JPH0426560B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a ceramic wiring board, and in particular, the present invention relates to a method of manufacturing a ceramic wiring board, and in particular, the present invention relates to a method of manufacturing a ceramic wiring board, and in particular, the present invention relates to a method of manufacturing a ceramic wiring board, and in particular, the present invention relates to a method of manufacturing a ceramic wiring board, and in particular, the present invention relates to a method of manufacturing a ceramic wiring board, and in particular, the present invention relates to a method of manufacturing a ceramic wiring board, and in particular, the present invention relates to a method of manufacturing a ceramic wiring board, and in particular, the present invention relates to a method of manufacturing a ceramic wiring board, and in particular, the present invention relates to a method of manufacturing a ceramic wiring board. The present invention relates to a method of manufacturing a ceramic wiring board.

[Conventional technology]

In recent years, with advances in the electronics industry, electronic devices have become smaller and faster, and as part of this, wiring boards on which hybrid ICs and LSIs are mounted are also required to have higher density and higher reliability.

Ceramic materials, which are excellent in reliability, dimensional stability, heat dissipation, etc., are widely used as substrate materials for the wiring boards, and as a method for forming conductor circuits on hybrid IC wiring boards made of the ceramic materials. For example, a method of screen printing and firing a thick film conductor paste such as a silver/palladium paste is generally applied.

However, the conductor formed by the thick film paste has a high sheet resistance, which is the most important, high frequency transmission loss, a practical limit of fine line property of 0.20 mm width, and poor solderability and bonding properties. However, it had the disadvantage of being inferior to that of silver, and furthermore, it was necessary to pay attention to silver migration.

As a method for forming conductors that can solve these drawbacks, a method of forming conductors on ceramic substrates by electroless plating has recently been proposed, but conductors formed by electroless plating do not adhere well to the substrate material. Various studies have been conducted to improve this adhesive property.

For example, the 11th edition distributed on April 11, 1985.
ISHM JAPAN Technical Lecture Proceedings Volume 9~
As described on page 17, a method is known in which electroless plating is performed by chemically etching the surface of a ceramic substrate in advance to roughen the surface of the substrate material and exert an anchor effect. Furthermore, Japanese Patent Application Laid-Open No. 54-25469 discloses an invention related to a "method for manufacturing a printed wiring board."

However, with the method described in the aforementioned lecture proceedings, it is quite difficult to uniformly etch and roughen the entire surface of a ceramic substrate, and the adhesive strength of conductors made of electroless plating tends to vary, making it unreliable. There were flaws. Furthermore, according to the method described in the above publication, it is stated that it can also be applied to ceramic plates, but this invention is a method that uses an adhesive containing crystalline polybutadiene resin as an adhesive layer, and is applicable to ceramic plates. It has the disadvantage that it does not have sufficient heat resistance, which is an important property for a wiring board.

[Problem that the invention seeks to solve]

As mentioned above, conventionally known methods include forming a conductor by electroless plating, which has excellent heat resistance and reliability of adhesion between a ceramic substrate and electroless plating, and thin ceramic wiring with excellent heat dissipation properties. The method of manufacturing the substrate is not yet known.

The present invention eliminates the above-mentioned drawbacks of ceramic wiring boards, forms a conductor using electroless plating that has extremely excellent heat resistance and reliability of adhesion between the ceramic board and electroless plating, and at the same time provides thin heat dissipation properties. The object of the present invention is to provide a method for manufacturing an excellent ceramic wiring board, and the above object can be achieved by providing the method described in the claims.

[Means for solving problems]

According to the present invention, a synthetic resin containing inorganic fine particles is applied to the surface of a ceramic substrate to form an adhesive layer, and the surface of the adhesive layer is removed to expose a portion of the inorganic fine particles on the surface of the adhesive layer. After that, the exposed inorganic fine particles are dissolved and removed to roughen the surface of the adhesive layer, and then electroless plating is performed to form a conductive layer. _The present invention relates to a method for producing a ceramic wiring board, characterized in that the thickness of the adhesive layer is 10 μm or less.

The present invention will be explained in detail below.

In the present invention, a synthetic resin containing inorganic fine particles is applied to the surface of a ceramic substrate to form an adhesive layer, and the surface of the adhesive layer is removed to expose a part of the inorganic fine particles on the surface of the adhesive layer. Thereafter, it is necessary to dissolve and remove the exposed inorganic fine particles to roughen the surface of the adhesive layer.

