Homebrew PCBs

Marvin,

If you don't want to go through all the technical know-how 
and details of chemistry of plating then I would recommend 
you buy the plating solutions and necessary parts from 
someone who specializes in this. Markus has shown the group 
he has had good success with Bungards as a supplier. You can 
probably save money buying everything individually, such as 
anodes from an anode supplier, or sulfuric and copper 
sulfate from a chemical supplier, brighteners from a plating 
supplier. There should be electroplating suppliers in any 
industrialized city that has electroplating shops. It took 
me quite a few phone calls before I found what I needed. Its 
surprising how helpful some salesmen can be to the poor 
hobbyist trying to setup a plating apparatus. The chemicals 
are non-toxic, although corrosive and can burn skin & eyes.

The problem may be buying small quantities. If the person at 
the electroplating supplier is not too busy he/she should 
happily sell you small quantity. I was lucky enough to get 
free 250 ml bottle of Macdermid brightener for acid copper 
sulfate plating, simply because it wasn't worth their effort 
selling so small amount. That gave me enough brightener to 
make 90 liters of plating solution. Don't bother trying to 
buy supplies from PCB fabricators or plating shops. I went 
to about 6 different places and not ONE of them was willing 
to sell me anything.

Your anodes must be phosphorized copper or they won't form 
the black protective film during dissolution. Anodes are 
sold at electroplating suppliers as nuggets, bars, ect. I 
bought 1 kg of nuggets because the bars were too big and 
expensive. The nuggets sit in a sack made from outdoor 
plastic shade cloth (polyethylene). A connection is made by 
2mm^2 PVC coated solid wire to one of the nuggets, which 
contacts the remaining nuggets. I drilled a hole in the 
nugget to neatly fit the solid wire and used a nail punch to 
crimp the outside of the nugget. Some PVC solvent cement 
sealed the wire connection at the nugget. If you can get 
small anode bars then they will be easier to use than nuggets.

My tank is 250 mm x 340 mm base and 320 mm high. Liquid 
depth is 250 mm. Maxium PCB capcity is 300x200mm. Spacing 
between the middle of the anode and PCB surface is about 90 
mm. There are two anodes in total giving one on each side of 
the PCB. The anodes sacks are about 60 mm diameter at the 
widest part. Each anode weights about 500g. There is 
polypropylene anode bags as recommended in the Macdermid 
brightener datasheet. I bought one large anode bag form the 
supplier and cut it to size, then sowed together with 100% 
polyester thread. I usually plate between 2 and 3 A /dm^2, 
but go down to 1.5A/dm^2 in cold temperatures (<15\ufffdC) in 
order to maintain a bright plating finish. Solution 
agitation by air bubbles using homemade air diffuser (two 
lengths of PVC pipe 1 mm holes each spaced 25 mm) and a good 
aquarium air pump. There are lead weights at the bottom 
which stop the diffusor from floating. Tank holds 22 liters 
of plating solution and constructed from gray 4.5mm ridged 
PVC sheet. All plastic joints are hand welded.

Adam.


mpdickens wrote:
> Hello Markus!
> 
> Your station is most excellent! Questions:
> 
> 1.) What/who's chemistry are you using?
> 2.) How many volts/amps do you? Are you 
>     using a formula to calculate
>     voltage/amperage verses board size?
> 3.) What is the composition of your anodes
>     and what is thier weight/size?
> 
> 
> Before I saw what you had done, I had already begun
> construction of a similar thru-hole plating system.
> Like you, I came to the conclusion that what I needed
> was a station that was built on time tested
> technology. In other words, I wanted to build a
> smaller version of
> what large companies use to thru-hole plate (In fact,
> all of the tools/fixtures/equipment I have made are
> based on proven industry technology).
> 
> Currently, I have the tank, card holders and
> circulation system completed. I still have
> build/engineer the rectifier (power supply), purchase
> anodes and descide on a chemistry. My plan is to
> complete this station, work the kinks/problems out and
> then build a tinning station. 
> 
> Your station is of professional quality. Further,
> I am impressed (Not that it really matters...).
> FWIW, you may want to cross post/link your station
> to:
> 
> http://groups.yahoo.com/group/Electroplating
> 
> 
> Best regards
> 
> 
> Marvin Dickens
>