Low Cycle Fatigue Behavior of Lead Free Solder EM388F: A Case Study

Low Cycle Fatigue Behavior of Lead Free Solder EM388F: A Case Study
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This final presentation by Kuan Gary Lu from the Materials Science & Engineering department explores the low cycle fatigue behavior of lead free solder EM388F

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PowerPoint presentation about 'Low Cycle Fatigue Behavior of Lead Free Solder EM388F: A Case Study'. This presentation describes the topic on This final presentation by Kuan Gary Lu from the Materials Science & Engineering department explores the low cycle fatigue behavior of lead free solder EM388F. The key topics included in this slideshow are . Download this presentation absolutely free.

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Slide1Low-Cycle Fatigue Behaviorof Lead-Free Solder EM388F Final Presentation Kuan (Gary) Lu Materials Science & Engineering April 30 2008

Slide2Outline• Introduction – Solder Alloys – Fatigue behavior of Solder • Case study – Frequency effect – Temperature effect – Solder composition – Solder joint

Slide3Introduction: Solder in Microprocessor• Solder provides electrical, mechanical and thermal interconnects. • Thermal-mechanical fatigue of solder joints during normal usage. (Strain controlled fatigue) Silicon Chip Plastic substrate Solder bump Underfill CTE: 2.6ppm/ o C for Si; ~15ppm/ o C for PCB

Slide4Introduction: Solder Alloys• Eutectic solders: – 63Sn-37Pb – 96.5Sn-3.5Ag ( Pb-free ) • Small addictives: Cu, Bi, Sb, Zn,... • Some Thermal-mechanical properties: – High homologous temperature @ RT (~0.6T m ); – Time dependent creep deformation; – Low-Cycle Fatigue (N f <10 4 ).

Slide5Solder under Cyclic Load (strain control)• Strain softening in the beginning: – Stress amplitude approaches a steady state. • Stress drops dramatically at the end of fatigue life. • Coffin-Manson eqn.: J.A. Bannantine, Fundamentals of Metal Fatigue Analysis. 1990. C. Andersson, Mater. Sci. Eng.A 394 2005

Slide6General Approaches in Solder Fatigue Study• Strain controlled (0.1~10% total strain); • Bulk solder (regulated by ASTM) or solder joints; • Isothermal fatigue test or TMF test; • Failure criteria: 25% or 50% of stress drop; • Variables to study: Solder composition, Temperature, frequency, solder joint geometry and metallization,…. • Strain-N f  log plot, derive Coffin-Manson coefficients; • Failure analysis. Dogbone bulk solder (unit: mm)

Slide7Case Study: Frequency Effect• Bulk 96.5Sn-3.5Ag • Isothermal (20 o C) C. Kanchanomai, Mater. Sci. Eng.A 345 2003

Slide8Case Study: Frequency Effect• Coffin-Manson relationship: C. Kanchanomai, Mater. Sci. Eng.A 345 2003

Slide9Case Study: Frequency Effect• Eckel relationship: • Frequency-modified Coffin-Manson relationship: C. Kanchanomai, Mater. Sci. Eng.A 345 2003

Slide10Case Study: Temperature Effect• Bulk 96.5Sn-3.5Ag • Isothermal (20 o C, 85 o C, 120 o C) • Frequency: 0.1Hz C. Kanchanomai, Mater. Sci. Eng.A 381 2004

Slide11Case Study: Temperature EffectC. Kanchanomai, Mater. Sci. Eng.A 381 2004

Slide12Case Study: Solder composition• Bulk solder • Isothermal (RT) 3.5Ag C. Andersson, Mater. Sci. Eng.A 394 2005

Slide13Case Study: Solder Joint• Shear test @ RT; • Hourglass shape solder joint; • Cu/Ni/Au metallization; • Frequency: 0.2Hz. (mm) C. Andersson, Mater. Sci. Eng.A 394 2005

Slide14Case Study: Solder JointLow strain level High strain level C. Andersson, Mater. Sci. Eng.A 394 2005

Slide15Complexity of Solder Joint Study• Sample geometry effect; • Intermetallic compound (IMC); • Crack path may depend on: – Solder composition; – Under bump metallization (UBM); – Strain range.

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