The reason why a synthetic resin containing inorganic fine particles is used for the adhesive layer is that inorganic fine particles have excellent heat resistance and insulation properties, and when they are dissolved and removed, clear anchors are formed and the surface of the adhesive layer is uniform. This is because high bonding strength and bonding reliability between the ceramic substrate and the electroless plating can be obtained since the ceramic substrate can be roughened to a high degree. Further, the reason why a part of the inorganic fine particles is exposed on the surface of the adhesive layer is as follows.
The objective is to effectively and uniformly dissolve the inorganic fine particles present on the surface of the adhesive layer over the entire surface of the adhesive layer.

By the way, as a method for improving the adhesion of electroless plating in the manufacture of printed wiring boards, an invention related to a ``method for manufacturing a laminate'' is disclosed in Japanese Patent Application Laid-open No. 50-42377. This is a method of electroless plating on substrate materials made of organic laminates such as epoxy varnish cloth, and the adhesive strength between the resulting plating conductor and laminate is determined by peel strength.
In contrast, according to the present invention, a ceramic material with excellent heat resistance is used as the substrate material, and the adhesive strength of the obtained conductor is 1.0 Kg/cm, which is sufficient for practical use. Extremely high values of cm or more can be obtained. As mentioned above, the above invention and the present invention are completely different in the type of substrate material used and the value of the adhesive strength obtained.

The ceramic substrate used to carry out the present invention preferably has an electrical resistance (volume resistivity) of 10 ⁸ Ω-cm or more. The reason for this is that when the electrical resistance is lower than 10 ⁸ Ω-cm, the thickness of the adhesive layer having electrical insulation properties is increased to ensure electrical insulation between the conductor made of electroless plating and the ceramic substrate. This is because the heat dissipation property, which is an important characteristic of a ceramic wiring board, will be greatly reduced. In addition, the material of the ceramic substrate is
Alumina, beryllia, mullite, low temperature fired ceramics, dielectric ceramics, aluminum nitride, silicon carbide, etc. can be used.

As the synthetic resin, any material can be used as long as it has excellent thermal properties, electrical insulation properties, adhesive properties, etc. Heat-resistant thermosetting resins are particularly preferred, and among them, epoxy resins, heat-resistant epoxy resins,
Epoxy modified polyimide resin, polyimide resin,
Preferably, at least one selected from triazine resins is used.

The inorganic fine particles used in the present invention have an average particle size of
It is necessary that the size is 5 μm or less. The reason for this is that if the average particle size is larger than 5 μm, the adhesive layer will become thicker and the heat dissipation of the ceramic wiring board will deteriorate, and the density of the anchor formed by melting and removal will decrease, resulting in lower adhesive strength and reliability. decreases,
Furthermore, the unevenness of the surface of the adhesive layer becomes severe, making it difficult to obtain a fine pattern of the conductor.
Examples of the material of the inorganic fine particles include hydrochloric acid,
Soluble in strong acid solutions such as sulfuric acid, nitric acid, hydrofluoric acid, or mixtures thereof, or strong alkaline solutions such as sodium hydroxide, and has heat resistance, electrical insulation properties, and stability against chemicals other than the above-mentioned strong acids and strong alkalis. For example, silica, titanium oxide, zirconia, zinc oxide, glass, etc. can be suitably used, and in particular, for example, crystalline silica, fused silica, mullite, sillimanite, silica-based glass etc.
Inorganic fine particles mainly containing SiO ₂ are advantageous because they can be easily dissolved in an aqueous hydrofluoric acid solution and have excellent properties.

The blending amount of the inorganic fine particles in the synthetic resin is 10 to 300 parts by weight per 100 parts by weight of the synthetic resin solid content.
A range of parts by weight is preferred, and a range of 50 to 250 parts by weight is particularly preferred since it is possible to obtain conductor adhesion strength of 1.0 Kg/cm or more in terms of peel strength. In order to improve the heat dissipation properties of the adhesive layer, in addition to the inorganic fine particles soluble in the strong acid or strong alkaline solution, fillers having excellent thermal conductivity and electrical insulation properties such as alumina, beryllia, Inorganic fillers such as silicon nitride and boron nitride can be added to the synthetic resin. Incidentally, in order to improve the adhesion between the synthetic resin and the inorganic fine particles, the surface of the inorganic fine particles can be treated with a coupling agent.

