PURPOSE: To prevent the oxidation of copper circuits by a heat treatment and to obtain an excellent solder rising property by incorporating specific components into a solder flux precursor.
CONSTITUTION: The formation of the solder flux precursor on a printed wiring board is executed by applying the soln. prepd. by adding the resulted product of reaction of imidazole and benzotriazole and if necessary a surfactant and a solvent, such as aceton, to a plasticizer, such as rosin, on the printed wiring board right after the production thereof and drying the coating. The resulted product of the reaction of the imidazole and benzotriazole has the high effect as the rust inhibitor of the surface of the copper circuit and the rust inhibitive power thereof is stabler than the rust inhibitive power of the imidazole used heretofore; therefore, the solder flux precursor having the excellent moisture resistance and heat resistance is obtd.
SAIKAWA TETSURO
UENOUCHI SHIGERU
