JPH0661619A - Production of circuit board - Google Patents

Abstract

PURPOSE:To produce board material for electronic appliances at low cost by metallizing a ceramic or glass board having smooth or highly pure surface. CONSTITUTION:When a zinc oxide layer 2 is formed entirely or partially on the surface of a ceramic or glass board 1 and brought into contact 3 with a solution dissolving a salt of catalytic metal for electroless plating, metal ions in the metal salt are taken into the surface or the interior of a semiconductor in parallel with dissolving reaction of the zinc oxide. The phenomenon is utilized 4 in electroless plating bath of copper, nickel, silver, gold, and/or platinum thus depositing a metal layer on the surface of ceramic or glass board.

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 circuit board by forming a metal layer on the entire surface or a part of a ceramic substrate, and in particular, a zinc oxide thin film has strong adhesion to various ceramic or glass substrates. And, while being dissolved in a solution containing a metal that serves as a catalyst for electroless plating, the metal ions in the metal salt are taken into the surface and inside, and when this is put into an electroless plating bath, the adhesion is improved. The present invention relates to one utilizing a novel phenomenon discovered by the present inventor that a metal layer having good conductivity is formed.

[0002]

2. Description of the Related Art Various methods have been tried for manufacturing a circuit board material for electronic devices by forming a metal layer on a ceramic or glass substrate surface with good adhesion. Here, a typical electroless plating is used. Methods and typical methods of physical vapor deposition are introduced.

First, the electroless plating method is used. First, the surface of the ceramic substrate is roughened by various methods, and then the surface of the ceramic substrate is sensitized by treatment in a concentrated hydrochloric acid solution of SnCl ₂ , Is treated with a concentrated hydrochloric acid solution of PdCl _{2, and} the ceramic surface is treated by the following equation (1).
Form Pd metal nuclei that act as a catalyst for electroless plating of gold, copper or nickel.

Sn ²⁺ + Pd ²⁺ → Sn ⁴⁺ + Pd (1) This is placed in an electroless plating bath of gold, copper or nickel to form a metal layer. Moreover, if necessary, the power is further assisted by electrodeposition.

Further, in the physical vapor deposition method, a ceramic substrate is placed in a vacuum container, and the metal is vaporized by a method such as argon sputtering to deposit the metal on the substrate.

Although the electroless plating method is excellent in terms of cost, the electroless plating method has a drawback that the ceramic surface must be roughened to increase the surface area in order to obtain adhesion strength.

Further, for example, in the case of alumina, which is a typical ceramics substrate material, the surface roughening is performed by chemically etching impurities contained in the substrate, so that it has a drawback that it can be used only for a substrate material of low purity. .

For these reasons, there is a limit in obtaining a metal layer pattern having a fine structure by etching a metallized ceramics substrate manufactured by an electroless plating method.

Therefore, in order to metallize a ceramic substrate having a smooth surface and high purity, a physical vapor deposition method is mainly used. For example, in the case of metallizing a glass substrate or a high-purity alumina substrate whose surface is sufficiently polished, chromium, then copper or nickel, etc. are first deposited by a sputtering method. Here, the chromium layer is sandwiched between the ceramic substrate and the copper or nickel layer in order to obtain adhesion strength.

[0010]

As described above, according to the existing technology, it is not possible to inexpensively manufacture a substrate material for electronic equipment by metallizing a ceramic substrate or a glass substrate having a smooth surface or a high purity. It was difficult.

An object of the present invention is to provide a new method which can eliminate such drawbacks.

[0012]

The present invention provides a novel phenomenon discovered by the present inventor, that is, a zinc oxide thin film has strong adhesion to various ceramic or glass substrates, and
While dissolving in a solution containing a metal that serves as a catalyst for electroless plating, the metal ions in the metal salt are taken into the surface and inside, and when this is put into an electroless plating bath, a metal layer with good adhesion is formed. This new phenomenon can be used to form a metal layer on the entire surface or a part of a ceramics or glass substrate to manufacture a circuit board for electronic devices, etc. And has the following configurations.

