JPH0664990A - Production of metallized ceramic substrate - Google Patents

Abstract

PURPOSE:To provide a method for producing a metallized ceramic substrate in which the metallized ceramic substrate capable of avoiding the occurrence of blister produced in a part of the metallic film due to heating in the subsequent step performed after producing the metallized ceramic substrate can stably be produced. CONSTITUTION:This objective method for producing a metallized ceramic substrate comprises forming a metallic film containing organic particles with a plating bath containing the organic particles dispersed therein and then heat- treating the resultant film at a higher temperature than the boiling point of the organic particles in forming the metallic film on the surface of the ceramic substrate with the plating bath.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a metallized ceramic substrate used for producing a ceramic wiring board, a heat dissipation plate and the like.

[0002]

2. Description of the Related Art Generally, a ceramic wiring board uses a so-called thick film method in which a conductive circuit is formed by printing a conductive paste on a surface of a ceramic substrate in a predetermined pattern using a screen printing machine. ing. However, in the case of the thick film method, it is difficult to control the film thickness of the conductor circuit, the electrical characteristics and mechanical characteristics of the obtained conductor circuit are not sufficient, and the precision is not so good that it is difficult to miniaturize the circuit. There is a problem of

Therefore, the use of a metallized ceramic substrate in which the precision and miniaturization of the conductor circuit can be achieved, that is, a ceramic substrate in which a metal film is formed on the surface of the ceramic substrate by a method such as electroless plating, has been studied and put to practical use. Is also provided. In the case of a metallized ceramic substrate, a conductor circuit having a predetermined pattern can be formed by using a photographic method capable of highly precise fine patterning, and the resistance value is also low because the conductor circuit is made of metal. .

However, in the above metallized ceramic substrate, the adhesion between the metal film and the ceramic substrate (adhesive strength)
Is not enough. When a wiring board is manufactured using a metallized ceramic substrate, heat treatment is performed for various purposes in processes such as circuit formation and electronic component mounting.However, during these heat treatments, blisters ( Local peeling) occurs, and the adhesion state between the metal film and the ceramic substrate becomes poor.

The blisters generated on the metal film are due to the inclusion of the plating solution component in the film or the like during the process of depositing and growing the metal film by the plating method. The entrapped plating liquid component does not escape when it is gasified in the subsequent heat treatment and causes volume expansion to generate blisters. As a measure for preventing the blistering of the metal film, Japanese Patent Application Laid-Open No. 1-16
Japanese Patent No. 4786 proposes that the metal film has a crystal structure with a gap through which gas can escape. However, this measure is not practical.

One is that it is difficult to stably produce a metal film having a crystal structure with a gap through which gas can escape. It is difficult to stabilize the crystal structure of the metal film because the crystal structure of the metal film changes depending on the amount of accumulated salt, which is a plating aged substance. The other is that if the metal film becomes thicker, the gas inside cannot escape well. The gap in the crystal structure of the metal film is very narrow, and if the metal film is thick, it becomes difficult for gas to escape.

[0007]

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention is a metallized ceramic substrate capable of avoiding blistering on a part of a metal film due to a heat treatment in a post process performed after the production of the metallized ceramic substrate. It is an object of the present invention to provide a method capable of producing a stable product.

[0008]

In order to solve the above-mentioned problems, in the method for manufacturing a metallized ceramic substrate according to the present invention, when a metal film is formed on the surface of the ceramic substrate by using a plating method, organic particles are used. A metal film containing the organic particles is formed on the surface of the ceramic substrate with the dispersed plating bath, and then heat treatment is performed at a temperature equal to or higher than the boiling point of the organic particles.

The present invention will be specifically described below. The material of the ceramic substrate itself used in the present invention includes alumina, forsterite, steatite, zirconia,
Oxide-based ceramics such as mullite, cordierite, titania, barium titanate, and calcium titanate are mainly used, but carbide-based ceramics such as silicon carbide and nitride-based ceramics such as aluminum nitride are used. Alternatively, plural kinds of ceramics may be used in combination.

The ceramic substrate is preferably preliminarily subjected to a surface roughening treatment which exhibits an anchor effect so that the adhesion of the conductor layer on the surface is enhanced. As roughening treatment,
There are mechanical surface roughening treatment using sandblasting and chemical surface roughening treatment by etching with a surface roughening agent. Examples of the surface-roughening agent include phosphoric acid, boric acid, and H.
Examples include F, solutions of alkali metal compounds, melts, and the like.

