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Weston Bye
08-04-2007, 05:47 PM
In an effort to rid the environment of all traces of lead, modern civlization is now being threatened. Electrical solder joints, now lead-free by law in some parts of the world, are beginning to grow tin "whiskers" that can cause a short circuit if the whisker touches an adjacent conductor. I have been aware of the problem for a few years and have been advising fellow engineers and customers at work to beware. Here is a recent link with details:

http://pubs.acs.org/cen/science/85/8529sci1.html

Perhaps you may want to rethink the extended warranty option.

Carld
08-04-2007, 10:53 PM
Isn't that interesting. I was wondering when a defect would appear. I guess we can add that to the list of negative results of the environmentalists exagerated demands. I guess the lead was outlawed before a tested substitute was found.

Well, it's a boon for the electronics industry now isn't it. Short life spans for electronic gear is good for the ecconomy though so maybe it's not so bad after all. We are a throw away society aren't we.

I can understand removing lead from paint and gasoline and things that expell lead into the atmosphere but lead in many other things will never be a problem.

nheng
08-04-2007, 11:11 PM
Wes1, We do lead free (and ROHS) designs currently, still run a small percentage of leaded so that we don't have to screw around with the lower quality of lead-free joints when working on prototypes.

NASA has a good paper on tin whisker growth but I don't have the link handy. The tin whisker growth seems to be one of the less understood phenomena in today's science. It is very much affected by the composition of the mating surfaces and their finish as well (tin/matte, gold, nickel, etc.). Most of the chip makers have been in full production for most of their product lines.

What's kinda funny about the whiskers is that you can conformally coat an electronic assembly and the tin whiskers can still poke up if conditions are right ... just like trying to control stubborn weed growth with plastic sheeting.

added - my own opinion about lead free is that it is a load of bull cr-p. I'm not going to plunk down several $k for a flat panel TV that has a design life of say ... THREE years :eek: :eek: The lead free nonsense is pure nonsense that is rendered totally unecessary by proper recycling of electronic assemblies, which I believe is already well in progress in Europe (the cradle-to-grave stuff).

Den

Carld
08-04-2007, 11:22 PM
Do you think the industry will come up with a way to clean the boards and solder joints to repair or keep shorts from happening. If not and it becomes common knowledge won't that cut sales. I too hate to think of buying electronic gear and have it fail in a few years. Most the stuff I have now is over 5 years old and I don't want to replace it now after reading this.

darryl
08-05-2007, 12:11 AM
My oh my. I can see it now- a vehicle goes out of control because it's been engineered to be a totally electric/electronic system, including steering- and the computer grew a whisker. Prang! Six people dead. Prang! Another two. Prang! A passenger train suddenly becomes uncontrollable and overspeeds through a corner.
ZZZZSSSSTT! Your doctor's x-ray machine has run amok and given you a major overdose. PPPFFFSSSSTTT! The totally electronic frying pan has just made a major carcinogen of that expensive steak you just bought.

Bolody whiskers.

lazlo
08-05-2007, 12:22 AM
This reminds me of the lead-free bullets the EPA forced down the US Army's throat.

http://www.ausa.org/webpub/DeptArmyMagazine.nsf/byid/CCRN-6CCS3V

http://www.firearmsid.com/Feature%20Articles/GreenBullets/GreenBullets.htm

By the way, with all the controversy over the powdered tungsten "Green Bullets", does anyone know if they're being used in Iraq? The EPA was concerned about lead contamination on US-based firing ranges, so it wasn't clear to me whether they planned to use the tungsten bullets in combat.

If they are being used in Iraq, I'm really curious how well they work -- there was a lot of concern amongst the military that they wouldn't penetrate as well as a copper jacketed lead-core bullet (the Green Bullet is a powdered tungsten/plastic composite).

oldtiffie
08-05-2007, 02:26 AM
Deleted/edited-out

Yow Ling
08-05-2007, 03:25 AM
Odd that.

