Thesis (Ph. D.)--State University of New York at Binghamton, Department of Systems Science and Industrial Engineering, 2007. / Includes bibliographical references (leaves 278-290).

Thesis (Ph. D.)--State University of New York at Binghamton, Thomas J. Watson School of Engineering and Applied Science, Department of Mechanical Engineering, 2008. / Includes bibliographical references.

abstract: This dissertation presents methods for addressing research problems that currently can only adequately be solved using Quality Reliability Engineering (QRE) approaches especially accelerated life testing (ALT) of electronic printed wiring boards with applications to avionics circuit boards. The methods presented in this research are generally applicable to circuit boards, but the data generated and their analysis is for high performance avionics. Avionics equipment typically requires 20 years expected life by aircraft equipment manufacturers and therefore ALT is the only practical way of performing life test estimates. Both thermal and vibration ALT induced failure are performed and analyzed to resolve industry questions relating to the introduction of lead-free solder product and processes into high reliability avionics. In chapter 2, thermal ALT using an industry standard failure machine implementing Interconnect Stress Test (IST) that simulates circuit board life data is compared to real production failure data by likelihood ratio tests to arrive at a mechanical theory. This mechanical theory results in a statistically equivalent energy bound such that failure distributions below a specific energy level are considered to be from the same distribution thus allowing testers to quantify parameter setting in IST prior to life testing. In chapter 3, vibration ALT comparing tin-lead and lead-free circuit board solder designs involves the use of the likelihood ratio (LR) test to assess both complete failure data and S-N curves to present methods for analyzing data. Failure data is analyzed using Regression and two-way analysis of variance (ANOVA) and reconciled with the LR test results that indicating that a costly aging pre-process may be eliminated in certain cases. In chapter 4, vibration ALT for side-by-side tin-lead and lead-free solder black box designs are life tested. Commercial models from strain data do not exist at the low levels associated with life testing and need to be developed because testing performed and presented here indicate that both tin-lead and lead-free solders are similar. In addition, earlier failures due to vibration like connector failure modes will occur before solder interconnect failures. / Dissertation/Thesis / Ph.D. Industrial Engineering 2012

Depuis l’entrée en vigueur de la directive RoHS (Restriction of Hazardous Substances Directive) interdisant l’utilisation du plomb, les industriels des secteurs aéronautique et militaire se doivent de comprendre le comportement en fatigue des nouveaux alliages sans plomb afin de pouvoir estimer leur durabilité en conditions réelles d’utilisation. En se basant sur les résultats d’essais accélérés et les modélisations éléments-finis associées, les modèles de fatigue mécanique et thermomécanique correspondant aux brasures SAC305 sont développés. Le 1er chapitre traite de la caractérisation mécanique et optique de cet alliage sans plomb. Après une étude bibliographique poussée, les propriétés élastiques et viscoplastiques de l’alliage SAC305 sont établies à partir d’essais d’écrouissage, de traction et de nanoindentation. La courbe d’hystérésis contrainte - déformation en cisaillement est en outre tracée via l’utilisation de jauges de déformation. Des analyses EBSD sont finalement réalisées afin d’identifier les caractéristiques microstructurales des joints de brasure SAC305 après refusion. Le chapitre 2 a pour objectif d’évaluer la durabilité des interconnexions SAC305 soumises à des chargements en vibrations et en chocs. L’hypothèse élastique est retenue et les paramètres matériaux du modèle de Basquin sont déterminés. À partir de l’algorithme de comptage rainflow et de la loi de Miner, une méthode d’évaluation de la durabilité en vibration aléatoire est donnée. La tenue mécanique en chocs des brasures SAC305 est enfin discutée et comparée à l’alliage SnPb63Ag2. Le dernier chapitre porte sur l’étude de la fatigue thermomécanique des joints brasés SAC305. En utilisant le modèle viscoplastique unifié d’Anand, la loi de fatigue énergétique correspondant est développée. Le phénomène de recristallisation caractéristique de l’endommagement thermomécanique des brasures SAC305 est finalement investigué à partir d’analyses EBSD. / Temperature and vibration-induced solder joint fatigue are main reliability concerns for aeronautic 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 solder behavior used in thermal en vibrational environments. This study reports fatigue life prediction methodologies developed to assess the durability of SAC305 solder joints subjected to temperature variations and vibration loadings. Based on accelerated tests and finite element analysis, solder joint fatigue models corresponding to each environment are developed. Chapter 1 discusses SAC305 solder mechanical characterization and its microstructural features. An indepth literature review is conducted and SAC305 solder elastic and viscoplastic properties are determined through tensile, creep and nanoindentation tests. An approach never considered for lead-free solder joints is also applied to plot the SAC305 shear strain - stress hysteresis loop. EBSD analysis is finally performed in order to identify the microstructural “finger print” of asreflowed SAC305 solder joints. Chapter 2 aims to determine the polycyclic fatigue curve corresponding to SAC305 interconnects damage under harmonic vibrations. Considering the rainflow counting algorithm along with the Miner’s linear damage rule, the corresponding Basquin’s model is used as an input data for assessing SAC305 durability under random vibrations. SAC305 endurance under shock loading is finally discussed and compared with SnPb36Ag2 assemblies. The final chapter deals with the thermomechanical fatigue assessment of SAC305 solder joints. An energy-based model is developed using Anand unified viscoplastic law. EBSD analysis is finally conducted to assess the SAC305 microstructure evolution throughout thermal cycling characterized by -Sn grains recrystallization.

