Homebrew PCBs

--- In Homebrew_PCBs@yahoogroups.com, William Alford <walford@...> wrote:
...
> 
> Don Lancaster, famed electronics writer online at the guru's lair has 
> said that after chemical cleaning, the board should be quickly dipped 
> into ferric chloride and then well rinsed before beginning any kind 
> of PC resist coverage. 

...

> 
> William Alford
> 
> GI Motility Medical Research Page
> http://alford.grimtrojan.com/ 
> 
> [Non-text portions of this message have been removed]
>

Yesterday I was working on some small urgently needed boards using
toner transfer and my usual methods.  Everything went well enough
until i ran out of fresh board material and needed to reuse some that
had been used for an earlier, incorrect pattern.  

Suddenly, though I cleaned with 91% IPA, then Acetone, then Toluene,
used Scotchbrite and Bar Keeper's Friend copper cleanser, one at a
time and then in combinations, I could not get acceptable toner
adhesion.  

In desperation I put the cleaned board into the ferric chloride for
just long enough to see a patina.  It wasn't pretty - the slight
whorls and general unevenness in the copper's color made me uneasy
about trying this.  But after that things went much better, and I
finished the project.

Like traditional photography, the limitations one has on process
control makes producing small quantity PCBs a challenge, and sometimes
something of a mystery.

Dave Witten