Regular and proper tinning of the top and side of the solder nozzle barrel ensures the solder will flow evenly and consistently out of the nozzle. 75 is a conditioning flux specifically formulated for tinning the soldering nozzle on selective soldering machines. (Note: The clogging of flux spray nozzles with rosin residue can often by cleared up by flushing the flux spray apparatus with Isopropyl Alcohol 99%.) This rosin flux conforms to Mil-F-14256, Type RMA, and ROM1 per J-STD-004 SSF-RMA20 has the controlled activity of an RMA flux, but contains the ideal amount of solvents to reduce the clogging of the flux sprayer nozzle typical with rosin-based fluxes. Superior SSF-RMA20 is a Type RMA rosin flux formulated for selective soldering applications. SSF-WS80 is classified as an ORM0 per J-STD-004. SSF-WS80 provides the activity of a water-soluble flux, but as it is neutral, it should not corrode the stainless steel components of the equipment. Superior SSF-WS80 water-soluble flux is a neutral, alcohol-based flux ideally formulated for selective soldering applications. SSF-NC400 is classified as an ROL1 per J-STD-004. This No-Clean flux’s activity level is robust to meet the rapid activity, leaving a bright solder finish and no visible residue. Superior SSF-NC400 is an alcohol-based, No-Clean flux that contains a specialized rosin/resin blend that leaves a clear residue and is effective for both lead-free and lead-bearing solder alloys. SSF-NC50 is classified as an ORL0 per J-STD-004. SSF-NC50 leaves a clear residue and is effective for both lead-free and lead-bearing solder alloys. SSF-NC50 is also formulated to withstand the higher temperature requirements of selective soldering applications. To get away from cleaning, many companies have shifted to no-clean flux, which will be the focus of my next column.Superior SSF-NC50 is a VOC-free, No-Clean flux that promotes the rapid activity necessary for selective soldering. The fluxes described here require cleaning. However, without cleaning, assembly reliability may be compromised because the sticky rosin can attract dust and harmful contaminants in the field during service. R and RMA fluxes are not even cleaned in some applications even though they are not classified as no-clean. R and RMA types are generally noncorrosive, hence safe. The various categories of rosin fluxes differ in the concentration of the activators (halide, organic acids, amino acids, etc.). Where RCO2H is rosin in the flux (C19H29COOH mentioned earlier)Īs mentioned earlier, rosin fluxes are also referred to as rosin (R), rosin mildly activated (RMA) and rosin activated (RA). The general formula for oxide removal by rosin is: In general, rosin fluxes are weak, and to improve their activity (fluxing action), the use of halide activators is required. This means that synthetic fluxes can be used at higher temperatures than rosin fluxes, because the former decompose at higher temperatures. A flux is not effective if it decomposes at soldering temperatures, however. A desirable flux should melt and become active slightly below the soldering temperature. The melting point of rosin is 172☌ to 175☌ (342☏to 347☏), or just below the melting point of solder (183☌). This is the reason for using solvents, semiaqueous solvents or water with saponifiers to remove them. They are soluble in a variety of solvents but not water. They are naturally acidic (165 to 170 mg KOH per g equivalent). Rosin fluxes are inactive at room temperatures but become active when heated to soldering temperatures. Rosin flux is composed primarily of natural resin extracted from the oleoresin of pine trees and refined. Rosins contain several percent of unsaponifiable hydrocarbons for rosin flux removal, saponifiers (a form of alkaline chemical to make the water soapy) must be added. It consists mainly of abietic acid (70 to 85 percent, depending on the source) with 10 to 15 percent pimaric acids. The composition of rosin varies from batch to batch, but a general formula is C19H29COOH. Rosin or colophony is a natural product that is extracted from the stumps or bark of pine trees. The proper flux allows for proper solder flow and increased wetting of desired areas. Rosin Paste Fluxes are intended to be used to reduce solder balling, and bridging.
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