Buried interfacial structures containing epoxy underfills are important in the microelectronics industry and their structures determine the interfacial adhesion properties of electronic devices and ultimately their lifetime. Weak adhesion and delamination at such interfaces lead to premature failure of microelectronic devices. In this work, sum frequency generation (SFG) vibrational spectroscopy, an intrinsically surface sensitive technique, was utilized to investigate the molecular structure of buried epoxy interfaces before and after accelerated stress testing. This technique was used in order to relate the molecular-level structural changes of the epoxy systems to the macroscopic adhesion strength and determine if silane adhesion promoters can affect a polymer/epoxy system. Two controls systems were used; a hydrophilic and hydrophobic surface, interfacial water was detected after hygrothermal aging on the hydrophilic surface but was not detected on the hydrophobic surface. Lap shear analysis was performed and it was found that the hydrophilic surface had greatly reduced in adhesion strength after aging, much more reduced than the hydrophobic surface. To determine if the adhesion strength could be increased after aging, silane adhesion promoters, (3-aminopropyl)trimethoxysilane (ATMS), (3-glycidoxypropyl)trimethoxysilane (GPS), and octadecyltrimethoxysilane (OTMS), were introduced into the system. For the hydrophilic model surface, each silane prevented interfacial water from forming and increased adhesion strength after aging. For the hydrophobic model surface, ATMS and GPS increased the adhesion strength, while OTMS did not change the adhesion strength after aging. This research demonstrates that molecular structural studies of buried epoxy interfaces during hygrothermal aging using SFG vibrational spectroscopy can greatly contribute to the overall understanding of moisture-induced failure mechanisms of organic adhesives found in microelectronic packaging.

Characterization of polymer/epoxy buried interfaces with silane adhesion promoters before and after hygrothermal aging for the elucidation of molecular level details relevant to adhesion

251st National Meeting (2016)

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