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Tin Whiskers


hilldweller
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I've just been browsing the t'internet and come across a reference to the dangers posed to consumer electronics by "tin whiskers".

It would seem that since the E C and various other authorities banned the use of lead in solder, faults caused by tin whiskers are causing problems with consumer and industrial electronics.

It appears that solders formulated without the use of lead eventually grow "whiskers" of pure tin that can easily short out digital signal levels.

The "elf & safety" brigade sucessfully lobbied to bring in lead free solders a few years ago and since then multi-million pound satellites have failed and the Swatch watch company have had to bin about a million dollars of stock due to the problem.

It appears that NASA and Swatch have obtained dispensations to use leaded solder again.

We poor consumers are stuck with built in failure mechanisms in our consumer electronics.

Isn't progress wonderful.

I must say that the only occurances I have seen are on soldered plumbing fittings made with lead free solder where I have seen whiskers growing from the joints.

HD

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Swatch - a slightly bigger problem than first estimated ...

I've just been browsing the t'internet and come across a reference to the dangers posed to consumer electronics by "tin whiskers".

It would seem that since the E C and various other authorities banned the use of lead in solder, faults caused by tin whiskers are causing problems with consumer and industrial electronics.

It appears that solders formulated without the use of lead eventually grow "whiskers" of pure tin that can easily short out digital signal levels.

The "elf & safety" brigade sucessfully lobbied to bring in lead free solders a few years ago and since then multi-million pound satellites have failed and the Swatch watch company have had to bin about a million dollars of stock due to the problem.

It appears that NASA and Swatch have obtained dispensations to use leaded solder again.

We poor consumers are stuck with built in failure mechanisms in our consumer electronics.

Isn't progress wonderful.

I must say that the only occurances I have seen are on soldered plumbing fittings made with lead free solder where I have seen whiskers growing from the joints.

HD

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So the Swatch company lost a billion dollars, rather than a million.

What's three orders of magnitude between friends.

Was it just coincidence that 30 minutes after I posted this item, my DVD recorder died on me.

It's only 9 months old 'so at least it's under warrenty.

HD

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I've just been browsing the t'internet and come across a reference to the dangers posed to consumer electronics by "tin whiskers".

It would seem that since the E C and various other authorities banned the use of lead in solder, faults caused by tin whiskers are causing problems with consumer and industrial electronics.

It appears that solders formulated without the use of lead eventually grow "whiskers" of pure tin that can easily short out digital signal levels.

The "elf & safety" brigade sucessfully lobbied to bring in lead free solders a few years ago and since then multi-million pound satellites have failed and the Swatch watch company have had to bin about a million dollars of stock due to the problem.

It appears that NASA and Swatch have obtained dispensations to use leaded solder again.

We poor consumers are stuck with built in failure mechanisms in our consumer electronics.

Isn't progress wonderful.

I must say that the only occurances I have seen are on soldered plumbing fittings made with lead free solder where I have seen whiskers growing from the joints.

HD

They need to get a proper chemist to formulate the solder alloy for them then, and not some mug from the 'elf & safety.

Why is leaded solder such a risk when it is part of a circuit board fully enclosed within the device and otherwise inaccesible? Or is it just a risk to the workers, paid the equivalent of 4p a year for soldering the things up in a sweat shop foreign facyory? Molten solder will give off toxic lead vapour.

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Was it just coincidence that 30 minutes after I posted this item, my DVD recorder died on me.

It's only 9 months old 'so at least it's under warrenty.

HD

Has it died of tin whiskers on the soldered joints causing shorting problems? :rolleyes:

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It appears that solders formulated without the use of lead eventually grow "whiskers" of pure tin that can easily short out digital signal levels.

Tin Whiskers?

Many of us older radio enthusiasts (that's me and you HD ;-) ) probably started our interested in radio by building our own first radio as a "crystal set" which used a Cats Whisker as a detector. If I remember rightly the cats whisker contained a thin metal "whisker" in contact with another material which out the junction had a rectifying effect on radio frequencies.

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Tin Whiskers?

