JPH0613755A - Ceramic multilayer wiring board and manufacture thereof - Google Patents

Abstract

PURPOSE:To enable a thin film wiring layer to be well formed so as to enhance a ceramic multilayer wiring board in reliability by a method wherein conductor pattern exposed on both sides of a ceramic multilayer wiring board is formed flush with the surface of ceramic. CONSTITUTION:A flat thin film wiring layer 1 is formed on one side of a ceramic multilayer wiring board where a conductor pattern is exposed, and a sealing cap can be joined firmly. Input/output pins 7, solder bumps, and the like can be bonded onto the other side of ceramic wiring board firmly. As the through-hole conductor metal layer 2 of an outer ceramic green sheet 81 is larger than that of inner ceramic green sheets 83 and 84 in area, the misalignment of the through-hole conductor metal layer 2 for electrical connection of the outer ceramic green sheet 81 to the inner ceramic green sheets 83 and 84 due to burning shrinkage is absorbed to surely connect the outer sheet 81 to the inner sheets 83 and 84, and furthermore the through-hole conductor metal layer 2 of the green sheet is large in area, so that the metal layer 2 is firmly fixed to a ceramic 4, and input/output pins 7, solder bumps, and a sealing cap can be enhanced in bonding strength.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic wiring board, and more particularly to a flat ceramic wiring board having enhanced connection strength such as I / O pins and sealing caps on the front and back surfaces of the board and a method for manufacturing the same.

[0002]

2. Description of the Related Art Ceramic wiring boards are used in electronic calculators, communication devices, home appliances, etc. as substrates for mounting semiconductor chips and small electronic parts because they can be miniaturized and have high reliability. Wet-type ceramic wiring boards that use switches are widely used because they are advantageous for high-density wiring. In this wet type ceramic wiring board, a through hole is formed in a ceramic raw sheet (hereinafter referred to as a green sheet) in which ceramic raw material powder is bonded with an organic resin, and then a wiring pattern of a conductor paste is formed on each sheet. The conductive paste is also filled in the through holes for forming the patterns and connecting the wiring patterns, a predetermined number of the conductive pastes are stacked, pressure-bonded, and then baked.

Nikkei Electronics, 1985
, June 17, pp. 243 to 266 "Water cooling the multi-chip package", further forming thin film wiring on the surface of the fired ceramic wiring board,
I / O pins connect the brazing material on the back side. Also,
When the input / output terminals are minute and the arrangement density is high, solder bumps are formed to connect the input / output pins, and after mounting an LSI, a chip carrier, etc., a cap or the like is sealed with solder to hermetically protect them.

In order to form the above-mentioned thin film wiring, the substrate surface is required to have flatness. On the other hand, since the ceramic wiring substrate after firing has a warp, an unevenness, and a protrusion of the wiring pattern on the substrate surface, it is necessary to polish the substrate surface flat. However, in order to polish the surface of the substrate flat, it was necessary to first polish the back surface of the substrate, which is the reference surface, to be flat. Further, Japanese Patent Application Laid-Open No. 1-140699 discloses that a wiring conductor on the surface of a ceramic substrate is heated and pressed to be embedded in the surface layer by the thickness thereof.

[0005]

In the above-mentioned prior art, since the main object is to make the front and back surfaces of the ceramic wiring board flat, the connection strength of the input / output pins and solder bumps on the back surface of the ceramic wiring board, the board surface. However, there is a problem that the sealing strength and the like are insufficient and no consideration is given.
That is, since the front and back surfaces of the ceramic wiring board are polished, the input / output pattern connected to the back surface of the board, the sealing pattern on the board surface, etc. are formed of thin films. Therefore, the pin connection strength, the bump shear strength, the sealing strength, etc. are weakened to about 1/2 to 1/3 as compared with the case where these are directly provided on the thick film pattern on the front and back surfaces of the ceramic wiring board, which is sufficient. The reliability was not obtained. An object of the present invention is to provide a ceramic wiring board and a method for manufacturing the same that solve the above problems.

