etching (Coating)

[The Dark force of dance]

Y-ellow Y'all.
        I thought I'd share this with you whilst we're on the subject. This
something that I was about to do but the device disappeared for one reason
or another. Err but I'm getting ahead of myself.

Get an old washing-machine disk drive. You know the sort that use to take 14
inch disk-platters. An old 5 by 5 or something. Hot-wire the drive motor to
a switch so it just runs. Unbolt the spindle head and mount a clamp on there
such that you can clamp a PCB into it in roughly the centre.

Use some liquid etch resist. The kind you get in a bottle such as CCPR12.
Rev up the motor and spin the PCB up. Then, with an eye-dropper or something
similar, Drop a quantity of the etch resist into the centre of the spinning
board and with centrifugal force, it should spread evenly right to the edges
of the board.

Like I said I never got to do this because someone pinched my disk drive.
However this is how they coat silicon wafers. Of course it's easier since
the wafer doesn't vary in size and is round. However if your clamps are set
up right so you can adjust them from both ends, you should be able to centre
the board in the centrifuge.

See this liquid photo resist is dirt cheap by comparison to any other
method. However it's a bugger to get an even coat. Using a centrifuge is
probably the best way in small volumes. And perhaps you could use it in
conjunction with Isac's water idea. Must have a look to see If I can find
another 5 by 5.

Hope this helps.

Be absolutely Icebox.
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