This study investigates the reliability of SnPb and SnAg solder joints in semiconductor packages subjected to thermal cycling. More specifically, solder joint crack growth and life are experimentally measured, and FEM models are run to explain the test results. Ultimately a life-prediction model is proposed for both SnPb and SnAg solder joint packages. Motorola 357-plastic ball grid array packages on printed wiring boards were thermal cycled with the following test parameters: SnPb and SnAg solders, three post-process conditions (aged, aircooled and quenched), four package layouts on the printed circuit boards (singledense, single-sparse, double-alternating, and double-dense), three accelerated thermal cycling protocols (0°C to 100°C, -40°C to 125°C, and -55°C to 125°C), and tests run at Motorola and the University of Texas. At predetermined thermal cycles, packages were removed from the environmental chambers, dyepenetrated, packages removed to expose the solder joints, and optical images taken. Images were processed to measure crack area, shape, orientation and length to show crack growth. Selected joints were sectioned and polished to investigate microstructure and failure modes. Selected boards were connected to an ANATECH event detector to monitor life from joint failures. FEM crack initiation and propagation models were developed to better understand failure mechanisms. Major experimental results are: 1) SnPb joints have about 50% faster crack growth rates than SnAg joints, subsequently SnPb joints have half the life of SnAg joints, 2) air-cooled and quenched packages had similar failure characteristics, but aged SnPb joints had lower life and aged SnAg joints had significantly longer life than the comparable nonaged joints, 3) double-dense package layout significantly decreased life (by 75%) over the other package layouts, which were similar to each other, 4) the test results at the two locations (UT and Motorola) were similar for SnPb solder joints, but significantly different for SnAg solder joints, and 5) the largest cracks occurred at the corners of joints just under the die edge. Major FEM simulation results are: 1) the crack initiation life of SnAg joints is approximately 100% longer than SnPb joints, 2) shear load is a major cause of crack growth, but the contribution of tensile load increases as the cracks grow, 3) primary cracks at the board interface appear to reduce the propagation rate of the primary crack on the package interface, 4) secondary cracks are suppressed when compressive stresses prevent voids from nucleating, 5) the double-dense configuration shows no PWB warping due to symmetry, and its stresses are larger than for the other package layouts, and (6) the stresses and strains for single-dense, single-sparse, and double-alternating package layouts are similar because the stresses/strains are dominated by local effects due to the CTE mismatch between the die and board. Based upon the experimental results and FEM simulations, a lifeprediction model based upon a severity metric was proposed. The metric estimates damage to the solder joints and links material properties and parameters associated with package layout and thermal test conditions to the time-dependent creep, time-independent plastic deformation, and a time-dependent and geometric effective stress of the solder. The severity metric predicted life very well for most of the data tested and was more accurate than the industry-standard life-prediction models for SnPb solder joints.

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.

Thesis (M.S.)--University of Missouri, School of Mines and Metallurgy, 1949. / Vita. The entire thesis text is included in file. Typescript. Title from title screen of thesis/dissertation PDF file (viewed July 8, 2010) Includes bibliographical references (p. 65).

In der vorliegenden Arbeit wird die Synthese von neuartigen Zinn(II)alkoxiden, deren Potential für die Zwillingspolymerisation und die Darstellung von zinnhaltigen organisch-anorganischen Nanokompositen beschrieben. Partielle Hydrolyse der Zinn(II)alkoxide führt zur Bildung von fünf- und sechskernigen Zinnoxidoclustern, die eine gute Löslichkeit in organischen polaren Lösungsmitteln besitzen. Eine Nachbehandlung der durch Zwillingspolymerisation erhaltenen Hybridmaterialien unter reduzierenden Bedingungen (Ar/H2) liefert Nanokomposite bestehend aus Zinnnanopartikeln eingebettet in eine Kohlenstoff/Siliziumdioxid-Matrix. Weiterhin werden verschiedene metallhaltige Additive wie z.B. Carboxylate in der Zwillingspolymerisation verwendet und deren Eignung zur Darstellung von zinnhaltigen Nanokompositen sowie zur Legierungsbildung mit Zinn im Nanokomposit untersucht. Mit ausgewählten Materialien werden elektrochemische Messungen durchgeführt, wobei deren potentieller Einsatz als Anodenmaterial für Lithiumionen-Batterien geprüft wird (Kooperation BASF SE, Research Performance Materials GMV/P). Die Charakterisierung der neu synthetisierten Verbindungen und Nanokomposite erfolgt unter anderem mittels Einkristallröntgenstrukturanalyse, Röntgenpulverdiffraktometrie, NMR-Spektroskopie, Infrarotspektroskopie, Elektronenmikroskopie sowie thermischen Analysemethoden

In der vorliegenden Arbeit wird die Synthese von neuartigen Zinn(II)alkoxiden, deren Potential für die Zwillingspolymerisation und die Darstellung von zinnhaltigen organisch-anorganischen Nanokompositen beschrieben. Partielle Hydrolyse der Zinn(II)alkoxide führt zur Bildung von fünf- und sechskernigen Zinnoxidoclustern, die eine gute Löslichkeit in organischen polaren Lösungsmitteln besitzen. Eine Nachbehandlung der durch Zwillingspolymerisation erhaltenen Hybridmaterialien unter reduzierenden Bedingungen (Ar/H2) liefert Nanokomposite bestehend aus Zinnnanopartikeln eingebettet in eine Kohlenstoff/Siliziumdioxid-Matrix. Weiterhin werden verschiedene metallhaltige Additive wie z.B. Carboxylate in der Zwillingspolymerisation verwendet und deren Eignung zur Darstellung von zinnhaltigen Nanokompositen sowie zur Legierungsbildung mit Zinn im Nanokomposit untersucht. Mit ausgewählten Materialien werden elektrochemische Messungen durchgeführt, wobei deren potentieller Einsatz als Anodenmaterial für Lithiumionen-Batterien geprüft wird (Kooperation BASF SE, Research Performance Materials GMV/P). Die Charakterisierung der neu synthetisierten Verbindungen und Nanokomposite erfolgt unter anderem mittels Einkristallröntgenstrukturanalyse, Röntgenpulverdiffraktometrie, NMR-Spektroskopie, Infrarotspektroskopie, Elektronenmikroskopie sowie thermischen Analysemethoden