A flip-chip process is to provide a pressing jig with a channel, so that the pressing jig grips a chip module by vacuum suction through the channel, and the chip module can be bonded onto a circuit board via a plurality of solder bumps through the pressing jig, and then a heating device is provided to heat the plurality of solder bumps and reflow the plurality of solder bumps. Therefore, the chip module can be vacuum-gripped by the pressing jig to suppress deformation of the chip module, so that the solder bumps can effectively connect to corresponding contacts of the circuit board.