Abnormal Cu3Sn Growth and Kirkendall Formation Between Sn and (111) and (220) Preferred-Orientation Cu Substrates

(111) and (220) preferred-orientation Cu substrates were successfully produced by varying electroplating current-density. While these preferred-orientation Cu substrates reacted with Sn, serious Kirkendall voids formed at the interfaces between Sn and (111) and (220) preferred-orientation Cu substrates. Also, abnormal Cu 3 Sn growth occurs; the Cu 3 Sn layer decreased upon aging and vanished after 1000-h aging. With a prolonged 2000-h aging, a Cu 3 Sn layer re-grew at the Cu 6 Sn 5 /Cu interface. The abnormal Cu 3 Sn growth was found to highly associate with serious Kirkendall formation