Reflow oven insulation

My reflow oven is very low tech. I haven’t modified it at all and even so I’ve been using it to reflow thousands of PCBs ever since LowPowerLab started.

It has top and bottom elements, but the heat does not distribute evenly, understandably so – you can see through it. Sometimes PCBs that were on the inside edge would take longer to reflow. Air escapes in several different places all over the oven enclosure, especially on the bottom front and back:

It’s time for a small improvement, adding some basic insulation in an attempt to stop air flow, keep the heat in and hopefully make it more evenly distributed.I folded aluminum foil to get two layers and then folded the edges to match the length of the oven (I used a small tape measure to estimate how much foil I need). Then used high temperature tape to attach it in every inch or two. It was easier to apply the foil on each side – top, bottom, left, right and door. So each side would get a double layer or aluminum foil, carefully taped to each other and to the metal enclosure of the oven.

It turned out quite well. The foil is pretty sturdy and opening the door and inserting the tray holder does not interfere at all.

Finally, I cut a window so I could see through. It didn’t even need to be so big since even a small amount of light will get reflected all over by the aluminum foil.

I ran some tests and here are the observations:

  • The temperature rises significantly faster
  • Once it’s turned off, the temperature keeps rising to a higher point and much quicker, so I will need to stop it sooner than before for the soaking zone
  • When I turn the oven back on (after the soaking zone), the temperature picks up much faster. Before it would keep dropping for 10 seconds after restart, now it’s only a few seconds before temperature starts going north
  • The oven metal enclosure is cooler to the touch, previously it was too hot to touch after it heated up, a sign that the heat stays inside

Once I do more reflowing I will post updates, but so far so good, I think the heat is preserved a lot better and should be more evenly distributed within the oven. Automating this little oven would be even better, but for now I have a better reflow oven than what I started with.

5 thoughts on “Reflow oven insulation

  1. Looks good. I was thinking of getting high temp insulation and putting it inside in the empty space between the oven and the outer case. I may try the extra foil. I only had put it on the glass and the bottom since the bottom elements don’t heat as much.

    Here is part one of my setup
    http://www.mobilewill.us/2013/07/another-toaster-reflow-oven-part-one.html

    Doing the automated part is so worth it. I took all my research and my post has everything you need.

  2. Looks good. Do you have any control for the temperature like a PID controller to follow a typical reflow curve? or do you use manual control?

    • It’s all still manual at this point. The insulation was a BIG improvement, reflow takes much less time (oven heats up quickly and keeps temperature). But I will plan to add a PID controller sometime in the future. But even so, to fully automate it you need to be able to open the door or start moving air out after the reflow phase (maybe with a fan – but I don’t plan to cut out any holes for that). So mauybe some door servo motor solution can be devised for that. For now I’m happy with how it works manually… it takes a few minutes every time, no big deal.

      • Thanks for the quick answer. So you only put the pcbs and when you see they are soldered, stop the oven and remove the pcbs, don’t you? In fact a very good improvement

        • I stop it at 120C, it keeps going up to almost 170C (soaking zone), then I turn it on again until it reaches ~220C, by then all boards should reflow and I turn it off, let it sit for 5-10 seconds (reflow zone), then open the door. It only takes about 4-5 minutes in total.

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