Researchers Getting the Lead Out of Electronics

alphadogg writes "Researchers at the University of Maryland say they have discovered a material to replace lead, a potential environmental hazard, in electronics products. The material, bismuth samarium ferrite (BSFO), was found by researchers in the university's A. James Clark School of Engineering. It can be used in products such as biomedical imaging devices and inkjet printers, and if implemented commercially could keep lead out of landfills and the ecosystem, they say. While manufacturers have developed replacements for lead in many products, until now no commercial replacement existed for lead zirconate titanate (PZT) — the material of choice for transducers, actuators, sensors and microelectromechanical systems used in common electronic devices, the university says."

What about radiation shielding?

Could this new metal shield against cosmic rays as well as lead? I'm reminded of the scene in Kim Stanley Robinson's Red Mars [amazon.com] where the inhabitants of a spacecraft have to hold out against an incoming solar flare and find their shielding woefully insufficient. A material that could block rays yet be lightweight and less toxic would no doubt be a boon to the space industry.

Re:What about radiation shielding?

Lead is NOT a good shield against cosmic rays. Fast charged particles cause a strong bremsstrahlung (braking radiation) in lead. That's also how X-Rays machines work - fast electrons are slammed into targets made of lead or tungsten.

High-density polyethylene, water or paraffin work much better for cosmic rays shielding.

Now, lead is great against gamma-rays. But they are not the principal danger of cosmic rays.

Re:What about radiation shielding?

So we can't throw 60 tons of lead at DC because the DC politicians are even more dense?

Sorry offtopic, but we are talking about dense things.

Re:What about radiation shielding?

It's all about cross section, which roughly depends on the incoming particle's energy being close to the energy of a bound state in the atoms of the material that is to absorb the radiation. The density contributes an overall factor to the calculation. Also, led is nasty when charged particles are involved (electrons, probably protons), because they will rapidly decelerate and create brehmstrahlung, so you've traded a charged particle which is easy to deflect with an X ray, which is not easy to reflect. My wife uses plexiglass shields in her lab for this reason, because it gracefully absorbs beta radiation.

Re:What about radiation shielding?

Actually, extra mass is a problem even once it is in space. Manoeuvring all that extra mass requires greater amounts of energy, which is often somewhat in short supply.

Re:What about radiation shielding?

Hey, no fair actually knowing how physics work! Here we are, all sci-FI about things, and you barge in with just sci... you must think you're sooooooo much better than the rest of us don't you?

Good day sir, I say good day.

Toxicity?

So... have they actually tested this on humans to verify it's non-toxic? That's great that we're not using lead, but if this is just as bad for humans when it hits our water supply, what exactly is the benefit? Swapping one (cheap) poison for another (expensive) one?

Re:Toxicity?

Toxicology can be full of (un)pleasant surprises; but the list of elements involved is promising. Bismuth is a widely accepted nontoxic substitute for lead in applications where similar mechanical properties are needed, and is a component of certain medicines. Iron is generally unproblematic. I'm not sure about Samarium, though our wikipedia overlords say "low to moderate toxicity". Since one of its isotopes has internal medical applications, there are probably some toxicological data out there.

We'll need to test the compound itself, to be sure; but it probably beats lead.

Re:Toxicity?

Inferring a compound's behavior from the individual elements is error-prone. Carbon is great and nitrogen is great, but CN, well, not so much. On the other hand, this is more true with organic compounds (containing carbon).

Re:Toxicity?

Certainly true, particularly with clever organic stuff. On the plus side, it can at least give you an idea of whether the compound can be rendered safe by incineration, decay, or being metabolized by the right organisms. Particularly with the interest in incineration or plasma pyrolysis for waste disposal, I'd consider a toxic compound made of harmless elements to be a win over a toxic compound made of toxic elements(and, in some circumstances, even a harmless compound made of toxic elements). In the end, we'll just have to feed a bunch of this stuff to bunnies and fuzzy puppies, I suppose.

Re:Toxicity?

Pepto-Bismol is Bismuth salicylate if I remember correctly.

Re:Toxicity?

