Board Preparation

After drilling from the top side, the holes on the metal side of the board will now have rough edges from the dental burr piercing through. You must sand these smooth to the touch, without scratching up the rest of the copper surface. The best way to do this is by wet-sanding with a small piece of "Wet-or-Dry" sandpaper, 400 grit or so. (This is the black or dark gray paper.) Rinse frequently while you are sanding. The same scrap of paper can be used repeatedly for many boards.

Next, the copper surface must be scoured clean to remove any oils or oxidation that didn't come off in the sanding. Use a regular kitchen-type steel wool / soap pad like "Brillo" or "SOS" for this, then wash the board with a drop of dish detergent and rinse thoroughly to remove traces of soap and steel fibers. You may want to try other scouring pads like "Scotch-Brite", etc, which can be used directly with dish detergent.

Alternatively, you can use a small tuft of very fine (grade 00 or finer) steel wool with a drop of dish detergent. Again, make sure you rinse off all stray steel fibers as well as the detergent.

Dry with a clean towel... the copper should have a soft shine. Avoid touching the surface.

See also Printed Circuit Construction