Author Topic: Modern Marvels - Tin Whiskers  (Read 2296 times)

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Offline Falcon69

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Modern Marvels - Tin Whiskers
« on: April 11, 2015, 06:07:46 am »

I just saw an episode on Modern Marvels of the problem in the electronics industry regarding Tin Whiskers.

They said that temperature plays a big part in the Tin Whisker Problem, but not limited to just temperature.

They mentioned that they are crystalline in structure, and actually grow over time, thus, creating shorts.  Lead was introduced into the soldering alloy to slow down this process (though, they said it only SLOWS down the process, so Sn/Pb can have Tin Whiskers as well). But, because of the obvious problems with lead, manufacturers still use the tin only solder, i.e. Lead Free Solder.

I had no idea that they grow over time, I thought it was just a process of the actual soldering process that created them, and components need to be inspected afterwards and cleaned to prevent shorts.

They've found tin whiskers, they said, in satellites, F-15's, Missiles, Pace Makers, and more. Sounds pretty dangerous.

If this is happening in vital life sustaining electronics equipment, i.e. pace makers, why are manufacturers still using lead free in these? 

The show mentioned that scientists still can't figure out how to stop this from happening with the tin solder.

Offline Psi

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Re: Modern Marvels - Tin Whiskers
« Reply #1 on: April 11, 2015, 06:20:53 am »
Yep, they grow!  and the process behind it is still not understood.

Here's a video of one growing under a electron microscope

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Offline cimmo

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Re: Modern Marvels - Tin Whiskers
« Reply #2 on: April 11, 2015, 07:41:54 am »
A tiny bit of lead in the solder makes no difference to the environment - especially compared to the millions of tonnes sitting around in lead-acid batteries.

No, this scam was perpetrated by the equipment manufacturers in conjunction with the green lobby. A perfect way of ensuring your overly complicated gadget with device pin spacing of 0.4mm (or less?) will fail and need replacement. The fact that tin whisker growth rates will almost certainly guarantee no failures due to this cause within the warranty period is just the icing on the cake.
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Online T3sl4co1l

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Re: Modern Marvels - Tin Whiskers
« Reply #3 on: April 11, 2015, 07:58:04 am »
Note that Modern Marvels is quite an old show these days!  (Are they still even active?  Is there even any history still on the "History" channel? :-DD )

The late 2000s carried a lot of lead-free hoopla, but with lead-free smartphones, computers and all other manner of materiel and equipment being produced in this way, it seems the fears were indeed completely unfounded.

Not to deny the phenomena, of course -- but, it seems, things are now more robust than ever.

What it comes down to, the most, is the same with much industrial production: process control.  Alloys are more accurately formulated, more uniformly applied, and activated according to stringent temperature profiles.

Quality RoHS assemblies actually appear to be stronger (indeed, the alloys are stronger, if somewhat more prone to cracking*) and more reliable!

The difference is that it's a stronger differentiator, so cheap production will have worse quality, and will succumb to such maladies as whiskers and fractures.

*Especially in some exceptional cases, like the infamous Xbox.  That would be more properly blamed on poor thermal management, however.  While a leaded process might not've failed in the same way, or as easily, the excessive temperature and cycling is still a key factor, in any kind of product -- from pure mechanical systems (car engines, anyone?) to top tech computer chips (the chips alone, nevermind the PCB assemblies they're ultimately mounted to).  It was poor system-level design, only a matter of time.

Electrolytic capacitors share a similar morbidity, though from operating temperatures alone, not cycling as well.  There were also some batches of these components, in the mid to late 2000s, that ranged from bad to terrible.  To this day, poorly specified, formulated or designed** electronics continue the same pattern, anyway.

(**To be fair, engineering is a holistic field, including product cost and life cycle.  If marketing declares that 95% of the product must outlive the 90 day warranty, it's only good engineering to make it as close to 95% as possible.  This is perhaps one of the more... "neutrally moral" aspects of "engineering" as such.)

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