Many of us older radio enthusiasts (that's me and you HD ;-) ) probably started our interested in radio by building our own first radio as a "crystal set" which used a Cats Whisker as a detector. If I remember rightly the cats whisker contained a thin metal "whisker" in contact with another material which out the junction had a rectifying effect on radio frequencies.

I think most young lads "cheated" and used a OA81 germanium diode.

I did manage to purchase an original commercially made cat's whisker detector from a tiny shop at the bottom of West Street in the fifties.

The "crystal" of I think, Galena, was set in a little brass cup with "Wood's Metal".

The spring loaded cat's whisker was made of something that looked like phossy bronze, with a sharp point.

It needed very careful positioning and was never as good as a germanium diode, You had only to cough and it stopped working.

You also needed to procure the "three noughts five microfarad" (500 pF) variable tuning capacitor and wind a suitable coil.

All those hours spent listening to Radio Luxembourg with headphones and a long-wire aerial from my attic window across to the outside lavatory roof at the top of the yard.

The best 'phones were made by S. G. Browns with a resistance of about 4,000 ohms, but I had to make do with a pair of low impedance WW2 bomber wireless operator phones, with the throat-mike removed.

HD

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I did manage to purchase an original commercially made cat's whisker detector from a tiny shop at the bottom of West Street in the fifties.

The "crystal" of I think, Galena, was set in a little brass cup with "Wood's Metal".

The spring loaded cat's whisker was made of something that looked like phossy bronze, with a sharp point.

It needed very careful positioning and was never as good as a germanium diode, You had only to cough and it stopped working.

I can't remember how I managed to come by a long obsolete cats whisker when I started with radio around 1967-8 but the one I had was exactly as you describe it here in terms of construction although I was a bit luckier in that mine was not that temperamental once set up. It either worked or it didn't. If it didn't you could spend ages fiddling about with it and moving the crystal until it did, - then it just carried on working.

The crystal set crystal was indeed Galena, lead sulphide which is an ore of lead. The whisker just had to be a piece of metal to make a point contact, but as it was spring loaded and had to be firmly held in place without bending / moving (hence the tempremental behaviour?) it had to be a fairly strong piece of metal so phosphor bronze was probably the material of choice. Not so sure about the Wood's Metal though, - this is a particularly low melting point eutectic alloy of already low melting, and quite toxic metals. It melts at around 70 degC, so it would melt in hot water. It was used to make the teaspoons sold in joke shops which melted when you stirred your hot cup of tea to dissolve the sugar. Silly really given the toxicity of the metals and where you were melting it.

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The best 'phones were made by S. G. Browns with a resistance of about 4,000 ohms, but I had to make do with a pair of low impedance WW2 bomber wireless operator phones, with the throat-mike removed. HD

Most Hi-Fi headphones were designed to work at low impedance and had impedences of either 4 or 8 ohms. They were useless for radio work requiring high sensitivty to very weak signals as would be the case with simple, home made amateur SW radios.

I did manage to get an earpiece for 1 ear which had an impedence of 8000 ohms which was good but unconfortable.

However, both the HAC (Hear All Continents) SW valve radio kits and the CODAR communications receivers came with identical sets of cheap 4000 ohm headphones that were fit for purpose and worked well. The sound quality was not great but the tone they provided allowed the required sound to cut through the radio noise better so were ideal for picking up weak distant stations.

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The crystal set crystal was indeed Galena, lead sulphide which is an ore of lead. The whisker just had to be a piece of metal to Not so sure about the Wood's Metal though, - this is a particularly low melting point eutectic alloy of already low melting, and quite toxic metals. It melts at around 70 degC, so it would melt in hot water. It was used to make the teaspoons sold in joke shops which melted when you stirred your hot cup of tea to dissolve the sugar. Silly really given the toxicity of the metals and where you were melting it.

I have several old books from the early radio era. Everymans Wireless Book by F.J. Camm, Foundations of Wireless by M. G. Scroggie.

Somewhere I have a Admiralty manual that covers spark transmitters and "Coherers". We made a simple coherer from a glass tube filled with filings from an old silver sixpence and coupled it to a torch bulb and a 4.5 volt battery.

Our spark transmitter would have given a "elf & safety" bloke apoplexy.

The results were reasonably conclusive but variable.