(1) When a zinc oxide layer is formed on the entire surface or a part of a ceramic or glass substrate and brought into contact with a solution in which a metal salt of a metal serving as a catalyst for electroless plating is dissolved,
Utilizing the phenomenon that metal ions in the metal salt are taken into the surface and the inside of the semiconductor in parallel with the dissolution reaction of zinc oxide, which is used for copper, nickel, silver, gold, and / or
Alternatively, a metal layer is laminated on the surface of the ceramic or glass substrate by placing it in a platinum electroless plating bath.

(2) In the method for manufacturing a circuit board as described in Structure (1), the zinc oxide layer is etched as required, and then a metal layer is deposited to form a patterned metal layer on a ceramic or A structure characterized by being formed on a glass substrate.

[0015]

In the structure (1), the zinc oxide layer is
Having strong adhesion to various ceramics or glass substrates, and while dissolving in a solution containing the metal salt, adsorption of the metal ion or exchange reaction with zinc in zinc oxide occurs, Incorporation of the metal ions occurs on the surface and inside of the zinc oxide layer.

The reaction formula in this case is considered to be the following formula (2) or (3), for example, when palladium chloride is used as the metal salt.

ZnO + PdCl ₂ → Zn ²⁺ ＋ Pd ²⁺ (ad) ＋2 ・ Cl ₂ (ad) ＋1/2 ・ O ₂ (2) ZnO ＋ Pd ²⁺ → Zn ²⁺ ＋ PdO (3) Where (ad) is It means the adsorption state. In both the above formulas (2) and (3), palladium is in a divalent state.

Next, when this substrate is placed in an electroless plating bath, the reducing agent in the plating bath advances the reduction reaction of the metal ions represented by the formula (4) or (5) to deposit a zero-valent metal. .

Pd ²⁺ (ad) + reducing agent → Pd (4) PdO + reducing agent → Pd + 1/2 · O ₂ (5) The metal thus incorporated on the zinc oxide or inside the zinc oxide Acts as a good catalyst for electroless plating. Therefore, according to this method, the metal can be formed on the ceramic substrate with good adhesion.

Further, according to the above configuration (2), a part of the semiconductor layer formed on the ceramic substrate is etched as required, and then electroless plating is performed, whereby
It makes it possible to form the electroless metal layer only on the patterned portion of the required circuit.

[0021]

EXAMPLES A method of manufacturing a ceramics circuit board for electronic devices according to examples of the present invention will be described below.

(First Embodiment) FIG. 1 is a schematic view showing an experimental procedure of a method for manufacturing a ceramics circuit board for electronic equipment according to a first embodiment of the present invention. In the figure, reference numeral 1 is a ceramic substrate (cross-sectional view), reference numeral 2 is a zinc oxide layer, reference numeral 3 is a metal nucleus serving as a catalyst for electroless plating, and reference numeral 4 is an electroless plated copper metal layer.

First, the zinc oxide layer 2 is formed on the ceramic substrate. The zinc oxide layer 2 may be produced by any method as long as it can form a zinc oxide layer on the surface of ceramics. Here, a solution containing zinc ions is sprayed, and then in air. Alternatively, a spray pyrolysis method of spraying on a substrate heated in an oxygen atmosphere was used.

Next, this ceramic substrate is put into a solution containing the metal salt to adsorb metal ions on the surface and inside of the zinc oxide 2.

Next, this ceramic substrate is placed in a copper electroless plating bath to deposit a metal layer 4.

When the ceramic substrate is treated by such a method, the entire surface of the ceramic substrate can be uniformly covered with copper with good adhesion.

The experimental conditions in this case are as follows.

Ceramics substrate High-purity alumina substrate (purity: 99.9%, surface roughness: R
_a = 0.05 μm) Zinc oxide thin film 0.4 μm thickness Zinc oxide thin film manufacturing method Spray coating method Spray solution: 0.05 M zinc acetate ethanol solution Substrate temperature: 400 ° C. Composition of metal salt solution 10 ⁻³ MPdCl ₂ aqueous solution (PH = 2.45) Electroless plating solution Type A: Ebara Eugelite PB-503 Type B: Ebara Eugelite PB-542 Preparation procedure 1. Substrate cleaning: The alumina substrate was ultrasonically cleaned in ethanol for 5 minutes and then air-dried.

