Toaster oven forgoes Pop-Tarts, reflows solder

For SMD work, solder paste and a heat gun is great. Heat guns aren’t the cheapest thing, so [Karel] decided to make cheap reflow oven out of a toaster oven. With a PCB taken from a laminator temperature control board, the build was fairly successful, so [Karel] decided to add a thermistor to his oven.

There was a problem with placing this thermistor near the board: solder melts in a reflow oven, so [Karel] needed to figure how to connect the thermistor to the control board outside the oven. The solution was crimping thin copper tubing to the thermistor leads and passing that tube through the wall of the oven. Epoxy was used to avoid an electrical short. A low tech solution, but very effective. After applying some solder paste and going in the oven, this board looks very clean. There are a few solder bridges, but nothing a wick can’t take care of.

[Karel] is now working on an update to the temperature controller that controls the oven over a serial connection. Check out the video of a few temperature cycles after the break.

Comments

  1. This is a common problem with thermocouples as well, which you could use if you get the high temp kind. You need to twist the two wires together and then weld the tip using high current.

    One way is to use a 12V battery and clip one lead to the twisted pair just behind where you want to weld it. Clip the other lead of the battery to a piece of carbon plate, you might even be able to use a carpenter’s pencil lead. Then strike the thermocouple across the carbon plate and hopefully you get sparks, heat and a nice weld. Kind of like stick welding.

  2. At some point I need to stop being lazy and come up with my own temperature control solution for my infrawave oven. I had originally set it up with a TechFX Reflow controller which worked pretty good, but now their site is dead and I can’t get the drivers/software anymore. :| I hate setbacks!

    On a related note, anyone else with a Black & Decker Infrawave oven not able to get the bottom element to come on?

  3. Roberto says:

    I found heat guns in the pawn shop for $20. They are no Wellers, but am not sure if these aren’t usable in SMD work.

  4. autofail says:

    neat hack. seems like a pretty smart temp controller to have a serial interface.

    what does a toaster over get you over something like a hot plate for reflowing?

    about the kickstarter…. doesnt pass the smell test for me. are their really no open source temp controllers out there? what does Karel’s temp controller do better than something like this” http://screwdecaf.cx/yatc.html ? why $10,000? is that just to pay for his time before he releases specs? or does he plan on selling these?

    also, kinda lame excuse to build one, heat guns are $13 at harbor freight: http://www.harborfreight.com/1500-watt-dual-temperature-heat-gun-572-1112-96289.html and coupons in the paper can usually get that below $10

    • Reg says:

      Well, a fully programmable oven like this can be used in many applications and has a much greater range than a simple hot air gun.

      As an example, many people inkjet print etch mask for DIY PCBs. This oven can be set, not only to the perfect temperature, but also to the perfect time.

      And sure you can use a hot air gun or hot plate for reflow, but this hack allows you to program the optimal reflow curve. People don’t know this, but heating your ICs up too fast can actually damage them.

      As for the kickstarter thing, looking at the schematics on his blog, I’m guessing he chose $10k because that would be enough for a bulk order of these parts and PCBs. I don’t know if he intends to sell them after he has met his kickstarter commitment, but he clearly states he is open sourcing the whole project.

      I don’t know about anyone else, but I’m getting a kit. It’s only $25 and the u-controller comes preprogrammed.

      -Reg

    • JA12 says:

      “what does a toaster over get you over something like a hot plate for reflowing?”

      My intuition and/or facts may not be totally accurate but here’s few. Anyone, please correct me or add to this.

      For reflow:
      -There can be cold spots on the hot plate and buying a new one or avoiding cold spots might be only possible solutions.
      -Soldering on both sides is possible in the oven.

      On the other hand, hot plates are cheap and can be used as preheat if you do hot air rework/reflow.

      Oven is also handy for drying different chemicals on the board if you make your own PCBs, also for both sides.

      Btw, did someone say ‘inert gas’?

  5. Vonskippy says:

    To solder thermistors use silver solder and braze the connections.

    Silver solder has a melting point almost twice that of regular solder (i.e. around 450C)

  6. Wm_Atl says:

    need more derivative to prevent the over shoot. For me though coming out of industrial controls I would go the cabinet mounted unit and add a solid state relay driven by the controller. Easy to adjust tuning. http://www.factorymation.com/s.nl/sc.2/category.81010/.f

  7. Krazeecain says:

    Who makes pop-tarts in a toaster oven? I just use a normal pop-up toaster.

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