PCBgogo

Hello,
We have some all-SMD, FR4  PCBs which comprise LEDs and Driver components,  or some PCBs which have  just driver components. These PCBs are either double sided or 4 layer. They are 1.6mm in thickness. The components range from D2PAK FETs down to 0402 resistors, and 4mm by 4mm SMD LEDs.
We are  sometimes  finding that  these PCBs, when delivered to us, don't work because of dry-jointed LEDs or other components.
We find this out because we  can often make PCBs work by simply 'dunking' on/near the component pads with a big , wetted soldering iron.
However, we really need a better way to reflow these SMD components. Do you believe a hot-plate would be best?, or some kind of little SMD oven?, or an IR oven?
Sometimes the dry-jointed components have connection to a thermal copper pour  on the PCB bottom. -But sometimes this is not the case.
We are actually wondering if the best & quickest way of doing it could be to simply put the PCB on a cheap hot-plate and waft over the suspect dry-joint components with a  "gas gun" soldering tool?..(blowing scorching hot air on the suspect components)