Hi Pat and gang - good information as our "industry attention" on the
topic of tin whiskers pre-1997 was not at the same level of scrutiny as we
have today. This failure, if it has a tin whisker root cause, is a
demonstration of two things: (1) the breakdown of system rules prohibiting
the use of pure tin in a space application. NASA has always attempted to
avoid the use of pure tin due to the tin whisker risk. There may have been
a simple human error or this could have been a lack of knowledge by a
supplier; (2) the lack of a tin whisker mitigation strategy. If there was
going to be the use of pure tin in a space application, was a tin whisker
mitigation methodology missed - such as pretinning the leads, adequate
design spacing or the use of a coating material to capture/contain the
whiskers? Easy to second guess what happened. Hopefully, further details
of the story will be published so that we can learn from the issue.
Dave Hillman
Rockwell Collins
[log in to unmask]
"Goodyear, Patrick" <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
03/20/2012 02:33 PM
Please respond to
TechNet E-Mail Forum <[log in to unmask]>; Please respond to
"Goodyear, Patrick" <[log in to unmask]>
To
<[log in to unmask]>
cc
Subject
Re: [TN] Out of the world tin whiskers
To answer my own question.
Cassini was launched October 15,1997, so it was most likely built in
'96-'97 timeframe. I don't think lead free had hit the streets by then
except for applications in plumbing. Whiskers had been an issue long
before that, at least in my industry. We have been inspecting for them
since around 1992, we tripped a unit in 1988 due to a whisker in a relay,
shorting out a contact that should have opened when the relay energized.
pat
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Goodyear, Patrick
Sent: Tuesday, March 20, 2012 11:11 AM
To: [log in to unmask]
Subject: Re: [TN] Out of the world tin whiskers
But Cassini is a bunch of years old, at least 10 I think. The components
are most likely plated leads on diodes or tin canned pots.
Pat
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Dale Ritzen
Sent: Tuesday, March 20, 2012 11:00 AM
To: [log in to unmask]
Subject: Re: [TN] Out of the world tin whiskers
Joyce,
I know your question below is basically rhetorical, but have you tried to
find a component without a Pb-free coating on it lately... That is,
unfortunately, why there are Pb-free components on spacecraft... and
obviously tin whiskers.
Dale Ritzen, CQA
Quality Manager / ISO Management Representative Austin Manufacturing
Services
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Joyce Koo
Sent: Tuesday, March 20, 2012 12:57 PM
To: [log in to unmask]
Subject: Re: [TN] Out of the world tin whiskers
I thought space is exempt for leadfree. Why?
--------------------------
Sent using BlackBerry
----- Original Message -----
From: Inge Hernefjord [mailto:[log in to unmask]]
Sent: Tuesday, March 20, 2012 01:47 PM
To: [log in to unmask] <[log in to unmask]>
Subject: Re: [TN] Out of the world tin whiskers
DO THEY NEVER LEARN!
Inge
On 20 March 2012 18:08, Gervascio, Thomas L
<[log in to unmask]>wrote:
> Tin whiskers at Saturn
>
> PASADENA, Calif. -- The Cassini plasma spectrometer instrument (CAPS)
> aboard NASA's Cassini spacecraft at Saturn has resumed operations.
> Mission managers received confirmation on Friday, March 16, that it was
turned on.
> They plan to monitor the instrument for any unusual behavior.
> Last June, short circuits in the instrument led to unexpected voltage
> shifts on the spacecraft. As a precaution, mission managers turned off
> the CAPS instrument while engineers investigated the issue. The
> investigation led to the conclusion that tin plating on electronics
> components had grown "whiskers." The whiskers were very small, less
> than the diameter of a human hair, but they were big enough to contact
> another conducting surface and carry electrical current. Researchers
> are still trying to understand why whiskers grow on tin and other
> metals, but they know now that whiskers can grow in space and on
> Earth. It is believed that these or additional tin whiskers that may
> grow on Cassini cannot carry enough current to cause problems, but will
burn out on their own like a lightweight fuse.
>
>
>
> ______________________________________________________________________
> This email has been scanned by the Symantec Email Security.cloud
service.
> For more information please contact helpdesk at x2960 or
> [log in to unmask]
> ______________________________________________________________________
>
______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask]
______________________________________________________________________
---------------------------------------------------------------------
This transmission (including any attachments) may contain confidential
information, privileged material (including material protected by the
solicitor-client or other applicable privileges), or constitute non-public
information. Any use of this information by anyone other than the intended
recipient is prohibited. If you have received this transmission in error,
please immediately reply to the sender and delete this information from
your system. Use, dissemination, distribution, or reproduction of this
transmission by unintended recipients is not authorized and may be
unlawful.
______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask]
______________________________________________________________________
______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask]
______________________________________________________________________
______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask]
______________________________________________________________________
______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask]
______________________________________________________________________
______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask]
______________________________________________________________________
|
