Bonding copper wire plated with palladium and gold and electroplating process thereof

Abstract

The present application relates to the technical field of electroplating, and particularly to a bonding copper wire plated with palladium and gold and an electroplating process thereof. The electroplating process includes: electroplating a first palladium layer on a surface of a copper wire with a first palladium plating solution, electroplating a second gold layer with a first gold plating solution to obtain a semi-finished product, electroplating a third palladium layer onto the semi-finished product with a second palladium plating solution, and electroplating a fourth gold layer with a second gold plating solution to obtain a finished product; and the first palladium plating solution comprises tetraamminepalladium acetate, 4-sulfamoylbenzoic acid and 6-azauracil.

Claims

1. An electroplating process for a bonding copper wire plated with palladium and gold, comprising: electroplating a first palladium layer on a surface of a copper wire with a first palladium plating solution, electroplating a first gold layer with a first gold plating solution to obtain a semi-finished product, electroplating a second palladium layer onto the semi-finished product with a second palladium plating solution, and electroplating a second gold layer with a second gold plating solution to obtain a finished product; wherein the first palladium plating solution comprises tetraamminepalladium acetate, 4-sulfamoylbenzoic acid and 6-azauracil.

2. The electroplating process for a bonding copper wire plated with palladium and gold according to claim 1, wherein in electroplating the first palladium layer, in the first palladium plating solution, a concentration of the tetraamminepalladium acetate is maintained at 5-8 g/L, a concentration of the 4-sulfamoylbenzoic acid is maintained at 5-15 mg/L and a concentration of the 6-azauracil is maintained at 1-5 mg/L.

3. The electroplating process for a bonding copper wire plated with palladium and gold according to claim 1, wherein the first palladium plating solution further comprises methionine; and methionine has a concentration of 10-20 mg/L in the first palladium plating solution.

4. The electroplating process for a bonding copper wire plated with palladium and gold according to claim 1, wherein the second palladium plating solution comprises a palladium salt, 3-chloro-4-fluoroaniline, calcium dinonylnaphthalene sulfonate and ?-cyano-L-alanine.

5. The electroplating process for a bonding copper wire plated with palladium and gold according to claim 4, wherein the palladium salt is one or more selected from the group consisting of tetraamminepalladium(II) dichloride, diaminedinitritopalladium(II), palladium diammine dichloride and trans-dibromodiamminpalladium (II).

6. The electroplating process for a bonding copper wire plated with palladium and gold according to claim 4, wherein in electroplating the second palladium layer, in the second palladium plating solution, a concentration of the palladium salt is maintained at 6-10 g/L, a concentration of the 3-chloro-4-fluoroaniline is maintained at 3-13 mg/L, a concentration of the calcium dinonylnaphthalene sulfonate is maintained at 2-6 mg/L, and a concentration of the ?-cyano-L-alanine is maintained at 12-22 mg/L.

7. The electroplating process for a bonding copper wire plated with palladium and gold according to claim 1, wherein the copper wire has a diameter of 180-220 ?m; the electroplating process for a bonding copper wire plated with palladium and gold further comprises performing a first wire drawing to the semi-finished product, and the semi-finished product has a diameter of 90-105 ?m after the first wire drawing; and the electroplating process for a bonding copper wire plated with palladium and gold further comprises performing a second wire drawing to the finished product, and the finished product has a diameter of 15-22 ?m after the second wire drawing.

8. The electroplating process for a bonding copper wire plated with palladium and gold according to claim 1, wherein the electroplating the first palladium layer, the electroplating the first gold layer, the electroplating the second palladium layer and the electroplating the second gold layer are performed at a temperature of 70-85? C., with a current of 10-80 mA, for a period of 10-30 min.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a SEM image of a spherical end formed by a bonding copper wire plated with palladium and gold prepared in Example 1 after electrolytic corrosion.

(2) FIG. 2 is a SEM image of a spherical end formed by a bonding copper wire plated with palladium and gold prepared in Comparative example 6 after electrolytic corrosion.

