Much recent research has focused on the development lead-free perovskite piezoelectrics as environmentally compatible alternatives to lead zirconate titanate (PZT). Two main categories of lead free perovskite piezoelectric ceramic systems were investigated as potential replacements to lead zirconate titanate (PZT) for actuator devices. First, solid solutions based on Li, Ta, and Sb modified (K���.���Na���.���)NbO��� (KNN) lead-free perovskite systems were created using standard solid state methods. Secondly, Bi-based materials a variety of compositions were explored for (1-x)(Bi���.���Na���.���)TiO���-xBi(Zn���.���Ti���.���)O��� (BNT-BZT) and Bi(Zn���.���Ti���.���)O������(Bi���.���K���.���)TiO������(Bi���.���Na���.���)TiO��� (BZT-BKT-BNT). It was shown that when BNT-BKT is combined with increasing concentrations of Bi(Zn[subscript 1/2]Ti[subscript 1/2])O��� (BZT), a transition from normal ferroelectric behavior to a material with large electric field induced strains was observed. The higher BZT containing compositions are characterized by large hysteretic strains (> 0.3%) with no negative strains that might indicate domain switching. This work summarizes and analyzes the fatigue behavior of the new generation of Pb-free piezoelectric materials. In piezoelectric materials, fatigue is observed as a degradation in the electromechanical properties under the application of a bipolar or unipolar cyclic electrical load. In Pb-based materials such as lead zirconate titanate (PZT), fatigue has been studied in great depth for both bulk and thin film applications. In PZT, fatigue can result from microcracking or electrode effects (especially in thin films). Ultimately, however, it is electronic and ionic point defects that are the most influential mechanism. Therefore, this work also analyzes the fatigue characteristics of bulk polycrystalline ceramics of the modified-KNN and BNT-BKT-BZT compositions developed. The defect chemistry that underpins the fatigue behavior will be examined and the results will be compared to the existing body of work on PZT. It will be demonstrated that while some Pb-free materials show severe property degradation under cyclic loading, other materials such as BNT-BKT-BZT essentially exhibit fatigue-free piezoelectric properties with chemical doping or other modifications. Based on these results, these new Pb-free materials have great potential for use in piezoelectric applications requiring a large number of drive cycles such as MEMS devices or high frequency actuators. / Graduation date: 2013

Thesis (M.S.)--State University of New York at Binghamton, Department of Systems Science and Industrial Engineering, 2005. / Includes bibliographical references (p. 94-96).

Thesis (M.S.)--State University of New York at Binghamton, Thomas J. Watson School of Engineering and Applied Science, Department of Systems Science and Industrial Engineering, 2007. / Includes bibliographical references.

Thesis (M.S.)--State University of New York at Binghamton, Thomas J. Watson School of Engineering and Applied Science, Department or Systems Science and Industrial Engineering, 2009. / Includes bibliographical references.

Thesis (Ph. D.)--State University of New York at Binghamton, Thomas J. Watson School of Engineering and Applied Science, Department of Systems Science and Industrial Engineering, 2009. / Includes bibliographical references.

Thesis (M.S.)--State University of New York at Binghamton, Department of Mechanical Engineering, 2005. / Includes bibliographical references (leaves 70-72).

Lead-free solders such as SnAg and SnAgCu are used extensively as replacements of SnPb solders in microelectronics packaging. But these alloys have several drawbacks, such as poor wetting ability and formation of intermetallic compounds (IMC). Doping of rare earth element (RE) on SnAg alloys has been found to improve the wetting property, reduce IMCs and their growth, and refine the microstructure which results in improved mechanical properties of the solder. This study focuses on establishing the quantitative effects of RE doping on the microstructure and mechanical behavior of 96.5Sn3.5Ag alloy. SnAg alloys with different amounts of Lanthanum were made. Specimens were cast under typical reflow conditions, and then aged at different temperatures for three different aging times. Quantitative microscopy was conducted on samples with different amounts of La doping. It was found that doping greatly reduces the grain size, as well as the size of the intermetallic particles Ag3Sn. However, the inter-particle spacing remains relatively unaffected by the La doping amount. Creep tests at various temperatures and strain rates were conducted. The results show that La doping increases creep resistance of the SnAg alloy by ~15%. The creep test result can be fit into a modified microstructure dependent Anand model. A new constitutive law was also proposed to account for the hierarchal microstructure over multiple length scales. Specifically, at the sub micrometer scale, the SnAg eutectic region is treated as a particulate-reinforced composite with the Ag3Sn being the particle and Sn being the matrix. At the micrometer length scale, the solder alloys is treated as a two-phase composite with the Sn dendrite as the particle and the SnAg eutectic region as the matrix. Good agreement was found between the model predictions and the creep test results. Fatigue test was performed on bulk samples. It was found that RE doping increases the fatigue life of SnAg alloy by a factor of 5.

