Homebrew PCBs

--- In Homebrew_PCBs@yahoogroups.com, "dagmargoodboat"
<dagmargoodboat@...> wrote:
>
> (Oops - a "tab" and a <cr> sent my first post before completion!)

<snip>

<delurking>
Greetings all,
I see the first half of this post was lost, and that
Yahoo kindly reformatted my carefully-formatted 2nd
part as well.  Sorry!  I'll repeat here...

INTRO
Hi! I've been making the occasional toner transfer (TT)
board for >12 yrs, mostly with Press-N-Peel Blue and
a household iron.  Lately I've used Staples' Picture
Paper, per Thomas Goatee.

After cruising the archives here, I procurred a GBC
DocuSeal 95 laminator for $5, hoping to reduce
some of the process variables.

Using Staples' Picture Paper, my first try through
the laminator gave a perfect--and I do mean perfect--
transfer of a junk board with some 0.006" lines onto
0.020" double-sided circuit board.  Very nice.

The second attempt--on a real board to be etched--
was not perfect though.  Traces had a few gaps, and
some pitted / ragged edges.  Mostly okay, but not
acceptable.  I'm using 0402 parts, and need fine
lines. Subsequent trials have not improved.

Accordingly, I've finally been moved to
troubleshooting the matter with rigor, seeking
a more definitive answer.

My first thought was insufficient heat; the GBC
heating stage measures 118 C (245 F) on its
"laminate" setting, 145 C (285 F) on "foil".

The GBC's "laminate" setting wasn't hot enough to
transfer any toner at all, but "foil" worked quite
well. I was surprised, but 145 C is apparently
ample.  Increasing the temp. as high as 160 C
(320 F) doesn't affect or improve the transfer.

My troubleshooting is ongoing; the purpose of
this post is to share the toner melting points
I've measured.

TONER MELTING POINT MEASUREMENT


EQUIPMENT
Household iron, instrumented with a thermocouple,
and insulated to keep the heel plate temp. decently
isothermal.


PRINTERS
. 1)  HP LaserJet 5L, original cartridge
. 2)  Samgsung 1710, cartridge refilled with recommended
.                    toner from TonerKits.com

PROCEDURE
  I made one print from each printer, on separate sheets
from the same package of Staples' paper, then measured:

.   a) the minimum temperature at which I could smear the
.      pattern with the iron (i.e., toner flows)
.   b) the minimum temperature at which decorative foil
.      would transfer to the toner (i.e. toner is 'tacky')

(Rather than nail the exact melting points, I took data
until the actual temp. was reasonably bracketed, hence
the ranges reported below.)


RESULTS
=======
.                    HP LJ-5L                Samsung
.                ----------------        ----------------
toner            99 C < t < 106 C        98 C < t < 101 C
smears @        (210F < t < 222F)       (209F < t < 213F)

foil             107 C < t < 112 C       78 C < t < 83 C
sticks/          (225F < t < 233F)      (172F < t < 181F)
transfers

Given the commonly recommended fusing temps, I was surprised
at these low melting points, and think it may have
broader implications for the fusing problem in general.

Sorry for the newbie posting hiccups, and hope this version's
format survives better.

  Best,
  James