Silver vs. gold switch contacts

CC · Apr 5, 2006

Hi:

I am planning to make a switched gain transimpedance amp, switched gain
voltage amp, as well as a switched bandwidth filter based on op-amps and
rotary switches. I'd like to use ITT MA00L1NCQD or Grayhill
56DP36-01-1-AJN from DigiKey.

Both of these have silver contacts for the rotor. The ITT has silver
stationary contacts as well. While at least the Grayhill has gold
plated stationary contacts. In fact, even when ordering the "G" contact
type from ITT, the rotor I think is still silver.

Alternatively, there is a bit more expensive ITT 50DP36-01-1-AJN which
has all gold contacts.

Is silver unacceptable for circuits in which practically no current
flows, such as an op-amp's feedback loop?

Thanks for input.

Good day!

Al · Apr 5, 2006

CC said:
Hi:

I am planning to make a switched gain transimpedance amp, switched gain
voltage amp, as well as a switched bandwidth filter based on op-amps and
rotary switches. I'd like to use ITT MA00L1NCQD or Grayhill
56DP36-01-1-AJN from DigiKey.

Both of these have silver contacts for the rotor. The ITT has silver
stationary contacts as well. While at least the Grayhill has gold
plated stationary contacts. In fact, even when ordering the "G" contact
type from ITT, the rotor I think is still silver.

Alternatively, there is a bit more expensive ITT 50DP36-01-1-AJN which
has all gold contacts.

Is silver unacceptable for circuits in which practically no current
flows, such as an op-amp's feedback loop?

Thanks for input.

Good day!

The problem occurs when the contacts are open. If there is a DC bias
voltage between them and the humidity is high, the silver will migrate
and eventually cause a short. Usually this happens between adjacent
contacts as the silver forms dendrites. Gold is unlikely to do this. Tin
will also migrate; you can actually see the whiskers form. I have seen
the tin bridge air gaps. The higher the humidity and the voltage, the
faster the effect takes place.

Al

martin griffith · Apr 5, 2006

Hi:

I am planning to make a switched gain transimpedance amp, switched gain
voltage amp, as well as a switched bandwidth filter based on op-amps and
rotary switches. I'd like to use ITT MA00L1NCQD or Grayhill
56DP36-01-1-AJN from DigiKey.

Both of these have silver contacts for the rotor. The ITT has silver
stationary contacts as well. While at least the Grayhill has gold
plated stationary contacts. In fact, even when ordering the "G" contact
type from ITT, the rotor I think is still silver.

Alternatively, there is a bit more expensive ITT 50DP36-01-1-AJN which
has all gold contacts.

Is silver unacceptable for circuits in which practically no current
flows, such as an op-amp's feedback loop?

Thanks for input.

Good day!

There is a app note from Tyco/Pandbrelays.com called "relay contact
life" that goes through many contact formulation. Dont have the URL,
the app note *may* be called IH/12-00

worth a read if you can find it

martin

Chris Carlen · Apr 5, 2006

martin said:
There is a app note from Tyco/Pandbrelays.com called "relay contact
life" that goes through many contact formulation. Dont have the URL,
the app note *may* be called IH/12-00

worth a read if you can find it

Found it easily thanks to Google...

http://relays.tycoelectronics.com/app_pdfs/13c3236.pdf

Thanks for the info.

--
Good day!

________________________________________
Christopher R. Carlen
Principal Laser&Electronics Technologist
Sandia National Laboratories CA USA
[email protected]
NOTE, delete texts: "RemoveThis" and
"BOGUS" from email address to reply.

AZ Nomad · Apr 5, 2006

Hi:

I am planning to make a switched gain transimpedance amp, switched gain
voltage amp, as well as a switched bandwidth filter based on op-amps and
rotary switches. I'd like to use ITT MA00L1NCQD or Grayhill
56DP36-01-1-AJN from DigiKey.

Both of these have silver contacts for the rotor. The ITT has silver
stationary contacts as well. While at least the Grayhill has gold

What kind of moron would use silver? Do they expect you to get out
the silver polish every two weeks to remove the tarnish?

Are you confusing some other silvery metal with silver?

Chris Carlen · Apr 5, 2006

AZ said:
What kind of moron would use silver? Do they expect you to get out
the silver polish every two weeks to remove the tarnish?

Are you confusing some other silvery metal with silver?

Silver, element Ag, the one that tarnishes is used all over the place in
electronics. And I often wonder why since it tarnishes like crazy. Of
course, it also has many desirable features.

What really bugs me is BNC and other connectors and switches with solder
lugs that after sitting in a drawer for a while are impossible to
solder. Have to wire brush them with a dremel tool. Very time consuming.

But silver is indispensible it seems in contacts rated for carrying
significant amounts of current. Low level stuff though, clearly needs
all gold.

--
Good day!

________________________________________
Christopher R. Carlen
Principal Laser&Electronics Technologist
Sandia National Laboratories CA USA
[email protected]
NOTE, delete texts: "RemoveThis" and
"BOGUS" from email address to reply.

Phil Hobbs · Apr 5, 2006

Chris said:
Silver, element Ag, the one that tarnishes is used all over the place in
electronics. And I often wonder why since it tarnishes like crazy. Of
course, it also has many desirable features.

What really bugs me is BNC and other connectors and switches with solder
lugs that after sitting in a drawer for a while are impossible to
solder. Have to wire brush them with a dremel tool. Very time consuming.

But silver is indispensible it seems in contacts rated for carrying
significant amounts of current. Low level stuff though, clearly needs
all gold.

One good reason is that silver oxide is a metal. Tarnish is ugly but
hardly affects the contact resistance.

