Relationship between Nanomechanical Responses of Interfacial Intermetallic Compound Layers and Impact Reliability of Solder Joints

Abstract

This study aims to evaluate solder joint reliability under high speed impact tests using nanoindentation properties of intermetallic compounds (IMCs) at the joint interface. Sn–Ag based solder joints with different kinds of interfacial IMCs were obtained through the design of solder alloy/substrate material combinations. Nanoindentation was applied to investigate the mechanical properties of IMCs, including hardness, Young’s modulus, work hardening exponent, yield strength, and plastic ability. Experimental results suggest that nanoindentation responses of IMCs at joint interface definitely dominates joint impact performance. The greater the plastic ability the interfacial IMC exhibits, the superior impact energy the solder joints possess. The concept of mechanical and geometrical discontinuities was also proposed to explain brittle fracture of the solder joints with bi-layer interfacial IMCs subject to impact load.

Microstructural and Mechanical Characterization of Cu/Sn Slid Bonding Utilizing Co as Contact Metallization Layer

“…The measured Er and Ei for Cu 6 Sn 5 in this study were below the average reported values in the literature (some reported values in the literature are listed in Table 1). However, it has to be considered that the mechanical properties of the Cu 3 Sn and Cu 6 Sn 5 strongly depend on the crystal orientation [7,12,14,65]. Besides, the strain rate can considerably affect the Young's modulus, elastic modulus and hardness values [93,94].…”

“…However, the hardness value for the high-Co content (10 at%) Cu6Sn5 IMC is much larger than pure Cu 6 Sn 5 . Since E/H implies plasticity of the IMCs, higher E/H better plasticity and subsequently higher joint reliability, [7,95] it is important to consider the E/H values for IMCs formed in the joint area. The E/H values for Cu 6 Sn 5 , (Cu,2at%Co) 6 Sn 5 , and (Cu,10at%Co) 6 Sn 5 were calculated to be 17, 20, and 17, respectively in this work.…”

“…The reliability performance of SLID bonding significantly depends on the bond quality and mechanical properties of the IMCs formed at the joint area, as different type of defects, such as cracks and voids, can seriously degrade the mechanical properties of the brittle IMCs. Therefore, it is of utmost importance to clarify the bond quality and microstructural evolution and mechanical properties of the intermetallic compounds formed in the bonding area [5][6][7].…”

“…According to Milman et al, the fraction of plastic deformation in the total deformation during indentation (δ H ) can be used as a plasticity characteristic of brittle materials [34]. δ H can be determined by the ratio of Young's modulus to hardness (high E/H value implies better plasticity for IMCs, while low E/H indicates brittleness) [7], [34][35][36]. Hence, Cu 3 Sn shows better plasticity compared to Cu 6 Sn 5 , as it possesses similar hardness to and a higher Young's modulus than Cu 6 Sn 5 .…”

The Mechanical Properties and Elastic Anisotropy of η′-Cu6Sn5 and Cu3Sn Intermetallic Compounds

“…Domestic and foreign research both present studies on the mechanical properties of Cu 6 Sn 5 and Cu 3 Sn. The Young's modulus (E) and hardness (H) of Cu 3 Sn and Cu 6 Sn 5 were measured by nanoindentation experiments [10][11][12][13]. Ghosh et al [14] identified the values of E, shear modulus (G), bulk modulus (B), and Poisson's ratio (ν) using the pulse-echo method.…”