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Mechanism of Moisture Diffusion, Hygroscopic Swelling, and Adhesion Degradation in Epoxy Molding Compounds

  • M. H. Shirangi
  • B. Michel
Chapter
Part of the Micro- and Opto-Electronic Materials, Structures, and Systems book series (MOEM)

Abstract

Epoxy molding compounds (EMCs) are widely used as encapsulation materials for protecting the semiconductor chips of plastic encapsulated microcircuits (PEMs) against harsh environments and mechanical forces such as impact and pressure. Since PEMs are usually exposed to humid conditions during their storage and service life, they absorb moisture, which causes many reliability problems such as popcorn cracking and interfacial delamination during the solder reflow process. This chapter presents a comprehensive investigation of the mechanism of moisture diffusion in EMCs. The results from moisture diffusion tests during absorption, desorption, and re-sorption of various EMC samples are presented. The gravimetric results showed a non-Fickian behavior of the moisture diffusion in the EMCs. This non-Fickian behavior was found to induce a non-reversible effect by causing some residual moisture content upon baking these plastic parts. The gravimetric moisture diffusion results can be correlated to moisture-induced hygroscopic swelling and adhesion loss. Hygroscopic swelling of EMC and its reversibility was investigated using both bulk EMC samples and bi-material beams. Moreover, the effect of moisture on the adhesion of EMC/Cu interface was studied using a fracture mechanics approach. Two mechanisms of adhesion loss upon moisture diffusion can be observed. Some of the adhesion loss due to small amount of moisture content may be recovered via a proper annealing. However, upon long-term storage in humid conditions, where the second phase of non-Fickian behavior is activated at the interface, none of the adhesion loss can be recovered after baking the samples.

Keywords

Epoxy molding compound (EMC) Plastic encapsulated microcircuit (PEM) Moisture Diffusion Moisture sensitivity level Fickian non-Fickian Absorption Desorption Residual moisture content Re-sorption Electronic packaging Hygroscopic swelling Bi-material beam Warpage Adhesion Fracture toughness Adhesion loss Adhesion recovery Degradation Hydrogen bonding 

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Copyright information

© Springer Science+Business Media, LLC 2010

Authors and Affiliations

  1. 1.Department of Micro Materials Center Berlin (MMCB)Fraunhofer Institute for Reliability and Microintegration (IZM)BerlinGermany
  2. 2.Robert Bosch GmbHAutomotive Electronics, Development ASIC & Power PackagesReutlingenGermany

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