Effects of Aging on Macro Performance and Multiscale Structure Change of Highly Filled Elastomer Composites for Chip Cooling Investigated by Broadband Dielectric Spectroscopy

The aging of elastomer composites in advanced electronic packaging is becoming a pain point along with the increase in chip power density and miniaturization. High temperatures and extreme environments become common during the service lifetimes of packaging materials. Despite the wide use of elastomer composites, understanding the property-structure correlation evolution under a harsh environment remains limited, which restricted the development of high-reliability packaging materials. In this study, highly filled polydimethylsiloxane/aluminum elastomer composites for chip cooling are accelerated aging in various environments (wet air (atmospheric environment), dry air, N-2, and N-2 + H2O) at 125 degrees C, and their multiscale structure changes are investigated by broadband dielectric spectroscopy. We found that aging time and aging environment both influence the mechanical performance of the PDMS/Al elastomer composite, and the macroscopic properties of the composites deteriorate most obviously in the atmospheric environment. The elongation of the PDMS/Al elastomer composite is decreased by 82.7%, while the modulus of the PDMS/Al elastomer composite is increased by 523% after aging in atmospheric environment for 200 h, which contributes to the increase of total thermal resistance of the elastomer composite. The broadband dielectric spectra of the PDMS/Al ascertain that aging increases the bulklike segmental relaxation time and decreases the interfacial segmental relaxation time, ascribing to the cross-linking of polymer chain and polymer filler under high temperature and O-2, and thickening of interfacial layer. Our method can be applied to study the multiscale structure evolution of various aged elastomer composites.