JP3242459B2 - Manufacturing method of ceramic wiring board - Google Patents

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 wiring board.

[0002]

2. Description of the Related Art In a ceramic wiring board used in the field of electronic materials, particularly in the field of hybrid ICs, a circuit of a predetermined pattern is conventionally formed by screen printing and baking a conductive paste (copper paste, etc.) on the surface of a ceramic substrate. Thereafter, a thick resistor layer is formed by baking. However, this method has problems that it is difficult to miniaturize the circuit and that the conductive paste contains vitreous material, so that solder adhesion is poor, defective products are easily generated, and there are many failures during use.

Therefore, a conductive film is formed by electroless plating on the surface of a ceramic substrate without using a conductive paste to form a circuit, and selective etching is performed to provide a ceramic conductive layer having a predetermined pattern of a circuit conductive layer on the surface. After obtaining the substrate, a thick resistor layer may be formed by baking. In this case, since the conductor layer is basically made of metal, the resistance of the circuit is low, and the circuit can be miniaturized by applying a fine patterning technique using a photolithography technique.

However, in this case, there is the following problem. After forming the resistor layer, a metal film may be formed on the surface of the conductor layer by a plating method. For example, if the conductor layer is copper,
Gold plating is performed on the conductor layer in order to impart chip die bondability or wire bondability. Thereafter, when chip die bonding or wire bonding is performed, the conductor layer is peeled off from the surface of the ceramic substrate, causing blisters, thereby causing a circuit damage.

[0005]

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention provides a printed wiring board obtained by forming a metal film by plating after forming a resistor layer on a conductor layer on the surface of a ceramic substrate. It is an object of the present invention to provide a method which can be manufactured so that blisters of a conductor layer are hardly generated by high-temperature treatment.

[0006]

In order to solve the above problems, a method for manufacturing a printed wiring board according to the present invention comprises:
After baking and forming a resistor layer on a ceramic substrate provided with a conductor layer on the surface, and then forming a metal film on the surface of the conductor layer by a plating method, a conductor formed by a plating method as the ceramic substrate is used. a layer, a conductor layer at least one of the ceramic particles or metal particles are dispersed is to use a ceramic substrate provided.

Hereinafter, the present invention will be described more specifically.
The ceramic substrate itself used in the present invention is suitably of a sintered ceramic type, and the material is an oxide based material such as alumina, forstenite, zirconia, mullite, cordierite, titania, barium titanate, and calcium titanate. Are mainly used, but carbide-based ceramics such as silicon carbide, nitride-based ceramics such as aluminum nitride may be used, or a plurality of types of ceramics may be used in combination.

The ceramic substrate is preferably preliminarily subjected to a surface roughening treatment so as to increase the adhesion of the conductor layer on the surface. Examples of the surface roughening include mechanical surface roughening using sandblasting or the like and chemical surface roughening using a processing agent such as hot phosphoric acid. In the present invention, a conductive film containing ceramic particles and metal particles is formed on the surface of the ceramic substrate after the surface roughening treatment, but the metallization method in this case is not limited to a specific method. However, electroless plating or electrolytic plating in which ceramic particles or metal particles are added to a plating bath to disperse the particles in a conductive film is easy to use. In the case of electrolytic plating, it is necessary to form a base metal layer in advance.

[0009] Examples of the kind of metal which is a main material of the conductive film include copper and nickel. On the other hand, ceramic particles and metal particles dispersed in the conductive film are particles having a function of suppressing crystal growth in a conductor layer for a circuit during heating, and are not limited to specific particles, but have an average particle size. 3
Particles having a particle size of 0 μm or less are preferable, and examples thereof include ceramic particles such as alumina particles and metal particles such as nickel particles. The content of the ceramic particles and the metal particles in the conductive coating is usually in the range of 40% or less, and about 10 to 30% as seen in Examples described later. If it exceeds 40%, there is a tendency that the film adhesion and the conductivity are greatly reduced.

[0010] The thickness of the conductive coating containing ceramic particles and metal particles is not limited to a specific thickness, but is preferably 2 µm or more. The ceramic particles and metal particles need not be dispersed throughout the conductive coating. For example, a portion (lower layer) from the surface of the ceramic substrate to a certain height has particles dispersed therein, and a portion above the upper portion (upper layer) has no particles dispersed therein and is a conductive film having a multilayer structure of a pure metal layer. It may be. After all, the formation of the particle-dispersed portion is more troublesome than the formation of the non-dispersed portion of the particle, so that it is easier to produce the particle-dispersed portion only in the required area.

