Gold plating, electroless

Electroforrning, which is used in the production of art objects or jewelry is a combination of electroless plating and electro deposition. A wax mold of the object to be produced is made conductive by electroless gold plating, a thick layer of gold or gold alloy is then electrodeposited and, finally, the wax is removed by melting (134). 

For more than 20 years, there has been sporadic interest in electroless gold plating as a simple and inexpensive method of depositing gold on semiconductors and circuit patterns. Recently, interest in this method has increased because of the need of depositing gold on small isolated areas of high density circuits fabricated on ceramic or plastic substrates. 

When electroless gold must be deposited on nickel metal, the common practice is to precoat the nickel with galvanic displacement gold prior to plating electroless... 

The Au(I) sulfite complex is well known to be the source of gold in an electroplating bath. Will the Au(I) sulfite complex in the absence of thiosulfate work as a source of gold for electroless plating ... 

To find the conditions in which the electroless deposition of gold at Ni-P surfaces with an acceptable appearance and adhesion would be possible, the activation of Ni-P substrates with 10% HC1 solution or a mixture of 0.1 M NH4F and sodium sulfamate was investigated. The results showed that only low phosphorus alloys (P content less than 5 wt%) pretreated with ammonium fluoride/sodium sulfamate mixture can be used for a successful electroless gold plating from cyanide solution and hydrazine as a reducing agent.31... 

Table 12 summarizes the commonly used electrolytes. Reference [42] reviews recent topics in electrolytic and electroless gold plating. 

Shimizu, S. Yoshiba, K. Electroless gold plating solution for forming gold films on electroless nickel plated films. Jpn. Kokai Tokkyo Koho JP 2005307309, 2005 Chem. Abstr. 2005,143,444651. 

Contrary to non-noble metallization, the electrical resistance of ICA joints mounting a gold-plated QFP80 component on an electroless Au-plated FR4 board is quite stable in the 85 C (185 °F) and 85% RH environment. No significant increase can be observed up to 2000 h. Hence, it can be concluded that a noble metallization such as Au or Ag-Pd is preferable for normal ICAs. However, by adding corrosion inhibitors, some superior ICAs for pre-tinned metallization have been developed (Ref 13). 

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