Anecdote #3: Field Failures Due to Tin Whiskers Breaking Loose from Matte Tin-Plated RF Enclosure Lids

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Anecdote #3:  Field Failures Due to Tin Whiskers Breaking Loose from Matte Tin-Plated RF Enclosure Lids
Click on the Thumbnails Below to see a Larger Version of the Picture

Source:  Gabriela Bogdan/SANMINA-SCI (Tel Aviv)

Date:       May 2003

This story and images were offered for posting to the NASA Tin and Other Metal Whisker www site. The field failure experience was documented in May 2003.  It describes electrical failures within an RF electronics assembly where TIN WHISKERS growing from the matte tin-plated RF enclosure (package lid) became dislodged.  As loose debris, the whiskers were able to create short circuits across exposed conductors (components) within this enclosure.  Click on the Images Below to Enlarge and Read About This Experience as Told by the RF Assembly Manufacturer  

Tin Whiskers Growing on Matte Tin-Plated RF Enclosure (Lid)
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Tin Whiskers that Dislodged from RF Enclosure 
Becoming Conductive Debris Shorting Hazard to Electronics within the Assembly
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"Dear NASA Whisker Investigators:

When we ordered fences and covers for a RF assembly, our customer specified matte tin, and hoped for the best. We had a supplier in Taiwan and one at home. I don't remember how things developed, but surely not in the right direction. A week ago, our customer brought us  failed assemblies which returned from - anonymous location - after working ~ 1 year. They were puzzled by the following:

One of the fine pitch components showed electrical failure

When the lid was opened, and the component changed with a new one, everything was OK. Then, one smart guy-luckily for me-thought about resoldering the old component, and again-everything was OK. Now they come to us and say- 

"Your solder joints are bad, see, the same one turned ok after resoldering. Try to find bad solder joints on those two which are dead too."

Now, I know these guys, and know that they did not perform any other tests, and are pretty sure that they can blame the solder joints. I took the assembly to the microscope and looked at the solder joints of the component-good shiny ones. Then I tried to find cracks. You know how hard it is to find them, and I used maximum magnification, turned the assembly around, focused on each joint- and then I had a call.  When I returned to the microscope and tried to focus again, I suddenly saw "things" all over the place, and they were metallic, and they were not a result of our process.

Whiskers galore!  Not from the components, not attached to them, but just laying across everything. Remember the fences and lids?  The fences are reflowed around the area during assembly. The lid is attached over the fences by the customer after receiving the assembly from us. Whiskers fell from the lid all over the place in the enclosure.
But what to do now?

SCARY!!!! Assemblies are returned now. Today I checked 2 years old fences under the microscope. SCHWARZWALD! ("Black Forest")  Please look at the pictures. You will enjoy them."

Responsible NASA Officials:

   Michael Sampson/NASA GSFC Code 306
   Dr. Henning Leidecker/NASA GSFC Code 562
Additional Researchers: 

   Jong Kadesch/Orbital Sciences Corp.
   Jay Brusse/Perot Systems

Last Updated:

June 9, 2008

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