Drilling
- DON'T USE A DREMEL TOOL!
- USE A DRILL STAND OR PRESS
- Use only carbide drill bits
Usually, component leads go through the board, so we have to drill them out. A drill press or a cheap drill press stand for a portable drill is ideal. A Dremel tool isn't meant for precision drilling--since it does not have a real chuck on it, the drill tends to "precess", making the hole larger than the bit or causing the drill to break.
Sizes:
0.022 transistor leads, small holes
0.035-0.040 IC/resistor leads, general 0.046 large transistor leads
Finishing
- Electroless tinplate solution makes a board easier to solder and keeps a good finish for a long time.
- Solution is a powder which dissolves on hot water. Solution is reusable, but has a limited shelf life (about 6-8 mos).
I used to make boards without tinning them. In a day's time, fingerprint acids begin to discolor the board, and it looks horrible. Electroless tinplating is cheap, fast, and makes a board look professional. In addition, parts are easier to solder on, and if you need to rework the board later, tinning makes that much easier.
Did you clean the board before you etched it? Well, clean it again! This time, rub with steel wool and Ajax (or similar) abrasive cleaner. You must get off all the resist, all the fingerprint oils, and all etchant residue. AN OILY PATCH ON THE BOARD WILL NOT TINPLATE.
Like with etchant, use a Pyrex or plastic tray for tinplate (NOT the same one as the etchant--they are NOT chemically compatible!). Follow the directions on the tinplate package. Except for one point: I like to mix the tinplate crystals with HOT water, because they all dissolve that way. Be careful--there's an exothermic chemical reaction when those crystals hit that hot water! Use goggles.
Now, sit back, enjoy a beverage, and admire that nice-looking PCB for a bit before your put the components on it. |