2. Preparation of zinc oxide thin film: The alumina substrate obtained by the preparation procedure 1 was placed on a hot plate heated to 400 ° C., and 200 ml of a 0.05 M zinc acetate ethanol solution was sprayed from above. Then 400 in the air
Annealing treatment was performed at ° C for 3 hours.

3. Preparation of catalytic metal nuclei: The alumina substrate obtained by the preparation procedure 2 was immersed in the metal salt aqueous solution for about 5 minutes.

4. Preparation of copper metal layer: The alumina substrate obtained by the preparation procedure 3 is thinned with the electroless copper plating solution A,
Further, using the electroless copper plating solution B, the film thickness is about 3 μm.
Electroless plating was performed until it became.

The adhesion strength of the copper film obtained in this experiment was measured by patterning the copper film with a photoresist into a square section of 2 × 2 mm, soldering lead wires thereon, and then measuring the vertical tensile strength. It was measured. As a result of measuring 16 points on a 5 × 5 cm substrate, the maximum value is 18.85 k.
g, the minimum value was 9.28 kg, and the average value was 13.59 kg. It can be seen that the interface separated by the peeling test is always the copper / zinc oxide interface, and the zinc oxide thin film / alumina interface has stronger adhesion.

Further, an electronic circuit pattern having a fine structure with a line width of 10 μm was formed from the copper-clad ceramic substrate obtained in this experiment by patterning using a normal photoresist, followed by copper etching and zinc oxide etching. I was able to get A cross-sectional view of the patterned metal layer on the ceramic substrate manufactured in this way is shown in FIG. In the figure, reference numeral 21 is a ceramic substrate (cross-sectional view), reference numeral 22 is a zinc oxide layer, reference numeral 23 is an electroless plating catalyst nucleus, and reference numeral 24 is an electroless plating copper metal layer.

(Second Embodiment) The electroless plating bath of copper used in the first embodiment is replaced by an electroless plating bath of nickel, and otherwise the same as in the first embodiment, metallizing the ceramic substrate. I went.

The experimental conditions in this case are as follows.

Ceramics substrate High-purity alumina substrate (purity: 99.9%, surface roughness: R
_a = 0.05 μm) Zinc oxide thin film 0.4 μm thickness Zinc oxide thin film manufacturing method Spray coating method Spray solution: 0.05 M zinc acetate ethanol solution Substrate temperature: 400 ° C. Composition of metal salt solution 10 ⁻³ MPdCl ₂ aqueous solution (PH = 2.45) Electroless plating solution Chemical Products Kogyo Nicka727 Manufacturing procedure 1. Substrate cleaning: The alumina substrate was ultrasonically cleaned in ethanol for 5 minutes and then air-dried.

2. Preparation of Zinc Oxide Thin Film: The alumina substrate obtained in Preparation Procedure 1 was placed on a hot plate heated to 400 ° C., and 200 ml of 0.05 M zinc acetate ethanol solution was sprayed from above. After that, an annealing treatment was performed in air at 400 ° C. for 3 hours.

3. Preparation of catalytic metal nuclei: The alumina substrate obtained by the preparation procedure 2 was immersed in the metal salt aqueous solution for about 5 minutes.

4. Preparation of Copper Metal Layer: The alumina substrate obtained in Preparation Procedure 3 was electroless plated using the electroless nickel plating solution until the film thickness became about 3 μm.

(Third Example) The high-purity alumina substrate used in the first example was replaced with an aluminum nitride substrate, and the aluminum nitride substrate was metallized in the same manner as in the first example.

The experimental conditions in this case are as follows.

Aluminum nitride substrate Purity: 99% Surface roughness: Ra = 0.5 μm Zinc oxide thin film thickness 0.4 μm Zinc oxide thin film preparation method Spray coating method Spray solution: 0.05M zinc acetate ethanol solution Substrate temperature: 300 ° C Composition of metal salt solution 10 ^-3 MPdCl ₂ aqueous solution (pH = 2.45) Electroless plating solution Type A: Ebara Eugelite PB-503 Type B: Ebara Eugelite PB-542 Preparation procedure 1. Substrate cleaning: The aluminum nitride substrate was ultrasonically cleaned in ethanol for 5 minutes and then air-dried.

