AVS 46th International Symposium
    Applied Surface Science Division Tuesday Sessions
       Session AS-TuP

Paper AS-TuP23
Time-Resolved Observations of Failure along Polymer-Glass Interfaces in Humid Environments@footnote 1@

Tuesday, October 26, 1999, 5:30 pm, Room 4C

Session: Poster Session
Presenter: J.T. Dickinson, Washington State University
Authors: J.T. Dickinson, Washington State University
N.Z. Hertelendy, Washington State University
S.C. Langford, Washington State University
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Adhesive interfaces play a critical role in microelectronic packaging, as well as in aerospace, automotive, and civil structures. The accelerated failure of strained adhesive bonds due to moisture is of considerable interest. By studying very small bonded zones (area @<=@ 1 mm@super 2@) one greatly enhances the influence of environmental attack, allowing for accelerated testing. To measure failure kinetics, we compare videotaped micrographic records of failure along ethylene vinyl acetate/soda lime glass interfaces in humid atmospheres with simultaneously acquired measurements of applied force. The interface is viewed through the glass substrate with an optical microscope. With increasing applied stress and relative humidity, the time required to produce an observable defect and the total time to failure decrease in a monotonic fashion. With increasing stress, the size of the crack at the onset of unstable critical crack growth also decreases. Visible crack growth prior to unstable failure is rate limited by the diffusion of water to the crack tip. The time required to produce a visible defect can be accounted for on the basis of chemically assisted failure, where the crack velocity depends directly on the change in surface energy due to water sorption (not transport limited). A quantitative model for the dependence of failure on stress and humidity is presented. @FootnoteText@ @footnote 1@This work is supported by the NSF Surface Engineering and Tribology Program under Grant CMS-98-00230.