FLUX FOR LEAD-FREE SOLDER AND METHOD OF SOLDERING

摘要

A flux for soldering which can prevent the development of whiskers which is apt to occur when electronic parts are soldered to a printed wiring board with a lead-free solder (e.g., Sn-3.0Ag-0.5Cu) having a higher tin content and a higher melting point than eutectic solders. The flux is suitable for use as a non-cleaning type post flux in flow soldering. The flux contains at least one compound selected among acid phosphoric acid esters and derivatives thereof in an amount of 0.2-4 mass%, besides a rosin as a main-ingredient resin and an activator. By conducting soldering in a nitrogenous atmosphere, whisker development is more effectively prevented.