The metallized insulating substrates work as mechanical supports for the circuitry of Power Module Packages. Due to their specific functions, substrates for power electronics are made by different materials. The conductive metal layers can assume different functions: the top metal serves as power circuitry routing while the bottom metal improves the mechanical robustness and thermal efficiency. Ceramic layer provides excellent electrical insulation. These features play an essential role in the operation of power modules, which are often operated at high voltage and high current density. The substrates, composed by materials with different thermal expansion coefficients, are subjected to cyclic stresses due to temperature variations induced by operative working conditions. The substrate layouts typically include differences in shape and/or thickness between the top and the bottom side; this generates asymmetrical distributions of stress/strain resulting in overall warpage. The variations of this warpage induce mechanical fatigue during lifetime and represent a limiting factor for reliability. The scope of the presented work is the characterization of the out of plane warpage of Active Metal Brazed substrates (AMB) by means of numerical approach. The elastoplastic properties of metal and ceramic have been measured, evaluating the thermal softening of the copper as well. These characteristics are needed to calculate AMB warpage through Finite Element Models (FEM), simulating the warpage induced by a passive temperature cycling. Warpage computed from numerical model have been benchmarked and validated with optical warpage measurements. The validated numerical model has been developed to optimize the substrate warpage variation during cycling improving the whole package reliability.
[1]
G. Pharr,et al.
An improved technique for determining hardness and elastic modulus using load and displacement sensing indentation experiments
,
1992
.
[2]
T. Rouxel,et al.
Temperature dependence of Young's modulus in Si3N4-based ceramics: roles of sintering additives and of SiC-particle content
,
2002
.
[3]
Stéphane Lefebvre,et al.
Characterisation of power modules ceramic substrates for reliability aspects
,
2009,
Microelectron. Reliab..
[4]
D. Weidmann,et al.
Determination of strength of interface in packages based on an approach using coupling of experimental and modeling results
,
2011,
2011 12th Intl. Conf. on Thermal, Mechanical & Multi-Physics Simulation and Experiments in Microelectronics and Microsystems.
[5]
P. Mawby,et al.
High temperature thermal cycling performances of DBA, AMB and thick film power module substrates
,
2016
.
[6]
H. Hirotsuru,et al.
Effect of mechanical properties of the ceramic substrate on the thermal fatigue of Cu metallized ceramic substrates
,
2016,
2016 IEEE 18th Electronics Packaging Technology Conference (EPTC).
[7]
M. Oliveri,et al.
Mechanical properties of amorphous Ge2Sb2Te5 thin layers
,
2018,
Surface and Coatings Technology.