Microstructure and mechanical properties of Cu joints soldered with a Sn-based composite solder, reinforced by metal foam

Abstract

In this study, Ni foam, Cu coated Ni foam and Cu-Ni alloy foams were used as strengthening phases for pure Sn solder. Cu-Cu joints were fabricated by soldering with these Sn-based composite solders at 260 °C for different times. The tensile strength of pure Sn solder was improved significantly by the addition of metal foams, and the Cu-Ni alloy/Sn composite solder exhibited the highest tensile strength of 50.32 MPa. The skeleton networks of the foams were gradually dissolved into the soldering seam with increasing soldering time, accompanied by the massive formation of (Cu,Ni) 6 Sn 5 phase in the joint. The dissolution rates of Ni foam, Cu coated Ni foam and Cu-Ni alloy foams into the Sn matrix increased successively during soldering. An increased dissolution rate of the metal foam leads to an increase in the Ni content in the soldering seam, which was found to be beneficial in refining the (Cu,Ni) 6 Sn 5 phase and inhibiting the formation of the Cu 3 Sn IMC layer on the Cu substrate surface. The average shear strength of the Cu joints was improved with increasing soldering time, and a shear strength of 2 61.2 MPa was obtained for Cu joints soldered with Cu-Ni alloy/Sn composite solder for 60 min.

Morphologies of intermetallic compound phases in Sn-Cu and Sn-Co peritectic alloys during directional solidification

“…Among them, the Sn-Cu and Sn-Co alloys have shown wide application. As one of the most popular lead-free solders, Sn-Cu alloys are commonly applied in the electronics industry owing to their excellent weldability and non-toxic property [23][24][25][26][27][28][29] . Investigation on the Sn-Cu solders of high Sn content is of great interest since the operating temperature of solders can be enhanced by increasing the content of Cu.…”

Microstructure evolution and grain refinement of ultrasonic-assisted soldering joint by using Ni foam reinforced Sn composite solder

“…Our current research included fabricating and using Ni foam reinforced Sn composite solder foils to solder Cu alloy and Al alloy, and it revealed that the use of Ni-skeletons and Ni-Sn reactants significantly increased the strengths of joint [6] , [7] . The analysis results show that continuous reticular structure inhibits the aggregation of the reinforcing phase and improves the combination between Sn solder and reinforcing phases [8] .…”

Microstructure transformation and mechanical properties of Al alloy joints soldered with Ni-Cu foam/Sn-3.0Ag-0.5Cu (SAC305) composite solder

“…For example, Zhang [21] fabricated the Cu-foam reinforced Sn-Bi solder and found the Cu foam not only refined the solder structure but also enhanced the mechanical properties of the Sn-Bi solder. The Ni foam-Sn/Cu joints were fabricated in our previous work [22][23][24]. The Sn solder was quickly consumed by the metallurgical reactions between Sn solder and Ni foam, forming a high melting point joint containing (Ni,Cu)3Sn4, (Cu,Ni)6Sn5 and Ni skeleton.…”