Study on metal adhesion mechanisms in high density interconnectprinted circuit boards

摘要

Strong chemical reactions between metal and polymer substratessignificantly enhance adhesion of the metal to the polymer. This studyinvestigated the adhesion of three types of thin film metals, includingCu, NiCr, and Cr, to a fully epoxy-based polymer. Before depositingthese thin film metals, the epoxy surface was treated with either an Aror O plasma etch. It was found that NiCr and Cr produced higher peelstrengths than Cu, but NiCr and Cr did not produce different peelstrengths than each other. It was also found that O plasma etch producedhigher peel strengths than Ar plasma etch. An XPS (X-ray photoelectronspectroscopy) study was performed to determine the reactivities of themetal thin films with the epoxy. Both the Ni and Cr of the NiCr thinfilm reacted with the epoxy, forming metal oxide at the metal-epoxyinterface. It was determined that Cr thin film reacted more strongly,forming slighty more metal oxide at the metal-epoxy interface. Cu wasnot seen to react strongly with the epoxy. Thermodynamic informationsupported the relative amounts of oxides found by XPS. When comparingthe Ar-treated to the O-treated samples for the NiCr and Cr metal types,more oxide was seen on the O-treated samples