--- In
Homebrew_PCBs@yahoogroups.com, "Stefan Trethan"
<stefan_trethan@...> wrote:
>
> yes to all your questions.
>
> Edge problems are common. There can be many reasons, like
> contamination or bad surface preparation, which is tricky along the
> edges. Also, the pull from the paper shrinkage under heat is
greatest
> on the edges.
> I simply leave a solid copper border around the PCB (or around the
> outside of several if i make more than one on a panel), and cut it
> away later. It is the only sure way i have found. Apparently
> pre-shrinking the paper by running it through the laminator before
> printing has also brought relief to some.
∗∗∗ I tried this. Sure can get some serious shrinkage with a full
sheet. In fact, the paper ( HP Q2419A ) just wrinkled up. Obviously
wouldn't have worked at all.
I tried again this morning. Used a board about two inches
too big in each dimension - so there was an inch of dead space on
each side. I printed onto the HP glossy paper with the following
settings on my Brother MFC8600DN:
∗ resolution 1200HQ
∗ "transparency" ( figured those are smooth, and the printer might
put down more toner )
I cleaned the board with laquer thinner, and then with denatured
alcohol. Trimmed the printout a bit smaller than the board, and
taped it on with Scotch Magic tape.
Gave it 5 passes through the laminator (GBC 95P ) doused it in
cold water, and then let it in hot soapy water for about 15 minutes.
It mostly worked, although the corners were still crumbly, and I had
to spend about a half hour rolling the soft paper off.
Bits of toner were coming off in the ferric chloride bath. I
fished the board out and touched up with a fine-tip marker pen.
The circuit side etched faster than the back side, so when it was
done ( and the back side still had a ways to go ), I taped off the
whole circuit side with masking tape and finished etching off the
other side. It's not pretty, but it'll work.
Things I want to try next time:
∗ Sand the board. I think that a bit of a tooth will help the
toner stick. Say 400 or 600 grit.
∗ Try different temps. I think maybe the "foil" setting is a bit
hotter than needed. I noticed some pots on the circuit board in the
laminator. A lower temp should help with the shrinkage. Would like
it hot enough to melt the toner, but no hotter.
- Jerry