Hot Air Station?

Discussion in 'Electronics & Electrics' started by RussellK, Jun 17, 2019.

  1. RussellK

    RussellK Member

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    What are people using for hot air rework?

    I'm looking at making up a little board that'll have a 48 pin QFN chip, and am facing up to the reality that a soldering iron ain't going to do the job.

    There seem to be a heap of the 858D units floating around. Given they just have to blow hot air, I guess they don't need to be particularly complicated?
     
  2. Matthew kane

    Matthew kane Member

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    I use a Quick 861dw.
     
  3. _zak

    _zak Member

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    Does the IC have an exposed pad? If not, I've done components using a fine tip, lots of flux, and desoldering braid to clean up.. If it does have the pad, hotplate reflow (with an op-shop fry pan) might be an option.

    I've looked at the various 858D clones, and have always ended up deciding that I don't trust them quite enough to have on my workbench. Apparently the Yihua ones are the 'originals' and generally reliable, but I'm saving for the Quick 861DW that Matthew kane has :)
     
  4. dakiller

    dakiller (Oscillating & Impeding)

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    This is what I got at work, it aint too bad - https://au.element14.com/tenma/ss-952bc-f/rework-station-500w-110v-220v/dp/2311402

    Otherwise I would take the opinion of Rossmann on the matter (Quick 861) - https://rossmanngroup.com/buy-hot-air-station-laptop-cellphone-repair/

    I got a Hakko 851 clone at home. It is really old and the diaphragm pump cracked around where the screws all clamp it together not long ago and it stopped blowing. I repaired it by cable tying it all back together. I'll be in the market for a new machine when that repair gives out.
     
  5. bYrd

    bYrd Member

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    I'm using a Yihua 853D (the 3A bench PSU one), my second after the first hot air element kept burning out. The replacement has been great, no issues at all
     
  6. merlin13

    merlin13 Member

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    +1 to hand soldering with a normal hot stick, of you've got the right attitude and skill set. And you're working on chips with exposed pins of course... :)

    Else I bought a Yum Cha one just like this quite a few years ago now, cheap 'n cheerful. Apart from the irregular abuse I give it hammered the hell out of it whilst doing some contract electronics work for a company (that had literally been building SMT board product for years and no hot air station anywhere in the building... long story) and it's been fine.

    Only thing I did do is order a spare hot air element at the same time from the same crowd - extra, but having had those die even in name-brand units found it was a pain to twiddle thumbs or use the hot stick for soldering until the replacement element lobbed in. That and the fun finding a compatible replacement as well at 4 pm on a Friday...

    Oh, off topic but as an aside - also have an old (!) Hakko desoldering station that needed a new diaphragm, part for that aren't manufactured any more.

    So rather than forking out near $100 for a piece of high-temp silicon sheet thin enough (minimum order of from anywhere here in Oz at the time...), found the bottom of a silicon pie plate made a great substitute to Frankenstein up a few. Gave that a hammering over the years as well and haven't killed the first one yet.
     
    Last edited: Jun 18, 2019
  7. OP
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    RussellK

    RussellK Member

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    The part in question is this little 7x7mm bundle of fun:
    http://www.ichaus.de/upload/pdf/TW8_datasheet_D1en.pdf

    It kinda looks like there's the sides of the pads exposed around the edges, so a good, honest iron may do the job, but on the other hand, I should have moved to SMT years ago, and it's probably time I tooled up. Replacing parts using an iron is doable, but a pain.

    The Quick 861dw looks nice, particularly with the Rossmann tick of approval, and I've been trying to go with the "buy once, cry once" philosophy (hence I finally coughed up for an 87V a few years ago) but often find myself reaching for the cheap tool that does the job well enough. Another alternative is the current Tenma offering from Farnell:
    https://au.element14.com/tenma/21-10130-uk-eu/rework-station-900w-220v-uk-eu/dp/206263302

    I see the Tenma stuff all over their site - I'm guessing it's their house yum-cha brand, but given it's Farnell, you'd imagine it wouldn't be total junk?
     
  8. dakiller

    dakiller (Oscillating & Impeding)

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    You need a hot air for that one, also some good skills to go with. QFN is a fickle one, especially the bigger one.

    You’re getting a pro made board for this and not something diy?

    Tenma is element14’s yumcha brand, I got the one I linked in my first post and it isn’t junk.
     
  9. OP
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    RussellK

    RussellK Member

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    That's the other can of worms I'm going to have to reluctantly open. Up to this point, my boards have been one-offs, some maybe 4 or 5. I run them out on a CNC router that also takes care of the drilling. I can have a board done in around 30 minutes.

