Guang Zeng

Creep behavior of SnAgCu solders with rare earth Ce doping

Abstract Extensive testing was carried out to study the effects of rare earth Ce doping on the properties of SnAgCu solder alloys. The addition of 0.03% (mass fraction) rare earth Ce into SnAgCu solder may improve its mechanical properties, but slightly lower its melting temperature. The tensile creep behavior of bulk SnAgCuCe solders was reported and compared with SnAgCu solders. It is found that SnAgCuCe solders show higher creep resistance than SnAgCu alloys. Moreover, Dorn model and Garofalo model are successfully used to describe the creep behavior of SnAgCu and SnAgCuCe alloys. The parameters of the two creep constitutive equations for SnAgCu and SnAgCuCe solders are determined from separated constitutive relations and experimental results. Nonlinear least-squares fitting is selected to determine the model constants. The experimental data of the stress-creep strain rate curves are in good agreement with the theoretical ones.

Microstructure and creep properties of Sn-Ag-Cu lead-free solders bearing minor amounts of the rare earth cerium

Purpose – The purpose of this paper is to investigate the effects of minor addition of the rare earth (RE) element cerium, Ce, on the microstructures and creep properties of Sn‐Ag‐Cu solder alloys.Design/methodology/approach – The pure Sn, Sn‐Cu alloy, Sn‐Ag alloy and Cu‐Ce alloy were used as raw materials. Sn‐Ag‐Cu alloys with different contents of RE Ce were chosen to compare with Sn‐Ag‐Cu. The raw materials of Sn, Sn‐Cu alloy, Sn‐Ag alloy, Cu‐Ce alloy were melted in a ceramic crucible, and were melted at 550°C±1°C for 40 minutes. To homogenize the solder alloy, mechanical stirring was performed every ten minutes using a glass rod. During the melting, KC1+LiCI (1.3:1), were used over the surface of liquid solder to prevent oxidation. The melted solder was chill cast into a rod.Findings – It is found that the microstructure exhibits smaller grains and the Ag3Sn/Cu6Sn5 intermetallic compound (IMC) phases are modified in matrix with the addition of Ce. In particular, the addition of 0.03u2009wt.% Ce to the Sn‐...

Determination of Anand parameters for SnAgCuCe solder

A unified viscoplastic constitutive model, Anand equations, was used to represent the inelastic deformation behavior for Sn3.8Ag0.7Cu/Sn3.8Ag0.7 Cu0.03Ce solders in surface mount technology. The Anand parameters of the constitutive equations for the SnAgCu and SnAgCuCe solders were determined from separated constitutive relations and experimental results. Non-linear least-squares fitting was selected to determine the model constants. Comparisons were then made with experimental measurements of the stress–inelastic strain curves: excellent agreement was found. The model accurately predicted the overall trend of steady-state stress–strain behavior of SnAgCu and SnAgCuCe solders for the temperature ranges from −55 to 125u2009°C and for the strain rate range from 1%u2009s−1 to 0.01%u2009s−1. It is concluded that the Anand model can be applied to represent the inelastic deformation behavior of solders at high homologous temperatures and can be recommended for finite element simulation of the stress–strain response of lead-free soldered joints. Based on the Anand model, the investigations of thermo-mechanical behavior of SnAgCu and SnAgCuCe soldered joints in fine pitch quad flat package by the finite element code have been done under thermal cyclic loading, and it is found that the reliability of the SnAgCuCe soldered joints is better than that of the SnAgCu soldered joints.

Reliability evaluation of SnAgCu/SnAgCuCe solder joints based on finite element simulation and experiments

Purpose – The purpose of this paper is to numerically evaluate the reliability of SnAgCuCe solder joints compared with that of SnAgCu. A trace amount of the rare earth (RE) element Ce was added into SnAgCu solder in order to improve the reliability of lead‐free solder joints, which was evaluated based on finite element simulation and experiments.Design/methodology/approach – A finite element method and an Anand constitutive model were employed to analyze the reliability of SnAgCuCe and SnAgCu solder joints in fine pitch quad flat packages under thermal cycling. The mechanical properties and reliability of solder joints were characterized by using thermal fatigue and creep tests, while the microstructure of the solder alloy and SnAgCu/SnAgCuCe solder joints were also investigated in the experimental procedure.Findings – The simulation results indicated that SnAgCuCe solder joints had better reliability than SnAgCu. In addition, the experimental results accorded well with those of simulation, the thermal fa...