There was a saying in Australia that was in common use until not so long ago: "It's got ****** whiskers on it" which was applied to anything that was no good for purpose.

Must'a nown sun-th'n eh?

The rather rude response was that "So'ze ya ****** *****" (insert your own words to suit).

I wonder if that's true - must check.

can I buy a vowel?

dicks42000
08-05-2007, 07:00 AM
Funny thing, this isn't a new or recently observed phenomonon....Anyone who has been involved in restoration of old electronics has seen them or heard of them. Have the old tube-type radios etc. really faded that far into the past...? Man I am getting old. As a teenager, I used to play around with old cabinet radios from the 30's, 40's....wax impregnated paper/foil capacitors, heavy wiring & chassis, big transformers, B-batteries, intricate cable systems to drive dial pointers & tuning capacitors, sometimes stylish wooden cabinets or streamlined bakelite. I wish I'd had the sense to save the bakelite "Stromberg-Carlsen" radio we used to listen to at night....A father of a friend of mine used to restore them.

Tin "whiskers" used to grow from soldered electrical connections at tube sockets etc. Note this is exposed "point to point" wiring mostly.

In materials science, much research was done in the late 50's & 60's in Britian using tin crystals as they are easy to grow in solution. This was investigating high-purity materials at high strains...(bending). Imagine having to build a testing machine for this kind of work using manual machine tools. Google "Georgeopoulos Geronomedes" (sp.?) he did it....Gripping & manipulating a crystal was the challenge, I'd be intimidated just by the sheer size problem....as in a world under a magifying glass.

It is amazing the difference in properties between a smooth surfaced single crystal whisker and a comparable size piece of "wire". Many properties we observe on a gross or macro level are related to inter-granular or inter-crystalline "crack-stopping" by alloy ingredients or displacements in the crystal lattice. It's called "pinning". Others are affected by micro cracks that emanate from the surface, say during cooling. Glass fibers exhibit this to a high degree.....

Anyhow that's my nightly diatribe.
Keep well, Rick.

Evan
08-05-2007, 07:12 AM
Have the old tube-type radios etc. really faded that far into the past...?
Not around my place. :D

http://vts.bc.ca/pics/halli.jpg

Still works.

oldtiffie
08-05-2007, 07:19 AM
Deleted/edited-out

Weston Bye
08-05-2007, 09:38 AM
Before anyone asks how this relates to machining I will state the obvious.

We are incorporating more and more electronic devices, from electronic readouts to VFDs on our equipment. Vibration is one of the factors that helps to propagate whiskers. These devices have become more and more complex and miniaturized internally. The pitch between adjacent terminals on integrated circuit packages have become closer, increasing the potential for bridging.

Taking a page from the sky-is-falling news media, imagine a whisker bypassing all the safety and control circuits in your VFD, suddenly driving the spindle from zero to full torque, full speed, while you are adjusting the boring head or changing a cutter. In the past, a mechanical drum switch or contactor removed power from the spindle, but today how many drives are directly connected to the spindle motor?

In the old days, control circuits operated at higher voltages with robust currents involved. Higher current alone was sufficient to burn away a whisker should one chance to bridge a gap.

As nheng pointed out conformal coating is innefective in controlling these things. Where I work, we are doing things like placing hard plastic barriers where possible in places where whisker formation has been suspected or detected, and on simple electronic circuits have been exploring alternatives to soldered circuits.

A.K. Boomer
08-05-2007, 10:05 AM
That is just plain amazing Wes, those pictures are almost as if the boards are alive,,,
I cant believe china is shipping toys over here with lead paint that we know know goes directly into kids mouths yet we have a ban on curcuit boards ----- even though I know its common practice for meth heads to cut up thier stereo components and chew on them I think that thats actually a plus in the long run for average the citizen:cool:

Carld
08-05-2007, 10:09 AM
I have always been afraid of electronicly controled machines and turn them off or use a manual gear box neutral if available. There was a lathe where I last worked that had an electronic speed control on it. It had a habit or starting by it's self and sometimes suddenly speeding up.