DETAILED DESCRIPTION

Example 1

(3) In this example, a bonding copper wire plated with palladium and gold was prepared, and the electroplating process for a bonding copper wire plated with palladium and gold includes:

(4) electroplating a first palladium layer on a surface of a copper wire with a first palladium plating solution, electroplating a second gold layer with a first gold plating solution to obtain a semi-finished product, electroplating a third palladium layer onto the semi-finished product with a second palladium plating solution, and electroplating a fourth gold layer with a second gold plating solution to obtain a finished product, i.e., the bonding copper wire plated with palladium and gold. The bonding copper wire plated with palladium and gold included a copper core wire, the first palladium layer, the second gold layer, the third palladium layer and the fourth gold layer arranged from inside to outside.

(5) The electroplating the first palladium layer, the electroplating the second gold layer, the electroplating the third palladium layer and the electroplating the fourth gold layer were performed at a temperature of 70? C., with an current of 10 mA, for a period of 10 min.

(6) The first palladium plating solution included tetraamminepalladium acetate, 4-sulfamoylbenzoic acid and 6-azauracil. During an electroplating process, in the first palladium plating solution, the concentration of the tetraamminepalladium acetate is maintained at 7-8 g/L, the concentration of the 4-sulfamoylbenzoic acid is maintained at 12-15 mg/L and the concentration of the 6-azauracil is maintained at 1-2 mg/L.

(7) The second palladium plating solution included tetraamminepalladium(II) dichloride, 3-chloro-4-fluoroaniline, calcium dinonylnaphthalene sulfonate and ?-cyano-L-alanine. During the electroplating process, in the second palladium plating solution, the concentration of the tetraamminepalladium(II) dichloride was maintained at 6-8 g/L, the concentration of the 3-chloro-4-fluoroaniline was maintained at 10-13 mg/L, the concentration of the calcium dinonylnaphthalene sulfonate was maintained at 2-4 mg/L, and the concentration of the ?-cyano-L-alanine was maintained at 18-22 mg/L.

(8) Both the first gold plating solution and the second gold plating solution were potassium dicyanoaurate solution. The potassium dicyanoaurate in the first gold plating solution and the second gold plating solution was maintained at the concentration of 6-8 g/L. During a process of adjusting the first gold plating solution and the second gold plating solution by ammonia, both the first gold plating solution and the second gold plating solution had a pH of 10-12.5.

Example 2

(9) Comparing with Example 1, in this example, the temperature, current and period of electroplating, proportion and pH of each plating solution, and types of palladium salt were adjusted.

(10) In this example, a bonding copper wire plated with palladium and gold was prepared, and the electroplating process for a bonding copper wire plated with palladium and gold includes:

(11) electroplating a first palladium layer on a surface of a copper wire with a first palladium plating solution, electroplating a second gold layer with a first gold plating solution to obtain a semi-finished product, electroplating a third palladium layer onto the semi-finished product with a second palladium plating solution, and electroplating a fourth gold layer with a second gold plating solution to obtain a finished product, i.e., the bonding copper wire plated with palladium and gold. The bonding copper wire plated with palladium and gold included a copper core wire, the first palladium layer, the second gold layer, the third palladium layer and the fourth gold layer arranged from inside to outside.

(12) The electroplating the first palladium layer, the electroplating the second gold layer, the electroplating the third palladium layer and the electroplating the fourth gold layer were performed at a temperature of 85? C., with an current of 80 mA, for a period of 30 min.

(13) The first palladium plating solution included tetraamminepalladium acetate, 4-sulfamoylbenzoic acid and 6-azauracil. During the electroplating process, in the first palladium plating solution, the concentration of the tetraamminepalladium acetate was maintained at 5-6 g/L, the concentration of the 4-sulfamoylbenzoic acid was maintained at 5-8 mg/L and the concentration of the 6-azauracil was maintained at 4-5 mg/L.

(14) The second palladium plating solution included diaminedinitritopalladium(II), 3-chloro-4-fluoroaniline, calcium dinonylnaphthalene sulfonate and ?-cyano-L-alanine. During the electroplating process, in the second palladium plating solution, the concentration of the diaminedinitritopalladium(II) was maintained at 8-10 g/L, the concentration of the 3-chloro-4-fluoroaniline was maintained at 3-5 mg/L, the concentration of the calcium dinonylnaphthalene sulfonate was maintained at 4-6 mg/L, and the concentration of the ?-cyano-L-alanine was maintained at 12-15 mg/L.

