Printed Circuit Design & Fab - January 2008 - (Page 25) 5 35 µm [1.4 mils] Reflow 28 µm [1.1 mils] Barrel Stress (Mpa) MLB: Glass / Epoxy No Lands Two Lands 1 0 Distance from Mid-plane (mils) 70 Double wave – single pass BIGLARI, ET AL, IDEALS; L: TH. AHRENS, FRAUNHOFER INSTITUT D. MATTIX, QUALCOMM INC. FIGURE 4. Graph showing the z-direction tension stresses on the copper barrel of a plated-through hole9. 35 µm [1.4 mils] 22 µm [0.9 mils] FIGURE 7. Micro-photographs showing extent of copper dissolution during wave and reflow soldering. FIGURE 5. Micro-photograph of plated-through hole without any inner-layer connections/lands and the resulting full holewall pull-away after lead-free wave soldering10. FIGURE 8. Micro-photographs showing damage to a PCB from the vapor pressure generated by soldering temperature. FIGURE 6. Micro-photograph of plated-through hole with full complement of inner-layer connections/lands10. Moisture Absorption and Bake-Out Moisture absorption can play a significant role in whether a PCB can survive the high temperatures required for lead-free soldering. Thus, it is imperative that both test coupons and production PCBs undergo adequate moisture bake-outs just prior to assembly. These bake-dry or vacuum bake procedures should be done at temperatures not to exceed 105˚C JANUARY 2008 for the number of hours (up to 24) required to sufficiently remove moisture from the PCBs. Vapor pressure within the PCBs can cause both cohesive and adhesive failure modes, depending on where the weakest bonds are located, whereas thermal decomposition due to inadequate thermal stability leads predominantly to cohesive failures. It should be noted that the vapor pressure within a PCB roughly doubles from 220˚C to 260˚C. The consequences of high vapor pressure can be seen in FIGURE 8. Testing PCB testing using IST (Interconnect Stress Testing) as per IPC– TM-650, 2.6.2611, or HATS (Highly Accelerated Thermal Shock) as per IPC-TM-2.6.7.2B12 assures primarily long-term reliability PRINTED CIRCUIT DESIGN & FAB 25
Table of Contents Feed for the Digital Edition of Printed Circuit Design & Fab - January 2008 Printed Circuit Design & Fab - January 2008 Contents Our Line Market Watch Around the World Happenings ROI PTH Reliability: Designing to Improve PTH Reliability EMC for the Real World PTH Reliability: The Survival and Long-Term Reliability of Lead-Free PCBs iNEMI's Emerging Technologies: Research Priorities for the Electronics Industry Printed Circuit Design & Fab Annual Buyers Guide Special Suppliers Section Guide to Products and Services Off the Shelf: Designcon Preview Marketplace Ad Index BGA Bulletin Printed Circuit Design & Fab - January 2008 Printed Circuit Design & Fab - January 2008 - Printed Circuit Design & Fab - January 2008 (Page Cover1) Printed Circuit Design & Fab - January 2008 - Printed Circuit Design & Fab - January 2008 (Page Cover2) Printed Circuit Design & Fab - January 2008 - Printed Circuit Design & Fab - January 2008 (Page 1) Printed Circuit Design & Fab - January 2008 - Contents (Page 2) Printed Circuit Design & Fab - January 2008 - Contents (Page 3) Printed Circuit Design & Fab - January 2008 - Our Line (Page 4) Printed Circuit Design & Fab - January 2008 - Our Line (Page 5) Printed Circuit Design & Fab - January 2008 - Market Watch (Page 6) Printed Circuit Design & Fab - January 2008 - Market Watch (Page 7) Printed Circuit Design & Fab - January 2008 - Around the World (Page 8) Printed Circuit Design & Fab - January 2008 - Around the World (Page 9) Printed Circuit Design & Fab - January 2008 - Around the World (Page 10) Printed Circuit Design & Fab - January 2008 - Around the World (Page 11) Printed Circuit Design & Fab - January 2008 - Happenings (Page 12) Printed Circuit Design & Fab - January 2008 - Happenings (Page 13) Printed Circuit Design & Fab - January 2008 - ROI (Page 14) Printed Circuit Design & Fab - January 2008 - ROI (Page 15) Printed Circuit Design & Fab - January 2008 - PTH Reliability: Designing to Improve PTH Reliability (Page 16) Printed Circuit Design & Fab - January 