PLATING SOLUTION OF PALLADIUM ALLOY AND METHOD FOR PLATING USING THE SAME

Abstract

The present invention relates to a plating solution of palladium alloy and has an object to provide a plating solution of palladium alloy highly stable and capable of stably forming a plated film of a given alloy composition. The present invention relates to a plating solution of palladium alloy containing a palladium complex and a metal salt, wherein the palladium complex is coordinated with at least one neutral amino acid selected from the group consisting of glycine, alanine, valine, leucine, serine, threonine, asparagine, glutamine and tyrosine as a ligand.

Description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the invention are described below.

Examples 1 to 5

These examples used respective neutral amino acids of serine, valine, alanine, glycine and leucine as ligands for palladium complexes. The plating treatment was carried out with plating solution compositions and under conditions shown in Table 1.

	TABLE 1
	Solution composition	Concentration
Example 1	Palladium salt	Palladium chloride	(Pd concentration)	10	g/L
	Gold salt	Sodium gold sulfite	(Au concentration)	1	g/L
	Neutral amino acid	DL-serine		1	mol/L
	Stabilizer	Sodium sulfite		50	g/L
	Buffering agent	Disodium hydrogen		40	g/L
		phosphate
	Plating conditions . . . pH 9, 60° C., 1 A/dm2
Example 2	Palladium salt	Palladium chloride	(Pd concentration)	5	g/L
	Gold salt	Sodium gold sulfite	(Au concentration)	1	g/L
	Neutral amino acid	DL-valine		1	mol/L
	Stabilizer	Sodium sulfite		50	g/L
	Buffering agent	sodium carbonate		50	g/L
	Plating conditions . . . pH 10, 60° C., 1 A/dm2
Example 3	Palladium salt	Palladium chloride	(Pd concentration)	5	g/L
	Gold salt	Sodium gold sulfite	(Au concentration)	1	g/L
	Neutral amino acid	DL-alanine		0.5	mol/L
	Stabilizer	Sodium sulfite		50	g/L
	Buffering agent	Disodium hydrogen		50	g/L
		phosphate
	Plating conditions . . . pH 10, 60° C., 3 A/dm2
Example 4	Palladium salt	Palladium chloride	(Pd concentration)	10	g/L
	Gold salt	Sodium gold sulfite	(Au concentration)	5	g/L
	Neutral amino acid	DL-glycine		0.5	mol/L
	Stabilizer	Sodium sulfite		50	g/L
	Buffering agent	Disodium tetraborate + hydrate		50	g/L
	Plating conditions . . . pH 9, 50° C., 1 A/dm2
Example 5	Palladium salt	Palladium sulfate	(Pd concentration)	5	g/L
	Gold salt	Sodium gold sulfite	(Au concentration)	1	g/L
	Neutral amino acid	DL-leucine		0.5	mol/L
	Stabilizer	Sodium sulfite		100	g/L
	Buffering agent	Trisodium citrate dihydrate		50	g/L
	Plating conditions . . . pH 7.5, 60° C., 1 A/dm2

Conventional Example

The plating treatment was carried out using diamine dichloropalladium as a palladium salt with a plating solution composition and under conditions shown in Table 2.

	TABLE 2
	Solution composition	Concentration
Conventional	Palladium salt	Diamine dichloropalladium	(Pd concentration)	1.8 g/L
Example	Gold salt	Sodium gold sulfite	(Au concentration)	10 g/L
		Ammonium sulfate		15 g/L
	Plating conditions . . . pH 8.2, 55° C., 0.5 A/dm2

Examples 6 and 7

These examples used a silver salt and a copper salt as a metal salt, respectively, and the plating treatment was carried out with plating solution compositions and under conditions shown in Table 3.

	TABLE 3
	Solution composition	Concentration
Example 6	Palladium salt	Palladium chloride	(Pd concentration)	10	g/L
	Silver salt	Silver nitrate	(Ag concentration)	0.1	g/L
	Neutral amino acid	Asparagine		0.5	mol/L
	Stabilizer	Sodium thiosulfate		50	g/L
	Buffering agent	Dipotassium hydrogen		50	g/L
		phosphate
	Plating conditions . . . pH 70, 60° C., 1 A/dm2
Example 7	Palladium salt	Palladium chloride	(Pd concentration)	10	g/L
	Copper salt	Copper nitrate	(Cu concentration)	1.0	g/L
	Neutral amino acid	Asparagine		0.5	mol/L
	Stabilizer	Dipotassium citrate		100	g/L
	Buffering agent	Dipotassium hydrogen		50	g/L
		phosphate
	Plating conditions . . . pH 7.0, 60° C., 1 A/dm2

On completion of the plating treatment, each of the thin films of alloy formed was visually observed for the external appearance, and analyzed by ICP emission spectroscopy for eutectoid rate (% by weight) of the palladium and metal ions in the plated film dissolved in aqua regalis. The results are given in Tables 4 and 5.

