Performance of electrically conductive adhesive attached sensors in high temperature cycling

This paper studies the high temperature performance and reliability of electrically conductive adhesive (ECA) attached temperature sensors. Testing of the sensors was conducted using a high temperature cycling test with long transition time between the extreme temperatures of -55°C and +180°C. Several different ECA materials were used as attachment materials. Additionally, the effects of the thickness and material of a substrate were studied. Real-time measurements were conducted during testing and these showed that ECA interconnections could withstand harsh high temperature cycling for long periods of time when proper materials and structures were chosen. Significant differences between the ECA materials were seen, thus the selection of the ECA material was found to be very important for the interconnection reliability. Additionally, the thickness and material of the substrate had a marked effect on the reliability. In most cases a flexible substrate yielded a better performance, but the effect differed between the ECA materials. The ECAs studied were mostly anisotropic conductive adhesives (ACAs). However, two isotropically conductive adhesives (ICAs) were also studied, one of them also with an underfill. Although underfill material is commonly used with ICAs, in this study it was observed to impair the reliability. The results showed that analysis of the reliability of all materials and structures is essential when adhesives are used in high temperature applications.