JPS596365A - Electroless gold plating method - Google Patents

Abstract

PURPOSE:To obtain high purity gold plating excellent in bonding characteristics and roller characteristics, by using a gold plating bath consisting of potassium gold cyanide, a complex compound comprising an org. acid (salts), a reducing agent and NH4Cl with respect to the surface of a member to which Ni plating is applied to apply electroless gold plating thereto. CONSTITUTION:High purity gold is applied to the surface of a member subjected to heat treatment after Ni plating or Ni plating containing B is applied thereto or a member to which gold flash plating is applied by electroless gold plating as mentioned hereinbelow. That is, an electroless gold plating bath with a pH of 4-7 containing potassium gold cyanide, sodium citrate, hydrazine hydrate, citric acid (Na salt) and NH4Cl is used with respect to the surface of the aforementioned member while slowly stirred at 45-50 deg.C to precepitate an electroless gold plating layer with a desired thickness. This gold plating layer can be made thick at a speed of about 0.5-1.0m/hr. In the next step, the plated member is heated to 200-300 deg.C after washing and drying, and heat treatment for recrystallizing gold is applied to form an electroless gold plating film.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an electroless gold plating method, and more particularly to an electroless gold plating method that allows high-purity gold plating to be performed on a member to be plated. It is.

[Technical background of the invention and its problems]

For example, a single IC, an envelope used for multiple ICs, L8
When manufacturing so-called electronic component envelopes such as semiconductor envelopes such as I envelopes and envelopes for surface wave devices, tungsten, molybdenum, and their alloys are placed on an insulating substrate made of ceramics, alumina, etc. Metal powder is made into a paste and applied to a portion using printing technology, and then heated and sintered together with an insulating substrate to form a conductor part, and a gold layer is deposited on this conductor part by plating. A known method is to use it for wiring and connection with a metal lid. In this case, after performing nickel plating obtained by ordinary electrolytic plating or electroless plating, nickel plating containing boron, etc. on the conductor part, the parts are treated in a hydrogen furnace, or the parts are treated with 111/l sodium hydroxide 1001/l sodium hydroxide. /l sodium citrate 100
y/l solution for about 5 minutes at 95°C, and on a member that had been flushed by about 0.1 μm with a normal electrolytic gold plating solution, 211/l cyanogen-gold potassium was deposited.
Ammonium chloride 75g/l, sodium oxalate 5
0 g/l and sodium hypophosphite 1 ott/l. An electroless gold plating film is formed at 90-95°C using a plating solution with a pH of 7-7.5, or gold chloride 381//l.
, sodium carbonate 101/'.

p) consisting of 37 formalin and 65 dll (7-7.5
Various methods of forming an electroless gold plating film have been carried out, in which the electroless gold plating film is formed using a plating solution of 10 to 20°C.

However, these plating solutions have problems such as short service life, slow plating speed unless the total concentration is high, high plating temperature (usually 90°C or higher), and purity of the plating film.
Currently, it is only used for relatively thin gold plating of 5μ, and such a thin gold plating layer is used for bonding of bonding wires used for connection with electronic components, and for silver soldering or silver-copper soldering of lead bins. There are problems in that the connection is sometimes insufficient, the adhesion to the substrate is poor, and the appearance is not good.

[Purpose of the invention]

This invention was made in view of the above-mentioned conventional problems.
The object of the present invention is to provide an electroless gold plating method that has good bonding properties and brazing properties of lead pins, and can obtain a better appearance.

[Summary of the invention]

That is, the present invention applies to the surfaces of nickel plating obtained by electrolytic plating or electroless plating, members heat-treated after nickel plating containing boron, and members flash-plated with gold to iron, nickel, or their alloys. When depositing high-purity gold by electroless gold plating, electroless plating is performed using at least a gold compound consisting of gold potassium, and organic acids such as citric acid, sodium citrate, tartaric acid, and their salts. It is characterized by the use of a complex compound consisting of the following, a reducing agent consisting of hydrazine hydrate, and a gold plating solution having a pH of 4 to 7 consisting of ammonium chloride or the like.

[Embodiments of the invention]

Next, a first embodiment of the electroless gold plating method of the present invention will be described.

