Active investigation continues on various alloys used to replace lead for soldering in electronics components. Use of lead has dropped since the Restriction of Hazardous Substances Directive took effect in July, 2006. Historically, interconnections in electronic components have been made using tin/lead solder formulations. Those materials melt at 183C, while the thermoset and thermoplastics used in electronics have temperature limits up to 235C. The glass transition temperature of FR-4, a common PCB material, is between 140-175C. The resin softens as temperatures rise. New lead-free alternates such as SAC become liquid at 217C. Other lead-free solders have even higher melting points, causing failures of laminates and thermoplastics. Materials suppliers are struggling to adapt, says James Hall of ITM Consulting, who gave an interesting overview of the issue during a conference session at National Manufacturing Week in Rosemont, IL. “Just increasing cross-linking in the modified epoxies used in laminates is not the way to go,” he says. Cross-linking increases the brittleness of the laminates, creating problems when the boards are drilled. Specialty thermoplastics, such as modified nylons, are also experiencing problems because of the high solder temperatures. Explorations continue on new plastics as well as new solder formulations, including significant use of dopants such as nickel and germanium that provide specific property enhancements for various reasons.
Oak Ridge National Laboratory has developed a surface preparation method to improve joining carbon composites with aluminum, with potentially far-reaching ramifications for high-volume industrial applications.
Focus on Fundamentals consists of 45-minute on-line classes that cover a host of technologies.
You learn without leaving the comfort of your desk. All classes are taught by subject-matter experts and all are archived.
So if you can't attend live, attend at your convenience.