JP2001003179A - Electroless palladium-molybdenum alloy plating solution and plating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare an electroless palladium-molybdenum alloy plating soln. with which a plating layer excellent in bonding properties an solder joinability is obtained, and to provide a plating method. SOLUTION: This electroless palladium-molybdenum alloy plating soln. is obtd. by adding a molybdenum compd. to an electroless palladium plating soln. contg. a palladium compd., a reducing agent selected from formic acid and the salts thereof, hypophosphorous acid and the salts thereof, phosphorous acid and the salts thereof, a boron hydroxide compd. and amine boranes, a complexing agent selected from ammonia and amines, a buffer selected from carbonic acid and borates and a stabilizer selected from a sulfur compd. and a lead compd.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electroless palladium-molybdenum alloy plating solution and a plating method suitable for plating an electronic component having a bonding portion and a soldering portion.

[0002]

2. Description of the Related Art Conventionally, as an electroless plating method for an electronic component having a bonding portion and a solder bonding portion, a method in which an electroless gold plating layer is provided on an electroless nickel plating layer has been mainly used. However, since electroless gold plating is expensive, electroless palladium plating has recently been used in place of electroless gold plating. However, in the configuration of the electroless nickel layer / electroless palladium layer / electroless gold plating layer in which a part of the electroless nickel layer / electroless palladium layer or the electroless gold plating layer is replaced with the electroless palladium layer,
Although the bonding property is good, the solder bonding property is poor, and in particular, in the ball solder bonding, a dropout failure of the ball solder occurs.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide an electroless palladium-molybdenum alloy plating solution and a plating method capable of obtaining a plating layer having excellent bondability and solder jointability.

[0004]

Means for Solving the Problems In order to solve the above problems, the present inventors have carried out various investigations and studies to improve the solderability of the electroless palladium plating layer. Palladium-molybdenum alloy plating using an electroless palladium-molybdenum alloy plating solution with a molybdenum compound added to the solution,
The present invention has been made based on the finding that a plating layer having excellent bonding properties and solder bonding properties can be obtained.

That is, in the electroless palladium-molybdenum alloy plating solution of the present invention, a palladium compound, formic acid and its salt, hypophosphorous acid and its salt, phosphorous acid and its salt, borohydride compound, and amine borane Electroless palladium plating containing a reducing agent selected from the group consisting of a complexing agent selected from ammonia and amines, a buffering agent selected from carboxylic acids and borates, and a stabilizer selected from sulfur compounds and lead compounds For example, 0.05 to 20 g / L (L is liter, the same applies hereinafter) of a molybdenum compound is added to the liquid, and a surfactant as a bit preventing agent is added as necessary.

In the electroless palladium-molybdenum alloy plating method of the present invention, the article to be plated is immersed in the electroless palladium-molybdenum alloy plating solution.
That is, a palladium-molybdenum alloy plating layer is formed on the entire surface or a part of the article to be plated.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below. The palladium compound used in the electroless palladium-molybdenum alloy plating solution of the present invention may be any water-soluble palladium compound, such as palladium chloride, palladium sulfate, palladium nitrite, and palladium acetate. Can be. The amount of Pd is preferably 0.1 to 25 g / L as Pd. If the amount is too small, the plating rate will decrease, and if it is too large, it is not economical.

Further, as a reducing agent, formic acid, formate such as sodium formate, hypophosphorous acid, hypophosphite such as sodium hypophosphite, borohydride compound such as potassium borohydride, dimethyl One of aminoboranes such as aminoborane and trimethylaminoborane is used. The used amount is 0.01 to 0.5 mol / L. When the amount is too small, the plating rate decreases, and when the amount is too large, the plating bath becomes unstable. Further, as the complexing agent, ammonia, triethanolamine, dimethylamine, trimethylamine,
Amines such as diethylamine, ethylenediamine, diacetylenetriamine, triethylenetetramine, EDTA, and N-hydroxyethylenediaminetriacetic acid are used. The used amount is 0.05 to 2 mol / L. If the amount is too small, the plating bath becomes unstable, and if the amount is too large, the plating rate decreases.

As the buffer, boric acid, borate such as potassium borate, potassium citrate, citric acid, potassium tartrate, potassium oxalate, malic acid, malonic acid, potassium succinate, adibic acid, fumaric acid Or any of the carboxylate salts such as maleic acid. The used amount is 0.01 to 0.5 mol / L. If the amount is too small, the buffering action is weak, and if it is too large, it is not economical. As the stabilizer, any one of a sulfur compound such as a thiosulfate, a sulfite and an organic thio compound or a water-soluble lead compound such as lead acetate and lead citrate is used. The amount used is 0.1 ~
At 50 ppm, if too small, the plating bath becomes unstable,
If the amount is too large, the plating rate decreases.

