quality of the printed wiring board, but this alone is not sufficient. That is, even if it is determined that the prepreg layer 2 is non-defective in the thickness measurement, as shown in FIG. 8A, one prepreg layer 2 and two prepreg layers 3 should be used as shown in FIG. 8B. The prepreg layer 2
If the prepregs 2a and 2b are laminated and the prepreg layer 3 is made one, it is indistinguishable because the plate thickness is the same, and there is a possibility that the prepreg is shipped as a defective product as it is. Improvement was desired in this regard.

The present invention has been made to solve such a problem, and an object of the present invention is to simply visually check the thickness of a prepreg layer laminated between an outer wiring pattern and an inner wiring pattern. An object of the present invention is to provide a multilayer printed wiring board which can be inspected.

[0008]

According to the present invention, there is provided a double-sided substrate having a predetermined wiring pattern formed on both sides thereof, at least one of which is an inner layer wiring pattern, In a multilayer printed wiring board in which an outer wiring pattern is formed on a wiring pattern via a prepreg layer, a prepreg layer detection pattern is formed at a predetermined position on the inner wiring pattern forming surface, and the outer wiring pattern forming surface is formed. Is provided with a window through which the prepreg layer detection pattern can be seen through the prepreg layer.

Most prepregs are milky white and translucent. Therefore, when the prepreg layer detection pattern is seen through the prepreg through the window on the outer layer wiring pattern side, the prepreg layer detection pattern is more blurred when there are two prepregs than when there is one prepreg. Will be visible. The present invention utilizes this fact, and it is possible to confirm the number of laminated prepregs based on whether the prepreg layer detection pattern is clear or unclear.

When an outer layer pattern is formed on each side of the double-sided board via a prepreg, for example, two prepregs are laminated on one inner layer wiring pattern,
In a multilayer printed wiring board in which one prepreg is laminated on the other inner layer wiring pattern, a prepreg layer detection pattern that can be seen through the prepreg from the window portion on each inner layer wiring pattern forming surface as described above. Is preferably provided.

According to this, when the multilayer printed wiring board is viewed from the front side and the back side, if the sharpness of the prepreg layer detection pattern is different, it is determined to be a good product, and the sharpness of the prepreg layer detection pattern is determined. If they are the same, it can be determined that they are defective. That is, it is not necessary to separately prepare a reference detection pattern as a pass / fail determination criterion.

As described above, when the prepreg layer detection patterns are formed on the respective inner layer wiring pattern formation surfaces, it is preferable that the prepreg layer detection patterns be the same pattern. Further, the prepreg layer detection pattern may be any of a figure, a symbol, and a character. However, from the viewpoint of easy visual judgment, it can be said that a bar code pattern composed of a combination of a thick line and a thin line is preferable.

The present invention is not limited to a multilayer printed wiring board having an irregular layer configuration in which prepreg layers having different thicknesses are formed on each surface of a double-sided substrate as a core material. The present invention can also be applied to the inspection of an indispensable multilayer printed wiring board.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Next, for better understanding of the technical concept of the present invention, an embodiment will be described with reference to the drawings.

FIG. 1 is an exploded perspective view of a four-layer printed wiring board 10A having an irregular layer configuration as a first embodiment viewed from the lower surface side, and FIG. . This four-layer printed wiring board 10A includes a double-sided board 11 as a core material.

The double-sided board 11 has a copper foil layer bonded on the front side and the back side via an insulating layer 11a, and inner layer wiring patterns L2 and L3 are formed on each of the copper foil layers. In the present invention, the prepreg layer detection patterns D1 and D2 are formed on each copper foil layer together with the inner layer wiring patterns L2 and L3.

In the first embodiment, each of the prepreg layer detection patterns D1 and D2 is composed of a bar code having the same configuration as shown in FIG.
It may be formed at positions facing each other on the front and back sides of the blank portion or the discard plate portion. In FIG. 2, the barcodes of the prepreg layer detection patterns D1 and D2 are written in the vertical direction for convenience of drawing. However, each bar is actually arranged along a plane perpendicular to the paper surface. I have.

