An approach for impression creep of lead-free microelectronic solders
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Authors
Anastasio, Onofrio A.
Subjects
Impression creep
Lead-free solders
Lead-free solders
Advisors
Dutta, Indranath
Date of Issue
2002-06
Date
Publisher
Monterey, California. Naval Postgraduate School
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Abstract
Currently, the microelectronics industry is transitioning from lead-containing to lead-free solders in response to legislation in the EU and Japan. Before an alternative alloy can be designated as a replacement for current Pb-Sn extensive testing must be accomplished. One major characteristic of the alloy that must be considered is creep. Traditionally, creep testing requires numerous samples and a long time, which thwarts the generation of comprehensive creep databases for difficult to prepare samples such as microelectronic solder joints. However, a relatively new technique, impression creep enables us to rapidly generate creep data. This test uses a cylindrical punch with a flat end to make an impression on the surface of a specimen under constant load. The steady state velocity of the indenter is found to have the same stress and temperature dependence as the conventional unidirectional creep test using bulk specimens. This thesis examines impression creep tests of eutectic Sn-Ag. A testing program and apparatus was developed and constructed based on a servo hydraulic test frame. The apparatus is capable of a load resolution of 0.01N with a stability of Å 0.1N, and a displacement resolution of 0.05mm with a stability of Å 0.1mm. Samples of eutectic Sn-Ag solder were reflowed to develop the microstructure used in microelectronic packaging. Creep tests were conducted at various stresses and temperatures and showed that coarse microstructures creep more rapidly than fine microstructures in the tested regime.
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Thesis
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Format
xvi, 39 p. : ill. (some col.) ;
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Distribution Statement
Approved for public release; distribution is unlimited.
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This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.