Homebrew PCBs

I have the same results.
Thermal contraction tries to rip the edges away. My solution is to
print a wide black strip all around the PCB, you don't care if all of
it comes out well but if wide enough it can withstand the pull, or at
least "take the hit". With this broad black line i have no more
problems. If you do several boards on one piece you only need one
overall "guard trace" around them. Sometimes i leave the wide outline
on the PCB on purpose, it is useful for a low impedance ground trace,
for example to clip scope probe ground leads somewhere.

I also see the wrinkling when put in water, but i believe this is
different to the thermal expansion/contraction. Paper tends to get a
lot larger when taking up water. The wrinkles only appear in places
with no trace, and don't seem to rip traces off. I use hot water, and
i sand or scratch the paper backside after fusing to open the surface
for quicker wetting. It is different to your fingers getting all
wrinkly by the way, this is because the salty water inside you is
drawn out into the less salty water on the outside, not because of
your skin expanding (although it may do that, too). I'm told if you
bathe in very salty water (e.g. dead sea) this effect does not occur.
I am not certain if this is a myth or true.

About the "shiny surface" paper, i know exactly what you mean. But
there is an advantage to this additional effort. The shiny surface is
much smoother than the clay on matte paper. This gives better
resolution overall, and less white residue for component legend. I now
use this shiny paper for all boards. There is a quick and efficient
way to remove the residue by the way, without getting your fingers
wrinkly ;-). Take a piece of polyurethane foam (foam rubber, synthetic
sponge), and use that to rub the residue off. Much more efficient than
your finger, and no wear and tear on same.

ST

On Jan 13, 2008 3:02 PM, Lez <lez.briddon@...> wrote:
> Just tried some UK asda paper, 2.97 25 sheets, seems 'ok' but the shiny
> surface sticks to the copper as well as the toner making a little more thumb
> work needed, but on the good side the actual paper is quite easy to remove
> and wicks water up quickly.
>
> paper is ''asda a4 glossy inkjet photo paper '' 25 sheets 180gsm
>
>
> I also have had my old problem of the paper 'jumping' off the pcb when it
> hits the coldwater, like the pcb shrinks in the cold water, should I try hot
> water? (all my papers do this, I think its my pcb material to blame, very
> 'expansive' when hot)
> (This is after an iron at cotton setting for 60 seconds)
>
> If the paper does not 'jump off' it wrinkles like a wave shape leaving
> toner/no toner/toner along the edges.
>
> Its an effect like you see on your fingertips if you have spent along time
> in the bath/shower
>
> Like I said all my papers have done this, the asda is no worse, but cheaper
> to buy.
>
>
> [Non-text portions of this message have been removed]
>
>
>
>
> Be sure to visit the group home and check for new Links, Files, and Photos:
> http://groups.yahoo.com/group/Homebrew_PCBs
> Yahoo! Groups Links
>
>
>
>
>