Characterization of Material Damage and Microstructural Evolution Occurring in Lead Free Solders Subjected to Cyclic Loading

2018 ◽  
Author(s):  
Md Mahmudur Chowdhury ◽  
Mohd Aminul Hoque ◽  
Nianjun Fu ◽  
Jeffrey C. Suhling ◽  
Sa'd Hamasha ◽  
...  
Keyword(s):  
Cyclic Loading ◽  
Microstructural Evolution ◽  
Lead Free ◽  
Material Damage ◽  
Lead Free Solders

scholarly journals Phase equilibria investigation and alloys characterization in Sn-In-Ag system

2008 ◽  
Vol 62 (3) ◽  
pp. 148-152
Author(s):  
Aleksandra Milosavljevic ◽  
Dragana Zivkovic ◽  
Dragan Manasijevic ◽  
Nadezda Talijan ◽  
Aleksandar Grujic ◽  
...  
Keyword(s):  
Phase Equilibria ◽  
Xrd Analysis ◽  
Lead Free ◽  
Solder Alloys ◽  
Standard Lead ◽  
Free Solder ◽  
Dsc Method ◽  
Lead Free Solders ◽  
Thermocalc Software

Lead-free soldering has become very popular in the world recently, especially in electronics, because of high ecological demands in industry. Some of lead-free solder alloys are already used in electronic industry, but despite that investigations are still going in order to find suitable replacement for Pb-Sn standard solder. In this paper phase equilibria and characterization of Sn-In-Ag alloys in section In:Ag = 7:3 are investigated. The results of phase diagram calculation are obtained by ThermoCalc software, and characteristic temperatures by DSC method. The results of XRD analysis, optical microscopy, microhardness and electrical conductivity are also presented. These results are given in order to contribute the knowledge about lead-free solders, especially Sn-In-Ag solder alloys, which are potential candidates for replacement standard lead solders.

Thermal property, wettability and interfacial characterization of novel Sn–Zn–Bi–In alloys as low-temperature lead-free solders

2015 ◽  
Vol 84 ◽  
pp. 331-339 ◽  
Author(s):  
Jian-Chun Liu ◽  
Gong Zhang ◽  
Zheng-Hong Wang ◽  
Ju-Sheng Ma ◽  
Katsuaki Suganuma
Keyword(s):  
Low Temperature ◽  
Thermal Property ◽  
Lead Free ◽  
Lead Free Solders

The Effects of Aging of the Cyclic Stress-Strain and Fatigue Behaviors of Lead Free Solders

2013 ◽  
Author(s):  
Muhannad Mustafa ◽  
Jordan C. Roberts ◽  
Jeffrey C. Suhling ◽  
Pradeep Lall
Keyword(s):  
Cyclic Loading ◽  
Damage Accumulation ◽  
Solder Joints ◽  
Peak Load ◽  
Cyclic Stress ◽  
Lead Free ◽  
Failure Behavior ◽  
Stress Strain ◽  
Effects Of Aging ◽  
Lead Free Solders

Solder joints in electronic assemblies are typically subjected to thermal cycling, either in actual application or in accelerated life testing used for qualification. Mismatches in the thermal expansion coefficients of the assembly materials cause the solder joints to be subjected to cyclic (positive and negative) mechanical strains and stresses. This cyclic loading leads to thermomechanical fatigue damage that involves damage accumulation, crack initiation, crack propagation, and failure. In addition, the microstructure, mechanical response, and failure behavior of lead free solder joints in electronic assemblies are constantly evolving when exposed to isothermal aging and/or thermal cycling environments. While the effects of aging on solder constitutive behavior (stress-strain and creep) have been examined in some detail, there have been no prior studies on the effects of aging on solder failure and fatigue behavior. Aging leads to both grain and phase coarsening, and can cause recrystallization at Sn grain boundaries. Such changes are closely tied to the damage that occurs during cyclic mechanical loading. In this investigation, we have examined the effects of aging on the cyclic stress-strain behavior and fatigue life of lead free solders. Uniaxial solder test specimens (SAC105 and SAC305) have been prepared and subjected to cyclic stress/strain loading at different aging conditions. A four-parameter hyperbolic tangent empirical model has been used to fit the entire cyclic stress-strain curve and the hysteresis loop size (area) was calculated using definite integration for a given strain limit. This area represents the energy dissipated per cycle, which is correlated to the damage accumulation in the joint. Using the recorded cyclic stress-strain curves, the evolution of the solder hysteresis loops with aging have been characterized and empirically modeled. Similar to solder stress-strain and creep behavior, there is a strong effect of aging on the hysteresis loop size (and thus the rate of damage accumulation) in the solder specimens. Fatigue experiments were also performed, where the uniaxial specimens were subjected to cyclic loading over a particular strain range until failure. Fatigue failure in the experiments was defined to occur when there was a 50% peak load drop during mechanical cycling. Prior to testing, the specimens were aged (preconditioned) at 125 °C for various aging times, and then the samples were subjected to cyclic loading at room temperature (25 °C). It was found that aging decreased the mechanical fatigue life, and the effects of aging on the peak load drop have been studied. It has also been observed that degradations in the fatigue/failure behavior of the lead free solders with aging are highly accelerated for lower silver content alloys (e.g., SAC105). Various empirical failure criteria such as the Coffin-Manson model and the Morrow model have been used to fit the measured data, and the parameters in the models have been determined as a function of the aging conditions.

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