Joachim,

The consumption of Au per sample is not necessarily related to the cost of
plating Au. For example, 0.3 grams of Au can be deposited from a 50 liter
bath 30 days
after purchase of the bath and 30 unsuccessful efforts. In that instance you
may include the cost related to:
a. Bath acquisition
b. Bath type (cyanide, non-cyanide), replenisher cost,
c. Bath maintenance
d. Au appreciation or depreciation on the market
e. Test equipment
f.  Test design, sample holder, contact (exposed/isolated) etc.
g. Sample preparation
etc.

In that case the cost of the 0.3 grams (today at $4.28 + in replenisher) is
rather miniscule
compared to the overall expense of running the process. For most practical
instances the actual cost of consumed Au becomes a significant factor
through the replenisher cost and only upon reaching a certain production
level. The calculation depends, as you can see, on many factors including
the ones above.

Regarding the Au consumption rate the non-cyanide Au tends to be deposited
with the rate slightly above 100% by the nature of the solution especially
with inadequate maintenance. The solution suppliers will provide the
appropriate maintenance procedure. The rest of the usage per sample is very
much up to the equipment and test design. If you are interested to minimize
your losses and speed up your projects in a controlled and predictable
processing, we do provide benchtop electroplaters for MEMS and other
microfabrication, www.fibrotools.com - you can contact me directly at
[email protected].

Igor Kadija
ECSI
201-670-8397

----- Original Message -----
From: "Joachim Oberhammer" 

> does anybody know how much gold is actually consumed from the electrolyte
> when electroplating? I calculated that a plating step of 5 um thickness of
> gold on 40% of the area of a 100 mm wafer deposits a volume of about 16
> mm^3, which corresponds to a weight of 0.3 g (assuming a density of 19.3
> g/cm^3, which surely is a too high figure). But how large is the
> "practical" consumption of gold in the electrolyte including deposition on
> connectors and other "losses"? Is it about 100%, 150%, 500% of the
> actually plated volume/weight? Or can anybody give me a cost figure (pure
> electrolyte material costs) of a certain plated volume? (there might be
> differences in the electrolyte; just tell me whatever figures you have in
> mind). How are you doing such calculations?