JPH11256349A - Plating method with high adhesion property on resin base and copper plating liquid to be used for that - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a means to easily obtain a high and stable adhesion strength between a resin base body and a conductive layer. SOLUTION: In the plating method with high adhesiveness to a resin base, a resin substrate subjected to catalytic treatment is subjected to electroless copper plating with the plating precipitation rate controlled to <=0.5 μm/30 min, and then subjected to electroplating. As for examples of the electroless copper plating bath used for this method, the following plating liquids can be used. The electroless copper plating liquid contains copper ion, complexing agent of copper ion, formaldehyde or glyoxalic acid as a reducing agent, and a precipitation controlling agent, and has 12 to 13 pH range. Or the electroless copper plating liquid contains copper ion, citric acid or its salt as a complexing agent of copper ion, and a hypophosphorus acid or its salt as a reducing agent, and has 8.0 to 11.0 pH range.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-adhesion plating method capable of forming a metal film having good adhesion on a resin substrate, and an electroless copper plating solution usable for this purpose.

[0002]

2. Description of the Related Art In recent years, with the tendency of electronic equipment to become smaller, lighter, thinner, faster, and more sophisticated, there is an increasing demand for thinner printed wiring boards, multilayers and higher densities. At present, attention has been paid to the build-up method in order to respond to such a demand, and an insulating layer and a conductor layer are stacked for each layer, and the layers are connected each time to manufacture a multilayer wiring board. Also,
There are various element technologies such as interlayer insulating materials, formation of via holes, formation of fine patterns, etc. in manufacturing multilayer wiring boards. Among them, the interlayer insulating material has good adhesion between the insulating layer and the conductor layer. Very important.

In general, in a printed wiring board, a conductor layer on a resin substrate is often formed by sequentially performing electroless plating and electroplating. For example, a method for forming a metal copper layer (conductor layer) is often used. Is generally performed in the order of roughening the surface of the resin substrate, applying a palladium catalyst, electroless copper plating, and electrolytic copper plating. And, the adhesion between the resin substrate and the copper plating layer depends on the effect of the electroless copper plating penetrating into the fine recesses on the resin substrate caused by the roughening, the so-called anchor effect. Have been.

As described above, at present, in order to improve the adhesiveness, the surface of the insulating layer is roughened with an oxidizing agent to obtain an anchor effect, thereby improving the adhesive strength. It is difficult to obtain, and it is one of the bottlenecks in manufacturing printed wiring boards.

[0005]

Therefore, there has been a strong demand for the development of means that can easily and stably obtain a high adhesion strength between a resin substrate and a conductive layer.

[0006]

The inventor of the present invention has conducted various studies on factors relating to the adhesion between the resin base material and the conductor layer in the printed wiring board. It was found that the pore size and the deposition rate of electroless copper plating on copper had a great influence on the adhesion.

That is, the fine concave hole is too small, and
If the deposition rate of electroless copper plating on copper is too high, bridge-like deposition occurs, and the film is formed without plating inside the fine concave holes formed on the resin surface, so sufficient adhesion I knew I couldn't get it. On the other hand, if this is avoided and the resin base material is roughened slightly to improve the coverage of the electroless copper plating, the anchor effect is naturally lost.

The inventor of the present invention has conducted further studies in order to resolve this contradiction. As a result, in electroless copper plating, no metal was first deposited on metal copper deposited on a palladium catalyst first, and the remaining palladium catalyst was not deposited. It has been conceived that if an electroless copper plating solution that selectively precipitates is used, the electroless copper will adhere to the inside of the fine concave hole and a sufficient anchor effect will be obtained. Then, as a result of various studies on the composition and the components of the electroless copper plating solution, they found one that meets such a purpose, and completed the present invention.

[0009] That is, an object of the present invention is to reduce the rate of plating deposition on copper by 0.5 on a resin substrate that has been catalyzed.
An object of the present invention is to provide a method for plating a resin substrate on which electroless copper plating is performed at a rate of not more than μm / 30 minutes or less, followed by electroplating.

