JP3167456B2 - Composite plating method by electroless gold plating - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite plating method by electroless gold plating which can obtain a composite plating in which a fine fluororesin is eutectoid uniformly in a gold matrix in a high eutectoid amount.

[0002]

2. Description of the Related Art Composite plating, in which fine particles and fibrous materials such as metals and inorganic and organic compounds are dispersed and eutectoid in a metal matrix formed by electrolytic plating or electroless plating, is based on the properties of the metal matrix that constitutes it. It has the function of combining the properties of different eutectoids.

Therefore, for the purpose of improving corrosion resistance, abrasion resistance, lubricity, etc., and beautifying the appearance, etc., a metal matrix and an eutectoid material suitable for the purpose are selected, and many proposals have been made. ing.

[0004] If gold-fluorine resin composite plating can be obtained, plastic and rubber molds that take advantage of the properties of gold and fluorine resin, such as corrosion resistance, chemical resistance, high electrical conductivity, and water repellency, respectively, can be obtained. It is thought that it can be applied to metal molds, medical devices, water repellent catalysts, and many other applications.

[0005] However, gold-plated substrates require relays, switches, and switches that require corrosion resistance and high conductivity.
Although it is used for electrical contact parts such as contacts and connectors, it is expensive and known to eutect inorganic particles (for example, Japanese Patent Publication No. 59-15098). It is also known to use a polymer to improve the properties of the conductor surface (for example, JP-A-48-28332), but gold-fluorine resin composite plating is not known.

[0006]

[Problems to be solved by the invention]
Japanese Patent Application Publication No. 150098 discloses hard inorganic particles such as WC and TiC or MoS _{2 in} a metal matrix such as gold.
JP-A-48-28332 discloses that a polymer matrix such as natural or synthetic rubber latex is codeposited on a metal matrix such as copper or nickel. In this example, an example of composite plating of nickel-Teflon is shown, and it is not that a fluororesin is codeposited on a gold matrix.

[0007] This is because a commonly used gold plating bath is provided with a PT used for Ni-PTFE composite plating.
In most cases, when a fluororesin such as FE dispersion is added, PTFE fine particles are aggregated and settle, and are not dispersed in the plating bath or even if they are eutectoid, PTFE particles remain in the plating layer. Uneven and
This is probably because only a very small amount of eutectoid film can be obtained.

An object of the present invention is to provide a method capable of forming a composite plating layer in which a fluorine resin is uniformly dispersed at a high eutectoid amount in a gold matrix.

[0009]

Means for Solving the Problems The present inventor has conducted intensive studies on the electroless gold plating method in order to solve the above-mentioned problems and achieve the above-mentioned object. The inventors have found that the object can be achieved by using an electroless gold plating bath having a self-catalyst thickening type, and have completed the present invention. That is, the present invention provides a conductive salt concentration of 15
0 g / l or less, gold salt concentration of 20 g / l or less as gold,
This is a composite plating method by electroless gold plating in which an electroless plating treatment is performed using an autocatalytic thickening type electroless gold cyan plating bath to which a fine fluororesin is added to form a gold plating layer containing the fluororesin dispersed therein. .

[0010] The gold plating bath in the present invention includes DM
An autocatalytic thickening type electroless plating bath having a conductive salt concentration of 150 g / l or less and a gold salt concentration of 20 g / l or less as gold using AB or a borohydride compound or thiourea as a reducing agent. Can be

The fluororesin may be selected from PTFE, FEP and other fluororesins depending on the intended use. As PTFE, a composite plating dispersion commercially available for Ni-PTFE composite plating, a commercially available PTFE dispersion generally used for other applications (for example, 30-J (trade name) manufactured by DuPont), Daikin D-1 and D-2 (all trade names) manufactured by Kogyo Co., Ltd., or FEP dispersion (for example, 120-J (trade name) manufactured by DuPont), etc. Further, fluororesin powder (for example, PTFE) Then
DuPont MP-1100, MP-1125, TLP
-10M (all trade names), L-170 manufactured by Asahi Glass Co., Ltd.
J, L-172J, L-173J (all are trade names),
Examples of the FEP include Aflon PFA (trade name) manufactured by Asahi Glass Co., Ltd., and it is also preferable to use a gel that has been subjected to a pretreatment for solubilization. A commercially available fluororesin emulsion can also be used after pretreatment.

