Technical Paper

Pushing the Envelope in DFM

Prepared by Colin Koh, Paul Gunn, Muhammad Syafiq, Takuto Yoshida.

Presented at BiTS Workshop, Arizona March 15 -18, 2015 & BiTS Workshop, Shanghai on October 21, 2015

Contents

  • Socket 1 Design
  • Improved Socket 2 Design
  • First FEA Simulation for Socket 2
  • FEA Simulation Improvement
  • Compare FEA Simulation and Actual Measurement
  • Improved Socket 3 Design
  • FEA Simulation Improvement
  • Compare FEA Simulation and Actual Measurement
  • Conclusion

 

Socket 1

Design

  • Total 1656 pins for 6 devices
  • 1 Top Plate (TP) Design
  • Socket side 6x M3 screws to keep TP coplanar at pin areas
  • Without FEA

Coplanarity Measurement

  • Target 0.050mm for coplanarity
  • Max. 0.116mm coplanarity from measurement
  • Warpage trend shows at center area
  • TP hardness is not enough
  • Tight screws is far from pin areas
  • FEA is required for next design

Improved Socket 1 Simulation & Measurement

  • Max. 0.129mm coplanarity from improved simulation
  • Max. 0.116mm coplanarity from measurement

Compare Socket 1 Simulation and Actual Measurement

  • Coplanarity error rate is 20% or less

Socket 2

Improved Socket 2 Design

  • Total 2370 pins for 6 devices
  • Improvements
    • Stainless Steel Holder & Ceramic Peek TP
    • 12x TP screws closer to pin area
    • Design with FEA simulation

First FEA Simulation for Socket 2

  • Coplanarity values are different in nominal and worst case
  • We estimated actual coplanarity close to nominal case

Socket 2 Coplanarity Measurement

  • Target 0.050mm for coplanarity
  • Max. 0.125mm coplanarity from measurement
  • Coplanarity measurement close to worst case
  • Need to improve the FEA

FEA Simulation Improvement

  • Implement elastic membrane technique
    • To predict deformation
    • To predict stress values
  • Elastic membrane technique provides
    • More stiffness reliability
    • More robust design
  • Refer to Prabakaranand Pal, Finite Element Analysis using Elastic Membrane Technique for Test Socket Design Optimization (BiTS, 2008)

Improved Socket 2 Simulation & Measurement

  • Max. 0.116mm coplanarity from improved simulation
  • Max. 0.125mm coplanarity from measurement

Compare Socket 2 Simulation and Actual Measurement

  • Coplanarity error rate is 19% or less

Socket 3

Improved Socket 3 Design

  • Total 2430 pins for 6 devices
  • Change TP material to Machinable Ceramic
  • Target 0.050mm for coplanarity
  • Max. 0.019mm coplanarity from improved simulation

Improved Socket 3 Simulation & Measurement

  • Max. 0.019mm coplanarity from improved simulation
  • Max. 0.023mm coplanarity from measurement

Compare Socket 3 Simulation and Actual Measurement

  • Coplanarity error rate is 21% or less

Conclusion

  • FEA simulation using Elastic Membrane technique proves good DFM relationship between design to actual socket
  • FEA provides more robust design and stiffness to enhance product reliability

Reference

Prabakaranand Pal, 2008, Finite Element Analysis using Elastic Membrane Technique for Test Socket Design Optimization, Burn-In and Test Socket Workshop, Hot Topics Session