Application of ESPI in investigating the static deformation of a lead-free joint D. Karalekas 1 , J.Cugnoni 2 , J. Botsis 2 1 Lab. Adv. Manufact. and Testing, University of Piraeus, Greece 2 Lab. Applied Mechanics & Reliability, EPFL, Switzerland Photomechanics 2006
19
Embed
Application of ESPI in investigating the static deformation of a lead-free joint D. Karalekas 1, J.Cugnoni 2, J. Botsis 2 1 Lab. Adv. Manufact. and Testing,
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Application of ESPI in investigating the static deformation of a lead-free joint
D. Karalekas1, J.Cugnoni2, J. Botsis2
1 Lab. Adv. Manufact. and Testing, University of Piraeus, Greece2 Lab. Applied Mechanics & Reliability, EPFL, Switzerland
Photomechanics 2006
Outline
Introduction General remarks Goal of research work
Experimental Work Materials and Specimens Experimental Procedure
Lead (Pb)-containing solders have been used extensively in microelectronics applications
Recent trends of worldwide environmental legislation for toxic materials and consumer demand for “green” products are accelerating the transition from Pb-containing to Pb-free solders in the electronic industry
Reliability assessment of risk factors associated with Pb-free solders requires: Better understanding of of Pb-free solders’ metallurgical and mechanical
properties Predictions of package/assembly field performance, where FEM based
projections require new valid constitutive equations and new fatigue damage criteria based on the thermomechanical loading history for the new materials
Photomechanics 2006
Introduction
Non-contact optical methods are desirable in measuring “real-time” thermomechanical deformation of such materials
ESPI is a versatile method since it requires little or no special specimen preparation, being able to measure in-plane and out-of-plane deformation with high sensitivity
The goal of the research work was to measure strain field evolution in Pb-free joints (global strain field & local strain field near the stress concentrations) at different load levels: In the elastic domain, near yield stress In the early plastic domain Near rupture, to observe failure initiation and development
Photomechanics 2006
Experimental work: materials and specimens
Photomechanics 2006
Specimen configuration: 60 mm long copper plates Sn-4.0Ag-0.5Cu solder alloy 0.2, 0.5 & 1mm solder gap
width Customized specimen
mounting devices Pure tension condition 2kN load cell Displacement controlled
Experimental work: setup
Photomechanics 2006
ESPI arrangement for in-plane measurements
Experimental work: setup
Photomechanics 2006
ESPI configuration: 633 nm wavelength He-Ne laser 768 x 572 pixels CCD camera Standard phase-shifting Differential measurements in successive steps of 3 μm
as obtained phase-shifted unwrapped
Results: vertical displacement field
Photomechanics 2006
Observation region: 22x16 mm, displ. range: ~10 microns
Results: elastic region
Photomechanics 2006
Displacement field Strain distribution
Applied load: 465 N
Results: close to yield point
Photomechanics 2006
Displacement field Strain distribution
Applied load: 817 N
Results: close to failure
Photomechanics 2006
Displacement field Strain distribution
Applied load: 1205 N
Results: displacement variation at interfaces of
the solder joint gap
Photomechanics 2006
Applied load: 1205 N
Results: local measurements
Photomechanics 2006
Displacement fieldDisplacements at interfaces
Increased magnificationObservation region: ~ 10 x 8 mm