Forums

Old Ge transistors and Whiskers

Started by Chris M. White November 28, 2021
Hi,

Anyone know if NOS (old, but never used) germanium transistors are
prone to forming whiskers to the same extent as used ones? I'm not
sure if it's a phenomenon which arises from the electrical potential
applied during the service life of the device or not. Anyone know?

Chris.
On Sunday, November 28, 2021 at 9:35:21 PM UTC-4, Chris M. White wrote:
> Hi, > > Anyone know if NOS (old, but never used) germanium transistors are > prone to forming whiskers to the same extent as used ones? I'm not > sure if it's a phenomenon which arises from the electrical potential > applied during the service life of the device or not. Anyone know?
I don't know for sure, but I've never heard that metallic whiskers were grown by electrical potential. I believe it is just a metallurgical matter. -- Rick C. - Get 1,000 miles of free Supercharging - Tesla referral code - https://ts.la/richard11209
In article <ed720d84-43f7-4e79-8eb9-527ae3fc671bn@googlegroups.com>, 
gnuarm.deletethisbit@gmail.com says...
> Anyone know if NOS (old, but never used) germanium transistors are > > prone to forming whiskers to the same extent as used ones? I'm not > > sure if it's a phenomenon which arises from the electrical potential > > applied during the service life of the device or not. Anyone know? > > I don't know for sure, but I've never heard that metallic whiskers were grown by electrical potential. I believe it is just a metallurgical matter. > >
I aagree. Some old GE comercial radios would do that in the tuned cavities and there is no power in them.
On Monday, November 29, 2021 at 12:35:21 PM UTC+11, Chris M. White wrote:
> Hi, > > Anyone know if NOS (old, but never used) germanium transistors are > prone to forming whiskers to the same extent as used ones? I'm not > sure if it's a phenomenon which arises from the electrical potential > applied during the service life of the device or not. Anyone know? >
**See: https://nepp.nasa.gov/whisker/anecdote/af114-transistor/index.html ** Seems it's related to age, not usage. ...... Phil
On Monday, November 29, 2021 at 1:16:24 AM UTC-4, palli...@gmail.com wrote:
> On Monday, November 29, 2021 at 12:35:21 PM UTC+11, Chris M. White wrote: > > Hi, > > > > Anyone know if NOS (old, but never used) germanium transistors are > > prone to forming whiskers to the same extent as used ones? I'm not > > sure if it's a phenomenon which arises from the electrical potential > > applied during the service life of the device or not. Anyone know? > > > **See: > > https://nepp.nasa.gov/whisker/anecdote/af114-transistor/index.html > > ** Seems it's related to age, not usage.
My understanding is these whiskers are very fragile requiring only a tiny current to remove them. It is mentioned on one of the NASA pages how measuring the short with a standard ohm meter is enough to clear the short. It seems the short would be cleared by the currents flowing in most circuits the devices would be used in. No? -- Rick C. - Get 1,000 miles of free Supercharging - Tesla referral code - https://ts.la/richard11209
On 29/11/2021 22:42, Rick C wrote:
> On Monday, November 29, 2021 at 1:16:24 AM UTC-4, palli...@gmail.com wrote: >> On Monday, November 29, 2021 at 12:35:21 PM UTC+11, Chris M. White wrote: >>> Hi, >>> >>> Anyone know if NOS (old, but never used) germanium transistors are >>> prone to forming whiskers to the same extent as used ones? I'm not >>> sure if it's a phenomenon which arises from the electrical potential >>> applied during the service life of the device or not. Anyone know? >>> >> **See: >> >> https://nepp.nasa.gov/whisker/anecdote/af114-transistor/index.html >> >> ** Seems it's related to age, not usage. > > My understanding is these whiskers are very fragile requiring only a tiny current to remove them. It is mentioned on one of the NASA pages how measuring the short with a standard ohm meter is enough to clear the short. It seems the short would be cleared by the currents flowing in most circuits the devices would be used in. No? >
