I have just received the following interesting email from Jay Brusse at Nasa:
Quote:
Subject: The Verdict is.... they are TIN Whiskers inside AF114!!!
Dear Paul,
Sorry for our delay in analyzing the AF114 Germanium transistors you sent to us some weeks ago. I've attached some PRELIMINARY info (Power Point Slide Show) from our analysis of 1 of the 4 parts you sent to us. Our analysis to date confirms the following:
Metal whiskers are growing profusely from the internal surface of the TO package.
Materials analysis confirms that the whiskers are TIN.
The external surface of the can is also TIN (but no whiskers noted).
Due to the geometry of the opened package, we have not yet been able to document that the INTERNAL surface is tin, but it is a logical conclusion that this will be the case. Still we would need to dissect the can a bit further in order to allow our instrument detectors to "see" this surface. We are not yet pursuing this analysis as we first contemplate any other examinations we might like to do before more dissection.
Whiskers are bridging from case wall to the internal pins. Some nice dissection work by my co-worker, Mr. Chris Greenwell, has left shorting whiskers intact for photo-documentation.
Whiskers do grow readily through the 'grease' (suspect Silicone based?). We are contemplating techniques to more clearly photo-document this fact (photos included are not as good as we'd like to make this point) such as by cutting off the top of the already opened can to enable us to better illuminate the whiskers within the grease.
I hope you don't mind, but I am distributing this same initial information to a 'tin whisker' email forum I participate in. They have expressed a high degree of interest in "seeing" what I have "told" them thus far. For more permanent archival, I hope to post an "anecdote" of some form to the NASA whisker www site in the not too distant future. Our site is TEMPORARILY down for logistical maintenance matters (hope to be back soon?!?!)
Many thanks again, Paul, for your kind contribution. I certainly owe you one (or two or three depending on how much you like your liquor). I will keep you informed of any additional info we learn from your specimens.
Sincerely,
Jay
Jay Brusse
QSS Group at NASA Goddard
Sr. Components Engineer
|
The PowerPoint slideshow mentioned is too large to attach to this message (approx 2.5MB) so I have uploaded it to
this new page on my Vintage Radio Information site. I have also created a PDF version for those who do not have PowerPoint installed, which is available on the same page.
Please take a look - some of the photos are fascinating!