Metal Finishing Guide Book


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surface morphology. In most instances, the recommended working temperature for the sulfuric acid plating solution does not exceed about 27°C, and more typically, plating is carried out at room temperature. Because these copper plating electrolytes are designed Figure 1: Thickness of copper plated on the surface and in the through- for use at room temhole. perature, they are not generally suited for plating throughholes at elevated temperatures. On many occasions, the brighteners undergo chemical changes at elevated temperatures and are no longer effective for copper plating. In other instances, the levelers used in combinaFigure 2: HT 100 microdistribution on 1.6 mm measured at 24°C.. tion with the wetter/ suppressor additives in the solution present issues leading to the deposition of dull, rough layers, especially inside the through-holes. The thermal characteristics of the copper layer deposited at elevated temperatures are adversely affected and reliFigure 3: HT 100 microdistribution on 1.6 mm measured at 35°C. ability performance decreases. Failure occurs during the soldering operation that follows plating.Over the past few years, printed circuit board fabrication has dramatically increased in geographic areas with hot climates. In order to maintain the desired temperature in these areas, chillers or other cooling methods are generally needed. Thus, it is desirable to simplify the process in these warmer areas to eliminate the need for chillers 246

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