scholarly journals Experimental SAC305 Shear Stress–Strain Hysteresis Loop Construction Using Hall's One-Dimensional Model Based on Strain Gages Measurements

2019 ◽  
Vol 141 (2) ◽  
Author(s):  
J.-B. Libot ◽  
J. Alexis ◽  
O. Dalverny ◽  
L. Arnaud ◽  
P. Milesi ◽  
...  
Keyword(s):  
Shear Stress ◽  
Energy Density ◽  
Hysteresis Loop ◽  
Strain Energy Density ◽  
Strain Energy ◽  
Solder Joints ◽  
Strain Gages ◽  
Sac305 Solder ◽  
Stress Strain ◽  
Temperature Cycles

Temperature-induced solder joint fatigue is a main reliability concern for aerospace and military industries whose electronic equipment used in the field is required to remain functional under harsh loadings. Due to the RoHS directive, which eventually will prevent lead from being utilized in electronic systems, there is a need for a better understanding of lead-free thermomechanical behavior when subjected to temperature variations. Characterizing solder joints properties remains a challenge as viscoplastic behavior during thermal cycling is complex, and their small dimensions prevent direct measurements from being performed. This paper reports the experimentation based on strain gage measurements, allowing the construction of the shear stress–strain hysteresis loop corresponding to Sn3.0Ag0.5Cu (SAC305) solder joints behavior during thermomechanical loading. This methodology, initially developed in 1984 by Hall for Sn60Pb40 interconnects, allows the measurement of the strain energy density dissipated during temperature cycles. Custom daisy-chained 76 I/O ceramic ball grid array (CBGA76) components were designed and assembled on flame retardant (FR-4) multilayered printed circuit boards (PCB). Four strain gages were specifically placed at the center of the assembly on top and bottom faces of both PCB and CBGA76 component. The assembly was subjected to temperature cycles and the SAC305 solder joints shear stress–strain hysteresis loop was plotted. The correlation between the measured strain energy density and measured lifetime corresponds to one point of the energy based fatigue curve for SAC305 solder joints. The hysteresis loop also provides the necessary data to derive SAC305 solder joints constitutive laws.

Critical Accumulated Strain Energy (Case) Failure Criterion for Thermal Cycling Fatigue of Solder Joints

1994 ◽  
Vol 116 (3) ◽  
pp. 163-170 ◽  
Author(s):  
Tsung-Yu Pan
Keyword(s):  
Fatigue Life ◽  
Energy Density ◽  
Thermal Cycling ◽  
Creep Strain ◽  
Failure Criterion ◽  
Strain Energy Density ◽  
Strain Energy ◽  
Solder Joints ◽  
Field Service ◽  
Accumulated Strain

In the automotive and computer industries, a perennial challenge has been to design an adequate and efficient accelerated thermal cycling test which would correspond to field service conditions. Failures, induced in both thermal cycle testing and field service, are characterized by thermal fatigue behavior. Several fatigue models have been proposed, none of these models take into account all of the many parameters of the test or service environment. In thermal cycling, for example, the temperature range, ramp rate, hold time, and stepped heating and cooling are known to influence the number of cycles to failure. In this study, a critical accumulated strain energy (CASE) failure criterion is proposed to correlate the fatigue life to both the plastic and creep strain energies, which accumulate in solder joints during the thermal cycling. This criterion suggests that solder joints fail as the strain energy accumulates and reaches a critical value. By using finite element analysis with a “ladder” procedure, both time-independent plastic strain energy and time-dependent creep strain energy are quantified. These are related to fatigue life by the equation: C = N*f (Ep + 0.13Ec), where C is the critical strain energy density, Nf is the fatigue life, Ep and Ec are plastic and creep strain energy density accumulation per cycle, respectively, for the eutectic Sn-Pb solders. By analyzing Hall and Sherry’s thermal cycling data (Hall and Sherry, 1986), it is found that creep is the predominant factor in deciding fatigue life. Creep accounts for 51 to 97 percent of the total accumulated strain energy, depending on the cycling profiles. This criterion is used to simulate crack propagation in a solder joint by analyzing the strain energy in small “domains” within the joint.