2. Preparation of zinc oxide thin film: The aluminum nitride substrate obtained in Preparation Procedure 1 was placed on a hot plate heated to 300 ° C., and 200 ml of a 0.05 M zinc acetate ethanol solution was sprayed from above.

3. Preparation of catalytic metal nuclei: The aluminum nitride substrate obtained in Preparation Procedure 2 was immersed in the metal salt aqueous solution for about 5 minutes.

4. Preparation of copper metal layer: The aluminum nitride substrate obtained by the preparation procedure 3 is thinned with the electroless copper plating solution A, and further the electroless copper plating solution B is used to obtain a film thickness of about 3
Electroless plating was performed until the thickness became μm.

The adhesion strength of the copper film obtained by this experiment was measured by patterning the copper film with a photoresist into a square section of 2 × 2 mm, soldering a lead wire thereon, and then measuring the vertical tensile strength. It was measured. As a result of measuring 16 points on a 5 × 5 cm substrate, the maximum value is 13.79 k.
g, the minimum value was 7.13 kg, and the average value was 10.00 kg. It can be seen that the interface separated by the peeling test is always the copper / zinc oxide interface, and the zinc oxide thin film / aluminum nitride interface has stronger adhesion.

(Fourth Embodiment) The glass substrate was metallized in the same manner as in the first embodiment except that various glass substrates were used as the high-purity alumina substrate used in the first embodiment.

The experimental conditions in this case are as follows.

Glass substrate Type A: Pyrex glass (Corning 7104) Type B: Cellstar glass (manufactured by Asahi Glass Co., Ltd.) Type C: Soda glass Zinc oxide thin film 0.8 μm Zinc oxide thin film preparation method Spray coating method Spray solution: 0.05M zinc acetate ethanol solution Substrate temperature: 300 ° C Composition of metal salt solution 10 ^-3 MPdCl ₂ aqueous solution (pH = 2.45) Electroless plating solution Type A: Ebara Eugelite PB-503 Type B: Ebara Eugelite PB-542 manufacturing procedure 1. Substrate cleaning: A glass substrate was ultrasonically cleaned in ethanol for 5 minutes and then air-dried.

2. Preparation of zinc oxide thin film: The glass substrate obtained by the preparation procedure 1 was heated to 300 ° C. and placed on a hot plate, and 200 ml of 0.05 M zinc acetate ethanol solution was sprayed from above.

3. Preparation of catalytic metal nuclei: The aluminum nitride substrate obtained by the preparation procedure 2 was immersed in the metal salt aqueous solution for about 4 minutes.

4. Preparation of copper metal layer: The glass substrate obtained by the preparation procedure 3 is thinned with the electroless copper plating solution A, and further electroless plated with the electroless copper plating solution B until the film thickness becomes about 3 μm. went.

The adhesion strength of the copper film obtained in this experiment was measured by patterning the copper film with a photoresist in a square section of 2 × 2 mm, soldering lead wires thereon, and then measuring the vertical tensile strength. It was measured. 5 for each type A, type B, and type C glass substrate
As a result of performing the measurement at each point, the maximum value is 5.25 kg in Type A, the average value is 3.28, the maximum value is 5.87 kg in Type B, the average value is 4.62 kg, and the maximum value is 10 kg in Type C. It was .29. In addition,
In any type of glass substrate, the substrate itself was often broken. The interface separated by the peeling test is always the copper / zinc oxide interface, and the zinc oxide thin film /
It can be seen that the glass interface has stronger adhesion.

(Fifth Embodiment) FIG. 3 is a schematic view showing an experimental procedure of a method for manufacturing a ceramics circuit board for electronic equipment according to a fifth embodiment of the present invention. In the figure, reference numeral 31 is a ceramic substrate (cross-sectional view), reference numeral 32 is a zinc oxide layer,
Reference numeral 33 is an electroless plating catalyst nucleus, and reference numeral 34 is an electroless plating copper metal layer.

In this embodiment, the first embodiment, the third embodiment,
In the fourth embodiment, the zinc oxide thin film formed on the substrate is patterned by various methods, and then electroless plating is performed to directly obtain a patterned metal layer in a desired electronic circuit. it can.

