Lead free solder - exposed in a UK national newspaper

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Within a whisker of failure

Removing lead from solder may seem a smart idea environmentally, but the resulting microscopic growths called tin whiskers could be just as problematic

  • Kurt Jacobsen * The Guardian, * Thursday April 3 2008 * Article history

This article appeared in the Guardian on Thursday April 03 2008 on p1 of the Technology news & features section. It was last updated at 00:05 on April 03

2008. Tin whiskers

On April 17 2005, the Millstone nuclear generating plant in Connecticut shut down when a circuit board monitoring a steam pressure line short-circuited. In 2006, a huge batch of Swatch watches, made by the eponymous Swiss company, were recalled at an estimated cost of $1bn (£500m). In both cases, "tin whiskers" - microscopic growths of the metal from soldering points on a circuit board - were blamed for causing the problems.

It's not the first time these mysterious growths have been blamed for electronics failures. In 1998 the Galaxy IV communications satellite sputtered out after just five years; engineers diagnosed its failure as due to "whiskers".

The US military blamed them for malfunctioning F-15 radar systems and misguided Phoenix and Patriot missiles. In 1986, the US Food and Drug Administration recalled a number of pacemakers because of these same whiskers. In fact, they've been known about since the 1940s, and happen with cadmium and zinc, too: during the second world war, similar whiskers would short the cadmium tuning capacitors in aircraft radios. A decade later, tin-based relays in AT&T telephone switching centres were found to cause shorts.

The solution to "whiskering"? Mix lead into the solder, as was done from the

1950s. Colin Hughes, a physicist who worked on the first British nuclear bomb, told me that the whiskering problem never came up during his career.

But now the lead is gone, by legal mandate, and whiskers are back - causing potential problems for us all.

Since 2006, lead has been banned from solder in the European Union under the

2003 Reduction of Hazardous Substance (RoHS) directive, which gave manufacturers three years to phase out lead.

The logic seemed reasonable. Removing lead from petrol (where it was used to prevent engine mistiming) brought clear environmental and health benefits, taking a harmful chemical that can affect intelligence out of the atmosphere. Removing lead from solder, the 37% lead, 63% tin alloy used to join metal objects in everything from plumbing to circuit boards, was an obvious next step to prevent it leaching into ground water from dumped items in landfills.

Meanwhile, the US and Japan have also been moving to lead-free solders. It's a huge shift; the US Environmental Protection Agency (EPA) estimates that

80m kilograms of lead solder was used worldwide in 2002. Environmental groups have applauded the move. "In the US we've been surviving without lead solder for many years," says Rick Hind, legislative director of Greenpeace's toxics campaign. "With less exposure to lead we will all benefit by being smarter and making safer and more durable products." (The US has not made lead-free solder obligatory, but does offer tax benefits for doing so.)

But without lead to tame it, tin behaves oddly on circuit boards. Left alone, tin plating, like cadmium and zinc, spontaneously generates microscopic shreds of metal - about one to five microns in diameter, or less than one-tenth as wide as a human hair - which push up from the base. If they grow far enough to touch another current-carrying location, they'll cause a short that can wreck the equipment while leaving barely any trace.

The cause is becoming clearer. "I believe the mechanism of whisker formation is now understood: it is due to compressive stress - caused by, say, diffusion of copper into the tin - being built up in the tin layer which breaks through the tin oxide barrier layer [to the air]," says Steve Jones of Circatex, in South Shields. Critics cite reports that solder substitutes - pure tin, tin-zinc, tin-silver-copper - simply cannot match the lead mixture for reliability, coverage ("wetting" terminals), and cost (silver is especially pricey). Therefore, the US military, Nasa and medical and high-level research equipment are exempt from what authorities view as untrustworthy commercial components.

"I still use lead-tin solder - it works better," says John Ketterson, a solid state physicist at Northwestern University in Illinois. He notes the tradeoffs of "cost, materials, strength of the solder and all that" during this mandated changeover, and that manufacturers "have to get an experience base" with new processes.

{ snipped as lengthy }

Tin whiskers: coming to a PC near you?

