Homebrew PCBs

Hi all
  Well, after much frustration, I thought I would more or less 
abandon my efforts at using the toner transfer method, as my results, 
despite using the papers and machinery recommended just weren't 
working.
  i invested around $100 US in a screenprinting setup.  I was told 
this should have the detail to do the kinds of things I wanted to do 
(little 10 mil tracks).  For anyone accumstomed to screenprinting, I 
used a "12XX" pitch screen, said to be okay for fine details.
  I was also unimpressed.  Maybe it was because I chose an oil-based 
paint, but the graphic I got on my copper was smudgy and way too 
thick.  Damn.  Another failure.
  So, in frustration one night, I read someone's post where they had 
suggested that the temperature of the laminator (when used) should be 
very hot.  It made sense that the people experimenting with fusers 
would be having luck, since they are awfully hot.  I read that 
someone bypassed the thermostat in his laminator, but that it hadn't 
yeidled good results.  I thought "what the heck...the thing's more or 
less useless to me anyway" (because it only heats to 242 degrees F by 
itself).
  I bypassed it and let the thing heat.  It got up to 350 degrees 
before I stopped it, but not before running a board through a few 
times.  And wouldn't you know it...it came out pretty good.  (I 
changed my paper as well, to a "Sports Illustrated On Campus" issue I 
happen to have laying around).
  Because of the high heat, the cheap Wal Mart laminator's heating 
element had fried.  It no longer heated up.  So...I opened it up and 
found a metal housing around the rubber wheels, supported on set of 
high-heat resistant plastic legs.  I thought hmmm...what if I placed 
my iron right on top of the thing, and just heated it that way?  
Okay, it's cheasy in it's own regard, but it appears to work well.
  I think I might be noticing a slight deformation of the rollers, 
but I'm not positive.  In any case, the iron's high temp is around 
400 degrees F.  When pressed against the flat top of the laminator, 
it gets it up around 350.  With only 4 passes through, I actually had 
a board I was semi impressed with!  Finally! I'm trying to submit a 
picture in the photos area, should you want to be as cheap as me.  
Total cost of equipment:  laminator: (Henkel 9" electric, with 
cartoon duck wearing a hat on the box) $22, iron: $6.  Both purchased 
at Wal Mart.
  Now I have another question...just as I was about to submit my 
circuits to a board house...I need a method to align my top and 
bottom sides.  Is there anything anyone does that works especially 
well?  I have looked through the messages from the group and have 
heard of people taping both top and bottom on, and running them 
through at the same time.  That sounds like it would work, but how do 
you align them accurately?

Thanks
-Josh
Pullman, WA

--- In Homebrew_PCBs@yahoogroups.com, "joshdewinter" 
>   Now I have another question...just as I was about to submit my 
> circuits to a board house...I need a method to align my top and 
> bottom sides.  Is there anything anyone does that works especially 
> well?  I have looked through the messages from the group and have 
> heard of people taping both top and bottom on, and running them 
> through at the same time.  That sounds like it would work, but how 
do 
> you align them accurately?


I use the TT method and a laminator; although I haven't had the heat 
problems you had with my stock laminator.  It might have to do with 
the type of toner you are using.  I know a guy accross town that has 
been doing 1 sided boards OK with the same laminator (w/o modifying 
the heat element btw).  What kind of clad are you using? He does .5 - 
1 oz 1/16" stock in his --although the rigid roller transport does 
make a bit of noise doing so.

Most of the homebrew boards I do are double sided.  I print the top 
and bottom, (top mirrored) onto magazine paper making a few alignment 
crosses outside of the board boundary lines.  Under a bright desk 
lamp I align the crosses of the two pages with the toner sides in.  I 
use a glue stick and bind one of the edges to create an envelope.  
Sandwich the board into the envelope and insert the bound edge side 
in first into the laminator.  Make 2-3 passes in the same direction 
until the toner "tacks". After that you can clip off the bound edge 
and rotate and flip the board for a few passes until the toner has 
fastened to the copper clad.

The sandwich works pretty well on some pretty tight via pitches.  The 
possiblity of the skew from the bound edge justifying to the top or 
bottom turns out to be a non-event.  The rollers tend to align the 
binding with the center of the board when initially fed --as long as 
you insert the bound edge in first and fairly perpendicular to the 
board edge.

I have a write up on this in case you missed it in the TT links 
section...
http://myweb.cableone.net/wheedal/pcb.htm 

-Dal
(Pocatello, ID)

In a message dated 2/16/2004 9:31:08 PM Central Standard Time, 
joshdewinter@... writes:
Now I have another question...just as I was about to submit my 
circuits to a board house...I need a method to align my top and 
bottom sides.  Is there anything anyone does that works especially 
well?  I have looked through the messages from the group and have 
heard of people taping both top and bottom on, and running them 
through at the same time.  That sounds like it would work, but how do 
you align them accurately?
Drill the holes FIRST.

Or, if you MANUALLY drill all the holes (and break more $$ worth of bits than 
having the PC professionally-etched would cost!), and you MUST have the 
"copper pattern" present for drilling, then, using a light-box, place the negatives 
for top/bottom together, emulsion "inside", and tape them together along TWO 
sides, being careful to keep the "targets" aligned while taping.  THEN, just 
SLIP the sensitized blank between, clamp in a contact-printing-frame, and 
expose.  Remove, reverse, and repeat.  Now develop and etch.  

But, if redundant, if the holes are there FIRST, you could use the negatives 
"one at a time", and be CERTAIN of registration.   Yes, I realize drilling 
first would require either a home-brew CNC drilling rig, or the use of some kind 
of, say, self-adhesive pattern showing all the hole-centers.  And, sadly, most 
photo-copy machines will NOT sufficiently accurately copy a pattern for this 
purpose.  If you "draw" your pattern with an ink-jet printer, then print a 
copy on Avery 5265 (etc.) full-sheet adhesive-backed label-stock, and stick that 
to your blank, and drill.  The paper helps a tiny bit to "center" the bits as 
they enter the work.  A slow and kludgy method, but possible when the wallet 
is so severely challenged.          Jan Rowland


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