for reflow soldering , radiant heating is applied to one surface of a printed circuit board on which electronic components are placed and onto which cream solder is supplied and at the same time hot air is blown locally and roughly perpendicular to to - be - connected points on said one surface of the printed circuit board . this reflow method permits secure soldering even if the hot air is set at a temperature not exceeding the heat resistance of the electronic components , which is possilbe because of its combination with the radiant heat . moreover , this reflow method can permit soldering in such a manner that only the to - be - connected points are heated selectively , because the hot air is blown locally and roughly perpendicular to the points to be connected . thus , this reflow method prevents heat damage to other sections than the to - be - connected points and ensures that the solder at the to - be - connected points is melted .