Homebrew PCBs

On Sat, 11 Oct 2008 01:50:08 -0000, you wrote:

>--- In Homebrew_PCBs@yahoogroups.com, "warrenbrayshaw"
><warrenbrayshaw@...> wrote:
>>
>> "pixelcanvas"  wrote:
>> >
>> 
>> > The stuff I'm testing is this:
>> > http://www.es.co.th/Detail_eng.asp?Prod=WARA%2DDRYFILM
>> > 
>> > I get it locally (I live in Bangkok), and unfortunately the
>> > instructions are in Thai... my girlfriend helped me out with it but I
>> > still think there may be something wrong with them... 
>> > 
>> 
>> As this appears to be Wara product try the manufacturers web site to
>> confirm your translation was correct.
>> 
>> http://www.warapcb.com/dryfilm.php
>> 
>> All the best
>
>Yes, the translation is correct, but I have serious dubts about it's
>usefulness. For example it does say to use a 100W light bulb for 15
>minutes to expose the film, and I know for a fact that is way too
>little time. So I think I should take those instructions with a pretty
>large grain of salt...
>
>Harvey, I think what you are saying about the bottom of the film not
>being exposed may be correct.
>I'm going to try to get an UV light, and expose a test board at
>different times, I'll place a piece of cardboard over it and move it
>to the side every 15 minutes or so to expose more of the board. Then
>I'll see what exposure time works best.

For commercially available boards (GC electronics), board about 8
inches from the lamps, lamps 18 inch 15 watt black lamp fluorescent
(not what's recommended, I think), I get about 3 minutes exposure.
Multiple lamps seems to help.  I've got a homemade vacuum frame
(particle board and a shop vac with a lot of holes in the particle
board) and I use thin upholstery vinyl (transparent, of course) over
the board.

a 100 watt lamp is mostly red and yellow.  If it's supposed to be
exposed under UV or blue/white light, then you might see a recommended
wavelength in the resist technical characteristics.

The normal photoresist polymerizes (or de polymerizes) from the top
down.

Harvey

>
>Thanks  lot for the suggestions so far.
>> Warren
>>
>