3M on Novec and the Future of HFCs

Clearing the air

Whether you live in sunny California or on the rocky coast of Maine, new CARB regulations could have a major impact on your future

From time to time, you may see a chemical manufacturer’s claim that a certain product “meets CARB Standards.” CARB, which stands for California Air Resources Board, is a department within the California Environmental Protection Agency, charged with ensuring healthy air quality in the state.

Established in 1967, before the passage of the Federal Clean Air Act superseded the right of states to set their own air quality standards, CARB is unique in the nation, and has a record of taking proactive and sometimes aggressive actions to improve air quality by steering industry sectors towards the best available technology. Because of this, CARB regulations exert a strong influence on other state and federal agencies, and are often viewed as a bellwether of future national clean air standards.

In recent years, CARB has banned the use of chlorinated solvents, such as methylene chloride, perchloroethylene and trichloroethylene, in aerosol cleaners – including those used in industrial environments. This is being done to reduce the use and emissions of these toxic solvents.

Finding sustainable alternatives to chlorinated solvents

Because CARB rulings are often an indication of the direction that future federal regulations will take, an increasing number of users of industrial aerosol cleaners – including those outside of California – are investigating more sustainable alternatives to products based on chlorinated solvents. The alternatives need to strike the delicate balance of preserving important performance criteria such as non-flammability, material compatibility and cleaning power while at the same time addressing the EHS liabilities of chlorinated solvents.

One such family of alternatives is 3M™ Novec™ Aerosol Cleaners – specialized cleaning products that combine non-flammability and effective performance with a wide margin of workplace safety and a favorable environmental profile – including zero ozone depletion potential and an extremely low climate impact. Most important, these products don’t contain the chlorinated solvents regulated by the Federal NESHAP (National Emissions Standards for Hazardous Air Pollutants) and CARB.

These fast-drying, non-flammable and noncorrosive cleaners are available in four unique formulations, for use in a wide range of maintenance, rework and repair operations. Three of these products – 3M™ Novec™ Electronic Degreaser, Flux Remover and Contact Cleaner Plus – are formulated with 3M™ Novec™ 7200 Engineered Fluid – a solvent uniquely positioned to achieve compliance with California Air Resources Board (CARB) regulations. Novec 7200 fluid is the only nonflammable spray cleaner solvent currently exempt from the CARB definition of a VOCs.

Novec aerosol products also offer “more cleans-per-can,” because they do not resort to increased use of inert propellants (dilution) in order to achieve compliance. In fact, every Novec aerosol product can contains over 95% active solvent – only 5% of the can contents is devoted to the propellant, which is ordinary CO2.

Compare this to many competitive aerosols, which may contain 75% or less active solvent in conjunction with propellants such as tetrafluoroethane (HFC-134a) – a formulating technique these products require in order to be defined as “nonflammable” and/or to achieve VOC limitations.

Whether or not your business is immediately affected by new CARB restrictions on chlorinated solvents, chances are good that similar Federal, regional or state restrictions are on the horizon. That’s why, in order to avoid potential disruptions caused by future regulatory action, many forward-thinking users have already made the switch to sustainable alternatives – like 3M™ Novec™ Aerosol Cleaners.

Hole in one

Unique cleaning properties of 3M™ Novec™ Engineered Fluids help usher in a new generation of sophisticated semiconductor packages

To meet consumer demand for ever more powerful, faster and feature-rich electronic devices, semiconductor manufacturers have adopted a number of innovative techniques to boost chip performance.

One of these techniques involves “stacking” multiple chips, in order to increase speed and reduce power consumption in the same footprint. In order to connect the chips in the stack, tiny holes (called “through-silicon vias,” or TSVs) are etched through the silicon, then filled with a conductive material, such as copper. These metal-filled vias are what connect the chip to the one directly above or below it in the stack.

The most common method for ion-etching TSVs is called the “Bosch Process,” in which plasma formed from SF6 gas is used to etch a hole in the silicon.

