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Thread: Looking to buy a reflow oven

  1. #1
    Senior Member joe_prince's Avatar
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    Looking to buy a reflow oven

    Does anyone have a good reflow oven they can recommend? Looking to get one for small quantity, small board size, personal use. Would like to spend no more than $400 (if that's possible).

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    Several years ago I was looking into this and came up with an web post somewhere (Dangerous Prototypes? [edit - they do have some posts on toaster oven reflow but it looks like that wasn't my original source...I'll keep looking]) that said they just bought a cheap toaster oven, turn it on broil until the solder melts, then turn it off and open the door. I thought that was a little too simplistic so I semi-followed this:

    https://www.sparkfun.com/tutorials/60

    The actual toaster oven I bought was a Hamilton Beach because (A) it had convection fans and (B) it was on sale.

    I didn't go through the steps of taking it apart and making a separate controller for the fans and elements; I just have a '328, thermocouple, piezo beeper, 2 line LCD, 'start' and 'reset' pushbuttons, and a PowerSwitch Tail AC controller controlling the oven.

    The oven controls are set to 'broil' and 'always on' and the 328 runs a pretty simple cycle of:

    1. Oven on till 150C or 3 minutes (preheat)
    2. Oven off for 30 seconds (soak)
    3. Oven on till 225C or 2 minutes (flow)
    4. Oven off till cooled to 200C
    5. Beep to signal to open door
    6. Beep when temp has dropped to 50C

    I've been using this since 2012 and have run boards up to 20cm x 10cm and haven't had any real issues. The reflow graph isn't great compared to the ideal you see published in most data sheets but so far so good. Total cost was under $150.

    [edit 2 - found the original post: http://electronics.stackexchange.com/a/1187 ]
    Last edited by potatotron; 12-09-2015 at 06:34 AM.

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    Senior Member Constantin's Avatar
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    See here for some pics and a description. Probably cost about $150 in materials and works.

    I hear the $285 eBay jobs require modifications to work well.

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    Quote Originally Posted by joe_prince View Post
    Does anyone have a good reflow oven they can recommend? Looking to get one for small quantity, small board size, personal use. Would like to spend no more than $400 (if that's possible).
    I use the reflow oven from beta-store
    https://www.beta-estore.com/rkde/ord...list.html?wg=1

    costs are between 130 and 480 Euro, depending on the kit.

    Efficient 'printer' to bring solder paste onto boards is very useful.

    otherwise, the method described by poatotron is sufficient.

    oven itself is a commercial pizza/toaster oven (50-60 Euro)

    added value is controller and solder paste transfer printer

  5. #5
    Senior Member joe_prince's Avatar
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    potatotron

    Thanks for the great information!

    Quote Originally Posted by potatotron View Post
    The actual toaster oven I bought was a Hamilton Beach because (A) it had convection fans and (B) it was on sale.
    I just read through that SparkFun post (good stuff there) and had a few questions about the oven itself. For the burners in the oven, do I need top and bottom burners? If so, is a convection oven that has 2 top and 2 bottom burners better than that which has only 1? I didn't see many ovens with the fans you're talking about...do you feel that heat distribution would be uniform enough without the fan?

    And for the thermocouple, are you using type K as well? Was thinking about possibly having multiple thermocouples and averaging their values to get a better idea of the heat distribution.

    Quote Originally Posted by potatotron View Post
    The oven controls are set to 'broil' and 'always on' and the 328 runs a pretty simple cycle of:

    1. Oven on till 150C or 3 minutes (preheat)
    2. Oven off for 30 seconds (soak)
    3. Oven on till 225C or 2 minutes (flow)
    4. Oven off till cooled to 200C
    5. Beep to signal to open door
    6. Beep when temp has dropped to 50C
    Great information here - I'll definitely reference it when I start working on my own!


    Constantin

    Quote Originally Posted by Constantin View Post
    See here for some pics and a description. Probably cost about $150 in materials and works.

