Plasma cleaning method for improved ink brand permanency on ic packages

Abstract

A gas phase plasma cleaning method is utilized for removing contaminants from the surface of exposed metallic, ceramic and plastic parts on integrated circuits (IC's). A two step method uses a defined gas mixture of argon and oxygen, followed by ammonia and hydrogen. For plastic packages, a two step method using a fluorinated plasma, followed by oxygen and argon is utilized. The gases are separately introduced into a plasma chamber. The argon oxygen mixture is used to remove carbonatious material by chemical reaction and by milling. The ammonia hydrogen mixture is introduced to chemically remove and reduce oxides and phosphates from the metallic parts. The fluorinate is used to remove surface silicon and organo-silicon compounds from the plastic parts, while the oxygen argon mixture removes carbonatious and ionic compounds from the plastic package surface. Surface energies are increased to permit improved adhesion of inks. Additionally, intermediate oxides on the metallic parts formed after the plasma exposure prevent complete regrowth of the normally passivating oxide layer.