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Subject: Re: [Homebrew_PCBs] RE: Home made double side PCB with solder mask and silk screen!

From: ctech <ctech4285@...>
Date: 2014-03-01

sorry for the late response arggg yahoo groups mail delivery!!

>Just asking...that UV paint has a "short" shelf life, doesn't it
no, I mix 200g up in the spray gun and it last me over 6 months.
Its properties seem to change a little bit, every now and then I have to adjust exposure time up or down by 2 minutes.

>Firstly, that he
managed to dry it before UV curing.
The trick is thin code (but still think enough that you can barley see throw the board) and dry it in a controlled temperature environment. Tosters do not work. The paint will start curing when you heat it up too much and the point between dry enough to apply the mask and curing is very close ~5-10deg C
(105-115deg it starts to cure, higher and it's all crap) when the color tone changes slightly its junk

Also I just dry the pain enough to apply the mask, it is a little bit sticky but the mask can be moved a little bit, and the paint does stick a little to the mask after curing so masks are one time use only.

>And I
"baked" it in the oven at 180 degrees C for about 20 minutes and it "dried" ok, soft but tack-free.
No!!! way to hot. 105deg C 30 minutes, 115deg and I get crappy results. And index the mask when the board is just a little tacky

regards
Andreas




On Sat, Mar 1, 2014 at 5:24 AM, Russell Shaw <rjshaw@...> wrote:
 

On 01/03/14 16:56, James wrote:
>
>
> Well, I tried diluting and airbrushing some of the ink (white) but didn't have
> any success.
>
> Well, it dilutes ok. It airbrushes fine to a thin coating. And I "baked" it in
> the oven at 180 degrees C for about 20 minutes and it "dried" ok, soft but
> tack-free. Then I tried to cure it under the UV.
>
> But... it doesn't seem to cure under the UV at all, something is inhibiting it

Expose it in direct sunlight (it has a ∗lot∗ of UV). If it works, maybe your UV
source is no good.