Weston Bye
08-05-2007, 12:57 PM
That is just plain amazing Wes, those pictures are almost as if the boards are alive,,,
I cant believe china is shipping toys over here with lead paint that we know know goes directly into kids mouths yet we have a ban on curcuit boards ----- even though I know its common practice for meth heads to cut up thier stereo components and chew on them I think that thats actually a plus in the long run for average the citizen:cool:

It has always been my theory that the children of the poor and ignorant suffered most from lead exposure. We've heard the stories of children eating chips and flakes of lead-based paint, the paint found in older, poorly maintained rental houses, etc. Lead oxide has a vaguely sweet taste (I am told), so attractive to a child, especially one that is hungry. Poor diets may be calcium deficient, and as calcium is insturmental in eliminatinon of lead from the body, the paint-eating child retains the lead and is harmed.

Reasonably affluent or informed families may live in houses of equal lead hazard but survive without harm simply by virtue of a good diet and housecleaning and maintenance. A coat of paint can stabilize the lead even if only temporarily.

As to circuit boards, the hazard is more when discarded into the general waste stream and the waste is incinerated rather than placed in a landfill. There is the fear that lead in the landfill will pollute groundwater, but given the other stuff that goes into landfills, lead is a small issue.

My daughter and son-in-law were contemplating the purchase of an older home that had been fully remodeled - plumbing, electrical, drywall, trim - no lead hazards. They asked me to look at it. I found that the supply line from the water main in the street was lead - common in older parts of a lot of cities. No sale. Some of you may want to check. I relate this to note that for over 100 years this has been common practice and generations of our best and brightest survived and flourished. Replacement is not a bad idea, but not a crisis. Lead in landfills may leach, but very slowly and a lot will get tied up in ground calcium.

I once built and installed a control system that went into a radiator manufacturing plant. They monitored lead fume exposure and provided milk and orange juice - indeed, mandated breaks for milk or juice consumption if the employee's badge indicated overexposure.

When I write operator instructions for areas where leaded solder is used, part of the rules include no eating, drinking or smoking, and wash hands after handling lead-containing materials and before eating or smoking during breaks.
I also encourage a calcium-rich diet.

Don't eat your Blackberry.

rkepler
08-05-2007, 01:25 PM
Not around my place. :D

http://vts.bc.ca/pics/halli.jpg

Still works.


I wondered where my Hallicrafters had got to... Still have the type 80 power tube?

Mike W
08-05-2007, 01:37 PM
Nice picture of the Hallicrafters. I have a couple of Hallicrafters, a couple of R-390's, some Drake rigs, and other stuff I forgot what I have.

Rich Carlstedt
08-05-2007, 10:09 PM
I still use my Grundig-Majestic radio with
Am/Fm/LongWave/3 shortwave bands.
A few years ago I had to find a tube tester ..wow was that a job.
Then I went online and bought a dozen tubes to replace some of the 22 in the radio.
Guess where they all came from ?....Russia..
but they worked.. must still have a lot of tubes there
Rich

J Tiers
08-05-2007, 10:23 PM
Tubes are still made in Russia, and china. They used to be made elsewhere as well, Jugoslavia, for instance, but I think the Serb/Croat thing killed production there.

I believe the article linked states that tin whiskering is not as active by far with lead-containing solder alloys. It may not happen at all.

So old tin-lead solder probably will never grow whiskers.

For sure, it is FAR less likely to crack as the brittle lead-free types do.

Mike W
08-05-2007, 11:51 PM
I have tubes, some new in the box as in more than I care to count.

Evan
08-06-2007, 04:34 AM
Quite a few years ago I replaced the 80 with silicon diodes and also replaced most of the paper capacitors. That radio was my Dad's and I used it as a child to listen to everything I could find. It is still more sensitive than my Yaesu FRG 7700 although the image rejection sucks.

I still have the 80 and a number of other spare tubes.