What is the best way to solder a GSM module with castellated vias. I have designed a PCB in which i have extended the solder pads to 4mm. I will clean the solder pads with flux and i’m thinking of drag soldering the pins using flux also. I will be using lead-free solder. Is there any better way?
I have no idea what a “castellated” via is. But, the flux for lead-free solder contains organic acids that are activated by the heat of soldering. All of the flux MUST be cleaned away! Use hot water and a tooth brush, then flush with distilled water and finally used compressed air to clear all the water from under all the components. Otherwise you will discover in a few months the flux has eaten away the copper on your board.