Lead-free compatible underfill materials for flip chip applications

This paper focuses on underfill materials for lead-free applications. A series of lead-free compatible underfill materials using capillary flow and mold transfer technologies were evaluated. The evaluations consist of the characterization of their physical properties, assembly of test vehicles with these materials and the reliability stress test of the assembled units. The processing of these materials for assembly was correlated to their physical properties. The reliability issues of the underfill. materials observed at 260°C reflow temperature were highlighted. With the understanding of the materials physical properties and failure mechanisms, the quest for high temperature reflow underfill materials solution begins here.