Characterization of Thermo-Mechanical Damage in Tin and Sintered Nano-Silver Solders

abstract: Increasing density of microelectronic packages, results in an increase in thermal and mechanical stresses within the various layers of the package. To accommodate the high-performance demands, the materials used in the electronic package would also require improvement. Specifically, the damage that often occurs in solders that function as die-attachment and thermal interfaces need to be addressed. This work evaluates and characterizes thermo-mechanical damage in two material systems – Electroplated Tin and Sintered Nano-Silver solder. Tin plated electrical contacts are prone to formation of single crystalline tin whiskers which can cause short circuiting. A mechanistic model of their formation, evolution and microstructural influence is still not fully understood. In this work, growth of mechanically induced tin whiskers/hillocks is studied using in situ Nano-indentation and Electron Backscatter Diffraction (EBSD). Electroplated tin was indented and monitored in vacuum to study growth of hillocks without the influence of atmosphere. Thermal aging was done to study the effect of intermetallic compounds. Grain orientation of the hillocks and the plastically deformed region surrounding the indent was studied using Focused Ion Beam (FIB) lift-out technique. In addition, micropillars were milled on the surface of electroplated Sn using FIB to evaluate the yield strength and its relation to Sn grain size. High operating temperature power electronics use wide band-gap semiconductor devices (Silicon Carbide/Gallium Nitride). The operating temperature of these devices can exceed 250oC, preventing use of traditional Sn-solders as Thermal Interface materials (TIM). At high temperature, the thermomechanical stresses can severely degrade the reliability and life of the device. In this light, new non-destructive approach is needed to understand the damage mechanism when subjected to reliability tests such as thermal cycling. In this work, sintered nano-Silver was identified as a promising high temperature TIM. Sintered nano-Silver samples were fabricated and their shear strength was evaluated. Thermal cycling tests were conducted and damage evolution was characterized using a lab scale 3D X-ray system to periodically assess changes in the microstructure such as cracks, voids, and porosity in the TIM layer. The evolution of microstructure and the effect of cycling temperature during thermal cycling are discussed.Dissertation/ThesisDoctoral Dissertation Materials Science and Engineering 201

Mechanical Property Evaluation of Electrodeposited Nanocrystalline Metals by Micro-testing

Electrodeposition is a very important technology in the fabrication of micro-components for micro-electro-mechanical systems (MEMS) or integrated circuits. Evaluations of the materials used in these devices as 3D components should be conducted using micro-sized specimens due to the sample size effect on the practical use of the components. Nanocrystalline metals could be deposited using an electrodeposition method with supercritical CO2 emulsion. Our experiment on the micro-specimens provides information on micro-mechanical testing of electrodeposited metals including the effect of sample size, grain size, and anisotropic structures on mechanical properties. In this chapter, recent studies on crystal growth in electrodeposition of metals and its evaluation using micron-sized testing will be presented

The properties and the effect of operating parameters on nickel plating (review)

The energy required in an electroplating process and the material costs are important considerations in product manufacturing. The most important plating criteria, however, are quality and the uniformity of the deposited metals. The nickel plating process is used extensively for decorative, engineering, and electroforming purposes. Because of the appearance and other properties of the electrodeposited material, nickel deposition can be varied, over a wide range, by controlling the composition and the operating parameters of the plating solution. Decorative applications account for about 80% of the nickel consumed in plating; 20% is consumed for engineering and electroforming purposes. Autocatalytic (electroless) nickel plating processes are commercially important but are outside the scope of this review. In this review, the basic facts of nickel electroplating processes, thickness test and methods, are discussed. The properties of nickel and the different effects of the operating parameters on nickel plating, together with the simulation and design tools, are also reviewed. Simulation tools can help to obtain better plating results. Non-destructive techniques to evaluate the coatings on a microstructural and the technical evaluation with TEM, SEM, XRD and other techniques were also reviewed

Cu/Ni/Au multilayers by electrochemistry: A crucial system in electronics - A critical review

International audienc

Modeling electrodeposited NI80Fe20 and the electrolytes boundary conditions' influence on the mechanical properties, 2009

A Micro-electro-mechanical system (MEMS) gas turbine generator is currently under development. This device uses electrodeposited NisoFezo (thin film) as a structural material in the high speed rotating micro-generator used to convert mechanical energy to electrical energy. For structural applications, the materials' mechanical properties are vital for the design. However, for electrodeposited NisoFezo, currently, there is not any published data regarding its mechanical Properties. Therefore, the goal of this research is to model the mechanical properties of electrodeposited Ni80Fe20 as a function of three critical electrolytes variables: agitation, current density, and temperature. In achieving this goal, a typical off-the- shelf nickel iron electroplating solution was used to fabricate the Ni80Fe2~ test specimens. A 2k Factorial Analysis and Design of Experiments was used to identify the critical variables and boundary conditions, and a new Micro/Nano Testing System was designed and developed to measure the mechanical properties. Finally, a linear regression analysis was conducted to model Young's Modulus and Ultimate Strength as a function of the three critical electrolytes variables

Conductive Copper Paste for Crystalline Silicon Solar Cells

In photovoltaic industries, the main technique of metallization is screen printing with silver pastes due to its simple and quick process. However, the expensive price of silver paste is one of the barriers to the production of low-cost solar cells. Therefore, the most focused target in photovoltaic research is the decreasing consumption of silver paste or substitute silver for other materials. As a proper candidate, copper has been researched by many institutes and companies since it has a similar conductivity with silver even though the price is inexpensive. To apply copper as a contact for solar cells, the plating technique has been actively researched. However, copper paste, which was mainly developed for integrated circuit applications, has been recently researched. Mostly, copper paste was developed for the low-temperature annealing process since copper tends to oxidize easily. On the other hand, firing type copper paste was also developed by coating copper particles with a barrier layer. This chapter discusses recent development of copper paste for the application of solar cells and its appropriate annealing conditions for better electrical properties. Also, the light I-V characteristics of copper paste on the solar cells in other research papers are summarized as well

Ge Nanowires Anode sheathed with Amorphous Carbon for Rechargeable Lithium batteries

Interdisciplinary School of Green EnergyThe composite electrode composed of single crystalline Ge NWs sheathed with amorphous carbon showed excellent electrochemical properties of large reversible capacity, high coulombic efficiency, excellent rate capability and stable cycle performance. c-Ge NWs synthesized by using thermal decomposition of C2H2 gas at 700 °C under Ar atmosphere after SLS (solution-liquid-solid) growth were found to have good performance during cycling with Li. The rate capability for charging was shown reversible capacity of 963 mAh/g with a coulombic efficiency of 90% and 700 mAh/g at the rate of 6C (= 4800mA/g). Capacity retention after 100 cycles was 72% at the rate of 0.5C. The improved electrochemical performance of c-Ge-NWs fabricated in our experiment was attributed to the formation of amorphous Ge NWs during cycling and a homogenous carbon coating on Ge NWs. Thus, these results suggest that the use of nanowires structure can be promising for alloy anode materials in lithium ion batteries