The plasma pulse alternates with application of a fluorocarbon gas, which deposits a layer of fluoropolymer material on the sidewall of the via. This fluoropolymer layer stops the plasma from etching through the sidewall (i.e. “passivation”). This etch/passivation cycling of the Bosch process results in a via with slightly scalloped edges.

The fluoropolymer residue left on the via sidewalls from the Bosch process must be thoroughly removed, in order to prevent potential reductions in performance or even failure of the metal interconnect. The problem is, the chemistries typically used in this application (dilute hydrofluoric acid or amines) work by chemically etching and solubilizing the sidewall residue, which can change critical dimensions or generate non-selective material corrosion in the completed device. In another process, N-Methyl-2-pyrrolidone (NMP) is used as a solvent to dissolve the fluoropolymer residue. However, NMP does not produce reliable cleaning results in this application, and there are increasing concerns globally about the toxicity of this compound.

Innovative 3M chemistry helps optimize Bosch process

In recent years, several major manufacturers of 3D semiconductor packages – particularly those being developed for use in MEMs, flash memory and DRAM – have reported excellent results in using 3M™ Novec™ 7100, 7200 and 7300 Engineered Fluids to remove fluoropolymer residue in TSVs.

These Novec fluids selectively dissolve the fluoropolymer residues without acid/alkaline aqueous attack of the patterned wafer. In addition, their very low surface tensions and low viscosity provide more complete wetting
and penetration of TSVs, for more complete contaminant removal. They also are low in toxicity, non ozone-depleting and have relatively low global warming potentials.

A versatile solution for any cleaning method

While Novec engineered fluids can be used in a number of cleaning processes to remove TSV residue, including immersion and spray systems, incorporating them in vapor degreasers offers several particular advantages.

For example, vapor degreasers utilize a boil sump region to remove gross contamination from a wafer by positioning the wafer immediately above the boiling liquid where the solvent vapor condenses on the wafer. The condensed vapor solubilizes the contaminant and the liquid then drips back into the boil sump. The wafer is then rinsed and dried in the rinse sump and vapor zone, respectively. The chemical consumption is limited to evaporative losses which for a typical 20 liter degreaser are 1.5 liters per week. Several users of these kinds of systems report that switching to Novec fluids from other chemistries required no process changes or equipment modifications, beyond replacing seals.

Today, Novec engineered fluids are being commercially used for TSV cleaning in the U.S., Japan and Taiwan. In response to customer demand, 3M will be soon be introducing a UHP (ultra-high purity) grade to complement the existing family of Novec engineered fluid products.

For HFCs, the handwriting is on the wall

As knowledge – and scrutiny – of the climate impact of hydrofluorocarbons (HFCs) grows among environmental activists and regulators, the future of this class of chemicals is becoming more uncertain with each passing year.

Under the Montreal Protocol ratified in 1997, HFCs were listed as acceptable substitutes for ozone-depleting substances such as chlorofluorocarbons (CFCs). At the time, the attention of the Montreal signatories was focused on protecting the ozone layer. Although the global warming potential of HFCs was significant, it was still considerably lower than CFCs, and HFCs were one of the few practical substitute chemistries available at the time.

Today, a number of low global-warming alternatives to HFCs have been commercialized, and more are under development. With this in mind, calls from the environmental community to begin the formal phasedown of HFCs have become more insistent.

One of the most influential voices in that community is the Natural Resources Defense Council (NRDC), founded in 1970 to address a broad range of environmental issues. Staffed by more than 300 lawyers, scientists and policy experts, the organization has helped to write some of America’s fundamental environmental laws.

In May of 2010, the NRDC formally petitioned the U.S. EPA to remove HFC-134a from the list of acceptable ODS alternatives for motor vehicle air conditioning and aerosols and requested the EPA evaluate the feasibility of removing HFC-134a and other high GWP HFCs as acceptable substitutes in other end-use sectors, including fire protection, if alternatives are available.

