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 μm) on the mechanical integrity of the MFIs and interposer are also explored.