(15) Both the first gold plating solution and the second gold plating solution were potassium dicyanoaurate solution. The potassium dicyanoaurate in the first gold plating solution and the second gold plating solution was maintained at a concentration of 6-8 g/L. During the process of adjusting the first gold plating solution and the second gold plating solution by ammonia, both the first gold plating solution and the second gold plating solution had a pH of 13-15.

Example 3

(16) In this example, the temperature, current and period of electroplating, proportion and pH of each plating solution, and types of palladium salt were adjusted relative to Example 1, and methionine was added into the first palladium plating solution.

(17) In this example, a bonding copper wire plated with palladium and gold was prepared, and the electroplating process for a bonding copper wire plated with palladium and gold includes:

(18) electroplating a first palladium layer on a surface of a copper wire with a first palladium plating solution, electroplating a second gold layer with a first gold plating solution to obtain a semi-finished product, electroplating a third palladium layer onto the semi-finished product with a second palladium plating solution, and electroplating a fourth gold layer with a second gold plating solution to obtain a finished product, i.e., the bonding copper wire plated with palladium and gold. The bonding copper wire plated with palladium and gold included a copper core wire, the first palladium layer, the second gold layer, the third palladium layer and the fourth gold layer arranged from inside to outside.

(19) The electroplating the first palladium layer, the electroplating the second gold layer, the electroplating the third palladium layer and the electroplating the fourth gold layer were performed at a temperature of 75? C., with an current of 40 mA, for a period of 20 min.

(20) The first palladium plating solution included tetraamminepalladium acetate, 4-sulfamoylbenzoic acid, 6-azauracil, and methionine. During the electroplating process, in the first palladium plating solution, the concentration of the tetraamminepalladium acetate was maintained at 6-7 g/L, the concentration of the 4-sulfamoylbenzoic acid was maintained at 9-11 mg/L, the concentration of the 6-azauracil was maintained at 3-4 mg/L, and the concentration of the methionine was maintained at 10-12 mg/L.

(21) The second palladium plating solution included palladium diammine dichloride, 3-chloro-4-fluoroaniline, calcium dinonylnaphthalene sulfonate and ?-cyano-L-alanine. During the electroplating process, in the second palladium plating solution, the concentration of palladium diammine dichloride was maintained at 7-8.5 g/L, the concentration of the 3-chloro-4-fluoroaniline was maintained at 8-10 mg/L, the concentration of the calcium dinonylnaphthalene sulfonate was maintained at 3-4 mg/L, and the concentration of the ?-cyano-L-alanine was maintained at 16-18 mg/L.

(22) Both the first gold plating solution and the second gold plating solution were potassium dicyanoaurate solution. The potassium dicyanoaurate in the first gold plating solution and the second gold plating solution was maintained at the concentration of 6-7 g/L. During the process of adjusting the first gold plating solution and the second gold plating solution by ammonia, both the first gold plating solution and the second gold plating solution had a pH of 12-13.

Example 4

(23) Comparing with Example 1, in this example, the temperature, current and period of electroplating, proportion and pH of each plating solution, and types of palladium salt were adjusted, and methionine was added into the first palladium plating solution.

(24) In this example, a bonding copper wire plated with palladium and gold was prepared, and the electroplating process for a bonding copper wire plated with palladium and gold includes:

(25) electroplating a first palladium layer on a surface of a copper wire with a first palladium plating solution, electroplating a second gold layer with a first gold plating solution to obtain a semi-finished product, electroplating a third palladium layer onto the semi-finished product with a second palladium plating solution, and electroplating a fourth gold layer with a second gold plating solution to obtain a finished product, i.e., the bonding copper wire plated with palladium and gold. The bonding copper wire plated with palladium and gold included a copper core wire, the first palladium layer, the second gold layer, the third palladium layer and the fourth gold layer arranged from inside to outside.

(26) The electroplating the first palladium layer, the electroplating the second gold layer, the electroplating the third palladium layer and the electroplating the fourth gold layer were performed at a temperature of 73 ?C, with an current of 60 mA, for a period of 25 min.

(27) The first palladium plating solution included tetraamminepalladium acetate, 4-sulfamoylbenzoic acid, 6-azauracil and methionine. During the electroplating process, in the first palladium plating solution, the concentration of the tetraamminepalladium acetate was maintained at 6-7 g/L, the concentration of the 4-sulfamoylbenzoic acid was maintained at 8-10 mg/L, the concentration of the 6-azauracil was maintained at 4-5 mg/L, and the concentration of the methionine was maintained at 18-20 mg/L.

