Homebrew PCBs

> They do mention to use amonia 
> in the directions at there web site and I have not
> tried this yet.  

Ammonia is a degrease. I used to use it, but the fumes
are enough to cause insanity. So, I switched to
alcohol for decreasing. Also, I use denatured alcohol
of the highest purity I can find (I buy it at the
hardware store. It's not reagent grade, but it's clean
enough).


> Do you just spray on one coat of the resist? I am
> wondering about the 
> depth of the coat.

The way I've always done it is to spray it on.
However, the spray bottle I use I purchased at the
shop that sell cookware (Pots, pans and etc...). The
bottle has a pump built into it. I put the resist into
it, pump it up and then spray it as if it were a can
of spray paint: I start at the top of the card and
spray from left to right (I'm right handed...). Once I
reach the far right of the card, I move down the card
just a bit and then spray from right to left, move
down the card, spray left to right. I do this motion
again and again until I'm at the bottom of the card. I
then inspect the card for an even coat. If the coat is
not even, I do it again over the uneven coat using the
same motion. Ultimately, you end up with a super even
coat. However, be careful: There is a fine line
between just right and too much...

This motion gives a *really* even coat (Using this
method, you can make canned spray paint look like it
was applied using an airbrush...). 


> How do you expose, for how long?

I use quantity-4, 8-watt black lights. They emit UV
radiation around 325 to 350nM range which is the part
of the spectrum this type of resist reacts to. So, my
exposures are short: Depending on the size of the card
and the distance from the lamps, anywhere from 30
seconds to 5 minutes.   

> What are you using for a negative!

I use clear transparencies (The type that are used in
overhead projectors) that I purchase at office depot
and staples (And occasionally, walmart...) I print
using an HP 7350 deskjet at 1200 dpi. Also, I ALWAYS
use original HP black ink. I've found the ink in the
clone cartidges and the refills to be too thin. 



> your done, still 
> pretty much clear but just barely see the traces
> when tipped to the 
> side in the light?

This is a subjective question whose answer is function
of how good a persons eye sight is. So, the answer is
yes I can see it clearly, but at the same time, not
nearly as well as my 10 year old daughter (I'mm 44yrs
old...). 


Best regards


Marvin Dickens
Alpharetta, Georgia  

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