As the plating method used in the present invention, electrolytic plating may be used in addition to electroless plating.
When the metal film is formed by electroless plating, it is preferable to apply a catalyst as an activation treatment on the surface of the ceramic substrate. As a method of applying the catalyst, for example, the catalyst is P
In the case of d, there are sensitizing-activation method, catalyst-acceleration method, etc., but the kind and applying method of the catalyst are not limited to these examples, and they contribute to the deposition of the electroless plating film. I wish I had it.

The electroless plating solution used in the present invention is, for example, Cu (II), EDTA, NaOH (pH
(For control), HCHO as a basic component, and if necessary, additives such as stabilizers that suppress the decomposition of the plating solution, accelerators that improve the plating rate, and modifiers that improve the state of the plating film are added. Examples include liquids, but needless to say, they are not limited to these.

In the case of the present invention, since the ceramic substrate is plated in an electroless (or electrolytic) plating bath in which organic particles are dispersed, the organic particles are insoluble, inactive, and non-catalytic in the plating solution. However, those having a low boiling point are preferable. Specific materials for the organic particles include naphthalene,
There are anthracene, naphthacene and the like, which are not limited to specific ones, but those having a boiling point of 400 ° C. or less are preferable.

The organic particles preferably have a small particle size and are not limited, but particles having an average particle size of 10 μm or less are preferable. The amount of organic particles added to the plating solution is also
Although not particularly limited, it is usually 5 to 5 by weight.
The range is 50%. If it is less than 5%, the effect of preventing blistering of the metal film tends to be insufficient, and 50%
If it exceeds the range, it becomes difficult to uniformly disperse the organic particles in the plating solution.

As a method of dispersing the organic particles in the plating solution, for example, there is a method of circulating the plating solution or a method of mechanically stirring the plating solution, but it is not limited to a specific method. Further, in order to uniformly disperse the organic particles in the plating solution, an additive such as a surfactant may be added if necessary. In the case of the present invention, a metal film containing the organic particles is formed on the surface of the ceramic substrate in a plating bath in which the organic particles are dispersed, and then heat treatment is performed at a temperature equal to or higher than the boiling point of the organic particles. By this heat treatment, the organic particles are removed from the metal film, and the traces become gaps, so that the metal film becomes porous and a metallized ceramic substrate is obtained.

The amount and size of the gap of the metal film mainly depend on the particle size and the content of the organic particles to be contained, and the amount of the gap and the size can be adjusted by adjusting the particle size and the content of the organic particles. You can control the size. The heat treatment for removing the organic particles is preferably performed under conditions of a heating temperature of 400 ° C. or lower and a heating time of 10 minutes or longer. 400 ° C
If the temperature exceeds 1, the plating solution component (gas source) is gasified before the organic particles are removed from the metal film and a gap is formed, and it is impossible to prevent the generation of blisters. Further, if the heating time is less than 10 minutes, the organic particles cannot be sufficiently removed, and there is a strong tendency that the gaps necessary to remove the gas causing blisters cannot be formed.

The metallized ceramic substrate of the present invention may be in a stage after the heat treatment for removing the organic particles. Since there is a sufficient gap in the metal film, the plating solution components will come out well in the subsequent heat treatment. In addition to this, the metallized ceramic substrate of the present invention further has the following features:
Further, it may be at a stage where the metal film is densified.

In the metallized ceramic substrate obtained by the heat treatment for removing the organic particles, when the conductivity of the metal film is insufficient, for example, the following heat treatment is carried out to remove the plating solution component. Alternatively, the porous metal film may be densified. That is,
After removing the organic particles, the metallized ceramic substrate is heated under a reduced pressure of 750 mmHg or less in the range of 400 to 800 ° C. for 10 to 30 minutes to evaporate the plating solution components near the surface of the ceramic substrate and in the metal film. Let it escape, and then 800 to 1000 in a nitrogen gas atmosphere.
By heating at 90 ° C. for 90 minutes or more, the metal film is recrystallized, the density of the metal film is increased, and the conductivity is improved.

[0019]

In the method of manufacturing a metallized ceramic substrate of the present invention, a metal film containing organic particles is formed on the surface of the ceramic substrate, and heat treatment is performed at a temperature higher than the boiling point of the organic particles. The particles are detached so that the metal film has a sufficient gap (porous). as a result,
The plating solution component (gas source) in the vicinity of the surface of the ceramic substrate or in the metal film can be discharged from the gap, and the occurrence of blisters can be sufficiently prevented.

Further, the gap is a trace of organic particles irrelevant to the crystal structure, and a sufficient gap can always be formed in the metal film, and as a result, the metallized ceramic substrate can be stably manufactured.

