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."

Re:What about radiation shielding?

[mrmeval]

Water, boron gas, aluminum, etc you tailor it like Chobham armor in layers and with other tricks. You don't really want lead because of the density it doesn't matter much in space unless you're aiming 60 kilotons of it at DC.

We WILL become more green all this 'waste' is becoming the new gold. Help develop efficient technologies to evacuate landfills of the wealth in them and be the next Bill Grates.

Re:But...but...

[MiKM]

Bismuth isn't radioactive [wikipedia.org]

Re:Toxicity?

[fuzzyfuzzyfungus]

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.

Way Too Late

[svnt]

They may pick up some stragglers that are totally dependent on PZT, but in European consumer electronics, components containing significant PZT have been practically useless since 2006. Europe is not what I would call a small market - as a result, components everywhere are designed to meet the same requirements, meaning these components have suffered from declining demand and/or been removed from company plans.

"Products that use the new compound could hit the market in about five years, according to the university, after large-scale testing takes place, industry awareness and demand happens, and a method for mass production is created."

Given that RoHS [wikipedia.org] has already had a staggering impact on the electronics industry, I don't see "maybe 2013, if people figure out that they want this material, and if we can actually mass-produce it" as too reassuring. I'm sure not designing anything in the hopes that a PZT replacement will hit the market sometime next decade.

Maybe if you're in ultrasonics this is big news?

Re:What about radiation shielding?

[networkBoy]

I was under the impression that a materials ability to block radiation was (more or less) proportional to it's density. Lead being the densest cheap metal making it ideal. while the mass may not be a problem once in space, it sure is a heck of a penalty in lift weight to get it there though.
-nB

Re:But...but...

[the_humeister]

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:What about radiation shielding?

[Cyberax]

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?

[DirtySouthAfrican]

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:$130 / 100g

[Chris Pimlott]

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]

Misleading title...

[jamiek]

FTFA, The researchers have found a replacement for Lead zirconate titanate not LEAD. PZT is a piezoelectric material that contains lead and is used to make actuators and transducers in microelectronics industry. The article itself is pretty poor describing piezoelectric materials as a "switch", so perhaps it is not the fault of the readers for thinking this was a replacement for lead based solders.

No, it replaces lead zirconate titanate

[dtmos]

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:Toxicity?

[fuzzyfuzzyfungus]

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:Lead solder replacement

[servognome]

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.

Re:Lead solder replacement

[servognome]

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.

The problem is many companies think you just change the alloy to lead free, turn the ovens on a little hotter and everything is fine.
When I started work on lead free process development 8 years ago, it became quickly evident that lead free solders require much more than a process "tweak" to the old eutectic systems. Every aspect basically needs to be redeveloped - as you said lead free solder doesn't behave the same.

At the most basic level, instead of 1 tin-lead eutectic alloy, there are a series of different lead-free alloy replacements that you choose from depending on your application and reliability requirements. From there you need new fluxes(to deal with different oxides), equipment (improve accuracy because of less self-alignment and higher temps), and procedures (to make the changes work correctly), all specifically optimized to the alloy and application you are working on.

Lead-free isn't as easy as leaded solders, but if you've done your due diligence in developing the process correctly it really isn't that bad.

Re:What about radiation shielding?

[Cyberax]

You can use pretty much any heavy metal as a target.

Copper is used because it has good thermal conductivity and high melting point - only about 1% of energy is converted into x-rays, most of it is dissipated as heat.

Re:What about radiation shielding?

[default luser]

Absolutely, it is. You can use a higher voltage and a process with larger feature sizes to make your electronics more resistent to a bit flip. The larger feature size and voltage means it takes more energy to flip a particular transistor, at the cost of larger circuits and more power consumed.

You have to add in some buffers to handle the sudden power spikes from particles, so your transistors themselves are safe from damage. Sure, you could still have radiation error events, but they're much less probable with the above setup. MUCH cheaper than lifting enough lead to shield the whole damn circuit board.