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Waste treatment for advanced semiconductor packaging operations

Due to the maturity of plastic packaging technology in the semiconductor industry, a long history of successful waste treatment and water recycling applications exists. However, new packaging technologies have evolved that do not limit bond pad location to the edge of the die. These technologies require deposition of a solder bump on the bond pads for electrical connection between die and package. The solder bump and under bump metallurgy (UBM) can be deposited via electrolytic plating, electroless plating, evaporation, sputtering or other techniques. Many of these metal deposition techniques bring with them new and different metal bearing waste streams that require treatment or disposal. The focus of this paper is on treatment of wastes from electroless plating operations used to deposit the UBM. This process generates several relatively low volume metal bearing concentrated waste streams, and a relatively high volume metal bearing rinse water waste stream. Several waste treatment methods were evaluated to determine the optimum method based on total costs and environmental health and safety (EHS) risks. First, characterization of the wastes and costs for off-site disposal were determined as a worst case baseline and fall back position. Second, on-site treatment with sludge generating treatment methods were investigated. Finally, on-site treatment using more elegant nonsludge generating treatment methods were investigated. Although the exact chemistry and process sequence are of course proprietary, the general waste treatment schemes, unit operations and results are presented.