PURPOSE: To enable parts which are mounted on a printed wiring board and soldered to be lessened in thermal stress and enhanced in reliability by a method wherein low-melting cream solder is printed on pads provided onto the printed wiring board, and the printed wiring board is soldered to a BGA printed wiring board by fusing the low-melting cream solder.

CONSTITUTION: A solder resist 3 is printed on a BGA printed wiring board 1 partially overlapping pads 2 located on the board 1, then flux 4 is applied onto the pads 2, and eutectic solder balls 5 are mounted on the pads 2. The solder balls 5 are fused by heating in a reflow oven or the like so as to form bumps 6. Low-melting cream solder 9 is printed on pads 8 located on a mating printed wiring board 7. Then, the BGA printed wiring board 1 is turned upside down, and the bumps 6 are aligned with the low-melting cream solders 9. Lastly, the printed boards 1 and 7 are heated in a reflow oven or the like to fuse the low-melting cream solders 9, whereby the wiring boards 1 and 7 are soldered to each other.