Disclosed is a solder bonding structure which is capable of retaining sufficient solder bonding strength and ensuring high bonding reliability even in severe environments having an extremely large temperature difference. In the solder bonding structure, an electronic component 4 is mounted on a main surface 1a of a substrate having an electrode section 2 and an insulating film 3, and the electrode section 2 and the electronic component 4 are electrically bonded to each other through a solder section 5, and a flux residue 6 exuded from the solder section 5 is present between the electronic component 4 and the insulating film 3. The flux contains an acrylic resin, an activating agent, and a thixotropic agent having a hydroxyl group. The glass transition point of the acrylic resin is not higher than −40° C., or not lower than the softening temperature of the flux residue. The flux residue has a maximum value of 300×10−6/K or less of linear thermal expansion coefficient within a temperature range from −40° C. to the softening temperature of the flux residue.