Another object of the present invention is to contain copper ion, a complexing agent of copper ion, formaldehyde or glyoxylic acid as a reducing agent, and a precipitation controlling agent, which are used in the above method, and have a pH in the range of 12 to 13. An electroless copper plating solution is provided.

Further, another object of the present invention is to contain copper ions used in the above-mentioned method, citric acid or a salt thereof as a complexing agent for copper ions and hypophosphorous acid or a salt thereof as a reducing agent, and have a pH of 8. An object of the present invention is to provide an electroless copper plating solution having a range of 0 to 11.0.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, electroless copper plating does not further deposit on a copper plating film deposited on a palladium catalyst and deposits at a normal rate on a palladium catalyst on which copper has not yet deposited. It is important to adjust to

For this purpose, it is necessary to control the deposition rate of electroless copper plating on copper to 0.5 μm / 30 minutes or less.

Any electroless copper plating that satisfies the above conditions can be used in the present invention irrespective of the bath composition and the like. One example of such an electroless copper plating solution is copper electroless plating. An electroless copper plating solution containing formaldehyde or glyoxylic acid and a precipitation controlling agent as a complexing agent and a reducing agent for ions and copper ions and having a pH in the range of 12 to 13 is exemplified.

The precipitation control agent added to the electroless copper plating solution suppresses the deposition of electroless copper plating on copper. Specifically, thiourea, allylthiourea, thiomalic acid, thiomalic acid, Glycolic acid or thiocyanic acid or salts thereof may be mentioned. Among them, the effects of thiourea, allylthiourea, thiomalic acid or salts thereof are the most excellent. This precipitation inhibitor is generally used in an amount of 0.1.
About 1 to 1000 ppm is blended.

On the other hand, in the above electroless plating solution, copper sulfate, cupric chloride, copper nitrate and the like are used as copper ion sources, and EDTA, tartaric acid, malic acid and the like are used as copper ion complexing agents.
Citric acid, quadrol, glycine and the like and salts thereof. These are all commonly used in electroless copper plating baths using formaldehyde as a reducing agent. The amounts of these components may be the same as those of a conventional electroless copper plating bath using formaldehyde.

The rate of deposition of the above electroless copper plating solution on the copper film is as follows: formaldehyde is used as a reducing agent;
In comparison with the conventional electroless copper plating of No. 13, the deposition rate is about 1/2 or less, and the deposition rate of 0.5 μm / 30 minutes or less can be maintained.

Another example of an electroless copper plating solution capable of controlling the deposition rate of electroless copper plating on copper to 0.5 μm / 30 minutes or less includes copper ions and complex of copper ions. It contains citric acid or a salt thereof as an agent and hypophosphorous acid or a salt thereof as a reducing agent, and has a pH of 8.0 to 11.0.
And an electroless copper plating solution in the range of

The feature of this electroless plating solution is that citric acid or a salt thereof is used as a complexing agent for copper ions. The amount of the citric acid or salt thereof is preferably 1 to 10 times in molar ratio to copper ions. Electroless copper plating baths using an organic acid other than citric acid as a complexing agent for copper ions and using hypophosphorous acid as a reducing agent are known, but good results cannot be obtained by using them.

On the other hand, examples of the copper ion source of the electroless copper plating solution include copper sulfate, cupric chloride, and copper nitrate, all of which use hypophosphorous acid or a salt thereof as a reducing agent. It is generally used in the electroless copper plating bath used. In addition, the compounding amount may be about the same as that of an ordinary electroless copper plating bath using hypophosphorous acid or a salt thereof.

This electroless copper plating bath utilizes the property that hypophosphite does not have an autocatalytic effect on copper, and is combined with citric acid or a salt thereof to form a catalyst on palladium as a catalyst. When copper is deposited, no further deposition occurs, and the deposition rate on copper is 0.5 μm / 3.
It can be controlled to 0 minutes or less.