As a method for applying the synthetic resin containing inorganic fine particles to the surface of the ceramic substrate, for example, roll coating, dip coating, spray coating, spinner coating, screen printing, etc. can be used. An adhesive layer is formed. The thickness of the adhesive layer (strictly speaking, the thickness after removing the surface portion) is 10 μm or less. The reason for this is that if the thickness of the adhesive layer is greater than 10 μm, heat dissipation, which is a particularly important property for ceramic wiring boards, will be greatly reduced, and if the thermal stress is significant, the adhesive layer will peel off. This is because it becomes easier. Therefore, it is preferable that the thickness of the adhesive layer be as thin as possible within a range that ensures the adhesive strength between the ceramic substrate and the conductor, and a thickness of 5 μm or less is particularly preferable. In order to improve the adhesion between the adhesive layer and the ceramic substrate, the surface of the ceramic substrate can be chemically or physically roughened or treated with a coupling agent.

As a method for removing the surface portion of the adhesive layer, polishing means such as polishing using a fine powder abrasive or liquid honing, for example, etching means using chromic acid, etc. can be adopted, and by doing so, the surface portion of the adhesive layer can be removed by A part of the coated inorganic fine particles can be exposed on the surface of the adhesive layer. Next, the exposed inorganic fine particles can be dissolved and removed by immersing the ceramic substrate in the strong acid or strong alkali solution, or by spraying the solution onto the ceramic substrate. As a result, the surface of the adhesive layer can be uniformly roughened.

According to the present invention, electroless plating is applied to a ceramic substrate on which the surface of the adhesive layer has been roughened. The conductor formed by electroless plating thus obtained has low sheet resistance, low high frequency transmission loss, and excellent fine line properties. Examples of the electroless plating include electroless copper plating, electroless nickel plating, and electroless gold plating. Note that electroless plating can be followed by electroplating or coating with solder.

Incidentally, a conductor circuit can be formed on the ceramic substrate obtained by the present invention, on which the surface of the adhesive layer is roughened, by a subtractive method or an additive method, which is conventionally used for printed wiring boards.

Next, the present invention will be explained with reference to examples.

Example 1 A ceramic wiring board was manufactured through the following steps (1) to (5).

(1) 96% alumina ceramic substrate (external dimensions 50.8
× 50.8 mm, thickness 0.635 mm) was immersed in a 2% solution of silane coupling agent (Shin-Etsu Chemical, KBM-303) dissolved in methyl ethyl ketone, then dried to surface the ceramic substrate. was subjected to coupling processing.

(2) Heat-resistant epoxy resin (Mitsui Petrochemical, TA-
1850) For 100 parts by weight of solid content, fused silica fine particles (manufactured by Takimori, Fuse Rex-X) with an average particle diameter of 1.5 μm that had been treated with silane coupling were added.
They were mixed at a ratio of 150 parts by weight, the viscosity was adjusted to 200 CPS using a butyl carbitol solvent, and then kneaded using a three-roll mill. The obtained varnish-like synthetic resin was applied to one side of the ceramic substrate using a roll coater, and then heated and cured at 180°C for 1 hour to form a 5μ thick layer as shown in Figure 1B.
An adhesive layer of m was formed.

(3) The surface of the adhesive layer was lightly polished with a rotary brush polisher using #1000 alumina fine powder abrasive to expose the fused silica particles on the surface of the adhesive layer as shown in FIG. 1C. The thickness of the adhesive layer after polishing was 3 to 4 μm.

(4) The polished ceramic substrate was immersed in a 25% hydrofluoric acid aqueous solution for 2 minutes to roughen the surface of the adhesive layer as shown in FIG. 1D, and then washed with water.

(5) After masking one side of the ceramic substrate on which the adhesive layer is not formed, a palladium catalyst (manufactured by SHIPLEY, Cataposi 44) is applied to activate the surface of the adhesive layer, and the additive method has the composition shown below. Immerse it in electroless copper plating solution for 3 hours to make the plating thickness 7μ as shown in Figure 1E.
Electroless copper plating was applied.

