Top: Colorized scanning electron micrograph (SEM) shows a "whisker" on the surface of a tin-copper alloy. The image was taken 176 days after the alloy was electroplated onto a tiny cantilever beam.
Bottom: Micrograph of a "hillock" on an electrodeposited surface of pure tin (10 times the magnification of top image).
Image credit:NIST/Boettinger et al., Acta Materialia,5033-5050
Environmental groups around the world have been campaigning for years to replace lead-containing solders and protective layers on electronic components with non-hazardous metals and alloys. In response, the European Union (EU) will ban the use of lead (and five other hazardous substances) in all electrical and electronic equipment sold in EU nations starting in July 2006. U.S. manufacturers must comply with this requirement in order to market their products overseas.
However, pure electroplated tin and lead-free tin alloys tend to spontaneously grow metallic whiskers (thin filament-like structures often several millimeters long) during service. These defects can lead to electrical shorts and failures across component leads and connectors.
Whiskers--and more benign raised formations called hillocks--are believed to be a metal’s means of relieving stress generated by the electroplating process, so National Institute of Standards and Technology (NIST) researchers--working with the International Electronics Manufacturing Initiative (iNEMI)--have been trying to identify the origins of such stresses and better understand the resulting mechanisms for whisker and hillock growth. In a recent paper in Acta Materialia,* they reported that the surfaces of tin-copper deposits developed extremely long whiskers while pure tin deposits (the simplest lead-free plating finish) only produced hillocks. By comparison, the soon-to-be-banned tin-lead deposits did not form either type of deformity (a characteristic known since the 1960s).
Michael E. Newman | EurekAlert!
Engineers develop smart material that changes stiffness when twisted or bent
15.02.2018 | Iowa State University
Breaking local symmetry: Why water freezes but silica forms a glass
14.02.2018 | Institute of Industrial Science, The University of Tokyo
Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale
Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...
For photographers and scientists, lenses are lifesavers. They reflect and refract light, making possible the imaging systems that drive discovery through the microscope and preserve history through cameras.
But today's glass-based lenses are bulky and resist miniaturization. Next-generation technologies, such as ultrathin cameras or tiny microscopes, require...
Scientists from the University of Zurich have succeeded for the first time in tracking individual stem cells and their neuronal progeny over months within the intact adult brain. This study sheds light on how new neurons are produced throughout life.
The generation of new nerve cells was once thought to taper off at the end of embryonic development. However, recent research has shown that the adult brain...
Theoretical physicists propose to use negative interference to control heat flow in quantum devices. Study published in Physical Review Letters
Quantum computer parts are sensitive and need to be cooled to very low temperatures. Their tiny size makes them particularly susceptible to a temperature...
Let’s say the armrest is broken in your vintage car. As things stand, you would need a lot of luck and persistence to find the right spare part. But in the world of Industrie 4.0 and production with batch sizes of one, you can simply scan the armrest and print it out. This is made possible by the first ever 3D scanner capable of working autonomously and in real time. The autonomous scanning system will be on display at the Hannover Messe Preview on February 6 and at the Hannover Messe proper from April 23 to 27, 2018 (Hall 6, Booth A30).
Part of the charm of vintage cars is that they stopped making them long ago, so it is special when you do see one out on the roads. If something breaks or...
15.02.2018 | Event News
13.02.2018 | Event News
12.02.2018 | Event News
16.02.2018 | Information Technology
16.02.2018 | Health and Medicine
16.02.2018 | Physics and Astronomy