PROBLEM TO BE SOLVED: To provide a method for forming a solder joint which can suppress crack progress of a solder joint even under such a severe environment that a difference in temperature is large and vibration is loaded, and can suppress crack progress in the interface vicinity between an electronic component and the solder joint even when solder joining is performed by using an electronic component not subjected to Ni/Pd/Au plating and Ni/Au plating, and to provide an electronic circuit board having the solder joint and an electronic control device.SOLUTION: There is provided a method for forming a solder joint using a solder paste composition which has a flux containing a powdery lead-free solder alloy containing 2 wt.% or more and 3.1 wt.% or less Ag, 1 wt.% or less Cu, 1 wt.% or more and 5 wt.% or less Sb, 3.1 wt.% or more and 4.5 wt.% or less Bi, 0.01 wt.% or more and 0.25 wt.% or less Ni, and with the balance being Sn, a resin, a thixotropic agent, an activator and a solvent.SELECTED DRAWING: Figure