Fatigue Life Law Based on Inelastic Strain Energy Density of Solder Alloys and its Simple Prediction Method

2020 ◽  
Author(s):  
Tomoya Fumikura ◽  
Mitsuaki Kato ◽  
Takahiro Omori
Keyword(s):  
Fatigue Life ◽  
Energy Density ◽  
Fatigue Test ◽  
Strain Energy Density ◽  
Strain Energy ◽  
Prediction Method ◽  
Strain Range ◽  
Inelastic Strain ◽  
Stress Strain ◽  
Wide Range

Abstract In recent years, a fatigue life law based on inelastic strain energy density as proposed by Morrow has been applied to solder materials. In this study, the effectiveness of the fatigue life law based on inelastic strain energy density was compared with the conventional law based on inelastic strain range. First, the fatigue properties of Sn-Ag-Cu solder alloy were investigated by a torsional fatigue test with strain control. It was found that the stress–strain hysteresis loop arising from inelastic deformation occurred even under a low strain load with a fatigue life of about 1 million cycles. Therefore, as an extension of the low-cycle fatigue test, evaluation was performed using inelastic strain range and inelastic strain energy density. Experimental results show that when fatigue life was evaluated using inelastic strain energy density, a single power law was found over a wide range from the low-cycle region to the high-cycle region, and the validity of the fatigue life law based on inelastic strain energy density was confirmed. Next, a simple prediction method for the fatigue life law based on inelastic strain energy density was examined, taking the physical background into account. Two material constants of the fatigue life law based on the inelastic strain energy density were estimated from the stress–strain curve for a monotonic load and shown to be close to the actual fatigue test results.

scholarly journals Creep-Fatigue Behaviours of Sn-Ag-Cu Solder Joints in Microelectronics Applications

2021 ◽  
Author(s):  
Joshua A. Depiver ◽  
Sabuj Mallik ◽  
Yiling Lu ◽  
Emeka H. Amalu
Keyword(s):  
Energy Density ◽  
Thermal Cycling ◽  
Strain Rate ◽  
Deformation Rate ◽  
Strain Energy Density ◽  
Strain Energy ◽  
Solder Joints ◽  
Creep Fatigue ◽  
Accelerated Thermal Cycling ◽  
Isothermal Ageing

Electronic manufacturing is one of the dynamic industries in the world in terms of leading technological advancements. Electronic assembly’s heart lies the ‘soldering technology’ and the ‘solder joints’ between electronic components and substrate. During the operation of electronic products, solder joints experience harsh environmental conditions in terms of cyclic change of temperature and vibration and exposure to moisture and chemicals. Due to the cyclic application of loads and higher operational temperature, solder joints fail primarily through creep and fatigue failures. This paper presents the creep-fatigue behaviours of solder joints in a ball grid array (BGA) soldered on a printed circuit board (PCB). Using finite element (FE) simulation, the solder joints were subjected to thermal cycling and isothermal ageing. Accelerated thermal cycling (ATC) was carried out using a temperate range from 40°C to 150°C, and isothermal ageing was done at −40, 25, 75 and 150°C temperatures for 45 days (64,800 mins). The solders studied are lead-based eutectic Sn63Pb37 and lead-free SAC305, SAC387, SAC396 and SAC405. The results were analysed using the failure criterion of equivalent stress, strain rate, deformation rate, and the solders’ strain energy density. The SAC405 and SAC396 have the least stress magnitude, strain rate, deformation rate, and strain energy density damage than the lead-based eutectic Sn63Pb37 solder; they have the highest fatigue lives based on the damage mechanisms. This research provides a technique for determining the preventive maintenance time of BGA components in mission-critical systems. Furthermore, it proposes developing a new life prediction model based on a combination of the damage parameters for improved prediction.

An Energy Based Critical Fatigue Life Prediction Method

2011 ◽  
Author(s):  
Todd Letcher ◽  
M.-H. Herman Shen ◽  
Onome Scott-Emuakpor ◽  
Tommy George ◽  
Charles Cross
Keyword(s):  
Fatigue Life ◽  
Energy Density ◽  
Strain Energy Density ◽  
Strain Energy ◽  
Life Prediction ◽  
Failure Process ◽  
Prediction Method ◽  
Fatigue Life Prediction ◽  
Stress Strain ◽  
Energy Behavior

The capability of a critical life, energy-based fatigue prediction method is analyzed in this study. The theory behind the prediction method states that the strain energy accumulated during monotonic fracture and fatigue are equal. Therefore, a precise understanding of the strain energy density behavior in each failure process is necessary. The initial understanding of energy behavior shows that the accumulated strain energy density during monotonic fracture is the area underneath the experimental stress-strain curve, whereas the sum of the constant area within every stress-strain hysteresis loop of the cyclic loading process is the total strain energy density accumulated during fatigue; meaning, fatigue life is determined by dividing monotonic strain energy density by the strain energy density in one cycle. Further observation of the energy trend during fatigue shows that strain energy density per cycle is not constant throughout the process as initially assumed. This finding led to the incorporation of a critical life effect into the energy-based fatigue prediction method. The analysis of the method’s capability was conducted on Al 6061-T6 ASTM standard specimens. The results of the analysis provide further improvement to the characterization of strain energy density for both monotonic fracture and fatigue; thus improving the capability of the energy-based fatigue life prediction method.

