Over the period of a year our product mix changes from producing 90% solder coated circuits to producing 80% solder mask over bare copper (SMOBC) circuits. In both processes tin lead was plated over the circuits to act as an etch resist. The tin lead is stripped off after etch on SMOBC product. The change in product mix increased the lead in the influent to waste treatment from 1 mg/l to 35 mg/l in a 50 gpm system. This is an increase of approximately 2,300 kg per year of lead added to our sludge. The etch resist plating was changed to acid tin for SMOBC boards reducing the influent to waste treatment to below original levels.
Electroplating tin, etching the base copper, striping the tin, masking over the copper circuits, and applying solder by hot air solder level to only the holes allows for less lead on the finished product and no ionic forms of lead in high concentrations in the production process.
The process change reduced the amount of lead in the waste water treatment sludge by 5,000 pounds per year just from rinse water. This reduced sludge generation by 52 drums per year. The 3,300 gallons of stripping solution which averaged over 10 g/l was condensed and disposed of off-site. Now that the stripping solution no longer contains lead it is treated in house with other corrosive solutions, reducing the lead waste by 275 pounds per year and reducing liability
Details of Reductions
Additional Information :
The savings in reduced disposal cost is $14,000 per year. The project cost was $20,000 thus pay back will be 1.5 years.