Abstract: A circumferential portion of a land portion 14 which is formed on a surface of the printed wiring board for mounting a component with a lead-free solder is covered with an extending portion 21 of a solder mask 20 formed on the surface of the printed wiring board.

Abstract: An automatic soldering apparatus comprises a solder bath, and a plurality of component parts such as a jet flow nozzle, bolts, nuts and washers equipped in the solder bath, wherein a relative density of such component parts equipped in the solder bath of the automatic soldering apparatus is smaller than that of lead-free solder to be used in the automatic soldering apparatus. Preferably each piece of the component parts are made of titanium material or ceramic material having relative density of around 4.5. Further the lead-free solder includes 2.5 weight % of silver, 0.5 weight % of cupper, 1.0 weight % of bismuth, and tin for the rest, and having a relative density of around 7.5. Accordingly, in case of dropping the piece of components parts into the melting solder, the dropped piece can float on the melting solder without breaking the apparatus.

Abstract: An automatic soldering apparatus comprises a solder bath, and a plurality of component parts such as a jet flow nozzle, bolts, nuts and washers equipped in the solder bath, wherein a relative density of such component parts equipped in the solder bath of the automatic soldering apparatus is smaller than that of lead-free solder to be used in the automatic soldering apparatus. Preferably each piece of the component parts are made of titanium material or ceramic material having relative density of around 4.5. Further the lead-free solder includes 2.5 weight % of silver, 0.5 weight % of cupper, 1.0 weight % of bismuth, and tin for the rest, and having a relative density of around 7.5. Accordingly, in case of dropping the piece of components parts into the melting solder, the dropped piece can float on the melting solder without breaking the apparatus.