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Toughened and Higher Fracture Crack-Resistant Polyimide

IP.com Disclosure Number: IPCOM000041873D
Original Publication Date: 1984-Mar-01
Included in the Prior Art Database: 2005-Feb-03
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Gupta, MR: AUTHOR

Abstract

Crack propagation in polyimide (PI) films can be lessened by incorporating about 10-25% high molecular weight PI. A residual stress, due mainly to thermal expansion difference, of 5000-7000 psi is present on PI film on a substrate due to various process steps (such as, for example, via hole generation). There are always stress concentrations in the PI film which raise the stress to the point where the residual stress is the same as the yield strength of the material. Also, there will be some small cracks or crazes, either sharp or rounded, produced near the vias or at the point of the defects. The problem of rapid fracture crack propagation can be alleviated by incorporating a small (10-25%) fraction of a very high molecular weight PI of the same chemistry (or of different chemistry if miscible).

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Toughened and Higher Fracture Crack-Resistant Polyimide

Crack propagation in polyimide (PI) films can be lessened by incorporating about 10-25% high molecular weight PI. A residual stress, due mainly to thermal expansion difference, of 5000-7000 psi is present on PI film on a substrate due to various process steps (such as, for example, via hole generation). There are always stress concentrations in the PI film which raise the stress to the point where the residual stress is the same as the yield strength of the material. Also, there will be some small cracks or crazes, either sharp or rounded, produced near the vias or at the point of the defects. The problem of rapid fracture crack propagation can be alleviated by incorporating a small (10-25%) fraction of a very high molecular weight PI of the same chemistry (or of different chemistry if miscible). This is based on the fact that only very high molecular weight polymers form the backbone of fibrils at the vicinity of the crack tip. (See, for example, Hertzberg and Mansion, Fatigue of Polymers, Academic Press, N.Y., 1980.) Adding the high molecular weight PI does not reduce the planarity or gap- filling ability of polymer. The environmental stress crazing caused by certain hot chemicals will also be reduced or diminished by this new composition.

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