Homebrew PCBs

Adam and the group,

If you want to make plated through boards you should consider asking  
a board fabricator to sell you some of their existing chemistry. The 
cost of this stuff is higher than you would think because of the 
minimum quantities that must be purchased when starting new. These 
chemical baths require almost daily testing and replenishment with 
the main culprit being the catalyst and electroless copper baths. 
Some systems don't require an electroless copper bath and use a super 
activated palladium catalyst which is a little easier to maintain.

After taking on something like this you should just go into the 
business and get as much work as you can to make it worth doing. One 
thing to consider is that 15 years ago there were about 3000 shops in 
the USA and earlier today while I was talking with a drilling machine 
supplier he said there were less than 200 shops left in the USA. Many 
of the big guys from earlier years all went broke.

On one hand there is a glut of used equipment available really cheap 
right now which means you can setup a shop without much cash. For 
example, when I closed my PWB plant I sold my best Excellon drilling 
and routing machine for $6500. This machine was in excellent shape 
and cost $146,000 new. One of your biggest expenses will be just 
MOVING all of this equipment and setting it in place. 

On the other hand the business climate in the PWB industry is soft 
with mucho foreign competition so its a tough call on what to do. It 
is a fascinating technical business but there isn't much money in it 
anymore. Printed circuits are a commodity now days with low selling 
prices.

One thing to consider is trying to find some small plating tanks for 
your electrolytic plating and do the through hole sensitizing using 
pyrex trays on hot plates. This will work on a small scale. A small 
spray etcher with sodium persulfate will handle the etching part. If 
you wanted reflowed solder you could modify a donut fryer to get it 
up to 475 degrees F and you would be all set to reflow the tin/lead 
plating.

The rectifier for acid copper plating should be capable of at least 
30 amps per square foot per side. The solder plating requires 
somewhat less current at around 20 amps per square foot. If you use a 
CAM program to setup your films they will tell you the total square 
inches of copper traces and pads for plating. 

When I closed my plant I kept one photoplotter for making precision 
films,a smaller drilling machine, pin router and silk screening 
equipment. Now I just make boards for the instruments and control 
systems that I make. Everything is single sided except for one RF 
board with only four through holes which I bond with eyelets. There 
are times when I miss the plated through capabilities but I manage 
without it and doing fine.

If anyone wants more information on how the plated through process 
works I would be glad to write up something on it. I did it for 
twenty four years and learned it from the ground up.

Tom










--- In Homebrew_PCBs@yahoogroups.com, adam Seychell 
<adam_seychell@y...> wrote:
> Hi all,
> 	I was just wondering how many people here would like to make 
their own 
> plated through hole double sided boards. How far are hobbyists 
willing 
> to go ? The main question is if this extra step is worth the amount 
of 
> chemicals and equipment needed to make plated through. I had the 
desire 
> to make plated boards for a long time but only because I find both 
the 
> chemistry and electronics side interesting. From what I have found 
with 
> experiments, is that the process can be done at home if you are 
prepared 
> to put in the effort. There is a lot setting up with the equipment 
such 
> as plating tanks, etching tanks, making holes conductive, applying 
dry 
> film photoresists and then there is the equipment for analyzing the 
> chemistry, not to mention the learning curve. About the only good 
news 
> is that the chemistry is relatively low cost and the toxicity is 
about 
> the same as conventional copper etching solutions (copper is a 
toxic 
> heavy metal). The ultimate aim would be 4 layer boards, but that 
raises 
> a whole new set of hurdles.
> 
> reagrds,
> 
> Adam