An autocatalytic electroless gold process suitable for electronicpackaging applications, particularly wirebonding needs, is described.This process yields high purity, non porous soft gold of any thicknessthat meets or exceeds all military specifications. The process can beused for a wide variety of organic laminates (FR4, multifunctionalepoxies), circuitized either subtractively or additively, in addition toceramic substrates. A description of the process flow, bath parameters,bath performance and resulting metallurgy are described. The processacts as an excellent follow on to the conventional electrolessnickel/immersion gold surface finishing systems currently practiced bythe industry. Rate, purity, hardness, and wirebond data as a function ofbath life (metal turnovers) are discussed. The plating rate can be tunedbetween 1.5 and 2.5 microns/hr. The resulting deposit remains pure(>99.93%) and soft (<70 knoop) even in the presence of metallicimpurities and upon bath aging. Wirebond and solder data as a functionof gold thickness and plating parameters are also presented. These twoassembly methods typically have competing requirements and the workingrange for both using this process are described. The process also hasthe ability to uniformly plate fine lines (>50 microns) separated bysmall spaces (>45 microns) without loss of line definition orbridging. The bath exhibits excellent throwing power. Drilled PTHs withaspect ratios as high as 15:1 (hole diameter of 0.03 mm, length of 0.45mm) can be uniformly plated
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