Re: Cathode Films from Sheldahl

[Gerard Visser <gvisser@indiana.edu>]

Hi Simon,
	I think you may be overlooking something... -->

resistivity of gold
  2.2E-8 Ohm*m

surface resistivity @ 900 Angstroms
  2.2E-8 Ohm*m / 9E-8 m = 0.244 Ohm (per square)

length of longest strip
  about 242 squares

characteristic impedance
  who knows - not simulated - but surely on the order of 100 Ohms at the 
most

signal loss (at the most optimistic) 1-exp(-242*0.244/100)=45%

not so good, I think.
and this simple analysis did not mention the noise contribution of this 
resistance. probably nonzero.

I think this all needs to be considered more carefully. A real 
calculation of the cathode line impedance and attenuation and the noise 
contributed by it, should be done.

	- Gerard

p.s. Yes I do agree with the concern about handling (and connecting to) 
any super-thin layers whether copper or gold.


Simon Taylor wrote:
> Hi, Fernando,
> 
> As far as thickness goes, 900 Angstroms of Gold should be okay:
> For each gold layer I get  900 x 10^-10 m x 19.3 g/cm^3 / (6.4 g/cm^2) =
> 2.7 x 10^-5 X0,
> compared to 1.3 x 10^-4 X0 for 2 microns of Copper.  My concern for such
> a thin layer of conductor is handling:  I can well imagine it could be
> quite easy to cause breaks in the strips due to scratches...  Also, we
> would probably have to do some selective plating near where the strips
> need to be connected to the outside world.
> 
> Simon
> 
> 
> Fernando J. Barbosa wrote:
>> Sheldahl has a series of gold deposited materials that can be used for
>> the cathodes. These materials are normally specified as thermal
>> barriers in satellites but can be used for the FDC cathodes. Part #
>> 146437 (see below) is a standard product with 900 angstroms of Au on
>> 25 micrometer Polyimide and can be delivered in 48 inches wide rolls.
>> The left column below is for standard products (available) and they
>> range from 8 to 127 micrometer Polyimide.
>