![]() Modified/derivatised rosins, such as those indicated in the preceding paragraph, exhibit an equal propensity to resin acid evolution and are, therefore, treated in the same way with regard to setting exposure limits. After a recent study, the UK Health and Safety Executive (HSE) has introduced a new Maximum Exposure Limit (MEL) for the total resin acids, superseding reliance on formaldehyde as a "marker". ![]() This deleterious effect is caused by the presence of certain resin acids in rosin based flux fumes, although exposure limits have traditionally been based on the products of resin acid decomposition, mainly aldehydes measured as formaldehyde. ![]() In addition to potential shortcomings in terms of physical properties and chemistry, rosin based fluxes have long been associated with various occupational illnesses such as skin sensitization and, especially, asthma. Solder paste these modified rosins have only low acid value. Finally, esterification of the acid group, with the conjugated double bond system left intact, produces liquid rosin esters that can be used as tackifiers in, for example, Subsequent esterification, with glycerol, for example, yields a ' robust non-oxidising resin ideal as a protective coating. This increases softening point, and acid functionality. A further reaction which exploits the conjugated double bond system is Diels Adler addition of, for example, maleic anhydride. As before, resistance to oxidation is enhanced by the loss of conjugation. The dimerised rosin which results exhibits a higher softening point by virtue of increased molecular weight, and less crystallisation tendency. ![]() A further reaction that can exert an inhibiting effect upon abietic type acid oxidation is polymerisation, again, involving the conjugated double bond system. This can be minimised in many ways: hydrogenation to fully saturate the double bond system dehydrogenation, to increase unsaturation, leading to a more stable aromatic fused ring system and disproportionation, in which hydrogen is transferred to yield a single double bond in one molecule, and an aromatic system in a "partner" molecule. B23K2101/36- Electric or electronic devicesĪ propensity to oxidation, which has a darkening effect and which impairs solubility and fluxing ability, is caused by the interaction of the conjugated double bond system with atmospheric oxygen.B23K2101/00- Articles made by soldering, welding or cutting.coatings, fluxes Selection of soldering or welding materials, conjoint with selection of non-metallic compositions, both selections being of interest with organic compounds as principal constituents B23K35/3612- Selection of non-metallic compositions, e.g.coatings, fluxes Selection of soldering or welding materials, conjoint with selection of non-metallic compositions, both selections being of interest B23K35/36- Selection of non-metallic compositions, e.g.B23K35/22- Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material.B23K35/00- Rods, electrodes, materials, or media, for use in soldering, welding, or cutting.B23K- SOLDERING OR UNSOLDERING WELDING CLADDING OR PLATING BY SOLDERING OR WELDING CUTTING BY APPLYING HEAT LOCALLY, e.g.B23- MACHINE TOOLS METAL-WORKING NOT OTHERWISE PROVIDED FOR.Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.) Filing date Publication date Priority claimed from GB0006989.8 external-priority Application filed by Multicore Solders Limited filed Critical Multicore Solders Limited Priority to AU37620/01A priority Critical patent/AU3762001A/en Publication of WO2001070449A1 publication Critical patent/WO2001070449A1/en Links ![]() Inventor Steven James Cooper Frank Timothy Lawrence Original Assignee Multicore Solders Limited Priority date (The priority date is an assumption and is not a legal conclusion. ![]()
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