Evaluation Of Several Underfill Materials For Chip Scale Package

Underfill technology has been used to minimize the mismatch of the Coefficient of Thermal Expansion (CTE) in flip chip technology. An extension of this application has been used to increase the mechanical strength of Chip Scale Packages (CSPs). As the density for mobile electronic product becomes higher and higher and underfill technology improved, more and more underfill material have been developed. In order to minimize the cost of product and maximize its reliability, evaluate and develop proper underfill material and process becomes necessary. This paper will discuss the impact of non-reworkable and reworkable undefill, and corner-bonding on the mechanical strength of CSPs.It includes 5kinds of non-reworkable underfill, 2kinds of reworkable underfill and one kind of corner bonding underfill. The goal is to understand the reliability and degree of protection each of these underfill material offers. PCBA reliability tests are used to verify the reliability of CSP underfill. It performed include drop, shear, bending and thermal shock tests. This paper also gives lots of data about application, safety and reliability of these undefill gule. It can be used to select available underifll glue.