JPH0823169A - Manufacture of multilayer ceramic wiring board - Google Patents

Abstract

PURPOSE:To reduce short circuits or openings of thin film patterns formed on a substrate by making small a void diameter in the outermost layer or in the surface layer of a multilayer ceramic wiring board. CONSTITUTION:Green sheets, whose manufacturing differs for the outermost layer or a surface layer 1 and an internal layer 2, are used. Each green sheet is treated with a through hole 3, and the like. After a prescribed number of laminates are bonded and sintered to make a void 4 in the outermost layer or the surface layer 1 smaller than the void 4 in the inner layer 2. For decreasing the void 4 in the outermost layer or the surface layer 1, there are methods such as dry mixing and adding of powder materials or reduction of the blending rate of flux and a combination of both. Consequently, by making smaller the void diameter in the outermost layer or the surface layer 1 of the multilayer ceramic wiring board, short-circuits and inferior openings of a thin film pattern formed on the multilayer ceramic wiring board can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a ceramic multilayer wiring board having a structure in which the outermost layer or surface layer is denser than the inner layer.

[0002]

2. Description of the Related Art Conventionally, in a method of manufacturing a ceramic multilayer wiring board of this type, a binder and a solvent are added to about 70 ωt% of inorganic powder and about 30 ωt% of a flux component, and the mixture is mixed in a ball mill for a predetermined time, and vacuum deaeration is performed. Go to create a slurry. Next, form through holes in the green sheet,
After filling the through holes with the conductor paste, the wiring pattern is printed by the screen printing method. Then, a predetermined number of the green sheets are laminated, thermocompression-bonded using a hot press, and then sintered with a predetermined profile to produce a ceramic multilayer wiring board.

[0003]

When a thin film layer is formed on a ceramic multilayer wiring substrate prepared by a conventional method, it is necessary to carry out surface polishing in order to secure flatness, and by carrying out polishing, the outermost layer or The voids in the surface layer are exposed on the surface. In this way, in the ceramic multilayer wiring board created by the conventional method, since the void diameter in the green sheet used for the outermost layer or the surface layer is large, if a thin film pattern is formed on this, the insulating film will flow into the void portion, Since the insulating state is deteriorated and the flatness is deteriorated, a portion to which a sputtered film for forming a pattern is not adhered is formed, which may cause a short circuit or an open. Therefore, it is necessary to reduce voids in the outermost layer or the surface layer.

[0004]

In the present invention, a powder material is put into a ball mill and dry mixed for a certain period of time, and then a solvent is introduced and wet mixing is performed for a predetermined period of time to prepare a slurry, and a doctor blade. Create a green sheet by law. By using the green sheet produced by such a method as the outermost layer or the surface layer, a ceramic multilayer wiring board having a dense outermost layer or surface layer is obtained. Further, a green sheet in which the flux component is reduced as compared with the conventional one is prepared, and this green sheet is used as the outermost layer or the surface layer, whereby a ceramic multilayer wiring board having a dense outermost layer or the surface layer is obtained.

Furthermore, by combining the above two manufacturing methods, that is, by weighing the powder material so that the flux component of the green sheet used for the outermost layer or the surface layer is lower than that of the inner layer,
The dry mixing is performed for a certain period of time, and then the wet mixing is performed to use the green sheet as the outermost layer or the outermost layer to obtain a ceramic multilayer wiring board having a dense outermost layer or the outermost layer.

[0006]

By performing the dry mixing, each powder material is crushed into fine particles, and the filling property of the powder itself is improved.
Since a green sheet is prepared by adding a solvent to the powder material in this state and then performing wet mixing, the green sheet itself becomes dense. That is, the powder material, which has been made fine by dry mixing, enters into the voids in the case of the conventional method, and the voids are filled or become small, so that the green sheet becomes dense. By using this green sheet as the outermost layer or surface layer, even if the flux component is similar to that of the green sheet used for the inner layer, the void component is smaller than that of the inner layer, so the flux component that melts during sintering becomes easier to fill the void. Therefore, it is possible to obtain a ceramic multilayer wiring board in which voids in the outermost layer or the surface layer are reduced.

Further, when a green sheet having a reduced flux component as compared with the inner layer is used for the outermost layer or the surface layer, the amount of the flux component which becomes a liquid phase by being melted during the temperature rise of sintering is small, so that voids between the mullite grains are formed. The gasified substances such as the binder cannot be easily removed. After that, the flux component in the liquid-state inner layer penetrates into the outermost layer or the surface layer to fill the voids and promote the grain growth of mullite, so that the gas remaining in the structure is reduced and the voids are reduced.

Further, by combining the above two manufacturing methods, the voids in the outermost layer or the surface layer are further reduced by the synergistic effect of the two.