The conductive film thus formed is patterned by selective etching using a photolithography technique or the like, and a conductive layer for a circuit is provided on the surface of the ceramic substrate. This method of forming a conductor layer for a circuit is called a subtractive method, but in the case of the present invention, the conductor layer is not limited to that provided by the subtractive method, and may be formed by another method such as a so-called additive method or a semi-additive method. It may be provided by a method.

After the circuit conductor layer is thus provided, the resistor layer is formed. The resistor layer can be formed by applying and baking a resistor paste. After baking, trimming may be performed as necessary to adjust the resistance value. Examples of the resistor paste include pastes of LaB ₆ type, SnO ₂ type, etc., which are baked by firing in a nitrogen atmosphere.
Alternatively, a paste such as a RuO ₂ paste that is baked by baking in air is mainly used, but is not particularly limited. The former paste is not particularly problematic, but when using the latter paste such as RuO ₂ based firing in air, when the conductive layer is a metal to be oxidized such as copper,
It is necessary to reduce oxidized copper in a reducing atmosphere (for example, a mixed atmosphere of hydrogen and nitrogen). These pastes usually have a firing temperature of about 800 to 950 ° C.

After the formation of the resistor layer, a metal film is formed on the conductor layer by plating. The type of metal coating,
Although not limited to a specific metal, for example, nickel, gold and the like can be mentioned. The metal coating may be a composite coating comprising a plurality of different types of metal layers. The type of plating bath, plating method, operating conditions, and the like in the plating method for forming a metal film are not particularly limited.

[0014]

According to the method for manufacturing a ceramic wiring board of the present invention,
After forming the resistor layer, a printed wiring board is obtained by forming a metal coating on the conductor layer on the surface of the ceramic substrate by plating, but since the ceramic particles and metal particles are dispersed in the conductor layer, the subsequent Swelling of the conductor layer is hardly caused by the high-temperature treatment.

In the firing for forming the resistor layer, the crystal growth rate of the conductor layer is suppressed by ceramic particles and metal particles, so that the crystal grain size does not change much and many crystal grain boundaries exist. On the other hand, when the particles are not dispersed, the crystal growth proceeds and the crystal grain size increases, and the crystal grain boundaries decrease. on the other hand,
Thereafter, when a metal film is formed on the conductor layer by a plating method, a plating solution or the like is occluded near the surface of the conductor layer, and the occluded plating solution or the like gasifies and penetrates into crystal grain boundaries. In the case of the printed wiring board of the present invention, a large number of crystal grain boundaries are present, and the invading gas is dispersed and dispersed well in all directions, so that the gas does not reach the interface between the conductor layer and the ceramic substrate, and blisters are unlikely to occur . On the other hand, in the conventional case, since the crystal grain boundaries are small, the gas does not diffuse much and is not absorbed, but reaches the interface between the conductor layer and the ceramic substrate, so that blisters are easily generated.

Therefore, in the case of the present invention, it is possible to avoid occurrence of blisters in the manufactured printed wiring board due to heating during chip die bonding or wire bonding.

[0017]

Embodiments of the present invention will be described below. Of course,
It goes without saying that the present invention is not limited to the following embodiments. FIG. 1 shows a configuration of a main part of the printed wiring board obtained in the first and second embodiments, and FIG. 2 shows a main configuration of the printed wiring board obtained in the third embodiment.

Example 1 As a ceramic substrate, an alumina substrate having a 6 μm-thick electroless copper-plated copper coating (conductive coating) in which alumina particles having an average particle size of 1 μm are dispersed at a content of 20% was formed. 1 was used. By subjecting the copper film of the alumina substrate 1 to a selective etching process, a desired pattern was formed, and a copper conductive layer 2 for a circuit was formed.

