Homebrew PCBs

tanning tubes (easy to get in europe) works great.

I'm glad to hear (read) that more and more dry film users are here.
for over a couple of years im working with it and found out that a 
normal exposure unit isnt wath you want with negative films.
Specialy with small smt pwb, the lines that are close together melt 
together with negative film.
Or with positive film they get real thin.
I lower the 12 tube's to 60/70cm 25in. and close to te glassplate a 
collimar grid like think&thinkers idea.
i will shoot some pictures this week of it

gr Roel


--- In Homebrew_PCBs@yahoogroups.com, Adam Seychell <a_seychell@...> 
wrote:
>
> lcdpublishing wrote:
> > Hi guys,
> > 
> > I got a chance to do some more experimenting with the dry film 
photo 
> > process.  I did a "step" test doing various exposure times and 
found 
> > out that the UV lamp I bought for this purpose simply isn't 
powerful 
> > enough.  I have a regular light bulb of the right color range and 
> > tried that with much better results - exposure time through 
> > transparncy of only 3 minutes.  I have much more experimenting to 
do 
> > to get it better, but was able to make my first board all the way 
> > through the etching process.
> 
> Most people use those UV "insect zapper" florescent tubes, also 
known as 
> black lights ("BL") which emit a bluey violet colour. Don't waste 
your 
> money on filtered black lights used for special effects. You can 
get 20W 
> compact florescent blacklight lamps too these days.
> 
> > 
> > 1) When I used to have a black and white dark room, I discovered 
> > that the developer would last a long time and could be reused 
over 
> > and over again.  
> 
> There is no shelf life for sodium carbonate solutions, other than 
water 
> evaporation. The Na2CO3 is obviously consumed during development, 
but 
> its actually very small. The data sheet for my resists specifies a 
> developer loading capacity of about 9.4E-6 m^3 of resist per litre 
of 
> developer. For your average 40um dryfilm resist and double sided 
PCB 
> with 50% trace coverage then that works out to be 0.23 m^2 of PCB 
area 
> (485 x 485mm square) per litre of developer.
> 
> 
> > 2) While doing the exposure / developer tests, I realized very 
> > quickly just how tough this resist is.  I was scrubbing with a 
> > scotch brite pad vigorously without removing the resist. 
> 
> That's normal. You strip it off in 2~5% NaOH, in 5 minutes at room 
temp. 
>   Don't waste your energy scrubbing it off, just let the NaOH do 
its 
> work and it will lift off before your eyes.
>