This thesis is devoted to the research and development of low processing temperature lead-free interconnect materials for microelectronic packaging applications with an emphasis on fundamental studies of nanoparticles synthesis, dispersion and oxidation prevention, and nanocomposites fabrication. Oxide-free tin (Sn), tin/silver (96.5Sn3.5Ag) and tin/silver/copper (96.5Sn3.0Ag0.5Cu) alloy nanoparticles with different sizes were synthesized by a low temperature chemical reduction method. Both size dependent melting point and latent heat of fusion of the synthesized nanoparticles were obtained. The nano lead-free solder pastes/composites created by dispersing the SnAg or SnAgCu alloy nanoparticles into an acidic type flux spread and wet on the cleaned copper surface at 220 to 230 ¡æ. This study demonstrated the feasibility of nano sized SnAg or SnAgCu alloy particle pastes for low processing temperature lead-free interconnect applications in microelectronic packaging. Surface functionalized silver nanoparticles and silver fakes were used as fillers for electrically conductive adhesives (ECAs) applications. During the curing of epoxy resin (150 ¡æ), the surfactants were debonded from the particles and at the same time the oxide layers on the particle surfaces were removed which facilitated the sintering of Ag nanoparticles. The contact interfaces between fillers were significantly reduced and an ultra highly conductive ECA with a resistivity of 5 ¡Á 10-6 ohm.cm was obtained. To enhance the adhesion of carbon nanotube (CNT) films to substrates, an ultra highly conductive ECA were used as a media to transfer the CNT films to copper substrates. The polymer wetted along the CNTs during curing process by the capillary force. An ohmic contact was formed between the copper substrates and the transferred CNTs. This process could overcome the serious obstacles of integration of CNTs into integrated circuits and microelectronic device packages by offering low processing temperatures and improved adhesion of CNTs to substrates. The transferred CNTs can be used to simultaneously form electrical and mechanical connections between chips and substrates.

Electrically conductive adhesives (ECAs) are one of the lead-free interconnect materials with the advantages of environmental friendliness, mild processing conditions, fewer processing steps, low stress on the substrates, and fine pitch interconnect capability. However, some challenging issues still exist for the currently available ECAs, including lower electrical conductivity, conductivity fatigue in reliability tests, limited current-carrying capability, poor impact strength, etc. The interfacial properties is one of the major considerations when resolving these challenges and developing high performance conductive adhesives. Surface functionalization and interface modification are the major approaches used in this thesis. Fundamental understanding and analysis of the interaction between various types of interface modifiers and ECA materials and substrates are the key for the development of high performance ECA for lead-free interconnects. The results of this thesis provide the guideline for the enhancement of interfacial properties of metal-metal and metal-polymer interactions. Systematic investigation of various types of ECAs contributes to a better understanding of materials requirements for different applications, such as surface mount technology (SMT), flip chip applications, flat panel display modules with high resolution, etc. Improvement of the electrical, thermal and reliability of different ECAs make them a potentially ideal candidate for high power and fine pitch microelectronics packaging option.

Thesis (M.S.)--State University of New York at Binghamton, Thomas J. Watson School of Engineering and Applied Science, Department of Systems Science and Industrial Engineering, 2008. / Includes bibliographical references.