The Fab C board represents a prototype process change to streamline turn-around time. We experimented with the photo-etch process, but found it too costly if the board needs a quick fix. This led to a refined method of pre-drilling the copper-clad board with a CNC drill, then laying toner-transfer(TT) onto to the pre-drilled copper clad before etching. Bill's experimentation with TT led to a breakthrough discovery that increases resolution and nearly guarantees a perfect transfer. This new discovery allows us create perfect artwork transfers with traces thin enough to route between the pins on the PIC microcontroller.
Since we switched to CNC drilling the holes in the board, I had to come up with a program that would convert an N/C drill file into something that TurboCNC could understand. I also added a tool-path optimization algorithm that drastically reduces the drill time for the Arcsin board. I wrote the conversion utility in PERL and I may post it here after I clean it up a bit.
These stop action shots show the CNC drill in action.
About 30 minutes later, we have roughly 1200 holes drilled and we're ready to transfer some toner.
A shot of the Arcsin board after the substrate dust has been blown away.
The holes only require a bit of cleanup to get them ready for the TT.
After TT, the board is nearly ready to go into the etchant. By reducing the size of the pad holes on the TT printouts, we can allow some toner to slightly fill the holes and keep the etchant from eating away the copper foil at the edges of the holes.
Backside of the Arcsin, right out of the etchant.
This kind of resolution is almost as good as the photo-etch process.
Arcsin FAB C almost stuffed and ready for checkout.
Testing the Arcsin FAB C board.