New High Reliability Lead-Free Solder Alloy for Electronic Application in Extreme Environment
Authors: Md Hasnine, Ph.D., Xiang Wei, Ph.D. Company: Kester Inc, An Illinois Tool Works Company Date Published: 9/22/2019
Abstract: High reliability solders are widely used in electronic applications such as automobiles, trains, aerospace, oil drills, downhole gas exploration and power stations. Due to the internet of things (IoT) revolution associated with challenging operating environments, the need for high power densities, high reliability solder has been an urgent priority in the electronic assembly industry. The operating temperature of high reliability solder alloys varies between 100 ºC – 200 ºC depending on applications. Solder joints exposed to elevated temperatures for long times lose their mechanical strength and structural integrity. Thermal aging causes the grain growth of bulk solder as well as the coarsening of the different phases. This microstructural evolution results in the reduction of the bulk solder elastic and plastic properties including tensile strength, yield stress and creep. Thermal aging also enhances the intermetallic growth between substrate and solder which weakens the solder joint reliability. The mechanical properties of solder alloys can be greatly influenced by the addition of alloying elements or micro-alloying. Addition of micro alloys modifies the microstructure and alter the bulk alloy characteristics; increase the volume fraction of eutectic phase and alter the crack pattern thus improve the drop and shock reliability performance. It’s also enhanced the interfacial IMC layer properties by improving the ductility and toughness. Hence, this paper describes a high reliability lead-free solder alloy providing a lower undercooling temperature, improved thermo-mechanical reliability, and high temperature creep resistance in extreme environments.
High reliability, solder, IMC, mechanical properties, creep, microstructure