Publication Date

Fall 1996

Degree Type

Master's Project

Degree Name

Master of Science in Engineering (MSE)

Department

General Engineering

First Advisor

Dr. Guna Selvaduray

Abstract

A complete design of experiment was conducted to determine the optimum solder paste volume needed to establish reliable solder joints on tape ball grid arrays. The focus of the investigation was to optimize the solder paste volume, thus eliminating soldering defects such as shorting to ground plane due to solder wicking, bridging, and insufficient or open solder. Based on theoretical calculations for the solder paste volume, a matrix was developed and stencils were designed to deposit paste to the calculated volumes. Four parameters; solder paste volume, thickness and aperture openings in stencil design, reflow temperature, and pad geometries on the board, were considered in the experiment. Solder paste was deposited on printed circuit cards using stencil and squeeze operation, followed by placement of tape ball grid arrays on the boards by pick and place SMT equipment. The boards were then reflowed in forced convection ovens to reflow the joints. It was established that with other fine pitch surface mount devices loaded on board, a 6 mil thick stencil with 26 mil round pad openings provided the best paste matrix for reliable joint formation.

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