PCB pens

[Mike I.]

The only way I get good results from "etch resist pens" is to use fine 
scouring powder (such as Ajax cleanser, slightly moistened) to clean the 
copper surface. DO NOT USE STEEL WOOL - even very fine steel wool gouges 
the copper surface and promotes pitting. After scouring, wash the board 
well with warm water, followed by a rinse with methanol, and dry well 
before using the pen. Using scouring powder I get a perfect etch almost 
every time (boards with 15 chips and dozens of other components). I use 
a Staedtler Lumocolor 317 fine-point marker and ferric chloride etchant.