[tinwhiskers] Re: [TN] Tin strikes again!

  • From: "Meschter, Stephan J (US SSA)" <stephan.j.meschter@xxxxxxxxxxxxxx>
  • To: "tinwhiskers@xxxxxxxxxxxxx" <tinwhiskers@xxxxxxxxxxxxx>
  • Date: Mon, 22 Nov 2010 21:12:32 -0500

Hi,

The other place I had heard about pressure induced whiskering was in the 
Japanese research literature. I was not aware of any product recalls though. It 
appeared that earlier than expected tin whisker failures were observed on some 
connector contacts. 

** Mizuguchi et.al. Whisker and Nodule Formation on Lead-Free Tin Plating by 
External Stress, Sony Corp. 2nd CALCE International Tin Whisker Symposium 2008

** Shibutani et.al., Pressure-induced tin whisker formation, Microelectronics 
Reliability 48 (2008) 1033-1039

It might be possible to make some lemonade out of these lemons.
Perhaps each of our companies could keep track of cost (or hours) and product 
impact associated with this issue. Then maybe someone from academia could 
compile it, sanitize it and provide a comprehensive cost case study.

Best regards,
Stephan Meschter
stephan.j.meschter@xxxxxxxxxxxxxx



-----Original Message-----
From: tinwhiskers-bounce@xxxxxxxxxxxxx 
[mailto:tinwhiskers-bounce@xxxxxxxxxxxxx] On Behalf Of Bob Landman
Sent: Friday, November 19, 2010 3:19 PM
To: 'TechNet E-Mail Forum'
Cc: Leadfree@xxxxxxx; tin whiskers forum
Subject: [tinwhiskers] Re: [TN] Tin strikes again!

Thanks so much, Steve, for sharing this vital information.  

This is the first I've heard of this recall.  I noted that Tyco didn't title 
this document as a RECALL but that's what it clearly is.

IMHO, tin plated anything is to be avoided at all costs as there's no such 
thing as a whisker-free tin plating.  NASA has seen them on USB connectors.  
http://nepp.nasa.gov/whisker/photos/index.html  No component manufacturer who 
has made such claims has backed it up with proof we can trust.  

If you read their claims very carefully you see the legal department's help 
craft  their statements.  Real proof, as we see in this sad case, takes YEARS, 
not iNEMI's 4000 hour test (which allows whiskers as long as 50 microns) proves.

What are we manufacturers to do?  

The iNEMI JESD "standard test" gives false hope to us consumers.  It was the 
lowest bar all apparently could agree to.  What good are claims of any 
manufacturer if production can make this kind of mistake?  

Wouldn't you like to know how Tyco let this mistake go on for years 2005-2010 
and why was it only customers detected the whiskers?  

(We use a more expensive 3M part which is gold over nickel over copper, thank 
goodness!)  

Tyco is kidding itself (and the consumers) when it says in the announcement: 
"may have a higher than normal risk of developing tin whiskers".  I'd like Tyco 
to tell us exactly what is a "normal risk of developing tin whiskers"?

Rohm & Hass markets a tin plating solution called "solderon ST-380" which it 
claims: "provides a deposit with low whisker propensity".  If that's true, then 
why doesn't Tyco use it?  Why (in its revised manufacturing spec) does Tyco not 
allow tin on the area of the connector that is subjected to compressive stress?

There are no lot codes on these parts.  Even if there were, how many 
manufacturers track lot numbers in their bills of material?  It would be a 
logistical nightmare.  If they are still in stock (this is unlikely), then they 
can be pulled but once they go into a product, that door is closed forever.

There is no way to find and replace the installed connectors that are affected 
in this recall.  How many products are already failing?  Have there been 
fatalities?    

AIA-PERM has released a whitepaper on the subject recently which states:

"The technical knowledge and data necessary to perform quantitative reliability 
assessments for ADHP lead-free electronic systems do not yet exist. Based on 
our current state of technical understanding, the Steering Committee concludes 
that the
aerospace, defense and high performance electronics industries do not presently 
have the technical knowledge or data necessary to provide a level of confidence 
in reliability assessments for lead-free electronics equal to that currently 
available for traditional tinlead electronics. It is premature to rely solely 
on MIL-STD-810, MIL-HDBK-217, and RTCA DO-160 for qualification of systems 
containing lead-free assemblies in critical, high-reliability, harsh environment
applications without rigorous assessment of application requirements."

Dave Hillman was recently interviewed by Terry Costlow stating: 

The growths, which occur on components that use plated tin surface finishes, 
are a bit more shrouded in mystery than most issues in soldering processes. 
Whiskers usually don't occur until well after manufacturing is completed, and 
it's problematic to predict when they'll grow. It's difficult to figure out 
whether or not they will show up, making them especially vexing in high 
reliability applications like the military or automotive.

"Tin whiskers don't just have one or two causes. A lot of things set them off," 
said Dave Hillman, principal materials and process engineer at Rockwell 
Collins. "We know that stress is a primary driver, but there are still a lot of 
questions about what causes them."

Though it's difficult to tell what causes tin whiskers, their impact can be 
significant. Short circuits are a common problem. Some researchers feel that 
the metallic growths may be overlooked since they can fall off when the board 
is being sent to technicians who examine it to see what's happened. "The real 
question is 'how real is the tin whiskers effect?' When you have a failure 
mechanism, but we don't know its root cause, it's difficult to fix," Hillman 
said. 

Mystery?  We have to obey stupid EU RoHS laws that result in mystery?

Hans Christian Anderson wrote a childrens story that is very apropos, perhaps 
you heard of it? 

"The Emperor's New Clothes"  http://www.youtube.com/watch?v=-ZYzbkk5X4M

Bob Landman
H&L Instruments, LLC
www.hlinstruments.com
LDF Coatings, LLC
www.ldfcoatings.com



-----Original Message-----
From: TechNet [mailto:TechNet@xxxxxxx] On Behalf Of Bush, Jeffrey D. (US SSA)
Sent: Friday, November 19, 2010 10:38 AM
To: TechNet@xxxxxxx
Subject: Re: [TN] Tin strikes again!

It is quite amazing how many components have been switched to >95% tin without 
notification and change of part numbers.  Without a disciplined parts pedigree 
program many contractors have expended major resources on mitigation for PMP 
issues. This issues are more common than most believe and additional events are 
uncovered against legacy safeguards for whisker prevention.   

Jeffrey Bush
Sr. Principle Product Assurance Engineer Space Products and Systems - 
Performance Excellence BAE SYSTEMS P.O. Box 868, MER24-116A Nashua, NH 
03061-0868
Facility: 144 DW Highway
Merrimack, NH 03054
Office +1 603.885.8137
Mobile +1 603.318.8056
Fax +1 603.885.5258


-----Original Message-----
From: TechNet [mailto:TechNet@xxxxxxx] On Behalf Of Steve Gregory
Sent: Friday, November 19, 2010 10:16 AM
To: TechNet@xxxxxxx
Subject: [TN] Tin strikes again!

Morning all!

Before I post the Quiz pictures today, I got something from one of my friends 
back in Tulsa that might interest you if you haven't seen it:

http://stevezeva.homestead.com/Tyco_Letter.pdf

Tin strikes again!

While we're on the subject of whiskers, here are some Inge's more spectacular 
whisker images from a while back:

http://stevezeva.homestead.com/files/daniel121b.jpg

http://stevezeva.homestead.com/files/daniel131b.jpg

http://stevezeva.homestead.com/files/daniel141b.jpg



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