Wednesday, September 28, 2016

Thru-hole copper plating

Spending some time looking for a more effective way to copper plate two sided PCB boards, combining ideas from different sources.
Currently, as far as I can find on shared media, the whole surface of the copper sheet, on both sides, are plated in order to actually achieve the objective of plating the holes.
This seemed to be a waste of time, and overall cost of raw materials. So envisioning here a system that utilize the very known film resist technology to isolate most of the copper, allowing quick and cheap plating of pads and holes.
I'm also trying to replicate some recipes found online for the hole activation solution, which in my opinion is the most critical element of this process. Still collecting chemicals, some not easy to get in US due to DEA restrictions, will post the recipe once tested.

Below is the design for the plating tank, which consist of a acrylic box, with middle flanges to hold the PCB like a sandwich, isolating top and bottom plating solution, allowing flow thru the holes only.
The board is drilled and receive a film resist layer that allow pads and vias to be exposed. This can easily be achieved with common PCB design CAD SW's, like Eagle.
The copper layer in both top and bottom layers of the board are electrically connected to the negative of the plating power source.
Two copper mashes are positioned above and below the PCB and both connected to the positive of the power source, allowing even plating of the pads, vias and holes from both sides.
Another element is the fluid pump that will circulate the plating solution, moving it from top to bottom of the tank. The main objective of this is to force solution into the holes, bottom to top, allowing better plating and push out  and release bubbles that form inside the tiny holes.

Right now this is just a project, will post as it develops. Any thoughts and feedback are welcome.


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