JPS63102398A - Manufacture of ceramic circuit board - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [) Already Required] A method for manufacturing a ceramic circuit board, in which the wiring pattern is insulated in each layer of the board by an insulating coating, while the apparent diameter of the pad is increased. A ceramic circuit board can be manufactured simply and at low cost, and the reliability and yield of the ceramic circuit board can be improved and high-density packaging can be achieved.

[Industrial application field]

The present invention relates to a method of manufacturing a multilayer printed wiring board using ceramic, and more specifically, to a method of manufacturing a ceramic circuit board having a structure in which wiring patterns are located between connection vias.

Multilayer printed wiring boards include resin circuit boards, ceramic circuit boards, and the like, depending on the material of the base material forming each layer.

Ceramic circuit boards generally have higher airtightness than resin circuit boards, and have a VI for interlayer connection of wiring patterns.
It has the advantage of being able to secure several times more A per unit area.

To explain this based on Figures 3 and 4, the 3rd
In the manufacturing process of the resin circuit board 10 illustrated in the figure, a wiring pattern 12 is provided by etching on a resin base material 11 for forming each layer S1, layer S2, and so on. In contrast, the through-holes 13 are stacked one on top of the other, the front and back through-holes 13 are bored by drilling, and the through-holes 13 are coated with metal plating 14 to form the through-hole VIA 15.
In the manufacturing process of the ceramic circuit board 20 illustrated in FIG. After filling the conductive paste and forming the wiring pattern 22 on the surface of the base material 21, a large number of base materials are stacked, laminated, and fired, thereby making the filled portion into a conductive VIA 25. This is based on the difference between

Although ceramic circuit boards have these advantages, they have previously had drawbacks such as a high dielectric constant and a high resistance value of conductive paste such as molybdenum used for wiring patterns.

However, in recent years, these drawbacks have been eliminated as glass ceramics with low dielectric constants that can also be used as resin circuit boards have been developed, and copper pastes with low resistance values can be used by adjusting the firing atmosphere.

Therefore, in recent years, ceramic circuit boards have been increasingly used as substrates for high-density mounting on which high-heat generating components are mounted in large-scale computers and automobile control devices.

The problem here is that ceramic circuit boards have variations in the shrinkage rate of ceramic sheets during firing, as well as differences in the local shrinkage of each ceramic sheet.
This may cause disconnection of the conductive VIA.

This will be explained based on FIG.

In FIG. 5A, the base material 2 of the unfired ceramic sheet
1 includes a rectangular wiring pattern 22 and conductive vias 25 at each corner thereof.

This base material 21 is laminated together with a large number of base materials and fired.

FIG. 5B shows the base material 21 of the layer corresponding to the base material 21 in the ceramic circuit board after firing.

After firing, the wiring pattern 22 and the conduction V
The IA 25 is displaced from its normal planned position.

Therefore, the wiring pattern 22 has a curved line as shown in FIG. 5B.

In this example, the conductive VIs are arranged regularly inside the rectangle.
After firing, A becomes irregularly arranged, and there is a possibility of wire breakage due to layer displacement due to difference in shrinkage rate.

As a result, the reliability and yield of the ceramic circuit board may be significantly adversely affected.

In particular, the possibility of wire breakage occurring due to layer displacement due to differences in shrinkage rates largely depends on the contactable area appearing on the surface of the conductive VIA of each ceramic sheet.
The contactable area greatly affects the conduction VIA and the mounting density of the wiring pattern.

Since various electronic devices are required to be packaged at higher density, there is a need for a method of manufacturing ceramic circuit boards that can be mounted at higher density with high quality and yield at low cost.

[Conventional technology]

The structure of the ceramic circuit board and its manufacturing method are as follows:
Conventionally, for example, as shown in FIG. 6, holes 23 are bored in each ceramic sheet base material 21 for forming each layer of a ceramic circuit board at the positions where conductive VIAs are to be provided, and the holes 23 are filled with holes 23. A conductive paste 26 is filled, and a wiring pattern 22 and a pad 27 are printed on the surface of the base material 21.

