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Effect of Composition and Bead Settling on Debonding of Underfill Layers

Published online by Cambridge University Press:  21 March 2011

Lorraine C. Wang  and
Reinhold H. Dauskardt
Lorraine C. Wang
Affiliation:
Department of Materials Science and Engineering, Stanford University, Stanford, CA 94305-2205
Reinhold H. Dauskardt
Affiliation:
Department of Materials Science and Engineering, Stanford University, Stanford, CA 94305-2205
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Abstract

With the increased complexity of microelectronic devices continuing to drive chip packages to smaller sizes, the need for reliable high-density flip chip packaging is increasingly important. In these packages, epoxy underfills are used to surround a solder ball grid array in order to support thermomechanical stresses in the system. This research focuses on determining the mechanisms that cause debonding at interfaces in these packages, particularly between the underfill and chip passivation. A fracture mechanics approach is used to study the adhesion of Si3N4 to two model underfills, one based on aliphatic epoxy and the other based on bisphenol F epoxy. Interestingly, these two underfills, which are similar mechanically, appear to show very different critical and subcritical behavior. The aliphatic underfill exhibits subcritical debond growth under constant displacements, behavior typically seen in interface systems, while the bisphenol F underfill surprisingly shows little susceptibility to stress corrosion. Although both underfills show evidence of silica bead settling, the addition of filler has opposing effects on their critical adhesion values. The effects of varying filler content in these underfills as well as environmental effects on the critical and subcritical behavior of these systems will be examined.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 682: Symposium N – Microelectronics and Microsystems Packaging , 2001 , N1.7
Copyright
Copyright © Materials Research Society 2001

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References

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