· They can grow at ambient temperature and humidity, or in vacuum · They can grow in steady or varying temperatures (though the latter may encourage growth) · Whiskers' tips are atom-sharp. They will push through any coating, given time · They are a prevalent cause, only now being identified, of many past equipment failures · One whisker can carry about 30mA - more than enough to cause havoc in digital circuits · Silver-tin-copper ("SAC") solder slows but doesn't stop whisker growth · SAC solder has more environmental impact than the lead-tin version · Older 37%-63% lead-tin solder mix merely deforms, reducing stress and hence minimising whiskering · Whiskers can grow indefinitely

Source: Howard Johnson, Signal Consulting

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

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Reply to
N_Cook
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Isn't it funny how figures can be 'distorted' to make facts suit the context. By saying "80m kilos", the EPA make it sound like a HUGE amount, but put that into a more 'recognisable' form, and it becomes 80 thousand tonnes, which is not nearly so contentious. Then further, take that only 37% of that was actually lead, and you are down to 29.6 thousand tonnes. Now compare that to the world's lead-acid battery usage, where recycling of the end-of-life product to recover the lead, has been sucessfully in place for years. At 30th tonnes, the potential environmental impact of the lead in solder, even if you *did* dump it all in the ground, is minuscule.

As I've said before, I'm glad that the avionics industry refuse to use the stuff. The day they do is the day I stop flying ...

Arfa

Reply to
Arfa Daily

About time too.

Never mind the reduced reliability (see the ERA study) caused by lead-free solder when equipment is exposed to vibration.

Graham

Reply to
Eeyore

Its good for the way economy works nowadays. Buy, buy, buy the crap that dies or obsoletes every 2-3 years.

Mark

Reply to
TheM

Before I waste time downloading an irrelevant pdf

would this be what you be referring to :

Review of Directive 2002/95/EC (RoHS) Categories 8 and 9 - Final

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Results of vibration testing lead-free solder from different researchers ...

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

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Reply to
N_Cook

And, where do these pin-heads think the lead came from, in the first place?

Jonesy

Reply to
Allodoxaphobia

Not sure if that's the one I had to be honest but looks interesting.

Graham

Reply to
Eeyore

It came from deep within the ground, in the form of lead ore, which I think is much less of a health hazard than metallic lead decomposing in a landfill and seeping into the water supply.

In Europe, there are places where the Romans smelted lead 2000 years ago, and 8" or so below the topsoil, the dirt is still so toxic that health officials (in Britain at least) don't allow people to dig there, even wearing protective gear.

BTW, I'm not a pinhead, just someone who cares about my health, that of others and a quality environment for us to all live in.

I tried lead-free solder, and gave up on it, at least for prototyping. I was feeling a little bad about returning to traditional solder, until the OP posted the article. Thanks - I feel vindicated. I hope that someday there is a better alternative to lead-based solder, but evidently it hasn't happened yet.

Jay Ts

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To contact me, use this web page:
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Reply to
Jay Ts

As I've said before... It isn't a matter of whether electronic equipment has lead in it, but what happens to that equipment when it's disposed of. It's the latter that should be considered.

Reply to
William Sommerwerck

And lead isn't the only toxic substance used in electronic equipment and the process used to manufacture it.

Is a lead-free item that fails and ends up in the landfill after 2 years better than a lead-containing device that lasts a decade?

Reply to
James Sweet

Welcome to California.

I've used 'alternative' solder. I could live with it if need be. It handles differently but geez, I think the fumes would kill me faster than eating a pound of lead solder everyday at tea. I've never heard the proponents addressing the wicked fumes of the 'better' solder.

-Bill (63/37)

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Reply to
exray

On Apr 3, 6:00=A0pm, exray wrote: > Jay Ts wrote: > I've used 'alternative' solder. =A0I could live with it if need be. =A0It > handles differently but geez, I think the fumes would kill me faster > than eating a pound of lead solder everyday at tea. =A0I've never heard > the proponents addressing the wicked fumes of the 'better' solder. >

You mean the fumes from the flux. You don't believe you're breathing solder vapors, do you? In the 40+ years I've been using solder, I doubt I've used 5 lbs and I do quite a bit of soldering.

GG

Reply to
stratus46

AIUI, lead in metallic form is pretty stable and doesn't 'leach' into groundwater the way some would have us believe.

Graham

Reply to
Eeyore

I've never turned on my shop spectrometer to determine if it was the flux or solder. I just know that the new stuff doesn't smell as friendly to my human nose.

40+ years, 5 pounds, yadda,yadda...how much 'new' solder have you used? I suspect you're just trying to pick a fight. I'm not playing. See ya.

-ex

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Reply to
exray

There's the other end of the process too: mining, smelting, and the rest of the manufacturing process that might be producing pollution. All that is outside my realm of knowledge. Maybe they do it in an "environmentally-friendly" manner these days? I really have no idea.

I think ideally, we'd find something better to use, but although it's gotten a lot of bad press, there are much worse things than lead. Such as other heavy metals, notably cadmium and mercury.

Another source of lead is CRTs, many of which are still in use. They contain about 5 pounds of lead each for radiation protection, quite a bit more than is contained in the solder in the PC boards.

