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edfas.org ELECTRONIC DEVICE FAILURE ANALYSIS | VOLUME 21 NO. 4 14 ESD CHALLENGES ON RFID DEVICES Peter Jacob EMPA Swiss Federal Laboratories for Materials Science & Technology Electronics & Reliability Center, Dübendorf, Switzerland peter.jacob@empa.ch EDFAAO (2019) 4:14-20 1537-0755/$19.00 ©ASM International ® INTRODUCTION Nearly everyone carries radio frequency identification (RFID) devices in their pockets today. Examples include contactless access cards and key transponders, car keys, laundry identification, and credit or debit cards with contactless payment functions. In principle, these tools simply consist of a microelectronic chip and an antenna. The antenna could be a printed folded dipole, printed coil (usually aluminum), orwound coil (usually copper). If such an RFID setup is located near the reader unit, the reader acts as the primary coil of a transformer, thus supplying the chipwith the requiredenergy.Whenpowered, theRFID sends the collecteddata to an external circuit. Poweredby the antenna reader, dedicated data is sent by the RFID to the antenna. Data is received by the reader unit and sent to a linked computer, which compares the data stored in the RFID to what is stored in the computer. This enables functions such as opening doors, unblocking car immobi- lizers, or scanning parcels. These small devices, many of them integrated in smart cards, are exposed to numerous electrostatic discharge (ESD) risks in manufacturing and field applications. ESD CHALLENGES IN MANUFACTURING In nearly all cases, RFID devices are mounted within chip cards or within other plastic housings, which are made of highly electrostatic active materials (Fig.1). In smart card manufacturing, many layers of plastic foil are unwound from big rolls at high speed and later stacked and baked to the final thickness of the smart card. One of the inner plastic foils in the stack is the one with printed antennas containing aluminum, which will be married with the semiconductor device. The unwinding from the roll and the abrading transport of such plastic tapes is known to charge them to some kV, frequently at the limits of electrostatic voltmeters. Although this charging cannot be avoided, it can be neutralized before contact between chip and antenna occurs in the assembly process. When the antenna coils are printed, both sides of the foil are used in order to connect both ends of the coil to the chip without producing an electric short (Fig. 2). When the foil support within the assembly tool is made of dissipative material, antenna charging is sup- pressed and chip placement onto the antenna foil pads can be donewithout ESD risk. However, some devices are designed for higher frequencies and therefore an open dipole is printed onto the foil instead of a coil—without backside contact. In this case, discharge through a dissi- pative support is not possible. Thismeans that the dipole antenna will experience charging to the electrostatic potential of nearby plastics. If the foil support baseplate is made of a dissipative or conductive material, it will contribute to a perfect foil capacitor with the (grounded) Fig. 1 Various types of RFID packaging, depending on applications. Smart cards (top right and inlay on left side) are among the most common.