Viscoelastic characterization of fast curing moulding compounds

Thermoset resins are well known as materials for high performance applications such as in the microelectronics. Examples are moulding compounds, underfill materials, coatings, adhesives, etc. A problem is however that the curing process induces thermal and reaction shrinkage, which leads to residual stresses and warpage. The polymer behavior is highly time, temperature and cure dependent and spans the entire range from liquid to solid state during processing. In order to be able to reduce and to prevent these stresses and warpage, the compound selection and the curing procedure should be optimized within the design process. For this, the polymer material behavior should be understood in advance, which in turn requires adequate modeling and characterization during cure. This paper deals with characterization and analysis of the viscoelastic properties of underfill and molding compounds. The focus is on the determination of the most useful method to find the viscoelastic properties of fast curing materials during the cure process.