Homebrew PCBs

On Sat, 17 Aug 2013 10:00:08 -0000, you wrote:

>Hello group.
>
>When manufacturers of boards plate through the holes they use some kind of special fluid solution, this attracts copper thus the hole is plated in copper.

Kinda.

This description is an old process, they might do it differently now.

The fluid makes the edges of the hole conductive.  Since all the holes
are drilled first, every top and bottom hole is connected.

The board has a negative resist on it, resist where you do not want
copper.

They then plate the board with one oz copper thickness.  This shorts
(all of) the layers  together.

The resist is still on, so you have a thicker copper layer where there
is to be a trace.

They then plate tin on the board, This plates the traces.  At this
point, the board is solid copper covered with resist where there is to
be no copper, a thicker plated trace that goes through the holes, and
tin plating all over that.

They then strip off the photoresist, leaving tin plated traces and
bare copper.

Etch in Ammonium persulphate or the like, which does not attack tin,
but does attack copper.

unprotected copper is removed, not touching the tin plating.

The plating through hole chemicals (graphite in a solution has been
used, I think), don't support the action that you want (you'd have to
spray this on the board, it would have to be continuous to plate a
copper layer, etc....)

Harvey

>
>So I was wondering if it is possible to use the same solution to print the actual pattern, afterwards transferring copper (sulphate?) to build up the tracks.
>
>Regards
>
>