Chip-Level Interconnects, Flip Chip and Underfills

In this research area, materials and processes are being explored for flip chip assemblies deployed in extreme thermal cycling environments. The primary objective is to develop a fundamental understanding of the reliability of flip chip applications in automotive and other harsh environment applications. Project deliverables include design and material guidelines for flip chip packages used in the automotive thermal cycling environment; material properties and adhesion characteristics of underfill encapsulants; flip chip thermal cycling reliability data; assembly and processing recommendations; and finite element and material models for application to future package designs.

Device Side Die Stress After CBGA Assembly and Heat Sink Clamping


Dr. Jeff Suhling (Research Leader)


  • Develop a fundamental understanding of the influence of package design, manufacturing, and materials on the reliability of flip chip packaging in harsh environments. Including but not limited to flip chip on laminate, flip chip BGA packaging, CSP, redistributed die, UltraCSP
  • Measure and predict the reliability of flip chip packaging in harsh environment thermal cycling and high end microprocessor packaging
  • Study next generation materials such as nano-structured underfills, high reliability substrates (e.g. STABLCOR), thermal interface materials, and chip-level interconnects
  • Develop a detailed understanding of underfill behavior and properties including material behavior (Stress-Strain and Creep), interfacial adhesion and failure criteria

Project Titles

  • P10-201 Underfill Stress-Strain and failure behavior
  • P10-202 In situ die stress measurements in flip chip packaging
  • P10-203 Modeling and material characterization for flip chip packaging
  • P09-201 Characterization and modeling of advanced substrates


  • 3D Viscoelastic Model for Underfill Material Behavior  - Nusrat Chhanda (ME), Jeff Suhling (ME))
  • Implementation of Viscoelastic Models for Underfill in Finite Element Analysis  - Nusrat Chhanda (ME), Jeff Suhling (ME)
  • FEA Predictions of Die Stresses in Microprocessor Assemblies Subjected to Temperature Change and Thermal Cycling - Mohammad Motalab (ME), Jordan Roberts (ME) , Jeff Suhling (ME)
  • Development of Lamination Theory for STABLCOR Substrates - Kun Y. Wang(ME) , Jeff Suhling (ME)
  • Effect of Heat Sink Clamping on Die Stresses in Microprocessor Packages  - Jordan Roberts (ME), Mohammad Motalab (ME), Jeff Suhling (ME))
  • Effect of BGA Solder Balling on Microprocessor Die Stress - Jordan Roberts (ME), Jeff Suhling (ME)