[0006]

In order to solve the above-mentioned problems, the conductor pattern surfaces exposed on the front and back surfaces of the ceramic multilayer wiring board are made flush with the ceramic surface.
A thin film wiring layer is formed thereon, and a metal plating film is provided on the conductor pattern surface exposed on the front and back surfaces to connect the input / output pins, solder bumps, sealing caps and the like. In addition, the above ceramic multilayer wiring board is laminated with a ceramic green sheet having a through hole filled with a conductive metal,
Further, on at least one surface of the surface, a ceramic green sheet for surface layer in which a conductive metal is filled in a through hole having an area larger than the through hole is laminated and fired, and then the surface of the ceramic green sheet for surface layer. Is ground flat and manufactured.

Therefore, a ceramic green sheet is laminated on the ceramic green sheet for surface layer before firing and fired, and then the ceramic green sheet after firing is fired.
The surface of the package body is flatly polished to expose the through-hole conductor metal surface of the surface layer ceramic green sheet, and the input / output pins, solder bumps, and sealing caps are exposed on the through-hole conductor metal surface. , The thin film wiring layer, etc. are connected.

[0008]

The thin film wiring layer is formed flat on one surface of the ceramic multi-layer wiring board with the conductor pattern surface exposed, and the sealing cap is connected with good adhesion. Input / output pins, solder bumps, etc. are connected to the other surface with good adhesion.
Since the area of the through-hole conductor metal portion of the surface layer ceramic green sheet is larger than the through-hole conductor metal portion area of the inner layer portion ceramic green sheet, the surface layer portion and the inner layer portion ceramic green portion due to shrinkage or the like. Through-hole of the sheet absorbs the displacement of the conductor metal to ensure the connection between the surface layer and the inner layer, and because the area is large, it is firmly fixed to the ceramic part and the input / output pins, solder bumps, and sealing Increase the connection strength of the cap, etc.

Further, the surface green ceramic green sheet
Since the thickness of the conductive layer after firing is set to the above polishing amount or more, the through hole conductor metal portion of the surface layer portion is not scraped off by polishing. The green sheet provided on the surface layer portion before firing surely and easily fills the conductor paste when the area of the through-hole conductor metal portion is particularly large.

[0010]

[Embodiment 1] FIG. 1 is a partial cross-sectional view of a ceramic wiring board of a mullite material completed according to the present invention. The ceramic wiring board before firing shown in FIG. 2 is prepared as a base. .

First, a method of manufacturing each green sheet in FIG. 2 will be described. The slurry for the green sheet is 7
6 g of ceramic powder consisting of 2 wt% of mullite fine powder, 28 wt% of alumina, silica and magnesia fine powder of sintering aid, polyvinyl butyral organic binder and butylphthalyl butyl glycolate plasticizer 2 g was added, and a solvent having an azeotrope composition consisting of trichloroethylene, tetrachloroethylene, and butyl alcohol was added thereto, and the mixture was thoroughly mixed with a ball mill to uniformly disperse the ceramic powder.
Next, the slurry was agitated and deaerated under reduced pressure to remove air bubbles, and the thickness was adjusted to 0.24 mm using a doctor blade type casting device, followed by cutting into a predetermined size to obtain a green sheet. To make.

FIG. 2 is a partial cross-sectional view of a substrate on which the green sheets are laminated and before firing. The upper and lower through holes for the wiring between the upper and lower green sheets 83, 84, etc. of the inner layer portion are punched using a punching die in which a cemented carbide pin is arranged. Similarly, the through holes of the thick film pattern of the input / output pins of the green sheet, which are exposed on the back surface of the substrate after the lamination, are also punched using a mold. Then, the through holes such as the green sheets 83 and 84 in the inner layer portion and the wiring pattern portion are filled with a tungsten conductor paste.

The tungsten conductor paste is manufactured as follows. Green sheet 83, 8 on the inner layer
The conductor pattern (tungsten paste A) for the wiring pattern in 4 is 80 g of tungsten fine powder, 2 g of glass powder as a sintering aid, 3 g of ethyl cellulose, and diethylene glycol as an organic solvent. 15 g of the above ingredients are mixed and kneaded with a ladle mixer and three rolls, and then n-butyl carbitol acetate is added to adjust the viscosity.

