Laser drilling improving circuit board manufacturing

We reported here a novel technique for laser high speed drillings on Printed Circuit Boards (PCBs). A CNC solid laser based system is developed to drill through and blind vias as an alternative to mechanical drilling. The system employs an Acousto-Optic Q-switched Nd: YAG laser, a computer control system and an X-Y moving table which can handle up to 400 x 400 mm PCB. With a special designed cavity the laser system works in a pulsed operation in order to generate pulses with width down to 0.5 mu s and maximum peak power over 10kW at 10k repetition rate. Delivered by an improved optical beam transforming system, the focused laser beam can drill hobs including blind vias on PCBs with diameter in the range of 0.1 - 0.4 mm and at up to 300 - 500 vias per second (depending on the construction of PCBs). By means of a CNC X-Y moving system, laser pulses with pulse-to-pulse superior repeatability can be fired at desired location on a PCBs with high accuracy. This alternative technology for drilling through or blind vias on PCBs or PWBs (printed wiring boards) will obviously enhance the capability to printed boards manufacturing.

Mechanics of a grip system of three-key-board hydraulic tongs developed for offshore oil pipe lines

This paper carries out the analysis of mechanics of a grip system of three-key-board hydraulic tongs developed for offshore oil pipe lines which has been successfully used in oil fields in China. The main improvement of this system is that a lever frame structure is used in the structural design, which reduces greatly the stresses of the major components of the oil pipe tongs. Theoretical analysis and numerical calculation based on thirteen basic equations developed Show that the teeth board of the tongs is not easy to slip as frequently happens to other systems and is of higher reliability.

On-Board Experimental Study Of Bubble Thermocapillary Migration In A Recoverable Satellite

An on-board space experiment of bubble thermocapillary migration was performed in the Chinese 22nd recoverable satellite in 2005. Silicone oil of nominal viscosity 5cSt was used as the continuous phase in the experiment. Air bubbles were injected into the liquid in the same direction as the constant temperature gradient in the liquid. The velocities of bubbles were obtained by recording the paths of the bubbles. The results indicate that the scaled velocity of bubbles decreases with an increase of the Marangoni number extended to 9288, which agrees with the results of previous space experiments and numerical simulation. In addition, the interaction between two bubbles was also observed in the space experiment. The trajectories and the velocities of the bubbles were obtained. The two-bubble experiment results are also consistent with the theoretical analysis.

Effects of Thermocapillary Convection on the Growth Process in Industrial 8-inch Silicon Czochralski Growth

Czochralski (CZ) crystal growth process is a widely used technique in manufacturing of silicon crystals and other semiconductor materials. The ultimate goal of the IC industry is to have the highest quality substrates, which are free of point defect, impurities and micro defect clusters. The scale up of silicon wafer size from 200 mm to 300 mm requires large crucible size and more heat power. Transport phenomena in crystal growth processes are quite complex due to melt and gas flows that may be oscillatory and/or turbulent, coupled convection and radiation, impurities and dopant distributions, unsteady kinetics of the growth process, melt crystal interface dynamics, free surface and meniscus, stoichiometry in the case of compound materials. A global model has been developed to simulate the temperature distribution and melt flow in an 8-inch system. The present program features the fluid convection, magnetohydrodynamics, and radiation models. A multi-zone method is used to divide the Cz system into different zones, e.g., the melt, the crystal and the hot zone. For calculation of temperature distribution, the whole system inside the stainless chamber is considered. For the convective flow, only the melt is considered. The widely used zonal method divides the surface of the radiation enclosure into a number of zones, which has a uniform distribution of temperature, radiative properties and composition. The integro-differential equations for the radiative heat transfer are solved using the matrix inversion technique. The zonal method for radiative heat transfer is used in the growth chamber, which is confined by crystal surface, melt surface, heat shield, and pull chamber. Free surface and crystal/melt interface are tracked using adaptive grid generation. The competition between the thermocapillary convection induced by non-uniform temperature distributions on the free surface and the forced convection by the rotation of the crystal determines the interface shape, dopant distribution, and striation pattern. The temperature gradients on the free surface are influenced by the effects of the thermocapillary force on the free surface and the rotation of the crystal and the crucible.

Indole and carbazole alkaloids from Glycosmis montana with weak anti-HIV and cytotoxic activities

A diprenylated indole, (E)-3-(3-hydroxymethyl-2-butenyl)-7-(3-methyl-2-butenyl)-1H-indole (1), and six known carbazole alkaloids were isolated from the twigs and leaves of Glycosmis montana Pierre (Rutaceae). Their structures were determined on the basis of analysis of spectral evidence including 1D and 2D NMR and MS. The alkaloids (1-3) exhibited weak to moderate take in vitro inhibitory activity against HIV replication in C8166 cells, and they (as well as carbalexine A and B) had cytotoxic activity against the human leukaemia cell line CCRF-CEM. (c) 2005 Elsevier Ltd. All rights reserved.