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What are the advantages and disadvantages of using a reflow oven vs a hot air station for prototyping SMD PCB? Do you need an oven or would an air station work?

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    \$\begingroup\$ Hot air gun is slip shod. Hot air station is another matter. \$\endgroup\$
    – DKNguyen
    Jan 18 at 20:27
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    \$\begingroup\$ @FourierFlux If it's a BGA part I would just take it into the shop. There can be hundreds of solder balls on a BGA part an each one needs to be soldered correctly with the proper thermal profile or it won't work (the impedance will be wrong, balls can crack ect). \$\endgroup\$
    – Voltage Spike
    Jan 18 at 20:29
  • \$\begingroup\$ If you want to place SMD pieces on a board, hand soldering is still a good option for most packages except something like BGA. Saves you having to buy more equipment, although it can take some practice. \$\endgroup\$ Jan 19 at 2:34
  • \$\begingroup\$ I have recently assembled some boards using an ordinary "toaster oven" model with a convection fan. I put down solder paste from a syringe (no stencil) and place components with tweezers. It works OK on 0603 parts. Probably it would be OK with 0402 also. You have to get fine solder paste and a very narrow syringe nozzle. A BGA would be tricky because the amount of paste is not totally consistent, and you can't inspect under the BGA to look for solder bridges or voids. \$\endgroup\$
    – mkeith
    Jan 19 at 7:38
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    \$\begingroup\$ For production you always use a reflow oven, obviously. For prototypes, it should be noted that you only need hot air station/heat plates etc with IC that have a cooling pad underneath them, and perhaps with particularly nasty fine pitch QFN. Hot air and paste is messy, using a solder iron is always the way to go whenever possible. For BGA I would use an oven and a professional contractor, because you need x-ray to verify them... I avoid designing in BGA like the plague, so I don't have a lot of experience with them. \$\endgroup\$
    – Lundin
    Jan 19 at 8:52

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The advantage of a reflow oven is that it evenly heats everything in a controlled and automated way. Assuming the oven is well calibrated you can precisely reproduce the manufacturers reflow profile, hopefully resulting in reliable soldering and very low probability of damage to components. The disadvantage is usually cost, and that cheap reflow oven often do not precisely track the programmed profile.

The advantage of hand reflow with hot air is that it is fast, doesn't require a reflow oven, and for prototyping can work quite well. The disadvantage is that it is hard to reflow large boards evenly, so except for very small PCBs you will probably end up applying too much heat to some areas and too little to others. Further problems occur with plastic components, which tend to be hard to reflow without melting because you don't have that fine control over temperature. For example, I would not use hot air to reflow a large 10" wide PCB with many surface mount components and plastic connectors, but I have done 1" PCB modules with hot air and found that it worked fairly well because the boards were so small I could evenly heat them.

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    \$\begingroup\$ Also the oven will make soldering SMD parts with connections under the package like thermal pads or no-lead terminations much easier. I'm not sure if there's even an acceptable way to solder these with a hot air iron. \$\endgroup\$
    – vir
    Jan 18 at 17:34
  • \$\begingroup\$ What is the consequence of not uniformly heating the board? Basically, can you treat hot air station as like a soldering iron and go component by component? \$\endgroup\$ Jan 18 at 18:00
  • \$\begingroup\$ @FourierFlux Provided you are careful, you can generally do that. However, if can be quite difficult to go component by component on tightly packed boards, meaning that you may heat each item several times, which can lead to damage if you aren't very careful. Similarly, it requires some practice to reflow larger chips without damaging things like plastic connectors if they're too close. If you're designing the board, you can make your life easier by putting heat sensitive items far from anything else that will require a lot of heat. \$\endgroup\$ Jan 18 at 18:07
  • \$\begingroup\$ @vir Reflowing leadless packages like QFNs or even BGAs using hot air takes some practice, but is not that difficult once you get the hang of it. The hot air will melt thermal pads too, although it may take longer if you must heat a large GND plane with just air. \$\endgroup\$ Jan 18 at 18:10
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    \$\begingroup\$ @FourierFlux I suggest watching a few YouTube videos of people doing reflow work, then getting a hot plate, heating to ~150C and then trying your luck with hot air. Unless your trying to do lots of 100+ ball BGAs this is something you can probably manage to teach yourself. Maybe practice on some old PCBs if you're really worried. \$\endgroup\$ Jan 18 at 22:59
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I have done a lot of at-home assembly of SMD boards. I do a mix of one-offs and 10s of boards, with anywhere from a few to hundreds of components. People vary in which type of assembly they prefer. For me, if there are only a few SMD components on a board, and they're not too fine pitch (e.g. 0603 passives and SOT-23 or SOIC-8 size), I will hand solder them with an iron. Any more than that, and I will get a stencil and reflow. Stencils are quite cheap now, I see no reason to manually dispense paste from a syringe, which I find pretty finicky.

For the actual reflowing, I started with a hotplate. This was OK, but I found it a little touchy, and tended to burn the PCB. I switched to an unmodified, cheap toaster oven, which I have used to do many boards. I used a thermocouple the first few times I did this, and you may want to do that to get a feel for it, but mostly found it unnecessary. I used the following "profile", turning on a stopwatch when I turned on the oven:

  • Set oven to 150C
  • Wait until 1:30
  • Turn off oven
  • Wait until 2:00
  • Set oven to max
  • Wait until solder reflows
  • Turn off oven
  • Wait 10 seconds
  • Open oven
  • Wait a few minutes and remove boards

Unless you have especially sensitive components (like WS2812 LEDs, which I have found best to hand-solder), this works really well, is cheap, and easy. Last year I built a temp-controlled reflow oven using the Controleo3. It is more precise, which is important if you have more sensitive components. But, for most hobbyist use, it's overkill.

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  • \$\begingroup\$ I replaced all the heat controls on a toaster oven with a heat-ramp-soak temp controller from Omega Instruments and a thermocouple I put in contact with the board. I also beefed up the insulation a bit. \$\endgroup\$ Mar 27 at 18:50
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Ovens are generally easier and are certainly more repeatable. But the cost is significant.

I use a cheap hot air station for prototyping and get good results. It can be tricky to solder leadless components without overheating them. Especially when some pins go to large copper areas (or vias to ground/power planes).

So, I now have a cheap preheater to go with my cheap air station! You heat the entire board to some intermediate temperature, which includes the internal planes and through-vias. Then you only have to supply a little heat from the air station to make the solder flow.

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    \$\begingroup\$ Preheaters are awesome. Even if you're just using an iron. \$\endgroup\$
    – DKNguyen
    Jan 19 at 1:57
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    \$\begingroup\$ You can use a toaster oven (one with a convection fan). I have done this. You have to try different temperatures and durations to find what works. Obviously, don't use the oven for food once you put a PCB in there. \$\endgroup\$
    – mkeith
    Jan 19 at 7:40
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    \$\begingroup\$ @mkeith -- I replaced all the heat controls on a toaster oven with a heat-ramp-soak temp controller from Omega Instruments and a thermocouple I put in contact with the board. I also beefed up the insulation a bit. \$\endgroup\$ Mar 27 at 18:49
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I totally disagree with the statement that oven heats with best control. It really depends on the quality of the oven. Simple Chinese ovens need a lot of attention and setup to get a stable result. We use ovens just because it's a bit faster for a big amount of similar PCBs.

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