... plenty of ground wire and power-up copper emanates heat to PCB other position.Directly welding 775 pedestal(No removing,directly reweld ... it’s boring, adjust the tuyere bottom repeatedly, insure to make the PCB part of 775 pedestal smooth.2.Choose welding paste ... other words, at the same 250°C,when starting to heat PCB chip,the actual temperature bottom is different, for a while ...