Copper sulfate (CuSO ₄ 5H ₂ O) 0.06 mol / Formalin (37%) 0.3 mol / Caustic soda (NaOH) 0.35 mol / EDTA 0.12 mol / Additives a little Plating temperature: 70-72℃ PH: 12.4 As above The manufactured ceramic wiring board was electroplated in a copper sulfate plating bath to make the copper plating thickness 35 μm, and the peel strength was measured according to JIS-C6481, and it was 1.4 to 1.8 kg/
cm and adhesive strength is high and stable, and even 150 cm
Even after a 500-hour high-temperature storage test at ℃, no significant decrease in adhesive strength was observed, indicating excellent heat resistance. Also,
When a power transistor (2SC2233) was mounted and the heat dissipation property was examined, it was found to be 1.12°C/W, which was found to be extremely excellent in heat dissipation property.

Example 2 Same as Example 1, but the thickness of the adhesive layer was reduced to approx.
A ceramic wiring board was created by changing the thickness to 50 μm. The heat dissipation property of the obtained substrate was examined in the same manner as in Example 1, and was found to be 2.37° C./W, which was slightly inferior to that of Example 1.

Example 3 As a ceramic substrate, 0.5mmφ was placed at the specified location.
A double-sided through-hole ceramic wiring board as shown in Figure 2 was fabricated using the same process as in Example 1 using a 96% alumina ceramic substrate (external dimensions 50.8 x 50.8 mm, thickness 0.635 mm) with holes arranged in it. Created.

The ceramic wiring board thus obtained was almost the same as the ceramic wiring board obtained in Example 1, and had excellent adhesion reliability and heat resistance between the ceramic board and electroless copper plating. Furthermore, with regard to the connection reliability of the through-holes, no failures occurred after 200 cycles in a thermal shock test (MIL-STD-202E 107D, Cond.B), demonstrating high reliability.

〔Effect of the invention〕

As described above, according to the method of manufacturing a ceramic wiring board of the present invention, it is possible to form a conductor by electroless plating that has extremely excellent adhesion reliability and heat resistance between the ceramic substrate and electroless plating, and It also has excellent heat dissipation, which is an important property for ceramic wiring boards. Furthermore, since the conductor is formed by electroless plating, the ceramic wiring board of the present invention has advantages such as low sheet resistance of the conductor, low high frequency transmission loss, and excellent fine line properties, and is suitable for applications such as hybrid IC. It is extremely useful industrially.

[Brief explanation of drawings]

Figure 1A is a vertical cross-sectional view of the ceramic substrate, Figure 1B
Figure C is a vertical cross-sectional view of the ceramic substrate on which the adhesive layer is formed, Figure C is a vertical cross-sectional view of the ceramic substrate in which the surface inorganic particles of the adhesive layer shown in Figure B are exposed, and Figure D is a vertical cross-sectional view of the ceramic substrate on which the adhesive layer is exposed. A vertical cross-sectional view of a ceramic substrate showing a roughened surface; Figure E is a vertical cross-sectional view of a ceramic wiring board that has been electrolessly plated; Figure 2 is a vertical cross-sectional view of a double-sided through-hole ceramic wiring board. It is a diagram. 1... Ceramic substrate, 2... Adhesive layer, 3...
Electroless plating, 4...Through hole.

Claims (1)

[Scope of Claims] 1. A synthetic resin containing inorganic fine particles is applied to the surface of a ceramic substrate to form an adhesive layer, and the surface of the adhesive layer is removed and a portion of the inorganic fine particles are applied to the surface of the adhesive layer. After exposing, the exposed inorganic fine particles are dissolved and removed to roughen the surface of the adhesive layer, and then electroless plating is applied to form a conductive layer. A method for manufacturing a ceramic wiring board, characterized in that the adhesive layer contains SiO ₂ and the thickness of the adhesive layer is 10 μm or less. 2 The electrical resistance of the ceramic substrate is 10 ⁸ Ω-cm
The method according to claim 1, which is the above. 3. The method according to claim 1 or 2, wherein the synthetic resin is a heat-resistant thermosetting resin. 4. Claims 1 to 3, wherein the synthetic resin is at least one selected from epoxy resins, heat-resistant epoxy resins, epoxy-modified polyimide resins, polyimide resins, and triazine resins.
The method described in any of the paragraphs.