Polyimide modified with metal coupling agent for adhesion application

Polyimide hybrid metal oxide thin films used on flexible print circuit boards are prepared by the in situ sol–gel process. The precursor, poly (amic acid), containing 2,2′-bis[4-(4-aminophenoxy) phenyl]propane ( p-BAPP), 3,3′,4,4′-benzophenetetraacarboxylic anhydride (BTDA) and p-aminopropyltrimetoxysilane (APrTMOS), is synthesized, and then phenyltrimethoxysilane; PhSi(OCH 3) 3 and tris(2,4-pentanedionatio) aluminum(III); Al(C 5H 7O 2) 3 are added and mixed thoroughly. Following curing, the polyimide/PhSiOx/Al 2O 3 hybrid films exhibit high transparency and flexibility. The adhesion improvement between copper and polyimides hybrid films is investigated by peel test and the X-ray photoelectron spectroscopy (XPS) measurements are made to demonstrate that the Si elements from APrTMOS and PhSiOx migrate from the surface to the bulk of polyimide hybrids. Dynamic mechanical analysis (DMA) indicates that the glass transition temperature (Tg) increases with the Al 2O 3 content and the tanδ peak becomes broader and lower. The nano-sized Al 2O 3 particles are highly dispersed in the hybrid film, as detected by high-resolution transmission electron microscopy (HRTEM). The polyimide/PhSiOx/Al 2O 3 films show good peel strength with copper, as well as high Tg values. They may therefore have potential applications in flexible print circuits.