Soldering irons are the primary tool used for soldering, and we use ours all the time for soldering. But for leadless parts, like QFNs, or ultra-tiny components that need rework, hot air can be superior!

The nice thing about hot air is that its just air - this means there's no physical 'tip' nudging the part to heat it up. This is great for delicate components. Another thing is that you can heat up an entire area at once, great when you want to rework a small leadless part because the pads are underneath the chip. The annoying thing is it takes a long time to heat up a board especially if there is a ground plane involved. You can try preheating the board if you have a preheater (basically a small reflow oven works fine).

We decided to go with a Hakko pencil tip hot air station. This station has some things going for it: there's an internal pump, its easy to use and it has a fine tip for small component rework. We picked it up off of ebay for about $150 which is lower than new but worth the risk of it not working out. We recommend getting a non-'chinese clone' air rework station since its common for a poorly made one to work ok at first and then die 6 months later because the pump is low quality, or the heater gets damaged. The old 'black box' Hakko's are discontinued and replaced with the new violet/yellow FX series, so it may be easier to get them off ebay for a discounted price

However, we recently decided its not 'good enough' for us so we bought a Hakko 852 off ebay for $400. We'll post up here when it comes in about whether we like it more.

In Practice

We use the Hakko Hot Air station for SMT rework, especially removing small resistors/capacitor or removing/reflowing ultra-small QFN's or UDFNS.

This is a nice video with a lot of details on using hot air reflow. Its slow but it works!

In this video, we use it to remove some very very small 0402 resistors without damaging them so that they can be measured out of circuit:
If you use our syringe technique to lay down paste, you can even 'reflow' a small board by bathing it in hot air and slowly working from one edge of the PCB to the other. This may not work well with very thick boards with big ground planes but it is probably good enough for making breakouts and such.

This guide was first published on Jul 29, 2012. It was last updated on Jul 29, 2012.

This page (Hot Air Tools) was last updated on Jun 21, 2012.

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