Case study: Printed Circuit Board Manufacturing

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Courtesy of Watman Ltd.

Aspocomp Ltd. is a Finnish leader in the manufacture of printed circuit boards (PCB), thick film hybrid circuits and mechanical assemblies for the electronics industry. Its main customers are European manufacturers of electronics equipment.

Rather than producing and marketing its own products, Aspocomp relies on its customers who design the product and provide the specifications and drawings, while Aspocomp provides the necessary production and process know-how via its ISO 9000-certified manufacturing operations. Product quality, prompt delivery and a flexible response to customer requirements form the foundation for Aspocomp’s competitiveness.

Most PCB plants in existence today have had problems with following the letter of the environmental law as the PCB process chemistry is complicated, and additionally product quality must always be high: this high quality can only be achieved by using plenty of water. Facilities have fulfilled the requirements of the regulations only by effectively controlling the effluents and the process parameters.

Dissolved in water by itself, copper as a simple salt of an ion that does not interact with copper, such as copper sulphate, will precipitate almost completely by only adjusting the pH. The problem arises when different waste streams are mixed together and, consequently, water treatment to remove heavy metals becomes difficult or expensive, or both. When ammonia or any other complex forming agent, such as EDTA, is mixed with copper, a strong copper-complex will form. This complex can easily pass the normal neutralization treatment

Effective agents (precipitants) that will remove copper from strong complexes, have been developed, but unfortunately, they are expensive. Much of the problem potential with the chelates can be solved by keeping the most difficult fractions separate and by maintaining the lowest level of copper possible.

When studying the alternatives in the Aspocomp Espoo facility, ion exchange waste treatment seemed to be a good approach. The resin used is very selective for bivalent cations such as Cu 2+ , Zn 2+ and Ni 2+ , against sodium but also against calcium ions. Metals from the ion exchanger eluates can be precipitated by normal methods.

Major efforts — both in the production processes and in the effluent treatment — were made to meet the most stringent limits set for metals in industrial process water coming to POWT. Three years after finalizing the effluent treatment plant, ion exchange now seems to be a good choice. Effluent from the Aspocomp Espoo PCB facility not only complies with the maximum limits given by the local authorities but also with the lower internal copper limit given by Aspocomp itself.

The copper concentration of the effluent does not exceed 0.5 mg Cu/l.

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