JPH0654828B2 - Method of forming circuit on hollow substrate - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for forming a circuit conductor on an enamel substrate by electroless plating, and particularly, to improve the adhesion strength of a conductor metal to the enamel substrate surface. The present invention relates to a circuit forming method that can be performed.

“Prior Art” As is well known, a metal core wiring board using an enamel is
It has been put to practical use in recent years, and its use is gradually increasing. In particular, a substrate using a crystallized enamel glass as disclosed in JP-A-57-140877 is widely used because it has high heat resistance and good dimensional accuracy. It is starting to be used. Conventionally, as a method of forming a circuit on such an enamel substrate, screen printing is performed on the substrate using a thick film conductor paste, and then firing is performed, and a pattern made of a metal such as Au, Ag, or Cu is formed on the substrate. There were most ways to create.

“Problems to be solved by the invention” In the conductor paste used for circuit formation by the thick film technology as described above, in order to form a circuit by firing in air, oxidation resistant Au, Ag, etc. Use precious metal or N ₂
Cu is used in the gas. However, noble metals such as Au and Ag are expensive, and Cu firing in N ₂ gas has problems such as man-hours and costs as compared with firing in air. Further, since the thick film conductor paste contains oxide, glass, etc. as a binder component, it is not easy to reduce the impedance of the formed circuit. Furthermore, in the method of screen-printing the thick film conductor paste, the fine line property is not so good,
There is a problem that it is difficult to form a thin conductor wiring.

On the other hand, if the circuit conductor is formed by electroless plating, the finding that it is possible to solve the above problems and form a circuit with low cost, low resistance and high accuracy is
It was generally known, but it was not put to practical use. The cause was that the adhesion strength of the conductor coating by electroless plating on the surface of the enamel vitreous material was weak. This is because the surface of glassy substrates such as enamel is usually very smooth, so even if direct electroless plating is performed, the ability to mechanically hold the plated metal film is small,
Further, it is difficult to sufficiently activate the place where the seed metal nuclei necessary for electroless plating are applied to the surface.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a circuit forming method by electroless plating with high adhesive strength to a enamel substrate.

"Means for Solving Problems" A circuit forming method according to the present invention is a circuit conductor formed on a substrate by roughening the surface of a enamel substrate using a chromic acid-sulfuric acid mixture solution. The gist is to achieve high adhesive strength. More specifically, prior to the formation of the circuit conductor by electroless plating, the surface of the enamel substrate is 5-40 wt% CrO ₃ , 5-20 wt% H ₂ SO
_4, chromic acid and the balance water - about 1-2 sulfuric acid mixed aqueous solution
It is immersed for 0 minutes to roughen the surface of the enamel board by etching, and then the circuit conductor is formed.

[Operation] According to the above method, the glass on the surface of the enamel substrate is partially melted, and a large number of fine irregularities of several μm are formed. As a result, the circuit conductor formed on this surface thereafter with respect to the substrate surface. The adhesive strength is remarkably improved.

That is, chromate ions adhere to the irregularities of the enamel substrate, and the surface activity of the enamel substrate increases due to the oxidizing action of the chromate ions. Since the surface of the enamel board is further activated and then the circuit conductor is formed by electroless plating, the adhesive strength of the circuit conductor is increased.

The degree of unevenness due to the above etching is, for example, CrO ₃ ; 40
When an aqueous solution containing 0 g / 10% by weight of H ₂ SO ₄ is used as an etching solution, the surface is roughened in about 5 minutes, and even if it is further immersed and the glass is melted, the degree of unevenness is reduced. Since it does not change so much, about 5 minutes is sufficient.

In the present invention, after roughening the surface as described above, the substrate is thoroughly washed with water to remove the acid content. Then, the roughened surface of the enamel substrate is activated, and a nucleus to be a seed for deposition of electroless plating is added. This activation treatment is usually performed after sensitizing the surface of the base material with a Sn compound solution, and is performed with an aqueous palladium compound solution. SnCl ₂ ; Immersed in an aqueous solution of about 0.2 g / for about 10 minutes, washed with water, and then immersed in an aqueous solution of PdCl ₂ ; about 0.5 g / for about 10 minutes for activation, which gives good nucleation. You can In particular, the activation process with this PdCl ₂ aqueous solution is
If this is repeated twice or more, the amount of Pd present on the substrate surface increases, and it becomes easy to form a good plating film. Alternatively, good activation can be achieved with a solution of AgNO ₃ ; about 1 g /, PdCl ₂ ; about 0.5 g /.

The substrate activated as described above is lightly washed with water to remove the activated solution adhering thereto, and then immersed in an electroless plating solution to form a circuit conductor. The electroless plating solution used for forming the circuit conductor may be any solution that can deposit a dense metal film. In particular, CuSO ₄ ; 4-35 g /
, 20 to 150 g /, NaOH; 5 to 50 g /, HCHO; 5 to 200 mg /, balance: electroless copper plating using a liquid having a water composition, NiSO ₄ ; 0.05 to 0.2 mol /, NaH ₂ PO ₂ ; 0.05 to 0.4 mol _{/, Na 3 C 6 H 5} O 7; 0.0
5 to 0.2 mol /, balance: Electroless nickel plating using a liquid having a composition of water can give a good conductor film.

Among the above liquid compositions, particularly preferable is CuSO ₄ ; 10 g / 50 g /, HCHO; 15 ml /, balance: Cu plating with aqueous solution of water, or NiSO ₄ ; 0.1
Ni plating with an aqueous solution of ml / (5), NaH ₂ PO ₂ ; 0.2 mol /, Na ₂ C ₆ H ₅ O ₇ ; 0.1 mol /.

