Patent ID: 7131566

Claim:
A flow-soldering system for performing a mixed packaging operation using lead free solder comprising: a fourth conveyor route providing: a carry-in unit which carries in a circuit board having an upper surface and a lower surface, one of the upper and lower surfaces of which has a surface mount device having been reflow-soldered thereonto using lead-free solder paste, the circuit board having a lead or a terminal of an insertion mount device inserted from the upper surface into a through hole drilled in the circuit board; a flux applying unit which applies flux to the circuit board carried in by the carry-in unit; a preheating unit which preheats the lower surface of the circuit board in order to shorten a time required for connecting the lead or the terminal of the insertion mount device to the circuit board by a flow soldering unit after the flux is applied to the circuit board at the flux applying unit; a flow-soldering unit which flow-solders the lead or the terminal of the insertion mount device to the circuit board by applying lead-free solder jet to the lower surface of the circuit board, which has been preheated by the preheating unit, the lead-free solder jet being applied while cooling the upper surface of said circuit board by a board cooling system which blows nitrogen in a temperature range of 20° C. to about 50° C. upon the upper surface in order to prevent a peel off effect that would result from a re-melting of a portion of the solder paste connecting the surface mount device, a temperature of the lead-free solder jet applied to the lower surface of the circuit board being within a range of 170° C. to 260° C.; and an adjust unit to adjust temperatures of both surfaces of the circuit board which cools the upper surface and the lower surface of the circuit board, immediately after the soldering at the flow-soldering unit; and a back conveyor route along, which the flow soldered circuit board is returned from the adjust unit to a position near the carry-in unit on the forth conveyor route.