    For this bad boy, a proper board with solder mask and all that is probably required. I hear they're damn cheap, which I think I'll need, as I rarely nail the ideal board layout first try.
     
  10. mtma

    mtma Member

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    Have to agree, hot air and paste is going to reduce the headaches considerably even if it's just a one off.

    Also to traditional hand solder the QFN (even without the die attach pad) you need to choose a special PCB pattern as the radii of the iron tips are a problem unless you've got real fine or sharp chisel tips.

    As for using the hot air stations, I assist the process with a hot pad, (actually a printer heat bed that I'm not using on a printer) and employing a preheat cycle is extremely helpful to achieving a positive solder/desolder response. You can hit the preheat soak with a big air gun if necessary then do the shooting with the station.
     
  11. dakiller

    dakiller (Oscillating & Impeding)

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    Jlcpcb is stupidly cheap for custom boards. It’s only a question of express post or slow post and how much you are willing to fork out to get them quickly
     
  12. OP
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    RussellK

    RussellK Member

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    Damn Jlcpcb is crazy cheap. I've been drifting along with Eagle, but I get the impression that Kicad is the go these days, hopefully being not the hot mess it was when I last looked at it...
     
  13. merlin13

    merlin13 Member

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    Funny, the crowd I mentioned earlier ended up buying near half-dozen of those Tenma machines when they saw that they really needed hot air stations. Weren't a bad toy for the coin.

    So add my +1 if you want to drop that ammount of coin on a reasonably serious box.

    Beta/pre-production and actual production run boards, definitely agree.

    But as a one-off or an Alpha prototype, that depends on the Tools 'n Talent. Not a job for the faint-hearted hand soldering SMT though when they either pick the wrong pads or change component specs after the board has been laid out, but still do-able with the right attitude.

    Solder paste does a pretty good job of transferring heat to the pins then wicking up between them 'n the pads, even if/when the iron tip isn't fine enough to get right down to the contact point 'tween each pin 'n pad.
    But you need enough flux to stop the paste from then bridging the pins when the surface tension of the solder kicks in. Home-rolled/one-off boards need good tinning on the pads as well.

    Using stock solder (even the real skinny sub-0.5 mm stuff), that can be daunting on the wrong layout. And stay away from Lead Free as well.
     
  14. _zak

    _zak Member

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    With that exposed pad, I'd say you're definitely looking at hot air or reflow. In my experience the side pads are relatively easy using flux and paste, but getting the iron underneath the chip is tricky!

    I learnt to design PCBs with KiCad and while I'm just an amateur, have laid out a number of pretty simple boards. If you don't mind spending a little more, OSH Park accept KiCad and Eagle files directly, which is pretty cool. They have the added bonus of ENIG finish, but I hope you like purple!

    Just to offer a contrary view, I've moved entirely to lead-free and while I initially found it trickier, I don't have any issue with it these days (generally I use Sn 99.3/Cu 0.7 at 300°C). Part of that is having a better iron, but re-learning proper technique and how to use flux helped a lot.
     
  15. dakiller

    dakiller (Oscillating & Impeding)

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    I was an avid Eagle user for over a decade, but I made the switch to KiCad last year and it has been great. There is some initial pain learning the basic commands again, kicad is all about the keyboard shortcuts to anything, and getting your head around their not so intuitive library system, but after that, the laying out is much nicer than eagle
     
  16. merlin13

    merlin13 Member

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    Off topic, but...

    Trickier? Oh hell yes for the Uninitiated. One-off home-rolled boards, far easier to use leaded solder. Particularly on the wrong sized pads using the "wrong" tools.

    Most "experienced" workshop teckos I've worked with would easily butcher boards and burn out iron tips on a regular at that temp. I'd also be reviewing component spec sheets on heating times right up there as well.
     
  17. OP
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    RussellK

    RussellK Member

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    And then there's this one:


    Yum-cha as all hell, but actually looks pretty impressive.
     
  18. merlin13

    merlin13 Member

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    Jesus - 1200 watts?? Strip bits out of an air fryer, did they? Mind you, with the air flow cranked right out they might need that much heat.

    Bit curious on the maximum air flow if you blow parts off the board above 10%. Yum Cha indeed... I want one though.
     
  19. mtma

    mtma Member

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    Would be useful to...

    Precisely burn a loctited bolt ? :lol:
     
  20. merlin13

    merlin13 Member

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    was thinking more getting that nice crispy crust on chicken or a nice lump of pork...
     

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