> Heres the theory .......
> 
> While browsing some other forums I came across someone who 
> stripped a dvd recorder and found the laser head could put 
> out around 250mw of power - enough to melt plastic/burn 
> paper. Further investigation showed these laser diodes are 
> good for between 80mw and 250mw output depending on the dvd burner.
> 
> The optics on these allow a fine focus
> 
> If photoresist boards can be "influenced" by these high 
> powered lasers then it could be a cheapish way of "printing" 
> directly onto PCBs.
> 
> Thoughts are to either have a rotary indexed table or maybe 
> reverse engineer a cheap laser printer and pass the board 
> through using the printer optics to raster print the image 
> onto the board.
> 
> Anyone know what happens to photoresist under a moderate 
> power laser beam ?
> 
> Dom


The resists are UV sensitive, what wavelength are DVD lasers?  Aren't they
infrared?

I guess you might be able to burn the resist off, but that's not quite what
you want.

The alternative is to use the laser directly onto film, develop & use that
as the mask.  This has been done forever, I used to make barcode masters for
printers like this, the laser was controlled by a BBC Micro, of all things.

As far as mechanicals, the usual method is to bounce the laser off a mirror.
I've seen film wrapped around a drum and rotated, with a mechanically
scanned laser (basically what you've suggested), or an X-Y table with the
laser fixed overhead.

The mirror method is the best.  Mirrors don't have much mass, so the 'scan
rate' is fast, and the amount of movement is tiny.  Bit tricky to get
accuracy though.

Tony

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