The method of the present invention is carried out by the same means for producing a printed wiring board as in the prior art, except that an electroless copper plating solution in which the deposition rate on copper is controlled to 0.5 μm / 30 minutes or less as described above is used. can do. That is, an example of conditions for processing a printed wiring board is as follows. Electroplating after electroless copper plating is not limited to copper electroplating, but may be performed using a desired material such as electrosolder plating or electrogold plating. Can be implemented.

[Basic operation process] Swelling process (65 to 85 ° C; 5 to 15 minutes) ↓ Etching process (65 to 85 ° C; 5 to 15 minutes) ↓ Chinese process (65 to 85 ° C) ; 5-10 minutes) ↓ Pre-soaking process (15-30 ° C; 1-3 minutes) ↓ (no water washing) Catalyst application process (15-30 ° C; 2-10 minutes) ↓ Promotion process (15-30 ° C) ; 2-10 minutes) ↓ Electroless copper plating process ↓ Electrolytic copper plating process Note) In the above, water washing is performed between processes.

[0024]

The reason why the method of the present invention can obtain high adhesion strength between the resin base material and the conductor layer is that the deposition of electroless copper plating on copper is suppressed, so that the inside of minute concave portions on the resin surface is also reduced. This is because the electroless copper plating is deposited on all the catalysts, including the catalyst, and sufficiently adheres to the catalyst to obtain good adhesion.

The precipitation control agent used in the present invention is included in the added stabilizer for the purpose of preventing self-decomposition of the plating bath. However, the stabilizer cannot always be used as the precipitation control agent. Absent. Further, it is not known that the stabilizer controls the deposition rate of electroless copper plating on copper, and it is not known that the adhesion is improved by controlling the deposition rate.

[0026]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited by these examples.

Example 1 Examination of the effect of suppressing precipitation: The effect of some compounds on the deposition of copper on a copper film was examined. The test was performed by immersing the copper-clad laminate in a composition obtained by adding the components and concentrations shown in Table 1 to the basic electroless copper plating bath composition using formalin as a reducing agent, and forming the copper plating layer under the following conditions. This was done by measuring the rate of deposition. The results are also shown in Table 1.

[Basic electroless plating bath composition] Copper sulfate pentahydrate 0.03M EDTA tetrahydrate 0.24M formalin 0.2M pH 12.5

[Electroless plating conditions] Bath temperature 60 ° C Stirring Air stirring

[0030]

[Table 1]

As is apparent from the results, thiourea,
In the case of allylthiourea, thiomalic acid, thioglycolic acid, potassium thiocyanate, etc., the deposition rate of electroless copper plating clearly decreases, and is less than half that of the case of performing the basic electroless plating composition, which is the condition of the method of the present invention. 0.5 μm / 3
The condition of 0 minutes was satisfied. In contrast, when 2-mercaptobenzothiazole or polyvinylimidazole was added, the deposition rate was high.

Example 2 Adhesion strength test: F having a size of 20 mm × 50 mm
An epoxy insulating varnish (photo via forming material: ILD-300 manufactured by JSR Corporation) was applied and cured on an R-4 substrate as a test piece. In the test, the substrate surface was first roughened according to the following processing steps.
Next, after applying a catalyst and promoting adhesion, the substrate was immersed for 30 minutes in an electroless copper plating bath obtained by adding the type and concentration of a precipitation control agent shown in Table 2 to the basic electroless copper plating composition of Example 1. Furthermore, a copper sulfate plating bath (EBARA Eugerite Co., Ltd.)
Electroplating was performed by a Cubelite TH process) to a thickness of about 30 μm.

The adhesion strength of the obtained copper plating film is 90
The adhesion was measured by a peel test. The adhesion strength was measured by peeling off vertically at a crosshead speed of 3 mm / sec with an Instron tester. Table 2 also shows the adhesion strength of each sample. The state of the peeled surface of the resin or the copper foil was observed with a scanning electron microscope (SEM).

