Current loadability of ICA for flip chip applications

Miniaturization is a key issue to achieve advanced performance of electronic devices and to decrease the overall cost of an electronic package. In this respect the flip chip technology provides excellent capabilities to meet the demands of recent and future products. Although solder joining is still the most common technology a great deal of research work has been conducted on conductive adhesives. They are successfully used as die attach, display and hybrid assembly. Progress with its application to flip chip devices has still to be made. Recently, the current carrying capability of isotropic conductive adhesive (ICA) has been a matter of great interest. Predominantly, corresponding characteristics of anisotropic conductive adhesives (ACAs) have been studied by several groups. Though interest, mainly on part of the automotive industry is shown, little is known about ICA's high current behaviour. This paper is part of a broad study focused on the current capabilities of isotropic conductive adhesives. Tests have been carried out on flip chip assemblies. The contact resistivities depending on different DC loads and increased environmental temperatures have been monitored. In-situ measurements have been carried out with an automated measuring system. TGA measurements were made to find out about degradation temperatures of the used materials. The results contribute to the following discussion about the failure mechanisms due to high current loads.