Homebrew PCBs

There's another problem with toner transfer or any other system which has an
intermediate printing step, and that is heat expansion.

On ordinary components it is insignificant, an 8-pin DIP will be good even
with moderate distortion, but on 'some' long components expansion becomes an
issue.  Yes, I have a ratio adjustment feature on QCAD, but the toner
transfer paper will not expand at identical rates.  Humidity in the air (and
paper) will give varying results, I'd have to test 'each' piece of paper
'cause my house is not a controlled environment.

I have one PCB that was affected by this, it had a 30-pin connector and it
came out 'short'.  The problem is that I only noticed that once etched.  I
had done a test print on ordinary paper, but that does not expand the same
way as Pulsar paper, everything was ok.

Printing directly onto the copper will reduce the risk of errors creeping in
the results.  Ideally, we'd have that direct etch system, but that will have
to wait.

Robert
:)


-----Message d'origine-----
De : Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com] De
la part de lcdpublishing
Envoyé : avril 16 2006 13:23
À : Homebrew_PCBs@yahoogroups.com
Objet : [Homebrew_PCBs] Re: inkjet second side alignment (was: homebrew CNC)


In metal working and in woodworking that concept is used quit 
frequently, so for me to get it was easy.  It is a tough one to 
grasp because it is hard to visualize that the printing will be 
square to the one edge - regardless of what the other three edges 
look like.  In reality, this could be accurate to within .003" 
depending on a couple of things...

...