Is it possible to hand solder a DFN package? It's leadless, so it could be tricky. I can't find any videos on YouTube about it, so I'm sort of thinking it as difficult, if not impossible.

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    \$\begingroup\$ I hope you do not mind thomas, I edited your title to be a bit more clear. \$\endgroup\$ – Kortuk Nov 20 '10 at 1:39

Heres a vid I made on reflowing a QFN without hot air http://www.youtube.com/watch?v=d-f-SBC0GrU

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    \$\begingroup\$ That is how I do them, except that I put a large via in the central pad so that I can feed solder in with a soldering iron tip. I also extend the pads, to make soldering easier. \$\endgroup\$ – Leon Heller Nov 20 '10 at 2:57

Its possible, its much easier if the leads are exposed on the sides as well as the bottom.

Hot air is really the best hand approach especially if there is a pad under the package.

You should be able to find lots of tutorials by searching for QFN soldering as that package is the same general structure as a DFN but much more common.

  • \$\begingroup\$ Hmm, so it's not possible with an average iron, only with hot air? \$\endgroup\$ – Thomas O Nov 19 '10 at 22:58

PCB Manufacturing

If you are manufacturing the pcb in house it may be a little difficult to do. Preferably you really need to have plated holes and soldermask. The plated holes are a must as the center pad is usually for thermal purposes and must have a good thermal connection to your ground plane. This means you will have to have several of them across this center pad. There are some via techniques that you can use at home that will work, but I do not have any experience with them. You can get away with no soldermask, but it makes life much easier.

The Footprint

There are 2 things you can do to make your soldering life easier while making the footprint. The first is to extend your pads out long enough that you can stick a soldering iron to it. The second is to round the corners of the pads on the inside of the chip. Typically I see students have issues with solder liking to bridge from the center pad to the others. They have found that rounding the back corners has extremely helped prevent this.

Time to Solder

  • Apply flux.
  • Place your IC.
  • Tack 1 pin on each corner down by pushing solder into the pad along your extended pad.
  • Flip your board over and apply solder to all of your vias. Make sure you get it nice and hot first, it will take it a bit longer for the heat to transfer to the IC. You want the IC to be hot when solder gets to it. This is a bit hard to tell so you will just have to do some guess work. You have put enough solder down when your vias becomes completely filled with solder.
  • Flip it back over and continue soldering all other pads with the method of pushing the solder into the pad.
  • Check the board and your done.

You can hand assemble or disassemble QFN/DFN with a toaster oven (or hot plate). It's worth learning because the process is about the same as a real SMT line.

The toaster oven is $30. Solder paste is $3 from dealextreme.

Unlike hand soldering, there is no technique to learn -- just cook it in the oven until the solder melts. Then turn it off and let it cool down.


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