Homebrew PCBs

Ok I am seeing the same problem with this 'working' paper as my other
papers, and now I'm on a laminator, not an iron....

My problem is when I heat the paper/toner onto the board, all looks
fine, as the board cools, the paper 'bubbles' up in some areas.

This is more noticeable on larger (say 6*5inch) boards than smaller,
say 3*3, on the smaller sizes, the paper sometimes just 'pops' or
lifts off.

Am I the only one suffering this?

It cant be too much heat, the new laminator is so 'warm' its not
melting the toner properly, but I still see the expansion.

I'm on a thick (1.6mm?) fibreglass board

I thought it was my water was too cold and was a 'shock' to the board,
but just letting it air-cool is causing it also.

-- 

Lez

On Thu, 01 Feb 2007 19:35:37 +0100, Lez <lez.briddon@...> wrote:

> Ok I am seeing the same problem with this 'working' paper as my other
> papers, and now I'm on a laminator, not an iron....
> My problem is when I heat the paper/toner onto the board, all looks
> fine, as the board cools, the paper 'bubbles' up in some areas.
> This is more noticeable on larger (say 6*5inch) boards than smaller,
> say 3*3, on the smaller sizes, the paper sometimes just 'pops' or
> lifts off.
> Am I the only one suffering this?
> It cant be too much heat, the new laminator is so 'warm' its not
> melting the toner properly, but I still see the expansion.
> I'm on a thick (1.6mm?) fibreglass board
> I thought it was my water was too cold and was a 'shock' to the board,
> but just letting it air-cool is causing it also.


I see something similar with my paper, it tends to rip off the board  
outline if i do not draw a second, wide, outline around it to anchor the  
paper to the board. I always thought the paper is shrinking and causing  
the problem this way.

You can try several things. Run the paper through your laminator a few  
times before use to "set" the size.
After printing, scratch the back of the paper with sandpaper or a brass  
brush to open the surface and allow water faster access.
Draw a wide outline around the actual board outline to guard it. Use  
another paper.

I throw the boards into water still hot, but i have also let it cool with  
the same result.

ST

>
> I see something similar with my paper, it tends to rip off the board
> outline if i do not draw a second, wide, outline around it to anchor the
> paper to the board. I always thought the paper is shrinking and causing
> the problem this way.

I'm sure it not the paper, got to be the copper, but I cant see why
only a few of us (well 2!) seem to see this.

Unless its more noticeable with some papers than others, and we have
the bad stuff........

"Stefan Trethan" <stefan_trethan@...> writes:
> I see something similar with my paper, it tends to rip off the board
> outline if i do not draw a second, wide, outline around it to anchor
> the paper to the board. I always thought the paper is shrinking and
> causing the problem this way.

I've gotten in the habit of outlining my boards too.  For the green
TRF, it also helps reduce wrinkles.

On Thu, 01 Feb 2007 20:44:04 +0100, Lez <lez.briddon@...> wrote:

> I'm sure it not the paper, got to be the copper


no, remember that's stuck to glass fibers.

ST

On 01/02/07, Stefan Trethan <stefan_trethan@...> wrote:
> On Thu, 01 Feb 2007 20:44:04 +0100, Lez <lez.briddon@...> wrote:
>
> > I'm sure it not the paper, got to be the copper
>
>
> no, remember that's stuck to glass fibers.

And that does not expand?

(looks for tape measure and a hot iron........)

On Thu, 01 Feb 2007 23:13:51 +0100, Lez <lez.briddon@...> wrote:

>
>> no, remember that's stuck to glass fibers.
> And that does not expand?


Sure does, but paper seems to expand or contract much more. Try it.

The expansion coefficient of copper is mostly irrelevant because the PCB  
is much thicker and would just stretch it (i have not noticed any bending  
of the boards, although single-sided PCB stock sometimes comes bent  
regardless of temperature.

I do not know the expansion coefficient of paper, i think it depends very  
much on the paper and also moisture. Wood ranges from somewhere in the  
ballpark of FR4 to maybe 10 times as much, but i suspect it is even more  
with paper. But the thing is, paper shrinks when you dry it, FR4 does not  
;-)
Put a drop of water on paper and see the ripples from expansion (i should  
know - stripped lots of wallpaper today).

ST