Search

Optimal performance of a MEMS device often requires hermetic packaging to enable proper functionality throughout the device lifetime. Solid-Liquid Interdiffusion (SLID) bonding is an attractive way to encapsulate MEMS devices in wafer level since it provides: i) possibility to use low temperature metal bonding process, ii) metallic seal rings don't take much out of the valuable surface area, iii) ductile metals can adopt mechanical and thermo-mechanical stresses and iv) metals have lower gas permeability compared to polymer or glass based sealing materials. Although metal bonding utilizing different binary metal-systems is becoming more common there is only a limited amount of information available on the defects of the bond and their effect on the reliability. In this work four typical defects of AuSn and CuSn seal rings, which are used for wafer-level hermetic bonding for MEMS resonators, are identified as non-uniform plating thickness, bubbles in electrodeposited metallizations, voids in bonded seal rings, and excessive amount of tin. Shear test was used to compare the mechanical properties of the interconnections in both material systems, and to evaluate the effects of different defects on failure mechanisms. In addition, the effects of thermo-mechanical treatments on the reliability performance are also studied. [ABSTRACT FROM PUBLISHER]

In this study, reliability assessment of the IMC layer of the ultra-fine-pitch FC-BGA(Flip-Chip Ball Grid Array) is conducted. The samples are prepared to reveal the differences in the adhesion forces of the IMC layer by dissimilarly establishing each plating thickness for surface finish(Ni/Pd/Au). The hardness and thickness of a P-rich Ni layer, which is known as the weakest section in ENPIG surface, are measured using the nano-indentation and TEM analysis. The degree of adhesion of the IMC layer under each experimental condition is evaluated and the metal plate shear test is performed for verification. The results showed significant correlations between the hardness and thickness of the IMC later and the high fraction defectives of the brittle fractures whose IMC layer had low hardness. [ABSTRACT FROM PUBLISHER]

The continuous trend towards high density and miniaturization of electronic devices involves the use of multiple reflow processes in assembling technologies for second level of interconnections in electronic packaging hierarchy. According to the “4P” Soldering Model concept (4PSMC), considering the Pad-Paste-Pin-Process elements as Key Process Input Variables (KPIV), the solder joints are the result of KPIV synergistically interactions and correlations with consequences over their microstructure. In the paper, taking into consideration the cooling rate influence over intermetallic compounds (IMC) formation and microstructure, there was described the investigations over electrical and mechanical properties of solder joints resulted from multiple reflow Vapor Phase Soldering (VPS) process, in terms of 4PSMC. Maintaining the pad, pin and paste of KPIV as references measurements of solder joints resistances and shear forces were perform as function of VPS process's number for two values of cooling rate, respectively IMC microstructures and stereofractography studies. The results of the studies performed and presented in the paper will be use for improving process control in order to assure the solder joints reliability, to minimize losses on VPS lines, to reduce defects number and rework time. [ABSTRACT FROM PUBLISHER]

The work presented in this paper is part of a more extensive study the aim of which is to build a complete simulation of the clinching process and subsequent resistance tests. This paper focuses on finite element analyses -that are performed with the ABAQUS™ code- of the resistance of clinched points to shear test. These analyses are run up to propagation of metal sheet fracture. A simplified procedure is proposed to identify the fracture initiation and propagation models that are used to simulate this failure process. This identification process is based on Lemaitre’s ductile damage model. The numerical simulations of a shear test have been compared to experimental results. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

Experimental shear tests and Finite Element Modeling (FEM) have been used to study the generation of bonding during the multi-pass drawing of multifilamentary wire, focusing on the experimental conditions and materials of interest to composite superconductor manufacture. The wires were of two kinds: (1) a simple cylindrical monocore arrangement consisting of a Nb7.5%Ta core inside a Cu can (or sleeve), (2) a six-around-one restack of the monocores. For the modeling a thermo-mechanical, elasto-plastic, finite-element model was employed. Two kinds of simulations were performed: (1) the initial state of the billet was assumed to be without bonding. The FEM simulation was then performed, and from this the normal pressure, deformation, and temperature at the core/sleeve interface were calculated; (2) a pressure welding model was used to estimate the bonding stress generated at the interface by the multi-pass drawing process. On the experimental side, the Cu-clad Nb monocore “billet” was drawn to certain size, restacked into a Cu can to form a 7 restack multifilamentary billet, and then drawn to small size. High resolution scanning electron microscopy was used to observe the characteristics of the Nb/Cu and Cu/Cu interfaces and mechanisms for the observed interfacial bonding were proposed. Furthermore, specially designed shear tests were carried out to determine the interfacial shear load. The results of these led to calculations of the interfacial shear stress (i.e. the bonding stress at the interfaces), the results of which were compared with the FEM predictions in order to establish the validity of the FEM model. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]