JP2000160350A - Electroless silver plating solution for electronic parts - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an electroless silver plating soln. for electronic parts having a migration preventive effect and by which the service life of a plating bath is prolonged. SOLUTION: This plating soln. consists of a silver salt, a fluoric surfactant and a pH buffer salt. Silver nitrate is used as the silver salt, and >=1 kind between succinimide and phthalimide is used as a silver complexing agent. The soln. contains 0.05-30 g/l silver ion, 0.1-200 g/l >=1 kind between succinimide and phthalimide and 0.01-10 g/l fluorine surfactant and further contains an inorg. acid, an org. acid or both as the pH buffer salt.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an electroless silver plating solution for electronic parts.

[0002]

2. Description of the Related Art Conventionally, in the manufacture of electronic parts such as printed wiring boards, a Ni alloy layer is provided on a copper pattern, or an Sn-Pb alloy layer is provided on a gold or copper pattern, and a capacitor, a resistor, a transistor, Components such as IC are mounted. However, in recent years, the use of Pb, which is a harmful substance, has been discontinued from the viewpoint of environmental conservation, and the use of Ni has been restricted.

[0003] Therefore, a method of producing an electronic component having an Ag plating layer provided on a copper pattern without using Ni or Pb has been attempted. However, Ag easily causes migration (electrolytic migration), and thus often causes a short circuit or breakdown failure. Migration is a type of electrolytic corrosion, and refers to a phenomenon in which when a voltage is applied between two electrodes in an insulator having relatively high hygroscopicity, the electrode metal is eluted as ions from the anode, resulting in electrolytic corrosion. 2AgOH → Ag ₂ O + H ₂ O near the anode,
Ag ₂ O colloid is generated, and Ag ₂ O is reduced by a reducing substance in the insulator or by an external factor to become Ag ions and precipitates as a needle-like crystal on the cathode to cause an electrical short circuit or dielectric breakdown. Become. For this reason, many measures and improvements are required to completely shut off the outside air or to prevent Ag from being emitted outside the mode.

In addition, a conventional electroless silver plating bath uses a sulfone compound or a compound having a polydentate ligand such as ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, or nitrilotriacetic acid as a silver complexing agent. Therefore, the plating bath is very unstable, and Ag deposits abnormally in the plating tank due to aging or light, and the deposited pieces adhere to the product, resulting in defective products.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide an electroless silver plating solution for electronic parts having a migration preventing effect and a long plating bath life.

[0006]

The present invention has the following features. (1) a silver salt, a silver complexing agent, a fluorine-based surfactant, and
An electroless silver plating solution for electronic components, comprising a pH buffer salt. (2) The electroless silver plating solution according to the above (1), wherein the silver salt is silver nitrate and the silver complexing agent is at least one of succinimide and phthalic imide. (3) 0.05 to 30 g / l of silver ions, 0.1 to 200 g of at least one of succinimide and phthalimide
An electroless silver plating solution for electronic parts, characterized by containing 0.01 to 10 g / l of a fluorine-containing surfactant and at least one of inorganic acids and organic acids as a PH buffer salt.

(4) The fluorine-based surfactant is a perfluoroalkyl sulfonate, a perfluoroalkyl carboxylate, a perfluoroalkyl phosphate, a perfluoroalkylammonium iodide, a perfluoroalkylamine oxide, a perfluoroalkyl The electroless silver plating solution for electronic components according to the above (1) or (3), which is at least one of trimethylammonium salts.

Hereinafter, the present invention will be described in detail.
The electroless silver plating solution for an electronic component of the present invention comprises a silver salt, a silver complexing agent, a fluorine-based surfactant, and a PH buffer salt. Silver nitrate is suitable as the silver salt, and succinimide or phthalimide is suitable as the silver complexing agent.

[0009] Fluorinated surfactants include perfluoroalkyl sulfonates, perfluoroalkyl carboxylates, perfluoroalkyl phosphates, perfluoroalkylammonium iodides, perfluoroalkylamine oxides, perfluoroalkyltrimethylammonium Salt is used. As the PH buffer salt, a phosphate compound, a boric acid compound, a carboxylic acid compound, an oxyacid compound, an inorganic acid such as a carbohydrate, or an organic acid or both compounds are used.

