Populated Printed Circuit Boards Research Articles

A Closed-Form Expression for Estimating Radiated Emissions From the Power Planes in a Populated Printed Circuit Board

An expression for the maximum intensity of radiated emissions from a rectangular power bus structure has been derived based on an analytical cavity-resonator model. The effect of components mounted on the board is modeled by modifying the propagation constant of the waves within the power bus structure. The radiated field intensity is calculated using the equivalent magnetic current around the edges of the power bus structure together with the modified propagation constant. Measurements of a populated test board show that the derived closed-form expression estimates the level of the maximum radiation intensity with reasonable accuracy

Designed experiments to investigate the solder joint quality output of a prototype automated surface mount replacement system

A robotic remanufacturing system at Rensselaer has been developed to replace fine pitch surface mounted components on a populated printed circuit board (PCB). The performance goal is to maximize the quality of the solder joint output to optimize the system's throughput. The purpose of this paper is to present the process parameters determined for obtaining a good solder joint with the rework cell. Developed here and to show an analysis of the solder joint quality obtained from the developed system. Maximizing the rate of correctly reworked components by the system is not chosen as a goal for measuring the system's performance. This is because rework is a low volume process and the cell being used, is an experimental prototype system.

Thermal characterization of chip packages-evolutionary development of compact models

The expanded R/sub jc/ methodology, first proposed in 1989, makes it possible to extend the use of this common figure-of-merit to chip packages with nonisothermal cases. This proposal spurred considerable debate and contributed to renewed efforts to provide "compact" thermal models of single chip packages, for preliminary design, as well as for detailed numerical simulation of populated printed circuit boards. This presentation offers a review of the development of this modified R/sub jc/ methodology and its efficacy in replicating the chip, or junction, temperature predicted by detailed numerical simulation.

A computer aided cost estimation system for BGA/DCA technology

The last decade has seen an increasing demand for smaller and more densely populated printed circuit boards (PCBs). This is partly due to the market driven need within the electronics industry of reducing the size of products while concurrently enhancing their capabilities. Consequently, the electronics packaging industry is relying upon area array technologies such as Ball Grid Array (BGA) and Direct Chip Attach (DCA) as possible replacements for the traditional peripherally leaded surface mount packaging formats. However, since these technologies are still in their nascent stage, the cost benefits obtained from them need to be quantified in an effort to aid in justigying their use. This paper describes a Computer Aided Cost Estimation (CACE) system which has been developed to justify the use of BGA/DCA devices.

Stress Analysis of Printed Circuit Boards With Highly Populated Solder Joints and Components: A Micromechanics Approach

The single most difficult aspect for thermo-mechanical analysis at the board level lies in to an accurate accounting for interactions among boards and small features such as solder joints and secondary components. It is the large number of small features populated in a close neighborhood that proliferates the computational intensity. This paper presents an approach to stress analysis for boards with highly populated small features (solder joints, for example). To this end, a generalized self-consistent method, utilizing an energy balance framework and a three-phase composite model, is developed to obtain the effective properties at board level. The stress distribution inside joints and components are obtained through a back substitution. The solutions presented are mostly in the closed-form and require a minimum computational effort. The results obtained by present approach are compared with those by finite element analysis. The numerical calculations show that the proposed micromechanics approach can provide reasonably accurate solutions for highly populated printed circuit boards.

Monte Carlo thermal optimization of populated printed circuit board

The methodology and results of a Monte Carlo optimization of component placement on a printed circuit board are presented. The overall reliability of the component mix on the printed circuit board is the criterion of optimality. Arrhenius relations are used to quantify the effect of temperature on the component failure rate. The finite element code called ANSYS is used to determine the temperature distribution in two conductively cooled printed circuit boards. The various strategies of the Monte Carlo annealing and cluster optimization methods and the effect of the relevant parameters on board reliability are discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Centrifugal Cleaning—A New Technology for Cleaning Printed Circuit Boards and Hybrid Circuits

Cleaning or defluxing of populated printed circuit boards has become a very difficult problem as component stand‐off clearances have become smaller, line spacings tighter, and solvents limited because of the CFC/ozone issue. This paper discusses the new technology of Centrifugal cleaning where ACCEL Energy™ is harnessed inside an enclosed chamber to provide significant cleaning benefits. Among these benefits are: superior washing, effective rinsing, superior drying, reduced solvent consumption by orders of magnitude, small footprint, and compatibility with H2O, saponifiers, chlorocarbons, fluorocarbons and terpenes.