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Monday, October 15 • 8:30am - 12:00pm
PDC 12: Achieving High Reliability for Lead-Free Solder Joints - Materials Consideration

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PDC12: Achieving High Reliability for Lead-Free Solder Joints - Materials Consideration

*Ning- Cheng Lee, Ph.D., Indium Corporation
Monday, October 15 | 8:30am — 12:00pm

Course Objectives
This course covers the detailed material considerations required for achieving high reliability for lead-free solder joints. The reliability discussed includes joint mechanical properties, development of type and extent of intermetallic compounds (IMC) under a variety of material combinations and aging conditions and how those IMCs affect the reliability. The failure modes, thermal cycling reliability, and fragility of solder joints as a function of material combination, thermal history, and stress history will be addressed in details, and novel alloys with reduced fragility will be presented. Electromigration, corrosion, and tin whisker will also be discussed. The emphasis of this course is placed on the understanding of how the various factors contributing to the failure modes, and how to select proper solder alloys and surface finishes for achieving high reliability. Also will be presented are the desirable future alloys and fluxes in order to meet the challenge of miniaturization.

Topics Covered
1. Implementation Status
2. Prevailing Materials
1) Prevailing Solder Alloys
2) Prevailing Surface Finishes
3. Surface Finishes Issues
1) Issues of ENIG
2) Issues of ImAg
4. Mechanical Properties
1) Shear & Pull Strength
2) Creep
5. Intermetallic Compounds
1) Interaction of Cu and Ni
2) Effect of Cu Content in SAC
3) Effect of Ni in Cu Pad
4) Effect of Alloy Additives
5) Effect of Heat History
6) Formation of Interfacial Void
6. Failure Modes
1) Grain Boundary Sliding & Cavitation
2) Grain Coarsening
3) Grain Orientation
4) Lead Contamination
5) Mixed Alloys
6) Interfacial Voiding
7. Thermal Cycle Reliability
1) Effect of Thermal Cycle Test Condition
2) Effect of PCB Surface Finish Cu vs Ni
3) Effect of Reflow Temperature
4) Reliability of Reworked SMT Joints
8. Reliability of Through-Hole Joints
1) Large and Thick Board
2) Partially Filled Through-Hole
9. Fragility
1) Fragility of Lead-Free Solder Joints
2) Effect of Component Finish
3) Effect of Alloy, PCB Surface Finish, Reflow History, and Strain Rate
4) Effect of IMC Thickness
5) Effect of Isothermal Aging
6) Effect of Thermal Cycling
7) Effect of Intermetallic Morphology
8) Novel Alloys with Reduced Fragility
10. Reliability – Electromigration
1) Influence of Electromigration and Temperature on Resistance
2) Effect of Current Density & Back Stress on IMC Thickness
3) Effect of Current on IMC Thickness, Joint Temp and Strain
4) Effect of Electromigration on Mechanical Property
5) Effect of Cu UBM Thickness on Electromigration
11. Reliability – Corrosion
1) SAC405
2) Corrosion Resistance of PWB Finishes
12. Tin Whisker

Monday October 15, 2018 8:30am - 12:00pm CDT
Room 53