In the first embodiment, two prepregs 12, 13 are laminated on one inner layer wiring pattern L2, and an outer layer wiring pattern L1 is formed thereon. When the outer wiring pattern L1 is formed, a portion of the copper foil corresponding to the prepreg layer detection pattern D1 is removed by etching to form a window W1 for seeing through the prepreg layer detection pattern D1.

One prepreg 14 is laminated on the other inner layer wiring pattern L3, and an outer layer wiring pattern L4 is formed thereon.
A window portion W2 for seeing through the prepreg layer detection pattern D2 is also provided on the surface on which is formed.

Double-sided substrate 11, prepregs 12, 13, 1
4 and the outer layer wiring patterns L1 and L4 are integrated by a lamination press, and in the inspection step after the outer layer wiring patterns L1 and L4 are etched, when the prepreg layer detection pattern D1 is viewed from the window W1, two sheets Bripreg 1
Since the layers 2 and 13 are stacked, the prepreg layer detection pattern D1 is slightly blurred as illustrated in FIG. 4A.

On the other hand, when the prepreg layer detection pattern D2 is viewed from the side of the window W2, there is only one prepreg 14 in between, so that the window W1 is exemplarily shown in FIG. The prepreg layer detection pattern D2 looks clearer than when viewed from the side. Thus, according to the first embodiment, the front and back windows W1, W
By looking at the prepreg layer detection patterns D1 and D2 from FIG. 2, it is possible to inspect whether or not the prepregs 12, 13, and 14 are laminated on the proper number and on the proper side.

Next, a description will be given of a five-layer printed wiring board 10B having an irregular layer structure according to a second embodiment shown in FIG. In the second embodiment, the outer layer wiring pattern L4 of the first embodiment is used.
Instead of this, the double-sided board 21 is laminated on the inner layer wiring pattern L3 via one prepreg 14, and for the other structure, refer to the first embodiment.

The double-sided board 21 is the same as the double-sided board 1 described above.
1 has a copper foil layer bonded on both front and back sides via an insulating layer 21a, and a wiring pattern is formed on each of the copper foil layers. In this case, one of the wiring patterns is an inner layer wiring pattern. L4a, and the other is an outer wiring pattern L5.

A window W2 for seeing through the prepreg layer detection pattern D2 is formed on the double-sided substrate 21. The window portion W2 is formed by removing the copper foil at the portion corresponding to the prepreg layer detection pattern D2 for the front and back copper foil layers by etching, and removing the insulating layer 21a by laser, router, or NC processing. can do.

FIG. 6 shows a third embodiment in which one prepreg 15 is further placed on the double-sided substrate 21 of the second embodiment.
6C shows a six-layer printed wiring board 10C having an irregular layer configuration in which an outer layer wiring pattern L6 is formed through the printed wiring board 10C.

That is, in the third embodiment, the pattern L5 of the double-sided substrate 21 which was the outer layer wiring pattern in the second embodiment is changed to the inner layer wiring pattern L5a. Along with L5a, for example, a prepreg layer detection pattern D3 made of a barcode having the same configuration as the prepreg layer detection patterns D1 and D2 is formed in a blank portion or a discarded plate portion, for example.

A window portion W2 for seeing through the prepreg layer detection pattern D2 is provided over the outer layer wiring pattern L6 and the double-sided substrate 21, and a window for seeing through the prepreg layer detection pattern D3 is provided in the outer layer wiring pattern L6. The portion W3 is formed. By adding the window portion W3, not only the prepregs 12, 13, and 14, but also the number of laminated prepregs 15 can be visually confirmed.

Finally, as a fourth embodiment, a three-layer printed wiring board 10D having an irregular layer structure shown in FIG. 7 will be described. The three-layer printed wiring board 10D has a three-layer structure by removing the prepreg 14 and the outer wiring pattern L4 from the four-layer printed wiring board 10A of the first embodiment. Since the wiring pattern L3 is changed to the outer wiring pattern, the prepreg layer detection pattern D1 is provided only on one inner wiring pattern L2 side.

