Finite Element Modeling of Advanced Interconnections

N. Bhandarkar
Point of Contact: pecht@calce.umd.edu

Objectives

Develop detailed Finite Element Analysis (FEA) models that allow computation of thermal, thermomechanical, and mechanical responses for Advanced Interconnect Technology (AIT) packages. Develop these models into software tools.

Background

AIT packages are multichip modules (MCMs) that utilize advanced packaging technology for interconnections between chips. For new technologies, it is important to understand potential reliability problems and failure mechanisms in order to develop suitable technology characterization and qualification procedures.

This modeling effort forms part of a joint NASA-Army-Navy-Air Force Reliability Technology (RELTECH) program to develop a detailed understanding of reliability of AIT structures in space and military environments. New packaging technologies, will be analyzed such as GE's overlaid high-density interconnects (HDI), which places active chips within wells formed on the substrate and then overlays dielectric layers, containing current traces for interconnection. Chip's multichip modules and other technologies, such as three- dimensional die stacks, are also being examined as part of the program.

Approach

The effort consists of developing global and local three-dimensional FEA models for analyzing AIT structures. The global models provide analysis at the package level, while the local models provide refined analyses of specific vulnerable substructures. During the global modelling procedure, dimensions for such structures as the substrate, the wells within the substrate, and the chips are established. The material property for the overlaid interconnection layers is described using a rule of mixtures.

On the local model level, geometry for structures such as vias, bond pads, metallization lines and various material interfaces are established, and the exact material properties are used. The finite element models are automatically generated and analyzed for user- input dimensions and material properties. Each model is integrated into a generic software tool for government, customer, and CALCE EPRC use, with flexibility to extend capabilities to include newly developed AIT technologies.

The software tool facilitates model building and interpretation of results. The models analyze the AIT module's global and substructural responses to thermal, thermomechanical, and mechanical loads caused by external thermal cycling, mechanical loads, and device power-on, power-off. The AIT tool can be used to examine potential failure mechanisms and to assess the limits of operating conditions and external environments that cause failures.

Work Accomplished