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 longterm 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 linear thermal expansion coefficient were determined by a crack width measurement in an environmental scanning electron microscope

Reliability Aspects of Microsystems for Automotive Applications

“…For a detailed explanation of the principle, the reader should study further references. [6] It is of importance that the determined fracture toughness, as it is measured by the MC test, represents the critical value G c , i.e., when the structure fails instantly. However, this parameter is in general unsuitable for a prediction of the long-term reliability of the bonding material.…”

Glass Frit as a Hermetic Joining Layer in Laser Based Joining of Miniature Devices

“…The use of an intermediate layer has advantages which include a relatively low joining temperature (few hundred degrees Celcius), and less stringent requirements for contact surface smoothness. Suitable intermediate layers include Au/Sn solder [12], Zn [13], Al, Au [14], In [15], Ti [16], thermosetting polymer benzocyclobutene (BCB) [17], or glass frit [18][19][20][21][22]. Glass frits are of particular interest due to the required low bonding temperatures ( < 595 K ), their ability to deliver a hermetic seal with moderately rough bonding surfaces, and to conform to the surfaces being bonded -even to the extent of allowing metallic feed-throughs to be included in the joining layer [19][20].…”

Mechanical Characterization and Micro Structure Diagnostics of Glass Frit Bonded Interfaces

“…The chosen specific sample geometry resulted from the adaptation of the SEMI standard (SEMI MS5-1107) for direct Silicon wafer bonding taking the technological limitations due to screen printing into account (9). The long micro chevron and double cantilever beam (DCB) sample geometries allowed to study the slow subcritical crack growth behaviour and, thus to investigate life time properties of glass frit bonded devices (4). In general, the combination of these tests allows a comprehensive assessment of process variations considering different quality, strength and reliability aspects of the seal glass bonding technology.…”