And the replacements, flat screen monitors, have mercury in the fluorescent backlights.

I've had trouble with mercury poisoning in the past, but even though I'd been exposed to a lot of lead as a child, I've never discerned any problem from it. (It's tricky though, low- to moderate-level heavy metal poisoning can easily go unnoticed, while causing significant health problems.)

This does not mean that solder-containing lead is "good", just that it's appropriate to keep things in perspective.

Jay Ts

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To contact me, use this web page:
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Reply to
Jay Ts

"Jay Tossers"

** Silly comparison.

Glass does not break down in the environment.

So how would any of that lead get out ??

...... Phil

Reply to
Phil Allison

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lead-free

...

One small bit from that study

"Solder joint failure due to vibration becomes more significant as the frequency of vibration approaches the resonant frequency of the component or structure. Studies by Chuang et al 29 and Song et al 30 have sought to identify microstructural features that influence the performance of conventional Sn-Pb solders and candidate replacement lead-fre solders. The typical microstructure of conventional Sn-Pb solders containing coarse pro-eutectic grains reduces the ability of these materials to absorb energy during crack formation and hence reduces the vibration resistance of joints made using these solders. "

I thoutht distributed irregularities in structures, suppressed crack propogation. Would seem NOT to be borne out for the case for premature failures of solder joints for unsupported dropper resistors in mucic combos - ie amplifiers contained within the same case as large speaker/s. Failure in 2 or 3 years of routine use wheras more like 20 years for failure in similar but older PbSn manufacture.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

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Reply to
N_Cook

Basically, there isn't a lead-free alternative that works the same, or even close, but you're missing the point(s). Firstly, there isn't *quite* such a huge amount or disposal problem as they would have you believe. Second, the lead in solder is pretty firmly 'locked into' the alloy, such that it doesn't readily come out of the solder into water. Yes, I know that acid rain can have some effect on that equation, but that's nothing like as bad as it once was. Finally, all electronic equipment in Europe at least, is now subject to the WEEE directive, which dictates the way it is treated at end of life, covering recycling and disposal of the remains that can't be recycled. There is no reason at all that leaded solder could not be recovered and recycled, in the same way as lead free solder. 80% of the world's metallic lead production goes to automotive battery manufacture. Lead recovery and reuse from that product at end of life, has been mandated and successfully carried out, for years.

I think that this is the reason that most people who have to use lead-free, get so wound up about it. As far as I am concerned, the legislation that mandates its use, is ill-considered, not thought through, unnnecessary in the light of the legitimate WEEE directive, and effectively replaces a mature and reliable technology, with one that has the potential to be directly dangerous to human life, if it ever finds its way into avionics, medical, and military applications, which so far, have managed to secure exemptions.

Like any sensible person, I don't want to deliberately pollute the planet for those who come after me, but in recent years, many badly informed decicisions on this sort of thing, have been made by departments 'jumping on the banwagon' to justify their own existence. The whole thing isn't helped by celebrities and ex famous politicians serving their own public eye needs through 'green' issues. It has actually reached the point where I am now sick to death of hearing the words "green" and "eco" and "carbon footprint" and "geenhouse gas" and "cimate change" and "global warming" every single time I turn on the radio or TV. So here's a new word.

Ecobollocks. Covers what a lot of this bull actually is ...

Arfa

Reply to
Arfa Daily

I don't think that he's trying to pick a fight at all ... Depending on whether or not he's talking 'professional' use, that might be a bit of an underestimate, but not huge. I hand solder just about every day of my working life. I use predominantly 0.7mm solder wire, which I buy in 500g reels. I reckon that each reel lasts me probably 3 years, so in 35 years of professional use, I have used perhaps 6kg or 13 pounds.

The reason that lead-free solder does not smell as nice, is that it is no longer a basic natural rosin flux that is contained within the solder. Because of the new stuff's vastly inferior wetting qualities with most metals used in electronics, it has to contain a far more aggressive flux to stand any chance of forming a metallic bond. That aggressive-ness is achieved by making the flux slightly acidic, so the fumes, if you are breathing them, are actually gently rotting the linings of your nose and lungs. There was always a declared H & S issue about industrial asthma with rosin flux fumes in quantity, but I suspect that this stuff is potentially a far greater health hazard than rosin fumes ever were. So, if you're having to use a lot of lead-free in your day to day work, I would suggest that now is the time to install some fume management, even if it is just an old computer fan blowing the smoke across to someone else ... :-)

Arfa

Reply to
Arfa Daily

And is then properly recycled ?

Arfa

Reply to
Arfa Daily

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