Pretreatment solution for electroless plating and electroless plating method

Abstract

The pretreatment solution for electroless plating of the present invention is composed of noble metal colloidal nanoparticles, a sugar alcohol, and water. The colloidal nanoparticles are gold, platinum, or palladium, have an average particle diameter of 5 to 80 nm, and are contained in the pretreatment solution in an amount of 0.01 to 10 g/L as metal mass. The sugar alcohol is at least one selected from the group consisting of tritol, tetritol, pentitol, hexitol, heptitol, octitol, inositol, quercitol, or pentaerythritol and is contained in the pretreatment solution in an amount of 0.01 to 200 g/L in total. The electroless plating method of the present invention uses the pretreatment solution and performs the electroless plating in an electroless plating bath.

Claims

1. A pretreatment solution for electroless plating, comprising noble metal colloidal nanoparticles, a sugar alcohol, and water, wherein the colloidal nanoparticles are platinum nanoparticles, and have an average particle diameter of 5 to 80 nm, and are contained in the pretreatment solution in an amount of 0.01 to 10 g/L as metal mass; the sugar alcohol is at least one selected from the group consisting of glycerin, erythritol, xylitol, inositol, or pentaerythritol and is contained in the pretreatment solution in an amount of 0.01 to 200 g/L in total; and the remainder is water.

2. A pretreatment solution for electroless plating, comprising noble metal colloidal nanoparticles, a sugar alcohol, and water, wherein the colloidal nanoparticles are palladium, and have an average particle diameter of 5 to 80 nm, and are contained in the pretreatment solution in an amount of 0.01 to 10 g/L as metal mass; the sugar alcohol is at least one selected from the group consisting of glycerin, erythritol, xylitol, or mannitol and is contained in the pretreatment solution in an amount of 0.01 to 200 g/L in total; and the remainder is water.

3. A pretreatment solution for electroless plating, comprising noble metal colloidal nanoparticles, a sugar alcohol, and water, wherein the colloidal nanoparticles are gold, and have an average particle diameter of 5 to 80 nm, and are contained in the pretreatment solution in an amount of 0.01 to 10 g/L as metal mass; the sugar alcohol is at least one selected from the group consisting of glycerin, erythritol, xylitol, mannitol, or pentaerythritol and is contained in the pretreatment solution in an amount of 0.01 to 200 g/L in total; and the remainder is water.

Description

BRIEF DESCRIPTION OF DRAWING

(1) The FIGURE shows a transmission electron microscope photograph of gold (Au) nanoparticles having a particle diameter of 20 nm according to the present invention.

EXAMPLES

(2) Preferred examples of the present invention will now be described.

[1] Preparation of Pretreatment Solution

Example 1

(3) Sodium tetrachloroaurate(III) tetrahydrate (0.1 g/L in terms of concentration of gold (Au)) and xylitol (1.0 g/L) were dissolved in an aqueous sodium hydroxide solution (pH: 12) at 90 C. The solution was reduced with trisodium citrate dihydrate to prepare a gold (Au) colloid solution. The gold (Au) nanoparticles had an average particle diameter of 20 nm, and 90% or more of the nanoparticles had a particle diameter in the range of 10 to 30 nm (d=2010 nm). Gold (Au) nanoparticles having a particle diameter of 20 nm were inspected with a transmission electron microscope (JEM-2010, manufactured by JEOL Ltd.). The transmission electron microscope photograph is shown in the FIGURE. As obvious from this photograph, picoclusters were in a size similar to the atomic-level size of gold (Au) and were self-aligned at equal intervals on the surfaces of the gold (Au) nanoparticles.

(4) Subsequently, the resulting gold (Au) colloid solution was dispersed in an aqueous solution of 1N hydrochloric acid, sulfuric acid, or potassium hydroxide at 80 C. A transmission electron microscope photograph of each dispersion was similarly inspected, and no change in the surface property of the gold (Au) nanoparticles was observed. Separately, the gold (Au) colloid solution was dispersed in an aqueous sodium hydroxide solution (pH: 12) at 30 C. Even after 150 hours, similarly, no change in the surface property of the gold (Au) nanoparticles was observed.

Example 2

(5) Gold (Au) colloid solutions were prepared as in Example 1, except that the amount of the sodium tetrachloroaurate(III) tetrahydrate was 1 g/L, 5 g/L, or 9 g/L in terms of concentration of gold (Au) and the amount of the xylitol was 15 g/L, 0.5 g/L, or 150 g/L, respectively. The resulting gold (Au) nanoparticles had a particle diameter d of 2010 nm, 3010 nm, and 5020 nm, respectively, for the amounts of 1 g/L, 5 g/L, and 9 g/L in terms of concentration of gold (Au).

