Thermal Expansion Mismatch in Electronic Packaging

Abstract

AbstractThermal expansion mismatch causes serious problems in operating device reliability because of the various stresses imposed on the joint materials undergoing temperature changes. Silicon has a low expansion coefficient so strain buffers are often employed between the silicon and the outer metal covers with relatively high expansion coefficients. These buffers can be metals like molybdenum, ceramics like alumina, or a brush structure of copper, with soft solders at the joints. However, solders themselves have finite fatigue lives which can be estimated from material and dimensional data.