53. Packaging Materials

This chapter is a high-level overview of the materials used in an electronic package including: metals used as conductors in the package; ceramics and glasses used as dielectrics or insulators; and polymers used as insulators and, in a composite form, as conductors. There is a need for new materials to meet the ever-changing requirements for high-speed digital and radio frequency (RF) applications. There are different requirements for digital and RF packages that translate into the need for unique materials for each application. The interconnecting and dielectric (insulating) requirements are presented for each application and the relevant material properties and characteristics are discussed. The fundamental material characteristics of materials are: dielectric constant, dielectric loss, thermal and electric conductivity, resistivity, moisture absorption, glass transition temperature, strength, time-dependent deformation (creep), and fracture toughness. The material characteristics and properties are dependent upon how they are processed to form the electronic package, so the fundamentals of electronic packaging processes are discussed including wirebonding, solder interconnects, flip chip interconnects, underfill for flip chip and overmolding. The relevant material properties are given along with requirements (including environmentally friendly Pb-free packages) that require new materials to be developed to meet future electronics needs for both digital and RF applications.