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
Asymmetric C-element Asymmetric C-element Asymmetric C-elements are extended C-elements which allow inputs which only effect the operation of the element when transitioning in one of the directions. Asymmetric inputs are attached to either the minus (-) or plus (+) strips of the symbol. The common inputs which effect both the transitions are connected to the centre of the symbol. When transitioning from zero to one, the C-element will take into account the common and the asymmetric plus inputs. All these inputs must be high for the up transition to take place. Similarly when transitioning from one to zero the C-element will take