Homebrew PCBs

Hi Parag,

I can't answer your questions about the differences, but can tell you 
what did and didn't work for me.

I've had good success with HP Inkjet transparencies.  They have 
several grades; I can give the exact part number if you're 
interested.  I'm using a Lexmark Optra E+ printer with toner refills; 
I haven't found toner to be a significant variable.  I've used the OEM 
toner and any brand of refill and haven't noticed a difference.

Nothing else worked very well.  Some CompUSA inkjet transparencies 
looked like they'd do well (better toner coverage), but I couldn't get 
a good transfer.  May need to work on ironing time.  Also tried laser 
transparencies and transparencies used for color wax printers (Phaser 
type).  Nothing worked as well as the HP inkjet transparencies.

With all inkjet transparencies, I get virtually 100% of the toner 
transferred.  Laser transparencies appear to have a greater affinity 
for toner; but I was doing a "hot" remove back then.  With inkjet, I 
do a "cool" remove.

Since I'm not using the laminator technique, I find that the 
transparencies allow me to apply heat/pressure where needed.  You need 
to cover the transparency with a paper towel to protect the carrier 
from melting.  This will also help for double sided applications 
because you can see through the carrier to line things up.  To date, 
the only double sided boards I've done were for card edge connectors 
and I did the layout so that I only needed the fingers to line up -- 
basically 2 single sided layouts on the same board.

The paper towel will take a pass or two to shed excess fibers; then 
sticking to the transparency will lessen.

I typically have some pin holes, but nothing that's more than cosmetic 
and I've never noticed any etching all the way through the copper.  If 
you remove all of the toner (I used to leave it to prevent oxidation), 
you could scrub the copper to remove any oxidized spots.  Copper fills 
are more problematic, but they can be touched up with an etch resist 
(I use fine point black Sharpies, ultra-fine and industrial chisel 
tips don't work).  But that's purely cosmetic.  If you're worried 
about conductors being compromised by the pitting, you could make them 
wider or tin the traces with solder.  I tried using a solder pot for 
tinning, but temperature appears to be important and I need to perfect 
my technique.  I've only had traces from an inkjet transparency 
transfer that were "bad" enough for me to want to go over it with a 
Sharpie once; I was too lazy to clean the board and try again.  That 
board was 100mmX160mm (posted with my photos).

An upside to my inkjet transparency method is that once ironing is 
done and the board has cooled to the touch, I'm almost ready to etch.  
No soaking/rubbing or dealing with paper fibers.

I use a toothbrush scrub with some liquid soap to remove any traces of 
the coating from the transparencies.  Then I do any touch-up before 
etching.

One last thing.  Since the carrier is transparent, I can see how much 
traces are spreading.  I can also see how small the pad/via holes are 
getting.  I like to have them almost closed to use as a pilot hole for 
drilling.  I choose the smallest hole diameter for all holes.  For 
library components, I put a via on them (there are times when Eagle 
complains).  I usually end up cutting and pasting the metal/vias to a 
different board, replacing library pads with vias, and arraying the 
pattern to fill an 8.5x11 sheet for printing.

I have some pictures posted for an inkjet transfer.

Regards,
Dennis

--- In Homebrew_PCBs@yahoogroups.com, Mr Crazy <crazymr420@...> wrote:
>
> Does any one know if OHP film, Transperancy and Acetate Films are 
the same or all are different?
> 
> Which is the best for Toner Transfer?
> 
> Parag