Example 3

(6) The same experiment as Example 1 was carried out using mannitol, glycerin, or erythritol instead of xylitol to prepare gold (Au) colloidal nanoparticles respectively having a particle diameter d of 2010 nm, 2010 nm, and 2010 nm. The resulting gold (Au) colloid solutions were each dispersed in an aqueous solution of 1N hydrochloric acid, sulfuric acid, or potassium hydroxide at 80 C., as in Example 1. No change in the surface property of the gold (Au) nanoparticles was observed, as in Example 1.

Example 4

(7) Palladium chloride (0.1 g/L in terms of concentration of palladium (Pd)) and glycerin (50 g/L) were dissolved in an aqueous hydrochloric acid solution (pH: 3) at 90 C. The solution was reduced with sodium hypophosphite to prepare a palladium (Pd) colloid solution. The palladium (Pd) nanoparticles had a particle diameter d of 3010 nm.

(8) Subsequently, the resulting palladium (Pd) colloid solution was dispersed in an aqueous solution of 1N hydrochloric acid, sulfuric acid, or potassium hydroxide at 80 C. No change in the surface property of the palladium (Pd) nanoparticles was observed, as in Example 1.

Example 5

(9) palladium (Pd) colloid solutions were prepared as in Example 4, except that the amount of the palladium chloride was 1 g/L, 5 g/L, or 9 g/L in terms of concentration of palladium (Pd) and the amount of the glycerin was 0.05 g/L, 4 g/L, or 18 g/L, respectively. The resulting palladium (Pd) nanoparticles had a particle diameter d of 5020 nm, 3010 nm, and 3010 nm, respectively, for the amounts of 1 g/L, 5 g/L, and 9 g/L in terms of concentration of palladium (Pd).

Example 6

(10) The same experiment as Example 4 was carried out using mannitol, xylitol, or erythritol instead of glycerin to prepare palladium (Pd) colloidal nanoparticles respectively having a particle diameter d of 3010 nm, 4010 nm, and 3010 nm. The resulting palladium (Pd) colloid solutions were each dispersed in an aqueous solution of 1N hydrochloric acid, sulfuric acid, or potassium hydroxide at 80 C., as in Example 4. No change in the surface property of the palladium (Pd) nanoparticles was observed, as in Example 4.

Example 7

(11) Hexahydroxoplatinic(IV) acid (0.3 g/L in terms of concentration of platinum (Pt)) and xylitol (1.5 g/L) were dissolved in an aqueous potassium hydroxide solution (pH: 12) at 90 C. The solution was reduced with hydrazine to prepare a platinum (Pt) colloid solution. The platinum (Pt) nanoparticles had a particle diameter d of 3010 nm. Platinum (Pt) nanoparticles having a particle diameter of 30 nm were inspected with a transmission electron microscope. Picoclusters were in a size similar to the atomic-level size of platinum (Pt) and were self-aligned at equal intervals on the surfaces of the platinum (Pt) nanoparticles.

(12) Subsequently, the resulting platinum (Pt) colloid solution was dispersed in an aqueous solution of 1N hydrochloric acid, sulfuric acid, or potassium hydroxide at 80 C. Similarly, the transmission electron microscope photograph was inspected, and no change in the surface property of the platinum (Pt) nanoparticles was observed.

Example 8

(13) Platinum (Pt) nanoparticles were prepared as in Example 7, except that the amount of the hexahydroxoplatinic(IV) acid was 1.5 g/L, 5 g/L, or 6.5 g/L in terms of concentration of platinum (Pt) and the amount of the xylitol was 4 g/L, 180 g/L, or 16 g/L, respectively. The resulting platinum (Pt) nanoparticles had a particle diameter d of 3010 nm, 5020 nm, and 3010 nm, respectively, for the amounts of 1.5 g/L, 5 g/L, and 6.5 g/L in terms of concentration of platinum (Pt).

Example 9

(14) The same experiment as Example 1 was carried out using sorbitol, mannitol, erythritol, glycerin, or inositol instead of xylitol to prepare platinum (Pt) colloidal nanoparticles respectively having a particle diameter d of 3010 nm, 6010 nm, 2010 nm, 6010 nm, and 8010 nm. The resulting platinum (Pt) colloid solutions were each dispersed in an aqueous solution of 1N hydrochloric acid, sulfuric acid, or potassium hydroxide at 80 C., as in Example 7. No change in the surface property of the platinum (Pt) nanoparticles was observed, as in Example 7.

[2] Electroless Plating

Example 10

(15) A 2020 mm square silicon wafer test piece having a surface provided with SiO.sub.2 was subjected to chemical vapor deposition using a silane coupling agent (3-aminopropyl triethoxysilane (trade name: KBE-903)) manufactured by Shin-Etsu Chemical Co., Ltd. under an atmospheric pressure at 75 C. for 5 minutes to form a self-assembled monolayer (SAM) having amine terminal groups, which was used as a substrate.

