For common electronic component soldering I just use 15 watts anda pointed tip for controlled application of heat to the small solder joint. For larger diameter power wires I set the iron to 30 watts and use a chisle tip to ensure rapid transfer of heat to the larger area. Be very careful not to apply too much heat, or for too long, to semiconductors or motor windings because they can be easily damaged by prolonged high tempuratures. A goodsolder joint is made by applying a sufficient amount of heat for the minimum amount of time to ensure both mechanical and electrical bonding between the component and contact pad. If the solder flows well and remains shiny after cooling the joint is probably good. If the solder clumps or is dull after cooling the joint is probably bad and the component may be damaged.