I am making some PCBs for my senior project (using the toner transfer method) and it is getting pretty obvious that I can not do this with a single layer board. Up till now I have only made single layer boards. I suppose I could try making a double layer board but I have heard that it is difficult to get the alignment right (any one have any comment on this?). So the thought that came two me was to use a separate single layer board that would plug into the bottom if the main board in order to act as a separate wiring layer. The way I was thinking of doing this is routing as a two layer board, then put pin headers where the vias are and then make the top and bottom layer as separate boards. One will have male pins, the other female and then plug them together. Will this work? Second, when I make a two layer board, not all top layer wires come from vias because some come straight from the component leads that are supposed to go through both layer (but they wont in mine). Is there any way to trick eagle into always using vias to go between layers? I suppose I could just auto rout with one layer then manually rout the unrouted wires in the second but does anyone have a better idea?
Yes I suppose I could do that as well, and still use the same method with the vias, I found this http://www.neufeld.newton.ks.us/electronics/?page_id=81 where he suggests just that. I guess also I just wanted it to look a little better than having random wires jutting out.
It’s pretty easy. On the solder side, just route a short trace from the pin that passes to the top side and then switch to the top layer and route a very short trace. That creates a via. (you may be able to just drop a via on the end of the short trace and not have to fuss with changing layers - check it out) Then go and ripup the short trace on the top side.
Alignment is not difficult on a toner transfer double sided board. The only thing I find challenging is soldering the vias. It’s a real pain. You can solder one side fine, but when you try the other side, you liquify the whole thing and it either all just drops through, or sticks to the soldering iron and pulls right out. I end up soldering long leads through each one, then cutting them off afterwards.
To align both sides, just hold the two toner papers up against a light and align up all the drill holes. Then tape them together along two sides so that they remain aligned. Put the board between them, then iron or ‘laminator’ the toner on.
EDIT: and sometimes you still can’t use thru-hole components as vias or even run a trace to the top side solder pad for a component, because the component covers up the hole on the top side.
Yes, that’s the method I’ve mentioned I’ve fallen back on. I still find it a hassle, perhaps because I haven’t practiced enough, sometimes I’ll heat the thing right through and the wire will slide.
Actually, you mention 20Ga wire. Best I have is 22 in solid wire. I’ll have to look for some thicker wire. Thanks.