As long as the product performs somewhere near as well as the old stuff, and it's patentable, then there is money to be made. We just have to find sufficient fault with the old stuff, and bad mouth it enough to start making money. Wikipedia says that as with the other lanthanides, samarium compounds are of low to moderate toxicity, although their toxicity has not been investigated in detail. An MSDS sheet where you can put toxicity N/A, no data available sounds better than one where you know it's toxic, because at least with an unknown there is a chance that it's not toxic. There is money to be made with the patent, and money saved by not having regulations to deal with. Regulations regulate know toxic materials, not unknowns.

Reality check...

Lead: Found in damn near every kind of mining ore. Very common.
Bismuth: 2x more abundant than gold. Not considered economical to mine for it; Usually had as a byproduct.

So sure, if you want your production costs to go up up and away, killing your competitive edge, use the eco-friendly BiFeO3. Everyone else, keep pushing recycling and consumer awareness. -_- Oh -- and the icing on the cake? Guess who produces most of the world's bismuth? China, the country best known for producing lead-laden products of much doom.

Re:Reality check...

If your toddler is licking mining ore I think your first court date will be with child protection services, not the manufacturer.

More reliable than tin?

While it's good that they're getting lead out of toys, etc. what about computers, televisions, and other devices/appliances which are generally not regarded as disposable? Is this new solder going to be more reliable than tin, which is notorious for whisker and dendrite formation, which wreaks havoc with reliability?

Given that you're on /. I'd assume that you know what tin whiskers and dendrites are, but in case you're not here is a refresher:

http://www.siliconfareast.com/whiskers.htm [siliconfareast.com]

You can see where this is a problem. And, although it's been discovered that matte tin surfaces and good quality control can reduce the likelihood of whisker formation, what about repairs and installation/reinstallation of components on a mainboard? Replacing integral components (capacitors, sockets, etc.) require high heat, which is sufficient to change the crystalline structure and introduce new stress points for whiskers to "grow," and flexing of the main board from installation of peripherals, connecting devices to sockets, and simple heat/cold cycling will be enough to introduce stress points even in properly-formed, properly-plated components, creating points where whisker formation is more likely.

Yes, protect the environment, but since more and more electronics are being recycled rather than being dumped in landfills, isn't lead in electronics a non-issue anyhow? I mean, in most localities you're not supposed to chuck monitors and devices containing printed circuit boards in the trash.

$130 / 100g

A quick search came up with one site listing the cost of Samarium as $130 per 100g. I'm sure that's cost effective for medical imaging equipment. And I had never realized this, but our local landfill is positively brimming with discarded medical scanning equipment. I might try to scavenge some of this, but all the discarded MRI machines are clumped together by some unseen force.

Re:$130 / 100g

And I had never realized this, but our local landfill is positively brimming with discarded medical scanning equipment. I might try to scavenge some of this, but all the discarded MRI machines are clumped together by some unseen force.

Might want to reconsider that. [wikipedia.org]

Why?

I've never seen a justification for the huge amount of money that's been spent on removing lead from electronics. Yes, the stuff can be toxic if ingested in sufficient quantities. No, it isn't going to leap out of your old TV set and perform unnatural acts on your dog. Tin-lead solder has been used for many decades. It's cheap and it works. I can understand why lead was removed from paint and gasoline. It was creating real problems when used in those products. Why, other than catering to the irrational and unfounded fears of the public, are we removing it from electronics?

Re:Why?

Why, other than catering to the irrational and unfounded fears of the public, are we removing it from electronics?

Isn't that pretty much a politicians' job description these days?

The environmental lobbies have already pushed through enough regulations to put many U.S. industries out of business and left consumers with no choice but to purchase much more shoddy products manufactured with far less environmental controls from foreign sources. But, I guess that's okay. It's over there, right? It's not like pollution in a foreign country affects us.

Oh, wait..

Vacuum tubes come to mind as a good example. I currently design, build, and service vacuum tube musical instrument amplifiers. The tubes being made in China, Russia, and other countries in eastern Europe are crappy-sounding, unreliable, and vary wildly in specs from production-run to production-run, and even within a single run. It's so bad that old-production tubes that have sat in some dusty warehouse for 2 or 3 decades or more sell for unbelievably-high prices.