NRDC requested EPA to act as quickly as possible, based on the feasibility of a number of HFC alternatives named in the petition.1

The concern of NRDC and other environmental experts is that, if the global warming effects of HFCs are not addressed, all the climate gains made in eliminating the ozone-depleting substances that HFCs replaced will be lost. As NRDC staff writer David Doniger puts it, “HFC production and emissions could rise eight-fold by 2050 if nothing is done, with most of the growth occurring in rapidly industrializing developing countries. HFCs would then amount to 9-19 percent of all global heat-trapping emissions in the business-as-usual case, wiping out the climate benefits of having eliminated CFCs and HCFCs and undermining efforts to cut CO2.”2

While most countries in the world agree that HFCs should eventually be replaced by more sustainable alternatives, the question of how and when is a matter of intense debate.

The mechanisms most often mentioned for implementing an international accord on HFCs are the two foremost global environmental treaties: the Montreal and Kyoto Protocols.

The Montreal Protocol, which came into force in 1989, is primarily concerned with matters that impact the Earth’s ozone layer.

Proponents of expanding the Montreal Protocol to include HFCs argue that this treaty was very successful at achieving a global phasedown of the production and consumption of ozonedepleting chemicals, starting with developed countries and followed several years later by developing countries.

Others argue that HFCs should be addressed under the Kyoto Protocol, which is specifically concerned with climate change, binding its signatories to reducing greenhouse gas emissions. Although the Kyoto Protocol came into force in 2005, it was never ratified by the U.S., and does not obligate developing countries to limit greenhouse gas emissions.

The politics and legal arguments of both viewpoints are too complex to go into here; suffice it to say that most producers of HFCs would prefer that regulation of these materials be covered under an agreement which would allow for a more gradual phasedown, rather than selectively removing individual HFCs from the list of acceptable ODS substitutes, as proposed in the NRDC petition to the EPA.

This debate is of particular concern to specifiers of clean agent fire protection systems, who want to be assured that the investment they make today will still be viable 10 to 20 years or more in the future. Although the final chapter of HFCs in fire protection is bound to have many twists and turns, there is little doubt about the ending. Essentially this leaves specifiers with a simple choice: either gamble that HFCs will survive the legislative and environmental initiatives for a few more years, or choose an alternative – such as 3M™ Novec™ 1230 Fire Protection Fluid – whose unmatched environmental profile makes it a safe, sustainable chemical option for the long term.

References
1 Petition to Remove HFC-134a from the List of Acceptable Substitutes
under the Significant New Alternatives Policy Program, NRDC,
May 7, 2010
2 NRDC Staff Blog, Switchboard, Nov. 8, 2009
3M Horizons
N O V E C

Keeping the lid on

Sustainable cover gas alternative helps magnesium industry achieve environmental goals

Magnesium – the stuff of milk of magnesia, mag wheels, lightweight engine blocks and even fireworks sparklers – is an industrial mainstay with a significant drawback. Processing is a challenge because molten magnesium combusts in contact with air and burns at approximately 3,100°C.

For years, an inert cover gas has made magnesium smelting and die-casting possible by forming a thin, non-flammable film on the surface of the molten metal. Unfortunately, the gas, sulfur hexafluoride (SF6), has a drawback, too. It’s recognized as the single most potent greenhouse gas – with a global warming potential 22,800 times greater than baseline CO2.

The U.S. Environmental Protection Agency’s (EPA) voluntary industry partnership program, SF6 Emission Reduction Partnership for the Magnesium Industry, committed to eliminate SF6 emissions by the end of 2010.1 The EPA has reported substantial progress in the goal to eliminate SF6. A key strategy has been the study and implementation of alternative melt protection alternatives.

Future forward technology 3M™ Novec™ 612 Magnesium Protection Fluid is one of the most important of the new alternative technologies. Part of the Novec family of 3M products, it is engineered to replace materials with high global warming potentials, as well as ozone-depleting substances (ODS). Like all Novec products, Novec 612 fluid is designed to be a sustainable technology – thus, expected to be available far into the future.

