Polyhedral oligomeric silsesquioxanes (POSS)-filled underfill with excellent high temperature performance

Advanced underfill material plays an important role in device reliability by distributing the thermal stress and providing environmental protection. Recently there is an increasing demand for low stress underfill which requires low coefficient of thermal expansion (CTE), low modulus and good flowablity. In this report, polyhedral oligomeric silsesquioxanes (POSS) functionalized with epoxy groups are used as potential CTE reducing fillers due to their ability to participant in the polymerization reaction. It was found that the POSS/epoxy composite shows excellent high temperature performance, including the increased Tg, lowered CTE and high storage modulus above Tg, and good thermal stability. Moreover, the effects of the length of organic moieties on the chemical and thermomechanical properties of POSS/epoxy composite were systematically investigated.