Reliability of ICA attached sensor components under prolonged humid conditions

Sensor components are used increasingly in various applications. The structure of a sensor component often differs from that of a typical silicon chip used in electronics, which may make their attachment and packaging challenging. Isotropic conductive adhesives (ICA) may be used in many applications which have such restrictions. ICAs consist of polymer binder, into which conductive particles are added. One of the main advantages of ICAs is their low process temperatures. Furthermore, they can be used with many different component structures and materials. In this study sensor components were attached onto flexible PI substrates using ICA flip chip technique. Five ICA materials were tested. Additionally, three different protective materials were studied. One material was underfill and the other two were glob tops. The effect of harsh humidity conditions on the sensor interconnections was studied using a constant humidity test. The test temperature was 85°C and relative humidity 85%. The overall test duration was 10,000h. The resistance values of the ICA materials were found to be very stable during testing. Three of the five ICAs had no failures during testing and two had only one failure. The protective materials were found to be very important for the reliability, as all samples without them failed during testing. The results showed that ICA materials can offer excellent reliability in humid conditions and are interesting interconnection materials for sensor components.