Course Objectives This advanced course on SMT solder paste stencil printing builds upon the basics to give the attendees a larger toolkit for troubleshooting and process improvement. The session starts with the handling and verification of incoming stencils, and continues with detailed methods of troubleshooting suspected stencil issues, showing images and data from multiple real-world stencil trials. Stencil underwiping is presented, reviewing types of wipe sequences, wiper papers and solvents, particularly as they relate to modern lead-free solder pastes and the preservation of nanocoatings. Videos and ultraviolet images of the effects of cleaning and nanocoatings are shown. The course then moves to automated Solder Paste Inspection (SPI) and discusses basic types of SPI equipment. It continues with tips for production implementation and setting inspection tolerances. It then introduces simple experimental methods that can be performed quickly and easily to improve yields using SPI data. The differences between accuracy and repeatability are discussed, as are the effects of setting of reference planes and measurement thresholds. This year's new updates include results of recent stencil stepping, aperture optimization, nanocoating and miniaturization studies.
Topics Covered 1. Stencil Verification 1.1. SPI verification 1.2. Test coupons 1.3. SEM images 1.4. Cleaning before using 2. Stencil Troubleshooting 2.1. Physical damage 2.2. Foil thickness 2.3. Aperture size 2.4. Aperture location 2.5. Impact on AR & TE 2.6. Cut Quality 3. Underwiping 3.1. Purpose and methods 3.2. UV Test results 3.3. Solvent requirements 3.4. Solvent compatibility with solder pastes 3.5. Solvent and paper compatibility with nanocoatings 4. Automated Solder Paste Inspection (SPI) 4.1. SPI basics 4.2. Production implementation 4.3. Setting inspection tolerances 4.4. Improving print yields 4.5. Accuracy and Repeatability 4.6. Reference planes and measurement thresholds 4.7. Special features to improve performance 5.0 Recent studies 5.1 Step stencil keepout zones 5.2 Getting Cpk >2.0 on 008004's or 0201M's 5.3 Aperture design print repeatability for discretes 5.4 Fresh look and head-to-head comparison of nanocoatings
Sunday September 22, 2019 1:30pm - 5:00pm CDT
Room 51
PDC09: Solder Joint Reliability – Principles and Practice
*Jennie Hwang, Ph.D., H-Technologies Group Monday, September 23 | 8:30am — 12:00pm
Course Objectives The course emphasizes on practical, working knowledge, yet balanced and substantiated with science by outlining the critical “players” of solder joint reliability (e.g., manufacturing process, PCB/component coating surface finish, solder alloys), and the solder joint reliability fundamentals in fatigue and creep damage mechanisms via ductile, brittle, ductile-brittle fracture. Likely solder joint failure modes of interfacial, near-interfacial, bulk, inter-phase, intra-phase, voids-induced and surface cracks will be illustrated. To withstand harsh environments, the strengthening metallurgy to further increase fatigue resistance and creep resistance, and the power of metallurgy and its ability to anticipate the relative performance will be illustrated by discussing the comparative performance vs. metallurgical phases and microstructure. The question on whether existing life-prediction models can assure reliability will be highlighted. A relative reliability ranking among commercially available solder systems, as well as the scientific, engineering and manufacturing reasons behind the ranking will be outlined. Attendees are encouraged to bring their own selected systems for deliberation.
Topics Covered 1. Premise – critical players, definition of reliability, solder joint thermo-mechanical degradation – fatigue and creep interaction 2. Solder joint failures modes - interfacial, near-interfacial, bulk, inter-phase, intra-phase, voids-induced, surface-crack, and others 3. Solder joint failure mechanisms – ductile, brittle, ductile-brittle transition fracture 4. Solder joint strengthening metallurgy 5. Illustration of microstructure evolution vs. strengthening in Sn Cu+x,y,z and SnAgCu+x,y,z systems 6. Solder joint voids vs. reliability - causes, effects, criteria 7. Solder joint surface-crack –causes, effects 8. Distinctions and commonalties between Pb-free and SnPb solder joints 9. Thermal cycling conditions - effects on test results and test results interpretation 10. Testing solder joint reliability – discriminating tests and discerning parameters 11. Life-prediction model vs. reliability 12. Solder joint performance in harsh environments 13. What solder alloys are on the horizon and what impact will be on reliability 14. Best practices and competitive manufacturing 15. Ultimate reliability
Monday September 23, 2019 8:30am - 12:00pm CDT
Room 51
