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50 The PCB Magazine • February 2015 Demarcation lines are cosmetically alarming and create concerns for the end-user. This is not an acceptable situation. The impact of demar- cation lines, in terms of quality, can be dem- onstrated using a drop test. The drop test is a simulation of a handheld device being dropped. According to the drop test, the performance of the EPAG system is superior to that of the thin Ni ENEPIG process. In addition to the poor drop test performance, the thin Ni layer becomes su- perfluous as a protection layer due to the low thickness and resultant poor morphology. Silver Wire Bonding Wire bonding is a field that is evolving like any other. Bonding speed, wire hardness and cost are all in the mix. Some 3D packaging philosophies mean that wire bonding is here to stay unless it is replaced completely by flip- chip derived bonding technology. Reduction in cost without yield and capacity loss is a major driver in this field. Pure copper wire bonding is one candidate for cost reduction, but this can result in other complications like component and equipment damage due to the forces and energy required. Gold, on the other hand, is the preferred and established medium, but recent exploration into silver wire bonding is proving potentially viable. The high potential for silver as a technical replacement for gold is the com- parable softness of the metals. Figure 1 demon- strates that ENEPIG and EPAG are both able to deliver confidence in silver wire bondability. Additional to the technical similarities, silver also complies, in some way, to cost saving. EPAG exhibits a wide working window with good performance indicators for silver wire bonding. Well known OEMs are also champion- Figure 6: the impact of low ni on demarcation lines. Figure 7: the performance comparison of the low ni EnEPIG compared to the EPAG process. THE FUTURE OF NICKEL IN NICKEL/PALLADIUM/GOLD FINAL FINISHES continues feature