Open AccessReliability and Performance of Wafer Level Fan Out Package for Automotive Radar
Author(s) -
Walter Hartner,
M. Nießner,
F. Arcioni,
Manfred Fink,
Christian Geißler,
Birgit Hebler,
G. Haubner,
Maciej Wojnowski
Publication year - 2021
Publication title -
journal of surface mount technology
Language(s) - English
Resource type - Journals
ISSN - 1093-7358
DOI - 10.37665/smt.v34i1.12
Subject(s) - ball grid array , temperature cycling , failure mode and effects analysis , radar , reliability (semiconductor) , automotive industry , thermal , wafer , microwave , materials science , vibration fatigue , ball (mathematics) , printed circuit board , vibration , electronic engineering , mechanical engineering , automotive engineering , soldering , acoustics , engineering , fatigue testing , structural engineering , electrical engineering , optoelectronics , composite material , telecommunications , power (physics) , mathematical analysis , physics , mathematics , quantum mechanics , meteorology , aerospace engineering
Embedded wafer level ball grid array (eWLB) or FO-WLP (Fan-out wafer-level packaging) is investigated as a package for MMICs (Monolithic Microwave Integrated Circuit) for automotive radar applications in the 77GHz range. Special focus is put on the thermo-mechanical performance to achieve automotive quality targets. The typical fatigue modes “solder ball fatigue” and “copper fatigue”, evolving during thermo-mechanical stress like cycling on board will be discussed. Simulation as well as experimental preparation results for typical fatigue levels are given. In addition, several influencing parameters are listed and rated regarding their effectiveness. The theoretical framework why solder ball fatigue is the only failure mode causing electrical failure is provided.
The impact of different thermo-mechanically driven fatigue modes is discussed. The two important parameters to be considered for the functionality of the Radar system are RF (Radio Frequency) and thermal performance.
For elaborating the RF performance with present fatigue modes, the phase shift between different channels and pads is analyzed by full-wave EM (Electromagnetic) simulation. It is found that for fatigue levels up to 90% the phase shift stays below specification for single fatigue modes and may approach specification only for an unlikely combination of all 90% fatigue modes.
For assessing the thermal performance with present fatigue modes, thermal simulation as well as thermal measurements are used. Assuming 50% degradation in average for all thermal balls, an increase in RTH of up to about 30% is seen. On average for all thermal measurements, the deviation between measurement and simulation is within ±1°C.