The Viability of a Cyanide-free Immersion Gold Bath

A key discussion topic within the electronics industry in recent years has been about the impact of real estate pressure on lines and spaces. However, looming in the background is a very real issue that will not go away by simply being ignored. The monster in the closet is environmental awareness. 

The Tianjin chemical blast in August 2015 sensitized the Chinese authorities to the use of cyanide in production. As a consequence, the authorities have introduced licensing with regard to the use of cyanide. In turn, this has motivated Chinese PCB manufacturers to ask suppliers for a competent cyanide-free immersion gold solution (CNF Au). 

To achieve authenticity, the gold data for this article has all been generated in a 19-liter production simulation tank (Figures 1 and 2). Beaker testing can potentially result in non-representative findings. To ascertain the relevance of any data generated, statistical tools will be applied where suitable. 

Background

Although the main drive of this article is a benchmarking exercise, due to the application complexity, some of the elements studied need to be considered on their own merit. In the field, electroless nickel chemistries are normally combined with complementary immersion gold chemistries to provide a robust and reliable system. This article has maintained this approach, in that the immersion gold baths that will be compared to the CNF Au are purpose-defined.

To read this entire article, which appeared in the November 2019 issue of PCB007 Magazine, click here.