[0021]

Embodiments of the present invention will be described below. Of course,
The present invention is not limited to the embodiments described below. -Example 1-After chemically roughening the surface of a ceramic substrate with hot phosphoric acid, palladium is nucleated, and copper sulfate and EDT are used.
A, formalin and sodium hydroxide as basic components in the proportions shown in Table 1 and 5 naphthalene having an average particle size of 1 μm
Plating was performed in an electroless copper plating bath having a weight% dispersed therein.
During plating, the plating bath was agitated with air.
A 30 μm-thick copper film containing naphthalene particles was formed on the surface of the ceramic substrate.

Then, the ceramic substrate on which the copper film is formed is placed in an electric furnace and heat-treated at 350 ° C. for 30 minutes,
The copper film was made porous by removing the naphthalene particles. Then, heat treatment is performed at 500 ° C. for 30 minutes in an electric furnace depressurized to 10 mmHg to remove the plating solution components contained in the copper film as a gas, and then the electric furnace is used to remove nitrogen atmosphere. The copper film was densified by heating at 900 ° C. for 90 minutes.

Example 2 The anthracene particles were removed in the same manner as in Example 1 except that the organic particles used were anthracene particles having an average particle size of 1 μm, and then the copper film was densified. went. -Example 3-The naphthalene particles were removed in the same manner as in Example 1 except that naphthalene particles having an average particle diameter of 5 µm were used as the organic particles, and then the copper film was densified.

Example 4 The naphthalene particles were removed in the same manner as in Example 1 except that the naphthalene particles having an average particle size of 10 μm were used as the organic particles, and then the copper film was densified. went. -Example 5-The naphthalene particles were removed in the same manner as in Example 1 except that the amount of the naphthalene particles dispersed in the plating solution was 30% by weight, and then the copper film was densified.

Example 6 The naphthalene particles were removed in the same manner as in Example 1 except that the dispersion amount of the naphthalene particles in the plating solution was 50% by weight, and then the copper film was densified. It was -Example 7- As shown in Table 1, a plating solution containing an accumulated salt having a specific gravity of 1.10 was used, and 5 wt% of naphthalene particles having an average particle size of 1 µm were dispersed therein. In the same manner as in Example 1, the naphthalene particles were removed, and then the copper film was densified.

-Comparative Example 1- Using the plating solutions shown in Table 1, electroless plating was carried out without dispersing the naphthalene particles to obtain metallized ceramic substrates. -Comparative Example 2- A metallized ceramic substrate was obtained by performing electroless plating without dispersing naphthalene particles while using a plating solution having a composition shown in Table 1 and a specific gravity of 1.10.

[0027]

[Table 1]

With respect to the metallized ceramic substrates obtained in Examples and Comparative Examples, heat resistance and volume resistivity of the copper film were examined. Regarding heat resistance, heating was performed at 950 ° C. for 10 minutes in an electric furnace in a nitrogen atmosphere, and it was examined whether blistering occurred in the copper film (poor heat resistance) or not (good heat resistance). . The volume resistivity of the copper film is
It was measured according to JIS-C2525. The measurement results are shown in Table 2 together with the particle size of the organic particles.

[0029]

[Table 2]

As can be seen from the measurement results shown in Table 2, in the case of the embodiment, even if the copper film is as thick as 30 μm, there is sufficient heat resistance, and the formation of gaps by dispersion and heating removal of the organic particles in the metal film, It turns out that it is very effective. Further, it can be seen that the volume resistivity of the copper film is not much different from the conventional one, and is sufficiently within the practical range.

[0031]

The metallized ceramic substrate obtained by the manufacturing method of the present invention is formed by forming a metal film containing organic particles on the surface of the ceramic substrate and heat-treating it at a temperature not lower than the boiling point of the organic particles. Release the organic particles,
Since the metal film is in a state with a sufficient gap (porous), the plating solution component (gas source) in the vicinity of the surface of the ceramic substrate or in the metal film can be discharged from the gap, and the blistering of the metal film is sufficiently generated. In addition, the gap is a trace of organic particles that have nothing to do with the crystal structure, and a sufficient gap can always be created in the metal film, resulting in blistering in the metal film. It is possible to stably manufacture a metallized ceramic substrate that does not have metalized ceramics.

Claims (2)

[Claims] 1. A method for producing a metallized ceramic substrate, wherein a metal film is formed on the surface of a ceramic substrate by a plating method, wherein the organic system is formed on the surface of the ceramic substrate with a plating bath in which organic particles are dispersed. A method for producing a metallized ceramic substrate, comprising forming a metal film containing particles, and then performing heat treatment at a temperature equal to or higher than the boiling point of the organic particles. 2. The electroless plating is used as the plating method.
A method for producing the metallized ceramic substrate described.