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Hobbyist Techniques for Reflow?

Discussion in 'General Electronics Discussion' started by chopnhack, May 27, 2014.

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  1. chopnhack

    chopnhack

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    Apr 28, 2014
    What are your techniques? With the continuing push for smaller, fewer products will be available in hand solderable packages. As a hobbyist, how are you contending with the issue? I have seen reflow done on youtube in a toaster oven! Has anyone tried using a heat gun?
     
  2. OLIVE2222

    OLIVE2222

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    Oct 2, 2011
    I have seen solder plate method videos and its look pretty good. I have personally used the paste (via a dispenser) and a dedicated oven. Results are correct but I still prefer the plain old solder iron method up to 0402 size + desoldering braid and flux for fine pitchs IC. I apply a simple rule, if I can't perform a visual inspection of the result (solder pad under IC, BGA,...) I go for professionally made assy. No doing so involve more soldering debug issue than design debug issue.
    Olivier
     
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  3. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    I limit my hand soldering to 0603 or larger.

    On small devices I use solder paste unless I'm replacing a component -- In that case it's often easier to tack it in place with whatever solder is on the pads.

    0.65mm pitch is the narrowest I'll do willingly, but I've done 0.5mm pitch by hand. The hardest part is really getting things aligned.

    I have a rework tool as well, and although I can do a lot of stuff with an iron, there are times when hot air is just a lot better.

    Oh, it also helps to be an octopus.
     
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  4. chopnhack

    chopnhack

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    Wow! 0402 is small... I found a video showing someone hand soldering an IC - my first thought when watching was that too much heat was pumped into the IC - can anyone comment as to whether this is a good technique to learn from? I am going to find some scrap boards and start practicing if it is.
     
  5. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Yeah, I'd probably do it a little quicker. Also, you may not have the luxury of being able to hold the device down with your fingers. That's a pretty big chip.
     
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  6. chopnhack

    chopnhack

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    Apr 28, 2014
    Maybe do opposite leads to tack in place?
     
  7. BobK

    BobK

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    Jan 5, 2010
    I have not tried reflow yet. I've soldered 0603 and SOT using paste and then just touching each side with tip of the iron. I've soldered 44 pin SSOP using drag method (tack two corners, then drag a blob of solder across all the pins on one side, making a mess, and clean up with desoldering braid). That method is actually faster than soldering the individual pins on a PDIP. I concur with Steve that getting the large chips aligned is hard part.

    If you go to Sparkfun, they have an interesting method of doing reflow with an electric skillet that I think I will try if I ever need it.

    Bob
     
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  8. chopnhack

    chopnhack

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    Apr 28, 2014
    I tried my hand at removing some SMD's today. It is apparent to me that my crappy iron is not up to the task - simply doesn't put out enough heat! All the videos I see, it just takes a touch, while my iron has to sit on the component for quite some time before the solder flows. I did pre tin my tip and use a flux pen ;-) I attached a pic of some of the pieces I pulled off a scrap board. Luckily I was able to find two soic-8 chip that are the exact size of my next project to practice with :)

    Can anyone recommend a good soldering iron?

    [​IMG]
     
  9. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    It is quite possible that the boards you're trying to desolder parts from are using unleaded solder which melts at a somewhat higher temperature.

    If the board has large areas of copper, this may also make life hard for you.
     
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  10. BobK

    BobK

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    Did you use a solder sucker or copper braid? It is very hard to remove parts with just a soldering iron.

    Bob
     
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  11. chopnhack

    chopnhack

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    Apr 28, 2014
    Copper braid, I don't know whether it was the old solder or the iron itself. I fluxed the terminals just prior to applying the braid and heating the terminal, some posts would go liquid quickly, most did not. The smd's came off fairly easy - I actually had more trouble with the through hole parts, some were soldered top and bottom? I don't know if that was just excess passing through the hole or something else.

    Aside from a good iron, (which I still could use your recommendations on) is there a particular flux that is better? I have seen some being used in videos that was much more viscous, seemed like it worked better.
     
  12. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    For surface mount devices there's often nothing else to do other than to melt all the solder and lift the device off while it's still molten. This is where hot air really comes into its own.

    The removal of through hole components is almost always exactly opposite. You remove all the solder and let the device fall out. To highlight this difference, sucking is often the best approach.
     
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