Soldering (see RoHS), has led to a change in formulation of both solders and fluxes. Water-soluble non-rosin-based fluxes have been increasingly used since the 1980s so that soldered boards can be cleaned with water or water-based cleaners. This eliminates hazardous solvents from the production environment, and from factory effluents. Those regulations have also reduced the use of lead based solders, and caused the melting temperatures of solders in use to increase by up to . "Hot-bar reflow" is a selective soldering process where two pre-fluxed, solder coated parts are heated with heating element (called a thermode) to a sufficient temperature to
Praseodymium Praseodymium Praseodymium is a chemical element with symbol Pr and atomic number 59. It is the third member of the lanthanide series and is traditionally considered to be one of the rare-earth metals. Praseodymium is a soft, silvery, malleable and ductile metal, valued for its magnetic, electrical, chemical, and optical properties. It is too reactive to be found in native form, and pure praseodymium metal slowly develops a green oxide coating when exposed to air. Praseodymium always occurs naturally together with the other rare-earth metals. It is the fourth most common rare-earth element, making up 9.1 parts per million of