[0012]

The plating bath as described above (for example, potassium (I) cyanide or potassium (III) cyanide (as gold) 1.0 to 6.0 g / l, potassium hydroxide 5)
~ 35 g / l, potassium cyanide 0.5-10 g / l,
DMAB 4 to 6 g / l), a surfactant such as a fluorine-based amphoteric surfactant is added in an amount of 20 ml / l or less, and a fluororesin dispersion is added in an amount of 20 ml / l or less.
It is preferable to perform an electroless plating process.

The reason that the concentration of the conductive salt in the gold plating bath is 150 g / l or less and the concentration of the gold salt is 20 g / l or less in terms of gold is that the dispersibility of the fluororesin decreases due to the electroless addition due to the nature of the surfactant. The apparent particle size increases due to aggregation,
It is thought that it is separated from the aqueous solution by the relationship of Stokes formula, and regardless of the presence or absence of forced dispersing means such as stirring, if these limits are exceeded , high eutectoid amount of fluororesin, uniform distribution cannot be obtained Because. Further, in order to improve dispersibility, it is conceivable to add a surfactant such as a fluorine-based amphoteric surfactant, but an excessive addition is not preferable because it adversely affects the amount of eutectoid.

In this electroless plating method, the deposition rate and the fluorine resin eutectoid amount are usually reduced by repeatedly using the plating bath two or more times. The deposition rate of the plating film is kept constant by replenishing the reducing agent in excess of the consumption amount, that is, by replenishing 1.3 ⁿ times the consumption amount (n = the number of repetitions when the film thickness is 2 μm is defined as one time). Can be In addition, it was confirmed that the decrease in the eutectoid amount was caused by an increase in the cyanide concentration with respect to the decrease in the eutectoid amount of the fluororesin. Instead of using a gold (I) sulfite (for example, an alkali metal salt, or an ammonium salt) as a gold salt having the same valence as gold, it is possible to control the decrease in the eutectoid amount of the fluororesin and to decrease the deposition rate. It can be suppressed. Also, as a method of controlling the amount of eutectoid fluorocarbon,
By adding 0.2 ml / l or less of a nonionic surfactant represented by perfluoroalkylamine oxide, it is possible to control the eutectoid content of the fluororesin to 35% by volume or less.

In addition to DMAB as a reducing agent, a reducing agent exhibiting an autocatalytic reduction reaction such as borohydride or thiourea, or a gold (I) sulfite or a gold (III) chloride as a gold salt at the time of building bath. ) When an acid salt or the like is used, eutectoid of the fluororesin is recognized, but it is recognized that the deposition rate is low and that the plating bath is easily decomposed or abnormally precipitated.

[0016]

Next, an embodiment of the present invention will be described. Example 1 Using gold (I) cyanide as gold, 3 g / l, potassium hydroxide 45 g / l, potassium cyanide 2.3 g / l,
DMAB 4.0 g / l, potassium carbonate 100 g / l, triethanolamine 15 g / l, lead acetate 0.03 g / l
A commercially available fluororesin dispersion for composite plating was added at 10 ml / l using a self-catalyzed thick electroless gold plating solution having DMAB having a composition as described above as a reducing agent, and a solution temperature of 72 ° C. and a liquid load of 1. The electroless plating was performed at 0 dm ² / l.

