My first attempts at etching these boards didn’t go so well. Using the toner transfer method has worked very well for me in the past, but it looks like my current printer doesn’t work as well as the one I used previously.
Below are a few pictures of the backplane boards I tried etching, the first photo based off a slightly older design with narrower traces. While the traces were etched fairly accurately, the surface of the traces has some fairly deep pitting where the toner coverage wasn’t thick enough. The worst of the pitting has eaten through to the fiberglass.
In some places the toner didn’t stick down very well, possibly because the board wasn’t clean enough or the toner hadn’t set properly. Ahh well, looks like more testing is needed.
While it is annoying to have wasted two boards worth of PCB material it is good to iron out these problems now. I have gone through all of the boards and increased trace width and also modified some packages to increase the size of pads and decrease drill size which should help with etching. Now I just need to improve the transfer process!