Homebrew PCBs

making a pocket is the easiest way to do this.  what is explained
below works very well and usually the only issue one might run into is
the printing heating the PnP blue slightly different causing the
layout to be slightly off.  kinda like shrinkydink.




On Jul 5, 2015, at 8:41 AM, Mat Smith hazymat@...
[Homebrew_PCBs] wrote:


>
> I must say, the idea of gluing together two single-sided PCBs to
> make a double-sided PCB seems excessively tedious.
>
> Perhaps it's because I don't really agree with you that the most
> difficult part of a double-sided PCB is lining the holes / tracks up.
>
> When I first started, I thought lining up the holes would be the
> most difficult part. But I've never had anything but great success
> in this area.
>
> The most difficult part for me has been knowing how long to iron and
> the time it takes to peel. To get excellent results (really fine /
> straight edges to tracks and toner that adheres amazingly well) I
> iron for 35-40 minutes... and the longer I iron the harder it is to
> remove the paper. This to me seems excessive but anything else
> results in having to use a lot of sharpie and boards that don't look
> as nice.
>
> May I ask exactly how you are lining the layers up?
>
> Here's my process. Here I overexplain it, but it doesn't actually
> take more than 3-5 minutes.
>
> I cut the two pieces of paper, one piece slightly smaller than the
> other to allow for better grip when I tape them together.
>

> I hold the two pieces of paper up against a worklight and ensure the
> designs line-up perfectly, then fold a tiny piece of masking tape
> over the two pieces of paper, in the middle of one of the edges. I
> then hold them up to the light to ensure they are still lined up,
> and add another small piece of tape onto the middle of another of
> the edges. If for some reason the papers became misaligned it's then
> easy to remove a single tab of tape and do it again.
>
> Finally, repeat the process for the third side, check the alignment
> by shining the worklight through the papers, then run tape
> lenghtways down all three sides.
>
> Drop the board in (which has been prepared obsessively with metal
> wool and white spirit / acetone) and check there that the effect of
> separating the papers with the 1.6mm FR4 hasn't misaligned the
> papers. Almost every time I've dropped the PCB in, it hasn't caused
> any misalignment. Always check the papers lie flat.
>
> When the PCB is in, seal the final 4th side with a line of masking
> tape. It doesn't matter if the PCB rattles around, in fact it's
> better to make the paper a fair bit larger than the PCB that drops
> into the envelope you have created.
>
> You then line up the PCB so it fits to the design just before you
> iron (using a worklight again).
>
> The above hasn't failed for me ever, and it's pretty quick to do
> despite my over-explanation!
>
> Thanks
>
> Mat
> On Sun, 5 Jul 2015 at 12:14, 'Tony Smith' ajsmith1968@...
> [Homebrew_PCBs] <Homebrew_PCBs@yahoogroups.com> wrote:
>
>
> The drilled holes will never line up properly, it’s a fundamental
> property of universe.
>
>
>
> When gluing use a bright light underneath so you can see both sets
> of tracks, and use something like the mounting hole outlines to
> align them.
>
>
>
> Tony
>
>
>
>
>
>
>
> From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com
> ]
> Sent: Sunday, 5 July 2015 3:14 PM
> To: Homebrew PCBs
> Subject: [Homebrew_PCBs] Gluing 2 single sided boards to make a
> double sided board.
>
>
>
>
>
>
>
>
>
> Double sided boards as we all know can be a bit of a pain, the
> biggest problem is getting that precise alignment between sides
> correct so that when you drill in the center of your pad on one
> side, it comes out in the center of the pad on the other (and not,
> as is not uncommon, breaking out, and probably messing up the trace,
> or a trace nearby...).  Especially if your only able to expose/
> imprint artwork one side at a time.
>
>
>
> Even more frustrating when one side comes out perfect in part of the
> process (eg, developing) and the other side is too flawed to be
> useful, meaning you get to start from scratch again.
>
>
>
> So, the thought randomly occurred to me today, if you could prepare,
> expose, etch, drill the two sides of a double sided board completely
> separately, and join them up at the end of the process, it would
> make getting precise alignment of those sides almost a non-issue, 
> assuming you can drill even roughly vertically and hit the center of
> the holes it's just a matter of lining up the holes you drilled on
> each side.  And also means that the success or failure of each side
> is independent of the other.
>
>
>
> Of course, it does double the drilling, but that's the easy bit
> really.
>
>
>
> This is also of course more or less how multi layer PCBs are made by
> fabricators, a stackup of already prepared pcb layers and resin
> impregnated sheets.
>
>
>
> Single sided laminate at 0.8mm thick (and you can get down to 0.5mm)
> is available out of China for cheap.
>
>
>
> Eg:
>
> http://item.taobao.com/item.htm?spm=a1z10.5-c.w4002-1192550948.12.TIEXsq&id=35870048695
>
> http://item.taobao.com/item.htm?spm=a230r.1.14.4.VdTsRT&id=21105435798&ns=1&abbucket=3#detail
>
>
>
> Has anybody done this... am I reinventing a triangular wheel here,
> is it doomed to failure?  Suggestions on suitable adhesive... maybe
> just spray on contact adhesive might work, it's a pretty big flat
> contact area.
>
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