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Tin whisker observation on PS3 BRIR diode

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Proud Mary

Mon May 10 2010, 09:21AM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Steve McConner wrote ...

Metal whiskers aren't a lead-free thing. You see hobbyists who are into vintage radio restoration complain that the old germanium transistors fail because of whiskers growing inside the can and eventually shorting something.

Whisker formation is caused by residual compressive stress.

Appl. Phys. Lett. 93 (2008) 011906.

Selenium whiskers emerging from an Sn-Cu system

1273483205 543 FT88790 Sncuwhiskerformation

Conundrum

Mon May 10 2010, 10:38AM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062

Thats interesting.
I did discover that many of my old "clear" germaniums were DOA, never could figure out why. Thanks for sharing this titbit of knowledge :)

wonder if i can "blow out" the short? or would this just fry the transistor..
depends if it was C-E (easy, just leave base open) as long as the voltage is lower than the reverse breakdown it ought to work fine.

-A

IntraWinding

Mon May 10 2010, 10:45AM

Registered Member #2261 Joined: Mon Aug 03 2009, 01:19AM
Location: London, UK
Posts: 581

BjÃ¸rn wrote ...

Have a look here, conformal coatings can stop whiskers on worst case materials, so on normal materials it will be completely efficient:

Good link. I found this there:

1950s and 60â€™s:
Bell Labs worked through the periodic table to
determine whether addition of some element to
a Tin coating would â€œinhibitâ€ whiskering
â€“ Adding 0.5 - 1% (by weight) or more of
Lead (Pb) into tin inhibits whiskering
â€“ Alloying with metals other than Pb
sometimes ENHANCES whiskering

Surely lead isn't the only thing that works though?

GeordieBoy

Mon May 10 2010, 05:09PM

Registered Member #1232 Joined: Wed Jan 16 2008, 10:53PM
Location: Doon tha Toon!
Posts: 881

> Metal whiskers aren't a lead-free thing. You see hobbyists who are into vintage radio restoration complain that the old germanium transistors fail because of whiskers growing inside the can and eventually shorting something.

Yeah, some of the old kit seems to be the furriest inside...

-Richie,

Conundrum

Mon May 10 2010, 07:32PM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062

ROFL! :)

"Um, dude, the reason it didnt work is that your radio has a fur coat"... What the...

Shame someone can't harvest these things for Z axis interconnects.

In other news,

Amazingly an "old school" trick works wonders.

I read somewhere that people have had great success applying the good old fashoned oven to stubbornly gassy valves and VFDs, it turns out if you get the temperature just right the getter can "clean up" the gas enough to lower the tube's leakage to useable levels.
Can save an otherwise dead tube from the trash.

-A
Who is currently exploring the merits of using Indiglo sheets as scintillators...

hboy007

Mon May 10 2010, 09:53PM

Registered Member #1667 Joined: Sat Aug 30 2008, 09:57PM
Location:
Posts: 374

> Shame someone can't harvest these things for Z axis interconnects.

I bet we will someday see self-organised interconnect structures that need the product to "ripen" some time and after usage it "expires" (shouldn't have thought out loud, now someone WILL use this to cut life span...)

Steve Conner

Tue May 11 2010, 09:13AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

It's already done, any properly designed piece of consumer electronics should self-destruct the day after the warranty runs out. If it outlasts the warranty, that means it was overdesigned.

IntraWinding

Tue May 11 2010, 11:32AM

Registered Member #2261 Joined: Mon Aug 03 2009, 01:19AM
Location: London, UK
Posts: 581

I'm wondering, how do you use this effect to grow nano products of some sort?

Alan

Proud Mary

Tue May 11 2010, 12:05PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

IntraWinding wrote ...

I'm wondering, how do you use this effect to grow nano products of some sort?

Google nano and whiskers and you'll find dozens and dozens of papers on how to grow them, and what might be useful things to do with them.

MinorityCarrier

Tue May 11 2010, 04:06PM

Registered Member #2123 Joined: Sat May 16 2009, 03:10AM
Location: Bend, Oregon
Posts: 312

Recall reading that this problem is much more prevalent with lead-free solders, which are also more brittle. Recall that commercial and military avionics don't use lead free solder for these reliability concerns.

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