Reflow main board techniques

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  • grimacelord
    Badcaps Veteran
    • Jan 2017
    • 362
    • USA

    #1

    Reflow main board techniques

    Hey guys. I have a TV that I am troubleshooting in another thread that leads me to believe reflowing the main processor may fix my problem. Problem is, I've never reflowed a TV main board before. I have successfully reflowed dozens and dozens of laptops, game consoles, etc. using a hot air rework station with bottom preheater. I am assuming the process is the same as I have developed a sort of standard technique over the years that is 90% successful on laptops and game consoles. I wanted to share my technique and see if it's suited for a TV main board.

    1. Remove main board and clean off any thermal paste, stickers, adhesive residue, etc.
    2. Place board on bottom preheater set to 150C for roughly 15 min or until a top temperature probe placed directly on the chips die reads 100C
    3. Apply generous high quality no clean flux such as amtech under the chip.
    4. Using a proper sized BGA nozzle for your chip, set the hot air roughly 1/4" above the IC and set to 150C. I use max air flow speed for my station, but others might need less.
    5. Apply 150C of hot air for 1 minute.
    6. Increase hot air temp to 200C after one minute and run for 30 seconds.
    7. Increase hot air temp to 225C after 30 seconds and continue for an additional 30 seconds.
    8. Ensure the top temp probe reads between 223-235C and remains in that range for roughly 10 seconds during the last 30 second flow time.
    9. Turn off hot air and preheater and allow to air cool until temp probe reads 60C or less.
    10. Clean off excess solder for appearance if that is important to you or just out of habit.
    11. Apply high quality thermal paste
    12. Apply a copper shim suited for your application on top of the chip that you just out thermal paste on then apply more paste on top of the copper shim and then install heatsink.
    13. Hope it worked.

    This works beautifully for me with computers and game console boards so, should I be ok with this technique on a TV main board?
  • trunks81
    Badcaps Veteran
    • May 2020
    • 265
    • Nederland

    #2
    Re: Reflow main board techniques

    Which station are you using ? This profile should work !

    Comment

    • diif
      Badcaps Legend
      • Feb 2014
      • 6978
      • England

      #3
      Re: Reflow main board techniques

      I have a rework machine, I use the same profile for reflowing everything, perhaps adjusting if the PCB is a bit thicker than usual.

      10. I think that should read remove excess flux not solder ? Which you should do as flux can be corrosive

      12. Why add a copper shim? the heatsink sticks straight onto the processors.

      Comment

      • grimacelord
        Badcaps Veteran
        • Jan 2017
        • 362
        • USA

        #4
        Re: Reflow main board techniques

        Originally posted by diif
        I have a rework machine, I use the same profile for reflowing everything, perhaps adjusting if the PCB is a bit thicker than usual.

        10. I think that should read remove excess flux not solder ? Which you should do as flux can be corrosive

        Yeah, I usually do clean up the excessive flux but there are some "no clean" flux types out there that claim it's non corrosive and ok to leave on. I usually don't anyway just out of habit of always cleaning it, but supposedly you can leave it if using one of these.

        12. Why add a copper shim? the heatsink sticks straight onto the processors.
        I've found, at least in the case of laptops (especially HP), that the heatsink alone isn't always sufficient to adequately cool the chip after it's already failed once and been reflowed.

        I started using copper shims originally on HP AMD GPU failures and stopped getting them returned after a few weeks or months. So now, I use them just about everywhere. You have to be careful that you don't add a shim too thick or you'll cause more problems.

        I buy packs of shims of varying thickness and use whichever is appropriate for the board I am working with. Has been working nicely for me so far, so I figure I'll keep doing it

        Comment

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