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|High Current Testing of Gold and Copper Wirebonds|
|Keywords: High current testing, Gold and copper wirebonds, Design rules & reliability|
|This paper discusses the key parameters affecting the mean time to failure (MTTF) of both gold and copper wirebonds during high current testing. Currents as high as 2.5A were used in wire of diameters varying between 1 to 1.5 mil. The resistance increase was recorded as a function of temperature and wirebond current density. It was found that temperature is the most important factor in wire resistance degradation, and should replace wire length as a criterion for maximum allowable wire current. The MTTF can be associated with the maximum allowed current density for a given temperature. When dealing with multiple wires, the maximum allowed current density follows a 1/d**2 relationship. As a result, as products migrate to smaller wire diameters and higher device operating temperatures, the decades-old mil spec for maximum allowed current will give increasingly less margin for device reliability. Failure modes observed for gold and copper wires are widely different and will be discussed.|
|Luu Nguyen, Senior Engineering Manager
National Semiconductor Corporation
Santa Clara, CA