Solution for Short Tail Issue on Electroless Nickel Electroless Palladium Immersion Gold (ENEPIG) Bond Finger with 0.7mil Gold Wire

Gold wire bonding process was evaluated with ENEPIG bondfingers which consist of 5umNi/0.2umPd/0.2umAu layers on the Cu traces. Total of 295 wires with wire length range from 2.4 to 3.8mm were bonded for each package. Massive short tail issues were encountered at initial set-up, which resulted in the discontinuity of the wire bonding process. Damage on the bonding surface was observed after the short tail happened which triggered by missing ball alarm. Capillary design with chamfer angle (CA) of 90 Degree and bottle neck height (BNH) of 180um was used and the result shows that short tail was reduced. To achieve short tail free, different ø0.7mil wire types were evaluated. Type A wire (99% Au) is having short tail in most of the runs and low wire pull reading in some cases. Type B (99% Au) and Type C (99.9% Au) wire have good wire pull results and do not have short tail issues. In this study, the key finding is that the wire type is very important for achieving short tail free bonding and right selection of wire provides a wider bonding parameter window. The best few runs had achieved wedge pull strength of $\gt 1.5$ gf. from this stud, it is observed that capillary with larger CA and smaller BNH has less short tail issues. From the study, type B and type C do not have short tail issues. Type B wire also has better response to pre-contact and pre-base scrub. Wire type A, (99% Au) has better wire sweep resistance compare to type B and type C. In overall, wire type B has best results in term of bonding continuity and wedge pull results.