Hi Pratap,
The IPC is not the best organization for that, because the technical work is done by committees. but we sure could use some organization 'with cloud.'
Werner
-----Original Message-----
From: Pratap Singh <[log in to unmask]>
To: '(Leadfree Electronics Assembly Forum)' <[log in to unmask]>; 'Werner Engelmaier' <[log in to unmask]>
Sent: Mon, Mar 1, 2010 2:21 pm
Subject: RE: [LF] Expert recreates Toyota sudden acceleration
HiWerner,
Thanks.
TheCAF and general metal migration in PCB has been described in details on pages68, 86, 223 and 225 in Failure Modes and Mechanisms in Electronic Packages’co-authored by me and Viswam. The other terms that have been used by variousauthors are – dendritic growth, conductive migration, conductivecorrosion migration, filament formation, Electromigration etc. These make andbreak mechanisms are exhibited by Ag, Au, Pb, Cu, and Sn commonly used in PCBassembly and packages. My comments were more to the point that in addition toTin Whiskers (a LF issue), other mechanisms are available to cause a shortingfailure. We all need well documented failure analysis of parts from a failed Toyota. Should IPC take alead and provide a helping hand to Toyotato get to the bottom of these events?
pratapsingh
___________________________________
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email:[log in to unmask]
Attached Message
From:
Werner Engelmaier <[log in to unmask]>
To:
[log in to unmask]
Subject:
Re: [LF] Expert recreates Toyota sudden acceleration
Date:
Fri, 26 Feb 2010 20:56:25 -0600
Hi Pratap,
The copper migration' you describe has a name_'conductive anodic filament
(CAF)'.
Werner
-----Original Message-----
From: Pratap Singh <[log in to unmask]>
To: [log in to unmask]
Sent: Fri, Feb 26, 2010 8:21 pm
Subject: Re: [LF] Expert recreates Toyota sudden acceleration
Chuck,
I addition to Tin Whiskers, other possible failure cause can be Copper
Migration. This phenomenon also behaves like a whisker that is it will
create a short, then burn out and grow again. Copper migration has occurred
on PCB surface and internally (PTH to plane). I know it is not politically
correct to say any thing against LF solder caused tin whisker thinking.
There are few other mechanisms in PCB assembly that can cause internal
surface shorts. Tin whisker is just one of the many.
pratap singh
___________________________________
Tel/Fax: 512-255-6820; Cell: 512-663-8903
email: [log in to unmask]
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Now that a plausible train of events has been demonstrated, i.e. a
intermittent short circuit as seen in previous links to demonstration
videos, perhaps it would be beneficial to ask what could cause a short
circuit to exist that would clear itself when the circuit is subjected
to an impact stress? Having seen long tin whiskers in person, and how
they did indeed short out circuitry, I am willing to 'suspend disbelief'
and accept tin whiskers as a possible cause of these failures once we
have evidence of tin whiskers growing in the units, but not before.
Chuck Patten, PMP
Engineer Lead Project
-----Original Message-----
From: Leadfree [mailto:[log in to unmask]] On Behalf Of Marcus L. Thompson
Sent: Friday, February 26, 2010 9:39 AM
To: [log in to unmask]
Subject: Re: [LF] Expert recreates Toyota sudden acceleration
"Doing whatever we can to call attention to this possibility in the
public eye is crucial."
Because the public has essentially no knowledge of this new and
particularly insidious failure mode for electronic systems (tin
whiskers), it's important that we, as a community with superior
knowledge of same, present the issue for examination.
I support taking a tack at this forum which seeks to discuss and
tangibly understand whether or not lead-free is a fitting vector for
these failures; as any such discussions can only serve to deepen our
understanding of the phenomena as a whole. I believe that we all can
benefit from any dialog which further elucidates this issue as it
affects real-world products and systems.
As others have rightly said, silence is what brought the world lead-free
in the first place. Shall we continue here???
Just my 2 cents on a Friday morning --
...