Prediction of Mechanical Behavior of Equivalent Adhesive-Layer Using Theory of Duality of Famage

2006 ◽  
Author(s):  
Jiemin Liu ◽  
Yazhen Sun ◽  
Jintang Liu
Keyword(s):  
Energy Density ◽  
Strain Energy Density ◽  
Strain Energy ◽  
Adhesive Layer ◽  
Total Strain ◽  
Mechanical Behaviors ◽  
Stress Strain ◽  
Stress Strain Relation ◽  
Strain Trajectory ◽  
Theory Of Duality

Concepts of equivalent adhesive-layer and Theory of Duality of Damage (TDD) are presented. Basic idea of the TDD is to assume that material damaged consists of two parts, i.e., Relative Non-Damaged Part (RNDP) and Complete Damaged Part (CDP). The mechanical behaviors of the material damaged can be simulated simultaneously by both mechanical behaviors of the RNDP and the CDP. The RNDP can be simulated by linear-elasticity and non-linear elasticity, respectively. The CDP can be approximately determined in engineering significant. Observed stress-strain relation of the equivalent adhesive layer of a steel/steel butt joint is measured. Evolution equation of damage of the equivalent adhesive-layer is established, and increment equation of stress-strain including effect of damage is given. The observed stress-strain relation is predicted through four damage parameters, i.e., plastic strain trajectory, plastic strain energy density, total strain trajectory, and total strain energy density. As a result, it is shown that the stress-strain curves predicted are of consistence with the observed stress-strain curve. The result predicted using total strain trajectory is better than others. It should be pointed out that the method presented in this paper could be applied to a variety of damaged structures not only to the equivalent adhesive-layer.

Strain Energy Density Criterion for Reliability Life Prediction of Solder Joints in Electronic Packaging

2004 ◽  
Vol 126 (3) ◽  
pp. 398-405 ◽  
Author(s):  
I. Guven ◽  
V. Kradinov ◽  
J. L. Tor ◽  
E. Madenci
Keyword(s):  
Growth Rate ◽  
Crack Growth Rate ◽  
Energy Density ◽  
Crack Growth ◽  
Strain Energy Density ◽  
Strain Energy ◽  
Life Prediction ◽  
Solder Joints ◽  
Intrinsic Property ◽  
Electronic Packages

This study concerns the prediction of crack growth rate for solder joints in electronic packages under thermal cycling. The crack growth rate, which is dependent on the intrinsic solder property and the current stress state, is calculated based on the strain energy density criterion. The critical value of the strain energy density represents the intrinsic property of the solder. The comparison of the crack growth predictions with the experimental measurements demonstrates the applicability of the strain energy density criterion for the reliability life prediction of solder joints.

Solder Joint Reliability of Wafer Level Chip Scale Packages (WLCSP): A Time-Temperature-Dependent Creep Analysis

2000 ◽  
Vol 122 (4) ◽  
pp. 311-316 ◽  
Author(s):  
John H. Lau ◽  
S.-W. Ricky Lee ◽  
Chris Chang
Keyword(s):  
Shear Stress ◽  
Energy Density ◽  
Solder Joint ◽  
Creep Strain ◽  
Strain Energy Density ◽  
Strain Energy ◽  
Rate Theory ◽  
Wafer Level ◽  
Temperature Dependent ◽  
Shear Creep

A novel and reliable wafer level chip scale package (WLCSP) is investigated in this paper. It consists of a copper conductor layer and two low cost dielectric layers. The bump geometry consists of the eutectic solder, the copper core, and the under bump metallurgy. Nonlinear time-temperature-dependent finite element analyses are performed to determine the shear stress, shear creep strain, shear stress and shear creep strain hysteresis loops, and creep strain energy density of the corner solder joint. The thermal-fatigue life of the corner solder joint is then predicted by the averaged creep strain energy density range per cycle and a linear fatigue crack growth rate theory. The WLCSP solder bumps are also subjected to shear test. Finally, the WLCSP solder joints are subjected to both mechanical shear and thermal cycling tests. [S1043-7398(00)01004-5]

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