(28) The second palladium plating solution included trans-dibromodiamminpalladium (II), 3-chloro-4-fluoroaniline, calcium dinonylnaphthalene sulfonate and ?-cyano-L-alanine. During the electroplating process, in the second palladium plating solution, the concentration of the trans-dibromodiamminpalladium (II) was maintained at 8-9 g/L, the concentration of the 3-chloro-4-fluoroaniline was maintained at 6-8 mg/L, the concentration of the calcium dinonylnaphthalene sulfonate was maintained at 5-6 mg/L, and the concentration of the ?-cyano-L-alanine was maintained at 20-22 mg/L.

(29) Both the first gold plating solution and the second gold plating solution were potassium dicyanoaurate solution. The potassium dicyanoaurate in the first gold plating solution and the second gold plating solution was maintained at the concentration of 7-8 g/L. During the process of adjusting the first gold plating solution and the second gold plating solution by ammonia, both the first gold plating solution and the second gold plating solution had a pH of 11-12.

Example 5

(30) Comparing with Example 1, in this example, the temperature, current and period of electroplating, proportion and pH of each plating solution, and types of palladium salt were adjusted, methionine was added into the first palladium plating solution, and twice of wire drawing processes were performed for copper wire plated layer.

(31) In this example, a bonding copper wire plated with palladium and gold was prepared, and the electroplating process for a bonding copper wire plated with palladium and gold includes:

(32) Selecting a copper wire with a diameter of 200 ?m, electroplating the first palladium layer on a surface of the copper wire with a first palladium plating solution, and electroplating a second gold layer with a first gold plating solution to obtain a semi-finished product; performing a first wire drawing to the semi-finished product, and the semi-finished product had a diameter of 97 ?m after the first wire drawing; then electroplating a third palladium layer on the semi-finished product with a second palladium plating solution, electroplating a fourth gold layer with a second gold plating solution to obtain the finished product, and performing a second wire drawing to the finished product, and the finished product had a diameter of 18 ?m after the second wire drawing. The obtained bonding copper wire plated with palladium and gold included the copper core wire, the first palladium layer, the second gold layer, the third palladium layer and the fourth gold layer arranged from inside to outside.

(33) The electroplating the first palladium layer, the electroplating the second gold layer, the electroplating the third palladium layer and the electroplating the fourth gold layer were performed at a temperature of 77 ?C, with an current of 35 mA, for a period of 30 min.

(34) The first palladium plating solution included tetraamminepalladium acetate, 4-sulfamoylbenzoic acid, 6-azauracil and methionine. During the electroplating process, in the first palladium plating solution, the concentration of the tetraamminepalladium acetate was maintained at 6-7 g/L, the concentration of the 4-sulfamoylbenzoic acid was maintained at 11-13 mg/L, the concentration of the 6-azauracil was maintained at 4-5 mg/L, and the concentration of the methionine was maintained at 14-16 mg/L.

(35) The second palladium plating solution included palladium diammine dichloride, 3-chloro-4-fluoroaniline, calcium dinonylnaphthalene sulfonate and ?-cyano-L-alanine. During the electroplating process, in the second palladium plating solution, the concentration of the palladium diammine dichloride was maintained at 6-7 g/L, the concentration of the 3-chloro-4-fluoroaniline was maintained at 10-12 mg/L, the concentration of the calcium dinonylnaphthalene sulfonate was maintained at 3-4.5 mg/L, and the concentration of the ?-cyano-L-alanine was maintained at 15-17 mg/L.

(36) Both the first gold plating solution and the second gold plating solution were potassium dicyanoaurate solution. The potassium dicyanoaurate in the first gold plating solution and the second gold plating solution was maintained at the concentration of 7-8 g/L. During the process of adjusting the first gold plating solution and the second gold plating solution by ammonia, both the first gold plating solution and the second gold plating solution had the pH of 12-13.

Comparative Example 1

(37) The technical solution of this comparative example is same as that of Example 1, except that the first palladium plating solution did not include the 4-sulfamoylbenzoic acid.