The Admiralty book measures capacitance in "Jars" rather than sub divisions of Farads.

Apparently Wood's Metal was used because it secured the Galena without subjecting it to mechanical or thermal stresses.

I wonder if the interface between the Galena and the Wood's Metal formed an additional semiconductor junction or if it was purely resistive ?

HD

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Apparently Wood's Metal was used because it secured the Galena without subjecting it to mechanical or thermal stresses.

I wonder if the interface between the Galena and the Wood's Metal formed an additional semiconductor junction or if it was purely resistive ?

HD

As Woods metal is easy to melt it would be ideal for supporting the Galena crystal without damaging it or heating it too much as the metal could be melted (70 degC)in a mould and the crystal partial inserted and then alloyed to cool and set. Easy to do, minimal damage to the crystal at a molecular level which would affect it's electrical properties.

Come to think of it, Woods metal is probably an ideal material for the crystal holder.

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I have several old books from the early radio era. Everymans Wireless Book by F.J. Camm, Foundations of Wireless by M. G. Scroggie. Somewhere I have a Admiralty manual that covers spark transmitters and "Coherers". We made a simple coherer from a glass tube filled with filings from an old silver sixpence and coupled it to a torch bulb and a 4.5 volt battery. Our spark transmitter would have given a "elf & safety" bloke apoplexy. The results were reasonably conclusive but variable.

When me and Stuart were in the 2nd year at school (1968-9) we found a book with spark transmitters and coherer receivers in and talked the science teacher, a bloke called "Moggy Matthews" into letting us build one during our Friday afternoon Creative Activities sessions.

The transmitter had a now banned HT solenoid that sparked a good 3 inches or so. The receiver had a coherer made out of a tube with iron filings in. Both were very simple and had minimal components. Both had matching aeriels made of a tripod gauze suspended from a retort stand and they were set up either at opposite ends of the lab or in different but adjacent labs.

It seemed to work perfectly at first attempt with a good strong signal being received, but when the simple coherer receiver was replaced with a proper portable transistor radio it either didn't work or worked only for a few feet from the transmitter.

Both the transmitter and receiver were powered from the laboratory 12V low voltage supply for electrical experiments and both devices were earthed using its earth connection. A quick look at the meters on the distribution unit for this low voltage syastem showed that each time the transmitter sparked, the voltage dropped and so was fed back to all the supply sockets on its network, all we were getting was a type of feedback transmission through the common power system.

The actual 2 devices we built, when powered independently, didn't work at all.

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The Admiralty book measures capacitance in "Jars" rather than sub divisions of Farads.

"Jars" comes from the original capacitors (previously called condensers) which were "Leyden Jars"

These consisted of an actual glass jar (a jam jar would do) which had a pieces of aluminium foil on the inner and outer surfaces to act as the plates, so I suppose the glass was the dielectric.

The capacitance of a Leyden Jar must have been almost in Farads rather than small subdivisions of it, in fact I wonder if a certain size "jar" was used to define the ridiculously large Farad unit.

At school we used to have a Wimshurst Machine (a device similar to a Van de Graaf generator) for generating large electrostatic charges. Where a VdG generator would store the charge on a large dome, the Wimshurst machine stored its charge in 2 large Leyden jars, - elf & safety no longer allows this, but the Wimshurst gave a much thicker, brighter, longer spark than the VdG ever could, and it was much more frightening to use it, - you wouldn't want to accidentally touch it.

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When me and Stuart were in the 2nd year at school (1968-9) we found a book with spark transmitters and coherer receivers in and talked the science teacher, a bloke called "Moggy Matthews" into letting us build one during our Friday afternoon Creative Activities sessions.

The transmitter had a now banned HT solenoid that sparked a good 3 inches or so. The receiver had a coherer made out of a tube with iron filings in. Both were very simple and had minimal components. Both had matching aeriels made of a tripod gauze suspended from a retort stand and they were set up either at opposite ends of the lab or in different but adjacent labs.

It seemed to work perfectly at first attempt with a good strong signal being received, but when the simple coherer receiver was replaced with a proper portable transistor radio it either didn't work or worked only for a few feet from the transmitter.

