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)I'm considering buying a rework station (Aoyue AO968A+220V). What could I expect to solder consistently using hot air that's not "possible" with solder iron?

What I've been avoiding from a soldering point of view is packages with less than 0.8mm pitch, and no-lead packages. Obviously BGAs has been totally out of the question.

The purpose of the soldering is prototyping and the alternative would of course be to get the PCB manufacturer to also assemble the board, but that might be less flexible solution.

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  • \$\begingroup\$ Hot air can solder just about any part. That's what the commercial reflow ovens use. It just depends on the aperture of the opening to the parts. \$\endgroup\$
    – Aaron
    Jan 19, 2021 at 0:45
  • \$\begingroup\$ @Aaron One would perhaps expect that, but I've done my homework: according to the answers to electronics.stackexchange.com/questions/42322/… you can't just copy the process. It seem trying to reflow a board with a hot air gun doesn't seem to be a reliable option. And of course there's a few components that are not designed for reflow soldering. \$\endgroup\$
    – skyking
    Jan 19, 2021 at 0:57
  • \$\begingroup\$ @Aaron The question is also about what could be done by hand. Those factories seem to place 0402 components without a blink of the eye, while I will drop it on the floor never to be seen again while trying to pick it up with the tweezer. \$\endgroup\$
    – skyking
    Jan 19, 2021 at 1:01
  • \$\begingroup\$ We used to solder the CC2400 by TI, with a hand held hot air gun. It's a leadless chip with a small pitch. It just depends on the skills of the person doing to soldering. \$\endgroup\$
    – Aaron
    Jan 19, 2021 at 1:19
  • \$\begingroup\$ re: hot air - yes just get it. That being said, with practice, flux, and some kind of hold-down device, the iron will do 0.65mm pitch without much trouble. \$\endgroup\$
    – Pete W
    Jan 19, 2021 at 2:02

4 Answers 4

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What could I expect to solder consistently using hot air that's not "possible" with solder iron?

Anything with pads below the component. Thermal pads, QFN, BGA etc.

Though mostly hot air stations are a complementing tool to a solder iron, mainly used for removing components, particularly when you need to remove something without damaging the part.

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  • \$\begingroup\$ While you can get a BGA to solder flow temperature, there's more to it than that. Generally one shouldn't count on being able to work with BGA's freehand, though yes, sometimes with care you luck out - eg, was sent a prototype with a BGA MCU badly assembled, figured there was nothing to loose so heated it up, gingerly nudged it with tweezers and watched surface tension pop it into alignment where it settled and subsequently took a program. But not something you can count on. \$\endgroup\$
    – Chris Stratton
    Jan 20, 2021 at 18:04
  • \$\begingroup\$ @ChrisStratton I'd say it depends entirely on how big they are. Smaller parts are much easier. But well, generally I avoid picking BGA parts in the first place, because they are horrible to work with. \$\endgroup\$
    – Lundin
    Jan 21, 2021 at 7:34
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I'm considering buying a rework station (Aoyue AO968A+220V). What could I expect to solder consistently using hot air that's not "possible" with solder iron?

Hot air is most useful for rework/repair of parts rather then primary soldering. You can, in a pinch, use hot air for reflow of small boards, but like your links discusses this is impractical for large boards.

The purpose of the soldering is prototyping and the alternative would of course be to get the PCB manufacturer to also assemble the board, but that might be less flexible solution.

Buy (or make) a reflow oven. This is much faster, and even cheap IR ovens will be much more reliable than doing things by hand. A basic T962 is only a little more expensive than that Aoyue and can easily reflow larger boards with 0402 parts and 0.5mm pitches. Conversely, a DIY reflow oven using a toaster oven or similar would be a lot cheaper and still much more effective than hot air.

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Soldering iron, hot air station, preheater, hot tweezers, and even a desoldering iron are basic tools any serious and efficient prototyper needs, IMHO.

