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I'm doing a project and I have a PCB which needs surface mount components attaching to it. One component has already been attached, and I have some 138deg solder paste in a syringe.

This is possibly going to sound very stupid, but is it feasible to use my kitchen oven or a similar household device to heat up the solder? This is just a one off for me and I am not planning on doing any surface mount soldering in future, and I do not have easy access to a proper reflow oven.

All the components will be mounted on one side if that's an issue.

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    \$\begingroup\$ What kind of parts? If they all have pins (no bga or pads under the part) then you just solder them by hand. You probably don't really want to do reflow in the same oven you bake food in. \$\endgroup\$ – JRE Apr 20 '17 at 15:21
  • \$\begingroup\$ check the temperature specs of your components for reflow and see if your oven can follow the strictest of the requirements. (It probably won't) \$\endgroup\$ – ratchet freak Apr 20 '17 at 15:22
  • \$\begingroup\$ While the kitchen oven can reach the soldering temps just right, I think it is not nearly as fast as needed. \$\endgroup\$ – Vladimir Cravero Apr 20 '17 at 15:24
  • \$\begingroup\$ Most of them do have pads under the part, yes \$\endgroup\$ – ram Apr 20 '17 at 16:30
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    \$\begingroup\$ I recommend a prototype service like Macrofab. \$\endgroup\$ – klamb Apr 20 '17 at 17:51
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Lots of people use toaster ovens and electric fry pans for reflow. It can get a little touch and go with lead-free solder, and I recommend leaded solder.

Large kitchen ovens likely don't have the oomph to bring things to temp fast enough, and your IC's may not tolerate the slow temperature profile.

I think whatever appliance you use, you should dedicate to reflow, and not use it for food.

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    \$\begingroup\$ +1 for not using it for food afterwards. \$\endgroup\$ – Arsenal Apr 20 '17 at 15:29
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    \$\begingroup\$ Make sure other people don't use it for food, either. Tape it shut with a big warning label or something and don't leave it in the kitchen. \$\endgroup\$ – user2357112 Apr 20 '17 at 18:00
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Can you? Yes. Will it work every time... Maybe not!

There are two reasons for this.

  1. Temperature profile and timing.

Reflow is done using two temperatures, a pre-soak temperature and a reflow temperature as shown below.

enter image description here

As such, you REALLY need to use two ovens to do this right, quickly switching it from one to the other after the pre-soak time.

  1. Oxidation

Commercial reflow is usually done in a nitrogen gas so that oxidation will not occur in the solder and joints during the molten phase. That's rather hard to do in your domestic environment.

IN ADDITION:

Not all components can withstand the same heat. Some parts are MUCH more sensitive to being "cooked" for too long, especially plastic parts like connectors and the like. If you are doing this at home it is prudent to identify those and manually add them after.

SAFETY CONCERNS

Other than the obvious... "Don't burn yourself..." it is not a healthy idea to solder using the same oven you plan on baking that apple pie in later in the day. Lead and other noxious chemical fumes will permeate the oven.

Also, if you are married, severe tissue damage can occur in the rectal area from the insertion of your spouses footwear when she, or he, finds out what you did.

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  • \$\begingroup\$ With regards to temperature profile, there are several open source controllers (mostly Arduino based) that convert cheap electric toaster ovens to temperature controlled reflow ovens. \$\endgroup\$ – slebetman Apr 21 '17 at 5:07
  • \$\begingroup\$ Not if he's married to one of these polyclay addicts ;) \$\endgroup\$ – Dmitry Grigoryev Apr 21 '17 at 12:45
  • \$\begingroup\$ @slebetman yes I have heard of those. Issue isn't the temperatures though it's the 3-6C per second ramp before the reflow and them getting the cooling right. Though some toasters might be able to handle it, it is definitely not within your regular electric, or gas, stove's capability. \$\endgroup\$ – Trevor_G Apr 21 '17 at 19:54
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If you want to learn how to solder SMT components by hand in an unimpeachable fashion, I would recommend watching some of the Youtube videos by IPC (J-STD-001) certified soldering teachers. You will need pure IPA (isopropanol) not drugstore rubbing alcohol, cored solder in appropriate size(s), appropriate liquid flux and preferably a decent stereo microscope or at least a magnifier. And, of course, a clean well-lit work area, preferably with ESD precautions.

I would not recommend try to solder a one-off with solder paste. I do it myself with a stencil but the oven parameters are known-good for most boards. Even dispensing appropriate amounts of paste on each pad without a timed pneumatic dispenser is not easy (the solder paste behaves in a fairly unpleasant manner because it's not really a liquid- it's a bunch of little balls of solder in a matrix of liquid flux). Getting the oven right could result in damage to board. Sn63Pb37 leaded solder temperature-time profiles are relatively forgiving, but unleaded solder means running some parts very close to the point where damage occurs so the parameters have to be well controlled.

For something like a resistor you clean the board with IPA, maybe the part if it is not pristine, then tin one pad and slide the part in to solder one side, then solder the other pad. There are some subtleties as to where exactly you put the solder during the process- to get the part to wet, and then feeding it in at the junction of pad and part, while heating both with the iron. Then you clean and inspect and move on to the next. It takes a while but the results can be very good.

If you insist there are people who are successful using nothing more than a skillet but you will want to not use that for food afterward, especially if you are using lead-based solder. Make sure you wash your hands after handling the paste (as a paste it's worse than wire solder) and (if applicable) don't do it at all if there is any chance of pregnancy.

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You probably wouldn't want to use a regular oven for three reasons:

  1. Its probably not a good idea to put lead where food is.
  2. A larger oven has more uneaven heating because there are more convection currents
  3. The temperature profile of the solder paste would be hard to duplicate in a larger oven

Use a smaller toaster oven, get one from a second hand store. Look up the temperature profile for the paste you have, you need to time the temperature profile to that of the solder, you will get better results.

If this is just a one off PCB and you won't do it long term, find a cheap assembly place.

Another option is skipping the oven all together. A hot air rework station will probably do just fine in your case. There are numerous videos and tutorials on the web that show how to solder or use a hot air rework station with QFN's QFP's and other components. This is a good option if you have a low part count on the PCB or low quantity production run ~(<3 PCB's).

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    \$\begingroup\$ It's not just about the solder, the reflow temperature profile of most components can also be critical. \$\endgroup\$ – Trevor_G Apr 20 '17 at 17:16
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    \$\begingroup\$ Yes it is, probably not for hobbyists and low production runs though (If a part fails they have the time an means to replace the IC). If your doing a large production run, your going to want to control all the variables within tight tolerances. The worst thing in my mind is moisture and blowing up parts. \$\endgroup\$ – laptop2d Apr 20 '17 at 17:50
  • \$\begingroup\$ Assembly place for one PCB?? \$\endgroup\$ – pipe Apr 20 '17 at 18:54
  • \$\begingroup\$ @pipe, I didn't say it would be cheap \$\endgroup\$ – laptop2d Apr 20 '17 at 19:18
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Please don't use microwave oven for the soldering techniques. The ovens that we use in home, is using the microwaves to get the heat. So you know the basics of microwaves and the semiconductor manufactures will strictly warn us about the ESD protection. So components may fail if you are using a microwave ovens. Instead use the IR ovens for the purpose. Maintain the temperature profile...enjoy

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    \$\begingroup\$ Indeed, nobody suggested using microwave ovens, obviously, and I'm quite sure OP wasn't thinking about this type of oven. What was suggested was toaster ovens, which can work, even if it's certainly not as practical as dedicated IR ovens (which cost an arm and a leg). \$\endgroup\$ – dim Nov 9 '17 at 8:53

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