As a method for patterning a zinc oxide thin film, a method utilizing a photodissolution reaction of zinc oxide in an aqueous solution,
Anything will do. Here, a photo-etching method using a resist is adopted.

The experimental conditions in this case are as follows.

Substrate Soda glass Zinc oxide thin film 0.8 μm Zinc oxide thin film preparation method Spray coating method Spray solution: 0.05 M Zinc acetate ethanol solution Substrate temperature: 400 ° C. Photoresist Tokyo Ohka etching solution Hydrochloric acid aqueous solution (pH = 1.0) Resist stripping solution Composition of Tokyo Ohka metal salt solution 10 ^-3 MPdCl ₂ aqueous solution (pH = 2.45) Electroless plating solution Type A: Ebara Eugelite PB-503 Type B: Ebara Eugelite PB-542 Procedure 1. Substrate cleaning: A glass substrate was ultrasonically cleaned in ethanol for 5 minutes and then air-dried.

2. Preparation of Zinc Oxide Thin Film: The glass substrate obtained in Preparation Procedure 1 was placed on a hot plate heated to 400 ° C., and 200 ml of a 0.05 M zinc acetate ethanol solution was sprayed from above.

3. Patterning of semiconductor thin film: Fabrication procedure 2
On the glass substrate obtained by applying the photoresist,
After further irradiating with light through a pattern mask, it was placed in the etching liquid for 40 seconds, and the cured resist was peeled off with the peeling liquid.

4. Preparation of catalytic metal nuclei: The glass substrate obtained by the preparation procedure 3 was immersed in the metal salt aqueous solution for about 5 minutes.

5. Preparation of copper metal layer: The glass substrate obtained by the preparation procedure 4 is thinned with the electroless copper plating solution A, and further electroless plated with the electroless copper plating solution B until the film thickness becomes about 3 μm. went.

By this experiment, a fine metallic copper pattern having a line width of 30 μm was obtained on soda glass. , On the copper film,
An adhesion test was carried out by adhering Scotch tape No. 56 well and peeling it off, but it was found that there was no metallic copper left on the tape and the adhesion was high.

[0064]

As described above in detail, the present invention provides a novel phenomenon discovered by the present inventor, that is, a zinc oxide thin film formed on various ceramics has strong adhesion to a substrate, Further, when contacted with an acidic aqueous solution in which a metal salt containing a metal serving as a catalyst for electroless plating is contacted, metal ions in the metal salt are generated in parallel with the dissolution reaction of the zinc oxide layer, In addition, by utilizing the phenomenon of being taken in with good dispersibility inside, it is possible to form a metal layer with good adhesion on the whole surface or a part of various ceramics to make it an electronic circuit board material.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an implementation procedure of a method for manufacturing a circuit board for an electronic device according to a first embodiment of the present invention.

FIG. 2 is a schematic view showing a cross section of a circuit board for electronic equipment manufactured according to the first embodiment of the present invention.

FIG. 3 is a schematic diagram showing an experimental procedure of a method for manufacturing a ceramics circuit board for electronic devices according to a fifth embodiment of the present invention.

[Explanation of symbols]

1, 21, 31 ... Ceramics substrate, 2, 22, 32 ...
・ Zinc oxide layer, 3, 23, 33 ... Electroless plating catalyst nucleus,
4, 24, 34 ... Electroless plated copper layer.

Claims (2)

[Claims] 1. When a zinc oxide layer is formed on the entire surface or a part of a ceramic or glass substrate and brought into contact with a solution in which a metal salt of a metal serving as a catalyst for electroless plating is brought into contact, the dissolution reaction of zinc oxide is carried out in parallel. Then, by utilizing the phenomenon that the metal ions in the metal salt are taken into the surface and inside of the semiconductor, it is put in an electroless plating bath of copper, nickel, silver, gold, and / or platinum. A method for manufacturing a circuit board, comprising laminating a metal layer on the surface of a ceramics or glass substrate according to. 2. The method for manufacturing a circuit board according to claim 1, wherein the zinc oxide layer is optionally etched, and then a metal layer is deposited to form a patterned metal layer on a ceramic substrate. A method for manufacturing a circuit board, which comprises forming the circuit board.