Auburn University

Auburn University is a comprehensive land-grant institution with primary missions including instruction, research, and extension/outreach.

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Auburn University was established in 1856 as the East Alabama Male College, 20 years after the city of Auburn's founding. In 1872, under the Morrill Act, the school became the first land-grant college in the South and was renamed the Agricultural and Mechanical College of Alabama. In 1899 the name again was changed, to the Alabama Polytechnic Institute. Finally, in 1960 the name of the school was changed to Auburn University, a title more in keeping with its location, and expressing the varied academic programs and larger curriculum of a major university.

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8 technical articles »

Analysis of the Mechanical Behavior, Microstructure, and Reliability of Mixed Formulation Solder Joints

Sep 26, 2023 | Yifei Zhang, Kanth Kurumaddali, Jeffrey C. Suhling, Pradeep Lall, Michael J. Bozack

The transition from tin-lead to lead free soldering in the electronics manufacturing industry has been in progress for the past 10 years. In the interim period before lead free assemblies are uniformly accepted, mixed formulation solder joints are becoming commonplace in electronic assemblies. For example, area array components (BGA/CSP) are frequently available only with lead free Sn-Ag-Cu (SAC) solder balls. Such parts are often assembled to printed circuit boards using traditional 63Sn-37Pb solder paste. The resulting solder joints contain unusual quaternary alloys of Sn, Ag, Cu, and Pb. In addition, the alloy composition can vary across the solder joint based on the paste to ball solder volumes and the reflow profile utilized. The mechanical and physical properties of such Sn-Ag-Cu-Pb alloys have not been explored extensively in the literature. In addition, the reliability of mixed formulation solder joints is poorly understood....

The Effects of Silver Content and Solidification Profile on the Anand Constitutive Model for SAC Lead Free Solders

Jun 14, 2023 | Munshi M. Basit, Mohammad Motalab, Jordan C. Roberts, Jeffrey C. Suhling, Pradeep Lall

In the electronic packaging industry, it is important to be able to make accurate predictions of board level solder joint reliability during thermal cycling exposures. The Anand viscoelastic constitutive model is often used to represent the material behavior of the solder in finite element simulations. This model is defined using nine material parameters, and the reliability prediction results are often highly sensitive to the Anand parameters. In this work, an investigation on the Anand constitutive model and its application to SAC solders of various Ag contents (i.e. SACN05, with N = 1, 2, 3, 4) has been performed. For each alloy, both water quenched (WQ) and reflowed (RF) solidification profiles were utilized to establish two unique specimen microstructures, and the same reflow profile was used for all four of the SAC alloys so that the results could be compared and the effects of Ag content could be studied systematically....

Effect Of Vacuum Reflow On Solder Joint Voiding In Bumped Components

Oct 31, 2022 | Arvind Srinivasan Karthikeyan, Sa'd Hamasha, Michael Meilunas, and Fred Dimock

Voids affect the thermal characteristics and mechanical properties of a solder joint, thereby affecting the reliability of the solder interconnect. The automotive sector in particular is requiring the mitigation of solder voids in various electronic control modules to the minimum possible level. Earlier research efforts performed to decrease voids involved varying the reflow profile, paste deposit, paste alloy composition, stencil aperture, and thickness. Due to the various advantages they offer, the use of Ball Grid Array packages is common across all industry sectors. They are also prone to process voiding issues. This study was performed to determine if vacuum assisted reflow process can help alleviate the voids in area array solder joints. Test parameters in this study largely focused on vacuum pressure level and vacuum dwell time....