Other alternative technologies are available but, like SF6, they are not sustainable due to concerns related to toxicity or that the alternative, itself, is also a greenhouse gas and targeted for reduction. For example, HFCs, including HFC-134a, are now the subject of negotiations for a global production phasedown under the Montreal Protocol.

Novec 612 fluid, on the other hand, has an atmospheric lifetime of just 5 days and a GWP of one, which is equivalent to naturally occurring CO2.2, 3,4 U.S. EPA studies show that greenhouse gas emissions from magnesium die casting and ingot casting operations are reduced by over 99% when SF6 is replaced by Novec 612 fluid.5 The table below reports data for a die-casting and an ingot-casting study where SF6 and Novec 612 fluid were run using the same process and equipment.

An outstanding balance of safety and performance

Significantly more reactive at melt temperatures, Novec 612 Magnesium Protection Fluid is more efficiently utilized than SF6, and can be used at very low concentrations.

In addition, both 3M and independent laboratories have determined that Novec 612 fluid has an outstanding safety profile. Studies reveal very low toxicity in both acute and repeated dose testing.

A low-viscosity liquid at room temperature, Novec 612 fluid is easy to transport in conventional liquid containers, and easy to transfer by pumping. It has a high vapor pressure, a low heat of vaporization and is delivered into a carrier gas stream with a gas bubbler apparatus or a precision pumping system.

Finally, Novec 612 fluid has been shown to be compatible with typical materials of construction of furnaces and die casting equipment, including polymeric seals and gaskets in valves and gas mixing meters.

Applications

Typical processes where Novec 612 fluid provides excellent protection include a variety of melting furnaces and casting operations, including:

• Open casting of ingots, direct chill casting, sand casting or investment casting
• High pressure die casting with hot or cold chamber melting furnaces
• Preparation of alloys from pure magnesium or other alloys
• Remelting of scrap from casting processes

1 SF6 Emission Reduction Partnership for the Magnesium Industry, US
Environmental Protection Agency web site, http://www.epa.gov/highgwp/magnesium-sf6/accomplishments.html
2 N. Taniguchi, T.J. Wallington, M.D. Hurley, A.G. Guschin, L.T. Molina, and M.J. Molina, Atmospheric Chemistry of CF3CF2C(O)CF(CF3)2 : Photolysis and Reaction with Cl Atoms, OH Radicals, and Ozone, J Phys Chem A, 2003, 107, 2674-2679.
3 B. D’Anna, S.R. Sellevag, K. Wirtz, and C.J. Nielsen, Photolysis Study of Perfluoro-2-methyl-3-pentanone under Natural Sunlight Conditions, Environ Sci Technol, 2005, 39, 8708-8711.
4 Federal Register 2004, 69 (190), 58907; Report of the Thirteenth Meeting of the Methodology Panel, November 12-16, 2007, page 3 paragraph 9.
5 S.C. Bartos, Characterization of Emissions and Occupational Exposure Associated with Five Melt Protection Technologies for Magnesium Die Casting, and Characterization of Cover Gas and By Product Emissions
from Secondary Magnesium Ingot Casting, available at http://epa.gov/magnesium-sf6/resources.html. Additional information on SF6 replacements is available on this website.

Business gets the green light

Why business sustainability makes dollars and sense

It’s now 23 years since the ratification of the Montreal Protocol, and the debate continues: is “going green” simply an imposed regulatory cost? Is it a compromise between performance and compliance? Is it something that clever marketing can spin into a brand advantage? Is it good PR? The answer, of course, depends on whom you ask. And, that in itself can cloud the real discourse in which businesses should engage.

Regardless of the myriad opinions about the value of green products and processes, the level of environmental concern today represents one fundamental reality: change.

The marketplace evolves continuously, whether the impetus is product safety, performance or ecological responsibility. The real need is for sustainability. That means today’s companies must find solutions that are both cost-effective and are the right choice for the environment.

