Homebrew PCBs

Volkan Sahin wrote:
>  
> 
> I've a working prototype. I'm using 150mw 405nm blue ray laser diode. 
> Without complicated optics I can get ~3 mil trace width/space. 
> Currently, I'm using  Dichromated PVA  based homemade photoresist.  The 
> problem is without  polygon mirror scanner, it is very slow but result 
> is impressive. The exposure time required for  1.5 mil spot is ~20 
> microseconds.
> Volkan
> 

What's wrong with using dry film photoresist ?
Its relatively cheap (under 10% cost of FR4 PCB material per unit area) 
easy to apply, fairly sensitive to 405nm, highly uniform and the ability 
to tent holes for the PTH panel plating method.

How are you positioning the laser ?
Would it be difficult to use parts off an laser printer to make a 
polygon mirror scanner. In that case only 1 axis movement is needed for 
the PCB.  My inkjet printer is currently the limiting factor for 
line/space widths, although 0.2mm (8mil) are quite reliable and adequate.