Effect of addition of Cu on the properties of eutectic Sn-Bi solder alloy

Abstract

The present work reports the effect of Cu addition on the melting point, hardness and electrical resistivity of Sn-57 wt.% Bi eutectic solder alloy. Both binary eutectic Sn-57 wt.% Bi and ternary Sn-(57-x)Bi-xCu (x = 0.1, 0.3, 0.5, 0.7 and 1 wt.%) alloys containing various amounts of Cu were developed by melting casting route. The microstructure of the various solder alloys was analyzed using an optical microscope and a SEM. The variation in melting point, hardness and electrical resistivity of the Sn-Bi eutectic solder alloys with the addition of Cu was determined. The melting point of the eutectic Sn-Bi solder alloy was found to decrease up to the addition of 0.7 wt.% Cu. However, further addition of Cu led to an increase in the melting point of the alloy. Addition of Cu led to an increase in the hardness of the eutectic Sn-Bi solder alloy whereas the electrical resistivity of this alloy was found to increase up to the addition of 0.7 wt.% of Cu beyond which a decrease in the electrical resistivity was observed. A change in the microstructure of the solder alloy was observed when it was reheated above the melting temperature.Keywords: Sn-Bi-Cu; lead-free solder alloys; melting point; DSC/TGA Effect of addition of Cu on the properties of eutectic Sn-Bi solder alloy 213 is 51 MPa to 75 MPa. Its density is 5.765 g/cc and its modulus of elasticity is 41.6 GPa. It has a thermal conductivity of 66.8 W/(m·K) and coefficient of thermal expansion of 0.000022 K −1 [7,8].

Effects of alloying element on mechanical properties of Sn-Bi solder alloys: a review

“…% of Ni and Zn in Sn-58Bi solder resulted in 395 MPa (Yang et al, 2016b) and 750 MPa of Sn and 600 MPa of Bi (Zhou et al, 2018) There have been a few studies on the hardness of Sn-Bi alloys containing the same alloying element, but at different weight percentages. Alam et al (2019) reported that alloying Cu in Sn-57Bi increased the microhardness value linearly in proportion to the increase in wt. % of copper from 0.1 to 1.0.…”

“…The hardness values of Sn-Bi solder systems alloyed with 0.5 wt. % of Ni (Yang et al , 2016b), Cu (Jayesh and Elias, 2020; Alam et al , 2019) and Al (Yang et al , 2019b) were studied. All studies used the same solder preparation technique except Alam, S. N. et al , and Yang, L. et al stated that the presence of 0.5 wt.…”

“…Tensile and yield strengths are directly proportional to the hardness value in a linear relationship, which clearly indicates that when hardness increases, the ultimate tensile and yield strength would correspondingly increase (Yang et al , 2016b). The hardness of a solder alloy can also be enhanced by the formation of brittle and hard intermetallic compounds (Alam et al , 2019). The durability and wear behavior of the solder can also be measured by its hardness properties (Yang et al , 2019b).…”

“…Yang et al (2016b); Alam et al (2019), Zhou et al (2018); and Singh and Durairaj (2020) studied the hardness of Sn-Bi solder systems alloyed with 1.0 wt. % of Ni, Cu, Zn, Al and Al 2 O 3 , respectively.…”

“…Yang et al (2016b);Alam et al (2019),Zhou et al (2018); andSingh and Durairaj (2020) studied the hardness of Sn-Bi solder systems alloyed with 1.0 wt. % of Ni, Cu, Zn, Al and Al 2 O 3 , respectively.Yang, L. et al and Zhou, S. et al conducted nanoindentation tests, whereas the others conducted Vickers microhardness testing to measure the hardness of the solder composition.…”