(38) In particular, the first palladium plating solution included tetraamminepalladium acetate and 6-azauracil. During the electroplating process, in the first palladium plating solution, the concentration of the tetraamminepalladium acetate was maintained at 7-8 g/L, and the concentration of the 6-azauracil was maintained at 1-2 mg/L.

(39) A bonding copper wire plated with palladium and gold was prepared.

Comparative Example 2

(40) The technical solution of this comparative example is same as that of Example 1, except that the first palladium plating solution did not include the 6-azauracil.

(41) In particular, the first palladium plating solution includes tetraamminepalladium acetate and 4-sulfamoylbenzoic acid. During the electroplating process, in the first palladium plating solution, the concentration of the tetraamminepalladium acetate was maintained at 7-8 g/L, and the concentration of the 4-sulfamoylbenzoic acid was maintained at 12-15 mg/L.

(42) A bonding copper wire plated with palladium and gold was prepared.

Comparative Example 3

(43) The technical solution of this comparative example is same as that of Example 1, except that the second palladium plating solution did not include the 3-chloro-4-fluoroaniline.

(44) In particular, the second palladium plating solution includes tetraamminepalladium(II) dichloride, calcium dinonylnaphthalene sulfonate and ?-cyano-L-alanine. During the electroplating process, in the second palladium plating solution, the concentration of the tetraamminepalladium(II) dichloride was maintained at 6-8 g/L, the concentration of the calcium dinonylnaphthalene sulfonate was maintained at 2-4 mg/L, and the concentration of the ?-cyano-L-alanine was maintained at 18-22 mg/L.

(45) A bonding copper wire plated with palladium and gold was prepared.

Comparative Example 4

(46) The technical solution of this comparative example is same as that of Example 1, except that the second palladium plating solution did not include the calcium dinonylnaphthalene sulfonate.

(47) In particular, the second palladium plating solution includes tetraamminepalladium(II) dichloride, 3-chloro-4-fluoroaniline and ?-cyano-L-alanine. During the electroplating process, in the second palladium plating solution, the concentration of the tetraamminepalladium(II) dichloride was maintained at 6-8 g/L, the concentration of the 3-chloro-4-fluoroaniline was maintained at 10-13 mg/L, and the concentration of the ?-cyano-L-alanine was maintained at 18-22 mg/L.

(48) A bonding copper wire plated with palladium and gold was prepared.

Comparative Example 5

(49) The technical solution of this comparative example is same as that of Example 1, except that the second palladium plating solution did not include the ?-cyano-L-alanine.

(50) In particular, the second palladium plating solution includes tetraamminepalladium(II) dichloride, 3-chloro-4-fluoroaniline and calcium dinonylnaphthalene sulfonate. During the electroplating process, in the second palladium plating solution, the concentration of the tetraamminepalladium(II) dichloride was maintained at 6-8 g/L, the concentration of the 3-chloro-4-fluoroaniline was maintained at 10-13 mg/L, and the concentration of the calcium dinonylnaphthalene sulfonate was maintained at 2-4 mg/L.

(51) A bonding copper wire plated with palladium and gold was prepared.

Comparative Example 6

(52) The technical solution of this comparative example is same as that of Example 1, except that the components of the first palladium plating solution and the second palladium plating solution are different from Example 1.

(53) The first palladium plating solution included tetraamminepalladium(II) dichloride, ethylenediamine (acting as a ligand) and sodium sulfate (enhancing the conductivity of the solution). During the electroplating process, the concentration of the tetraamminepalladium(II) dichloride was maintained at 7-8 g/L, the concentration of the ethylenediamine was maintained at 1-2 g/L, and the concentration of sodium sulfate was maintained at 5-6 g/L.

(54) The second palladium plating solution adopted in this comparative example has the same components as the first palladium plating solution.

(55) A bonding copper wire plated with palladium and gold was prepared.

Test Example 1

(56) The bonding copper wires plated with palladium and gold prepared in Examples 1-5 and Comparative examples 1-6 were tested with resistivity test and repeated bending tensile test. The results were shown in table 1.