Similarly, the conductive paste (tungsten paste B) for the input / output pattern of the green sheet, which is exposed on the back surface of the substrate after the through holes and the stacked layers, is made of tungsten fine powder having a different particle size distribution. Of 80 g, a glass powder of 4 g as a sintering aid, and the others are manufactured by the same method as the tungsten paste A. Then, the tungsten pastes A and B are used to screen the through holes by a screen printing method.
Then, a wiring pattern is formed on the surface.

Here, after the lamination, the grease exposed on the back surface of the substrate is formed.
Tungsten paste B is filled in the through holes for the input / output pins of the sheet as follows. That is, after the green sheet having no through holes is temporarily adhered to the green sheet, the concave portion formed by the through holes is filled with the tungsten paste B by the screen printing method. Then, as shown in FIG. 2, the green sheets are stacked so that the wiring patterns are electrically connected to each other, and the temperature is 130 ° C. and the pressure is 100 kg / c.
The green sheet is bonded and integrated with each other by m ² .

When the laminated green sheet body of FIG. 2 is fired, the deformation shown in FIG. 3 occurs. Through-hole conductor
If the firing shrinkage of the strike is the same as that of the green sheet, the thickness of the thick film pattern after firing is the green
It will be the same as one sheet. If the firing shrinkage of the conductor paste is smaller than the green sheet, the through-hole portion projects from the ceramic surface of the substrate, and if the firing shrinkage difference is too large, cracks occur.

If the firing shrinkage of the conductor paste is larger than the green sheet, the through-hole portion is recessed from the surface of the ceramic substrate, and if the firing shrinkage difference is too large, cracks or gaps occur. . If the coefficient of thermal expansion of the thick film pattern portion is not equal to that of the ceramic portion, cracks may occur or the strength of the thick film pattern portion may be reduced due to internal stress due to the difference in coefficient of thermal expansion. In the present invention, as described above, the vehicle composition and ratio of the conductor paste, the particle size of the conductor metal particles, the composition of the glass component and the ceramic powder and the addition amount are adjusted to adjust the thick film pattern portion and the green grease. -The firing shrinkage rate and the thermal expansion rate of the gut are made equal.

The firing is performed at a predetermined temperature in a mixed gas atmosphere of nitrogen, hydrogen and water vapor using an electric furnace having the laminated green sheet body on a base plate and molybdenum as a heating element. . The size after firing is 200 mm square,
The thickness of one layer was 0.16 mm. In addition, the amount of warpage and unevenness of the substrate after firing was 60 μm. Then, the flatness of the front and back surfaces of the substrate after the above baking is 1 μm.
m, and the surface roughness is 0.2 μm, the surface is polished to the level of the chain line C shown in FIG. The polishing amount is 0.1 mm on the front side,
The back side is 0.25 mm. Next, N on the back side of the substrate
I / Au plating is performed, and tungsten and Ni are diffused by heat treatment in a reducing atmosphere. Then, as shown in FIG.
The thin film wiring layer 1 is formed on the front surface of the substrate, and the input / output pins 7 are connected to the back surface of the substrate with a brazing material.

COMPARATIVE EXAMPLE 1 The conventional ceramic laminated substrate shown in FIG. 4 is manufactured by the same method as in the first embodiment (FIG. 1) of the present invention, but the thick film pattern conductor metal 3 and its green are used. -The difference is that the sheet 82 is omitted. Since the warp, unevenness, thickness per layer, etc. of the substrate were the same, the front and back sides of the substrate were each 0.1 mm.
The same flatness and surface roughness were obtained by polishing, the thin film wiring layer 1 was formed on the front surface, and the input / output pin connection pattern was formed on the back surface to connect the input / output pins with a brazing material.

Table 1 shows the above Example 1 by the tensile strength tester.
And the connection strength measurement result of the input / output pin 7 of Comparative Example 1,
It can be seen that the present invention can increase the tensile strength about three times.

[Table 1] Since the thick film pattern after polishing has no stress concentration at the interface between the end portion and the ceramic portion, the thickness of the thick film pattern is 2 to 3 compared to the case of the thick film pattern having a raised shape on the ceramic surface.
A relatively high adhesive strength can be obtained.

