Electronic　components　in　modern　flexible　electronics　are　connected　by　interconnects,　having　typically　the　form　of　metal　films　on　polymer　substrates.　Firstly,　this　paper　studies　experimentally　the　ductility　of　a　polyimide-supported　Cu　film　with　rough　interface(due　to　sandblasting　treatment)　and　show　that,　upon　tensile　loading　along　the　direction　of　film　surface,　the　density　of　surface　cracks　can　be　reduced　by　increasing　the　substrate　surface　roughness.　The　distribution　of　tensile　stresses　in　the　film　and　their　effects　on　film　cracking(initiation　and　propagation)　are　subsequently　studied　using　the　method　of　finite　elements.　It　is　found　that　a　rough(curved)　interface　can　reduce　the　tensile　stresses　along　the　film　surface　so　as　to　restrain　the　cracking　of　the　film.　Finally,　we　employ　the　cohesive　zone　model　to　study　the　initiation　and　spreading　of　damage　in　the　film　and　interfacial　cracking　of　the　curved　interface.　It　is　demonstrated　that　both　the　damage　and　length　of　interfacial　crack　are　reduced　due　to　interface　roughening.