376 research outputs found
Introduction to Surface-Mount Technology
In chapter 1, the surface-mount technology and reflow soldering technology are overviewed. A brief introduction is presented into the type of electronic components, including through-hole- and surface-mounted ones. Steps of reflow soldering technology are outlined, and details are given regarding the properties of solder material in this technology. The rheological behavior of solder pastes is detailed, and some recent advancements in addressing the thixotropic behavior of this material are summarized. The process of stencil printing is detailed next, which is the most crucial step in reflow soldering technology; since even 60–70% of the soldering failures can be traced back to this process. The topic includes the structures of stencils, discussion of the primary process parameters, and process optimization possibilities by numerical modeling. Process issues of component placement are presented. The critical parameter (process and machines capability), which is used extensively for characterizing the placement process is studied. In connection with the measurement of process capability, the method of Gage R&R (repeatability and reproducibility) is detailed, including the estimation of respective variances. Process of the reflow soldering itself is detailed, including the two main phenomena taking place when the solder is in the molten state, namely: wetting of the liquid solder due to surface tension, and intermetallic compound formation due to diffusion. Solder profile calculation and component movements during the soldering (e.g., self-alignment of passive components) are presented too. Lastly, the pin-in-paste technology (reflow solder of through-hole components) is detailed, including some recent advancements in the optimization of this technology by utilizing machine learning techniques
Survey and comparison of petroleum well electrologging tools
The principles used in the design of electrologging tools used in the petroleum industry are reviewed. Examples of tools and methods are taken from Gearhart Industries, Schlumberger Ltd and Western Atlas Ltd who are the three major electrologging companies accounting for 93% of the world market share. The survey and comparison of the tools in each of the category used both during the exploration and development stage of a well and reservoir are made. The results are presented and discussed. Furthermore an insight to the future of this industry is presented
Force sensing enhancement of robot system
At present there is a general industrial need to improve robot performance. Force feedback, which involves sensing and actuation, is one means of improving the relative position between the workpiece and the end-effector.
In this research work various causes of errors and poor robot performance are identified. Several methods of improving the performance of robotic systems are discussed.
As a result of this research, a system was developed which is interposed between the wrist and the gripper of the manipulator. This system integrates a force sensor with a micro-manipulator, via an electronic control unit, with a
micro-computer to enhance a robot system. The force sensor, the micromanipulator and the electronic control unit, were all designed and manufactured at the robotic centre of Middlesex Polytechnic.
The force feedback is provided by means of strain gauges and the associated bridge circuitry. Control algorithms which define the relationship between the force detected and the motion required are implemented in the software. The software is capable of performing two specific tasks in real time, these are:
1- Inserting a peg into a hole
2- Following an unknown geometric path
A rig was designed and manufactured to enable the robot to follow different geometric shapes and paths in which force control was achieved mainly by control of the micro-manipulator
Automated robotic inspection system for electronic manufacturing
An automated robotic inspection system for electronic manufacturing has been developed to identify pin defects of IC packages mounted on printed circuit boards using surface mount technology. The automated robotic inspection system consists of two robots, a computer, a CCD camera with frame gabber for image acquisition, and a customized windows program using neural network for on-line defect identification. Gray scale images of the pins on IC packages are acquired using ambient light. The images are filtered and formatted to appropriate size, so that Matlab neural network tool could be used. The images are used to train neural networks using Matlab\u27s Bayesian Regularization module. Optimal network was found to be a single-layer network with three outputs for each IC investigated. The weights and biases of each of the ICs investigated and the matrices of gray scale values for the IC images are saved as text files. A customized windows program uses these text files for on-line defect identification. The defect identification for the networks was found to be 100 percent for the two ICs investigated. The analysis and integration of an automated robotic inspection system for on-line monitoring of electronic manufacturing using neural networks is presented in this work
Investigation into Solder Joint Failure in Portable Electronics Subjected to Drop Impact
Ph.DDOCTOR OF PHILOSOPH
The design and implementation of a flexible manufacturing system for a surface mounting production line
A project report submitted to the Faculty of Engineering,
University of the Witwatersrand, Johannesburg, in partial
fulfillment of the requirements for the degree of Master of
Science in Engineering.The viability of introducing a Surface Mount
production line is chiefly determined by the
reliability characteristics of the components being
used. Surface Mount Technology (SMT) is entirely new
and although related to traditional through-hole
processes, requires different components, assembly
techniques and design methods. The purpose of the
literature survey is primarily to determine whether
surface mount components meet today's industrial
requirements with respect to their manufacturing
reliability and availability. A brief review of the
evolution of SMT is also presented. This study finds
that the implementation of SMT should be given highest
priority by manufacturing companies in order to
maintain their share of the marketplace.
