Homebrew PCBs

Jam5411's recent EUREKA moment with using the Simple Green wipes on a
inkjet printed pcb got me to thinking. There has been a lot of
discussion on the best method to clean pcb's. But in fact, we were
really discussing the correct method to "prepare" pcb's. A 'totally
clean' pcb just may not be best.

The Simple Green wipes left a slight film that affected the surface
tension of the ink/copper interface and resulted in better inkjet
printing. My guess is that the "brake fluid" and the TARNEX have the
same mechanism of leaving a slight invisible film on the copper. There
are probably many other compunds that would work.

I looked for some Simple Green wipes locally, but could not find any.
But based on the MSDS sheets, the wipes used some standard cleaning
solvent. These solvents or similar are used in most 'spray cleaners'.
So checking under the sink, I had both Windex window cleaner and an 
Orange Fresh" spray cleaners. (On a side note, the Orange juice
industry found a way to make money off the waste pulp and rinds of the
orange. They steam distill off the "bitterness" of the rind which is
used as an evironmentally friendly solvent.)

One lab test to measure surface tension is to place a drop of liquid
on the surface and measure either the angle of contact or diameter of
the droplet. The test can give quick and dirty comparisons of the
relative surface tensions. I decided to give it a try.

My first step was to thoroughly clean the copper. I used a green
scouring pad with an abrasive sink cleaner (COMET), rinsed it very
well in water, then follwed by a double rinse in 70% isopropyl
(rubbing) alcohol and a final rinse with 91% isopropanol.

I then cleaned one strip with the Orange cleaner and a second area
with Windex and wiped them dry. The third strip was the control.

I then carfully applied very small drops of MIS Yellow ink using a
fine wire. Being carefull to keeep the drop size and application force
constant. 

It was amazing, the strips with the cleaners had drop diameters at
least twice that of the control area. The chemicals left by the
cleaners significantly changed the surface tension. The results with
both cleaners was similar.

This means that we can control the wetting out properties and reduce
the puddling without adding anything to the ink itself.

As I'm writing this, the thought crossed my mind that this may be
applicable to Toner Transfer also. The toner is in a liquid state and
must properly wet out the copper. I'll probably give a try on my next
run of pcbs.

Myc





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