How to Solder QFN MLF Package by Hand (Using a Hot Air Rework Station) | Digi-Key Electronics

Soldering some surface mount components, such as QFN and MLF, can be very difficult by hand. These parts do not have leads that extend beyond the component body, which can be nearly impossible to reach with a soldering iron. In this video, we will demonstrate one way to solder a QFN component by hand using a hot air rework station.

A written guide showing these steps can be found here: https://www.digikey.com/en/maker/proj...

I recommend using no-clean flux and no-clean flux core solder if you do not have access to cleaning equipment that can get under the component. Pre-tin the pads on the PCB using a soldering iron. Try to get the layer of solder to be as even as possible among all pads.

Liberally apply flux to all of the pads and place the part on the footprint, doing your best to carefully line up the part pads with the footprint pads. You might need a microscope or loupe to visually inspect the alignment. You can tape a thermocouple probe near the part to get an idea of ambient temperature.

I set my hot air station to 300°C and 50-60% air flow. You might need to experiment with these numbers to get a good solder reflow without blowing your part off the board.

Start with your hot air nozzle a few inches above the component and draw circles over the PCB to “soak” the board. You want the PCB to reach a temperature of about 150°C over the course of 1-2 minutes.

Slowly lower the nozzle to about ¼-½ inches above the component, and continue to draw circles so that hot air is equally applied to all pads. The solder should reflow in 15-30 seconds, and you should be able to lightly tap the part using some tweezers. The surface tension of the solder should keep the part in place (for the most part).

Once you are satisfied with the part alignment and believe that all of the pads have made a good solder connection, slowly lift the hot air nozzle away from the part while continuing to draw circles. You want the part to cool to 150°C over 15-30 seconds. From there, you can let the board air cool.

Solder the rest of the components and test your board!

You can find the KiCad PCB design files for my custom QFN board here: https://github.com/ShawnHymel/ldo-pow...

This is the QFN part I used in the video: https://www.digikey.com/en/products/d...

Product Links:
Hot‐Air Rework Station 303D - https://www.digikey.com/en/products/d...
FX-888D Digital Soldering Station - https://www.digikey.com/en/products/d...

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