Solder Alloys

About

For power electronics to operate reliably at temperatures exceeding 200 ˚C, they require die attach materials with higher performance compared to traditional solders and epoxy-based adhesives. As power dissipation of components in-reases and overall package size decreases, engineers must innovate to ensure components don't overheat. Devices that run cooler last longer. In addition, in light of the Restriction of Hazardous Substances Directive (RoHs) in the European Union, and in advance of United States federal and state regulations, there is a growing focus on developing high-melting point (HMP) solders that do not contain lead (Pb). Binghamton University material scientists have timely de-signed a series of high-bismuth (high-Bi) ternary alloy solders that not only have high melting temperature but also meets industry thermal management challenges.  This breakthrough alloy can replace high-Pb materials that currently domi-nate high temperature electronics applications. High-tin (Sn) solders inherently do not work over 200 ˚C due to their approaching too closely their melting points. Other solders such as hard solders are expensive and are susceptible to thermal fatigue failure. The improvement of the current invention is based on the high melting temperature of Bi, and alloying it with other metals to overcome drawbacks of pure Bi such as brittleness, low thermal conductivity and poor wetting. The new ternary alloys have uniquely designed microstructures well suited for die attach materials and joining components exposed to high temperature and mechanically stressful environments where reliability is critical.  KEY ELEMENTS  Reliable operation of power electronics at temperatures ranging from 200- 250 ˚C  High melting temperature and meets the first-level interconnect challenges in electronic packaging  Ternary Bismuth alloys are lead free  Lower-cost alternative  APPLICATIONS  Die attach material for high temperature electronics, in-cluding SiC power devices and next generation LEDs  Joining material for high temperature electronics used in automotive, downhole drilling, and aerospace sectors   ADVANTAGES  Enables operation in temperatures ranging from 200-250 ˚C  Ternary Bi alloys are lead free  Good wetting on bonding surfaces such as nickel and copper  Good thermal and electrical conductivity  Innovative microstructures contributing to optimal mechanical properties for the power package  No phase transformation in cold ambient temperatures  Lower-cost alternative to expensive die attach materials such as hard solders (Au-Sn) and nano-silver  PATENTING  US patent pending (application no. 14/296,692)