JPH0793488B2 - Enameled wiring board manufacturing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing an enamel wiring board for forming a circuit on an enamel substrate by electroless plating.

(Prior Art) Conventionally, the circuit formation on the enamel substrate has used a thick film method in which a metal paste is screen-printed and then baked at a temperature of 500 ° C. or higher.

However, in the thick film method, (i) it is difficult to print in through holes, (ii) it is difficult to make fine patterns,
(Iii) Since firing at high temperature is repeated (three times for double-sided board with through holes), warpage or cracks may occur on the substrate. (Iv) Precious metal paste is used for firing in air. In addition to the high cost, (v) it is difficult to control the nitrogen atmosphere when firing silver paste, etc.
Since it is fired at a high temperature exceeding 900 ° C, it exceeds the heat resistant temperature of the enamel layer or exceeds the transformation point of the metal core (iron α
→ γ transformation point: 910 ° C), so there was a problem that strain was likely to occur.

For such problems, a method of plating the surface of the enamel substrate has been proposed. For example, JP-A-53-5438
In the method disclosed in Japanese Patent Application Laid-Open No. 60-195078, the surface of the enamel substrate is roughened by hydrofluoric acid for the former and sodium hydroxide melt for the latter.

(Problems to be solved by the invention) When hydrofluoric acid or a sodium hydroxide melt is used, the corrosive force is too strong and the crystalline phase and the amorphous phase on the surface of the enamel substrate are dissolved without distinction, resulting in unevenness on the roughened surface. In addition to being difficult to control, a brittle layer is formed near the surface, so that it is difficult to obtain a stable adhesion force because the electroless plating film applied thereafter peels off together with the brittle layer. Also, handling hydrofluoric acid or sodium hydroxide melt is dangerous.

The present invention provides a method for producing an enameled wiring board having excellent adhesion to an electroless plated film.

(Means for Solving the Problems) The present invention uses an enamel substrate in which a metal core is coated with a crystallization glaze enamel layer composed of a crystalline phase and an amorphous phase,
Roughening solution, which has a higher dissolution rate for the amorphous phase than the crystalline phase, roughens the surface to promote adhesion with the plating film, and then starts the electroless plating reaction so as not to destroy this roughened shape. The electroless plating is performed after applying a catalyst capable of forming a plating film having good adhesion on the enamel substrate.

The roughening solution used in the present invention is a neutral or near-neutral aqueous solution, and has different solubilities in phases having different compositions of crystallized glass.

Generally, the water resistance, acid resistance, and alkali resistance of oxides are as follows [Naruse Ministry "Glass Optics" (Sho 33) Kyoritsu Shuppan).

Water resistance: ZrO ₂ ＞ Al ₂ O ₃ ＞ TiO ₂ ＞ ZnO ＞ MgO ＞ PbO ＞ CaO ＞ BaO Acid resistance: ZrO ₂ ＞ Al ₂ O ₃ ＞ ZnO ＞ CaO ＞ TiO ₂ ＞ PbO ＞ MgO ＞ BaO NaOH resistance: ZrO ₂ 》 Al ₂ O ₃ , TiO ₂ , ZnO, CaO resistance to Na ₂ CO ₃ : ZaO ₂ 》 Al ₂ O ₃ , TiO ₂ , ZnO> CaO, BaO, PbO, MgO As crystalline components in crystallized glass When BaO, CaO, MgO, PbO, etc. are used, the crystalline phase is easily dissolved in both strong acid and strong alkali. By performing a treatment that strongly dissolves the amorphous phase in a neutral or near-neutral aqueous solution and leaves the crystalline phase, a roughened surface is formed that increases the adhesion with the plating film to be applied later. You can

Although crystallized glass is composed of a crystalline phase and an amorphous phase, the crystalline phase may be composed of several kinds of phases (compositions). In the present invention, at least one of the crystalline phases is used. Roughening is performed with a roughening liquid having a higher dissolution rate of the amorphous phase. As a result, at least one phase of the crystalline phase remains on the roughened surface, and the roughened surface can be formed so as to increase the adhesion with the plating film to be applied thereafter.

In the present invention, for example, boron, silicon, magnesium,
Barium is added to 15 <B ₂ O ₃ <35, 10 <SiO ₂ <30, 40 <MgO + CaO
Crystallized glaze containing + BaO <65 (mol%) can be used.

This enamel layer consists of a BaO-rich crystalline phase and a borosilicate glassy phase. The crystalline phase is acicular with a length of 20 μm or less and is dispersed innumerably in the amorphous matrix.

