NDLI: Residual Strain Measurement of Thin-Layer Cured Adhesives and Their Effects on Warpage in Electronic Packaging

Content Provider	IEEE Xplore Digital Library
Author	Ming-Yi Tsai Chih-Yao Chiang Chen-Yu Huang Sheng-Shu Yang
Copyright Year	1999
Abstract	Residual strains (stresses) of thin-layer adhesives are important and need be determined and further analyzed for better reliability design of the joints or bump joints in electronic or optoelectronic packaging. The purposes of this paper are to quantify residual strains of two adhesives: A (paste type) and B (film type) due to chemical shrinkage, stress relaxation, and thermal-loadings and moisture-loadings, and to investigate their effects on the warpage of die attachment assembly. At the beginning, the mechanical properties of the two adhesives in terms of temperatures are measured by dynamic mechanical analyzer (DMA) and thermomechanical analyzer (TMA). The residual strains are documented by testing fully cured adhesive/silicon bi-material plates under thermal and moisture loading using Twyman-Green (T/G) interferometry system associated with Timoshenko's bi-material theory and finite element method (FEM). Furthermore, the warpage of silicon/adhesive/Cu tri-material plates (similar to die attachment assembly) with both adhesives under thermal and moisture loading are also investigated by T/G experiments and confirmed by Suhir's solution and FEM results. For adhesive-A, the results of the bi-material plate suggest that the residual strains are only induced by mismatch of the coefficients of thermal expansion during thermal loading, rather than other factors, right after the fully cured adhesive cooling down to room temperature. On the other hand, for adhesive-B, it was found that the additional residual strain of this film adhesive caused by chemical shrinkage plus stress relaxation, is about 2.26 ? 10^-3, which accounts for 85% of thermal-residual strains in the bi-material plate from curing temperature cooling down to room temperature. Experimental results also indicated that moisture-absorption expansion of the both adhesives is the major cause of decreasing warpage for the bi-material plates at 29?C/55% RH, other than stress relaxation. In contrast to the results of the bi-material plate, the warpages of the tri-material plates are found to be insensitive to the moisture-absorption, chemical, and thermal strains of adhesives, but not to elastic moduli of adhesives, due to their relatively thin-layer and compliant nature. This paper has successfully laid down an approach for determining residual strain of thin-layer adhesive and provided information about their effect on warpage of die attachment assembly.
Sponsorship	IEEE Components, Packaging, and Manufacturing Technology Society
Starting Page	71
Ending Page	78
Page Count	8
File Size	905168
File Format	PDF
ISSN	15213331
Volume Number	33
Issue Number	1
Language	English
Publisher	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Publisher Date	2010-03-01
Publisher Place	U.S.A.
Access Restriction	Subscribed
Rights Holder	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subject Keyword	Strain measurement Electronics packaging Capacitive sensors Thermal stresses Thermal loading Residual stresses Chemicals Assembly Temperature Electronic packaging thermal management warpage Adhesive chemical shrinkage die attach residual strain thin film
Content Type	Text
Resource Type	Article
Subject	Electronic, Optical and Magnetic Materials Electrical and Electronic Engineering

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