2008 - PTH Reliability: Designing to Improve PTH Reliability (Page V1) Printed Circuit Design & Fab - January 2008 - PTH Reliability: Designing to Improve PTH Reliability (Page V2) Printed Circuit Design & Fab - January 2008 - PTH Reliability: Designing to Improve PTH Reliability (Page 17) Printed Circuit Design & Fab - January 2008 - PTH Reliability: Designing to Improve PTH Reliability (Page 18) Printed Circuit Design & Fab - January 2008 - PTH Reliability: Designing to Improve PTH Reliability (Page 19) Printed Circuit Design & Fab - January 2008 - EMC for the Real World (Page 20) Printed Circuit Design & Fab - January 2008 - EMC for the Real World (Page 21) Printed Circuit Design & Fab - January 2008 - PTH Reliability: The Survival and Long-Term Reliability of Lead-Free PCBs (Page 22) Printed Circuit Design & Fab - January 2008 - PTH Reliability: The Survival and Long-Term Reliability of Lead-Free PCBs (Page 23) Printed Circuit Design & Fab - January 2008 - PTH Reliability: The Survival and Long-Term Reliability of Lead-Free PCBs (Page 24) Printed Circuit Design & Fab - January 2008 - PTH Reliability: The Survival and Long-Term Reliability of Lead-Free PCBs (Page S1) Printed Circuit Design & Fab - January 2008 - PTH Reliability: The Survival and Long-Term Reliability of Lead-Free PCBs (Page S2) Printed Circuit Design & Fab - January 2008 - PTH Reliability: The Survival and Long-Term Reliability of Lead-Free PCBs (Page S3) Printed Circuit Design & Fab - January 2008 - PTH Reliability: The Survival and Long-Term Reliability of Lead-Free PCBs (Page S4) Printed Circuit Design & Fab - January 2008 - PTH Reliability: The Survival and Long-Term Reliability of Lead-Free PCBs (Page 25) Printed Circuit Design & Fab - January 2008 - PTH Reliability: The Survival and Long-Term Reliability of Lead-Free PCBs (Page 26) Printed Circuit Design & Fab - January 2008 - iNEMI's Emerging Technologies: Research Priorities for the Electronics Industry (Page 27) Printed Circuit Design & Fab - January 2008 - iNEMI's Emerging Technologies: Research Priorities for the Electronics Industry (Page 28) Printed Circuit Design & Fab - January 2008 - iNEMI's Emerging Technologies: Research Priorities for the Electronics Industry (Page 29) Printed Circuit Design & Fab - January 2008 - iNEMI's Emerging Technologies: Research Priorities for the Electronics Industry (Page 30) Printed Circuit Design & Fab - January 2008 - iNEMI's Emerging Technologies: Research Priorities for the Electronics Industry (Page 31) Printed Circuit Design & Fab - January 2008 - Special Suppliers Section (Page 32) Printed Circuit Design & Fab - January 2008 - Special Suppliers Section (Page 33) Printed Circuit Design & Fab - January 2008 - Special Suppliers Section (Page 34) Printed Circuit Design & Fab - January 2008 - Special Suppliers Section (Page 35) Printed Circuit Design & Fab - January 2008 - Guide to Products and Services (Page 36) Printed Circuit Design & Fab - January 2008 - Guide to Products and Services (Page 37) Printed Circuit Design & Fab - January 2008 - Guide to Products and Services (Page 38) Printed Circuit Design & Fab - January 2008 - Guide to Products and Services (Page 39) Printed Circuit Design & Fab - January 2008 - Guide to Products and Services (Page 40) Printed Circuit Design & Fab - January 2008 - Guide to Products and Services (Page 41) Printed Circuit Design & Fab - January 2008 - Guide to Products and Services (Page 42) Printed Circuit Design & Fab - January 2008 - Off the Shelf: Designcon Preview (Page 43) Printed Circuit Design & Fab - January 2008 - Marketplace (Page 44) Printed Circuit Design & Fab - January 2008 - Marketplace (Page 45) Printed Circuit Design & Fab - January 2008 - Marketplace (Page 46) Printed Circuit Design & Fab - January 2008 - Ad Index (Page 47) Printed Circuit Design & Fab - January 2008 - BGA Bulletin (Page 48) Printed Circuit Design & Fab - January 2008 - BGA Bulletin (Page Cover3) Printed Circuit Design & Fab - January 2008 - BGA Bulletin (Page Cover4)
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