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March 2004

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Subject:
From:
"Chafin, Ken G." <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Fri, 26 Mar 2004 17:13:11 -0500
Content-Type:
text/plain
Parts/Attachments:
text/plain (219 lines)
Someone asked about the material composition:

The pins are tin plated and the socket contacts are gold plated.

There is no evidence of corrosion or galvanic action here.

A laboratory used a SEM to determine the presence of carbon and FTIR to rule
out the presence of any significant quantities of carbon containing
compounds--none was detected.

Another common sense point: electrical arcing between two metal conductors
with the production of a "carbon appearing" deposit at the point where the
arcing occurs is a phenomenon with which most people are familiar.

I would like to understand the process better--including the source of the
carbon.

Searching through physics, chemistry, electronics, failure analysis and
other literature has failed to give me a clue.

If someone has a clue as to where I can find some relevant literature on
this subject I am very interested in hearing from you.

Thanks again.

> -----Original Message-----
> From: TechNet [SMTP:[log in to unmask]] On Behalf Of Dehoyos, Ramon
> Sent: Friday, March 26, 2004 7:59 AM
> To:   [log in to unmask]
> Subject:      Re: [TN] Carbon Buildup On Tin Plated Contacts
>
>         That is very true most of the sockets are reliable. If there is
> any defect such as the fingers of the sockets not putting enough pressure
> on the inserted pin or  the fingers not properly secured ( loose,
> fingers of the sockets are inserted into the socket housing ) or fingers
> fall down and collapsed when a pin is inserted, then there will be arcing
> and carbon build up.
>         Regards,
>         Ramon
>
> > -----Original Message-----
> > From: Crepeau, Phil (Space Technology)
> > Sent: Thursday, March 25, 2004 8:16 PM
> > To:   [log in to unmask]
> > Subject:      Re: [TN] Carbon Buildup On Tin Plated Contacts
> >
> > hi,
> >
> > i know what you all are talking about.  nevertheless i just want to say
> that many mil spec digital, power, and rf mil spec connectors have gold
> pins and sockets and they are extremely reliable.
> >
> > phil
> >
> > -----Original Message-----
> > From: David Douthit [mailto:[log in to unmask]]
> > Sent: Thursday, March 25, 2004 4:35 PM
> > To: [log in to unmask]
> > Subject: Re: [TN] Carbon Buildup On Tin Plated Contacts
> >
> >
> > Bogert,
> >
> > Based on this, we are prohibiting use of sockets for new design
> equipment.  Most military equipment prohibits use of sockets (ref
> historical MIL-STD-2000).  In my opinion, no equipment that is intended
> for long term reliability should ever use sockets.
> >
> > I agree. Even gold to gold contacts can become intermittent due to
> deposition of
> > particles and reactive gases combined with micro vibration and or
> thermal excursions.
> >
> > David A. Douthit
> > Manager
> > LoCan LLC
> >
> >
> >
> > - Bogert wrote:
> >
> > >What is the material finish of the socket contacts?  Is it the same as
> the part pins?  If not, you could have corrosion issue due to different
> finishes.  For example tin plated pins inserted into socket with gold
> plated contacts could be problem.  Another problem could be spread socket
> contacts that cause poor electrical connections resulting in arcing and
> subsequent carbon deposits.  Unfortunately we have used numerous sockets
> in fielded equipment with significant quality issues.  Based on this, we
> are prohibiting use of sockets for new design equipment.  Most military
> equipment prohibits use of sockets (ref historical MIL-STD-2000).  In my
> opinion, no equipment that is intended for long term reliability should
> ever use sockets.
> > >  ----- Original Message -----
> > >  From: Chafin, Ken G.<mailto:[log in to unmask]>   To:
> [log in to unmask]<mailto:[log in to unmask]>   Sent: Wednesday, March 24, 2004
> 5:10 PM
> > >  Subject: [TN] Carbon Buildup On Tin Plated Contacts
> > >
> > >
> > >  Elemental carbon has been identified as the dark material that has
> > >  "developed" on the surface of a pin at the point where it makes
> electrical
> > >  contact with a socket.
> > >
> > >  The applied voltage in one case is 12 VDC and in another it is 5 VDC.
> > >
> > >  It is suspected that the high vibration environment in which the
> device
> > >  operates is causing intermittent opening of the contact area and
> electrical
> > >  arcing is causing the carbon deposition.
> > >
> > >  I believe I have seen literature which identifies atmospheric C0_2 as
> the
> > >  primary source of the carbon (possibly some CO also).
> > >
> > >  Can anyone refer me to literature which confirms, disconfirms or
> otherwise
> > >  provides enlightenment on the precise nature of this process?
> > >
> > >  Thanks
> > >
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