The electroless palladium-molybdenum alloy plating solution of the present invention is obtained by adding a molybdenum compound to the above components. The molybdenum compound may be a water-soluble molybdenum compound such as sodium molybdate or ammonium molybdate. Any one may be used. The addition amount of this molybdenum compound is 0.05 as molybdenum.
When the amount is too small, the above effects cannot be obtained, and when the amount is too large, the bondability decreases. A nonionic, anionic, cationic, or amphoteric surfactant may be further added to the electroless palladium-molybdenum alloy plating solution of the present invention as a bit inhibitor.
The added amount is 0.005 to 10 g / L.

The electroless palladium-molybdenum alloy plating solution of the present invention is suitable as a plating film for a bonding portion or a solder bonding portion of an electronic component. can get.

[0012]

EXAMPLES Examples and comparative examples of the present invention will be described below. Example 1 ₂ g / L as PdCl ₂ Pd 0.1 mol / L potassium formate 0.1 mol / L ammonia 2 mol / L boric acid 0.5 mol / L Lead acetate 1 ppm as lead Sodium molybdate 0.05 g / L as molybdenum pH 7 Liquid temperature 70 ° C.

Example 2 ₂ g / L of PdCl ₂ Pd / L sodium hypophosphite 0.5 mol / L Diethylamine 0.1 mol / L Potassium citrate 0.25 mol / L Sodium thiosulfate 25 ppm Sodium molybdate 0.5 g / molybdenum L pH 8 Liquid temperature 60 ℃

Example 3 PdCl ₂ Pd 2 g / L sodium hypophosphite 0.3 mol / L triethylenetetramine 0.05 mol / L potassium succinate 0.1 mol / L sodium thiosulfate 40 ppm sodium molybdate 5 g / molybdenum L pH 8 Liquid temperature 60 ℃

Example 4 ₂ g / L as PdCl ₂ Pd Trimethylaminoborane 0.02 mol / L N-hydroxyethylenediaminetriacetic acid 1 mol / L Fumaric acid 0.1 mol / L Sodium sulfite 40 ppm Sodium molybdate 20 g / L as molybdenum pH 8 Liquid temperature 70 ° C

Example 5 PdCl ₂ Pd 2 g / L Potassium formate 0.1 mol / L Ammonia 2 mol / L Boric acid 0.5 mol / L Lead acetate 1 ppm as lead Sodium molybdate 20 g / L as molybdenum pH 7 Liquid temperature 70 ° C.

Comparative Examples Among the bath compositions of Examples 1 to 4, those containing no molybdenum compound were compared with those of Comparative Examples 1 to 4.
And the molybdenum concentration in the bath composition of Example 5 was 40 g /
What was set to L was set as the comparative example 5.

Each of the test pieces, each of which has been subjected to electroless Ni plating, is immersed in the above electroless plating bath, and an electroless palladium-molybdenum alloy plating layer or an electroless palladium plating layer is plated to a thickness of 0.3 μm. The layer was plated at 0.05 μm, and the test pieces were tested for bondability and solder jointability by the following methods. The results are shown in Table 1 below.
Shown in <Method of evaluating bondability> Ten test pieces each having a thickness of 25 μm were plated using a wire bonding machine.
The peel strength was measured using a gold wire. <Method of Evaluating Bondability of Ball Solder> Ten pieces of each of the test pieces were plated with Sn: Pb = 63 having a diameter of 0.76 μm.
%: Ball solder bonding was repeated twice at 220 ° C. for 50 seconds using 37% ball solder, and the ball solder bonding strength was measured with a bush gauge.

[0019]

[Table 1]

From the above results, all of the electroless palladium-molybdenum alloy plating solutions containing a molybdenum compound of the present invention were excellent in wire bonding property and ball soldering property. Each of the electroless palladium plating solutions containing no molybdenum compound of Comparative Examples 1 to 4 was slightly inferior in ball solder jointability. Further, the one plated with the electroless palladium-molybdenum alloy plating solution of Comparative Example 5 in which a molybdenum compound was added more than the scope of the present invention had poor wire bonding properties.

[0021]

The plating layer plated using the electroless palladium-molybdenum alloy plating solution of the present invention can provide excellent wire bonding properties and ball solder bonding properties.

Claims (3)

[Claims] 1. A palladium compound, formic acid and a salt thereof,
Selected from hypophosphorous acid and salts thereof, phosphorous acid and salts thereof, borohydride compounds, reducing agents selected from amineboranes, complexing agents selected from ammonia and amines, and carboxylic acids and borates An electroless palladium-molybdenum alloy plating solution obtained by adding a molybdenum compound to an electroless palladium plating solution containing a buffering agent and a stabilizer selected from a sulfur compound and a lead compound. 2. The amount of the molybdenum compound added is 0.0
The electroless palladium-molybdenum alloy plating solution according to claim 1, wherein the amount is 5 to 20 g / L. 3. A plating object is immersed in the electroless palladium / molybdenum alloy plating solution according to claim 1 or 2 to form a palladium / molybdenum alloy plating layer on the surface of the plating object. An electroless palladium-molybdenum alloy plating method characterized by the following: