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Ben's Home-Brew Solder Reflow Oven 2.0 Episode -- Episode 116

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element14's The Ben Heck Show

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Ben's fed-up with the difficulty of soldering surface-mount components by hand and builds a new reflow oven to keep in his shop. He transforms an inexpensive toaster over into a vital tool for electronics engineers and tinkerers. In this updated oven, he uses two thermal couples to ensure even heat distribution and effective reflow.
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  • Yeah, I'm a couple years late on this, but I was wondering if anyone could explain the reasoning for the "ramp" value in the profile. I'm putting together one and it will not heat beyond around 112°C. My oven is a bit larger (needed to fit the boards I plan to do), which I suspect is part of the issue and was wondering how and why the ramp value was determined. I'm assuming that part of the reason is not to heat things too quickly, but how those numbers were decided upon, I haven't a clue.

     

    It appears that when the variable 'state' is 1, it uses the PWM value for warming up, then transitions to state 2 where it just uses the relay pin as a digital to maintain the temperature for the soak period. States 3 & 4 do what 1 & 2 do but for the reflow. Problem is with the values in the profile, this oven is not going to heat up enough to get to state 2. let alone 3 & 4.

    I know I'm probably going to end up solving this myself, but if anyone can give me any pointers so I'm not over cooking the boards.

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  • Yeah, I'm a couple years late on this, but I was wondering if anyone could explain the reasoning for the "ramp" value in the profile. I'm putting together one and it will not heat beyond around 112°C. My oven is a bit larger (needed to fit the boards I plan to do), which I suspect is part of the issue and was wondering how and why the ramp value was determined. I'm assuming that part of the reason is not to heat things too quickly, but how those numbers were decided upon, I haven't a clue.

     

    It appears that when the variable 'state' is 1, it uses the PWM value for warming up, then transitions to state 2 where it just uses the relay pin as a digital to maintain the temperature for the soak period. States 3 & 4 do what 1 & 2 do but for the reflow. Problem is with the values in the profile, this oven is not going to heat up enough to get to state 2. let alone 3 & 4.

    I know I'm probably going to end up solving this myself, but if anyone can give me any pointers so I'm not over cooking the boards.

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  • in reply to MichaelL65

    I consulted Ben and this is what he explained to me. You have to bring it up to temperature at a certain rate, then hold it at a certain temperature for a certain time, then spike the temp, then bring the temp back down.  The theory behind that is warming the parts up first then spiking the temp to flow the solder, but only for as long as needed, then allowing the whole thing to cool. Parts have a rating that will tell you how hot they can get before being damaged. Does that answer your question?

  • in reply to makerkaren

    That's kinda what I thought. I did find some further information after digging some more and it appears that the "ramp" phase is supposed to increase temperatures no faster that 2-4°C/sec, which this oven had no intention of doing even at 100% power (Ben's program was trying to do that at about 30% - probably right for the oven but a little more info in the video or in text would have been nice). I also found out that in spite of my oven implying with the dial it would reach 230°C, it never got above 147°C. That means it would ramp & soak but was never going to spike. Unfortunately that killed the project, but I was able to talk my employer into buying a real reflow oven after that (Prices have come down a LOT recently).

     

    In case it helps anyone else, if it takes more than about 30-60 seconds to heat to the 140° point, you should change the profile of

     

    75,140,45,125,205,20

     

    to something more like:

     

    255,140,45,255,205,20

     

    and if your oven is really slow getting to the soak level, it may never reach the spike.

     

    Thanks, Karen!