Surfaces of mixed formulation solder alloys at melting

Oct 31, 2022 | M. J. Bozack, J. C. Suhling, Y. Zhang, Z. Cai, and P. Lall

Mixed formulation solder alloys refer to specific combinations of Sn-37Pb and SAC305 (96.5Sn–3.0Ag–0.5Cu). They present a solution for the interim period before Pb-free electronic assemblies are universally accepted. In this work, the surfaces of mixed formulation solder alloys have been studied by in situ and real-time Auger electron spectroscopy as a function of temperature as the alloys are raised above the melting point. With increasing temperature, there is a growing fraction of low-level, bulk contaminants that segregate to the alloy surfaces. In particular, the amount of surface C is nearly _50–60 at. % C at the melting point. The segregating impurities inhibit solderability by providing a blocking layer to reaction between the alloy and substrate. A similar phenomenon has been observed over a wide range of (SAC and non-SAC) alloys synthesized by a variety of techniques. That solder alloy surfaces at melting have a radically different composition from the bulk uncovers a key variable that helps to explain the wide variability in contact angles reported in previous studies of wetting and adhesion. VC 2011 American Vacuum Society. [DOI: 10.1116/1.3584821]...

ASSESSMENT OF ACCRUED THERMO-MECHANICAL DAMAGE IN LEADFREE PARTS DURING FIELD-EXPOSURE TO MULTIPLE ENVIRONMENTS

Oct 11, 2022 | Pradeep Lall, Ph.D., Rahul Vaidya and Vikrant More and Kai Goebel, Ph.D.

Electronic assemblies deployed in harsh environments may be subjected to multiple thermal environments during the use-life of the equipment. Often the equipment may not have any macro-indicators of damage such as cracks or delamination. Quantiication of thermal environments during use-life is often not feasible because of the data-capture and storage requirements, and the overhead on core-system functionality. There is need for tools and techniques to quantify damage in deployed systems in absence of macro-indicators of damage without knowledge of prior stress history. The presented PHM framework is targeted towards high reliability applications such as avionic and space systems. In this paper, Sn3.0Ag0.5Cu alloy packages have been subjected to multiple thermal cycling environments including -55 to 125C and 0 to 100C. Assemblies investigated include area-array packages soldered on FR4 printed circuit cards. The methodology involves the use of condition monitoring devices, for gathering data on damage pre-cursors at periodic intervals. Damage-state interrogation technique has been developed based on the Levenberg-Marquardt Algorithm in conjunction with the microstructural damage evolution proxies. The presented technique is applicable to electronic assemblies which have been deployed on one thermal environment, then withdrawn from service and targeted for redeployment in a different thermal environment. Test cases have been presented to demonstrate the viability of the technique for assessment of prior damage, operational readiness and residual life for assemblies exposed to multiple thermo-mechanical environments. Prognosticated prior damage and the residual life show good correlation with experimental data, demonstrating the validity of the presented technique for multiple thermo-mechanical environments....

Component Level Reliability For High Temperature Power Computing With SAC305 And Alternative High Reliability Solders

Feb 16, 2017 | Thomas Sanders, Sivasubramanian Thirugnanasambandam and John Evans, Ph.D., Michael Bozack, Ph.D., Jeff Suhling, Ph.D. - Auburn University, Wayne Johnson, Ph.D. - Tennessee Tech University

This experiment considers the reliability of a variety of different electronic components and evaluates them on 0.200” power computing printed circuit boards with OSP. Single-sided assemblies were built separately for the Top-side and Bottom-side of the boards. This data is for boards on the FR4-06 substrate.

This paper was originally published by SMTA in the Proceedings of SMTA International....

SMT Line Improvements for High Mix, Low Volume Electronics Manufacturing

Aug 04, 2011 | William Edward Swaim

This work covers two major projects aimed at increasing quality and efficiency on a high mix, low volume surface mount electronics production line. Specifically the installation of a ten zone reflow oven and an enhanced changeover method for SMT pick and ...

Assessment of Residual Damage in Leadfree Electronics Subjected to Multiple Thermal Environments of Thermal Aging and Thermal Cycling

Oct 21, 2010 | Pradeep Lall, Rahul Vaidya, Vikrant More, Kai Goebel, Jeff Suhling

Electronic systems are often stored for long periods prior to deployment in the intended environment. Aging has been previously shown to effect the reliability and constitutive behavior of second-level leadfree interconnects....

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