The fourth embodiment is the most simplified one of the present invention. In this case, the outer layer wiring pattern L1 and the inner layer wiring pattern L1 are determined based on the sharpness of the prepreg layer detection pattern D1 by looking at only one of the windows W1. The number of prepreg layers to be laminated is determined between the wiring patterns L2. At this time, it is preferable to compare the definition of the prepreg layer detection pattern D1 between the substrates or a non-defective substrate.

In each of the above embodiments, two prepregs are used as the irregular layer structure. However, three or more prepregs may be used depending on the transparency of the prepreg. Also,
The present invention is not intended only for a multilayer printed wiring board having an irregular layer structure, but is intended to inspect a case in which prepregs should be laminated one by one between layers, but more prepregs are laminated. Is also applicable.

[0031]

As described above, according to the present invention,
A multilayer printed wiring comprising a double-sided substrate having a predetermined wiring pattern formed on both surfaces, at least one of which is an inner wiring pattern, and an outer wiring pattern formed on the inner wiring pattern via a prepreg layer In the board, while forming a prepreg layer detection pattern at a predetermined location on the inner layer wiring pattern formation surface, by providing a window that allows the prepreg layer detection pattern to be visible through the prepreg layer on the outer layer wiring pattern formation surface, The thickness of the prepreg layer laminated between the outer wiring pattern and the inner wiring pattern can be easily inspected visually.

[Brief description of the drawings]

FIG. 1 is a schematic exploded perspective view of a four-layer printed wiring board having an irregular layer configuration as a first embodiment of the present invention.

FIG. 2 is a schematic enlarged sectional view of a main part of the first embodiment.

FIG. 3 is a plan view showing an example of a prepreg layer detection pattern used in the first embodiment.

FIG. 4 is an explanatory diagram showing the relationship between the thickness of a prepreg layer and the sharpness of a prepreg layer detection pattern appearing through the prepreg layer in the first embodiment.

FIG. 5 is a schematic enlarged cross-sectional view of a principal part of a five-layer printed wiring board having an irregular layer configuration as a second embodiment of the present invention.

FIG. 6 is an enlarged schematic cross-sectional view of a main part of a six-layer printed wiring board having an irregular layer configuration according to a third embodiment of the present invention.

FIG. 7 is a schematic enlarged sectional view of a principal part of a three-layer printed wiring board having an irregular layer configuration as a fourth embodiment of the present invention.

FIG. 8 is a cross-sectional view schematically showing a conventional four-layer printed wiring board having an irregular layer configuration and a four-layer printed wiring board as a defective product thereof.

[Explanation of symbols]

 10A to 10D Multilayer printed wiring board having irregular layer configuration 11 Double-sided board 12 to 15 Prepreg D1, D2 Prepreg layer detection pattern L1 to L6 Wiring pattern W1 to W3 Window

Claims (4)

[Claims] 1. A double-sided substrate having a predetermined wiring pattern formed on both sides thereof, wherein at least one of the wiring patterns is an inner wiring pattern, and an outer wiring pattern is formed on the inner wiring pattern via a prepreg layer. In the multilayer printed wiring board, a prepreg layer detection pattern is formed at a predetermined position on the inner layer wiring pattern formation surface, and the prepreg layer detection pattern is visually observed on the outer layer wiring pattern formation surface through the prepreg layer. A multilayer printed wiring board characterized by being provided with a window portion that can be used. 2. A double-sided board having a predetermined wiring pattern formed on both sides thereof, wherein both wiring patterns are formed as inner layer wiring patterns, and an outer layer wiring pattern is formed on each of the inner layer wiring patterns via a prepreg layer. In the formed multilayer printed wiring board, a prepreg layer detection pattern is formed at a predetermined position on each of the inner layer wiring pattern forming surfaces, and the prepreg is formed on each of the outer layer wiring pattern forming surfaces through the prepreg layer. A multilayer printed wiring board, wherein each of the windows is provided with a layer detection pattern that can be viewed. 3. The multilayer printed wiring board according to claim 2, wherein the prepreg layer detection patterns formed on each of the inner layer wiring pattern forming surfaces are the same pattern. 4. The multilayer printed wiring board according to claim 1, wherein the prepreg layer detection pattern is a barcode pattern.