    I hear the $285 eBay jobs require modifications to work well.
    I had found some in that ballpark when I was looking as well - thanks!


    WMXZ

    Quote Originally Posted by WMXZ View Post
    Efficient 'printer' to bring solder paste onto boards is very useful.
    Thanks for bringing this to my attention. Most of the boards I'm doing are for personal use, so stencils should be fine for now but I'll keep this in mind.

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    I'm also interested in doing this in the near future.

    This sounds like it might be the oven potatotron used:
    http://www.amazon.com/Hamilton-Beach...dp/B008J8MLHA/

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    Senior Member joe_prince's Avatar
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    Quote Originally Posted by linuxgeek View Post
    This sounds like it might be the oven potatotron used:
    http://www.amazon.com/Hamilton-Beach...dp/B008J8MLHA/
    I saw that model as well, but I didn't see the convection fans potatotron was mentioning. It might be an older model that isn't around anymore since it was back in 2012.

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    Quote Originally Posted by joe_prince
    Thanks for bringing this to my attention. Most of the boards I'm doing are for personal use, so stencils should be fine for now but I'll keep this in mind.
    the device ('printer') I'm using is a heavier (stable) plate where you can position a stencil in place by means of two magnets, but in such a way that you can flip the stencil away without smearing the solder mask. I used this for putting solder paste on multiple but identical boards. So the term printer is really a misnamed term, but that is what they call it.

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    Senior Member joe_prince's Avatar
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    Quote Originally Posted by WMXZ View Post
    the device ('printer') I'm using is a heavier (stable) plate where you can position a stencil in place by means of two magnets, but in such a way that you can flip the stencil away without smearing the solder mask. I used this for putting solder paste on multiple but identical boards. So the term printer is really a misnamed term, but that is what they call it.
    Ah, I see. Pardon my lack of knowledge with it. That's actually quite neat!

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    Senior Member Constantin's Avatar
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    There is a kickstarter right now for a PCB printing machine... i.e. put in some bare FRP and then the traces are printed, along with balls of extra solder for device connections. The whole enchilada is then heated from below and voila... finished PCB. If I were to do this again, I would look into redoing the control scheme, i.e. heat primarily from below with short bursts from above for only the critical reflow phase. But I don't have time and the current system works well enough. Also, wonder if the quartz tubes can handle a triac vs. being current limited by using a SCR.

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    Quote Originally Posted by joe_prince View Post
    I saw that model as well, but I didn't see the convection fans potatotron was mentioning. It might be an older model that isn't around anymore since it was back in 2012.
    I see one review complaining that the convection fan stopped working, so I think it does.

    I'm guessing it's behind that grill on the lower right.

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    Senior Member joe_prince's Avatar
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    Quote Originally Posted by Constantin View Post
    There is a kickstarter right now for a PCB printing machine... i.e. put in some bare FRP and then the traces are printed, along with balls of extra solder for device connections. The whole enchilada is then heated from below and voila... finished PCB. If I were to do this again, I would look into redoing the control scheme, i.e. heat primarily from below with short bursts from above for only the critical reflow phase. But I don't have time and the current system works well enough. Also, wonder if the quartz tubes can handle a triac vs. being current limited by using a SCR.
    Is this the one you're referencing Constantin? https://www.kickstarter.com/projects...ds-in-minutes?

    Quote Originally Posted by linuxgeek View Post
    I see one review complaining that the convection fan stopped working, so I think it does.

    I'm guessing it's behind that grill on the lower right.
    Good call - it very well may be the same one then!

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    Senior Member Constantin's Avatar
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    No, it's not prometheus. The fab I'm aware of prints solder paste directly onto FRP vs. milling a copper layer off. OK, found it... it's the voltera, see it on Hackaday. This is not an endorsement, BTW! I have no idea if it works. For example, the prometheus can handle some very tiny spacings/pads, etc. It's unlikely the Voltera can...

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    Senior Member joe_prince's Avatar
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    Quote Originally Posted by Constantin View Post
    No, it's not prometheus. The fab I'm aware of prints solder paste directly onto FRP vs. milling a copper layer off. OK, found it... it's the voltera, see it on Hackaday. This is not an endorsement, BTW! I have no idea if it works. For example, the prometheus can handle some very tiny spacings/pads, etc. It's unlikely the Voltera can...
    That's right, I remembering seeing it when they had the campaign. The tolerances/widths don't seem to be as good as the Prometheus like you mentioned, but it's neat that it's an all-in-one station.

    Would have been cool if they had another vacuum/suction attachment to do some pick and place along with the milling and solder paste dispensing....

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    I just read through that SparkFun post (good stuff there) and had a few questions about the oven itself. For the burners in the oven, do I need top and bottom burners?
    My understanding is yes it's better to have top and bottom elements, because you get more even heating.

    I didn't see many ovens with the fans you're talking about...do you feel that heat distribution would be uniform enough without the fan?
    Fans = "convection oven" sorry for not being clear on that. When I was doing research it seemed most people recommended this (including that Stack Overflow link) for more even heating.

    And for the thermocouple, are you using type K as well?
    I am using a K-type. Specifically, this one https://www.adafruit.com/products/270 with this this amp https://www.adafruit.com/product/269

    Was thinking about possibly having multiple thermocouples and averaging their values to get a better idea of the heat distribution.
    That's probably a good idea. What I do is touch the tip of the thermocouple to the center of the PCB but I like your plan.


    This is the toaster oven I bought back in 2011/2012: https://www.hamiltonbeach.com/toaste...er-31809c.html Like I said there's nothing special about it, at the time it was the cheapest one that was in stock and had top + bottom elements + convection.

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    Thanks again potatotron! After further researching it seemed that the only different between a conventional and a convection toaster oven is having the fan to distribute the air. It sounds like that's the best way to go for uniform heat in terms of the reflow oven and the reflow profile.

    I was looking at those 2 products from Adafruit last night, so nice to hear that they're working well for your application. As far as the actual oven goes, it seems like there is a wide variety and the lower priced ones are actually quite simple which is good for retrofitting (i.e., no rotisserie, nothing digital just manual knobs, etc.).

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    When I started making these a few years ago I did not want another project, I wanted a low cost functioning solution with "some assembly required"

    I purchased the Arduino Reflow Oven Controller Shield and paired it with this Panasoic IR Toaster oven.
    The first PCB worked turned out perfectly - much to my surprise - and many thereafter. I don't usually "cook" more than 4 of these Arduino shields or other boards of similar size at once to avoid inconsistent results due to different temperatures in different parts of the oven.

    There are certainly more turnkey style solutions available today.

    I actually charted out the reflow curve. The problem with many of these solutions is not necessarily the heating, but the cooling. In order to follow the recommended cooling profile I have to open the door of my toaster oven right after the reflow process is completed. Only then it cools down fast enough. The proper cooling BTW is easily as important as the proper soak and reflow time/curve because it is then when the solder metal(s) re-crystallize. Sounds complicated, but the solution - opening the door - was easy ;-)
    Last edited by Headroom; 12-09-2015 at 10:05 PM.

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    Senior Member joe_prince's Avatar
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    Quote Originally Posted by Headroom View Post
    When I started making these a few years ago I did not want another project, I wanted a low cost functioning solution with "some assembly required"
    That's really neat!

    I purchased the Arduino Reflow Oven Controller Shield and paired it with this Panasoic IR Toaster oven.
    I saw that some others used IR ovens as well, instead of a conventional or convection. How does the IR compare to them? Are the IR toaster ovens harder to "hack" than the conventional ones with regular heating elements?