[0009]

EXAMPLE In FIG. 1, the green sheet used for the inner layer 2 has a flux component (silica, alumina, magnesium carbonate) of 28 ωt% against a mullite component of 72 ωt%.
As shown in FIG. 2, the manufacturing method is obtained by wet mixing a predetermined amount of powder material and binder weighed in the above ratio with a predetermined amount of solvent in a ball mill for 15 hours. The resulting slurry is vacuum deaerated, adjusted to a predetermined viscosity, and then prepared by the doctor blade method. Through holes 3 are formed in the green sheet formed by this method, and after filling the conductive paste, a plane pattern is formed by screen printing. The green sheet thus produced is used as the inner layer 2, and the green sheet produced by any of the following methods is used as the outermost layer or the surface layer 1 to form through holes and patterns, and after stacking the layers, a laminate obtained by thermocompression bonding Is sintered according to a predetermined profile to obtain a ceramic multilayer wiring board having a small void 4 in the outermost layer or surface layer 1.

The voids in the inner layer were 30 μm or less.

Next, a method for manufacturing a green sheet used for the outermost layer or the surface layer 1 will be described based on the above claims.

Example 1 As a first method, as shown in FIG. 3, powder materials and a binder were dry mixed in a ball mill for 20 hours in a weight ratio similar to that of the green sheet used for the inner layer 2, and then, A green sheet obtained by processing the slurry obtained by wet mixing for 15 hours by adding the same amount of the solvent as the inner layer 2 to the outermost layer or the surface layer 1 by the same method as the inner layer 2 is used. A ceramic multilayer wiring board having voids 4 in the outermost layer or surface layer 1 of 20 μm or less was obtained.

Example 2 As a second method, as shown in FIG. 4, the flux component was 14 ωt%, and the powder material, binder and solvent were weighed so that the component ratio was lower than that of the green sheet used for the inner layer 2. A green sheet prepared by wet-mixing for 15 hours in a ball mill and processed by the same method as the inner layer 2 is used as the outermost layer or the surface layer 1. A ceramic multilayer wiring board having a void 4 of 15 μm or less was obtained.

Example 3 As a third method, as shown in FIG. 5, a green sheet produced by combining the methods shown in the first and second methods, that is, the flux component is 14 ωt% lower than that of the inner layer 2. The powdered material and a specified amount of binder,
A slurry obtained by dry mixing for 20 hours in a ball mill, then adding a predetermined amount of solvent and wet mixing for 15 hours,
By using a green sheet prepared by the same method as the inner layer 2 as the outermost layer or the surface layer 1, a ceramic multilayer wiring board having voids 4 in the outermost layer or the surface layer 1 of 10 μm or less was obtained.

[0015]

EFFECTS OF THE INVENTION Even if voids in the outermost layer or surface layer appear on the substrate surface by surface polishing performed before forming a thin film on a ceramic multi-layer wiring substrate, if the wiring is twice the void diameter or more, the thin film Even if the wiring pattern is formed, it is possible to prevent defects such as opens and shorts.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a ceramic multilayer wiring board having a structure in which a void diameter included in an outermost layer or a surface layer is smaller than a void diameter in an inner layer.

FIG. 2 Method for manufacturing inner layer green sheet (prior art)
Is.

FIG. 3 is a method (1) for producing an outermost or surface green sheet.

FIG. 4 is a manufacturing method (2) of the outermost layer or surface green sheet.

FIG. 5 is a method (3) for producing an outermost layer or surface green sheet.

[Explanation of symbols]

 1 ... Outermost layer or surface layer of ceramic multilayer wiring board, 2 ... Inner layer of ceramic multilayer wiring board, 3 ... Through hole, 4 ... Void.

Claims (4)

[Claims] 1. A ceramic multilayer wiring board obtained by stacking a predetermined number of green sheets printed with a conductor paste containing a high-melting-point conductive material as a main component and sintering the green sheets, or an outermost layer (two front and back layers) or one surface layer. A ceramic multilayer wiring board characterized in that the void diameter inside is smaller than other layers (inner layers) and has a dense structure. 2. The method for manufacturing a ceramic multilayer wiring board according to claim 1, wherein the green sheet used for the outermost layer or the surface layer is prepared by dry mixing powder materials for a certain period of time and then wet mixing them by adding a solvent. The ceramic multilayer wiring board characterized in that the green sheet used for the inner layer is prepared by simultaneously mixing the powder material and the solvent. 3. The method for manufacturing a ceramic multilayer wiring board according to claim 1, wherein the green sheet used for the inner layer has a composition of mullite component 70 to 74 ωt% and flux component (alumina / silica / magnesium carbonate) 26 to 30 ωt%. The green sheet used for the outermost layer or surface layer has a composition of mullite component of 80 to 100 ωt% and flux component of 0 to 20ωt%. As a ceramic multilayer wiring board production, the flux in the outermost layer or the surface layer is higher than that of the inner layer. A ceramic multi-layer wiring board characterized by having less components. 4. The method for manufacturing a ceramic multilayer wiring board according to claim 1, wherein the green sheet used in combination with claim 2 and claim 3, that is, the outermost layer or the surface layer is a mullite component of 80 to 100 ωt%, Flux component 0
The green sheet used for the inner layer is a mullite component 70 to 74 ωt% and a flux component 26.
A ceramic multilayer wiring board, characterized in that a powder material weighed so as to be ˜30 ωt% is prepared only by wet mixing.