Surface treatment solutions for gold and gold alloys

Abstract

A composition containing a cationic polymer obtained from a reaction product of nitrogen-containing heterocyclic compound and epihalohydrin; and a phosphorus compound. The composition can be used as a surface treatment for gold or gold alloy. The composition can seal pinholes on the surface of the gold or gold alloy.

Claims

1. A surface treatment method for gold or gold alloy comprising: a) providing a copper or copper alloy-made electronic component, b) nickel plating the copper or copper alloy-made electronic component, c) gold or gold alloy plating the nickel, and d) contacting a surface of the gold or the gold alloy with an aqueous solution consisting of a cationic polymer, wherein the cationic polymer comprises a reaction product of a nitrogen-containing heterocyclic compound and epihalohydrin, a phosphorus compound, water, and optionally a pH adjuster and a wetting agent, to seal pinholes in the gold or gold alloy.

2. The surface treatment method of claim 1, wherein the phosphorus compound is selected from the group consisting of phosphoric acids, polyphosphoric acids and salts thereof and phosphate esters.

3. The surface treatment method of claim 1, wherein the cationic polymer is in amounts of 0.01 to 70 g/L, and the phosphorus compound is in amounts of 0.01 to 50 g/L.

4. The surface treatment method of claim 3, wherein the cationic polymer is in amounts of 1 to 20 g/L.

5. The surface treatment method of claim 3, wherein the phosphorus compound is in amounts of 10 to 30 g/L.

6. The surface treatment method of claim 1, wherein a pH of the aqueous solution is from 6-12.

7. The surface treatment method of claim 6, wherein the pH of the aqueous solution is from 8-12.

8. The surface treatment method of claim 1, wherein the nitrogen-containing heterocyclic compound is chosen from imidazole or pyridine.

9. The surface treatment method of claim 1, wherein the epihalohydrin is chosen from epihalohydrin or epibromohydrin.

10. The surface treatment method of claim 1, wherein the surface treatment with the aqueous solution is done without performing electrolysis.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) As used throughout the specification C. is degree Celsius, g/L is grams per liter, ml/L is milliliters per liter, m is micrometer, m/min is meters per minute, and A/dm.sup.2 and ASD are Amperes per square decimeter.

(2) The present invention pertains to a surface treatment agent made of a composition containing a cationic polymer which is a reaction product obtained from a nitrogen-containing heterocyclic compound and epihalohydrin; and a phosphorus compound. Examples of the nitrogen-containing heterocyclic compounds include imidazole and pyridine. Halogens of epihalohydrins include fluoro, chloro, bromo or iodo. Examples of epihalohydrins include epichlorohydrin and epibromohydrin. Examples of the cationic polymer obtained by reacting nitrogen-containing heterocyclic compounds with epihalohydrins include those obtained by dissolving and reacting imidazole and epichlorohydrin at a desired concentration in the same solvent; however, commercially available products may also be used. Examples of commercially available products include RALUPLATE IME manufactured by Raschig chemicals (product name) (CAS No.: 68797-57-9). The content of the cationic polymer obtained by reacting nitrogen-containing heterocyclic compounds with epihalohydrins in the composition is from 0.01 to 70 g/L, preferably from 1 to 20 g/L.

(3) The composition of the preset invention uses a cationic polymer obtained by reacting nitrogen-containing heterocyclic compounds and epihalohydrins; and a phosphorous compound in a mixture. The phosphorous compounds include phosphoric acids, polyphosphoric acids and salts thereof, and phosphate esters, preferably at least one kind selected from these. Here, the polyphosphoric acid is obtained by dehydration condensation of two or more phosphoric acids. The polyphosphoric acid includes metaphosphoric acid and tri-polyphosphoric acid. The salts of phosphoric acids and polyphosphoric acids refer to inorganic or organic salts of these acids. Examples thereof include sodium, potassium, ammonium, and guanidine salts. Phosphate esters are obtained by substituting a hydrogen atom of at least one hydroxyl group of phosphoric acid by (C.sub.1 to C.sub.6) alkyl. Examples include phosphoric acid trimethyl, phosphoric acid triethyl, and the like. The content of the phosphorous compound in the composition is from 0.01 to 50 g/L, preferably from 10 to 30 g/L.

(4) The composition of the present invention can also contain a pH adjuster, a wetting agent as optional components. The composition of the present invention also uses water as the solvent; preferably deionized water can be used. The pH of the composition of the present invention is from 6 to 12, preferably from 8 to 12.

(5) The composition of the present invention can be used as a surface treatment agent for gold or gold alloys. More preferably, it is used as a sealing agent for gold or gold alloy to prevent corrosion by covering the pinholes developed on the gold or gold alloys.

