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Preventing whiskers in electrodeposited tin for semiconductor lead frame applications

Preventing whiskers in electrodeposited tin for semiconductor lead frame applications A new pure tin process is described which produces a deposit with a crystal orientation combination that minimises whisker growth, particularly when used with a specific pre‐treatment process. A recommended etch depth of minimum 2.5 μ m has been shown to reduce whisker growth, particularly with thin (3 μ m) tin coatings. Crystal orientation is determined by X‐ray diffraction and the angles between adjacent crystal planes are calculated from the pattern produced. A minimum proportion of small angles is required for lowest whisker risk. Angles smaller than 22° have been shown to be critical. The predominant orientations of the deposits from new tin process are 101, 211, 112, and 312. This combination of orientations has 8 percent of angles in the critical range. A typical pure tin process with a high tendency for whiskering may have a texture of 431, 321, and 211 orientations, and this combination produces 65 percent of angles smaller than 22°. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Circuit World Emerald Publishing

Preventing whiskers in electrodeposited tin for semiconductor lead frame applications

Circuit World , Volume 30 (2): 5 – Jun 1, 2004

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Publisher
Emerald Publishing
Copyright
Copyright © 2004 Emerald Group Publishing Limited. All rights reserved.
ISSN
0305-6120
DOI
10.1108/03056120410512118
Publisher site
See Article on Publisher Site

Abstract

A new pure tin process is described which produces a deposit with a crystal orientation combination that minimises whisker growth, particularly when used with a specific pre‐treatment process. A recommended etch depth of minimum 2.5 μ m has been shown to reduce whisker growth, particularly with thin (3 μ m) tin coatings. Crystal orientation is determined by X‐ray diffraction and the angles between adjacent crystal planes are calculated from the pattern produced. A minimum proportion of small angles is required for lowest whisker risk. Angles smaller than 22° have been shown to be critical. The predominant orientations of the deposits from new tin process are 101, 211, 112, and 312. This combination of orientations has 8 percent of angles in the critical range. A typical pure tin process with a high tendency for whiskering may have a texture of 431, 321, and 211 orientations, and this combination produces 65 percent of angles smaller than 22°.

Journal

Circuit WorldEmerald Publishing

Published: Jun 1, 2004

Keywords: Semiconductors; Alloys; Electrodeposition

References