Surface Mount Technology embodies a totally new
automated circuit assembly process, using a new
generation of electronic comporents: surface mounted
devices (SMDs). Smaller than conventional components,
SMDs are placed onto the surface of the substrate.
From this, the fundamental difference between SMD
assembly and convencional through-hole component
assembly arises; SMD component positioning is
relative, not absolute.
When a through-hole component is inserted into a pcb,
either the leads go through the hales or they don't.
An SMD, however, is placed onto the substrate surface,
it's position only relative to the solder lands, and
placement accuracy is therefore influenced by
variations in the substrate track pattern, component
size, and placement machine accuracy.
Other factors influence the layout of SMD substrates.
For example, will the board be a mixed-print ( a
combination of through-hole components and SMDs) or an
all-SMD design? Will SMDs be placed on one side of the
substrate or both? And there are process
considerations like what type of machine will place
the components and how will they be soldered?
This project describes in detail the processes
involved in setting up an SMT facility. A simulation
program was developed to verify the viability of these
processes. The simulation program was also applied to
an existing SMT facility and together with developed
optimization software, attempted to identify and
resolve some of the major problems. All this was
achieved, and the extent to which simulation could be
used as an efficient production tool, was highlighted.AC201
Langley Aerospace Research Summer Scholars
The Langley Aerospace Research Summer Scholars (LARSS) Program was established by Dr. Samuel E. Massenberg in 1986. The program has increased from 20 participants in 1986 to 114 participants in 1995. The program is LaRC-unique and is administered by Hampton University. The program was established for the benefit of undergraduate juniors and seniors and first-year graduate students who are pursuing degrees in aeronautical engineering, mechanical engineering, electrical engineering, material science, computer science, atmospheric science, astrophysics, physics, and chemistry. Two primary elements of the LARSS Program are: (1) a research project to be completed by each participant under the supervision of a researcher who will assume the role of a mentor for the summer, and (2) technical lectures by prominent engineers and scientists. Additional elements of this program include tours of LARC wind tunnels, computational facilities, and laboratories. Library and computer facilities will be available for use by the participants
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A pulse-width modulated, high reliability charge controller for small photovoltaic systems
This report presents the results of a development effort to design, test and begin production of a new class of small photovoltaic (PV) charge controllers. Sandia National Laboratories provided technical support, test data and financial support through a Balance-of-System Development contract. One of the objectives of the development was to increase user confidence in small PV systems by improving the reliability and operating life of the system controllers. Another equally important objective was to improve the economics of small PV systems by extending the battery lifetimes. Using new technology and advanced manufacturing techniques, these objectives were accomplished. Because small stand-alone PV systems account for over one third of all PV modules shipped, the positive impact of improving the reliability and economics of PV systems in this market segment will be felt throughout the industry. The results of verification testing of the new product are also included in this report. The initial design goals and specifications were very aggressive, but the extensive testing demonstrates that all the goals were achieved. Production of the product started in May at a rate of 2,000 units per month. Over 40 Morningstar distributors (5 US and 35 overseas) have taken delivery in the first 2 months of shipments. Initial customer reactions to the new controller have been very favorable
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