Silver Pick-Up during Tail Formation and Its Effect on Free Air Ball in Thermosonic Copper Ball Bonding

The tail breaking process is studied by investigating tail bond imprint micrographs. The imprints were made on Ag metallization (diepad) with Cu wire (Cu - Ag) and with Au wire (Au - Ag). In the Au - Ag case, Au wire residue was found on the diepad indicating fracture occurred in the Au wire. In the Cu - Ag case, no Cu residue was found on the imprint, but material fracture of the substrate metallization. A more detailed investigation of the Cu …