A large number of these base materials 21 are stacked and laminated, and fired.

FIG. 7 is an exploded cross-sectional view showing layers S1, S2, and S3, which correspond to each base material 21 in FIG. 6, of the fired ceramic circuit board.

At the time of lamination, as shown in FIG.
A large number of base materials 21 are positioned so that the base materials 3 are lined up in a straight line, but upon firing, each base material 21 shrinks at a different shrinkage rate for each base material 21 or for each part, and the substrate warps. As a result, the conductive VIA 25 and the pad 27 of the conductive VIA 25 that should be connected to it are misaligned as shown in FIG. 7, and the connection between A and B, for example, becomes open.

As a design means to reduce the possibility of such disconnection in this conventional structure, it is conceivable to increase the area or diameter of the pad 27 in comparison with the iT of layer displacement due to the difference in shrinkage rate.

However, it is necessary to maintain a predetermined distance G between the wiring pattern 22 passing between the pads 27 and the pads 27 in order to maintain electrical insulation.

Therefore, if the diameter of the pad 27 is increased as described above, the packaging density of the conductive VIA 25 and the wiring pattern 22 must be reduced.

[Problem that the invention seeks to solve]

In this conventional method, when trying to maintain high-density packaging, connection failures occur due to differences in shrinkage rates of ceramic sheets, etc., and the quality and yield of the ceramic circuit board is poor.

The present invention was created with these points in mind, and an object of the present invention is to provide a method for manufacturing a ceramic circuit board that can improve connection reliability while maintaining high-density packaging.

[Means for solving problems]

In the method for manufacturing a ceramic circuit board of the present invention, in the first step for manufacturing an unfired ceramic sheet, a wiring pattern is provided on the surface of the base material of the unfired ceramic sheet.

In the second step, an insulating coating is applied to the surface of the base material provided with the wiring pattern, except for the part where the pad is to be provided.

Therefore, the wiring pattern is covered with an insulating coating.

In the third step, a pad including a large diameter portion is formed on a portion of the surface of the base material that is not coated with an insulating coating and the surrounding insulating coating.

Note that in the manufacturing method of the present invention, the entire pad to be formed on the surface of the ceramic sheet may be formed in this third step. Further, in the third step, only the large diameter portion of the pad or only a part of the pad mainly consisting of the large diameter portion may be formed. In this case, the other portion of the pad may be formed in the third step. The wiring pattern is formed at the same time as the wiring pattern at a previous stage, for example, in the first step.

A large number of unfired ceramic sheets produced in this manner are stacked one on top of the other, and are fired to produce a ceramic circuit board.

[Effect]

According to the manufacturing method of the present invention: 1. In the unfired ceramic sheet, a pad including a large diameter portion is formed on the surface of the base material and an insulating coating around the pad, and the pad and the wiring pattern are completely insulated from each other by the coating.

Therefore, when this unfired ceramic sheet is laminated with other similar ceramic sheets and fired to manufacture a ceramic circuit board, misalignment between the layers may occur due to the difference in shrinkage rate due to firing. Even when this occurs, the pad overlaps the conductive portion of the adjacent ceramic sheet, such as V[A, etc., in its large diameter portion, so that the contact conduction between the pad and the conductor VIA, etc. is maintained.

Therefore, the reliability of the connection is improved, and the quality and yield of the ceramic circuit board are improved.

In addition, in the ceramic sheet manufactured as described above, the pad and the wiring pattern are insulated by an insulating coating, so the distance between the pad and the wiring pattern is increased while the large diameter part is formed in the pad. can be held briefly.

Therefore, high-density mounting on a ceramic sheet or ceramic circuit board is possible.

According to the present invention, in order to manufacture a ceramic circuit board having such a configuration, it is sufficient to perform steps such as printing pads and wiring patterns on the ceramic sheet and applying an insulating coating. is easy and does not increase manufacturing costs.

