| dc.description.abstract | Typically, a so-called surface rolling layer (SRL) would form on the Cu foil after mechanical process. This thin surface rolling layer has very different properties from the bulk Cu foil. We find that the thinner surface rolling layer by using the large cold-roll percentage, which affects the solder wettability on the rolled Cu. With wetting test results and BSE images, we can correlate the results of the reactivity with the solder wettability. And, we confirm that the reactivity is the driving force for wetting in high-Pb/Cu wetting solder system. The fast interfacial reaction depletes the Sn content in the wetting tip of the molten solder. As the Sn content in the wetting tip is insufficient, it is harmful for the wettability. From the XRD results and texture coefficient (TC), the preferred-orientation of the Cu raw material will transfer from (200) preferred-orientation to (220) preferred-orientation after rolling process. It is because of the compressive and the shear stress effects. Then, the Cu substrate reinstates to the random structure after annealing. Finally, the random structure will transform to the (200) preferred-orientation, as the Cu substrate is applied with a prolonged annealing. And we find that the (200) preferred-orientation has the highest surface reactivity. The higher TC of (200) will lead to the higher reactivity of the bulk Cu substrate. Finally, we conclude that: the softer Cu raw material, the higher MRP, and the higher rolling-times will lead to the better wettability.
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