Cheers,

Phil Hobbs

Roy L. Fuchs · Apr 5, 2006

What kind of moron would use silver? Do they expect you to get out
the silver polish every two weeks to remove the tarnish?

Are you confusing some other silvery metal with silver?

Most switch contacts are gold or platinum plated.

Just so you know Silver Oxide in pure form is a better conductor
than silver itself is. There is none better, in fact.

Elementally speaking, the best conductor is Silver. With respect to
compounds, however, Silver Oxide is the best conductor known to man,
short of superconducting media.

Ancient_Hacker · Apr 5, 2006

Elementally speaking, the best conductor is Silver. With respect to
compounds, however, Silver Oxide is the best conductor known to man,
short of superconducting media.

Very interesting! Howcome this isnt more widely known?

But isnt the black stuff on silver more likely to be silver sulfide?

Silver oxide is more a brownish color I think,, the crud on silver is
usually brown to black.

Chris Carlen · Apr 5, 2006

Roy said:
Most switch contacts are gold or platinum plated.

Just so you know Silver Oxide in pure form is a better conductor
than silver itself is. There is none better, in fact.

Elementally speaking, the best conductor is Silver. With respect to
compounds, however, Silver Oxide is the best conductor known to man,
short of superconducting media.

But isn't much of silver tarnish silver sulfide, rather than oxide?
Silver in a non-sulfurous environment remains free of tarnish for quite
a long time. The tarnish I see on most stuff is black, which I think is
mostly silver sulfide. It is not at all conducive to soldering, but I
suppose usually doesn't cause too much trouble with contact resistance,
as it probably gets scraped away sufficiently during wiping action.

Seems to be reiterated here:

http://www.infoplease.com/ce6/sci/A0845253.html

Haven't heard of platinum plated contacts either. Can you link to a
vendor that has any such beasts? This document speaks of using
palladium in relay contacts:

http://relays.tycoelectronics.com/app_pdfs/13c3236.pdf

--
Good day!

________________________________________
Christopher R. Carlen
Principal Laser&Electronics Technologist
Sandia National Laboratories CA USA
[email protected]
NOTE, delete texts: "RemoveThis" and
"BOGUS" from email address to reply.

Phil Hobbs · Apr 5, 2006

Ancient_Hacker said:
Very interesting! Howcome this isnt more widely known?

But isnt the black stuff on silver more likely to be silver sulfide?

Silver oxide is more a brownish color I think,, the crud on silver is
usually brown to black.

Silver sulphide is a good conductor too, although not as good as silver
oxide.

Cheers,

Phil Hobbs

mike Monett · Apr 6, 2006

[...]

Silver sulphide is a good conductor too, although not as good as silver
oxide.

Cheers,

Phil Hobbs

Phil, Any info on the conductivity of silver hydroxide, AgOH? In fact, if
you have any info on AgOH, such as decomposition temperature, I'd sure
appreciate it!

Thanks,

Mike Monett

Phil Allison · Apr 6, 2006

"Phil Hobbs"

One good reason is that silver oxide is a metal.

** Huh ???

Tarnish is ugly but hardly affects the contact resistance.

** What nonsense.

......... Phil

Tim Williams · Apr 6, 2006

Phil Hobbs said:
One good reason is that silver oxide is a metal. Tarnish is ugly but
hardly affects the contact resistance.

Er, silver oxide is a compound. If it were a metal, it wouldn't be a
compound, period! LOL

(Sure, lots of intermetallic alloys look like compounds, though.. MgAl vs.
PbS vs. pure Si, etc...)

Tim

Tim Williams · Apr 6, 2006

Roy L. Fuchs said:
Just so you know Silver Oxide in pure form is a better conductor
than silver itself is. There is none better, in fact.

Ha. Ha ha.

So, smarty pants, got a cite to share with us?

Tim

Phil Allison · Apr 6, 2006

"Phil Hobbs"

Silver sulphide is a good conductor too, although not as good as silver
oxide.

** Silver sulphide is an INSULATOR !!

Silver plated switch contacts INSULATE the circuit if they become tarnished
with silver sulphide.

Low current silver plated switches are normally designed to be "self
cleaning" - ie the contact surfaces wipe each other during switching.

Silver oxide does not exist on metallic silver under normal conditions.

........ Phil

AZ Nomad · Apr 6, 2006

Ha. Ha ha.

So, smarty pants, got a cite to share with us?

I'd be interested in how it compares to other metalic oxides. AFAIK, they're
all lousy conductors.

Michael A. Terrell · Apr 6, 2006

AZ said:
I'd be interested in how it compares to other metalic oxides. AFAIK, they're
all lousy conductors.

Yeah, Silicon oxide is a horrible conductor, and its as common as
sand. ;-)

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

Sjouke Burry · Apr 6, 2006

Phil said:
"Phil Hobbs"

** Silver sulphide is an INSULATOR !!

Silver plated switch contacts INSULATE the circuit if they become tarnished
with silver sulphide.

Bull.-)-)-) I have made lots of skin electrodes
with silversulfide layer on silver ,and they
conducted fine,one funny property was that the
layer was photo sensitive,you had to grow the
layer in total darkness.Conduction was oke in
both cases but the layer grown exposed to light
tended to drop off the silver.

Phil Allison · Apr 6, 2006

"Sjouke Burry"

Bull.-)-)-)

** Know anything AT ALL about elctrical contact issues ??

This will get you kick started.

http://relays.tycoelectronics.com/app_pdfs/13c3236.pdf

I have made lots of skin electrodes
with silversulfide layer on silver ,and they
conducted fine,

** Yawn.

Wrong topic .....

.......... Phil

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