Comparison of Sn2.8Ag20In and Sn10Bi10In solders for intermediate-step soldering

Abstract

We chose Sn-2.8Ag-20In and Sn-10Bi-10In (numbers are in weight percentages unless specified otherwise) as Pb-free solder materials for intermediate-step soldering. We then investigated how the two solders reacted with the under bump metallurgy (UBM) of Au/Ni (Au: 1.5 mm and Ni: 3 mm) at 210°C, 220°C, 230°C, and 240°C for up to 4 min. All of the Au UBM was dissolved into the solder matrix as soon as the interfacial reaction started. The reaction formed Au(In,Sn) 2 in the case of SnAgIn, and it formed Au(Sn,In) 4 and Au(In,Sn) 2 in the case of SnBiIn. The formation mechanism of the intermetallic phases is explained thermodynamically. The exposed Ni layer reacted with the solder and formed Ni 28 Sn 55 In 17 in case of SnAgIn, and formed Ni 3 (Sn,In) 4 in case of SnBiIn, at the solder joint interface. Under the same soldering conditions, the Ni 3 (Sn,In) 4 layer in the SnBiIn/UBM is thicker than the Ni 28 Sn 55 In 17 layer in the SnAgIn/UBM. Because of the thicker intermetallic compound layer, the SnBiIn solder joint has weaker shear strength than the SnAgIn solder joint.

The evolution of microstructure and microhardness of Sn–Ag and Sn–Cu solders during high temperature aging

“…The majority of Pb-free solders are Sn-based alloys with minor alloying elements of Ag, Cu, Co, In, Ni, Zn and others [1][2][3][4][5]. The most popular Pb-free solders include near-eutectic Sn-Ag-Cu, Sn-Ag and Sn-Cu alloys.…”

The Crystal Orientation of β-Sn Grains in Sn-Ag and Sn-Cu Solders Affected by Their Interfacial Reactions with Cu and Ni(P) Under Bump Metallurgy

“…[1][2][3][4] To improve the reliability of Pb-free solder joints, it has recently been proposed to reduce the Ag and Cu content as well as to add minor alloying elements such as Zn, In, Bi, Co, and Ni in Sn-based solders. [5][6][7][8][9][10] Since most Pb-free solders have a composition of more than 90% Sn, the physical, chemical, and electrical properties of Pb-free solders are predominantly affected by the properties of the b-Sn crystal. The properties of Sn are highly anisotropic, owing to the unique crystal structure of b-Sn, with a lattice structure of body-centered tetragonal (a 5.83 Å , c 3.18 Å ).…”

Investigation of the Local Mechanical Properties of the SAC Solder Joint with AFM

“…The Sn-Ag-Cu (SAC) alloys are the most commonly used lead-free substitute solders. The reliability of the solder-joints is heavily influenced by the characteristics of the formed intermetallic components (IMCs) during the soldering [1]. The following parts (phases) can be distinguished: the Cu substrate, the intermetallic layer (IML) which formed at the interface of the solder paste and the copper, the Ag 3 Sn islands, which grows up in the solder and the Cu 6 Sn 5 islands which spall from the IML and migrate into the Sn-rich phase [2,3].…”