Homebrew PCBs

--- In Homebrew_PCBs@yahoogroups.com, "Stefan Trethan" 
<stefan_trethan@...> wrote:
> I don't think flux will ever evaporate, no matter in what it is 
dissolved.

Well, I'm not a chemist (didn't pay much attention to chemistry - I 
was an EE major).  But I can tell you what I'm seeing.  If I clean 
flux from an area with 70% IPA and compare it to an area cleaned 
with 98% IPA, the 98% IPA area is cleaner; has less residue.  This 
is without allowing it to run off the edge of the board or blowing 
off the residue with compressed air.  I'm pretty sure some amount of 
flux will be carried off when a volatile solvent evaporates.

Did you ever think about what's going on when you smell some dog 
crap?  You're actually breathing molecules of dog crap...

> Maybe the water is doing something bad, i sure don't understand 
it. Flux  
> will not solve in water, maybe that's causing the dusturbance.

It's the water that's cauing the problem.  I talked to several 
Pharmacists when I was searching for a source of anhydrous IPA.  
They all said that rubbing alcohol was 70% IPA and 30% water.

> What does the good IPA cost in comparision?

98% IPA is costing me $4/pint vs. $1 for drug store variety rubbing 
alcohol.
 
> In general i noticed IPA seems to leave more residue than 
denatured  
> alcohol.

The more volatile the solvent, the less residue it will leave.  I 
attribute that to how quickly it evaporates.  But I'm not a chemist.
 
> I do know what you mean by the snagging wires problem, that's why 
i rarely  
> clean the flux off.

I'm somewhat of a Perfectionist.  I started working as a technician 
before I became an engineer.  I prided myself on quality of 
workmanship.  When I was an R&D Tech at HP Labs, I used to gold 
plate my prototypes and black annodize my heatsinks.  I got a lot of 
compliments on my work.  Back then, I used an endmill to layout my 
boards (a manual CNC if you will).  Even though I could have sent 
them out to have boards made.  Since I never did more than one of 
each design, I did it manually.  It was less work in the end.  I did 
more than a few calculations to determine the proper width for 50 
ohm transmission lines.

Once flux has done it's job of preparing materials for good solder 
joints, it needs to be removed or deactivated so it doesn't cause 
problems.  I was always taught to remove the flux.  Every single 
person who worked on the line where I built computers removed flux.  
But, I've seen commercial equipment that was hand soldered and no 
attempt was made to remove the flux.  Whenever I open up a piece of 
equipment and see that, I remove it; at least from the area where I 
make repairs.  Even if it didn't have the potential to cause 
problems, it still looks better without it.

If I were buying two similar products and one looked like there was 
more quality in workmanship, I'd probably buy the one that had 
better workmanship; even if it cost more.  Maybe that's just me.

Regards,
Dennis