Roughening is, for example, sodium fluoride, potassium fluoride,
It can be carried out with an aqueous solution of a fluoride salt such as ammonium fluoride, fluoroboric acid or ammonium tetrafluoroborate. The pH of the roughening solution is 2 to 13, preferably 5 to
It is 10, more preferably 6-9.

As the catalyst capable of initiating the electroless plating reaction, an ordinary catalyst used as a pretreatment for forming a circuit on the surface of the insulating substrate by electroless plating, particularly an alkaline or neutral Pb-based catalyst is preferable. Electroless plating can also be performed in the production of printed wiring with a normal electroless plating solution for forming a circuit on the surface of an insulating substrate.

In order to form a circuit by electroless plating, at least the electroless plating method may be included at the beginning.

That is, a method of forming a plating resist on the substrate and forming a circuit only by electroless plating, electroless plating on the entire surface of the substrate to form a plating resist and electroplating, then removing the plating resist and performing quick etching to form a circuit. Various methods such as a method of forming a circuit, a method of forming a circuit by electroless plating on the entire surface of the substrate and further performing electroplating, and then forming an etching resist, and forming a circuit are used.

Embodiment An explanation will be given with reference to FIG.

An enamel substrate covered with a crystallized glaze enamel layer 1 having a composition (mol%) of B ₂ O ₃ = 20, SiO ₂ = 15, MgO = 55, BaO = 5, SrO = 5 was used. 2 is a metal core (FIG. 1 (a)).
As the roughening liquid, 20 g of potassium fluoride / water solution (pH 7) was used. The enamel board with through holes was immersed in the roughening solution at 80 ° C for 50 minutes, then in a Pb seeding solution containing 1 g of NaOH for 2 minutes, then in an alkaline reduction solution for 1 minute and then dried. (Fig. 1 (b)). After forming a plating resist 3 on this substrate by a screen printing method (FIG. 1 (c)), electroless copper plating using formalin as a reducing agent is performed to form a copper plating circuit both in the through hole and the land. (FIG. 1 (d)).

The adhesion of the circuit thus obtained to the substrate is 1k
It was over g / mm ² .

On the other hand, elemental analysis of the substrate surface by XMA (X-ray microanalyzer) analysis before and after roughening revealed that the abundance ratio of Ba forming a crystalline phase after roughening significantly increased. Also, the surface observation by SEM (scanning electron microscope) revealed that the roughened surface was a stack of spherical particles of 0.5 to 2 μm.

(Effect of the invention) Through holes have been so far (i) the enamel layer peculiar to the enamel substrate is raised in the vicinity of the through holes, and (ii) the through holes of the enamel substrate are often 1 mm or more. Ink could not be sufficiently sucked into the interior, and it was difficult to liberate through-hole printing. On the other hand, in the method of the present invention, a circuit can be formed on both sides of the substrate and inside the through hole at the same time. Further, by adopting a photoresist, fine patterning is possible because fine processing, which is difficult with the thick film method, can be performed. Further, since the expensive precious metal thick film paste is not used, the cost of circuit formation can be significantly reduced.

[Brief description of drawings]

 FIG. 1 is a sectional view for explaining the method of the present invention. 1 ... Crystallized enamel layer 2 ... Metal core 3 ... Resist 4 ... Plating film

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Toshiro Okamura 1500 Ogawa, Shimodate, Ibaraki Shimodate Research Laboratory, Hitachi Chemical Co., Ltd. (56) Reference JP-A-58-157195 (JP, A) JP-A-60 -21829 (JP, A)

Claims (3)

[Claims] 1. A enamel substrate having a metal core coated with a crystallized glaze enamel layer consisting of a crystalline phase and an amorphous phase, wherein (a) a fluoride salt is contained and its pH is from 2 to 13. And a step of roughening the enamel layer with a chemical solution, (b) a step of applying a catalyst capable of initiating an electroless plating reaction, and (c) a step of performing electroless plating. Board manufacturing method. 2. The crystallized glaze enamel layer comprises boron, silicon,
Add magnesium and barium to 15 <B ₂ O ₃ <35, 10 <SiO ₂ <3
The method for producing an enamel wiring board according to claim 1, which is a crystallized glass containing 0, 40 <MgO + CaO + BaO <65 in a ratio (mol%). 3. The enamel wiring board according to claim 1 or 2, wherein the fluoride salt is any one of sodium fluoride, potassium fluoride, fluoroboric acid and ammonium tetrafluoroborate. Manufacturing method.