Both the transmitter and receiver were powered from the laboratory 12V low voltage supply for electrical experiments and both devices were earthed using its earth connection. A quick look at the meters on the distribution unit for this low voltage syastem showed that each time the transmitter sparked, the voltage dropped and so was fed back to all the supply sockets on its network, all we were getting was a type of feedback transmission through the common power system.

The actual 2 devices we built, when powered independently, didn't work at all.

Our aerials were about 40 feet long and situated in seperate back gardens about 50 yards apart.

It certainly worked but the confirmation depended on one or t'other of us dashing up or down the hill to report success.

We also experimented with voice signalling using earth transmissions.

We used two old valve radios, one of them with the extension speaker terminals connected to two earth rods at the top and bottom of the garden. A microphone was connected to the "pick-up" terminals.

Two earth rods in the other garden were connected to the "pick-up" terminals of a second radio.

Voice could just be heard over a very loud 50 Hz buzzing.

Apparently fair distances can be covered if the transmitting rods are far enough apart and perpendicular to the receiver rods.

This method was used in the trenches during WW1 until it was realised that the enemy was listening in.

HD

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Our aerials were about 40 feet long and situated in seperate back gardens about 50 yards apart.

It certainly worked but the confirmation depended on one or t'other of us dashing up or down the hill to report success.

We also experimented with voice signalling using earth transmissions.

We used two old valve radios, one of them with the extension speaker terminals connected to two earth rods at the top and bottom of the garden. A microphone was connected to the "pick-up" terminals.

Two earth rods in the other garden were connected to the "pick-up" terminals of a second radio.

Voice could just be heard over a very loud 50 Hz buzzing.

Apparently fair distances can be covered if the transmitting rods are far enough apart and perpendicular to the receiver rods.

This method was used in the trenches during WW1 until it was realised that the enemy was listening in.

HD

Once used my old Taylor RF signal generator, (pictured below) connected to a small RF amplifier and my longwire aeriel to send (illegally I suppose :o ), a signal to a friend a few miles away at a predetermined time and on an agreed frequency (one we knew nobody was using for anything else) and he would report back the next day on the results.

The results were very uncertain, and even after a few repeats of this experiment it remained unclear as to what was actually happening. The received signal was very weak, be it 3 miles away or close up to the signal generator / transmitter, noise levels were high but there was some sort of change in pitch when the transmitter was operated. We never did sort out what was actually happeneing.

At the time in 1971, aged 15, we were both keen to get our amateur radio licences, not the ones they have now for VHF / UHF short range conversational stuff (G8 callsigns) but the proper short wave G3 and G4 callsigns using morse code (required a seperate test) to send & receive signals around the world.

Early experiments like this that didn't work did put us off a bit and neither of us ever did become licenced radio hams.

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Once used my old Taylor RF signal generator, (pictured below) connected to a small RF amplifier and my longwire aeriel to send (illegally I suppose :o ), a signal to a friend a few miles away at a predetermined time and on an agreed frequency (one we knew nobody was using for anything else) and he would report back the next day on the results.

The results were very uncertain, and even after a few repeats of this experiment it remained unclear as to what was actually happening. The received signal was very weak, be it 3 miles away or close up to the signal generator / transmitter, noise levels were high but there was some sort of change in pitch when the transmitter was operated. We never did sort out what was actually happeneing.

At the time in 1971, aged 15, we were both keen to get our amateur radio licences, not the ones they have now for VHF / UHF short range conversational stuff (G8 callsigns) but the proper short wave G3 and G4 callsigns using morse code (required a seperate test) to send & receive signals around the world.

Early experiments like this that didn't work did put us off a bit and neither of us ever did become licenced radio hams.

This is getting rather spooky.

Step backwards about ten years before your experiment and I owned the identical Taylor RF Signal Generator. It had the same black crackle case but the control knobs had sharper points.

I had an ex-army WW2 R109 Receiver Set which covered 2 to 12 Mhz.

We installed the Taylor in my pals shed with the usual old radio set to provide a feed to the modulation input.

With the radio tuned to Radio Luxembourg and the signal gennie tuned to 12 Mhz we humped the R109 across town to the home of a lad we knew.

