[tinwhiskers] Re: FW: Why they grow? Getting to the roots of lethal metal whiskers

  • From: "Fritz, Dennis D." <DENNIS.D.FRITZ@xxxxxxxx>
  • To: <tinwhiskers@xxxxxxxxxxxxx>
  • Date: Thu, 1 Oct 2009 14:44:16 -0400

Thanks for posting.  I had heard some work from Germany was presented at the 
CALCE seminar in Denmark back in June.  This may close the gap on what that 
was.  I have asked the Purdue University attendees at the Denmark session if 
this is what was presented.  
 
Denny Fritz

________________________________

From: tinwhiskers-bounce@xxxxxxxxxxxxx on behalf of John Burke
Sent: Thu 10/1/2009 2:17 PM
To: tinwhiskers@xxxxxxxxxxxxx
Subject: [tinwhiskers] FW: Why they grow? Getting to the roots of lethal metal 
whiskers


This in from Klauss FYI
 

John Burke

(408) 515 4992

 

 

________________________________

From: Klaus Reindl [mailto:klaus-reindl@xxxxxxxxxxx] 
Sent: Thursday, October 01, 2009 2:26 AM
To: 'John Burke'
Subject: Why they grow? Getting to the roots of lethal metal whiskers



Why they grow? Getting to the roots of lethal metal whiskers


 Getting to the roots of lethal 
hairs<https://mclmail.saic.com/exchange/fritzdd/Drafts/RE:%20[tinwhiskers]%20FW:%20Why%20they%20grow_x003F_%20Getting%20to%20the%20roots%20of%20lethal%20metal%20whiskers.EML/1_multipart/image002.jpg>
 September 29th, 2009 

Enlarge <http://www.physorg.com/newman/gfx/news/hires/2-Web_Zoom.jpeg> 

 

 

 

 

 

(a) This image from an ion beam microscope shows the growth morphology of a tin 
whisker. (b) A model of the forces that cause spontaneous whisker growth on 
tin-plated copper. The tin coating is a few micrometres thick. Image: Max 
Planck Institute for Metals Research, Stuttgart

(PhysOrg.com) -- A short circuit can be quite hairy: satellites have failed, a 
NASA computer centre was repeatedly paralysed and the US public heath authority 
recalled thousands of pacemakers - all because tin whiskers caused a short 
circuit in the electronic components of these devices. 

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A team of scientists from the Max Planck Institute for Metals Research has been 
working with Robert Bosch GmbH to measure the forces that trigger this metallic 
hair growth. Tin whiskers can be up to a few millimetres long and just a few 
micrometres in diameter. They sprout from the tin used to solder and plate 
electronic components <http://www.physorg.com/tags/electronic+components/>  
made of copper. Understanding in detail what makes the whiskers grow is the 
first step on the way to preventing their growth. (Applied Physics Letters, 
June 2009)

The systems in a NASA computer centre failed after new data storage had been 
installed; at least 18 short circuits occurred in the high-performance 
computers before technicians found the reason: the replacement of the storage 
devices dislodged metal whiskers from the base construction and their 
subsequent distribution via air circulation caused system failure by bridging 
the electrical circuits of the supercomputers.

Researchers working with Eric J. Mittemeijer at the Max Planck Institute for 
Metals Research together with colleagues from the Robert Bosch GmbH, Argonne 
National Laboratory in Illinois and Oak Ridge National Laboratory in Tennessee 
have revealed the forces that cause these whiskers to sprout from tin-plated 
copper. According to their findings, the pressure of the tin atoms at the base 
of the film needs to be higher than at the surface. At the same time, there 
must be a pressure difference on the film's surface plane: The pressure at the 
root of the tin whisker must be lower than it is further away. "You can compare 
it to a toothpaste tube," says Matthias Sobiech, who carried out the 
experiments. "When you press the sides, toothpaste comes out of the top." The 
pressure, which physicists also call stress, is created because an 
intermetallic tin-copper compound forms at the tin-copper interface that grows 
further into the tin film. 

X-ray investigations provided a detailed picture of the distribution of the 
stress in the tin film. The researchers determined the stress differences 
between the base and the surface of the tin film in their laboratory in 
Stuttgart by measuring step by step the vertical mechanical stresses. In order 
to measure the distribution of stress in the surface plane around a growing 
whisker, the researchers had to use a method with very high spatial resolution 
in the sub-micron range. These micro stress measurements were taken using the 
synchrotron at the Advanced Photon Source at Argonne National Laboratory by 
means of the Micro Laue Diffraction method: A very fine beam of X-rays, around 
300 nanometres in diameter, scanned the surroundings of a growing tin whisker 
in very small steps, and a sensitive detector very precisely recorded the local 
stresses at each probed position. 


 

John, maybe you can it distribute in your group?

 

Best regards,

 

Klaus G. Reindl

rRC

Reliable Reliability Consulting

Seitenhalde 108/2

D 72793 Pfullingen

xx49 7121 799533

klaus-reindl@xxxxxxxxxxx

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