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How Much Rework Is Too Much The Effects of Solder Joint Rework on Platedthrough Holes in Multilayer Printed Wiring Boards

How Much Rework Is Too Much The Effects of Solder Joint Rework on Platedthrough Holes in... In the assembly process of high reliability printed wiring boards PWBs, rework cycles seem to be an unfortunate fact of life. The question repeatedly arises as to how many times a solder joint incorporating platedthroughholes PTHs can be reworked without degrading the configuration. By performing a controlled experiment, the authors were able to answer that question and make recommendations as to the limits that should be placed on the number of reworks. They were further able to look at the following factors operators, board type, number of layers and solder temperature to determine which were the most significant in determining limits to the number of rework cycles. The results showed that the more layers the board contained, the more at risk the PTH was to reworkinduced defects. This perhaps defies conventional wisdom that the board type or temperatures were the driving contributors. The increased number of board layers corresponds to thinner dielectric layers. The experimental results were repeated in a theoretical review using a finite element analysis FEA model that was developed showing the thermally induced stresses in the solder joint and PTH region. For multilayer boards, it is recommended that rework be limited to three cycles. The present work shows that there is evidence of degradation by the fifth cycle on boards with thinner dielectric 10layer board, dielectric thickness 0.008 in.. By limiting the number of reworks, the risk of inducing failure mechanisms into PWAs printed wiring assemblies is dramatically reduced. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Soldering & Surface Mount Technology Emerald Publishing

How Much Rework Is Too Much The Effects of Solder Joint Rework on Platedthrough Holes in Multilayer Printed Wiring Boards

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Publisher
Emerald Publishing
Copyright
Copyright © Emerald Group Publishing Limited
ISSN
0954-0911
DOI
10.1108/eb037888
Publisher site
See Article on Publisher Site

Abstract

In the assembly process of high reliability printed wiring boards PWBs, rework cycles seem to be an unfortunate fact of life. The question repeatedly arises as to how many times a solder joint incorporating platedthroughholes PTHs can be reworked without degrading the configuration. By performing a controlled experiment, the authors were able to answer that question and make recommendations as to the limits that should be placed on the number of reworks. They were further able to look at the following factors operators, board type, number of layers and solder temperature to determine which were the most significant in determining limits to the number of rework cycles. The results showed that the more layers the board contained, the more at risk the PTH was to reworkinduced defects. This perhaps defies conventional wisdom that the board type or temperatures were the driving contributors. The increased number of board layers corresponds to thinner dielectric layers. The experimental results were repeated in a theoretical review using a finite element analysis FEA model that was developed showing the thermally induced stresses in the solder joint and PTH region. For multilayer boards, it is recommended that rework be limited to three cycles. The present work shows that there is evidence of degradation by the fifth cycle on boards with thinner dielectric 10layer board, dielectric thickness 0.008 in.. By limiting the number of reworks, the risk of inducing failure mechanisms into PWAs printed wiring assemblies is dramatically reduced.

Journal

Soldering & Surface Mount TechnologyEmerald Publishing

Published: Jan 1, 1995

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