Assessment of advanced anisotropic conductive films for flip-chip interconnection based on Z axis conductors

Anisotropic Conductive Films (ACF) for high density Flip Chip Interconnection have been of growing interest during the last few years. One enhancement which has been clearly identified is the concept of a vertical interconnection sheet with structured Z axis conductors instead of particles. The main advantages of Z axis ACF compared to standard ACF are the possibility to get a low temperature process, a lower pitch and pad surface area with a better electrical contact. In this paper, the Z-axis ACF concept and manufacturing basics are reminded. To assess ACF performances, a specific test vehicle has been designed including Kelvin and daisy-chains patterns. We have performed an extensive reliability study by measuring the contact resistance after thermal cycling and humidity exposure. A good behaviour is observed under thermal cycling whereas some improvements are needed in case of humidity exposure. ACF can be useful to connect CdTe or CdZnTe X and gamma ray detectors to readout chips at low temperature. First results of demonstration are disclosed.