Nanocomposites and nanomaterials

Metal deposited nanoparticles as “bridge materials” for lead-free solder nanocomposites 
Yakymovych A.1, Yu. Plevachuk Yu. 2, P. Švec Sr P. 3, P. Švec P. 3,4, Sklyarchuk V.2
1Institute of Chemical Technologies and Analytics, TU Wien, Vienna, Austria
2Department of Metal Physics, Ivan Franko National University of Lviv, Lviv, Ukraine
3Institute of Physics, Slovak Academy of Sciences, Bratislava, Slovakia
4Centre of Excellence for Advanced Materials Application, Slovak Academy of Sciences, Bratislava, Slovakia

E-mail: yuriy.plevachuk@lnu.edu.ua

It is known that additions of metal or ceramic nanoparticles, as well as carbon nanotubes (CNTs) to the basic Sn-Ag-Cu matrix can improve significantly creep resistance and other important mechanical properties of lead-free solders as well as significantly decrease the total intermetallic thickness of solder-substrate joints.
In case of CNTs, it should be taken into account that practically all types of CNTs are completely not wettable by liquid metal alloys. This is the main reason that that inhibits the interaction betwen CNTs and the solder melt during the reflow process. In the course of soldering, most of carbides, oxides, and carbon-based ceramics can be pushed out of the molten solder during the reflowing process connected with the nonwettability, which is due to differences between some thermophysical properties such as, first of all, density and surface tension. To solve this problem, the surfaces of these carbon materials can be modified by the secondary metal phases to improve adoption with the solder matrixes before implementation.
The carbon nanotubes were added to the basic ternary metal Sn-Ag-Cu matrix. The conventional DC Diode Sputter Coater was used for the purpose of coating of CNTs by Ni and Co. Sputtered nanosized Ni and Co layers covered the surface of used nanoparticles, enhancing their uniform distribution in the matrix of the solder and forming a “bridge” substance, which reacts with the matrix of the SAC alloy and forms the layer of the intermetallic compounds in the course of the soldering procedure. The influence of different pure CNTs and CNTs coated by metals on structure and structure-sensitive properties of the Sn-Ag-Cu nanocomposite alloys was evaluated.

Support of the projects APVV-SK-UA-21-0076, VEGA 2/0144/21, UA-SK Project No. М/68-2022 and the FWF Project P 34894 is gratefully acknowledged.