Double sided PCB's

[Ron Hayes]

I've been making single sided PCB's for a while now using pre sensitized board, now I have a much more complicated board to create and I think I need to use double sided board, I just like to get some tips from those of you that have done this and can pass along a few hints as far a lining up the two sides.
All I can think of for now is to drill 4 holes in the board to line up with 4 holes on the transparency before applying the images.<p>Thanks
Ron

[grant fair]

I read about someone making double sided boards who would carefully put the two transparencies for both sides on top of each other and line various holes (like pads) so they are in line. Then the transparencies are taped together along one edge, and the pcb can be placed between them, but they are still in alighment. Hopoe that is helpful.<p>Grant

[Ron Hayes]

Hmm that sound easy, won't there be a bit of distortion due to the thickness though? I should give that one a try though on a small test board to see how well it works!<p>Thanks
Ron

[Dean Huster]

Grant, that idea will probably work as long as the artwork doesn't have very fine pitch and if the edge of the board is nowhere near the taped edge where any "roll" might affect registration. For most applications, it might not be a bad way to do it.<p>Using the toner transfer process, I first drill four registration holes near the board corners (they correspond to holes I've made on the drawings) and then shove straight pins through the films and the board to register. Then I put the whole mess in the dry mount press for the "ironing" process.<p>Dean

[chessman]

When I did three different double sided boards, I put just a printout of the layout on computer paper down, drilled all the holes, and then put down the real board layout, lining it up with the holes.<p>Oh yeah, make sure you are drilling with a VERY hard piece of wood underneath the board so the copper doesn't split and lift off from the board un-evenly.<p>[ March 12, 2003: Message edited by: chessman ]</p>

[Dimbulb]

My double sided skills are limited.
Side A for me is fairly "top view". The B side is what fits beneath while keeping the top view perspective as the main stay. The top view is where the through hole parts reside. However later what does'nt work out on the bottom ends up on top.<p>You can print side A on clear sheet with one color. On a separate clear sheet and there are four register marks that match on each. I use a window with good light, tape the sheet to a translucent white backgound. <p>Sometimes a grease pencil to rough out what you need will get you started. It sort of plans the general layout defining clusters. The revisions usually take place at test board stage.<p>One section at a time can be drawn out on paper (with lots of erasing). I check the design against the first side frequently and I must feel fairly confident before I move on to another section. Label carefully using letters to mark the trace endpoints helps to keep the match up process simple and revisions are much easier.