(16) Twenty of the substrates were immersed in 1000 mL of the gold (Au) colloid solution prepared in Example 1 at 25 C. for 10 minutes. The substrates were each washed with distilled water for 10 minutes. The substrates were then immersed one by one in an auto-catalytic non-cyan electroless gold plating bath (trade name: PRECIOUSFAB ACG 3000WX, gold (Au) concentration: 2 g/L, pH: 7.5) manufactured by Electroplating Engineering of Japan Ltd. at 65 C. for 5 minutes. All of the 20 substrates were plated without causing runaway of the electroless gold plating bath during the plating.

(17) The plating thickness of the resulting gold (Au) plating was measured with a fluorescent X-ray thickness meter (model: SFT-9550) manufactured by Hitachi High-Tech Science Corporation. The average plating thickness of the 20 substrates was 505 nm.

Example 11

(18) Ten -alumina substrates having a size of 5050 mm and a thickness of 1 mm were immersed in 1000 mL of the platinum (Pt) colloid solution prepared in Example 7 at 25 C. for 10 minutes. The substrates were each washed with distilled water for 30 minutes. The substrates were then immersed one by one in an electroless platinum plating bath containing 3.4 g/L of dinitro diamino platinum(II) (Pt(NH.sub.3).sub.2(NO.sub.2).sub.2), 2 mol/Pt mol of polyvinylpyrrolidone, and 1.0 g/L of potassium borohydride (KBH.sub.4) and having a pH of 12 at a bath temperature of 90 C. for 30 minutes. All of the 10 substrates were plated without causing runaway of the electroless platinum plating bath during the plating.

(19) The average plating thickness of the resulting platinum (Pt) plating was 10.3 m, and the variation in thickness was low to give uniform films.

Example 12

(20) Twenty gold test pieces having a size of 6030 mm and a thickness of 0.3 mm were immersed in 500 mL of the palladium (Pd) colloid solution prepared in Example 4. The substrates were each washed with flowing water for 10 minutes and were then immersed one by one in an electroless nickel plating bath (trade name: Lectroless NP7600, nickel (Ni) concentration: 4.8 g/L, pH: 4.6) manufactured by Electroplating Engineering of Japan Ltd. at 85 C. for 20 minutes. All of the 20 substrates were plated without causing runaway of the electroless nickel plating bath during the plating.

(21) The plating thickness of the resulting nickel (Ni) plating was measured with a fluorescent X-ray thickness meter (model: SFT-9550) manufactured by Hitachi High-Tech Science Corporation. The average plating thickness of the 20 substrates was 1.00.2 m, and the variation in thickness was low to give uniform films.

Comparative Example 1

(22) A gold (Au) colloid solution was prepared as in Example 1 except that the amount of sodium tetrachloroaurate(III) tetrahydrate was 12 g/L in terms of concentration of gold (Au). The gold (Au) nanoparticles had a particle diameter d of 8050 nm. This gold (Au) colloid solution started to aggregate at about 1 hour after the preparation and did not show an activity as a catalytic nucleus for electroless plating.

Comparative Example 2

(23) A gold (Au) colloid solution was prepared as in Example 1 except that the amount of sodium tetrachloroaurate(III) tetrahydrate was 0.005 g/L in terms of concentration of gold (Au). The gold (Au) nanoparticles had a particle diameter d of 4020 nm, and no picocluster was observed on the surfaces of the gold (Au) nanoparticles. This gold (Au) colloid solution was electroless plated in the bath of Example 10, but no electroless plating was operated.

Comparative Example 3

(24) A palladium (Pd) colloid solution was prepared as in Example 4 except that the amount of glycerin was 250 g/L. The palladium (Pd) nanoparticles had a particle diameter d of 4020 nm, and no picocluster was observed on the surfaces of the palladium (Pd) nanoparticles. This palladium (Pd) colloid solution was electroless plated in the bath of Example 12, but no electroless plating was operated.

Comparative Example 4

(25) A platinum (Pt) colloid solution was prepared as in Example 7 except that the amount of xylitol was 0.005 g/L. The platinum (Pt) nanoparticles had a particle diameter d of 2040 nm, and no picocluster was observed on the surfaces of the platinum (Pt) nanoparticles. This platinum (Pt) colloid solution was electroless plated in the bath of Example 11, but no electroless plating was operated.

Conventional Example 1

(26) An aqueous solution containing polyvinylpyrrolidone K25 (0.05 g/L), tetrachloroaurate(III) tetrahydrate (0.1 g/L in terms of concentration of Au), and sodium citrate dihydrate (0.5 g/L) was stirred at 90 C. for 30 minutes to prepare an Au colloid containing polyvinylpyrrolidone as a dispersant. This Au colloid solution was subjected to electroless gold plating as in Example 10, but no electroless plating was operated.

INDUSTRIAL APPLICABILITY

(27) The pretreatment solution for electroless plating of the present invention can be applied to every commercially available electroless plating solution. The electroless plating method can be applied to, for example, a variety of sensors, such as an optical sensor, a hydrogen gas detection sensor, an air pressure sensor, and a water depth sensor, and electrodes of wiring substrates.