Step 11: Etching Conductive Cloth for Soft Circuits
For the robot pumpkin head circuit I wanted to etch a very simple pattern as I was going to be trying several new techniques to glue and laminate the circuit.
The problem has always been to find an inexpensive, simple way to get a resist that is removable but will etch sharp high resolution conductive traces. I experimented with all kinds of tapes but they were either not waterproof enough or they had so much adhesion they peeled off the conductive coating on the fabric.
I finally tried clear vinyl shelf liner. It is just sticky enough to keep out the ferric chloride etchant, but not so sticky that it wont come off cleanly. the conductive cloth is placed on a piece of shelf liner with its sticky side up. this seals the back side. Another piece of liner is cut with a sharp x-acto knife to remove vinyl wherever the circuit needs to be etched. The conductive cloth is then sandwiched between the two layers of shelf liner. See pic15.
The cut traces are then burnished with a Popsicle stick to make sure the edges are adhered well to the cloth. It is then dipped into ferric chloride etchant for five minutes at room temperature. As soon as it looks well etched, it is removed and immediately submerged in a bucket of water and swished around. Remove it from the water and then rinse it some more to be sure all the etchant in the fibers is removed. the shelf liner can then be slowly peeled off and the cloth left to dry. Pic16 is the final cloth circuit board.
I have been experimenting with etching conductive cloth for several years. For some of the results see here: http://www.instructables.com/id/Conductive-Fabric-Make-Flexible-Circuits-Using-An/