No. Murphy's law and all that. Often the circuit dows not supply enough current to clear the short, and in other cases, a lot of current is available and the whisker starts an arc that vapourises big important parts of the equipment. I've seen quite a few whiskers, but so far always on very old (pre-1970) equipment. I've not yet seen any on RoHS compliant stuff. I wonder if it is just that the whiskers grow slowly, or if they used worse kinds of plating a long time ago.
On Sunday, November 28, 2021 at 9:35:21 PM UTC-4, Chris M. White wrote:
> Hi, > > Anyone know if NOS (old, but never used) germanium transistors are > prone to forming whiskers to the same extent as used ones? I'm not > sure if it's a phenomenon which arises from the electrical potential > applied during the service life of the device or not. Anyone know?
I didn't know tin whiskers had impacted the nuclear power industry. Seems, as is not uncommon, they didn't think events that affect other industries would impact them. The effect of tin whiskers was first documented in 1951 and satellites were lost due to tin whiskers as early as 1998. Medical implants were recalled in 1984 for tin whisker defects. Methods of mitigating tin whiskers were developed in 1974. Yet, it was allowed to impact the nuclear power industry directly right up to 2005. Right up until they had a reactor scram at Millstone, CT the nuclear industry believed they were immune from the effect or more accurately kept their head in the sand while other industries were hit by the issue. No wonder the nuclear industry is not much trusted. -- Rick C. + Get 1,000 miles of free Supercharging + Tesla referral code - https://ts.la/richard11209
On Monday, November 29, 2021 at 8:47:25 AM UTC-4, Chris Jones wrote:
> On 29/11/2021 22:42, Rick C wrote: > > On Monday, November 29, 2021 at 1:16:24 AM UTC-4, palli...@gmail.com wrote: > >> On Monday, November 29, 2021 at 12:35:21 PM UTC+11, Chris M. White wrote: > >>> Hi, > >>> > >>> Anyone know if NOS (old, but never used) germanium transistors are > >>> prone to forming whiskers to the same extent as used ones? I'm not > >>> sure if it's a phenomenon which arises from the electrical potential > >>> applied during the service life of the device or not. Anyone know? > >>> > >> **See: > >> > >> https://nepp.nasa.gov/whisker/anecdote/af114-transistor/index.html > >> > >> ** Seems it's related to age, not usage. > > > > My understanding is these whiskers are very fragile requiring only a tiny current to remove them. It is mentioned on one of the NASA pages how measuring the short with a standard ohm meter is enough to clear the short. It seems the short would be cleared by the currents flowing in most circuits the devices would be used in. No? > > > No. Murphy's law and all that. Often the circuit dows not supply enough > current to clear the short, and in other cases, a lot of current is > available and the whisker starts an arc that vapourises big important > parts of the equipment. > > I've seen quite a few whiskers, but so far always on very old (pre-1970) > equipment. I've not yet seen any on RoHS compliant stuff. I wonder if it > is just that the whiskers grow slowly, or if they used worse kinds of > plating a long time ago.
Mostly they used tin-lead solder in the good old days which is not subject to tin whiskers. RoHS compliant, lead free solder is exactly the material that grows tin whiskers. Seems pure tin coatings have also been used though. The can around a pacemaker was the cause of a recall when the can maker messed up and shipped a batch that was tin plated. The company using the cans did not test the coating. What parts of pre-1970 equipment developed tin whiskers? Was it non-electrical components? -- Rick C. -- Get 1,000 miles of free Supercharging -- Tesla referral code - https://ts.la/richard11209
On Mon, 29 Nov 2021 04:56:28 -0800 (PST), Rick C
<gnuarm.deletethisbit@gmail.com> wrote:

