High-Bi Alloys


Solder Alloys


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 increases 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 Euro-pean 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 designed 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 dominate 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 wet-ting. 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.




 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




 Die attach material for high temperature electronics, including SiC power devices and next generation LEDs


 Joining material for high temperature electronics used in automotive, downhole drilling, and aerospace sectors




 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 ex-pensive die attach materials such as hard solders (Au-Sn) and nano-silver





Professor-Inventor Dr. Junghyun Cho is a Professor of Mechanical Engineering and of Mate-rials Science and Engineering, and the Director of the Advanced Materials and Mechanics Laboratory at Binghamton University. His research program focuses on materials systems, including thin films, coatings, and solders useful in electronics and MEMS packaging, as well as the microstructure design, characterization and reliability of various ceramic, metallic, and polymeric materials.



Patent Information:
For Information, Contact:
Scott Hancock
Director, IP Management and Licensing
Binghamton University
(607) 777-5874
Junghyun Cho
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