As a result, the deposition rate of the film is 2 μm / h
r, the eutectoid content of the fluororesin was 25% by volume, and a uniformly dispersed plating layer was obtained. Example 2 1) Pretreatment of Fluororesin Dispersion PTFE dispersion (fluorine resin having a particle size of 0.1 to 0.2 μm is nonionic, anionic, or amphoteric) is generally used as a commercially available fluororesin dispersion. (D-2 manufactured by Daikin Industries, Ltd.) and pure 80
ml and perfluoroalkyl quaternary ammonium iodide (cationic surfactant: FC-135 manufactured by 3M)
Add 0.5 ml and stir well. This was centrifuged at 3500 rpm. p. m. After centrifugation for 30 minutes at, the supernatant liquid is separated from the gelled and precipitated fluororesin. 0.5 ml of the above-mentioned cationic surfactant is added to this fluororesin, and pure water is added to make 30 ml, and the mixture is stirred well and stored.

2) Plating treatment A commercially available autocatalytic thickening type electroless gold plating solution (OPC manufactured by Okuno Pharmaceutical Co., Ltd.)
Using Muden Gold 25), add 12 ml / l of the dispersion prepared in 1) as a fluororesin,
1.0 ml / l of -131 (a surfactant manufactured by Asahi Glass Co., Ltd.)
1.0 ml / l of FC-135 (a surfactant manufactured by 3M) was added, and electroless plating was performed at a liquid temperature of 74 ° C and a liquid load of 1.0 dm ² / l.

As a result, the deposition rate of the film was 10 μm /
hr and a uniformly dispersed composite plating layer having a fluorine resin eutectoid amount of 15% by volume was obtained. Example 3 As a result of treating in the same manner as in Example 2 except that GOBEL-2MN manufactured by Uemura Kogyo Co., Ltd. was used as a commercially available autocatalyst thickening type electroless gold plating solution and the solution temperature was 65 ° C., the deposition rate of the film was It was 1.2 μm / hr, and a fluororesin eutectoid amount of 28% by volume (35% by volume at maximum) was obtained as a uniformly dispersed composite plating layer. Example 4 A commercially available autocatalytic thickening type electroless gold plating solution made by Nippon Electroplating Engineers, Inc., Rectress 3G (3 g / l of gold (I) potassium cyanide as gold)
Addition) and the same treatment as in Example 2 except that the liquid temperature was 74 ° C. As a result, the deposition rate of the film was 1.4 μm / hr, and the eutectoid amount of the fluororesin was 28% by volume ( Up to 3
5% by volume) of a uniformly dispersed composite plating layer. Example 5 In a process similar to that of Example 1, Example 3, or Example 4, the amount of DMAB as a reducing agent was 1.3 ⁿ times the consumption every two hours (n: 2 hours as one unit). The number of repetitions of the process is repeated, and gold (I) sodium sulfite is supplied as a gold salt for the consumption amount, and the plating treatment is continuously performed while supplying the fluororesin dispersion for the consumption amount, and 1.2 turns (turns) : The gold content in the plating solution at the time of bathing is 1
As a result, the film formation rate and the eutectoid amount of the fluororesin could maintain the initial performance. Comparative Example 1 As a result of performing the same plating treatment as in Example 5 except that DMAB as a reducing agent was replenished every 2 hours for the consumption amount,
The formation rate of the film after 1.2 turns was reduced to 20% of the initial value. Comparative Example 2 As a result of performing the same plating treatment as in Example 5 except that potassium (I) cyanide was used as a gold salt for replenishing consumed gold, the eutectoid amount of the fluororesin after 1.2 turns was initially small. A reduction of the value to 12% was observed.

[0020]

The present invention uses a self-catalytic thickening type electroless gold plating bath having a specific conductive salt concentration and a gold salt concentration. A uniformly dispersed composite plating layer was obtained, and an extremely excellent effect was observed.

Claims (1)

(57) [Claims] A conductive salt concentration of 150 g / l or less, a gold salt concentration
Add fine fluororesin with a degree of gold of 20 g / l or less
A composite plating method based on electroless gold plating, wherein an electroless plating treatment is performed using a self-catalyzed thick electroless gold cyan plating bath to form a gold plating layer containing the fluororesin dispersed therein.