Accepted Manuscripts

Bryce DeFigueiredo, Trent Zimmerman, Brian Russell and Larry L Howell
J. Electron. Packag   doi: 10.1115/1.4040552
Flexible printed circuit boards (PCBs) make it possible for engineers to design devices that use space efficiently and can undergo changes in shape and configuration. However, they also suffer from trade-offs due to non-ideal material properties. Here, a method is presented that allows engineers to introduce regions of flexibility in otherwise rigid PCB substrates. This method employs geometric features to reduce local stiffness in the PCB, rather than reducing the global stiffness by material selection. Analytical and finite element models are presented to calculate the maximum stresses caused by deflection. An example device is produced and tested to verify the models.
TOPICS: Design, Stiffness, Printed circuit boards, Engineers, Stress, Materials properties, Tradeoffs, Deflection, Finite element model, Shapes
Liang Yin, Chris Kapusta, Arun V. Gowda and Kaustubh Nagarkar
J. Electron. Packag   doi: 10.1115/1.4040499
As silicon carbide (SiC) power semiconductor devices continue to mature for market adoption, innovative power electronics packaging designs and materials are needed to achieve the power density and efficiency that SiC devices are entitled to. Wire bonding loops is one of the major limiting factor in traditional module packaging methods for taking full benefits of SiC devices' superior electrical and thermal properties. Wire-bondless packaging methods have been demonstrated with low losses and to allow integration of gate drive circuit. In this paper, a wire-bondless packaging platform, referred to as Power Overlay Kilowatt (POL-kW), for SiC devices is presented. The packaging platform is intended for applications of motor drives and power conversion in automotive, aerospace and renewable industries. In this paper, POL-KW module's electrical and thermal performances were first summarized from previous experimental evaluations and numerical simulations. Compared with aluminum wire bonds, the utilization of polyimide-based Cu via interconnections resulted in much reduced parasitic resistance, capacitance and inductance, contributing to significantly lower switching loss and less voltage overshoot. The POL-kW module with integrated heat sinks showed low thermal resistance, which was further reduced by double-sided cooling. Recent results were presented on reliability evaluation, including high temperature storage, temperature cycling and power cycling.
TOPICS: Wire, Power semiconductor devices, Silicon, Packaging, Wire bonding, Power density, Storage, Thermal resistance, High temperature, Temperature, Cooling, Aluminum, Computer simulation, Capacitance, Reliability, Electronic packaging, Overlays (Materials engineering), Gates (Closures), Energy conversion, Thermal properties, Aerospace industry, Circuits, Heat sinks, Motor drives
Chia-Cheng Chang, Sheng-Da Lin and Kuo-Ning Chiang
J. Electron. Packag   doi: 10.1115/1.4040297
The fatigue characteristics of Microelectromechanical systems (MEMS) material, such as silicon or polysilicon, have become very important. Many studies have focused on this topic, but none have defined a good methodology for extracting the applied stress and predicting fatigue life accurately. In this study, a methodology was developed for the life prediction of a polysilicon microstructure under bending tests. Based on the fatigue experiments conducted by Hocheng and Hung [1-2], cantilever beams with different dimensions were remodeled with mesh control technology using finite element analysis (FEA) software to extract the stress magnitude. The mesh size, anchor boundary, loading boundary, critical stress definition and solution type were well modified to obtain more correct stress values. Based on the new stress data extracted from the modified models, the optimized stress-number of life curve (S-N curve) was obtained, and the new life-prediction equation was found to be referable for polysilicon thin film life prediction under bending loads. After comparing the literature and confirming the new models, the frequency effect was observed only for the force control type and not for the displacement control type.
TOPICS: Thin films, Silicon, High cycle fatigue, Stress, Polysilicon, Microelectromechanical systems, Finite element analysis, Fatigue, Control systems, Cantilever beams, Dimensions, Computer software, Displacement, Fatigue life, Force control

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