Mechanical properties of glass frit bonded micro packages

Abstract

Frit glass bonding is a widely used technology for encapsulation of surface micro-machined structures like inertial sensors or gyroscopes on wafer level. Since for sensors in automotive applications, a lifetime of 15–20 years has to be guaranteed for, a reliable lifetime prediction is necessary. Different material parameters have to be known for a lifetime estimation based on stress corrosion cracking, which determines the long-term strength behaviour of most bonded interfaces of microsystems. Parameters needed for lifetime prediction have to describe the material’s resistance against crack propagation (fracture toughness KIC), the stress situation in a micro package and the long-term strength behaviour. Results for fracture toughness investigations presented in this paper were determined by the micro chevron test. The stress situation in a micro package was calculated by a thermo-mechanical Finite Element Analysis. Furthermore the residual stress in the glass layer and the linear thermal expansion coefficient were determined by a crack width measurement in an environmental scanning electron microscope.