90    NON-CONVENTIONAL METAL PRECIPITATION AT A
PRINTED CIRCUIT BOARD MANUFACTURER:
A CASE STUDY
Charles Ficker, Senior Chemist
William S. Carter, Product Manager
DuBois Chemicals
Cincinnati, Ohio 45202
Jim Martin, Plant Chemist
Circuit Center, Inc.
Dayton, Ohio 45440
INTRODUCTION
Circuit Center, Inc. is a manufacturer of printed circuit boards located in Dayton, Ohio. The
production of circuit boards is accomplished through a series of wet chemical processes, and a number
of graphic art procedures. Details of production techniques will vary from one facility to another;
however, the basic processes of board etching, electroless and electrolytic copper plating, and water
rinsing are consistent.
The great majority of wastewater at Circuit Center, as at all board shops, is generated in the rinsing
operations. Here water picks up organic material, suspended solids and metal ions, including: copper,
tin, lead, nickel and other species. Another significant source of copper at Circuit Center is from the
use of a proprietary ammonia etchant. This is used to dissolve away unnecessary copper from the
circuit board laminate. This ammonia as well as the electroless plating process results in copper ions
which are compiexed and difficult to precipitate.
To protect human health and the environment, the toxic metal ions and other contaminants of
concern must be removed prior to discharge. As a circuit board manufacturer, Circuit Center falls
under the Federal Environmental Protection Agency (EPA) guidelines for metal finishers. Local
ordinances for wastewater discharge must be no less stringent than the Federal EPA Guidelines. Also
per federal law, any sludge from an electroplating rinse treatment is a categorical hazardous waste and
subject to the regulations of the Resource Conservation and Recovery Act (RCRA) and its
amendments.
When Circuit Center built a new facility in 1983, new EPA regulations were imminent, becoming
effective in 1984 (See Table I). The management of Circuit Center made the conscious decision to
minimize environmental impact. Among other actions, the shop was made solvent free, using only
aqueous cleaning, and an engineering company was selected to install a state-of-the-art waste treatment system. However, when Circuit Center began operations in 1984, it became apparent there
would be difficulties with compliance. The federal limit of 4.5 mg/L copper and 0.6 mg/L lead were
attainable. However, the local control authority, Montgomery County Sewer District, planned limits
Table I.    Printed Circuit Board Pretreatment Regulations 1984
Contaminant 1 Day Max 4 Day Average
Cyanide, Total 1.9 mg/L 1.0 mg/L
Copper 4.5 mg/L 2.7 mg/L
Nickel 4.1 mg/L 2.7 mg/L
Chromium, Total 7.0 mg/L 4.0 mg/L
Zinc 4.2 mg/L 2.6 mg/L
Lead 0.6 mg/L 0.4 mg/L
Cadmium 1.2 mg/L 0.7 mg/L
Total Metals 10.5 mg/L 6.8 mg/L
45th Purdue Industrial Waste Conference Proceedings, © 1991 Lewis Publishers, Inc., Chelsea, Michigan 48118.
Primed in U.S.A.
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