[Processing process] Swelling process (75 ° C .; 10 minutes) ↓ Etching process (75 ° C .; 10 minutes) ↓ Middle process (75 ° C .; 10 minutes) ↓ Pre-soaking process (room temperature; 2) Min) ↓ (no water washing) Catalyst application process (normal temperature; 5 minutes) ↓ Promotion process (normal temperature; 5 minutes) ↓ Electroless copper plating process (60 ° C; 30 minutes) ↓ Baking process (1) (120 ° C; 60 minutes) ↓ Electrolytic copper plating step (25 ° C .; 2 A / dm ² ; 75 minutes) ↓ Baking step (2) (150 ° C .; 120 minutes) Note) In the above, water washing is performed between steps.

[0035]

[Table 2]

As a result, it was found that the electroless copper plating using the precipitation controlling agent improved the adhesion strength as compared with the non-added copper plating. From this, the electroless plating applied to form the conductor layer can improve the adhesion by the anchor effect if the film is formed uniformly to the bottom of the etching mark formed on the resin, and for this purpose, the It was shown that the speed needed to be controlled.

Example 3 Electroless copper plating and copper sulfate plating were performed on an epoxy resin substrate by the same plating conditions and steps as in Example 2 except that the following plating bath composition was used. When the adhesion strength of the obtained copper plating film was also measured in the same manner as in Example 2,
It was 1.0 kg / cm.

[Plating bath composition] Copper sulfate pentahydrate 0.032 M sodium citrate 0.052 M sodium hypophosphite 0.54 M boric acid 0.50 M pH 9.0

[0039]

According to the present invention, since a metal film having good adhesion can be formed on a resin base material by appropriately performing a bath control of the electroless copper plating, it is possible to print a multilayer wiring board or the like. This is extremely advantageous in manufacturing a wiring board. that's all

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hideo Honma 8-1-60 Sugita, Isogo-ku, Yokohama-shi, Kanagawa Prefecture (72) Inventor Junichi Ishibashi 9-2-307, Minesawa-cho, Hodogaya-ku, Yokohama-shi, Kanagawa Prefecture (72) Invention Person Masako Suzuki 2-11-24 Tsukiji, Chuo-ku, Tokyo Inside JSR Co., Ltd. (72) Inventor Emi Maruyama 1-1-6 Yoshiyukizaka, Fujisawa City, Kanagawa Prefecture Inside Ebara Ujilight Inc. (72) Inventor Tomoyuki Fujinami 1-1-6 Yoshiyukizaka, Fujisawa-shi, Kanagawa Ebara Ujilight Inc.

Claims (7)

[Claims] 1. An electroless copper plating method in which a plating deposition rate on copper is controlled to 0.5 μm / 30 minutes or less on a catalyzed resin substrate, followed by electroplating. High adhesion plating method to resin substrate. 2. An electroless copper plating solution containing copper ions, a complexing agent for copper ions, formaldehyde or glyoxylic acid as a reducing agent and a precipitation controlling agent, and having a pH in the range of 12 to 13. 2. The method for plating a resin substrate with high adhesion according to claim 1, wherein the method is carried out using the method. 3. The high adhesion to a resin substrate according to claim 2, wherein the precipitation inhibitor is a compound selected from thiourea, allylthiourea, thiomalic acid, thioglycolic acid, thiocyanic acid and salts thereof. Plating method. 4. The electroless copper plating contains copper ions, citric acid or a salt thereof as a complexing agent for copper ions and hypophosphorous acid or a salt thereof as a reducing agent, and has a pH of 8.0 to 11.
2. The method for plating a resin substrate with high adhesion according to claim 1, wherein the method is performed using an electroless copper plating solution having a range of 0. 5. An electroless copper plating solution containing copper ions, a complexing agent for copper ions, formaldehyde or glyoxylic acid as a reducing agent and a precipitation controlling agent, and having a pH in the range of 12 to 13. 6. The method according to claim 5, wherein the precipitation inhibitor is a compound selected from thiourea, allylthiourea, thiomalic acid, thioglycolic acid, thiocyanic acid and salts thereof.
Electroless copper plating solution according to the item. 7. An electroless copper plating containing copper ions, a citric acid or a salt thereof as a complexing agent for copper ions and hypophosphorous acid or a salt thereof as a reducing agent, and having a pH in the range of 8.0 to 11.0. liquid.