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I don't have any soldering station but I need to solder the qfn package chip so how I solder it using a normal soldering iron.

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    \$\begingroup\$ It can be done. There are some video's on YouTube, search "Solder QFN by hand". \$\endgroup\$ – Steve G Mar 11 at 12:57
  • \$\begingroup\$ What do you mean under "normal soldering iron"? A normal soldering iron for this job should have at least 45W of power with 0.2mm conical tip, thermally controlled to ~380C if you use regular 40/60 solder. \$\endgroup\$ – Ale..chenski Mar 11 at 18:08
  • \$\begingroup\$ @Dhruv Does the thermal pad of your particular IC need to be soldered? Or, is that optional? If you can't tell off-hand, post a link to the datasheet, we'll have a look. \$\endgroup\$ – Nick Alexeev Mar 11 at 18:08
  • \$\begingroup\$ @NickAlexeev, yep, the thermal pad can't be soldered without hot air pencil/gun, true. \$\endgroup\$ – Ale..chenski Mar 11 at 18:12
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I normally put some solder paste on the pads, place the QFN on the board, and reflow with hot air. With some trial and error you learn how much solder paste to put, but you really need quite little.

I have seen it done with the soldering iron as well, by following the process above, but instead of heating the device with hot air, you hold the device in place with tweezers and heat the pins one at the time with the tip of the soldering iron.

You can find plenty of videos on how to do it on Youtube.

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If the PCB has not had any parts mounted on it yet (or at least none on the bottom) you could try a skillet. Dispense solder paste/flux, place the part, and heat until it melts. I have not tried this personally (normally I use a solder paste stencil and reflow oven). Of course you should not use the skillet for food ever again, particularly if you use lead-based solder, but even the flux may not be especially healthy.

Hot air is another way, but be careful with a cheap uncontrolled heat gun, it's pretty easy to fry FR4 let alone the chip with a $10 paint stripper heat gun (at least I found that).

If you don't have solder paste you might be able to get away with tinning the pads, applying lots of liquid flux to the chip and to the pads and heating it until the chip settles down into position. If you've designed the pads according to recommendations and placed the chip close to the correct position it should be pulled into alignment with the pads by surface tension of the solder.

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    \$\begingroup\$ Remember to not use the skillet for food after you contaminate it with lead and flux \$\endgroup\$ – BeB00 Mar 11 at 18:10
  • \$\begingroup\$ @BeB00 Good point, I'll add that to the answer. \$\endgroup\$ – Spehro Pefhany Mar 11 at 18:11

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