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Quick QFN40 Soldering Tutorial

Dear Reader,

As a small hardware company, we’ve benefited immensely from the myriad of tutorials others have made freely available online.  In the spirit of giving back, here’s a really quick demo of how to place a 0.5mm pitch QFN40.  Because of its very fine pitch and lack of leads, this can be an intimidating package to solder.  With practice it becomes much easier.

Things I failed to mention in the video:

  • My iron is a Weller WES51 with a long conical tip
    • In this demo it was set to 700F
  • My flux is MG Chemicals 8341
  • My solder is a Kester Rosin Core 63/37 Leaded solder
  • You can do this without a microscope, but for the sake of your back and your eyes I recommend a microscope with 5x-10x magnification for this sort of fine-pitch work.

Questions?  Comments?  Let us know!

5 Responses to “Quick QFN40 Soldering Tutorial”

  1. KarolNi May 2, 2014 at 4:46 pm #

    I’m glad that you know what’s right, bad that we are doomed for leadfree Mooshimeters

  2. Kean May 10, 2014 at 2:14 pm #

    A key thing not mentioned is making sure the QFN PCB footprint used extends out far enough to allow access for manual drag soldering. Many default (e.g. IPC compliant) footprints supplied with PCB software or component libraries aren’t suitable for the drag soldering technique, or have several options for PCB component density. Another tip is to use kapton tape to shield nearby pads from excess solder during this process, although some solder wick makes a pretty quick job of that.

    • James May 11, 2014 at 12:40 am #

      You’re totally right, thanks. On these footprints the pads extend about 15mil past the edge of the part. That’s pretty close to the minimum to use a drag soldering technique.

  3. Duncan Ritson-Elliott May 30, 2014 at 5:40 am #

    Any tips if I’ve got shaky hands?

    • James May 30, 2014 at 10:31 am #

      Make sure you have solid places to rest your wrists. If you have your elbows on the table and your wrists are floating you will tremor much more than if your wrists are firmly planted on the work surface.

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