--- In
Homebrew_PCBs@yahoogroups.com, Markus Zingg <m.zingg@n...>
wrote:
> Hi folks
>
> I'm still testing with water - the voltage regulator still get's too
> hot with low PCB motion speeds. Anyways, I created a little MPEG
movie
> of the station in action for those interested. You find it on the
> bottom of the entry page.
>
> http://www.myhome.ch/mzingg/pcbstuff/tps/
>
> It's farily late now here again. I was busy all day with cleaning up
> my office to make room for the station et all. Then we also had
> guests. I studied the docs of the chemicals I got and - some one
asked
> this - found info about the material the bag's around the anodes
> consist of. They are made of a polyprophylene tissue.
Markus,
That's an impressive tank system you made. I'm also interested in the
chemistry you will be using. Please provide more information when you
have time.
Many years ago I made a tank system for through hole plating in a
commercial shop. This system had six tanks that were 25 gallons each.
Maybe this information will help those considering this method of
processing.
Here is the process and details on that tank system:
Tank #1 Cleaner-conditioner, caustic soda based chemistry with
surfactants. Stainless steel tank. 160 degree F operating
temperature. 5 minute process time.
Rinse cycle
Tank #2 Micro-etch, surfuric peroxide based. PVC tank operating at
room temperature. 1 to 2 minutes.
Rinse cycle
Tank #3 Pre-dip, proprietary chemistry. PVC tank operating at room
temperature. 30 seconds to 1 minute dip. NO RINSE AFTER THIS STEP!!
Tank #4 Catalyst, proprietary activated palladium chemistry. PVC
tank operating at 105 degrees F. 20 minute process time.
Rinse cycle
Tank #5 Accelerator, highly saturated solution of soda ash with
about .5 gallons of copper sulfate solution added. It takes about 50
to 60 pounds of soda ash to make up this 25 gallon bath. Stainless
steel tank operating at 140 degees F. 10 minute process time.
Rinse cycle
Tank #6 Acid dip, 10% sulfuric acid solution. PVC tank operating at
room temperature. 5 minute process time.
Rinse and dry.
The printed circuit panels are now conductive through the holes and
across all exposed edges. An ohm meter connected across both copper
planes will show 10 or less ohms depending on the number of holes.
The panels are now ready for electrolytic plating.
This system used the newer activated palladium chemistry with no need
for electroless copper. Electroless copper is very difficult to run
and needs constant attention. The palladium chemistry is a better
choice for systems that are not run on a daily basis. Electroless
copper is one of the major sources of pollution in a circuit board
plant. You're better off if you never get near it.
Some thoughts about rinsing, in our first system (using electroless
copper)we had a 25 gallon flowing tank for each rinse cycle. Our
small shop used over 7000 gallons of water per day with this rinse
setup. This entire flow had to be waste treated which was a GIGANTIC
headache.
When I built the palladium based system we used a spray wand to rinse
for about one minute into a trough that collected the spray water.
Then the panels were dipped into a 25 gallon rinse tank that flowed
about 2 gallons per hour after which the panels went on to the next
process tank. The idea was to use a small amount of water as a spray
to do 99% of the rinsing and then a quick dip into a slow flowing
rinse tank caught anything else. Very efficient rinsing with very
little water.
All of this rinse water was collected into a common holding tank that
was fed into an evaporator system that boiled off the water at a rate
of about 30 gallons per hour. We ran the evaporator tank several
hours per day and had a ZERO DISCHARGE system with no connection to
the sewer drain. Our only discharge was clean water vapor and we were
able to reduce our water consumption to about 75 gallons per day. The
savings were tremendous and it satisfied the environmental
authorities as well.
Tom