Effect of plasma treatment on adhesion characteristics at interfaces between underfill and substrate

The effects of plasma treatment on the surfaces of the flame resistant-4 (FR-4) and copper substrates are investigated in terms of X-ray photoelectron spectroscopy (XPS), contact angle, and atomic force microscopy (AFM). The adhesion strengths of the underfills/FR-4 substrate and underfills/copper substrate are also studied. As experimental results, the plasma treatments of FR-4 and copper substrate surfaces yield several oxygen complexes in hydrophilic surfaces, which can play an important role in increasing the surface polarity, wettability, and adhesion characteristics of the underfills/substrates. And, the curing temperature ranges of the underfills, which have the maximum adhesion strength of the underfills/FR-4 substrate and underfills/copper substrate, were 140–150 °C.