In order to obtain ideal low Dk/Df film for 5G application, we have developed novel isotropic low Dk/Df film. Our newly modified PPE was soluble to organic solvents and crosslinked after curing. By formulating this new polymer and other components such as sillica filler, we have developed novel isotropic thermosetting film with low Dk/Df, high Tg, low CTE, low water absorption, high peel strength and HAST, which was supposed to be suitable film as substrate and interlayer insulating film for 5G packaging application.