That is, first, an unsintered alumina substrate is prepared, and tungsten powder, molybdenum powder, or a paste containing tungsten or molybdenum as a main component is screen-printed on desired parts of the alumina substrate, and then sintered at 1500°C to a thickness of approximately Form a conductor part of 20μ, and add 50% hydrochloric acid 501/l.
After soaking in a potassium fluoride aqueous solution for 5 minutes at room temperature, wash with water. Next, after activating the surface of this conductor part, a nickel plating layer containing boron is deposited using a nickel plating solution containing boron of about 5 μm. Next, after washing with water and drying, heat treatment is performed in hydrogen to recrystallize the nickel plating layer containing boron, immersed in 50% hydrochloric acid and 5011/17 potassium tsulfide aqueous solution, and then washed with water.

Next, an electroless gold plating solution adjusted to pH 6-7 with cyanogen gold potassium 29/l, sodium citrate 501/l, hydrazine hydrate 20 m/7, citric acid and sodium hydroxide was gently stirred at 45-50°C. As the process progresses, an electroless gold plating layer of desired thickness is deposited.

This electroless gold plating layer can be thickened at a rate of 0.5 to 1.0 microns. In this example, approximately 1 in 60 minutes
．． 0μ was deposited.

Next, after washing with water and drying, 30 minutes at 200-300℃
The electronic component envelope is completed by heating for ~60 minutes to perform a heat treatment for gold recrystallization.

The electroless gold plating layer formed in this way has high purity, and by recrystallizing the gold plating layer, it has a good longevity appearance and adhesion, and also has good bonding and brazing characteristics for electronic components. It was extremely good.

Next, a second embodiment of the electroless gold plating method of the present invention will be described.

That is, the steps up to the formation of the nickel plating layer containing boron were the same as in the previous example, but the electroless gold plating solution was cyanogen (total potassium 2 g/l, tartaric acid 5 og/l, ammonium chloride 501//l, hydrated). Hydrazine 30ynl/11
Sodium citrate or sodium hydroxide
Next, a third embodiment of the electroless gold plating method of the present invention will be described, in which an electroless gold plating layer is formed using Kl, and with gentle stirring at 45 to 50 DEG C.

That is, in this example, the electroless gold plating solution was 51/l of cyanogen-gold potassium, 751//It of citric acid, 401 d/l of hydrazine hydrate, 1 sodium citrate...4~
5, and form an electroless gold plating layer at 45 to 50° C. with gentle stirring.

Next, a fourth embodiment of the electroless gold plating method of the present invention will be described.

That is, in this example, as the electroless gold plating solution, cyanogen gold potassium 101/11 tartaric acid 5 oy/i 10 Tuser salt 50
1/l, pH 5-6, 45-50
An electroless gold plating layer is formed with gentle stirring at ℃.

The electroless gold plating solution of the above embodiment can be used for a long period of time by replenishing cyanogen-gold potassium and adjusting -.Also, in the above embodiment, a nickel plating layer containing boron was used as the base, but the present invention is not limited to this. This also applies to round parts that are nickel-plated and then heat-treated, as well as parts that are flash-plated with gold on iron, nickel, and their alloys.Also, since plating can be done at a relatively low temperature, it is possible to apply heat treatment to round parts and parts that are flash-plated with gold on iron, nickel, and their alloys. Of course, it can also be used for various purposes other than vessels.

〔Effect of the invention〕

As mentioned above, the electroless gold plating method of the present invention provides a gold plating layer that does not contain impurities, has a good appearance, and has excellent adhesion to the base, so its industrial value is extremely large. .

Agent Patent Attorney Inoue - Male

Claims (2)

[Claims] (1) When depositing high-purity gold by electroless gold plating on the surface of a member that has been heat-treated after nickel plating or nickel plating containing boron, or a member that has been flash plated with gold, the above-mentioned method is used. For electroless gold plating, a gold compound consisting of at least Kamechan gold potassium, a complex compound consisting of organic acids and their salts such as citric acid, sodium citrate and tartaric acid, a reducing agent consisting of hydrazine hydrate, ammonium chloride, An electroless gold plating method characterized by using a gold plating solution with a pH of 4 to 7. (2) The electroless gold plating method according to claim 1, characterized in that electroless gold plating is performed while gently stirring the gold plating solution at a temperature of about 50°C.