The above-mentioned formation of the conductor by electroless plating may be performed only on the circuit formation portion by masking the portion other than the circuit pattern, or by forming the conductor film on the entire surface of the substrate and plating the portion other than the circuit pattern. The circuit may be formed by removing the metal by etching. The conductor circuit created by the above process has sufficient adhesive strength (usually 2.
5 kg / 2 mm x 2 mm is enough).

Next, an embodiment of the present invention will be described.

"Example 1"MgO; 58.0 mol%, BaO; 7.0 mol%, B ₂ O _3; 21.0 mol%, SiO _2; the enamel substrate prepared using a crystallized glass having a composition of 14.0 mol% of the following steps 2mm × 2 by electroless copper plating on the substrate surface after treatment
A copper conductor pattern of mm was formed.

1) Alcohol cleaning, 2) Etching CrO ₃ ; 400 g /, H ₂ SO ₄ ; 10% aqueous solution,
Immerse at room temperature for 5 minutes.

3) Washing with water 4) Sensitization SnCl ₂ ; 0.2 g / aqueous solution, soaking for 10 minutes.

5) Washing with water 6) Activated PdCl ₂ ; 0.5 g / water solution, soaking for 10 minutes.

7) Washing with water 8) Electroless copper plating, CuSO ₄ ; 10g /, 50g / l ・ NaOH; 24g /, ・ HCHO; 15ml /, soak for 60 minutes.

9) Washing with water 10) Drying 11) Masking for forming a 2mm x 2mm conductor pattern 12) Etching of conductors other than the pattern part; Ferric chloride 5
% Aqueous solution.

13) Washing with water 14) Drying and removal of masking Solder a 0.8mm diameter tin-plated annealed copper wire to each conductor pattern of 2mm x 2mm created by the above procedure, pull it in the direction perpendicular to the board surface, and push-pull scale. The load for peeling the conductor pad was measured by. 60 pieces of 2mmm
The adhesive strength of the square pad was measured, and as a result,
An average value of about 4.9 kg / 2 mm x 2 mm was obtained.

[Example 2] The same enamel substrate as in Example 1 was used, and after this substrate was washed with alcohol, masking was applied to portions other than the place where a conductor pattern of 2 mm x 2 mm was to be formed. The plating solution is NiSO ₄ ; 0.1 m /, NaH ₂ PO ₂ ; 0.2 mol /, N
a ₂ C ₆ H ₅ O ₇ ; Processed according to steps 2) to 9) of Example 1 except that 0.1 mol / aqueous solution was used. After that, the masking agent was removed, and then the adhesive strength was measured in the same manner as in Example 1. As a result, the average strength is about 3.8Kg / 2mm × 2mm
The value of was obtained.

As described above, the circuit forming method according to the present invention is
The gist of the invention is to achieve a high adhesive strength of a circuit conductor formed on a substrate by roughening the surface of a enamel substrate using a chromic acid-sulfuric acid mixture solution. More specifically, prior to the formation of the circuit conductor by electroless plating, the surface of the enamel board is 5-40 wt% CrO ₃ ,
The surface of the enamel board was roughened by etching by immersing it in a chromic acid-sulfuric acid mixed aqueous solution containing 5 to 20% by weight of H ₂ SO ₄ and the balance of water for about 1 to 20 minutes.
According to the present invention, the surface of the enamel substrate is roughened with a chromic acid-sulfuric acid mixture solution, so that the glass on the surface of the enamel substrate is partially dissolved, and many fine irregularities of several μm are formed. Chromate ions are attached to the irregularities of. The surface activity of the enamel substrate increases due to the oxidizing action of this chromate ion. Since the surface of the enamel board is further activated and then the circuit conductor is formed by electroless plating, the adhesion strength of the circuit conductor to the enamel board can be improved.

Therefore, according to the present invention, the glass on the surface of the enamel substrate can be partially melted, and a large number of fine irregularities of several μm can be formed on this surface, and as a result, a circuit formed on the surface of the substrate thereafter. The adhesive strength of the conductor to the substrate surface can be remarkably improved.

Claims (5)

[Claims] 1. A method for roughening the surface of a enamel substrate with a CrO ₃ —H ₂ SO ₄ aqueous solution, activating the surface of the substrate, and then forming a circuit conductor on the surface of the substrate by electroless plating. A method for forming a circuit on a enamel substrate. 2. The enamel glass of the enamel substrate is about 6 to 6.
Claims: 25 mol% barium oxide, about 30-60 mol% magnesium oxide, about 13-35 mol% boron trioxide, and about 10-25 mol% silicon dioxide. 2. A method for forming a circuit on a enamel substrate according to item 1 of the above. 3. Cr used for roughening the surface of a enamel substrate
The O ₃ —H ₂ SO ₄ aqueous solution is an aqueous solution of CrO ₃ ; 5 to 40% by weight, H ₂ SO ₄ ; 5 to 20% by weight, and the balance is an aqueous solution of water. A method for forming a circuit on the enamel substrate described above. 4. The electroless plating solution is CuSO ₄ ; 4-35.
g /, 20-150 g /, NaOH; 5-50 g /, HCHO; 5-200 ml
The method for forming a circuit on a enamel substrate according to claim 1, which is an aqueous solution of /. 5. The electroless plating solution is NiSO ₄ ; 0.05.
0.2 mol _{/, NaH} 2 PO 2; _0.05~0.4
Mol _{/, Na 3 C 6 H 5} O 7; 0.05~0.2 circuit forming method onto enameled substrate to in paragraph 1 of the claims, characterized in that the mole / of the aqueous solution.