[AR] Re: Electroforming Experiment
- From: Peter Fairbrother <peter@xxxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Sun, 14 Jul 2019 01:25:15 +0100
On 13/07/2019 22:18, Ed LeBouthillier wrote:
On Sat, 2019-07-13 at 20:38 +0100, Peter Fairbrother wrote:
Also: (about 0.04 Amps/sqin)
First impressions: Copper level is ok; not enough acid; current too
low; too many additives.
Thanks. I don't have a pH meter yet.
The copper level is about medium. As you are not using very high
currents or acid concentrations, this is fine.
Do you know of any good general sources on setting up plating
parameters? I found a NASA pub:
Investigation of Electroforming Techniques
http://hdl.handle.net/2060/19760013393
It touches on some of the things you've mentioned.
Hadn't seen that one before, but it seems like a goodie. Ignore the
pyrophosphate bit, pyrophosphate copper is no good at high temperatures,
and concentrate on acid copper with PCR - that's where the good stuff lies.
The long and boring stuff about bath prep, maintenance etc - well you
have to read it, but you don't have to do it all :)
Basically:
4A/dm^2
8 seconds forward, 4 seconds reverse
20C
190 g/l Cu2SO4.5H2O
75 g/l H2SO4
chloride ion 80ppm by weight
xylose 0.3 g/l
as much agitation as is reasonably practical: then some more agitation
continuous filtration with activated carbon and 3 micron filter
occasional peroxide treatment
is pretty much state of the art; and will give at least as good results
as you can get anywhere else.
I use 7A/dm^2 and 1.6/0.4 seconds because it's faster (and because I use
a LOT of agitation) - but 4A/dm^2, 8s forward, 4s reverse gives better -
possibly the best available - results.
A note on agitation: this can consist of aeration, rotation,
ultrasonics, pumped flow in electrolyte, pumped flow in air - where you
pump the electrolye through the anode, then spray it over the cathode
workpiece to drip off - no drops in the spray, so the current flows in
the stream of the spray - anything to refresh the active layer of
electrolyte immediately next to the workpiece as fast as possible.
Are there any
industry standard documents that would be helpful?
Safranek's "Properties of Electrodeposited Metals and Alloys" is the
classic oldie but a goodie.
Modern Electroplating, Edited by Mordechay Schlesinger and Milan
Paunovic, is a bit more up-to-date, but perhaps less detailed.
Chapter 2, ELECTRODEPOSITION OF COPPER by JACK W. DINI AND DEXTER D.
SNYDER is a good but basic intro.
But a lot of stuff is either proprietary, or hidden by proprietary stuff
- eg I was reading a paper about the math of deposition, but then they
start talking about ingredient X, made by their sponsor - and then don't
tell you what X is.
That sort of thing is common.
On power supplies, the attached image is my 10A Mk3. It's my own one,
and a semi-prototype, so not as pretty as it might be. :)
Mk1 was analog, it had a quad 555 timer - 558? - with forward time, off
time, reverse time, off time knobs, and separately variable current for
forward and reverse.
Mk2 was digital, with an Arduino and a full-wave bridge, and you could
tweak anything you liked, even eg adding a sine or triangle wave of any
frequency to the "on" waveform (by reprogramming the Arduino...).
Mk3 is simpler, because I find you don't need most of that.
From top left clockwise in a circle, controls are: auxiliary motor
speed controller speed knob and output socket; temperature controller;
actual current and voltage display; power off/on; main current control
for both forward and reverse current; reverse/periodic-reverse switch;
main output socket; temperature controller socket; 2 more aux motor
outputs and knobs.
The forward and reverse on times are adjusted by presets on a 555 inside
the case; the reversing switch is a car relay, not a FET bridge.
Peter Fairbrother
Attachment:
Mk3.JPG
Description: JPEG image
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