Most PCB fabricators are using a chemical clean, usually two steps, with an
alkaline clean as the first step, and some sort of acid, either straight
cleaner (much less costly) or microetch.

If you can afford the process chamber length, an alkaline clean followed by
acid clean is the least expensive, and most effective.  Microetches start
justifying their very high cost (usually 5X per square foot) when the lines
are short, and exposure time is not long enough.

An alkaline cleaner actually has the potential of getting a surface cleaner
than an acid, properly done, but it cleans slowly.   Acids clean fast, but
are not real good on organic soils, including some anti-tarnishes.

At the end of the day, it is a decision that balances equipment costs, floor
space, chemical costs, waste treatment issues (clearly microetch removes a
lot of copper), and yield considerations.   We even have one customer who
uses a microetch because he believes that it minimizes defects caused by
dents in the Copper foil.

Rudy Sedlak
RD Chemical Company

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