Homebrew PCBs

[image: Inline image 1]

NIce eh?

Andreas
Nicadrone.com


[Non-text portions of this message have been removed]

Just asking...that UV paint has a "short" shelf life, doesn't it?

Charlie

On Wed, 26 Feb 2014 11:40:46 -0600 ctech <ctech4285@...> writes:
  
Thanks javierete,

The UV paint is the same used for the solder mask and etching and you can
get it for this here:
http://www.ebay.com/sch/m.html?_odkw=&_osacat=0&_armrs=1&_ssn=goldpart&_t
rksid=p2046732.m570.l1313.TR12.TRC2.A0.H0.Xpcb+uv&_nkw=pcb+uv&_sacat=0&_f
rom=R40


dilute the paint 50-75% alcohol pure without water and 25-50% paint. The
more paint the thicker paint layer you can make. 


I'll do some more work on the tutorial soon, I'll keep you posted

Regards
Andreas




On Tue, Feb 25, 2014 at 11:01 AM, <javierete@...> wrote:

  
Hi ctech


Your boards have very good finish, keep us posted!


How do you dilute the mask paint? And what about the silkscreen? BTW I
think you didn't finish the tutorial so I'll stay tuned on your webpage.


Regards!




[Non-text portions of this message have been removed]

On 27/02/14 13:33, n0tt1@... wrote:
>
> Just asking...that UV paint has a "short" shelf life, doesn't it?
>

Not that I'm aware of.  I have a couple 100g tubs of it kicking around, 
one has been here for well over a year and looks, smells, spreads, and 
cures the same as it always did.

That said, I have only really had good luck with some red stuff I got in 
10cc lots, I probably had that kicking around for about 9 months before 
I ran out, and it worked just fine.  The white and blue I have large 
amounts of is quite hard to use, at least in the way I've been doing it 
(I've described here before).

I'm surprised that ctech got such good results.  Firstly, that he 
managed to dry it before UV curing. The only one I've seen that can be 
dried was the blue, the others don't really dry (before UV cure) at all, 
at least not air-dry, no matter how long you leave it. Secondly that he 
thinned it with alcohol, I'm sure I tried that once and it didn't work.  
Maybe it's the thinning and air-brushing that does the trick, perhaps 
such a thin coating will dry (at which point it would be MUCH easier to 
work with).

But certainly I think I will give it another go in the weekend, thin 
some out the same as ctech did and load it in my air brush to see if I 
can get the amazing results he did.

Thanks for that info, James.  

I'm thinking the stuff really *should* dry.  Like you said,
it *would* be a lot easier to work with.  Maybe baking
in an oven? <Not in the wife's kitchen oven!!! :0) >

On Thu, 27 Feb 2014 14:08:50 +1300 James <bitsyboffin@...> writes:
  
On 27/02/14 13:33, n0tt1@... wrote:

  
Just asking...that UV paint has a "short" shelf life, doesn't it?


Not that I'm aware of.  I have a couple 100g tubs of it kicking around,
one has been here for well over a year and looks, smells, spreads, and
cures the same as it always did.

That said, I have only really had good luck with some red stuff I got in
10cc lots, I probably had that kicking around for about 9 months before I
ran out, and it worked just fine.  The white and blue I have large
amounts of is quite hard to use, at least in the way I've been doing it
(I've described here before).

I'm surprised that ctech got such good results.  Firstly, that he managed
to dry it before UV curing. The only one I've seen that can be dried was
the blue, the others don't really dry (before UV cure) at all, at least
not air-dry, no matter how long you leave it.  Secondly that he thinned
it with alcohol, I'm sure I tried that once and it didn't work.  Maybe
it's the thinning and air-brushing that does the trick, perhaps such a
thin coating will dry (at which point it would be MUCH easier to work
with).

But certainly I think I will give it another go in the weekend, thin some
out the same as ctech did and load it in my air brush to see if I can get
the amazing results he did.



[Non-text portions of this message have been removed]

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, it can easily be scraped just by gently rubbing your 
finger nail on it or even just pressing your finger nail on it, there is 
no difference between masked area and exposed area. And meths on a cloth 
just wipes the board clean with no effort at all.

The alcohol I'm using is just Methlyated Spirits (>= 95% ethanol, and 
the rest water with a tiny amount of a bittering agent)
The UV cure I gave up at 30 minutes, no change in the hardness or 
fastness was particularly noticable, it was still "soft".
Hmm, I notice on the referenced site ( 
http://nicadrone.com/index.php?id_cms=24&controller=cms ):
   "Dry the paint in a reflow oven, drying temperature influences 
exposure time drastically above 100C "
it doesn't say in which direction it influences, perhaps my drying 
temperature is too hot and this messes the exposure?

So in short it would be really great if Andreas (ctech) could give some 
brief details...

   1. your board shows a soldermask (green) and a silkscreen (white), 
which paints exactly did you use for these?  Just the ebay ones, one 
green and one white?
   2. what type of alcohol did you use specifically, ethanol, 
isopropanol, methanol...?
   3. what temperature and time did you "bake" the board at to dry it?
   4. are you doing anything else before exposure?
   5. how long as you exposing the board for to the UV under the mask?
   6. what type of UV source are you using, and are you using any fancy 
things like a vacuum system?
   7. how are you developing it after exposure exactly, with the same 
alcohol, with sodium hydroxide...?

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.

Russell Shaw wrote:
>  
>
> Expose it in direct sunlight (it has a *lot* of UV). If it works, 
> maybe your UV
> source is no good
>

I will, but my UV box has cured it normally (without the thinning and 
baking) fine, rather unlikely that every single one of the 200 leds has 
lost it's UV emitting power since I last used it (and yes I did check 
they are turning on) :-)

ctech wrote:
>  
> (105-115deg it starts to cure, higher and it's all crap) when the 
> color tone changes slightly its junk
>

I tried at 110 degrees 30 mins, no difference, touch dry, soft, doesn't 
UV cure.  No colour change is  observed at any temperature.

Maybe my ink is just different to your ink.

I will try curing an alcohol diluted sample today as I normally would 
under cellophane without baking and see if it can still be cured or if 
it is the changes induced by the alcohol thinning which causes the problem.

>
> 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.
Hmmm.  Curiouser and curiouser.  If the paint is sticking to the mask, 
why is it not bonding the mask to the board strongly I wonder, as it 
normally would.  What are you using for the mask?

On 02/03/14 11:38, James Sleeman wrote:
> I will try curing an alcohol diluted sample today as I normally would 
> under cellophane without baking and see if it can still be cured or if 
> it is the changes induced by the alcohol thinning which causes the 
> problem.

I can confirm that the diluted airbrushed coating does UV cure when wet 
and covered with the usual cellophane - although I only did a brief 
exposure to check so I could clean it off again, I didn't do a long 
exposure yet so don't know if the other properties of hardness, non 
conductivity, soldering heat resistance etc remain.

So that I guess leaves two possibles for the non-exposure of the "dried" 
one.  Heat damaging the UV cure properties.  Or the "drying" meaning 
that the oxygen removal of the cellophane layer is not possible (due to 
not sticking to it as it does when wet) - as we know, this stuff doesn't 
normally UV cure in the presence of oxygen, at least when wet.

Hmm.  I don't have an oven that can accurately hold 100 degrees C :-/