Effect of black copper oxide on interface adhesion between copper substrate and glob-top resin

A study is made of the effects of black copper oxide coating and other plating variables on adhesion strength of glob-top resin to copper substrates for Tape Ball Grid Array (TBGA) package applications. The button shear test was performed to measure the interfacial bonding strength. Several surface analytical techniques were employed to establish the correlations between the interface bond strength and various surface parameters, such as surface free energy, chemical element, surface roughness and fracture morphology. The experimental results showed that the presence of black oxide coating (Sample C) resulted in significantly higher interface bond strength than the bare copper (Sample A) or nickel coated (Sample B) surfaces. Further processes (Samples D and E) after the black oxide coating exhibited detrimental effects, to a varying degree, on interface bond strength. The interface bond strength was approximately proportional both to surface free energy and roughness of surface finishes, indicating that wettability and mechanical interlocking both played a significant role in forming adhesion with glob top resins