When we got there Radio Luxembourg was coming in on 12 Mhz very loud and very clear.

We raced back home as fast as we could to turn it off before any harm resulted.

Too late !

It seemed that Band 1 reception of BBC television had been replaced over an extensive local area by a broken picture and sound from Radio Luxembourg. It's a good job that many people in the area viewed on BRW cable and were not affected or the hoo-har would have been even greater.

Of course my mate and I were prime suspects and it's a good job that we were able to prove that we were at the other end of town during most of the interference. :)

At that time BBC TV came from Holme Moss on channel 2 with the sound carrier on 48.25 Mhz. The Taylor must have had substantial output on the fourth harmonic of 12 Mhz.

HD

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It seemed that Band 1 reception of BBC television had been replaced over an extensive local area by a broken picture and sound from Radio Luxembourg. It's a good job that many people in the area viewed on BRW cable and were not affected or the hoo-har would have been even greater.

Of course my mate and I were prime suspects and it's a good job that we were able to prove that we were at the other end of town during most of the interference. :)

At that time BBC TV came from Holme Moss on channel 2 with the sound carrier on 48.25 Mhz. The Taylor must have had substantial output on the fourth harmonic of 12 Mhz.

HD

My own aeriel at home went out through the bedroom window and up to the sofit boards from which was suspended a "Sheffield Cable" cable radio & TV. I don't know what company ran it as cable TV was more common in the north of the City and not so much on the Arbourthorne where they had few subscribers anyway. The aeriel was supported at sofit height by being wrapped around this cable TV thing before heading off down the garden to a largeish tree at the bottom.

Note the aeriel running to the tree. Sofit and TV cable off top of picture

The aeriel was in effect inductively coupled to the cable network and could pick up all sorts of rubbish. Rather than me "stealing" a free service from them it was actually a bit of a bind as BBC radio stations and TV sound signals were appearing all over my SW dial along with stations which were just strong bursts of noise that I assume would have been the picture carrier signal. If there was a good shortwave DX signal from half way around the world within a few kHz of one of these harmonic images then you had no chance of hearing it.

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This is getting rather spooky.

Step backwards about ten years before your experiment and I owned the identical Taylor RF Signal Generator. It had the same black crackle case but the control knobs had sharper points.

I had an ex-army WW2 R109 Receiver Set which covered 2 to 12 Mhz.

We installed the Taylor in my pals shed with the usual old radio set to provide a feed to the modulation input.

With the radio tuned to Radio Luxembourg and the signal gennie tuned to 12 Mhz we humped the R109 across town to the home of a lad we knew.

When we got there Radio Luxembourg was coming in on 12 Mhz very loud and very clear.

I wouldn't have chosen 12Mhz, - isn't it part of the 25 metre band?

In our experiments we always chose SW frequencies that were "between the bands" so that we wouldn't be causing trouble for anyone else (or getting caught!), that included broadcast, amateur, shipping and any other bands (like the citizens band which later became the CB radio free for all, which I fully disaproved of and took no part in) which were around at the time. This wasn't as easy as it looked if you considered harmonic emmisions down to the Nth degree.

In our early experiment described previously we chose not to use SW just in case the signal went far and wide. Instead we used disused LW and MW frequencies as they could be picked up on a cheap portable pocket transistor radio, and there wasn't a lot of them that had SW coverage. I seem to remember we used something like 540kHz right at the top of the dial on MW, and also something around 300KHz at the other end of the LW dial.

There were very few, if any at the time, continuous coverage receivers for MW / LW which covered the gap between the two. We assumed this was because most radios, and all commercial ones. were superhetrodyne receivers with an IF of either 465kHz or 470kHz in the middle of this gap.

Now, the Taylor signal generator covered this gap and had these 2 frequencies calibrated on its scale. Of course they were used to tune the cores of the IF transformers when setting up a superhet radio, something I have used it to do. We did consider trying to send out a signal at 465kHz, which, if it bypassed the aeriel and tuning circuits would not be filtered by the receiving radio and get a direct pass through its IF stages. We summised that if we did it every radio would pick us up regardless of what they were actually tuned to as all superhets convert the incoming signal to this frequency anyway. We never did try it.

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