Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

Hi all,

To make spray-on prp resist work well, the copper has to be cleaned
well. Some things that work: salt and vinegar, salt and lemon juice,
citric acid, and probably lots of others.

I like citric acid the best, as its ok to use in the kitchen.
Mix up 30-50% powdered citric acid (sold in supermarkets), with
hot water until disolved. Wiping it over the pcb blank with paper
towel is sufficient to degrease it, without any harsh scrubbing needed.