abstract: With increasing concerns of the intrinsic toxicity of lead (Pb) in electronics, a series of tin (Sn) based alloys involving silver (Ag) and copper (Cu) have been proposed as replacements for Pb-Sn solder and widely accepted by industry. However, they have a higher melting point and often exhibit poorer damage tolerance than Pb-Sn alloys. Recently, a new class of alloys with trace amount of rare-earth (RE) elements has been discovered and investigated. In previous work from Prof. Chawla's group, it has been shown that cerium (Ce)-based Pb-free solder are less prone to oxidation and Sn whiskering, and exhibit desirable attributes of microstructural refinement and enhanced ductility relative to lanthanum (La)-based Sn-3.9Ag-0.7Cu (SAC) alloy. Although the formation of RESn3 was believed to be directly responsible for the enhanced ductility in RE-containing SAC solder by allowing microscopic voids to nucleate throughout the solder volume, this cavitation-based mechanism needs to be validated experimentally and numerically. Additionally, since the previous study has exhibited the realistic feasibility of Ce-based SAC lead-free solder alloy as a replacement to conventional SAC alloys, in this study, the proposed objective focuses on the in in-depth understanding of mechanism of enhanced ductility in Ce-based SAC alloy and possible issues associated with integration of this new class of solder into electronic industry, including: (a) study of long-term thermal and mechanical stability on industrial metallization, (b) examine the role of solder volume and wetting behavior of the new solder, relative to Sn-3.9Ag-0.7Cu alloys, (c) conduct experiments of new solder alloys in the form of mechanical shock and electromigration. The research of this new class alloys will be conducted in industrially relevant conditions, and the results would serve as the first step toward integration of these new, next generation solders into the industry. / Dissertation/Thesis / Ph.D. Materials Science and Engineering 2012

Este trabalho de pesquisa apresenta uma proposta para um sistema de supervisão automatizada de processo dedicado à soldagem de componentes eletrônicos. Essa soldagem é realizada por forno de refusão de solda, o qual pertence ao processo de montagem de produtos eletrônicos com tecnologia de dispositivo de montagem em superfície (Surface Mounting Devide SMD). Esses produtos, para o caso estudado, são aplicados no ramo automotivo, o qual exige que o processo produtivo tenha características destacadas de repetibilidade, padronização, além da preservação do meio ambiente. Para atender essas características o mencionado processo emprega a tecnologia de solda sem chumbo (lead free) na soldagem de componentes. Essa tecnologia exige que o perfil térmico possua uma média de temperatura maior sobre os elementos submetidos ao processo de soldagem, quando comparado com o processo tradicional estanho-chumbo. Para atender essa exigência o sistema de supervisão proposto neste trabalho adquire informações relacionadas a temperaturas das zonas do forno, integridade de resistência de aquecimento, sistema de insuflamento de ar quente e velocidade de operação da esteira transportadora de placas. Essa aquisição é apresentada para o operador do sistema, por meio de uma Interface Homem-Máquina, com a meta de alertar sobre o atual estado do processo. Nessa interface é destacada a previsão de campos relacionados com registro contínuo das informações adquiridas, parametrização de informações de processo, alarmes visuais e sonoros. A avaliação sistêmica dessa proposta de monitoração de informações indica que se forem controladas todas as características críticas do forno poderá haver contribuição para a melhoria no aludido processo de produção especialmente no que se refere à qualidade da soldagem, bem como a integridade física de todos os componentes do produto. / This research presents a proposal for an automated supervision system of dedicated soldering process of electronic components. This soldering is accomplished by a reflow oven, which belongs to the process of assembly of electronic products with Surface Mounting Device (SMD) technology. These products, for the studied case, are applied in the utomotive branch, which demands that the productive process has outstanding characteristics of repeatability, standardization, beyond of the preservation of the environment. To assist those characteristics mentioned, this process uses the solder technology without lead (lead free) in the soldering of components. This technology demands that the thermal profile possesses an average of bigger temperature on the elements submitted to the soldering process, when compared with the traditional process tin-lead. To assist that demand the supervision system proposed in this work acquires information related with temperature of oven zones, integrity of heating resistance, blower system and speed of board transportation belts / conveyors. This acquisition is presented for system operator by means of Man-machine Interface, with the goal of to sensitize on the current state of the process. In that interface it is detached the forecast of fields related with continuous registration of the acquired information, make the process information on a parameter, visual and sonorous alarms. The systemic evaluation of this proposal indicates that if controlled all the critical characteristics of the oven it will be able to have contribution for the improvement in the alluded process of production especially in what refers to the quality of the product.

