![]() ![]() Residue may be removed with an appropriate solvent. R residue is hard, non-corrosive, non-conductive, and may be left on. Rosin flux has very low activity and is suitable only for easy-to-solder surfaces. ![]() Rosin flux consists of rosin and solvent. Note overlap of activity levels between flux groups. Each is available with a variety of activity levels, physical qualities of their residue, and cleaning methods required.įlux Comparison chart shows relative activity ranges of each flux category. There are five main categories in QQ-S-571E. ![]() ![]() Using a smaller powder will just cost more.įlux categories are defined by Military Specification QQ-S-571E as well as the IPC flux rating system. Using too large a powder will cause printing and dispensing difficulties, compromising quality. If the feature is smaller, the application requires the next smaller powder size. Dimensions listed for gullwing, square/circle, and dispense dot sizes represent the smallest feature recommended for that size powder. The Powder Size chart (Figure 2) cross-references particle size to typical printing and dispensing requirements. Having selected the best alloy, particle size is next. If a solder joint needs to retain physical integrity during a later operation, such as a second reflow process, the peak temperature of the later operation needs to be below the solidus temperature of the alloy. While wetting begins at the solidus temperature, best wetting is achieved at a peak temperature 15º C or more above the liquidus.
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