Making Circuit Boards

It is now rather easy to make your own single-sided printed circuit boards at home.  The total cost runs about 25 cents per square inch - board,chemicals, and all.

There are lots of ways to do the artwork on your computer.  I have a layout program that I wrote years ago that is good for single sided boards.  Free for you DOS program ECAD.

The problem has been in printing the transparency.  The clear plastic sheets for overhead projectors do not do a good job of making solid dark lines and most paper does not transmit light well.

The solution is to use vellum.  The usual kind from the office supply store was working ok for me, then I found some really great stuff at Marco's Paper on the net.


http://www.marcopaper.com/translucent_vellum.htm

This paper has both very high light transmission and also prints very fine detail on an inkjet.

I made a jig out of some 0.1 inch thick plexiglass with 0.060 inch shimming around the edges.  The shim is the same thickness as the circuit boards and allows them to be sandwiched tightly with the vellum image.



The board is indexed into a corner and the vellum is taped in position (face down) over the board.  The top piece is held in place with rubber bands.

This assembly is then placed about 4 inches under one of those 'maginifier' florescent desk lamps and exposed for about 30 minutes.

(I have switch to using a 75 watt halogen spot  bulb on a jig at about 18 inches.  This does a nice exposure in about 4 minutes)

The newer type of presensitised boards (Ever-Muse) do not need ultraviolet light.  These boards, allong with the developer, are available from Circuit Specialists

http://store.yahoo.com/webtronics/

The dry mix for making one quart is only about a dollar.  Since the instructions claim that it must be used within 24 hours after being mixed, I only mix up enough for each board.  The usual, ferric cloride, is then used for the etching.  Don't forget to remove the etch-resist coating from the traces before soldering components.  The local $1 store has acetone (sold as nail polish remover) that work well for this.