Subsequently, a LaB ₆ -based resistor paste is printed at a predetermined position, baked and baked at 900 ° C. in a nitrogen atmosphere to form a resistor layer 3, and then a copper conductive layer 2 for a circuit is formed. Forming a metal coating 4 consisting of a 1 μm thick gold layer 4 b on a 5 μm thick nickel layer 4 a by plating on the surface,
A ceramic wiring board was obtained. The heat resistance of the ceramic wiring board thus obtained was evaluated by a heat treatment at 500 ° C. for 10 minutes. As a result, no abnormality such as blisters was observed on the surface of the coating.

Example 2 As a ceramic substrate, an alumina substrate 1 having a 6 μm-thick electroless copper-plated copper coating (conductive coating) in which nickel particles having an average particle size of 1 μm are dispersed at a content of 15%. Was used. As shown in FIG. 1, by subjecting the copper film on the alumina substrate to a selective etching process, a desired patterning was performed, and a copper conductive layer 2 for a circuit was formed.

Subsequently, a LaB ₆ -based resistor paste is printed at a predetermined position, baked and baked at 900 ° C. in a nitrogen atmosphere to form a resistor layer 3, and then a copper conductive layer 2 for a circuit is formed. Forming a metal coating 4 consisting of a 1 μm thick gold layer 4 b on a 5 μm thick nickel layer 4 a by plating on the surface,
A ceramic wiring board was obtained. The heat resistance of the ceramic wiring board thus obtained was evaluated by a heat treatment at 500 ° C. for 10 minutes. As a result, no abnormality such as blisters was observed on the surface of the coating.

Example 3 As a ceramic substrate, particles were dispersed on a 3 μm-thick electroless copper-plated copper coating (lower conductive coating) in which alumina particles having an average particle size of 1 μm were dispersed at a content of 20%. An alumina substrate 1 having a conductive film formed by laminating a 3 μm-thick electroless copper electroplated copper film (pure copper film, upper conductive film) is used. The conductive layer 2 is made of alumina particles. A ceramic wiring board was obtained in the same manner as in Example 1, except that a copper conductive layer 2a containing 20% and a copper conductive layer 2b containing no alumina particles were laminated.

The heat resistance of the ceramic wiring board thus obtained was evaluated by heat treatment at 500 ° C. for 10 minutes. As a result, no abnormality such as blisters was observed on the surface of the coating. Comparative Example 1 The same procedure as in Example 1 was carried out except that an alumina substrate having an electroless copper-deplated copper film (pure copper film, film thickness: 6 μm) in which alumina particles were not dispersed was used as a ceramic substrate. Thus, a ceramic wiring board was obtained.

The heat resistance of the ceramic wiring board thus obtained was evaluated by heat treatment at 500 ° C. for 10 minutes. As a result, it was observed that blisters occurred on the surface of the coating. From the observation results of the examples and the comparative examples, it is clearly understood that in the case of the present invention, the occurrence of blisters can be prevented by dispersing the ceramic particles and metal particles in the conductive layer.

[0025]

According to the present invention, a printed wiring board is obtained by forming a metal coating on the conductor layer on the surface of the ceramic substrate by plating after the formation of the resistor layer. Ceramic particles and metal particles are dispersed in the conductor layer, and in firing for forming the resistor layer, the crystal grain size does not change much and there are many crystal grain boundaries, so in high temperature treatment after plating formation of the metal film, The absorbed plating solution or the like is dispersed in all directions and is well absorbed, does not reach the interface between the conductor layer and the ceramic substrate, and is less likely to cause blisters, which is very useful.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a main configuration of a printed wiring board obtained in Examples 1 and 2.

FIG. 2 is a cross-sectional view illustrating a configuration of a main part of a printed wiring board obtained in Example 3.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 ceramic substrate 2 copper conductive layer (conductive layer) 3 resistor layer 4 metal coating

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Masaya Koyama 1048 Kazuma Kadoma, Kadoma-shi, Osaka Matsushita Electric Works, Ltd. (56) References JP-A-1-313803 (JP, A) JP-A-58-71507 ( JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C04B 41/80-41/91

Claims (1)

(57) [Claims] 1. A method for manufacturing a ceramic wiring board, comprising: forming a resistor layer on a ceramic substrate having a conductor layer provided on a surface thereof by baking; and forming a metal coating on a surface of the conductor layer by plating. As the ceramic substrate, a conductive layer formed by a plating method, wherein a ceramic substrate provided with a conductive layer in which at least one of ceramic particles or metal particles is dispersed is used. Production method.