As Harvey just said, I think it would be easier to just glue two thin boards together to make a ds board. They don't even have to be the same thickness. If you want to get cute you might even make both pieces from ds stock and leave a lot of copper on the "hidden" side of each. Coat some solder paste on the copper, clamp it and put it in the oven to solder the two boards together. This (and gluing) might be a problem if you reflow the boards, but you might be able get some high temperature epoxy.
Mark
-----Original Message-----
>From: Mark Lerman <mlerman@...>
>Sent: May 23, 2010 11:29 AM
>To: Homebrew_PCBs@yahoogroups.com
>Subject: [Homebrew_PCBs] DLP Double Sided Update
>
>Well, I've done some tests trying it the easy way, and while it
>SHOULD work, it doesn't, at least not consistently. The problem is
>that both the carrier and the board are (obviously) much thicker than
>paper, and when they hit the drum/transfer roller interface there is
>a slight (and variable) delay as first the carrier and then the board
>go through. There are also problems in the X axis because the carrier
>"grabs" slightly when it hits the drum and has a tendency to get a
>little out of parallel to the motion axis. In theory we could wait
>till the pcb (or a "header" of equal thickness) is under the drum
>before telling it to print. However, this may create problems in the
>charging timing since the printer does not expect there to be a board
>present at that time. The X axis problem could be handled with a
>better and longer carrier guide, but too much friction would create
>its own problems.
>
>There is no reason that DLP can't do ds boards, but I'm far from sure
>that the mechanics of your typical laser printer can be "bulked up"
>enough mechanically to produce consistent results. Probably the best
>way to do ds DLP would be to make a flatbed laser system, much as has
>been done for inkjets. Print one side, put it in an oven to fix the
>toner, flip it and print the other side.
>
>This would also be the way to go for a commercial product - anyone
>interested in collaborating?
>
>Mark
>
>
>
>
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