Homebrew PCBs

Hi Bill,

--- In Homebrew_PCBs@yahoogroups.com, William Blair <wbblair3@...> 
wrote:
> You're using inkjet transparencies in a laser printer, correct?  
Did you determine that laser
> transparencies wouldn't work as well?  If they don't work as well, 
is this because inkjet
> transparancies have some kind of coating or finish that helps in 
the transfer of toner to the PCB?

Yes, I'm using inkjet transparencies in a laser printer.  I tried 
several kinds of laser transparencies and, as you mentioned, it's 
the coating on the inkjet transparencies that hold the ink that 
makes it release the toner.  I also tried transparencies for wax 
(Tek Phaser), they were slightly better than laser transparencies; 
but nothing had worked better for me than injket transparencies.  No 
scrubbing, no guessing if toner is melted enough, no blind alignment.

When I used laser transparencies, I found that removing it when the 
toner was hot/melted worked best.  If I let it cool, the 
transparency had a greater affinity for the toner.

With the inkjet transparencies, I let the toner melt and remove the 
transparency after things have cooled; but are still warm.  There's 
some residue from the transparency that I remove with soap, water, 
and a tooth brush.  You can leave it on, but etch time seems longer 
and the residue ends up in the etching solution.

> What brand of transparencies are you using?  Do the inkjet 
transparencies show any sign of melting
> or shrinking under the iron?

I'm using HP inkjet transparencies.  I bought a bulk pack and 
there's no part number.  I put a paper towel (doubled over) between 
the iron and transparency.  If the iron touches the transparency, it 
will melt, but no problems with shrinkage.  A little curling around 
the edges from downward pressure, but no distortion over the board.

The paper towel might stick to the transparency.  I lift the paper 
towel after 10-20 seconds while holding the transparency down so it 
doesn't shift.  After a few lifts, the transparency gets it's fill 
of paper fibers and things stop sticking.

I put the board on a block of wood covered by a doubled paper towel.

> What do you use to remove the toner from only the solder areas?

I use acetone on a cotton swab.  You'll need to experiment with how 
much to apply.  Too little and the toner smears and makes a mess.  
Too much and the toner ends up getting embedded in the board.  Small 
toner smudges can be removed with anhydrous isopropyl alcohol and 
some rubbing with a cotton swab.

> I assume you mean laser copies using _paper_ rather than 
transparencies?

I tried paper, laser transparencies, and injket transparencies.

Regards,
Dennis