PURPOSE: To divide bridged solder onto adjacent conductor patterns without removing solder bridges by forming a heat resistant insulating film which repels molten solder to the iron tip part of a soldering iron.

CONSTITUTION: Ceramics 10 is stuck as the heat resistant insulating film which repels the molten solder to the iron tip part of a soldering iron. This iron tip part is applied to the solder bridge point in the middle on the adjacent conductor patterns to separate the bridged solder. The heat resistant insulating film is formed by applying, such as brushing, dipping or spraying, and by drying and/or curing by heating. This heat resistant insulating film is composed of a material essentially consisting of any of metals, metal oxides, org. and inorg. composite materials, silica, titanium oxide, silicon carbide and aluminum nitride, an org. solvent and a binder. As a result, the packaging and soldering operation of semiconductor packages, etc., to circuit boards is facilitated.