am300854g_si_001.pdf (39 kB)
Molecular Level Understanding of Adhesion Mechanisms at the Epoxy/Polymer Interfaces
journal contribution
posted on 2012-07-25, 00:00 authored by Chi Zhang, Jeanne Hankett, Zhan ChenIt is important to understand the buried interfacial
structures
containing epoxy underfills as such structures determine the interfacial
adhesion properties. Weak adhesion or delamination at such interfaces
leads to failure of microelectronic devices. Sum frequency generation
(SFG) vibrational spectroscopy was used to examine buried interfaces
at polymer/model epoxy and polymer/commercial epoxy resins (used as
underfills in flip chip devices) at the molecular level. We investigated
a model epoxy: bisphenol A digylcidyl ether (BADGE) at the interfaces
of poly (ethylene terephthalate) (PET) before and after curing. Furthermore,
small amounts of different silanes including (3-glycidoxypropyl) trimethoxysilane
(γ-GPS), (3-Aminopropyl)trimethoxysilane (ATMS), Octadecyltrimethoxysilane
(OTMS(18C)), and Octyltrimethoxysilane (OTMS(8C)) were mixed with
BADGE. Silane influences on the polymer/epoxy interfacial structures
were studied. SFG was also used to study molecular interfacial structures
between polymers and two commercial epoxy resins. The interfacial
structures probed by SFG were correlated to the adhesion strengths
measured for corresponding interfaces. The results indicated that
a small amount of silane molecules added to epoxy could substantially
change the polymer/epoxy interfacial structure, greatly affecting
the adhesion strength at the interface. It was found that ordered
methyl groups at the interface lead to weak adhesion, and disordered
interfaces lead to strong adhesion.