A Study on the Oxygen Plasma Treatment on the Peel Adhesion Strength and Solder Wettability of SnBi58 Based Anisotropic Conductive Films

O_2 plasma treatment is a useful way to increase adhesion strength between polymer resins and adhered substrates in electronic packaging areas. However, a low adhesion strength of polymer adhesives on the adhered surfaces is a critical issue for anisotropic conductive film (ACF) joint reliability, especially when it comes to moisture-induced effects. This paper discusses the effects of oxygen plasma treatment (100W 20mTorr 3min) on the wettability and reliability of solder ACFs joints on Au/Ni metal electrodes. We carried out the surface analysis using surface energy, AFM, XPS, FTIR and joint resistances, peel adhesion strength, and reliability. By using the contact angle and surface energy, the un-wetted solder joining was explained from a spontaneous wettability to a hindered wettability, as a reason for poor electrical performance and reliability after oxygen treatment. Although the resin and electrode adhesion was increased, it was proven that the solder part played a more important role in determining joint reliability and mechanical property.