Smaller size, faster speed, and lower cost have been the ever-existing demands on microelectronic devices. This trend will continue as portable electronics become more prevalent. One of the most important keys to achieve the goal is application-dependent proper material sets.
The need for new materials for new technologies is obvious; e.g., in RF applications, the package materials strongly affect the performance of the RF electronics and thus the new materials are to be developed to meet new requirements. For the same reason, it is obvious that fundamental functional properties – electrical (dielectric constant, dielectric loss, conductivity, resistivity, etc.) and optical (refractive index, diffusivity, absorption, etc.) must be characterized accurately at the conceptual stage of material development.
Very often, however, it is not obvious that mechanical properties can be more critical than functional properties for successful development of conventional packaging materials. This is an issue associated with tailoring materials properties for specific package architectures. This concept requires clear understanding of mechanical challenges in designing package structures as well as assessing package reliability. The critical properties for considerations include but not limited to: chemical shrinkage, modulus, hygroscopic swelling constant, moisture diffusion constant, glass transition temperature, thermal expansion coefficient, adhesion strength, fracture toughness, etc.