RIM, RFID meet, signal new markets for a maturing technology

By completely enclosing electronics in small parts made of rugged PUR, OEMs can reduce manufacturing with a one-step process and protect sensitive elements from physical abuse, corrosive chemicals, or weather extremes.

When reaction injection molding (RIM) was developed in the late 1960?s, the low viscosity of its polyurethane (PUR) liquid components?polyol and isocyanate?allowed it to flow over large areas, permitting production of big parts and opening automotive market opportunities, with all-polyurethane bumper fascia driving off on cars soon after.

Now, nearly 40 years later, the low pressure and heat of the RIM process are creating opportunities in much smaller parts, some the size of a quarter, which house sensitive electronic components, including radio frequency identification (RFID) tags.

This latter application, and similar encapsulation of sensitive electronics such as sensors, antennas, and microchips in objects such as key fobs, credit cards, and identification tags, is expanding rapidly with OEMs.

AVX Corp. (Columbus, OH), a global supplier of passive electrical components and connectors, has long been an expert in insert injection molding, partially enclosing sensitive items in plastic, but attempts to encapsulate items such as active RFID tags using injection molding failed, because the coin-cell batteries only withstand temperatures of 60-65°C. Overheating or overcooling the batteries in an injection molding cavity, where temperatures can climb well over 200°C, can hinder their performance. In addition, the high temperatures of injection molding can melt all the soldering of a chip while pressures in excess of 2500 psi when material is injected shear off any remaining features.

Trial and Error

Tom Anderson, AVX product manager, says his company?s forays into RIM and encapsulation go as far back as 1994, with recent advances in process and material, boosted by aid from PUR supplier Bayer MaterialScience (Leverkusen, Germany), pushing RIM-enclosed electronics into the commercial realm and making high-volume components such as the newly emerging RFID segment attainable for AVX?s PolyTect process.

Ten years ago, Anderson admits, AVX?s experiments began somewhere else entirely?namely with small cartridges used in a portable gaming system. Purchasing 10 to 20 games at a time, Anderson and his team would pull off the covers, revealing the chip inside, and mold PUR around it. Next they?d plug them back into the system to see if they still worked.

?It took four or five years of trial and error before we could actually get [PolyTect] to function,? Anderson says. ?There was a long learning curve because [RIM] had never been done over electronics. It was more for car bumpers, bedliners, cowlings?all the normal industrial-type stuff.?

Those industrial applications were made in a process that offered some distinct advantages over competing materials and manufacturing technologies. RIM works by injecting the liquid polyol and isocyanate through two small orifices into a mixhead at pressures ranging from 1500-3000 psi. From there, the liquids are mixed via impingement, and after mixing, the material flows into a mold at roughly atmospheric pressures. For a solid part, filling can take less than a second with demolding possible in 30 seconds to one minute. Wall thicknesses can vary in a single part from .25-1.125 inch, and since the pressures are so low, alternate tooling materials, including aluminum, kirksite, nickel shell, and plastic composites, can be used.

RFID Beckons

Now, as the technology has matured through machinery and material developments, a simultaneous push by huge retailers such as Wal-Mart to use RFID tags to track shipments and inventory has created an opportunity for a manufacturing technology that encloses such sensitive electronics in a rugged material. ?When you really sit back and look at it,? Anderson says, ?we won?t have bar codes 10 years from now. The RFID market is going to be huge, and it?s going to be everywhere.?

But, Anderson adds, AVX isn?t interested in the entire market, just the areas that could use a hardy solution, such as sea containers, pallets, forklifts, and shipping vehicles, where the cost of PolyTect makes sense. ?If I were to sit back and say 10% of this RFID market has applications for this process, I?m probably not too far off,? Anderson says.

Anderson says AVX operates in a temperature range from 100-150°C with pressures around 100 psi or less. This compares to temperatures of 150- 230°C and pressures of 2500-3000 psi for injection molding, and temperatures of 150-175°C and pressures of 1500-2000 psi for epoxy molding. The PUR used allows for a durometer anywhere from 5-90 on a Shore A scale, with flexible or rigid foams, elastomeric to rigid solids, and even fiber-reinforced RIM composites possible, with Anderson admitting ?bulletproof? enclosures aren?t out of the question.

Smarter Smart Cards

A variant of RIM, dubbed RAMP (reaction assisted molded process) by its creator CardXX (Englewood, CO) is now exploiting the benefits of RIM?s low pressures and temperatures to high-tech cards, sandwiching the electronic guts of smart cards, key fobs, electronic passports, multimedia cards, secure digital cards, and other applications between two layers of film with a PUR filling. Using customized dispensing equipment, including metering machines and mixing heads from Gusmer|Decker (Lakewood, NJ), CardXX uses PVC, PET-G, or PC film to serve as the top and bottom of cards as thin as 30 thousandths of an inch, filling the space between the film sheets with PUR at a slow rate, according to a paper CardXX presented at the Polyurethanes 2005 Technical Conference and Trade Fair (Houston, TX; Oct. 17-19).

Although they?ve been slower to catch on in the United States, smart cards, or ones that feature microprocessor chips laminated in, represent a growing marketplace. According to the International Card Manufacturers Assn. (ICMA; Princeton Junction, NJ), the overall global 2004 market was 13.2 billion cards, with units growing by 13% and dollar value increasing 33.2% to $8.2 billion, thanks to microprocessor-chip card growth.

In fact in 2004, traditional cards represented 82.6% of the entire card volume, but only 17.9% of the dollar value, while chip cards grew to 17.9% of the volume and fully 82.1% of the total, global, dollar value.

As retailers and card companies move toward ?pay-with-a-wave? technologies, like JP Morgan Chase with its Blink credit card introduced in May in the United States, where consumers wave their card near a pay station to purchase goods, the push for cards that safely enclose the chip without fear of delamination will increase, creating another new market for RIM.