	TABLE 4
	Eutectoid rate (% by weight)
	External Appearance*	Pd	Au
Example 1	◯	75	25
Example 2	◯	80	20
Example 3	◯	90	10
Example 4	◯	60	40
Example 5	◯	85	15
Conventional	X	20	80
Example
*◯: Uniform, good external appearances, X: Irregularities observed on the surface

As shown in Table 4, the alloy film formed in each of Examples 1 to 5 had good quality with uniform external appearances. For a palladium eutectoid rate in the plated film, it was within a range from 40 to 90% by weight to give the excellent Pd—Au alloy film. On the other hand, the plating solution used in Comparative Example evolved precipitates during the plating work, and gave the uneven plated film with surface irregularities. Moreover, the plated film had a palladium eutectoid rate of 20% by weight.

	TABLE 5
	External	Eutectoid rate (% b weight)
	Appearance*	Pd	Ag or Cu
	Example 6	◯	80	20
	Example 7	◯	60	40
	*◯: Uniform, good external appearances, X: Irregularities observed on the surface

As shown in Table 5, the alloy film formed in each of Examples 6 and 7 which used a silver nitrate and a copper nitrate as a metal salt, respectively, had good quality with uniform external appearances. For a palladium eutectoid rate, it was within a range from 40 to 90% by weight to give the excellent Pd—Ag or Pd—Cu alloy film.

Claims

1. A plating solution of palladium alloy comprising a palladium complex and a metal salt, wherein the palladium complex is coordinated with at least one neutral amino acid selected from the group consisting of glycine, alanine, valine, leucine, serine, threonine, asparagine, glutamine and tyrosine as a ligand.

2. The plating solution of palladium alloy according to claim 1, wherein the palladium complex is formed by dispersing, in a solvent, at least one palladium salt selected from the group consisting of palladium chloride, palladium sulfate, palladium nitrate, palladium hydroxide and palladium oxide, and the neutral amino acid.

3. The plating solution of palladium alloy according to claim 1, wherein the metal salt is one of gold salt, silver salt and copper salt.

4. The plating solution of palladium alloy according to claim 1, wherein the neutral amino acid is present at 0.1 to 2.0 mol/L.

5. The plating solution of palladium alloy according to claim 1, wherein palladium is present at a concentration of 1 to 30 g/L as Pd.

6. The plating solution of palladium alloy according to claim 1, wherein the metal salt is present at a concentration of 0.1 to 30 g/L as the metal.

7. A palladium alloy plating method comprising forming a plated film with the plating solution of palladium alloy according to claim 1, carried out under the conditions of pH: 6 to 10, temperature: 30 to 80° C. and current density: 0.1 to 7.0 A/dm2.

8. A hydrogen separation membrane produced by the palladium alloy plating method according to claim 7.

9. The plating solution of palladium alloy according to claim 2, wherein the metal salt is one of gold salt, silver salt and copper salt.

10. The plating solution of palladium alloy according to claim 2, wherein the neutral amino acid is present at 0.1 to 2.0 mol/L.

11. The plating solution of palladium alloy according to claim 3, wherein the neutral amino acid is present at 0.1 to 2.0 mol/L.

12. The plating solution of palladium alloy according to claim 9, wherein the neutral amino acid is present at 0.1 to 2.0 mol/L.

13. The plating solution of palladium alloy according to claim 2, wherein palladium is present at a concentration of 1 to 30 g/L as Pd.

14. The plating solution of palladium alloy according to claim 3, wherein palladium is present at a concentration of 1 to 30 g/L as Pd.

15. The plating solution of palladium alloy according to claim 9, wherein palladium is present at a concentration of 1 to 30 g/L as Pd.

16. The plating solution of palladium alloy according to claim 4, wherein palladium is present at a concentration of 1 to 30 g/L as Pd.

17. The plating solution of palladium alloy according to claim 10, wherein palladium is present at a concentration of 1 to 30 g/L as Pd.

19. The plating solution of palladium alloy according to claim 11, wherein palladium is present at a concentration of 1 to 30 g/L as Pd.

20. The plating solution of palladium alloy according to claim 12, wherein palladium is present at a concentration of 1 to 30 g/L as Pd.