Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

Hi Markus,

I can give you one experience from my past experience in the PCB
industry many years ago.

One problem we encountered, very rarely, but gave a lot of "pain in
the head". Sometimes the palladium solution would seep into the
circuit board itself and created conductive tracks inside the PCB.

We found that it was caused by mainly two things.
1) drilling process, the drill bits would sometimes make a ragged
hole. That hole was the start of a "tunnel" that sometimes reached
another hole. This would obviously cause an invisible short in the
circuit.
2) bad raw pcb material. The fibreglass mesh that the board was made
of sometimes wasn't compressed enough, aggrevating the first problem.

I have troubleshot many such circuits, and I have to tell you that it
can be a real nightmare. A circuit that has an invisible short...

Other than that, I can say that you will have a lot of fun making
boards. The owner of the company that I worked for started in a
similar way that you are doing. He operated a successful business for
over 20 years in the prototype circuit manufacturing.
He hired a helper to help him. Then more and more, etc.
He also welded the plastics. He used gray PVC sheets for all his
machines.

For the next step, you should make a Tin-Lead electro plater. That is
used to place the tracks on the PCB.

After the holes are copper plated, the board is coated with photo-
resist (Riston) and then exposed (both sides) through the negative.
The resist is "negative", that means no resist where tracks are to be.
The tin-lead is then plated onto the exposed tracks (no resist).
After removing the photoresist (we used Riston) the remaining tin-
lead tracks were used as etch resist.
After etching, the PCB went into a reflow bath. The reflow bath was
simply peanut oil heated to the necessary temperature to melt
or "reflow" the tin-lead. That gives a nice shiny surface finish and
smooths out any electroplating imperfections.


Good luck,
John M...
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