Chemically crosslinked polyimide-POSS hybrid: A dielectric material with improved dimensional stability and dielectric properties

One kind of the leading polymers applied in microelectronic packaging is polyimide (PI)-tethered polyhedral oligomeric silsesquioxane (POSS) hybrids. However, a well-known problem is that PI-POSS hybrids usually suffer from the serious thermal expansion at elevated temperature, leading to deteriorated reliability in electronic devices. In this work, a series of PI-POSS hybrids is successfully fabricated using aminopropylisobutyl-POSS as a reactive filler, and then the phenolic hydroxyl groups on side chains of hybrids react with terephthaloyl chloride at room temperature to form a crosslinked network. The well-designed crosslinked network suppresses the thermal expansion and improves the dielectric properties of hybrids together with POSS. As an example, after 24 h of crosslinking reaction, the coefficient of thermal expansion of the crosslinked hybrid with 14.6 wt% POSS (CPIH-2-24H) is 24 ppm/K, revealing a 59% reduction against the unmodified PI (82 ppm/K). Meanwhile, the dielectric constant and loss of CPIH-2-24H are decreased by -27% (2.68 vs. 3.68) and -72% (0.007 vs. 0.025), respectively, compared with the corresponding values for the unmodified PI. These data indicate that the resultant crosslinked PI-POSS hybrids may be used as microelectronic packaging materials, and the work provides a feasible approach to restrict the thermal expansion of PI-POSS hybrids by room-temperature chemical crosslinking.