| abstract |
After reflow soldering an electronic component to a circuit pattern on the front and back of a printed circuit board provided with a through hole, and further soldering a lead of the electronic component to the through hole, the more the subsequent soldering, the more the molten solder is soldered. Provided are a flux and a solder paste which can improve wettability of lands and through holes. A flux using pyrazole as an activator in combination with rosin, a solder paste using the flux, and a circuit board before or after mounting electronic components having these residue films. [Selection diagram] Fig. 1 |