Session: 08-01 Mini-Symposium for Professor Dasgupta I

Paper Number: 97479

97479 - Multiaxial Interaction Between Printed Circuit Board Flexure and Quad Flat Package Interconnects Experiencing Plastic Strains 

Electronic packages are increasingly pushed to survive in harsher environments, including multiaxial random vibrations. In order to meet these rougher requirements, the interaction between board, package, and the multiaxial excitation need to be well understood. Though there are previous studies documenting electronic package durability in multiaxial random vibration environments, the package variety is sparse (large inductors and quad flat packages (QFPs)) and the underlying physics is limited (single lead packages).

In this study, durability data is gathered from previously reported experiments subjecting QFPs to simultaneous multiaxial random vibrations. The results were contrary to the general nonlinear multiaxial interaction theory; the QFPs with thinner packages and lower standoff resulted in severely lower time to failures (TTFs) than QFPs with thicker packages and higher standoff. The cause of such low TTFs when the QFPs were subject to multiaxial random vibration is hypothesized to be due to exceeding the yield strain in the copper gullwing leads. The plastic deformations are thought to transition the gullwing from acting like a spring to acting like a hinge. This hinge-like motion resulted in a considerably lower component rocking natural frequency. As such, the board flexure mode and component rocking mode were in a more damaging relation as relating to frequency and phase, leading to a nonlinear superposition of lead strain. This work employs a multiscale global-local submodeling approach to explore the hinge-like component rocking motion hypothesis and subsequent nonlinear interaction.

Presenting Author: Jonathan Kordell Ansys