Joint strength and interfacial microstructure between Sn–Ag–Cu and Sn–Zn–Bi solders and Cu substrate

Abstract

In the present research, in order to fundamentally investigate the strength and interfacial microstructure of the joints between Sn-3.5Ag-0.7Cu (SAC) and Sn-8Zn-3Bi (SZB) solders and Cu, examinations using the standardized solder joint specimen for measuring the shear strength were performed. The effects of the addition of Ag, Bi and Pb to the solders, which are the ingredients of possible lead plating materials of quad plat package, solder layer thickness and aging treatments ranging from 358 to 423 K were investigated. The SAC base solder joints, whose strength hardly degraded after aging, were more reliable than the SZB base solder joints. Since no detrimental effect of the Bi or Pb addition was recognized, the lead plating materials are found to have no significant effect on the strength of the SAC solder joints. Although the SZB base solder joints had higher strength than the SAC base solder joints in as-soldered condition, a significant degradation of the joint strength occurred after aging. In the case of thinner solder layer of 20 mm, the Cu 6 Sn 5 layer that formed at both the solder/Cu 5 Zn 8 and Cu 5 Zn 8 /Cu interfaces after aging caused the fracture of the solder joints and resulted in the degradation of the joint strength. In the case of thicker solder layer of 100 mm, the Cu 5 Zn 8 interfacial layer continuously grew during aging, which caused the fracture of the solder joints and resulted in the decrease in the joint strength. As for the effect of the addition elements, while Pb addition caused a marked degradation of the joint strength, Ag addition and Bi addition had no detrimental effect on the strength of the solder joints. In particular, the joint with the Ag addition solder had the better strength in the case of thinner solder layer. Thus, as for lead plating for the SZB solder, Sn-Pb should be avoided and Sn-Bi or Sn-Ag as Pb-free plating has no detrimental effect on the joint strength. In particular, Sn-Ag plating is preferable in the viewpoint of the joint strength. q

Reinforcement of Ag nanoparticle paste with nanowires for low temperature pressureless bonding

“…The measured strength of joints is the tensile shear strength due to the applied shear stress during the tensile testing, because two Cu wires were not coaxial. It was estimated by dividing the highest failure force value by the bonding area [24,50,51], r = F max /A (N/mm 2 or MPa). The fracture area of samples was difficult to measure Sintered paste with different Ag NW volume additions f 0 vol%, g 10 vol% and i 30 vol% after sintering at 150°C for 1 h. Inset low magnification image h and j are corresponding to Ag NP/10NW and Ag NP/30NW pastes due to the unsymmetrical geometry of fracture region.…”

The effect of crosshead speed on the joint strength between Sn-Zn-Bi lead-free solders and Cu substrate

“…So, the strength of the solder joints is important for this role [4]. There are not many studies reported on the mechanical properties of the joints by Sn-Zn solders [5,6,7], and a few stress-strain curves have been reported for the solders [5]. The mechanical properties of the substrate/solder joint are greatly influenced by the interface reaction products between them.…”

Effects of small additions of Ag, Al, and Ga on the structure and properties of the Sn–9Zn eutectic alloy

“…However, the tendency of oxidation, and poor wetting ability of this alloy system confine its application [5,6]. In recent years, to overcome the shortfall of Sn-9Zn, some authors have tried to add a third element, such as In [7], Bi [8][9][10], Al [11][12][13][14][15], Ag [16][17][18], and Ce/La [19][20][21] to the Sn-Zn binary system to improve the melting temperature, wettability, oxidation resistance, corrosion, and mechanical properties of the alloy.…”