Home etch double sided boards?

[RobA]

I did it the other day on dbl sided copper clad.  the pcb came out great but my circuit didn't work in the end.  i blew a day & a half on that and ended up frustrated.  i have little hope of finding where the error is because some things are soldered in on the component side and obviously it is difficult to get any sort of a line of sight under the components, even though I left them partially raised.  it is possible that wiring things up on the top could work better.  that was the first idea I had but I decided to solder right on the pcb instead since there weren't too many connections there anyway.  but i can tell you, even a few are a lot in terms of general PITA'ness.  Plated through holes rule for double layer pcb's.  If you could just figure out how to use those it'd be golden.

I would recommend making a version of your circuit that doesn't have a 9v pour on the component side.  either that or increase the tolerance a lot as well as the size of your route traces, because the margin for error is just too great otherwise.  of course if it is a complicated design I realize that could cause all manner of clearance problems....

Thanks very much for this info. It looks like everything I feared might happen would. And, given the fact that your etches are orders of magnitude better than mine, I'm pretty much doomed . Oh well, I think I'll just have to live with the wait on this first board to see everything I need to fix on my layouts and then I'll have a bit more confidence to risk sending in multiples at a time.

[RobA]

Just what kind of circuits are people doing that they even need a double sided board? I've dozens and dozens of pcb layouts for everything from simple pedals to discrete component stereo amps and it's rare to even need a single jumper on the top side of the board.

dave

60 components, two of them 14 pin DIP's, one crystal, and a need for a large ground plane to connect the digital ground to. It all fits on to a 1.8" by 1.9" board. I suppose that it's possible to do single sided, but it's beyond my skills at this point.

[davent]

Ah, makes sense now! Double sided it is.

Thanks
dave

[nieradka]

Ive done double sided etches successfully, it helps to have a vertical etching tank so both sides etch evenly. You will also need some sort of registration system. I drilled four holes out of the pcb area, and then marked those on my pnp blue printouts so i ould line them up. Its hard to get perfect registration, dont use tiny traces. Remember sometimes you may need to solder both sides of a component.

[vattern]

To align the two layers with toner transfer, I transfer the first side, and then drill 4 (or more) of the .6mm holes towards the outside of the board. I then use sewing pins to push through the back of the transfer, through the holes and into some corrugated cardboard. Then apply the iron to side 2. YMMV

[madbean]

I've done several double sided boards successfully. There are a couple of tricks which help.

Use registration points on the four corners of each side of both top and bottom. These are 'crosshairs'. Transfer the bottom side first, then drill the four points carefully. Using a backlight, align the top transfer reg points to the bottom using the four holes as a guide and tape the transfer down.

Before printing, use an image editing program to remove all unconnected pads on the top transfer leaving only pads which have traces connected to them or vias.

Use small wires to connect vias from top to bottom.

Don't forget to reverse the top image before printing.

[Haberdasher]

Before printing, use an image editing program to remove all unconnected pads on the top transfer leaving only pads which have traces connected to them or vias.

Heck yeah, this is the part that would have helped me.   I'm having one of those now why didn't i think of that moments right now lol.

I may have to give this another shot....

[RobA]

Thanks for all the advice on getting this to work. I'll have to order a couple double sided boards to try it out on.

My order from OSH Park came in over the weekend. It got here quite a bit faster than I was expecting. So, I'm set with things for this round. Now that I know what I need to change in my library, I can feel a bit more confident just sending out a few prototypes at once. That should help with keeping my mind off double sided etching for awhile, but I'm sure it'll come up in my head again eventually.