--- In
Homebrew_PCBs@yahoogroups.com, Mark Lerman <mlerman@...> wrote:
>
> The problem with DLP is that larger boards are very inconsistent, and
> even smaller ones give variable results.
I'm not sure what you mean by "inconsistent". I have done some tests on various laser printers where I printed a 1" grid of lines. I then turn one film over and lay it over the other one on a light table, so see how accurate the registration is. My experience is that almost every printer has at least a tenth of an inch error somewhere on the page! The stuff I am now doing with solder stencils requires .010" apertures, so the two films of the two sides need to line up extremely well. (I etch mirror image patterns in from both sides simultaneously to reduce sideways etching.) I actually have a problem because the program I wrote to convert Gerber to raster does the mirror-flip before plotting, and rounding processes in the program shift the apertures by one mil on the different sides. I can clearly see this as an offset between the apertures coming in from opposite sides. It doesn't really cause any problem in the solder stencil, but it is easily visible under the microscope. But, making these master artwork on a laser printer would be a fool's mission!
The boards these stencils are for have chips with lead pitch down to .4mm, and some of them are a foot wide! So, I need something with a LOT more accuracy.
Jon