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
Distributed element circuit led to wider applications. Distributed element circuits are those circuits designed using the distributed element model. This model is an alternative to the lumped element model in which the passive electrical elements of electrical resistance, capacitance and inductance are assumed to be "lumped" at one point in space in, respectively, a resistor, capacitor or inductor lumped component. The distributed element model is used when this assumption no longer holds and those quantities are considered to be distributed in space. The assumption breaks down when there is a significant time taken for electromagnetic waves to travel from one terminal of the