Effects of different anisotropically conductive adhesives on the reliability of UHF RFID tags

Radio frequency identification (RFID) system consists of a reader and tags which can be attached to the object to be identified. Such systems are used to identify multiple objects individually and reliably using radio waves without visual connection to the reader. An RFID tag has a simple structure with an antenna to which a chip is attached. Typically anisotropic conductive adhesives (ACAs) are used as attachment materials between the antenna and the chip. ACAs may have a significant impact on the reliability of a tag. In this paper the behaviour of RFID tag interconnections made with four different commercial ACAs was studied. For purposes of comparison the ACAs were characterized using several techniques. The reliability of the interconnections was studied using temperature cycling and constant humidity tests. Clear differences in the failure times between the ACAs were observed. Furthermore, different environments were found to have different effects on the reliability of the ACA interconnections. The results showed that the properties of the ACA should be carefully considered and reliability aspects taken into consideration when ACA for RFID applications is chosen.