Flex Reliability of RFID Inlays Assembled by Anisotropic Conductive Adhesive

Accompanied by the cost reduction and the assembly line speed increase, the drive to enhance the reliability of RFID tags is ever increasing due to the incremental puzzles on the tag response function. Anisotropic conductive adhesive (ACA) bonding is one of the main stream in a mass production of RFID inlay, but due to its nature of adhesive bonding and contact conduction, the increasing response problems emerges, especially when the ACA joint encounters the occasion that it needs to be flexed. A simple method to evaluate the flex reliability of the RFID inlays is developed in this study. A gold film is sputtered on the RFID flip chip to form a conductive layer, making the inlay strap becomes a conductor, and thus the contact resistance variety of ACA bonding joint can be detected. The ACA assembled inlays using this kind of dummy die are delivered to a serial tests: wind, static tensile and pure bend, while the DC resistance of these inlays is recorded simultaneously. It is found that the pure bend instead of static tensile results in irrecoverable enhancement of contact resistance of ACA joint. Besides, pure bend test with die facing down exhibit a less damage on the resistance than that with die facing up, because the former has a press effect while the latter exert a tear effect on the joint.