--- In
Homebrew_PCBs@yahoogroups.com, "gettingalongwouldbenice"
<gettingalongwouldbenice@y...> wrote:
>
> I finally got my hands on the sheet teflon.
> I posted a photo in the electrostatic page teflon.jpg.
> That's a TQFP64 SMT land pattern at 20 mil pin pitch.
> As you can see, there are some horrible problems.
>
> As expected the toner makes a very fine unfused image.
> And virtually all the toner irons on to the board where it
> makes contact.
>
> Problem 1 is that the toner won't stay put.
> It wants to jump all over the place. Slightest
> jarring of the page makes everything fuzzy.
> I'm hopeful that this problem
> can be fixed by coating the page with something to make
> it slightly conductive. Slipping a strip of aluminum foil
> between the teflon and the paper carrier page did wonders
> for the image from the drum, but just pulling it out of
> the printer jarrs it enough for the toner to spread.
>
> It's a pita to put the fuser back, but I should run some
> experiments fusing the image.
>
> Problem 2 is that the teflon is wrinkled. It's 0.002" sheet
> taped to a paper carrier. There are slight deformatons in it from
> manufacturing processes and being stored on a roll.
> Heating it to 400F causes major deformations. Has localized
> shrinkage that makes for a very uneven surface. It's a lot better at
> 300F, but I don't think there's
> any chance of using the sheet more than once. I was hoping
> teflon would be dimensionally stable under heat.
>
> I don't have a laminator, but that might help if problem 1
> gets solved.
>
> So, I'm disappointed. Anybody got any really bright ideas?
> Could use one about now.
well, probably an obvious one but what about bonding the teflon to a
more stable carrier. heavy paper might do it. the adhesive would
need to be temperature stable.
phil