Homebrew PCBs

First, some photos: http://www.delorie.com/pcb/lab/

I wanted to try this in case I needed it in the future, and this board
was simple enough that it didn't matter if it worked or not.  Got to
remember to avoid the thin bits of mask between pads, though - they
easily come loose.

The discovery is about laminating 1/16" (63 mil) clad.  Usually my
laminator doesn't like accepting these, I have to push pretty hard to
get it to "catch" and roll through.  This time, I was trying to avoid
air bubbles in the mask.  Usually I wrap the film around the leading
edge of the board, and hold the trailing edge tight, so that air
bubbles won't get trapped.  In this case, I didn't quite have enough
film (it was a scrap) so I put the pcb on a piece of paper, leaving
most of the paper on the leading edge side, and taped the film over it
(taped it to the paper, not the pcb).  That way, the laminator could
grab the paper and I had time to pick up the trailing edge of the film
and hold it while the laminator pulled in the paper/film/pcb.

I was expecting problems when the pcb got to the rollers, but it got
drawn in just as smoothly as the paper!  There was a bump when it
exited, but the lamination was nearly perfect.  So I'm thinking, when
you do 1/16 clad, leave enough of the TT/film/whatever paper on the
leading edge that you can fold it over enough to tuck under the pcb's
edge, so that the laminator can grab the fold and draw the PCB in.

Anyway, back to the mask... after developing, I put it under the UV
again for 3x my normal exposure to harden it.  Any idea how it will
hold up to soldering?  It's Riston.

Great stuff as usual. There is an instructables entry about a guy who did this as well. Might be of use to you or maybe even worth asking him some questions. 

http://www.instructables.com/id/Killer-PCBs/

I am looking to test this idea out myself soon enough. It seems very practical for prototyping and would really help with soldering surface mount. 

Trev

Some feedback about etch resist as solder mask... it's pretty but it
melts at soldering temperature.

--- In Homebrew_PCBs@yahoogroups.com, DJ Delorie <dj@...> wrote:
>
> 
> Some feedback about etch resist as solder mask... it's pretty but it
> melts at soldering temperature.
>

That is what I was thinking that the Heat would melt the resist, as I use positive resist boards and have left the Positive Resist on and soldered the board and the resist just melts away when heated with the soldering iron.  He was doing solder paste and reflow in a oven but still I would think that all the resist would break down in the heat of the oven.

Ben

"Ben L" <bhleavi@...> writes:
> oven but still I would think that all the resist would break down in
> the heat of the oven.

I've noticed the riston will bubble up if I overheat it with the hot
air gun (all the more reason to use a known-temp laminator control :)

It doesn't seem *that* bad though.  If you solder with the usual quick
touch, and don't actually hit the film with the iron, it seems to stay
put.  I don't think they'll survive the hotplate though.  I can try a
scrap later.

It does somewhat keep the solder in place, too.  And still looks
pretty.  I liquid-tinned the boards before putting the film on, they
all have a sort of silvery-blue theme.

They do sell actual soldermask film which you can apply and
photoprocess much like this.

I don't know where you can get it, just wanted to make sure you know about it.

ST

On Thu, Dec 31, 2009 at 6:02 AM, DJ Delorie <dj@delorie.com> wrote:
>
> "Ben L" <bhleavi@...> writes:
>> oven but still I would think that all the resist would break down in
>> the heat of the oven.
>
> I've noticed the riston will bubble up if I overheat it with the hot
> air gun (all the more reason to use a known-temp laminator control :)
>
> It doesn't seem *that* bad though.  If you solder with the usual quick
> touch, and don't actually hit the film with the iron, it seems to stay
> put.  I don't think they'll survive the hotplate though.  I can try a
> scrap later.
>
> It does somewhat keep the solder in place, too.  And still looks
> pretty.  I liquid-tinned the boards before putting the film on, they
> all have a sort of silvery-blue theme.
>
>

Stefan Trethan <stefan_trethan@...> writes:
> They do sell actual soldermask film which you can apply and
> photoprocess much like this.

I know, but it's a lot more expensive than etch resist, and I didn't
have any but did have riston.

(This list is about doing things cheaply, right? :)

--- In Homebrew_PCBs@yahoogroups.com, Stefan Trethan <stefan_trethan@...> wrote:
>
> They do sell actual soldermask film which you can apply and
> photoprocess much like this.
> 
> I don't know where you can get it, just wanted to make sure you know about it.
> 
> ST
>

Think & Tinker www.thinktink.com sells the Dry Film Soldermask, The Soldermask runs about 4 times the price of the Resist I think.

Also Mouser is selling small Qty of the Resist thru M G Chemical.

There is a guy on Ebay that sells cut pieces of the Dry Film Resist, I got some of that to try out the Resist. Will be cheaper than buying the precoated Series 600 M G Chemcial boards that I have been using if I can get a good reliable process down on getting it on the board.  I'll try the Wet method first since I don't have a laminator.  Should have giving it a try this week while I was off work but still have not gotten around to it.

Ben

Ben

> 
> (This list is about doing things cheaply, right? :)
>

GREAT!!!  That means "I" am on the right list - I'm CHEAP!! :):)

Ken

--- In Homebrew_PCBs@yahoogroups.com, DJ Delorie <dj@...> wrote:
>
> 
> First, some photos: http://www.delorie.com/pcb/lab/
> 
> I wanted to try this in case I needed it in the future, and this board
> was simple enough that it didn't matter if it worked or not.  Got to
> remember to avoid the thin bits of mask between pads, though - they
> easily come loose.
> 
> The discovery is about laminating 1/16" (63 mil) clad.  Usually my
> laminator doesn't like accepting these, I have to push pretty hard to
> get it to "catch" and roll through.  This time, I was trying to avoid
> air bubbles in the mask.  Usually I wrap the film around the leading
> edge of the board, and hold the trailing edge tight, so that air
> bubbles won't get trapped.  In this case, I didn't quite have enough
> film (it was a scrap) so I put the pcb on a piece of paper, leaving
> most of the paper on the leading edge side, and taped the film over it
> (taped it to the paper, not the pcb).  That way, the laminator could
> grab the paper and I had time to pick up the trailing edge of the film
> and hold it while the laminator pulled in the paper/film/pcb.
> 
> I was expecting problems when the pcb got to the rollers, but it got
> drawn in just as smoothly as the paper!  There was a bump when it
> exited, but the lamination was nearly perfect.  So I'm thinking, when
> you do 1/16 clad, leave enough of the TT/film/whatever paper on the
> leading edge that you can fold it over enough to tuck under the pcb's
> edge, so that the laminator can grab the fold and draw the PCB in.
> 
Try cold rolling through the laminator first. I find this pushs the air out before hot laminating.

> Anyway, back to the mask... after developing, I put it under the UV
> again for 3x my normal exposure to harden it.  Any idea how it will
> hold up to soldering?  It's Riston.
>

"David B" <davidlbarber@...> writes:
> > I was expecting problems when the pcb got to the rollers, but it got
>
> Try cold rolling through the laminator first. I find this pushs the
> air out before hot laminating.

The discovery isn't about air bubbles, it's about getting 1/16" PCBs
to *fit* into the laminator.  If I hold the end of the film up as it's
entering, I usually don't have problems with air bubbles.  *Steam*
bubbles are a different story - but laminating below 212F seems to
solve that problem.