Graduation Semester and Year

2016

Language

English

Document Type

Thesis

Degree Name

Master of Science in Mechanical Engineering

Department

Mechanical and Aerospace Engineering

First Advisor

Dereje Agonafer

Abstract

The assessment of board level solder joint reliability during thermal cycling is very important for electronic packages. During thermal cycling, the mismatch in Coefficient of Thermal Expansion (CTE) between the materials used in the package induces stress on the solder interconnects and result in deformation stresses. Finite element tools are widely used for rapid design optimization and also for understanding board level reliability issues. Lumped board properties approach, explicit geometry approach, and ECAD approach are the three widely used approaches for creating models for PCBs. In the lumped board properties approach, orthotropic elastic material properties are assigned to PCBs. However, for temperatures near and beyond the glass transition temperature, materials behave in a viscoelastic manner. In which case, considering viscoelastic properties would result in a more accurate representation than the orthotropic elastic lump model. In this thesis, a comparative study on the linear elastic and viscoelastic modeling of PCB is done and how it affects the board level reliability of Packages under thermal cycling. The viscoelastic material properties of PCBs are characterized using dynamic mechanical analyzer (DMA). The frequency and temperature dependent complex moduli are obtained from the DMA. The obtained results are used to model the PCBs as viscoelastic materials on ANSYS. Thermal cycling is performed in ANSYS and the results obtained are compared to those obtained from the elastic modeling of PCBs for WCSP.

Keywords

Viscoelastic modeling, WCSP, Thermal cycling

Disciplines

Aerospace Engineering | Engineering | Mechanical Engineering

Comments

Degree granted by The University of Texas at Arlington

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