Stress–Strain Behavior of SAC305 at High Strain Rates

2015 ◽  
Vol 137 (1) ◽  
Author(s):  
Pradeep Lall ◽  
Sandeep Shantaram ◽  
Jeff Suhling ◽  
David Locker
Keyword(s):  
Constitutive Model ◽  
Solder Alloy ◽  
High Strain ◽  
Image Correlation ◽  
Lead Free ◽  
Constitutive Behavior ◽  
Strain Rates ◽  
Mechanical Shock ◽  
High Strain Rates ◽  
Test Technique

Electronic products are subjected to high G-levels during mechanical shock and vibration. Failure-modes include solder-joint failures, pad cratering, chip-cracking, copper trace fracture, and underfill fillet failures. The second-level interconnects may be experience high strain rates and accrue damage during repetitive exposure to mechanical shock. Industry migration to lead-free solders has resulted in proliferation of a wide variety of solder alloy compositions. One of the popular tin-silver-copper alloys is Sn3Ag0.5Cu. The high strain rate properties of lead-free solder alloys are scarce. Typical material tests systems are not well suited for measurement of high strain rates typical of mechanical shock. Previously, high strain rates techniques such as the split Hopkinson pressure bar (SHPB) can be used for strain rates of 1000 s−1. However, measurement of materials at strain rates of 1–100 s−1 which are typical of mechanical shock is difficult to address. In this paper, a new test-technique developed by the authors has been presented for measurement of material constitutive behavior. The instrument enables attaining strain rates in the neighborhood of 1–100 s−1. High-speed cameras operating at 300,000 fps have been used in conjunction with digital image correlation (DIC) for the measurement of full-field strain during the test. Constancy of crosshead velocity has been demonstrated during the test from the unloaded state to the specimen failure. Solder alloy constitutive behavior has been measured for SAC305 solder. Constitutive model has been fit to the material data. Samples have been tested at various time under thermal aging at 25 °C and 125 °C. The constitutive model has been embedded into an explicit finite element framework for the purpose of life-prediction of lead-free interconnects. Test assemblies has been fabricated and tested under Joint Electron Device Engineering Council (JEDEC) JESD22-B111 specified condition for mechanical shock. Model predictions have been correlated with experimental data.

Constitutive Behavior of SAC Leadfree Alloys at High Strain Rates

2011 ◽  
Author(s):  
Pradeep Lall ◽  
Sandeep Shantaram ◽  
Mandar Kulkarni ◽  
Geeta Limaye ◽  
Jeff Suhling
Keyword(s):  
Constitutive Model ◽  
Solder Alloy ◽  
Failure Modes ◽  
High Strain ◽  
Image Correlation ◽  
Constitutive Behavior ◽  
Strain Rates ◽  
Mechanical Shock ◽  
High Strain Rates ◽  
Test Technique

Electronic products are subjected to high G-levels during mechanical shock and vibration. Failure-modes include solder-joint failures, pad cratering, chip-cracking, copper trace fracture, and underfill fillet failures. The second-level interconnects may be experience high-strain rates and accrue damage during repetitive exposure to mechanical shock. Industry migration to leadfree solders has resulted in proliferation of a wide variety of solder alloy compositions. Few of the popular tin-silver-copper alloys include Sn1Ag0.5Cu and Sn3Ag0.5Cu. The high strain rate properties of leadfree solder alloys are scarce. Typical material tests systems are not well suited for measurement of high strain rates typical of mechanical shock. Previously, high strain rates techniques such as the Split Hopkinson Pressure Bar (SHPB) can be used for strain rates of 1000 per sec. However, measurement of materials at strain rates of 1–100 per sec which are typical of mechanical shock is difficult to address. In this paper, a new test-technique developed by the authors has been presented for measurement of material constitutive behavior. The instrument enables attaining strain rates in the neighborhood of 1 to 100 per sec. High speed cameras operating at 300,000 fps have been used in conjunction with digital image correlation for the measurement of full-field strain during the test. Constancy of cross-head velocity has been demonstrated during the test from the unloaded state to the specimen failure. Solder alloy constitutive behavior has been measured for SAC105, and SAC305 solders. Constitutive model has been fit to the material data. Samples have been tested at various time under thermal aging at 25°C and 125°C. The constitutive model has been embedded into an explicit finite element framework for the purpose of life-prediction of leadfree interconnects. Test assemblies has been fabricated and tested under JEDEC JESD22-B111 specified condition for mechanical shock. Model predictions have been correlated with experimental data.

