Initial bond formation in thermosonic gold ball bonding on aluminium metallization pads

The morphological features of lift-off footprints on the aluminium metallization pads were investigated to gain an understanding of the effects of bonding parameters on formation of initial bonds during thermosonic gold ball bonding. The obtained results showed that metallurgical bonding initiated at the peripheral areas of the contact area situated along the direction of ultrasonic vibration. Those areas extended inwards with an increase in ultrasonic power. Both the external bonded area and central non-bonded area increased with increasing bonding force. Based on the evolution of footprints, the bonding models were proposed, and the effects of the bonding parameters on the formation of initial bonds were discussed.     

复合材料深度方向超声C扫描检测技术

介绍一种基于超声传播时域特性的深度方向超声C扫描成象检测技术,一次扫描可以同时获取被测材料内部若干层的扫描检测图象。     

Decomposed control design for non-stationary plants subject to disturbances

This paper combines the block (Luk'yanov and Utkin 1982, 1998), sliding mode and high gain control techniques (Utkin 1992) to form a new decomposed control law suitable for general multivariable non-stationary plants. Different versions of the control law are developed with various dependencies on plant parameters and state variables. The new control law is demonstrated by simulation of its application to an electrical drive employing a dc motor with controlled flux.     

Spatial distribution of doubly scattered polarized laser radiation in the focal plane of a lidar receiver

Depolarization lidars are widely used to study clouds and aerosols because of their ability to discriminate between spherical particles and particles of irregular shape. Depolarization of cloud backscattered radiation can be caused also by multiple scattering events. One of the ways to gain information about particle parameters in the presence of strong multiple scattering is the measurement of radial and azimuthal dependence of the polarization patterns in the focal plane of receiver. We present an algorithm for the calculation of corresponding polarized patterns in the frame of double scattering approximation. Computations are performed for various receiver field of views, for different parameters of the scattering geometry, e.g., cloud base and sounding depth, as well as for different values of cloud particle size and refractive index. As the spatial distribution of cross-polarized radiation is of cross shape and rotated at 45 degrees with respect to laser polarization, the use of a properly oriented cross-shaped mask in the receiver focal plane allows the removal of a significant portion of the depolarized component of the backscattered radiation produced by double scattering. This has been verified experimentally based on cloud depolarization measurements performed at different orientations of the cross-shaped mask. Results obtained from measurements are in agreement with model predictions.     

Tomographic bioluminescence imaging with varying boundary conditions

Three-dimensional bioluminescence imaging is an emerging technique that can be used to monitor molecular events in intact living systems. The inverse problem of 3D bioluminescence imaging does not have a unique solution because it requires reconstruction of a 3D source function from a 2D one. A novel approach that addresses this problem with the aid of a simple experimental setup and solves the uniqueness problem of the solution for a monochromatic measurement set is suggested here. The approach is verified numerically by reconstructing bioluminescent objects of various shapes embedded inside highly scattering media, such as biologi?al tissue.     

Femtosecond pulse shaping adds a new dimension to mass spectrometry

Phase-shaped femtosecond laser pulses and mass spectrometry were implemented as a tool for improving molecular identification. We demonstrate that the specific lines in the mass spectra of several chemical warfare simulants are sensitive to the phase characteristics of the incident laser field. The deviation in the relative yield of fragment ions observed upon pulse shaping (enhancement or suppression) adds a new dimension to mass spectrometry that improves molecular identification and can be used to quantitatively analyze mixtures of isomers.     

Microstructural evolution of 96.5Sn–3Ag–0.5Cu lead free solder reinforced with nickel-coated graphene reinforcements under large temperature gradient

In this study, 96.5Sn–3Ag–0.5Cu (SAC305) lead-free composite solder containing graphene nanosheets (GNS) decorated with Ni nanoparticles (Ni-GNS) was prepared using a powder metallurgy method. A lab-made set-up and a corresponding Cu/solder/Cu sample design for assessing thermo-migration (TM) was established. The feasibility of this setup for TM stressing using an infrared thermal imaging method was verified; a temperature gradient in a solder joint was observed at 1240 K/cm. Microstructural evolution and diffusion of Cu in both plain and composite solder joints were then studied under TM stressing conditions. Compared to unreinforced SAC305 solder, the process of diffusion of Cu atoms in the composite solder joint was significantly reduced. The interfacial intermetallic compounds (IMCs) present in the composite solder joint also provide a more stable morphology after the TM test for 600 h. Furthermore, during the TM test, the Ni-GNS reinforcement affects the formation, migration and distribution of Ni–Cu–Sn and Cu–Sn IMCs by influencing the dissolution rate of Cu atoms.     

Inverse problem in optical diffusion tomography. IV. Nonlinear inversion formulas

We continue our study of the inverse scattering problem for diffuse light. In contrast to our earlier work, in which we considered the linear inverse problem, we now consider the nonlinear problem. We obtain a solution to this problem in the form of a functional series expansion. The first term in this expansion is the pseudoinverse of the linearized forward-scattering operator and leads to the linear inversion formulas that we have reported previously. The higher-order terms represent nonlinear corrections to this result. We illustrate our results with computer simulations in model systems.