(57) Table 1. Resistivity test and bending tensile test of the bonding copper wires plated with palladium and gold prepared in examples and comparative examples

(58) TABLE-US-00001 Repeating relative bending tensile test for 50 times, with a semicircle having Resistivity/ a diameter of 1 cm formed Appearance (10.sup.?8? .Math. m) at a bending part Example 1 Smooth and 1.7 No peeling and cracking bright surface of a plated layer at the bending part Example 2 Smooth and 1.8 No peeling and cracking bright surface of a plated layer at the bending part Example 3 Smooth and 1.7 No peeling and cracking bright surface of a plated layer at the bending part Example 4 Smooth and 1.6 No peeling and cracking bright surface of a plated layer at the bending part Example 5 Smooth and 1.7 No peeling and cracking bright surface of a plated layer at the bending part Comparative Slight speckles 1.9 Slight cracking of a plated example 1 layer at the bending part Comparative Slight bumps 1.8 Slight cracking of a plated example 2 layer at the bending part Comparative Slight dents 2.0 Slight cracking of a plated example 3 layer at the bending part Comparative Slight stripes 2.1 Slight cracking of a plated example 4 layer at the bending part Comparative slight powder 1.8 Slight cracking of a plated example 5 spots layer at the bending part Comparative Slight holes on 2.0 Slight cracking of a plated example 6 the surface layer at the bending part

(59) It can be seen from the results in table 1, the bonding copper wires plated with palladium and gold prepared in Examples 1-5 have a smooth and bright surface, lower resistivity and good bending resistance, which are better than the results of the Comparative examples 1-6. The reason is that, the uniformity of the plated layer, the fineness of deposited particles, and the like are affected by the components of the first palladium plating solution and the second palladium plating solution.

Test Example 2

(60) After the bonding wire is welded, the welded end is easy to be corroded to lose efficacy, and the welded end of the bonding wire is generally spherical shape or a flat disc shape. Therefore, the end of the bonding copper wires plated with palladium and gold prepared in Example 1 and Comparative example 6 were prepared as spherical shape, the spherical end is tested with an electrolytic corrosion test (corresponding to an accelerated corrosion test). The electrolytic corrosion test is performed by referring to Standard GB/T 6466-2008, and SEM images of the ends of the bonding wires after electrolytic corrosion test were shown in FIG. 1 and FIG. 2, respectively. FIG. 1 is a SEM image of a spherical end formed by a bonding copper wire plated with palladium and gold prepared in Example 1 after electrolytic corrosion. FIG. 2 is a SEM image of a spherical end formed by a bonding copper wire plated with palladium and gold prepared in Comparative example 6 after electrolytic corrosion.

(61) Comparing FIG. 1 with FIG. 2, the spherical end in FIG. 1 has less cracking after the accelerated corrosion test, and the spherical end in FIG. 2 has more cracking after the accelerated corrosion test. It can be known that, the bonding copper wires plated with palladium and gold prepared in Example 1 has a better corrosion resistance.

Test Example 3

(62) 11 identical copper sheets were taken to replace the copper wires of the Examples 1-5 and Comparative examples 1-6, which were used to prepare copper sheets plated with palladium and gold. 11 copper sheets plated with palladium and gold were tested with a surface coverage rate test, and results were shown in table 2.

(63) TABLE-US-00002 TABLE 2 Surface coverage rate test Surface coverage rate/% Example 1 99.4 Example 2 99.3 Example 3 99.7 Example 4 99.6 Example 5 99.2 Comparative 93.1 example 1 Comparative 92.3 example 2 Comparative 94.4 example 3 Comparative 96.8 example 4 Comparative 95.0 example 5 Comparative 93.2 example 6

(64) It can be seen from the results in table 2, the coverage rate of the plated layer prepared in Examples 1-5 can reach 99.2-99.7%, which are obviously greater than that of Comparative examples 1-6. In particular, the plated layer in Examples 3-4 have greater coverage rate, the reason is that, compared with Example 1, the first palladium plating solution includes the methionine, which further improves the coverage rate of the plated layer.

(65) In summary, the bonding copper wire plated with palladium and gold prepared by the technical solution of the present application has advantages of even plated layer, large coverage rate, smooth and bright surface, good corrosion resistance, and good bending resistance, and the plated layer is not easy to be peeled off, and has high reliability when it is applied in devices such as semiconductor, and the like.

(66) The above are the preferred embodiments of the present application, which are not intended to limit the protection scope of the present application. Therefore, all equivalent changes made according to the structure, shape and principle of the present application should fall within the protection scope of the present application.