本研究利用X 光波長散佈分析儀(WDS)對鍍鈀銅線結球及接合球的橫截面進行鈀的元素分佈分析探討；研究結果顯示，鍍鈀銅線經過EFO 製程後形成結球，而原本鍍在銅線表面的鈀會溶進結球內部，在結球的球肩附近聚集，隨後結球被施以超音波接合，過程中鈀在接合球內部流動，待接合球完全凝固後，鈀則在接合球的兩半球上呈現漩渦狀的分佈。
本研究藉由觀察鈀從結球內部到接合球內部的分佈變化，推論液體銅在接合球內部的流向為漩渦狀。因為鈀在接合球內部不均勻的分佈，導致接合球內部的機械性質有所差異，在經由奈米壓痕量測的結果顯示出在富鈀區的硬度比純銅區大。

We investigated the distribution of Pd within the free-air balls (FAB) and wire bonds of the Pd-plated Cu wires by wavelength-dispersive x-ray spectroscopy mapping. After the formation of the Cu-Pd FAB, Pd was asymmetrically distributed within the FAB. The motion of the asymmetrical Pd then followed the semi-solid Cu flow during ultrasonic bonding and the Pd distribution within the ball bond formed two whirlpools of different Pd concentrations. Based on the Pd pattern obtained, the behavior of Cu flow has been further investigated and we propose whirlpool flow patterns in the interior of the ball bond. Additionally, hardness measurements by nanoindentation testing show that the Cu ball bond is harder in the regions where Pd exists.

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