Thermomechanical Analysis and Package-Level Optimization of Mechanically Flexible Interconnects for Interposer-on-Motherboard Assembly

This paper explores different means by which the interconnect reliability is improved and interposer warpage is decreased for an interposer-to-board integration platform using mechanically flexible interconnects (MFIs). Central to this exploration is the design and distribution/orientation of the MFIs on the interposer. Using finite-element-based tool ANSYS, different MFI distributions and configurations are investigated. A radially oriented interconnect distribution in which the MFIs line up along the contours of thermal expansion/contraction is evaluated. Furthermore, a multiobjective genetic algorithm is employed to reduce max von-Mises stress in the MFIs and warpage in the interposer for each MFI distribution configuration. The impact of chip size and MFI pitch (from 400 to 1200 mu m) on the mechanical integrity of the MFIs and interposer are also explored.