ETCHING & PLATING OF PLASTICS

Chromic acid, which is highly toxic, is used for etching plastics, such as ABS (a copolymer of Acrylonitrile Butadiene and Styrene). JP Laboratories have developed a inexpensive and nonpolluting system for etching plastics, such as ABS and ABS/PC alloys, for plating. The system is selective in etching polybutadiene. The etching system provides excellent adhesion of the plated metals. The adhesion of plated metals is about 2 - 3 kg/cm. The plating finish is excellent.

Etching Process: The etching system is composed of three baths: (1) pre-etching, (2) etching and (3) neutralization. The parts are treated in the pre-etching bath for 3-9 minutes between 40-60^oC, mainly to minimize dilution of the etching bath due to the drag-in of water. The parts are then etched in the etching bath for 3-9 minutes between 25-40^oC. The etched parts are then dipped in the neutralization bath for a few minutes before rinsing with water. The etched parts are then metallized using commercially available pre-plating and plating formulations and processes.

No Metal - No Organic: The pre-etching, etching and the neutralization formulations do not contain any organic or metal compounds. The etching system does not create any sludge. The rinse water simply requires neutralization with a base such as caustic.

Cost: The etching system will be significantly less expensive than the chromic acid etching system. The chemicals, e.g., mineral acids and the etchant, used in the etching system are commercially available in bulk quantities, and cost much less than a dollar per kilogram. The operating cost will be significantly lower because the system operates at lower temperatures and very little waste water treatment is required (the rinse water requires neutralization with a base).

Extensive Testing: We operated the etching system in our laboratory for months. Over 500 plaques and 300 parts were etched and plated. As long the operating parameters of the etching systems were maintained, all plaques plated with good finish and adhesion of the plated metals. The baths were rejuvenated as required.

Advantages and Benefits: The etching system offers many benefits and advantages over the chromic acid: It will be significantly less expensive, cost less to operate, essentially nonpolluting (metals or organic materials are used and the rinse water requires neutralization with caustic only), not create sludge, operate over wide ranges of time-temperature and concentrations and environmentally acceptable.