Mechanical Behavior of Sn1Ag0.5Cu and Sn3Ag0.5Cu Alloys at High Strain Rates

2012 ◽  
Author(s):  
Pradeep Lall ◽  
Sandeep Shantaram ◽  
Jeff Suhling ◽  
David Locker
Keyword(s):  
Strain Rate ◽  
High Speed ◽  
Prolonged Exposure ◽  
High Strain ◽  
Split Hopkinson Pressure Bar ◽  
Image Correlation ◽  
Constitutive Behavior ◽  
Strain Rates ◽  
High Strain Rates ◽  
Test Technique

Electronics may experience high strain rates when subjected to high g-loads of shock and vibration. Material and damage behavior of electronic materials at high strain rates typical of shock and vibration is scarce. Previously studies have shown that second-level interconnects have a high propensity for failure under shock and vibration loads in fine pitch electronics. Exposure to shock and vibration is common in a variety of consumer environments such as automotive and portable electronics. The low strain-rate properties of commonly used SnAgCu solders, including Sn1Ag0.5Cu and Sn3Ag0.5Cu, have been found to evolve with time after prolonged exposure to high temperatures. High strain rate properties of leadfree solder alloys in the strain-rate range of 1–100 sec−1 are scarce. Previous attempts at characterizing the high strain rates properties have focused on the use of the Split Hopkinson Pressure Bar (SHPB), which enables measurements of strain rates in the neighborhood of 1000 per sec. In this paper, a new test-technique developed by the authors has been presented for measurement of material constitutive behavior. The instrument enables attaining strain rates in the neighborhood of 1 to 100 per sec. Tests are conducted at strain rates 10, 35 and 50 per sec. High speed cameras operating at 75,000 fps have been used in conjunction with digital image correlation for the measurement of full-field strain during the test. Constancy of cross-head velocity has been demonstrated during the test from the unloaded state to the specimen failure. Solder alloy constitutive behavior has been measured for SAC105, SAC305 solders. Non-linear Ramberg-Osgood model has been used to fit the material data. The Ramberg-Osgood model available in Abaqus has been used for tensile test simulation and to correlate with DIC based experimental strain data.

Evolution of Anand Parameters With Elevated Temperature Aging for SnAgCu Lead-free Alloys

2020 ◽  
Vol 143 (2) ◽  
Author(s):  
Pradeep Lall ◽  
Vikas Yadav ◽  
Jeff Suhling ◽  
David Locker
Keyword(s):  
Constitutive Model ◽  
Thermal Aging ◽  
High Strain ◽  
Lead Free ◽  
Constitutive Behavior ◽  
Strain Rates ◽  
Lead Free Solder ◽  
High Strain Rates ◽  
Shock Event ◽  
Free Solder

Abstract Electronic components in downhole oil drilling and gas industry applications, automotive, and avionics may be exposed to high temperatures (>150 °C) and high strain rates (1–100 per sec) during storage, operation, and handling, which can contribute to the failures of electronic devices. Temperatures in these applications can exceed 200 °C, which is close to melting point for SnAgCu (SAC) alloys. Prior studies at low strain rates have shown property evolution even under moderate exposure to high temperature. In this paper, the evolution of Anand parameters for unaged and aged SAC (SAC105 and SAC-Q) lead-free solder alloys at high strain rates has been investigated induced under sustained periods of thermal aging. The thermal aged lead-free SAC solder alloys specimen has been tested at high strain rates (10–75 per sec) at elevated temperatures of (25 °C–200 °C). The SAC lead-free solder samples were subjected to isothermal aging at 50 °C up to 1-year before testing. To describe the material constitutive behavior, the Anand Viscoplastic model has been used. The effect of thermal aging on Anand parameters also has been investigated. In order to verify the accuracy of the model, the computed Anand parameters have been used to simulate the uni-axial tensile test. The material constitutive behavior has been implemented in a finite element framework to simulate the drop events using the Anand constitutive model and determine the plastic work per shock event. The plastic work per shock event is a measure of the damage progression in the solder interconnects. The constitutive model has been used to simulate the shock event of a ball-grid array package on printed circuit board assembly.

