High density fine pitch Pb-free flip-chip interconnect assembly

In this work, the assembly process development of a high density fine pitch multi-chip package with first and second level lead-free interconnects on a build-up substrate printed with polymer thick film (PTF) resistors is presented. Material selection and process parameters are discussed and addressed in this manuscript. Various assembly process and observations during the high density fine pitch flip-chip assembly process are also discussed in the manuscript, including underfill and package reliability issues.