Abstract Low-temperature co-fired ceramic (LTCC) based system-in-package (SiP) is an emerging multilayer module technology for wireless communication applications, mainly due to its excellent high-frequency material properties. LTCC-SiP modules are typically soldered onto an organic motherboard, but the lifetime of the 2nd-level solder joints is often poor due to the high stress level of the joints in test/field conditions. Moreover, using lead-free solders in the interconnections of LTCC modules raised new questions about the feasibility and reliability of the solder joints in LTCC applications. Therefore, the characteristic features of the 2nd-level solder joint configuration were determined in this thesis work. It was proved that collapsible Sn4Ag0.5Cu spheres are not a feasible option in LTCC/PWB assemblies with a large global thermal mismatch; a non-collapsible ball grid array (BGA) joint with a plastic core solder balls (PCSBs) was required to attain an adequate lifetime for such assemblies. To enhance the thermal fatigue endurance of the non-collapsible lead-free joints, a novel BGA joint consisting of Sn7In4.1Ag0.5Cu solder and PCSBs was developed. Moreover, this work proved that there is a relationship between the primary failure mechanisms of various Sn-based lead-free solders and thermomechanically induced stress level in the present non-collapsible BGA joint configuration. The effect of the plating material of the solder lands on the failure mechanism of the BGA joints in the LTCC/PWB assemblies was studied. The results showed that the adverse phenomena related to the sintered Ag-based metallization materials can be avoided using electroless nickel with immersion gold (ENIG) as a deposit material. On the other hand, this study also demonstrated that the inadequate adhesion strength of the commercial base metallization in the ENIG-plated modules resulted in the disadvantageous failure mechanism of the test assemblies. Therefore, the criteria for material selection and the design aspects of reliable 2nd-level interconnections are discussed thoroughly in this thesis.

This diploma thesis deals with the soldering process in manufacturing instrument transformers. It summarizes the knowledge of soldering process, lead-free alloys and test methods selected solder joint. In the practical part is the analysis the manufacturing process in terms of soldering operations, testing of selected lead-free alloys, which are considered as a replacement for lead-based alloy - now used in the manufacturing process. The conclusion is optimized manufacturing process to reduce operating costs and improve quality.

Ink-based semiconductors that come to mind today include conjugated molecules and polymers, colloidal quantum dots, metal halide hybrid perovskites, and transition metal oxides. These materials form an ink (solution/ suspension/ sol-gel) that can be applied and dried in ambient air to form high-quality films for optoelectronic devices. In this study, we will introduce the current understanding of ink-based lead and lead-free hybrid perovskite and perovskite-inspired thin films. Examples will be presented through time-resolved studies of the solidification to link the solid-state microstructure and device figures of merit to the ink’s formulation, drying, and solidification process. The perovskite crystallization kinetics characterized in situ during the solution process indicates an essential role by the inclusion of Cs+ and K+ alkali metal cations in perovskite inks. The film and device characterizations indicate the functions of mixed cation and halides in determining the optoelectronic properties. The further sophisticated design of perovskite inks enables significantly optimized charge dynamics, including exciton separation, inter-grain charge transfer, trap density, charge mobility, and charge collection efficiency. The considerably improved optoelectronic properties lead to higher charge collection efficiency and, therefore, better open-circuit voltage and fill factor for the Cs+-containing 3D perovskite devices in contrast to the control FAPbI3 one. Recent developments in ink formulation and processing that enable scalable ambient fabrication of high-quality perovskite semiconductor films will also be presented. These findings raise the possibility of developing more controlled perovskites for systematically addressing both charge dynamics and degradation mechanisms in concert for the timely commercialization of perovskite solar cells.

This thesis deals with fabrication and optimization of lead-free piezoceramics based on (Ba0,85Ca0,15Zr0,1Ti0,9)O3 (BCZT). The BCZT precursor powder was synthesized by sol-gel method. Dependence of relative density, microstructure, phase structure and piezoelectric properties on the sintering temperature in a range from 1300–1500 °C was studied on disc shaped samples, which were prepared by cold isostatic pressing (CIP) using pressure of 700 MPa. It was found, that sintering at 1300 and 1350 °C leads to ceramics with fine-grain microstructure, which exhibits poor piezoelectric properties (d*33 = 50 pC·N1 and 65 pC·N1, respectively). The highest value of piezoelectric charge coefficient was obtained by sintering at 1500 °C (d*33 = 390 pC·N1). Furthermore, BCZT thick films were prepared by tape casting. The composition of the ceramic slurry was optimized and various sintering techniques were tested to obtain completely flat films of BCZT ceramics. The correct sintering configuration has not been found. The least deformation of the films was achieved when the samples were sintered hung on the ZrO2 rod. The highest value of d*33 for BCZT films was measured when the sample was sintered at 1400 °C with the dwell time for 4 h (d*33 = 340 pC·N1).