Silver vs. gold switch contacts

Discussion in 'Electronic Design' started by CC, Apr 5, 2006.

  1. CC

    CC Guest

    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!




    --
    _____________________
    Christopher R. Carlen

    SuSE 9.1 Linux 2.6.5
    CC, Apr 5, 2006
    #1
  2. CC

    Al Guest

    In article <>,
    CC <> wrote:

    > 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
    Al, Apr 5, 2006
    #2
  3. On Tue, 04 Apr 2006 20:51:17 -0700, in sci.electronics.design CC
    <> wrote:

    >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
    martin griffith, Apr 5, 2006
    #3
  4. CC

    Chris Carlen Guest

    martin griffith wrote:
    > 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

    NOTE, delete texts: "RemoveThis" and
    "BOGUS" from email address to reply.
    Chris Carlen, Apr 5, 2006
    #4
  5. CC

    AZ Nomad Guest

    On Tue, 04 Apr 2006 20:51:17 -0700, CC <> wrote:


    >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?
    AZ Nomad, Apr 5, 2006
    #5
  6. CC

    Chris Carlen Guest

    AZ Nomad wrote:
    > On Tue, 04 Apr 2006 20:51:17 -0700, CC <> wrote:
    >
    >
    >>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?



    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

    NOTE, delete texts: "RemoveThis" and
    "BOGUS" from email address to reply.
    Chris Carlen, Apr 5, 2006
    #6
  7. CC

    Phil Hobbs Guest

    Chris Carlen wrote:

    > 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
    Phil Hobbs, Apr 5, 2006
    #7
  8. CC

    Roy L. Fuchs Guest

    On Wed, 05 Apr 2006 17:59:03 GMT, AZ Nomad <>
    Gave us:

    >On Tue, 04 Apr 2006 20:51:17 -0700, CC <> wrote:
    >
    >
    >>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?


    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.
    Roy L. Fuchs, Apr 5, 2006
    #8

  9. > 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.
    Ancient_Hacker, Apr 5, 2006
    #9
  10. CC

    Chris Carlen Guest

    Roy L. Fuchs wrote:
    > On Wed, 05 Apr 2006 17:59:03 GMT, AZ Nomad <>
    > Gave us:
    >
    >>On Tue, 04 Apr 2006 20:51:17 -0700, CC <> wrote:
    >>
    >>
    >>>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?

    >
    > 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

    NOTE, delete texts: "RemoveThis" and
    "BOGUS" from email address to reply.
    Chris Carlen, Apr 5, 2006
    #10
  11. CC

    Phil Hobbs Guest

    Ancient_Hacker wrote:
    >> 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.
    >


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

    Cheers,

    Phil Hobbs
    Phil Hobbs, Apr 5, 2006
    #11
  12. CC

    mike Monett Guest

    Phil Hobbs <> wrote:

    [...]

    >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
    mike Monett, Apr 6, 2006
    #12
  13. CC

    Phil Allison Guest

    "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
    Phil Allison, Apr 6, 2006
    #13
  14. CC

    Tim Williams Guest

    "Phil Hobbs" <> wrote in message
    news:...
    > 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


    --
    Deep Fryer: a very philosophical monk.
    Website: http://webpages.charter.net/dawill/tmoranwms
    Tim Williams, Apr 6, 2006
    #14
  15. CC

    Tim Williams Guest

    "Roy L. Fuchs" <> wrote in message
    news:...
    > 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


    --
    Deep Fryer: a very philosophical monk.
    Website: http://webpages.charter.net/dawill/tmoranwms
    Tim Williams, Apr 6, 2006
    #15
  16. CC

    Phil Allison Guest

    "Phil Hobbs"
    >>
    >> 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.
    >



    ** 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
    Phil Allison, Apr 6, 2006
    #16
  17. CC

    AZ Nomad Guest

    On Wed, 5 Apr 2006 21:23:18 -0500, Tim Williams <> wrote:


    >"Roy L. Fuchs" <> wrote in message
    >news:...
    >> 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?


    I'd be interested in how it compares to other metalic oxides. AFAIK, they're
    all lousy conductors.
    AZ Nomad, Apr 6, 2006
    #17
  18. AZ Nomad wrote:
    >
    > 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
    Michael A. Terrell, Apr 6, 2006
    #18
  19. CC

    Sjouke Burry Guest

    Phil Allison wrote:
    > "Phil Hobbs"
    >
    >>>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.
    >>

    >
    >
    >
    > ** 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.
    Sjouke Burry, Apr 6, 2006
    #19
  20. CC

    Phil Allison Guest

    "Sjouke Burry"
    > Phil Allison wrote:
    >> "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.

    >
    > 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
    Phil Allison, Apr 6, 2006
    #20

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