Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
  • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
  • C23C18/31—Coating with metals
  • C23C18/42—Coating with noble metals
  • C23C18/44—Coating with noble metals using reducing agents

Definitions

• the invention relates to a stabilized aqueous, alkaline gold bath containing a dicyanogold (I) complex, a complexing agent, a reducing agent and conventional additives for electroless deposition of gold on gold and metals that are less noble than gold, and on alloys of these metals.
• a dicyanogold (I) complex a complexing agent
• a reducing agent a reducing agent for electroless deposition of gold on gold and metals that are less noble than gold, and on alloys of these metals.
• Gold baths for the currentless deposition of gold are already known. These are alkaline or acidic gold baths which contain predominantly an alkali metal dicyanoaurate (I), a complexing agent, a reducing agent and additives for controlling the deposition rate and for improving the adhesive strength (US Pat. No. 4,091,128, US Pat. No. 3,300,328, US -PS 4,154,877, US-PS 3,032,436, DE-OS 2,052,787, DE-OS 2,518,559). All of these baths generally have an unsatisfactory stability and decompose with the deposition of metallic gold.
• I alkali metal dicyanoaurate
• the gold baths mentioned are also only suitable for gilding those metals that are less noble than gold. In contrast, optimal electroless deposition of gold on gold is not possible using these baths.
• the object of the present invention is to provide a stabilized aqueous, alkaline gold bath which enables the electroless deposition of gold on gold and less noble metals than gold and their alloys.
• a particular advantage of the bath according to the invention is that gold can be deposited electrolessly on gold surfaces from a stable bath. Existing gold layers that are too thin can thus be reinforced as desired using the bath according to the invention.
• the bath also enables the gold-plating of alloys that are common in the semiconductor industry, for example iron-nickel and iron-nickel-cobalt alloys and chemically reductively deposited nickel alloys such as nickel-phosphorus, nickel-boron and pure nickel.
• the bath is particularly suitable for gold deposition on diffusion layers such as nickel-gold or cobalt-gold.
• alkali dicyanoaurates (I) are suitable as dicyano gold (I) complex, for example the sodium and potassium complex salts and the ammonium dicyanoaurate (I).
• the concentration can advantageously be from 0.05 g gold / liter to 30 g gold / liter.
• Alkali borohydrides are used as reducing agents, which are extremely stable in the electrolyte at a pH value greater than 13.
• Alkali metal cyanides which serve to stabilize the dicyanoaurate I anion, serve as complexing agents. Molar ratios of 1: 5 to 1:10, that is to say a large excess of free cyanide, are particularly suitable.
• the labeled glycol derivatives and polyethyleneimines are used as stabilizers, which have an outstanding effect, which was not foreseeable.
• Examples of compounds with an outstanding stabilizing effect are ethylene glycol monoethyl ether, diethylene glycol monoethyl ether and polyethyleneimine.
• the basic composition of the bath according to the invention is as follows: Gold as metal 0.05 - 30 grams / liter Stabilizer 50 - 700 grams / liter Alkali cyanide 10 - 100 grams / liter Alkali hydroxide 5 - 100 grams / liter Reducing agent 10 - 100 grams / liter
• a molar ratio of reducing agent to stabilizer of 1: 4 is particularly advantageous for stability.
• the working temperature of the bath can be selected from around 40 to 90 ° C. Surprisingly, even at higher temperatures there is no decomposition of the bath, that is to say the precipitation of elemental gold.
• the bath according to the invention is used in a manner known per se by appropriately dipping the part which has been pretreated depending on the base material in the bath solution.
• Another advantage of the bath is that it can be used repeatedly without the elemental gold being filled by decomposing the bath.
• the bath according to the invention can be used in particular for the chemical gilding of metallic surfaces such as gold and less noble metals than gold, for example copper, silver or nickel and alloys of these metals.
• a particular advantage of the bath according to the invention is that the deposition rate surprisingly remains the same even after a standing time of several months.
• Another advantage is that the bath according to the invention works with a uniform deposition rate of up to 1.5 m / h.
• the bath according to the invention can be used with great success for gold layers of soldered connections which are formed by crystal or wire bonding, which is of particular technical value.
• the stabilizing bath compositions listed below can be used to deposit very uniform and highly adhesive and ductile coatings under the working conditions listed.

Landscapes

• Chemical & Material Sciences (AREA)
• General Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Chemically Coating (AREA)
• Electroplating And Plating Baths Therefor (AREA)

Applications Claiming Priority (2)

Publications (2)

Family

ID=6322785

Family Applications (1)

Country Status (5)

Cited By (4)

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• 1987
  • 1987-03-09 DE DE19873707817 patent/DE3707817A1/de not_active Withdrawn
• 1988
  • 1988-02-17 EP EP88102273A patent/EP0281804A3/fr not_active Ceased
  • 1988-03-08 JP JP63052778A patent/JPS6425987A/ja active Pending
  • 1988-03-08 CA CA000560784A patent/CA1290993C/fr not_active Expired
  • 1988-03-09 US US07/165,832 patent/US4838937A/en not_active Expired - Fee Related

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