Homebrew PCBs

Zoran A. Scepanovic wrote:

> Zdravo kirilian2351,
> 
>   Sunday, February 8, 2004, 12:55:43 AM, ti rece:
> 
> k> I am wanting to build a UV light box.  I have read as many internet 
> k> articles as I could find on the subject.  Some articles will 
> k> recommend certain bulbs while other articles will say to stay away 
> k> from those that were recommended.  What is the best bulb to use that 
> k> is easily obtainable?  I have read an article that suggested using 
> k> bug zapper bulbs.  My local Home Depot carries 15W and 40W versions 
> k> of the replacement bulbs for the Zapper models.  Would this type of 
> k> bulb work?  I have also read about breaking the glass shell of a 
> k> mercury vapor bulb and using the internal tube as a UV source.  I 
> k> don't plan to make large circuit boards (no larger than 6" square).
> 
>   DO NOT break the outer glass shell of a mercury vapour lamp! It will radiate a lot of short wave UV (UV-A) which is dangerous for eyes and skin, and it generates lot of ozone (O3). Good results could be obtained without breaking the outer glass shell.


I too use a HID mercury lamp. I did not break the shell after learning the 
dangers this can have. The other reason keeping the shell is because the 
short wave UV gained from removing the shell is useless since the window 
glass and/or polyester phototool will absorb all this energy. The only 
benefit I can think of would be less light undercutting the photomask due 
to the smaller sized light source. I've experienced problems with light 
undercut using a exposure units filled with fluro tubes mounted 5 cm from 
the PCB.
Using my phosphorized mercury vapor lamp at 30 cm from the PCB, the detail 
of the developed photoresist image is completely limited by my printer 
quality. Under a microscope the resist pattern clearly defines the markings 
of individual inkjet ink droplets that are visible on the transparency 
around line edges of the artwork.

To give you an idea, here are two photos comparing the resist pattern after 
developing and the photomask used to create the pattern. This is not a 
particularly good match between the photomask and resist pattern but its 
just some photos I had takes some time ago.

http://members.optusnet.com.au/eseychell/pictures/Epson_inkjet_film.jpg
http://members.optusnet.com.au/eseychell/pictures/resist_image_on_copper.jpg