Chair Materials and Reliability of Micro Technical Systems
Prof. Dr. Bernhard Wunderle
Phone +49 (0)371 531 24450
Fax +49 (0)371 531 24459
Main research topics
- Thermo-mechanical reliability
- Thermal management
Extended description of Research topics
Reliability as a scientific discipline is concerned with the analysis, assessment and prediction of the lifetime of microelectronic systems (e.g. of interconnects and interfaces of standard and advanced packages, BEOL-layers, MEMS, 3Darchitectures, SIP, power packages, etc).
The professorship is technology-open, i.e. the group develops experimental and simulative methods for reliability assessment and prediction for various integration technologies in the field of electronic systems in cooperation with technology partners from industry and academia. These methods also involve stress testing and failure analysis as well as thermal management concepts.
Reliability prediction crucially hinges upon the correct and accurate description of the respective failure mechanisms. The research therefore comprises the development of lifetime models for micro systems starting from the material level up to the system level, based on the physical understanding of the materials involved in terms of their properties and failure mechanisms as function of their structure and external loading conditions (“physics of failure”).
- Thermal and mechanical characterization of materials and compounds of micro systems under typical, applicationrelevant loading conditions such as e.g. temperature, moisture and vibration. Special customized equipment is available enabling characterization and accelerated stress testing along the length-scale.
- Characterization of cracks in materials and interfaces by means of fracture-mechanical methods. A special competence of the professorship is the development of customised loading stages which allow e.g. rapid interface delamination testing by Advanced Mixed-mode Bending (AMB).
- Thermal material and system characterization by pulse IR thermography and special customized precision test stand to characterize even thin and highly conductive thermal interface materials such as e.g. sintered silver. Special thermal test dies are available, too.
- Calculation of failure parameters as a function of external loading conditions. Selected lifetime models are available, e.g. for eutectic solders.
- Multi-physics approaches to couple e.g. electrical, thermal and mechanical (Finite Element simulations) for system simulation.
- Multi-scale approaches (e.g. Molecular Dynamics simulation) to obtain structure-property correlations between the nanoscale and the continuum. Current research topics include CNT-metal interfaces or polymers under moisture influence.
- Modern non-contact deformation analysis to verify simulation results on various length scales. So cracks can be observed in-situ in the micro and nano domain (e.g. nm-resolution by DIC in combination with REM, AFM or FIB)
- Mechanical testing, reliability testing and crack tracing (e.g. by pulse IR thermography) on specimens of small geometry under combined loading conditions.
- A new high vacuum chamber is now available allowing in-situ optical and IR microscopy for local temperature and deformation measurements on in-situ powered devices.