--- Previous Message in This Thread ---
Subject: Re:Expert recreates Toyota sudden acceleration
From: Pete Houwen <[log in to unmask]>
To: [log in to unmask], Marcus Thompson <[log in to unmask]>
Date: Friday, February 26, 2010 7:04:22 AM
> callling attention to unfounded "possibiilities" will be damaging to
any attempts
> to educate on the dangers of lead free solder. Crying wolf will only
destroy
> credibility.
>
> There is NO data, evidence, indications, etc. whatsoever that the
Toyota
> problems are in any way related to tin whiskers or lead free solder.
All
> implications of electronic failure are EMI and software related. Not
even sure
> why this is a topic of discussion on the LeadFree forum.
>
> Pete
>
>
>
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Subject: Re: [LF] Expert recreates Toyota sudden acceleration
Date: Fri, 26 Feb 2010 20:56:25 -0600
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Hi Pratap,
The copper migration' you describe has a name_'conductive anodic filament
(CAF)'.
Werner
-----Original Message-----
From: Pratap Singh <[log in to unmask]>
To: [log in to unmask]
Sent: Fri, Feb 26, 2010 8:21 pm
Subject: Re: [LF] Expert recreates Toyota sudden acceleration
Chuck,
I addition to Tin Whiskers, other possible failure cause can be Copper
Migration. This phenomenon also behaves like a whisker that is it will
create a short, then burn out and grow again. Copper migration has occurred
on PCB surface and internally (PTH to plane). I know it is not politically
correct to say any thing against LF solder caused tin whisker thinking.
There are few other mechanisms in PCB assembly that can cause internal
surface shorts. Tin whisker is just one of the many.
pratap singh
___________________________________
Tel/Fax: 512-255-6820; Cell: 512-663-8903
email: [log in to unmask]
______________________________________________________________________
This email has been scanned by the MessageLabs Email Security System.
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----------------------------------------------------------------------------
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Now that a plausible train of events has been demonstrated, i.e. a
intermittent short circuit as seen in previous links to demonstration
videos, perhaps it would be beneficial to ask what could cause a short
circuit to exist that would clear itself when the circuit is subjected
to an impact stress? Having seen long tin whiskers in person, and how
they did indeed short out circuitry, I am willing to 'suspend disbelief'
and accept tin whiskers as a possible cause of these failures once we
have evidence of tin whiskers growing in the units, but not before.
Chuck Patten, PMP
Engineer Lead Project
-----Original Message-----
From: Leadfree [mailto:[log in to unmask]] On Behalf Of Marcus L. Thompson
Sent: Friday, February 26, 2010 9:39 AM
To: [log in to unmask]
Subject: Re: [LF] Expert recreates Toyota sudden acceleration
"Doing whatever we can to call attention to this possibility in the
public eye is crucial."
Because the public has essentially no knowledge of this new and
particularly insidious failure mode for electronic systems (tin
whiskers), it's important that we, as a community with superior
knowledge of same, present the issue for examination.
I support taking a tack at this forum which seeks to discuss and
tangibly understand whether or not lead-free is a fitting vector for
these failures; as any such discussions can only serve to deepen our
understanding of the phenomena as a whole. I believe that we all can
benefit from any dialog which further elucidates this issue as it
affects real-world products and systems.
As others have rightly said, silence is what brought the world lead-free
in the first place. Shall we continue here???
Just my 2 cents on a Friday morning --
...
--- Previous Message in This Thread ---
Subject: Re:Expert recreates Toyota sudden acceleration
From: Pete Houwen <[log in to unmask]>
To: [log in to unmask], Marcus Thompson <[log in to unmask]>
Date: Friday, February 26, 2010 7:04:22 AM
> callling attention to unfounded "possibiilities" will be damaging to
any attempts
> to educate on the dangers of lead free solder. Crying wolf will only
destroy
> credibility.
>
> There is NO data, evidence, indications, etc. whatsoever that the
Toyota
> problems are in any way related to tin whiskers or lead free solder.
All
> implications of electronic failure are EMI and software related. Not
even sure
> why this is a topic of discussion on the LeadFree forum.
>
> Pete
>
>
>
______________________________________________________________________
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