Reliability Evaluation on Flexible RFID Tag Inlay Packaged by Anisotropic Conductive Adhesive

Interconnecting the RFID flip-chip on flexible antenna substrates by anisotropic conductive adhesive (ACA) is a preponderant technique to accomplish the low cost manufacturing of radio frequency identification (RFID) tag inlay. However, for the nature of hot compression bonding by adhesive, the frequency response function of RFID inlays often turns unstable and eventually goes to a response failure. In this work, ACA was prepared by mixing Ag particles into thermoset epoxy resin, and RFID flip chips were assembled on the aluminum antenna by ACA under 180 degC, 12 sec, 1.4 MPa. It was found that the ACA has a comparatively high Tg and the fractograph shows that Ag conductive particles were captured by the gold bumps other than the aluminum antenna. The static tensile test and wind test reveals that the contact resistance of ACA joint rises up with the time or period increasing. Further, the outwards bend wind destructs more than the inwards bend wind on the contact conductivity of ACA due to its heavier tearing fatigue effect. The inlays remained 10 cm response distance after HHT test of 85 degC, 85 %RH, 168 hrs. In a word, the flexible RFID tag inlay assembled by ACA prepared here has an excellent flexibility and high reliability.