This study employed a mechanical mixing method to successfully incorporate Mg particles into the lead-free solder Sn58Bi

resulting in a novel composite solder Sn58Bi-xMg (x=0

0.2

0.4

0.6

0.8

1.0). In-depth observation and investigation were conducted regarding the microstructure of the solder joints formed by these composite solders on Cu substrates and the growth of intermetallic compounds (IMCs) at the interfaces. The experimental results indicated that the introduction of Mg particles played a role in refining the microstructure of the solder joints. Simultaneously

the uniformly dispersed Mg particles in the matrix also suppressed the precipitation of Bi phases

contributing to the enhancement of solder refinement and overall strength. With the increase in Mg particle content

the thickness of IMC gradually decreased. Particularly

when the addition of Mg particles was 0.4 wt.%

the IMC thickness reached its minimum at only 3.03 μm. It is noteworthy that when the Mg particle content exceeded 0.4 wt.%

the larger-sized Mg particles were prone to aggregation and oxidation

leading to a less-than-satisfactory strengthening effect. Through observations of the growth of IMC grains

it was verified that the introduction of Mg particles successfully refined the IMC grains

achieving a fine-grain strengthening effect and improving the overall strength of the solder joints. Compared to solder joints without added Mg particles

the shear strength of Sn58Bi0.4Mg solder joints increased by 30%. Additionally

the appearance of ductile dimples on the fracture surface indicated a significant improvement in the ductility of the solder joints. These research findings provide new insights and methods for the improvement of soldering technology.