USD$400 for a pair of RCA 6L6's!?!? That's *if* you can find them somewhere?

http://www.kcanostubes.com/products/106/NOS-RCA-6L6GC-Blackplate-Matched-Pairs.htm [kcanostubes.com]

That's just nuts! The *whole amplifier* these things came in didn't cost that much new at the time!

I'm also going to keep on using regular 60/40 rosin-core solder in my builds and repairs until and unless they develop a true replacement that doesn't have the 'tin whisker' and other problems associated with current RoHS-compliant solders. If they outlaw it, I guess I'll be an outlaw.

I can see a future jailhouse conversation:

"What did they get ya for man?"

"Possession and distribution."

"Meth? Crack? Heroin?"

"Nah, 60/40 solder."

"Stay away from me, man!"

Cheers!

Strat

No, it replaces lead zirconate titanate

The researchers haven't come up with "a material to replace lead." They've come up with a material to replace lead zirconate titanate, a.k.a. PZT, a piezoelectric and ferroelectric material with many uses in electronics. Because it has an extremely large piezoelectric constant (meaning that it produces a large voltage under little mechanical stress) and is cheap to produce, it is the ceramic frequently used in transducers, sensors, and resonators. The thing on your motherboard that beeps on boot is very likely made of PZT.

PZT is not, repeat not, used in solder. Wikipedia [wikipedia.org] is one of your many friends.

Finding a ceramic with similar properties, but without the lead, has been a difficult problem for materials scientists, and the UM researchers say they have finally come up with a viable candidate.

Re:But...but...

Bismuth isn't radioactive [wikipedia.org]

Re:But...but...

From the same wikipedia article that was linked to (it's even in the first paragragh!):

It is generally considered to be the last naturally occurring stable, non-radioactive element on the periodic table, although it is actually slightly radioactive, with an extremely long half-life.

Re:Lead solder replacement

As a technician, RoHS is the bane of my existence. It doesn't flow right, it doesn't wet right, and it doesn't cool right.

Because RoHS solder is not a true eutectic alloy it tends to separate when thermal conditions aren't precisely right. As a consequence, many manufacturers had huge runs of products that stayed soldered just long enough to get out the door and frequently out of warranty.

I hope someone comes up with a better substitute soon because I am sick and tired of cracked solder, cracked solder, and cracked solder.

Re:Lead solder replacement

You've got to love an environmental measure that ensures a significantly higher failure rate in electronic devices, meaning more electronics to trash -- electronics containing materials much more hazardous than lead. Sheer genius.

People in first world countries have so little to worry about in terms of health issues that they strain to find bogeymen, and lead has become one of the things filling that role.

I had one couple fly up from Texas just to see my house in Seattle, make an offer on it, and later rescind the offer because the house was old enough that it existed when lead paint was sometimes used. There was no specific reason to believe the paint was lead-based, and much of the house was wall-papered. The mom was terrified of the possibility of lead and her email withdrawing the offer was filled with heartbreak because they really adored the place; they ended up getting a recent townhome in a much less desirable location. One twist: they knew from the beginning that the attic had loose-fill vermiculite that had a decent chance of containing asbestos, and they had no problems with that.

Re:Lead solder replacement

I haven't picked up a soldering iron in a while, but I've heard that non-lead solder has a lot more structural problems than lead solder. Will this stuff have related problems?

As an engineer working on lead-free solder development for electronics, the problems that can arise are specific to the application. The industry has developed a number of different alloys that perform under specific conditions. Instead of just choosing a tin-lead solder that works pretty much everywhere, developers need to understand the types of reliability stresses their product will see and choose the best alloy to meet those requirements. For example lead-free solders that work well in a thermal cycling environment tend to not perform as well under shock conditions. From an assembly side of things, a lot of the problems arise from using old SnPb equipment and materials for soldering joints using leadfree solders. Different reflow temperatures, wetting characteristics, and oxides, means that you just can't use the same old eutectic flux and soldering iron and expect the same quality of results.

Lead-free solders aren't necessarily problematic, they just require a little more understanding to properly use.