Ag alloy wire characteristic and benefits

Gold wire has been high volume production in IC packaging industry. With soaring price of gold in recent years and IC packaging search for cost reduction, copper wire offers 2nd alternative for wire bonding type assembly. But copper wire has drawbacks in control issues such as pad crack, aluminum splash, cratering and low throughput, Cu wire need a more complex multi-processing program to solve above problems, even if copper raw material cost is low, that cause the process costs are increased These limitations of copper wire are related to pad thickness and structure. Silver alloy wire can emerge as 3rd alternative as the cost can compete with copper and the properties of silver are nearly identical to gold while in the die to die package which benefits will be more apparent Many Study had performed for Silver alloy wire (88% & 95%), included the general workability, wire pull, ball shear, Al splash, pad-to-pad bonding. To get good workability result, Silver alloy wire properties have been studied and done the DOE to determine the best material properties windows. The key properties included the element composition and elongation, hardness, etc. IMC is another key point for the reliability performance, with the DOE of best wire bonding parameters, the IMC structure was analyzed with different condition of lead-frame based, substrate based. Combined with process flow and compound material types, IMC behavior has been observed. Electron Migration study had been performed as well to check if any side effect for Silver alloy wire bonding. Experiment results showed Silver Alloy wire bonding has better performance than copper. Silver alloy wire can be the mainstream to replace gold and copper wire, especially in pad-to-pad wire bonding type.