SMD Work

Discussion in 'DIY' started by JP, Jul 7, 2018.

  1. JP

    JP 7480 74111110101115

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    I made up a few batches of my boards over the last couple days, and thought there may be some interest in how it's done.

    First up is the jig, which holds the board and the stencils. The boards are the size of a .6 wide DIP 28 package.

    IMG_1757.jpg

    IMG_1767.jpg

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    This is a closeup of the QFN 20 footprint, which is the PIC uC (6x magnification):

    IMG_1749.jpg

    And this is the alignment pin and stencil at 6x. It's a rather high-tolerance fit.

    IMG_1762.jpg

    This is the QFN 20 footprint with the stencil over the board:

    IMG_1770.jpg

    Next we lay down some solder paste and squeegee it over the board:

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    Close-up of the stencil with the paste applied:

    IMG_1783.jpg

    And a close-up of the board with the paste applied after removing the stencil:

    IMG_1788.jpg
     
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  2. JP

    JP 7480 74111110101115

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    Next we place the components (by hand, with tweezers):

    IMG_1790.jpg

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    Get ready for the hot air gun:

    IMG_1801.jpg

    And the completed work:

    IMG_1813.jpg

    IMG_1819.jpg

    For a little size reference, the tip in this picture is on my micro pencil - that's a 0.6mm wide chisel.

    IMG_1812.jpg
     
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  3. Judas Priest

    Judas Priest Super Member

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    Interesting!
     
  4. restorer-john

    restorer-john Addicted Member

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    I absolutely love the scope shots. What are you using?

    Hot air rework unfortunately is a reality for all of us now. I remember making a big speech saying that I'd give up before I went down the SMD path.

    Now I'm doing laptop motherboard component level repairs and about to purchase a new IR bed/ hot air unit. The hot air station has become my friend, although PbFree is still a bug bear.
     
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  5. s-petersen

    s-petersen Scott Subscriber

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    I had to replace this one in my Samsung TV (chroma chip) everything looked like comics.I used hot air to remove it, but standard soldering iron to install it.I think it was 48 pins
    chip.png
     
  6. JP

    JP 7480 74111110101115

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    Mantis Elite with my phone camera held up to the viewer. If I went traditional I'd probably go with a trinocular AmScope. Bummer Mantis' camera option isn't great.

    Laptop boards makes the 0603 stuff I'm using here gargantuan. IR pre-heater would be my next step, or a reflow oven.

    I use a generous helping of flux on those and drag solder with a knife tip. Not too bad with practice.
     
    Last edited: Jul 8, 2018

     

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  7. s-petersen

    s-petersen Scott Subscriber

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    I saw that on YouTube, and that's how I did it, with the iron. I was looking for a decent USB camera as a viewer, but didn't find one at the time, I wanted something that had a working distance of at least 3 or 4 inches.I still need to find one.
    How do you make the stencil?
     
    Last edited: Jul 8, 2018
  8. JP

    JP 7480 74111110101115

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    The latency on all but the purpose-built USB units range from bothersome to nearly impossible. I debated Mantis vs. Tagarno; far more Mantis on the secondary market. Anyway, low latency will be the key.

    Stencils are laser cut by dedicated shops, or board shops. Usually one and the same. The jig was made by a friend on his tabletop CNC. You can also get them done in kapton which is cheaper and quicker. I prefer proper stainless sheet for new work.
     
  9. ChrisMarantz

    ChrisMarantz AK Subscriber Subscriber

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    I use an Amscope 3.5X - 90X Trinocular Stereo Microscope - it's been some of the very best money I have spent for bench equipment. I haven't ever used a Mantis - I hear that they are the absolutely the best for board inspection. - Chris
     
  10. H/K crazy

    H/K crazy Active Member

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    I use a Pace PRC-2000 rework station and a Nikon microscope.
     
  11. slimecity

    slimecity Super Member

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    Oh wow - so thats how they do it - solder paste? Interesting.
     

     

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  12. Ray Gianelli

    Ray Gianelli AK Subscriber Subscriber

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    This is something I've been interested in lately. Like Restorer-John said it's a reality for us now.

    JP, where did you learn about this stuff? And what tools do you recommend?

    I started a thread about SMD work a few weeks ago. Any input anyone can give is greatly appreciated!
     
  13. rcs16

    rcs16 Super Member

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    Good job, well done with the jig for the stencil.
    I recall the first smt line when I worked at Motorola in the early 80's. They had both a ceramic substrate and a FR4 line running side by side.
    I have never had to use a stencil for my home smt work but it is nice to see it being used. It is definely faster and better if you are doing more than one pcb.
    Tools wise I have a Sparkfun hot air machine,tweezers and lots of magnification/light, a steady hand, some glow core no clean solder, a couple of irons for easy 2 terminal passives removal. A 10x jewelers loupe for inspection.
     
  14. JP

    JP 7480 74111110101115

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    @Ray Gianelli I'll write how I learned later when I've a bit more free time. The equipment list that was posted in your other thread is a really good start. I use a bit better equipment because I appreciate being able to work fast with little fuss, and when I do the boards above, I do 10-20 at a time.

    Soldering gear: Hakko FX-100 with standard and micro pencils, FR-410 desoldering gun, and FR-811 hot air rework.

    IMG_1826.jpg


    Because synthetic flux makes me (and pretty much anyone) ill, a Hakko FA-430 extractor.

    IMG_1828.jpg

    Mantis Elite microscope for working and inspection. For the size of work above I use a 4x objective for working and 6x for inspection. I've 8x and 10x as well.

    IMG_1827.jpg


    And for schematics and such a 49" 4K TV.

    IMG_1830.jpg
     
  15. petehall347

    petehall347 the brandy coffee man Subscriber

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    i have been trying to do smd more seriously lately and bought a decent station for it . cant get to grips with it yet as seems to be taking a long time with the hot air to remove things even at 400c . when soldering i am thinking the solder paste is no use anymore . it did seem ok used with my iron before trying hot air and more runny when tried with iron . now its thicker .
     
  16. ChrisMarantz

    ChrisMarantz AK Subscriber Subscriber

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    Are you adding flux before heating? I find that flux is necessary for quick component removal

    I use AMTECH NC-559-V2-TF - Chris
     

     

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  17. petehall347

    petehall347 the brandy coffee man Subscriber

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    tried with flux and got lots of smoke and ic chip still not budging . asked about this on another forum and was told to not use flux for de-soldering or i would get loads of smoke . plus it wont help . will watch some more videos .
     
  18. JP

    JP 7480 74111110101115

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    If the board is cold you're heating the part and the board when you use air, which is going to take some time. For me to remove a QFN-20 off my board from cold takes a couple minutes. Ground pours, etc. exacerbate.

    Here you can see what it takes from a cold board to a hot board as I go. Pre-heater is next for me.

     
  19. ChrisMarantz

    ChrisMarantz AK Subscriber Subscriber

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    Sounds like you have the wrong type of flux. Amtech will not smoke or burn away quickly at all - Chris
     
  20. petehall347

    petehall347 the brandy coffee man Subscriber

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    have been thinking i need to pre heat the board first .
     

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