In doing some research into programming the Analog Devices AD9850 DDS chip, I ran into an application note AN-557 by G3XJP on using the AD9850 as an LO in an amateur transciever. He mentioned in passing a circuitboard prototyping technique which I had never heard of before and which seemed easy to do. I gave it a try. It worked. I have never made a circuit board before and was very happy with the results. The technique basically involves spray painting a circuit board then scratching away the paint to form "Trace Islands". The paint protects the circuit board from the etchant. The lines where the paint has been scratched off gets etched away leaving circuit board trace islands. I accidently ordered a couple surface mount 16F84 PICs. I needed to mount them on a prototype board in order to get access to the pins. I took a few photographs of the process as I thought the technique would be of general interest to experimenters.
Small screwdrivers and scrimshaw needles make great scribes. I wound up using the side edge of a tiny set of eye glass screwdrivers as my most-used tool.
Tools you will need: Spray paint (I used ACE Rust-Stop black) Paint remover Etchant Hemestat tweezers Plastic container Funnel to get the etchant back into its bottle. Q-tips to help with etching. Various Scribes Sharpie pen to fix mistakes in case you scratch away a place you didnt mean to.
Scratch between the pins of your chip. Scratch in the destination pads.
Scratch in the traces. If you goof -- no problem -- just paint over the goof with a Sharpie pen and scratch again.
Pour your etchant (I got mine from the local Radio Shack) into the plastic bowl. Grab the circuit board with your tweezers. Note: Your tweezers wont be ruined but they will loose their shiny finish. Use a pair you dont like too much. Move the board around in the etchant for about 10 minutes. You can speed things along a bit if you periodically use a Q-tip to lightly wipe the traces with etchant. Pour the etchant back into its original container using the funnel. Wash the circuit board and your other tools. Clean off the remaining paint with paint remover and your fingernail.
Check adjacent pads with an ohm meter. (One with continuity beep is nice.) If you have any problems, you can use your scrimshaw needle to help clean out any copper left in the etched lines.
Hey - not too bad for a first try.
Best Reguards, Mike KL7R Juneau, Alaska http://kl7r.ham-radio.ch/scrimshaw