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  • \$\begingroup\$ Two hot air stations, so you don't have to change hot nozzles when you need the other one. \$\endgroup\$
    – Simon Richter
    Jan 19, 2021 at 9:53
  • \$\begingroup\$ You're spoiling yourself :) \$\endgroup\$
    – Robert Jonkman
    Jan 19, 2021 at 11:42
  • \$\begingroup\$ I have two JBC irons at work so I don't have to spend the five seconds it takes to change tips lol. But I wish I had three. \$\endgroup\$
    – DKNguyen
    Jan 20, 2021 at 16:00
  • \$\begingroup\$ Tweezers are fun, but hard to justify. Recently discovered that the silly "hot knife" tip in many knock-off tip assortments is great for removing SMD passives, just put it beside and dab in some wire solder to get heat to both pads. \$\endgroup\$
    – Chris Stratton
    Jan 21, 2021 at 19:48
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As a (partially) laptop repairman and (partially, unproffessional) device engineer, I find hot air the most comfortable tool to work with, much more useful than soldering iron. Anything is easier to replace with hot air rather than soldering iron, from 0201 resistor to some TQFP-144 or larger BGA chips. But then again I work with SMD or BGA components a lot as well. You can replace anything smaller than laptop CPU or dGPU, which are simply too large for hot air station (and require training).

As for specifics, I STRONGLY DISCOURAGE you to buy anything under 200$. From my experience, they tend to overshoot the temperature a lot during turn on (to heat up quicker, I presume), and they hold the temperature poorly (can be as bad as 70C jumps while the temp is fixed, into the hotter area too!). Overheating can kill the chips, if you don't control the temperature.

If you want something universal for small and larger chips, I use Quick861DW, which is still on the affordable side, and it holds the temp really well, can handly about anything. Downside: it's a little louder than I would want to when I don't need it anymore and put it back onto the stand. I recommend to find some Youtube reviews where someone measures temp stability. 30C temp jumps are ok, more - not so much.

Overall, aim at 700W+ and you should be set for whatever life throws at you, phone or motherboard.

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  • \$\begingroup\$ Repairing things with high density and surrounding parts can indeed point towards needing a high quality tool and a lot of care. At the same time, one should not let the perfect be the enemy of the good. What one can do with a <$50 hot air tool compared to any soldering iron is huge. If someone is on the fence in terms of getting the capability, starting cheap can be a huge step up from nothing; but nothing against tools with more heat capacity and tighter temperature control, especially for boards with internal planes and working near heat-sensitive connectors or mechanical parts. \$\endgroup\$
    – Chris Stratton
    Jan 20, 2021 at 18:08
  • \$\begingroup\$ I used 150$ station and killed a pair of chips on customer devices because you set the temperature to 350 and it blasts 320-420 (jumping up and down; found out later of course, at the time I had no idea wtf happened). Cheap tools are simply dangerous for your components. If you buy cheap tools, at least watch 3-4 video reviews if possible. Preferable more detailed than "look, I unsoldered a chip, it works". 250$ pretty much guarantees you won't have weird stuff going on. Been using 300$ 861dw for 2 years, killed component count is 0 \$\endgroup\$
    – Ilya
    Jan 21, 2021 at 8:57
  • \$\begingroup\$ Thermally damaged chips are quite unusual; if you're working with large BGA flip chips having internal solder, on many layer boards that soak up a lot of heat, you might possibly get into the territory of concern (though freehanding BGAs is always dubious). But remember that this is a design site, not a laptop repair one - for most engineering lab purposes a cheap tool works just fine; in the end skill matters more than tools. In the exceptional cases where something better is needed, get it. But the cheap tool is a huge improvement over having no tool of the sort at all. \$\endgroup\$
    – Chris Stratton
    Jan 21, 2021 at 19:44
  • \$\begingroup\$ I agree that skill matters more than tool. but try some 350 degrees on a chip for 3 minutes, and you risk losing it. Or with 320 degrees with cheaper station. I'm not saying you need expensive tools. In fact, 250$ is still a low end. The idea is that if you screw something up, it will be because of you and not the tool. So get a low end 250$ station. Here in repair business we use 1000$ hot air stations too, but they're an overkill for any task imo. The tool doesn't have to be expensive, it has to be good enough not to be the reason of problems. 250$ is the cheapest good quality, again, imo \$\endgroup\$
    – Ilya
    Jan 22, 2021 at 13:14
  • \$\begingroup\$ The kind of thermal damage you are worried about just doesn't happen with the types of IC's the asker is going to be using. For purposes of the question, you're needlessly fear-mongering and falsely giving the idea that a acquiring a basic key capability costs more than the $40-60 it actually costs to revolutionize capabilities. Again, laptop repair has very little in common with typical prototyping. \$\endgroup\$
    – Chris Stratton
    Jan 22, 2021 at 17:51

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