71JE Harris and WH Rees US patent 4774101 1988

72. K. Minten and J. Cisson, Circuit World, Vol 19 (No. 2), 1993, p 4 Environmental and Safety Issues

The electroless copper plating industry has come under increasing legislative control in recent years, due to a variety of environmental and safety concerns relative to the chemistry and processes. The main issues are quality of waste water discharged, volatile components discharged, and health and safety concerns about handling of the various chemicals.

Waste Water. Regulations regarding effluent vary dramatically, both globally and within single countries. This factor has probably contributed significantly to the relocation of numerous plating facilities to areas having less stringent regulations. Copper itself is probably the main concern; waste treatment equipment designed to plate residual copper from discarded plating solutions will normally reduce Cu2+ below the legal limit (typically 1 ppm). Strong chelates have become a concern recently due to their tendency to dissolve any metallic surfaces encountered, either before or after discharge. Certain plating bath additives used in the past, including mercury and cyanide compounds, have been virtually eliminated from use due to waste water restrictions. Adjustment of waste water pH to a neutral range is also usually required. Chromium, used in POP pretreatment, is particularly toxic to the environment, but virtually all current users recycle their chromic acid etchants internally, thus avoiding any discharge. Discharge of strong oxidizing or reducing agents is also typically regulated closely. The issue of waste water treatment is so key to operating a successful plating operation that considerable literature on designing and implementing waste treatment systems is available (Ref 73).

Handling of individual chemicals in the plating process presents a number of concerns. A significant concern is the use of formaldehyde, which has been shown to be a carcinogen for certain laboratory animals, although no direct link with cancer in humans has been demonstrated at this time. Limits by the Occupational Health and Safety Administration on airborne formaldehyde have recently been reduced from 1 to 0.075 ppm (8-h time-weighed average permissible exposure in air). Concerns about formaldehyde, as well as concerns about waste treatment of electroless copper, have contributed to ongoing development of direct electroplating (Ref 26, 69, 74, 75), which could eliminate the need for electroless copper, particularly in portions of the PWB market.

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