Inorganic acids in the form of halides (discussed below) are found in some electronics fluxes but in very low concentrations and only supplemental to the greater amounts of organic acid.Īcid strength is determined by its hydrogen ion content more hydrogen ions equate to greater acidity. Inorganic acids (compounds of hydrogen with non-metals) such as hydrochloric or hydrobromic have exceptional oxide removal properties but not compatible with electronic reliability they leave highly conductive and corrosive residues that can cause electrical failures. The term used to describe flux acidity is “activity.” Most often, the acids are organic (meaning they contain carbon). (Jim) Smith, PhD ABD, President, Electronics Manufacturing Sciences, part of the flux that removes oxides, which the industry for reasons lost in antiquity insists on calling “activators,” is almost always acid, either directly or in a compound that releases acid when heated. Removal of oxides and prevention of reoxidation is the role of flux. With the exception of gold, all component surfaces are oxidized and that oxide must be completely removed and the deoxidize surface protected from reoxidizing before application of the solder. Oxidized metal lacks that energy, however, and does not allow wetting. Elemental metal is unstable and has energy to draw the solder (interatomic attraction). Solder flow is known as wetting and occurs only if the solder is applied to a pure elemental metal surface. If you haven’t read Part 1 of soldering flux, that really is the best place to start. If you read Part 1, you know the fundamentals of flux and are ready for the specifics of how to pick the flux that will make your soldering life very easy. This is the second of a three-part explanation of fluxes: what they do, how they do it and which one is best for various applications. However, fluxes are complex and making the right choice involves navigating a chemical minefield complicated by occasionally bizarre terminology and, too often, shady marketing practices by some well-known flux manufacturers. The right flux can save immense costs including but not limited to solder defects, cleaning and product failures. Liquid flux is just those same ingredients in a solvent.įlux selection may be the most important decision any electronics assembly business will ever make. RLC Resonant Frequency and Impedance Calculatorįlux consists of two basic ingredients: acids to remove oxides and a substance or substances (“solids”) to coat the surface and prevent oxygen from reaching the surface after oxides are removed.Bandwidth Rise Time and Critical Length Calculator.Transmission Line Reflection Calculator. Trace Width and Current Capacity Calculator.
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