Liquid Metal Fluidic Connection and Floating Die Structure for Ultralow Thermomechanical Stress of SiC Power Electronics Packaging

Coefficients of thermal expansion (CTE) of various materials in packaging structure layers vary largely, causing significant thermomechanical stress in power electronic packages during operation. For wirebondless SiC modules, the stress is even larger due to the structure's rigidity and the hig...

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Bibliographic Details
Published in:IEEE transactions on power electronics 2024-07, Vol.39 (7), p.7808-7814
Main Authors: Mu, Wei, Janabi, Ameer, Hu, Borong, Shillaber, Luke, Long, Teng
Format: Article
Language:English
Subjects:
Casting
Circuit boards
Electrical conduction
Electronic packaging
Electronic packaging thermal management
Feasibility
Finite element method
High temperature
Insulation
Liquid metal (LM)
Liquid metals
Liquids
Metals
Modulus of elasticity
Packaging
printed circuit board (PCB)/direct bond copper (DBC) hybrid packaging
Printed circuit boards
Printed circuits
reliability
Shear stress
SiC packaging
Silicon carbide
Stress
Substrates
Thermal cycling
Thermal expansion
Thermal stresses
thermomechanical stress
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Summary:Coefficients of thermal expansion (CTE) of various materials in packaging structure layers vary largely, causing significant thermomechanical stress in power electronic packages during operation. For wirebondless SiC modules, the stress is even larger due to the structure's rigidity and the high Young's modulus of SiC crystals. This letter takes a flexible printed circuit board (FPCB)/die/active metal brazed (AMB) packaging stack as an example to prove the feasibility of floating die structure enabled by liquid metal (LM) fluidic connection. The CTE mismatch among the die, printed circuit board, and AMB substrate is decoupled by the LM layer without compromise of thermal and electrical conduction. The finite-element analysis demonstrates a 56% reduction in von Mises stress of the device and more than 99% shear stress reduction at the FPCB-AMB interface, compared with a conventional rigid solder connection. Testing results show that LM-based packaging has a similar thermal and electrical conduction and higher breakdown voltage when compared with the soldered counterpart. Accelerated thermal cycling aging tests validate the stability of the insulation ring for LM-based packaging, especially under high-temperature conditions. The feasibility of using LM fluidic interconnections for a floating die structure of SiC packaging is validated.
ISSN:0885-8993
1941-0107
DOI:10.1109/TPEL.2024.3379121