Photodefinable wafer level underfill has been developed and its design concept has been verified, that is, the removal of underfill on the top of bumps enables the excellent quality of bump connection without underfill entrapment. The photodefinable composition using carboxylic type polyimide shows poor resolution, whereas the phenol type polyimide based Photo WLUF, CD3000B, has good patterning properties. CD3000B could form underfill patterns having 15 μm diameter holes on 25 μm Cu bumps through conventional photolithography processes. The bonded samples showed the seamless bump junction and passed moisture sensitivity level 2 and thermal cycling reliability test.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.