[Embodiment 2] FIG. 5 is a partial sectional view of an embodiment of the present invention in which a thick film pattern conductor metal 31 on the back surface of a ceramic wiring board is electrically connected to a circuit board 12 via solder bumps. The second embodiment is higher than the first embodiment in that the density of the thick film pattern conductive metal 31 is increased for connecting the solder bumps 11, and the thick film pattern for electrical connection of the thin film layer 1 is formed on the substrate surface. The difference is that the conductive metal film 321 and the thick film pattern conductive metal film 10 for sealing are provided.

Since the area of the thick film pattern conductive metal 31 may be relatively small, the through hole conductive metal (tungsten paste B) 2 is not temporarily bonded to the dummy green sheet. Can be filled by a screen printing method. The thick film pattern conductive metal 10 (tungsten paste) for sealing is filled in the same manner as in the first embodiment. The front and back surfaces of this ceramic wiring substrate are polished and plated, and after heat treatment, a thin film wiring layer is formed on the substrate surface, the substrate surface is capped, and solder bumps for connection are formed on the back surface.

[Comparative Example 2] Table 2 shows the measurement results of the tensile strength of the sealing portion and the shear strength of the solder bump in Example 2 and Comparative Example 2 by using the tensile strength tester and the shear strength tester. It is understood that the invention can increase the tensile strength and the shear strength by about three times.

[Table 2] [Embodiment 3] In this embodiment, the material of the ceramic wiring board is changed from mullite type (Example 1) to alumina type.

As the ceramic powder, 90% by weight of fine alumina powder and 10% by weight of mixed powder of talc and clay having a cordierite composition as a sintering aid were used.
As the tungsten paste, fine tungsten powder having a fineness distribution different from that in Example 1 was used, and glass powder having different composition and additives was used. Others were the same as in Example 1 except that a substrate was prepared, polished, plated and heat-treated, and a thin film was formed on the front surface, and then input / output pins were connected to the back surface with a brazing material.

[Comparative Example 3] Similar to Example 3 and Comparative Example 1, a brazing filler metal was used for the I / O pins having the thin film wiring layer on the polished substrate surface and the I / O pin connecting pattern on the back surface of the substrate. I was connected with. As a result of measuring the connection strength of the input / output pins of the thus-prepared substrate with a tensile tester, the connection strength of Example 3 was about three times that of Comparative Example 3. The same results were obtained for the shear strength of the solder bump and the tensile strength of the sealing portion.

Example 4 A glass wiring board was prepared in which the ceramic material of the ceramic wiring board was alumina filler / borosilicate glass, and the conductor material was copper.
After polishing and forming a thin film, I / O pin connection and solder bump formation and cap sealing are performed on the thick film pattern and thin film pattern, respectively, and the I / O pin tensile strength and solder bump shear strength are The cap sealing strength was examined. As a result, similar to the above, the tensile strength and the shear strength on the thick film pattern are about 2.5 to about 2.5 on the thin film pattern.
It was three times larger.

As described in the above embodiments, if the thickness of the thick film pattern on the front and back surfaces of the substrate in the ceramic wiring substrate after firing is set to be equal to or greater than the polishing amount of the back surface, the substrate after the polishing is finished. Since the thick film patterns on the front and back surfaces remain as they are, it is possible to directly connect the input / output pins to them and to form solder bumps to enhance the connection strength of each. Further, similarly, the cap can be attached with sufficient sealing strength. Further, the same effect can be obtained by applying the present invention to a ceramic wiring board by a green sheet method using another ceramic material or conductor material.

[0028]

According to the present invention, since a flat conductor pattern surface can be formed on the surface of a ceramic multilayer wiring board, a thin film wiring layer can be satisfactorily provided on it, and further, input / output pins and solder bumps can be formed. The reliability of the ceramic multilayer wiring board can be improved by connecting the sealing cap and the like with good adhesion. Since the area of the through-hole conductor metal portion of the surface layer ceramic green sheet is larger than the through-hole conductor metal portion area of the inner layer portion ceramic green sheet, the surface layer portion and the inner layer portion ceramic green portion due to shrinkage or the like. Through-hole of the sheet absorbs the displacement of the conductor metal to ensure the connection between the surface layer and the inner layer, and because the area is large, it is firmly fixed to the ceramic part and the input / output pins, solder bumps, and sealing The connection strength of the cap or the like can be increased.