Most important, it means finding solutions that are forward-looking and long-term.

That’s not to say the only benefit to a policy of environmental stewardship is weathering the current sea change in the market. For instance, voluntary carbon trading is image driven, enabling companies to make claims of carbon neutrality. While such positioning is more common in consumer markets, a green image is proving to have a positive impact throughout the supply chain, especially in high-profile industries such as electronics and automotive. In addition, such industries have created demand for low-environmental impact components and subassemblies, resulting in a direct benefit for companies nimble enough to bring “green” products to the market.

In many industries, however, the motivation for change is compliance. Here, the issues of compromise and trade-offs are felt most keenly, especially when companies remain dependent on regulated processes and products – only to scramble for fixes when phase-outs or bans go into effect. Decisions often are based on short term costs, which ultimately may cost more in the long-term.

That’s why industry experts recommend getting ahead of the compliance curve. Managing for business sustainability is based on a more holistic analysis than “compliance chasing.”

For instance, companies may anticipate that regulatory policies ultimately will put a cost on CO2 emissions. Those companies likely will consider technologies that reduce a carbon footprint to be a sound investment, even at a marginally higher cost. Right now, there are many businesses and organizations investing in waste heat recovery, solar, wind, sustainable fire protection, and similar technologies because they expect CO2 emissions to have real costs in the future.

As noted, the marketplace will continue to evolve – compelled by regulations, influenced by societal pressures, and motivated by the changing values within companies and industries themselves. Just five to ten years ago, the value propositions of sustainable technologies were difficult to sell and purchase decisions were more frequently based on shorter-term costs. Today, new technologies that impact a business’ carbon footprint or, perhaps, reduce energy use are perceived as having the higher value because they perform, are cost effective, and they are green.

Adapted from August 2010 ECN, August Roundtable: Why Adopt “Green “Technology? http://www.ecnmag.com/articles/2010/07/roundtable/green-tech.aspx

Social Science

New online forum seeks to facilitate cooling technology dialog

As reported in a previous issue of Novec Horizons, 3M is developing a simple, passive, 2-phase (evaporative) cooling technique for removing waste heat generated by large electronic data centers. This new technique, which involves immersing servers in a bath of a non-electrically conductive fluid, such as 3M™ Novec™ 649 Engineered Fluid, is based on decades of 3M experience in using immersion cooling for high-value electronics, such as supercomputers, transformers and traction inverters.

In the past, practical application and widespread adoption of unconventional techniques such as passive 2-phase immersion cooling might take years, because of the difficulty in reaching and engaging widely dispersed technical audiences. These audiences – who are understandably reluctant to risk their operations to unproven ideas – must be part of the development process, in order to move a new technology from the lab to the marketplace.

Today’s new social networking tools, such as Facebook, Twitter and YouTube, have made collaboration between technology developers and end users much faster, simpler and more efficient than ever before. That’s why 3M will soon introduce a new Facebook site, whose purpose is to create an ongoing dialog about passive 2-phase immersion cooling between its developers and the data center professionals who might benefit from it.

According to Erin Binder, 3M is unique among its competitors in this industry because of the level of heat transfer expertise possessed by its technical staff. “The people in our labs are not only doing chemical benchwork,” she declares.

“They also have the kind of hands-on, practical experience that can make our products work efficiently and reliably in a customer’s particular application.” Binder explains that 3M heat transfer specialists will use the new Facebook site to post progress reports of their development work – giving readers a “behind-the-curtain”
look at the evolution of this new cooling technology. “Readers will have the opportunity to post questions and comments on these reports, which we believe will help us identify and address issues that we might otherwise miss,” says Binder. “Essentially, users will be able play an active role in optimizing this technology for the marketplace.” In addition to its role as a reader forum, the site will also be used to post technical papers, research results, lab videos and more. The new site is up and running, so log on today to learn more about this unique Novec application.

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