A new, patented technology that is an offshoot of RIM has been developed by CardXX of Englewood, Colo., to encapsulate electronics into “smart cards.” It is now available for license. Compared with standard polyurethane RIM, the proprietary “reaction assisted molding process,” or RAMP, utilizes somewhat lower pressures and temperatures.
RAMP is being used to securely integrate a radio-frequency identification (RFID) chip and antennae, an integrated circuit, batteries, and other electronic components into a “small-form-factor” smart card. This can be a standard credit-card size or a key fob, smart tag, memory card, or other palm-sized device.
The process was adapted from traditional RIM technology by creating special molds with extremely small but precise cavities—e.g., credit cards are about 0.030 in. thick. Successful production of smart cards requires molds with highly specialized venting and flow characteristics that enable delicate electronics to be securely integrated into the card body.
The RIM equipment being used for this application comes primarily from Graco’s Gusmer/Decker RIM Group. Paul Reed, director of business development at CardXX, praises the equipment’s “unique ability to deliver very small, gram-level quantities of PUR material reliably and accurately.”
How it works
As in manufacturing standard smart cards, RAMP precisely positions computer chips and electronic components within a mold between two sheets of PVC, polycarbonate, or other suitable film. What’s different is that a rigid polyurethane formulation is then injected at low temperature and pressure to completely encapsulate the electronic element between the plastic sheets. Initial cure is less than 30 sec, after which the parts can be demolded. Complete curing takes 30 to 50 min. Several small molds move on a racetrack past mold-closing, filling, and demolding stations.
According to CardXX, the PUR adds flexibility and durability, provides high bonding strength (20 to 30 lb/in.), and has excellent heat resistance with a glass-transition temperature of approximately 250 F. Encapsulation of electronics in PUR reportedly provides superior protection, impact resistance, and shock absorption. According to CardXX, it also provides improved manufacturing efficiency, compared with standard “mill-and-glue” lamination of smart cards.
RAMP utilizes standard high-pressure impingement mixing, but low-pressure dispensing into the mold cavity. Pressures in the mold cavity are approximately 50 to 100 psi, vs. 50 to 200 psi typical for RIM, and PUR is injected at a temperature of 70 to 130 F, in the same range as standard RIM.
Gusmer/Decker’s RimCell Select Series metering and dispensing units are suited to RAMP because they can be customized for the low outputs (e.g., 0.33 lb/min) needed to minimize forces that might disrupt precise placement of electronic components within the smart cards.
At CardXX, a customized RimCell Select High Pressure 20 Unit was coupled with an L-style mixhead. The machine has a dual-switch station, which allows the operator to pour offline for prototyping without interrupting the RAMP production line. The L-style mixhead is a direct-impingement, self-cleaning unit that reportedly reduces pressure spikes and continuously purges the interior passages of any mixed A-side and B-side materials.