Thermal-mechanical simulation of embedded module based on organic substrate

Embedded devices encapsulated by electronic packaging offer significant advantages in terms of miniaturization, cost and performance. A new packaging concept, Embedded Technology, is highly conducive to the aforementioned advantages where active components are directly embedded into organic substrates without incurring subsequent package assembly processes such as flip-chip technology. However, one of the most significant drawbacks of Embedded Technology is its inherently poor thermal characteristics, which is symptomatic of most embedded device topologies. This paper presents a practical, streamline thermal management design methodology that mitigates thermal-mechanical risks of Embedded Technology while balancing electrical performance and cost considerations. The proposed methodology first demonstrates that the associated thermal-mechanical weaknesses of Embedded Technology can be mitigated through judicious selection of an appropriate substrate with good thermal conductivity, low Coefficient of Thermal Expansion (CTE) and high degree of hermeticity. A heuristic thermal-mechanical study of an embedded power MOSFET module is exemplified in this paper; its thermal performance is characterized under both steady-state and transient conditions thereby highlighting the embedded module´s sensitivity to material properties and convection properties. A power MOSFET bare die from Alpha & Omega Semiconductor Co. is applied in this embedded module. Thermal management characterization of the structure is subsequently scrutinized under different loading conditions, which can be done efficiently by numerical studies based on Finite Element Analyses (FEA). Simulation results reveal that the thermal-mechanical properties of the embedded module under forced-convection are much better compared to the properties under natural-convection. The thermal performance of the embedded module under forced convection conditions is sensitive to changes in temperature. Lastly, thermal-me- hanical simulations depict elevated stress concentrations appearing at the central portion of the MOSFET die edge, which could lead to potential brittle fracture. Qualitative correlation of the predicted stress contours with observed cross-sectioned SEM samples demonstrate that mitigating measures can be incorporated into the baseline simulation environment, a priori, to truncate product design iterations and improve process reliability.