Although the electroless silver plating solution of the present invention generally uses a silver complexing agent, a copper complexing agent may be added when the underlying copper material is dissolved. As the copper complexing agent, ethylenediaminetetraacetate, nitrilotriacetate, and diethylenetriaminepentaacetate are generally used.

The electroless silver plating solution of the present invention contains 0.05 to 30 g / l of silver ions, 0.1 to 200 g / l of at least one of succinimide and phthalic imide, and 0.1 to 200 g / l of a fluorine surfactant. Preferably, it contains from 01 to 10 g / l and a pH buffer salt.

[0012]

EXAMPLES Hereinafter, the electroless silver plating solution for electronic parts of the present invention will be described with reference to Examples and Comparative Examples. An example in which a printed wiring board is used as an electronic component and the electroless silver plating solution of the present invention is used for the production thereof will be described. Using various electroless silver plating solutions, printed wiring boards were manufactured by the following manufacturing steps. That is, the organic printed circuit board patterned by copper plating or etching is degreased, chemically polished, and immersed in an acid by a conventional method, and is then placed in various electroless silver plating solutions having the compositions shown in Table 1 at 35 ° C. for 3 to 8 minutes. Immerse 0.
A printed wiring board having a silver plating thickness of 10 μm was manufactured.

The silver layers of the printed wiring boards obtained by using various electroless silver plating solutions having the compositions shown in Table 1 were subjected to (1) a migration test and (2) a solder wetting test. Further, (3) plating bath life test was conducted to investigate the bath stability of various electroless silver plating solutions. The points of the performance tests (1) to (3) are as follows.

(1) Migration property test A silver-plated printed wiring board having a comb-shaped test pattern with a gap of 0.3 mm is used, and a humidity of 90 to 95% RH and a DC voltage of 50 V are applied between the poles as environmental acceleration test conditions. Then, the occurrence of migration after 48 hours and 480 hours was observed and evaluated with a microscope.

(2) Solder wettability test: The solder wettability test was performed on a pad pattern of a silver-plated printed wiring board with a diameter of 0.3 mm.
Place a 5 mm solder ball and use an inactive rosin-based flux (trade name: R-100: manufactured by α Metal Co., Ltd.) for 230
The solder wettability after heating at 30 ° C. for 30 seconds was observed and evaluated.

(3) Plating bath life test An electroless silver plating solution having various compositions shown in Table 1 was heated to 60 ° C.
For 12 hours in a constant temperature bath, and the presence or absence of silver precipitation in the silver plating solution was observed and evaluated.

Table 2 shows the results of the performance evaluation test. In Table 2, A: excellent, B: slightly excellent, C:
Inferior, D: Inferior.

As can be seen from the results shown in Table 2, with respect to Sample Nos. 1 to 9 included in the scope of the present invention, no migration occurred after 48 hours and 480 hours in the migration test, and there was no environmental acceleration test. And the solder wettability after 1 hour test of 0.1 ppm of H ₂ S were good. Further, there was no decomposition of the plating bath in the plating bath life test.

On the other hand, sample numbers 10 to 10 out of the scope of the present invention
13 was a low evaluation in any of the migration test, the solder wettability test, and the plating bath life test, and only C or D was obtained in the overall evaluation.

[0020]

[Table 1]

[0021]

[Table 2]

[0022]

According to the present invention, an electroless silver plating solution for electronic parts having an excellent effect of preventing migration, good solder wettability, and a long plating bath life was obtained.

Claims (4)

[Claims] 1. An electroless silver plating solution for electronic parts, comprising a silver salt, a silver complexing agent, a fluorine-based surfactant and a PH buffer salt. 2. The electroless silver plating solution according to claim 1, wherein the silver salt is silver nitrate and the complexing agent for silver is at least one of succinimide and phthalic imide. 3. A silver ion of 0.05 to 30 g / l, at least one of succinimide and phthalic imide.
00 g / l, fluorinated surfactant 0.01 to 10 g / l
An electroless silver plating solution for electronic parts, comprising: a pH buffer salt containing at least one of an inorganic acid and an organic acid. 4. The fluorosurfactant is a perfluoroalkyl sulfonate, a perfluoroalkyl carboxylate, a perfluoroalkyl phosphate, a perfluoroalkylammonium iodide, a perfluoroalkylamine oxide, a perfluoroalkyltrimethyl. 4. The electroless silver plating solution for electronic components according to claim 1, wherein the electroless silver plating solution is at least one of ammonium salts.