(6) In performing surface treatment for gold or gold alloys with the sealing agent of the present invention, as described above, the copper or copper alloy-made electronic components, which are generally subjected to the nickel plating as the base plating followed by gold or gold alloy plating on the nickel plating, are used as the processed material. The composition of the present invention is adjusted to 20 to 80 C., preferably 30 to 60 C. The processed material is brought into contact with the above composition for 0.1 seconds to 5 minutes, preferably for 1 second to 1 minute. Contact may be established by dipping, spraying, or other such methods. It is then preferably washed for 1 to 60 seconds with deionized water and dried.

(7) The compositions of the present invention are suitable for the surface treatment agent for electronic equipment and electronic components having gold or gold alloy plating film on its surface; preferably, it can be used as the surface treatment agent for the gold or gold alloy plating film formed on the connection terminal surface of the electronic components. For example, the composition can be used as the surface treatment agent for the gold or gold alloy plating film formed on the surface of the electrode terminals of semiconductor elements, connectors to connect electronic equipment, and the like. For gold or gold alloy plating, a hard gold plating solution is usually used, for example, gold cobalt alloy plating, gold nickel alloy plating, and the like.

(8) Hereinafter, the present invention will be explained with reference to the Examples; however, the present invention is not limited to these Examples.

EXAMPLE 1

(9) The electronic components (copper alloy 194) of copper material subjected to nickel electroplating (coating thickness of 2 microns) followed by gold electroplating (coating thickness of 0.026 microns) were used as the test sample. The composition 1 of the following composition was adjusted to 45 C., and the test sample was immersed for 5 seconds, and the surface treatment was performed. The test sample was then rinsed with deionized water and dried with air knife and hot air.

(10) Composition 1

(11) Cationic polymer obtained from imidazole and epichlorohydrin (Product name: RALU PLATE IME manufactured by Raschig Chemicals): 20 g/L Sodium polyphosphate (manufactured by Taihei Chemical Industrial Co., Ltd.): 20 g/L Remaining part: Water Corrosion Test Neutral salt spray test (NSS test) Conditions Spray solution: 5% sodium chloride aqueous solution Temperature: 34 to 36 C. pH: 6.5 to 7.2 Spray amount: Horizontal collecting area 0.5 to 3.0 ml/h per 80 cm.sup.2 Spray time: 48 hours or 72 hours Spray angle: 20 degrees to the vertical line Evaluation method: A state of corrosion developed on the surface of the test sample after an elapse of predetermined time was checked with the naked eye and rank was given according to the following criteria. Then, groove-like corrosion was counted with a microscope of 10 times. Evaluation criteria Level 0: No corrosion Level 1: About 1 to 9% of the area of the test sample surface is corroded Level 2: About 10 to 29% of the area of the test sample surface is corroded Level 3: About 30 to 49% of the area of the test sample surface is corroded Level 4: About 50% or more of the area of the test sample surface is corroded

Examples 2-3, Comparative Examples 1 to 8

(12) Operation was performed in the same manner as in Example 1 except the concentration of the composition was changed to the composition as described in Table 1 to 3, to assess the degree of corrosion. Results are shown in Table 1 to 3.

(13) TABLE-US-00001 TABLE 1 Example Type Compound Name 1 2 3 Cationic IME 20 g/L 20 g/L 20 g/L polymer Phosphorous Sodium 20 g/L compound polyphosphate Sodium 20 g/L tripolyphosphate Guanidine phosphate 20 g/L After 48 Corrosion level 0 0 0 hours Corrosion number 0 0 After 72 Corrosion level 0 0 1 hours Corrosion number 5 4

(14) TABLE-US-00002 TABLE 2 Comparative Example Type Compound Name 1 2 3 4 Cationic polymer Phosphorous compound Others Benzotriazole 1 g/L Mercaptosuccinic 15 g/L acid Picolinic acid 1 g/L After 48 Corrosion level 3 4 4 4 hours Corrosion number 200 or 50 or 42 100 or above above above After 72 Corrosion level 4 hours Corrosion number 200 or above

(15) TABLE-US-00003 TABLE 3 Comparative Example Type Compound Name 5 6 7 8 Cationic IME 20 g/L 20 g/L polymer H.C. polymer*.sup.1 20 g/L Phosphorous Sodium 20 g/L 20 g/L compound polyphosphate Others Sorbitan 1 g/L monostearate (Solgen 40) Polyethylene glycol 1 g/L (PEG 35000) Polyoxyethylene 20 g/L sorbitan monostearate (Solgen TW 60) After 48 Corrosion level 4 4 4 3 hours Corrosion number 100 or 100 or above above After 72 Corrosion level hours Corrosion number *.sup.1Copolymer of N-pyrrolidone and N-dimethylaminoethyl methacrylate diethyl sulfonate, manufactured by Osaka Organic Chemical Co., Ltd.