[Brief description of drawings]

1 is a comparison table of input / output pin connection strength between the ceramic wiring board of FIG. 1 and the conventional board of FIG.

Table 2 is a comparison table of the sealing portion tensile strength and the solder bump shear connection strength of the ceramic wiring board of FIG. 5 and the conventional board.

FIG. 1 is a partial cross-sectional view of a ceramic wiring board according to the present invention in which a thin film wiring layer is formed on the front surface and input / output pins are connected on a thick film pattern on the back surface.

FIG. 2 is a partial cross-sectional view of the ceramic wiring board before firing used in FIG.

FIG. 3 is a partial cross-sectional view of the ceramic wiring board after firing used in FIG.

FIG. 4 is a partial cross-sectional view of a conventional ceramic wiring substrate in which a thin film wiring layer is formed on the front surface and input / output pins are connected on a thick film pattern on the back surface.

FIG. 5 is a partial cross-sectional view of a ceramic wiring substrate having a thin film wiring layer and a thick film pattern for sealing formed on the front surface and solder bumps formed on the thick film pattern on the back surface according to the present invention.

[Explanation of symbols]

1 ... Thin film wiring layer, 2 ... Through-hole conductor metal, 3 ... Thick film pattern
Conductor metal, 4 ... Ceramic part, 5 ... Plating, 6 ... Brazing material, 7 ... Input / output pin, 81 ... Green sheet, 9 ... Thin film pattern, 10 ... Thick film pattern conductor for sealing Metal, 11 ...
Solder bumps, 12 ... Circuit board, C ... Polished surface.

Front page continuation (72) Inventor Seiichi Mitsuda 292 Yoshida-cho, Totsuka-ku, Yokohama, Kanagawa, Ltd.Institute of Industrial Science and Technology, Hitachi, Ltd. (72) Etsuko Takane 292 Yoshida-cho, Totsuka-ku, Yokohama, Kanagawa Hitachi, Ltd., Production Engineering Laboratory

Claims (6)

[Claims] 1. In a ceramic multilayer wiring board, a conductor pattern exposed on the front and back surfaces of the ceramic multilayer wiring board.
A ceramic multilayer wiring board, characterized in that the inner surface is flush with the ceramic surface. 2. The ceramic wiring board according to claim 1, wherein a thin film wiring layer is formed on a front surface and / or a back surface of the ceramic multilayer wiring board. 3. The metal plating film according to claim 1, wherein a metal pattern film is provided on a conductor pattern surface exposed on a front surface and a back surface of the ceramic multilayer wiring board, and input / output pins are connected and / or solder is provided on the metal plating film. A ceramic wiring board having bumps formed and / or caps sealed. 4. A method for manufacturing a ceramic multilayer wiring board, wherein a predetermined number of ceramic green sheets filled with a conductive metal are laminated in predetermined through holes, and the through holes are formed on at least one surface of the ceramic green sheet body. Ceramic layer for surface layer in which conductive metal is filled in through-hole with larger area than hole
A method for manufacturing a ceramic multi-layer wiring board, characterized in that the sheets are laminated and fired, and then the surface of the ceramic green sheet for surface layer is polished flat. 5. The ceramic green sheet according to claim 4, wherein a ceramic green sheet is further laminated on the surface green ceramic sheet and fired, and then the fired ceramic green sheet body is obtained. A method for manufacturing a ceramic multilayer wiring board, wherein the surface is polished flat to expose the through-hole conductor metal surface of the surface ceramic green sheet. 6. The input / output pin and / or the solder bump according to claim 4, wherein the through hole conductor metal surface of the surface layer ceramic green sheet is metal-plated.
And / or a sealing cap, and / or a thin film wiring layer and the like are connected to the ceramic multilayer wiring board.