Development of Chelating Ion-Exchange Resin Technology for Electroplating
Nickel impurities in pure gold deposits on printed circuit boards causes the non-sticking problem in wire bonding. Nickel impurities in the deposits originate from nickel(II) ion contamination in gold electroplating solutions.
The drawback of dummying is the significant gold deposition on a dummy cathode, leading to the loss of gold in gold electroplating solutions. Therefore, it is usually not adopted in gold electroplating solution treatment. Also, an extra effort to refine the gold deposited on a dummy cathode is required, and it involves toxic chemicals such as cyanide, and highly corrosive chemicals such as aqua regia, causing an increase in the risk of environment pollution and a lowering of safety in the workplace.
One of the main purposes of the gold strike is to protect the main gold plating tank against contamination. Since most of the nickel(II) ions will dissolve in the gold strike bath, a few nickel(II) ions can be brought to the main gold plating tank. This additional step increases the production cost significantly since gold is expensive and the cost for gold strike bath maintenance is necessary. NIckel(II) ions can still accumulate in the main gold plating solutions even the gold strike is implemented.
The use of chelating ion-exchange resins for contaminated gold electroplating solution treatment can produce a small gold loss because the resins can selectively adsorb the nickel(II) ions in the gold electroplating solutions, resulting in a prolonged life of the gold electroplating solutions and the lowering of the product rejection rate. The frequency of dumping of the contaminated gold electroplating solutions will be reduced. The gold strike process can potentially be eliminated in the gold electroplating process. Also, the impact on the environment and health due to the subsequent gold recovery process and waste electroplating solution treatment can be minimized as the utilization frequency of these processes is reduced.
Deliverables
- Nickel and gold adsorption performance of three chelating ion-exchange resins (resin bearing iminodiacetic acid, aminophosphonic acid and bis-picolylamine).
- Optimum pH for nickel adsorption by the resins.
- Influence of the amount of Au(CN)2– upon nickel adsorption on the resins.
- Optimum contact time for nickel adsorption by the resins.
- Nickel adsorption kinetics under the influence of Au(CN)2– will be determined.
- Nickel adsorption isotherm under the influence of Au(CN)2– .
- Molecular information of the Ni and Au loaded resins.