〔Example〕

1 and 2 show an embodiment of the present invention, and FIG. 1 is a sectional view showing each step of the method for producing a ceramic sheet in the method for producing a ceramic circuit board according to the embodiment.

A hole 23 is bored in the base material 1 of the ceramic sheet at the position where the conductive VIA 25 is provided, and a conductive paste 2 is inserted into the hole 23.
6 (Figure 1A).

A wiring pattern 2 is printed on the surface of the base material 1 (first
Figure B).

The surface of the base material 1 is masked so as to leave a hole 28 with a cross-sectional shape that widens toward the surface at the position where the pad 3 of the conductive VIA 25 is to be provided, and a glass-based material is coated so as to cover the wiring pattern 2. A paste is applied and printed to form an insulating coating 4 (FIG. 1C).

The thickness of the insulating coating 4 is set to a size corresponding to a minimum gap that guarantees insulation of the wiring pattern 2.

This hole 28 is filled with conductive paste 26 (first
Figure D).

A ceramic circuit board is manufactured by stacking a large number of ceramic sheets manufactured in this way and firing them.

FIG. 2 is an exploded cross-sectional view of a part of the ceramic circuit board manufactured in this manner, showing layers S1 and S2.

In each layer S1, S2, the pad 3 has a generally tapered shape consisting of a large diameter portion 3A and a small diameter portion 3B.

Therefore, since the portion of the pad 3 close to the conductive VIA 25 is a small diameter portion 3B, together with the insulation effect of the insulating coating 4, it is possible to provide an insulation gap necessary for insulation from the wiring pattern 2, and the pad 3 Since the vicinity of the surface is a large diameter portion 3A, the apparent upper diameter DO for connection of the pad 3 is large.

Moreover, a predetermined insulation gap is maintained between the wiring pattern 2 and the large diameter portion 3A by the insulation coating 4.

Therefore, even if layer SL and layer S2 are relatively displaced by a distance T larger than the radius D/2 of small diameter portion 3B due to layer displacement due to firing, the conduction VIA 25 of layer S1 and the size of the pad 3 of layer S2 The diameter portion 3A is connected.

Therefore, reliability can be improved by ensuring electrical and mechanical connections.

The embodiment shown in FIG. 1 may be modified so that the small diameter portion 3B of the pad 3 is printed at the same time as the wiring pattern 2, and only the large diameter portion 3A of the pad 3 is printed after the insulation coating 4 is applied. .

〔Effect of the invention〕

As described above, according to the present invention, the apparent area of the pad on the m-conducting VIA can be increased with a simple configuration without reducing the packaging density, thereby increasing the reliability of the connection of the conductive VIA. This makes it possible to improve the quality and yield of ceramic circuit boards, which is extremely useful in practice.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view showing each step of an embodiment of the present invention, Fig. 2 is an exploded cross-sectional view showing each layer of a ceramic circuit board manufactured according to an embodiment of the present invention, and Fig. 3 is a cross-sectional view of a resin circuit board. 4 is a sectional view of a ceramic circuit board, FIG. 5 is an explanatory diagram showing the shrinkage state of a ceramic sheet due to firing, FIG. 6 is a sectional view of a ceramic sheet before firing by a conventional method, and FIG. 7 is a sectional view of a ceramic circuit board. is a cross-sectional view of each layer after firing by a conventional method. 1 and 2, 1 is a ceramic sheet base material, 2 is a wiring pattern, 3 is a pad, 3A is a large diameter part of the pad, 3B is a small diameter part of the pad, 4 is an insulating coating, 25 is a conductive VIA It is.

Claims (1)

[Claims] In a method for manufacturing a ceramic circuit board by laminating and laminating a large number of unfired ceramic sheets and firing the same, a wiring pattern (
2), applying an insulating coating (4) to the surface of the base material (1) other than the part where the pad (3) is to be provided, and using the insulating coating (4) to form the wiring pattern ( 2), and a pad (3 ) A method for manufacturing a ceramic circuit board, characterized in that the unfired ceramic sheet is manufactured by a manufacturing method comprising a step of forming a ceramic circuit board.