Effects of Mn nanoparticle addition on wettability, microstructure and microhardness of low-Ag Sn-0.3Ag-0.7Cu-xMn(np) composite solders

Abstract

Purpose The purpose of this paper is to investigate of the effects of Mn nanoparticle addition on the wettability, microstructure and microhardness of SAC0307-xMn(np) (SAC: Sn–Ag–Cu; x = 0, 0.02, 0.05, 0.1 and 0.3 Wt.%) composite solders. Design/methodology/approach The SAC0307-xMn(np) composite solders were prepared by mechanically mixing different weight percentages of Mn nanopowders into the SAC0307 solder paste with rosin flux. In this study, the wettability of the solders was studied using contact angle and spread ratio methods. Afterward, the microstructure of the solders was investigated using scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffractometry. Moreover, the microhardness of the solders was studied. Findings The wetting process of SAC0307-xMn(np) composite solders was found to experience four stages. Adding a small amount of Mn nanoparticles (x = 0.05 Wt.%) could improve the wettability compared to Mn-free solder. Beyond this level, the wettability deteriorated. The addition of Mn nanoparticles significantly refined the size and spacing of Ag3Sn grains in the solder matrix. When 0.1 Wt.% Mn nanoparticles was added, both the average size of the Ag3Sn grains and the spacing between the Ag3Sn grains decreased significantly and approached minimum values. Beyond this amount, the size and spacing between Ag3Sn grains increased slightly but remained smaller than those in the Mn-free solder matrix. The refined Ag3Sn grains increased the microhardness of the Mn-containing composite solders by 6-25 per cent, in good agreement with the prediction of the classic theory of dispersion strengthening. Originality/value The paper demonstrates that Mn nanoparticle addition could improve the SAC0307-xMn(np) solder wettability and reduce the grain size and spacing between Ag3Sn grains. The enhancement of the solder microhardness shows good correlation with the microstructure.

Investigation of the Microstructure of Mn-doped Tin-Silver-Copper Solder Alloys Solidified with Different Cooling Rates

“…Thus, these reinforcing nanoparticles can enhance the quality and reliability properties of solder joints for ultra-fine package assembly.Due to the moderate price and the non-toxicity, the manganese is considered as an ideal dopant for the SAC solder alloys. Mn reported to have a grain refinement effect on the SAC solder alloys both in nanoparticle [9] and in micralloyed [10] form. At soldering temperature and below that the solubility of Mn in the Sn base solder alloy is relatively low; so even at very low concentration, Mn containing micro precipitation might appear inside the solder bulk which may act as a crystallization centre for the solidification of the SAC alloy.…”

Investigation of the Mechanical Properties of Mn-Alloyed Tin-Silver-Copper Solder Solidified with Different Cooling Rates

“…Because of the reasonable price and harmless nature, manganese can be an optimal alloying element for the SAC solder alloys. Mn reportedly refines the grain structure in the SAC solder alloys when added either in the nanoparticle [ 22 ] or in the alloyed form [ 23 ]. Both at soldering temperature and below that, the solubility of Mn in the Sn solder alloy is low.…”

“…Lin et al measured the elongation and Young’s modulus of SAC solders alloyed with manganese and titanium [ 23 ] and showed an increase in the elongation and a decrease in the Young’s modulus. Manganese was also utilized in nanoparticle form [ 22 ]. Tang et al found that the optimal weight percentage of manganese nanoparticles is 0.05 wt.% to enhance the wettability of SAC alloys.…”

Effect of CoSn3 nanocrystals on Sn3Ag plating for electronic packaging

“…Composite lead-free solders containing micro-, and nanoparticles have been extensively studied [1][2][3][4][5]. Due to grain-boundary resistance, these particles can inhibit the coarsening of the brazing material organization, especially the Cu 6 Sn 5 , Ag3Sn intermetallic compounds and β-Sn phases.…”

“…The addition of a small amount of Bi to Sn-1.5Ag-0.7Cu solders reduces supercooling, refines the microstructure, reduces the nucleation rate of intermetallic compounds (IMCs), and improves creep resistance and fracture life solders. Cheng et al reported that the addition of low levels of Ni to Sn-1.0Ag-0.5Cu solders enhanced the growth of Cu 6 Sn 5 IMCs and inhibited the growth of Cu3Sn IMCs during solid-state aging [4]. Presently, two widely employed methods for fabricating composite solders with added reinforcement materials are the mechanical blending method and the powder metallurgy method.…”