>On Monday, November 29, 2021 at 8:47:25 AM UTC-4, Chris Jones wrote: >> On 29/11/2021 22:42, Rick C wrote: >> > On Monday, November 29, 2021 at 1:16:24 AM UTC-4, palli...@gmail.com wrote: >> >> On Monday, November 29, 2021 at 12:35:21 PM UTC+11, Chris M. White wrote: >> >>> Hi, >> >>> >> >>> Anyone know if NOS (old, but never used) germanium transistors are >> >>> prone to forming whiskers to the same extent as used ones? I'm not >> >>> sure if it's a phenomenon which arises from the electrical potential >> >>> applied during the service life of the device or not. Anyone know? >> >>> >> >> **See: >> >> >> >> https://nepp.nasa.gov/whisker/anecdote/af114-transistor/index.html >> >> >> >> ** Seems it's related to age, not usage. >> > >> > My understanding is these whiskers are very fragile requiring only a tiny current to remove them. It is mentioned on one of the NASA pages how measuring the short with a standard ohm meter is enough to clear the short. It seems the short would be cleared by the currents flowing in most circuits the devices would be used in. No? >> > >> No. Murphy's law and all that. Often the circuit dows not supply enough >> current to clear the short, and in other cases, a lot of current is >> available and the whisker starts an arc that vapourises big important >> parts of the equipment. >> >> I've seen quite a few whiskers, but so far always on very old (pre-1970) >> equipment. I've not yet seen any on RoHS compliant stuff. I wonder if it >> is just that the whiskers grow slowly, or if they used worse kinds of >> plating a long time ago. > >Mostly they used tin-lead solder in the good old days which is not subject to tin whiskers. RoHS compliant, lead free solder is exactly the material that grows tin whiskers. Seems pure tin coatings have also been used though. The can around a pacemaker was the cause of a recall when the can maker messed up and shipped a batch that was tin plated. The company using the cans did not test the coating. > >What parts of pre-1970 equipment developed tin whiskers? Was it non-electrical components?
Certain products were more affected than others. IIRC the AF117 found in large numbers of early transistor radios was particularly prone to growing whiskers. A typical remedy involves tying EBC together and then zapping a HV cap between them and the screen. Use enough voltage and you can pretty much vaporise the whiskers. They will grow back again in time, but this method usually 'fixes' the problem for several years. -- "In one word, you reproach us with intending to do away with your property. Precisely so; that is just what we intend." - The Communist Manifesto, Marx & Engels.
Chris Jones <lugnut808@spam.yahoo.com> wrote:
> On 29/11/2021 22:42, Rick C wrote: >> On Monday, November 29, 2021 at 1:16:24 AM UTC-4, palli...@gmail.com wrote: >>> On Monday, November 29, 2021 at 12:35:21 PM UTC+11, Chris M. White wrote: >>>> Hi, >>>> >>>> Anyone know if NOS (old, but never used) germanium transistors are >>>> prone to forming whiskers to the same extent as used ones? I'm not >>>> sure if it's a phenomenon which arises from the electrical potential >>>> applied during the service life of the device or not. Anyone know? >>>> >>> **See: >>> >>> https://nepp.nasa.gov/whisker/anecdote/af114-transistor/index.html >>> >>> ** Seems it's related to age, not usage. >> >> My understanding is these whiskers are very fragile requiring only a tiny current to remove them. It is mentioned on one of the NASA pages how measuring the short with a standard ohm meter is enough to clear the short. It seems the short would be cleared by the currents flowing in most circuits the devices would be used in. No? >> > > No. Murphy's law and all that. Often the circuit dows not supply enough > current to clear the short, and in other cases, a lot of current is > available and the whisker starts an arc that vapourises big important > parts of the equipment. > > I've seen quite a few whiskers, but so far always on very old (pre-1970) > equipment. I've not yet seen any on RoHS compliant stuff. I wonder if it > is just that the whiskers grow slowly, or if they used worse kinds of > plating a long time ago.
I've seen them on post year 2000 equipment that wasn't RoHS. They're real odd and far too small to play with. Even true needle point meter probes are too big.