Experimental Studies of the Behaviour at High Strain Rates of Unfilled and Filled Polypropylenes

2006 ◽  
Vol 3-4 ◽  
pp. 363-368 ◽  
Author(s):  
N. Temimi ◽  
Noelle Billon
Keyword(s):  
Strain Rate ◽  
High Speed ◽  
High Strain ◽  
Experimental Studies ◽  
Young Modulus ◽  
Video Camera ◽  
Image Correlation ◽  
Strain Rates ◽  
High Strain Rates ◽  
Low Velocity

Thermo mechanical behaviour of unfilled and filled polypropylenes are studied in tension from 10-4 to 102 s-1. Complementary low velocity compression and shear tests are also performed. A high-speed video camera (up to 2500 frames/s) combined with image analysis, image correlation and an infra red pyrometer allow measuring 3D-strain fields and temperature during tests. Thus, data can be processed without restrictive assumptions. Beside usual (for polymers) temperature and strain rate sensitivities it is found that plastic deformation in these materials does not obey incompressibility assumption. Voiding damage is evidenced in the polymer matrix by SEM observations that result in volume change and significant decrease in Young modulus for both materials. Moreover, an increase in the temperature of more than 10 °C is observed and is likely to modify the behaviour of each material at high strain rates. Shear and compression measurements demonstrate that yield criteria and constitutive equation depend on loading. It is concluded that apparent yield stress in semi-crystalline polypropylene can be a result of a combination of “non strain rate sensitive” “non-cohesive mechanisms” and “strain rate sensitive” “cohesive mechanisms”. Experimental characterisation on polymers should then be revisited as most of the usual assumptions are invalid and non monotonic tests should be generalized.

Characterization of a Ferritic Stainless Sheet Steel in Simple Shear and Uniaxial Tension at Different Strain Rates

2011 ◽  
Author(s):  
Matti Isakov ◽  
Jeremy Seidt ◽  
Kauko O¨stman ◽  
Amos Gilat ◽  
Veli-Tapani Kuokkala
Keyword(s):  
Uniaxial Tension ◽  
Simple Shear ◽  
High Strain ◽  
Image Correlation ◽  
Materials Testing ◽  
Strain Rates ◽  
Test Results ◽  
High Strain Rates ◽  
Stress Strain

In this study the mechanical properties of ferritic stainless steel EN 1.4521 (AISI 444) were characterized in uniaxial tension and simple shear. The specimen geometries were designed so that tests could be carried out both with a conventional uniaxial materials testing machine and at high strain rates with the Tensile Hopkinson Split Bar method. During the tests, specimen surface deformation was measured using a three dimensional digital image correlation technique based on a two-camera stereovision setup. This technique allowed direct measurement of the specimen gauge section deformation during the test. Test results indicate that the selected approach is suitable for large strain plastic deformation characterization of ductile metals. The stress-strain data obtained from the simple shear tests shows a correlation with the tensile test results according to the von Mises effective stress-strain criterion. Since necking is absent in shear, test data can be obtained at considerably higher plastic strains than in tension. However, the final fracture occurs under a complex loading mode due to the distortion of the specimen geometry and multiaxial loading introduced by the simple shear arrangement. Test results also show that reliable material data can be obtained at high strain rates.

Strain Rate Effects and Rate-Dependent Constitutive Models of Lead-Based and Lead-Free Solders

2009 ◽  
Vol 77 (1) ◽  
Author(s):  
Fei Qin ◽  
Tong An ◽  
Na Chen
Keyword(s):  
Strain Rate ◽  
Impact Analysis ◽  
Solder Joints ◽  
High Strain ◽  
Drop Impact ◽  
Lead Free ◽  
Strain Rates ◽  
High Strain Rates ◽  
Rate Dependent ◽  
Lead Free Solders

As traditional lead-based solders are banned and replaced by lead-free solders, the drop impact reliability is becoming increasingly crucial because there is little understanding of mechanical behaviors of these lead-free solders at high strain rates. In this paper, mechanical properties of one lead-based solder, Sn37Pb, and two lead-free solders, Sn3.5Ag and Sn3.0Ag0.5Cu, were investigated at strain rates that ranged from 600 s−1 to 2200 s−1 by the split Hopkinson pressure and tensile bar technique. At high strain rates, tensile strengths of lead-free solders are about 1.5 times greater than that of the Sn37Pb solder, and also their ductility are significantly greater than that of the Sn37Pb. Based on the experimental data, strain rate dependent Johnson–Cook models for the three solders were derived and employed to predict behaviors of solder joints in a board level electronic package subjected to standard drop impact load. Results indicate that for the drop impact analysis of lead-free solder joints, the strain rate effect must be considered and rate-dependent material models of lead-free solders are indispensable.

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