    I actually charted out the reflow curve. The problem with many of these solutions is not necessarily the heating, but the cooling. In order to follow the recommended cooling profile I have to open the door of my toaster oven right after the reflow process is completed. Only then it cools down fast enough. The proper cooling BTW is easily as important as the proper soak and reflow time/curve because it is then when the solder metal(s) re-crystallize. Sounds complicated, but the solution - opening the door - was easy ;-)
    Haha nice! You have to open the door either way to get the boards out, so no worries if you open it a little sooner than you would need to anyway

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    Senior Member Constantin's Avatar
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    My oven was a $30 black and decker special from Amazon. Two quartz Tubes below, two above. I modded the living daylights out of that thing. I especially recommend reducing the thermal mass of the thing by adding high-temp insulation inside the cavity. That makes it much easier for the control system to actually run the whole process in the 3 minutes it is supposed to.

    (DO NOT even think about using house fiberglass!!! The stuff will go exothermic around 475*F since they use sugar as a binder)

    The Dual SCR doesn't get very warm thanks to the massive heat sink I fitted the thing with. If I had to do this again, I'd put the lower elements on one SCR, the upper ones on the other. Then re-write the Arduino code to reflect the desired curve, with the heavy lifting being done from below and only the occasional flash from above.

    As for cooling, this is something I want to address in a future iteration of my oven. Opening the door (and there are cams out there to do that for you) certainly helps but you want to be cautious initially until the solder has solidified. A member over at Arduino forums mentioned that cooling ceramic capacitors too quickly leads to naughty failures, i.e. invisible cracks that randomnly cause issues.

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    Quote Originally Posted by Headroom View Post
    I purchased the Arduino Reflow Oven Controller Shield and paired it with this Panasoic IR Toaster oven.
    LOL, that's my toaster oven, and luckily it has a touchy power switch. I guess it's time for a replacement and move this one to the workbench.

    Does it work well enough without a fan for convection?

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    Senior Member joe_prince's Avatar
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    Constantin

    Quote Originally Posted by Constantin View Post
    My oven was a $30 black and decker special from Amazon. Two quartz Tubes below, two above. I modded the living daylights out of that thing. I especially recommend reducing the thermal mass of the thing by adding high-temp insulation inside the cavity. That makes it much easier for the control system to actually run the whole process in the 3 minutes it is supposed to.

    (DO NOT even think about using house fiberglass!!! The stuff will go exothermic around 475*F since they use sugar as a binder)

    The Dual SCR doesn't get very warm thanks to the massive heat sink I fitted the thing with. If I had to do this again, I'd put the lower elements on one SCR, the upper ones on the other. Then re-write the Arduino code to reflect the desired curve, with the heavy lifting being done from below and only the occasional flash from above.

    As for cooling, this is something I want to address in a future iteration of my oven. Opening the door (and there are cams out there to do that for you) certainly helps but you want to be cautious initially until the solder has solidified. A member over at Arduino forums mentioned that cooling ceramic capacitors too quickly leads to naughty failures, i.e. invisible cracks that randomnly cause issues.
    This sounds awesome. Do you have any pictures of yours with all the mods? Would love to see it...

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    Senior Member Constantin's Avatar
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    The Arduino Forum Link I provided above has a pretty detailed description. Here it is again in case you missed it: http://forum.arduino.cc/index.php?topic=115163.0

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    The github link to the code that you modestly modfied in that Arduino foum page comes up empty. Would you be interested in sharing that ?
    It woud be really helpful.

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    I'm curious as to how one of these might perform for reflow operations.....
    http://www.appliancesdirect.co.uk/p/...s7VBoCdPjw_wcB

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    Senior Member Constantin's Avatar
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    Sure thing, it's attached.

    The Kester solder paste is pretty amazing, very happy with it. Some day I will try to rewire my oven and redo this control system. But first, I need to organize the basement so it no longer looks like an earthquake hit.
    Attached Files Attached Files

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