Transition Metal β-Diketonate Adhesion Promoters in Epoxy-Anhydride Resin

Area of Science:

• Materials Science
• Polymer Chemistry
• Surface Science

Background:

• Reliable epoxy-copper adhesion is crucial for electronic packaging.
• Adhesion promoters integrated into epoxy formulations offer processing and cost advantages over substrate pre-treatment.

Purpose of the Study:

• To investigate the efficacy of first-row transition metal β-diketonates as adhesion promoters in epoxy/anhydride resins for copper bonding.
• To elucidate the mechanisms underlying adhesion improvement and enhanced moisture resistance.

Main Methods:

• Addition of cobalt(II) and nickel(II) hexafluoroacetylacetonate to epoxy/anhydride resins.
• Lap shear strength testing before and after moisture aging.
• X-ray photoelectron spectroscopy (XPS) for surface analysis and depth profiling.
• In situ Fourier-transform infrared spectroscopy (FTIR) for monitoring cure kinetics.

Main Results:

• Over 30% lap shear strength enhancement before moisture aging and 50% after aging were achieved with Co(II) and Ni(II) hexafluoroacetylacetonate.
• XPS analysis revealed increased oxygen-containing functional groups, particularly esters, on failed surfaces, correlating with improved adhesion.
• Metal chelates influenced cure kinetics by interacting with phosphine catalysts, promoting interfacial esterification.
• XPS binding energy shifts and dielectric property changes indicated metal-polymer coordination contributing to adhesion and moisture resistance.

Conclusions:

• First-row transition metal β-diketonates are effective adhesion promoters for epoxy-copper joints.
• The mechanism involves controlled cure kinetics, interfacial esterification, and metal-polymer coordination.
• These findings suggest a promising strategy for developing robust epoxy-copper interfaces through functional additives.