Well there is a lot of fancy ways for doing this, depends on the amount of double sided home etched board you'd want to do in the future....
One fancy and easier solution would be to have a double side UV box, but you still need to have some flat weight on the board and the Transparent sheet or whatever.
I've seen people DIY'ing air tightening device (don't know how you call it in english) "Machine sous vide" in French, so to take all air out and to have a flat design on both sides.
That's how Big Companys do i believe.
I was going to build a box, using just one side of UV lamps and fit it like a cartridge when need to do double sided, so expose bottom side, than take the UV Cartridge out and fit it to expose Top side, you don't move design like this. Center section beeing the design and sandwiched between two thick glass panels, like 10mm or more for having it as heavy and flat as possible.
The other solution is like you mentionned, having some centering holes or so, but that means having like an aluminium or steel template frame for drilling the holes, two should suffice then guess. Drilling by hand won't make it very centered enough i guess, dunno never tried.....
I don't do that much double sided so i sticked to my easy pizzy "not much headache technique" well at least for me, since i got use to it now, so here it is, never got any faults so far (knock on wood)
This way of doing it has a limitation on size tough, meaning a little less than A4 since we need some room around, you'll see why.
- I print on transparent paper, or blurred type..
- Add two layers of the design for having a deeper black if needed, and drop some dots of crazy glue for keeping both prints in right place.
- Do same thing with the top design.
- Then take both assembly and align them together, and seal the alignment, top and bottom, with drops of crazy glue on one of the sides by drawing a line or whatever.
- Cut the board to the dimension required, but leaving some frame space around the design, i like to have at least 10mm, maybe a little more on one side.
- Fit the board between two design paper. EDIT: TRIM the cutted edges, we don't want bumps or whatever from the cutting process...
- Then do a crazy glue frame around it, on 3 sides of course, a U shape frame, leave one side wit more room to take the design out after all this....
For doing this, i draw a line of crazy glue on one side, and using two hard flat metal sheet, press both the PCB and the glued line together, to make things fit properly. We don't want to have too much "Wave" shape on edges or so on the design when putting some weight on, if you understand what i mean?
Do this on the 2 other faces, and you'll have yourself a nice trap for the PCB not to move when you turn it upside down.
OF course it will maybe feel a little loose because you take the Photosensitive protection off, but that ok, if you left a little more empty space on on side as mentionned earlier, you then just need to push the design in the trap a little more to keeping it in place.
Seems a long process reading this, but actually when you get your marks it's pretty quick, at least there is less concern about beeing aligned i think, well if your alignment was done on first place.
Try it on a small board or whatever, and see if it works good for you as well.
Hope that helps.
T.
March 27, 2015, 03:15:04 PM