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This work investigates the effects of Sb on IMC formation and mechanical properties of Sn-3.5Ag-0.7Cu lead-free solder joints. In this work, SEM is used to measure the thickness of intermetallic layer and observe the microstructural evolution of solder joint. The IMC phases are identified by EDX and XRD. Results show that there is a significant drop in IMC thickness when Sb is about 0.8 wt%. The tensile strength of the solder joints can be slightly improved by adding a small amount of Sb in Sn-Ag-Cu alloy system.

We present an optimized face-down die attachment for single-mode ridge-waveguide laser diodes (LDs) using Au80Sn20 solder. Based on this improved technique, a bonding process window has been determined through microstructure and mechanical investigation of the solder joint, and electro-optical characterization of LDs. Metallographical investigation shows that the solder joint comprises of a layer of /spl delta/ phase near the LD/solder and solder/heatsink interfaces, /spl zeta/ phase at the center of the solder joint, and a layer of (Au, Ni)Sn intermetallic compound (IMC) at the solder/heatsink interface. The /spl delta/ phase shifted to the interfaces, while /spl zeta/ phase Au/Sn compound is remaining at the center of the joint, is postulated by the lower surface tension in /spl delta/ phase. Mechanical shear testing demonstrates good bonding integrity, which meets the requirements specified by MIL-STD-883C. Fracture surface characterization shows brittle fracture occurring within the LD, at the GaAs/SiN interface. This optimized bonding process can achieve optical improvement of 2.5-3/spl times/ compared to unbonded LDs due to good thermal management.

In this paper, direct adaptive neural network control is studied for a class of multi-input and multi-output (MIMO) nonlinear systems based on input-output model with unknown inter connections between subsystems. The proposed adaptive algorithm is very simple and easy to implement. By finding a unitary orthogonal matrix to tune the NN weights, the closed-loop system is proved to be semi-globally uniformly ultimately bounded (SGUUB). The control performance of the closed-loop system is guaranteed by suitably choosing the design parameters.

The effects of antimony on the microstructural evolution and the intermetallic compound (IMC) growth of Sn-3.5Ag-O.7Cu lead-free solder joints were investigated in this work. To investigate the element diffusion and the growth kinetics of IMC formation in solder joint, isothermal aging test is performed at temperatures of 100°C, 150°C, and 190°C respectively. Optical and scanning electron microscope (OM and SEM) were used to measure the thickness of intermetallic layers and observe the microstructure evolution of solder joint. The IMC phases were identified by energy dispersive X-ray (EDX) and X-ray diffraction (XRD). Results show that the thickness of IMC layer reduces and the grain size decreases with the increase in antimony composition. The activation energy and growth rate of the IMC formation were determined. Results reveal that adding antimony in Sn-3.5Ag-0.7Cu solder system could increase the activation energy, and thus reduce the atomic diffusion rate so as to inhibit the excessive growth of IMC. It is also observed that the fme particles precipitated along the grain boundary of IMC increase with the increase of Sb composition. Based on the observation of the microstructural evolution of the solder joints, a grain boundary pinnimg mechanism for the inhibition of IMC growth due to Sb addition was proposed.

Delaminations of the embedded passive components are often associated with reliability problems. Understanding the delamination can help us quickly identify the failure cause at an early stage of the failure analysis. In this work, defects of buried capacitors have been detected by use of scanning acoustic microscopy (SAM). The results show that SAM can be a powerful analytical tool for the nondestructive evaluation of delaminations in buried passive components. T-scan is an effective method for determining the existence of the internal defects, and TAMI-scan is shown to be capable of detecting the location and size of the delamination and void.

The effects of Sn diffusion, Ag and Pd dispersion and intermetallic compound growth on the shear fatigue of solder joints between thick film mixed bonded Pd-Ag conductor and 62Sn-36Pb-2Ag solder are investigated. The samples were prepared by assembling leadless ceramic chip carrier (LCCC) passive components on a 96% Al/sub 2/O/sub 3/ substrate and ageing at 150/spl deg/C for varying times. Microstructural analysis reveals that the intermetallic compounds (IMC) Pd/sub 3/Sn/sub 2/, Pd/sub 3/Sn, Pd/sub 2/Sn, PdSn, PdSn/sub 2/, PdSn/sub 4/, Ag/sub 5/Sn, Ag/sub 3/Sn, PbPd/sub 3/, and Pb/sub 3/Pd/sub 5/ are formed after ageing. X-ray dot maps demonstrate that the longer the ageing time, the more serious the Ag and Pd dispersion into the solder and the Sn diffusion into the conductor. It is noted that the Sn diffuses to the interface of the substrate/conductor after 120 hours ageing. Shear strength tests at varying strain rates show that adhesion strength decreases with prolonged ageing time. Shear cycling tests indicate that the solder joint fatigue lifetime depends on the Ag and Pd diffusion range, and especially on Sn diffusion into the thick film conductor. These results mean that the more serious the Sn and Ag interdiffusion, and the more IMC is formed in the solder joint (which can be due to prolonged high temperature storage or long term operation of SMT assemblies), the more sensitive is the solder joint to stress, eventually leading to fatigue failure. It is argued that volume change and increased brittleness due to intermetallic formation, and conductor layer volume swelling due to Sn diffusion are major factors in the decrease of solder joint fatigue lifetime and shear strength.

The frequency selective surfaces (FSS) on both normally and in-plane biased ferrite slab is analyzed using the full-wave moment method solution in this paper. The extra degree of freedom offered by the biased ferrite can be used to tune the resonance characteristics of FSS. Numerical results show that the reflection band center frequencies can be adjusted by several gigahertz.