Having issues with Reball process

Discussion in 'General Electronics Chat' started by btwitche, Oct 6, 2010.

  1. btwitche

    Thread Starter New Member

    Oct 6, 2010
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    Basically, I thought it was going to be easier to reball than it is.

    I watched Youtube videos and did online resaerch on the process and Everything looked/sound easy.

    I bought a 1200 dollar infrared system with heating bed that hooks up to my laptop and the stencils and the balls and the flux and random other things i found i needed.

    But now i am 2k down and have not been able to do a single viable reball.

    I understand that I need to not heat the chip above 230 celcius
    I understand that i should have bought direct heating stencils.
    I am using flux that is no clean and tacky.
    I have .60mm balls that are 63/37 lead based.
    My system is programable.
    I can get the chips off and reball them and align them but so far i am 5 for 5 with none alive. 3 systems were working before the reball and now they are not finishing start up.
    I am shielding the other chips on the board.
    The BGA's I am fixing are just under 2inchs square.

    Any information would be very helpful.

    Thank you
    Branden
     
  2. retched

    AAC Fanatic!

    Dec 5, 2009
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    230C seems awful high. What is the time at temperature before damage is incurred?

    P.S. - Doesn't re-balling suck?
     
  3. btwitche

    Thread Starter New Member

    Oct 6, 2010
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    230 is melting point for lead free solder.

    I am thinking about using solder paste instead of the balls

    As for the reballing sucking as of yet yes very much.

    No one seems to know much about it and all reference material is either using 50,000 dollar equipment or so guy with a heat gun that just switchs out a working system so he does not look bad on your tube.

    I am here to get any extra help possible

    Thank you
    Branden
     
  4. DonQ

    Active Member

    May 6, 2009
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    11
    But you also said:
    Seems like contradictory info. You did say "to not heat the chip above 230 celcius", but just wanted to check that you weren't just getting too hot for the solder you were using.
     
  5. retched

    AAC Fanatic!

    Dec 5, 2009
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    One would thing the lead solder should melt at a lower temp then lead-free.

    If the ship is not happy above lead-free-melting-temps, then the leaded temp (lower) should keep it in a good range.

    IR is tough.. Is IR and leaded solder a good combination?

    Apparently, the IR systems for leaded and lead-free use different wave-lengths.

    It may be that you solder is not getting past the "gummy" stage and not electrically bonding to the pads.
     
  6. marshallf3

    Well-Known Member

    Jul 26, 2010
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  7. eblc1388

    Senior Member

    Nov 28, 2008
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    Someone commented in another forum that the heat must not be directed to the center of the BGA chip as it will definitely kill the die situated there.

    Heat the chip like that shown in arrow directions.

    [​IMG]
     
  8. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    I cannot reball but I have fixed HP laps tht needed the graphic chip set reheating.
    As elb said I always heat around never direct on to the die. Besides 230 is too much as I think.

    Preheating is necessary too
     
    Last edited: Nov 2, 2010
  9. marshallf3

    Well-Known Member

    Jul 26, 2010
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    Buy some of the VERY low melting point solder that ChipQuick sells.
     
  10. Wendy

    Moderator

    Mar 24, 2008
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    The processes I worked on used some fancy optics along with hot nitrogen, and lead tin solder.
     
  11. btwitche

    Thread Starter New Member

    Oct 6, 2010
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    Sorry let me better explain the process.

    I need the 235 degrees celcius to heat the lead free solder that originally connected the chip to the board.

    Lead free melts at 217 but there is a heat sink on top that I have to get thru and I am heating the bottom of the board at 200 with a preheating cycle. After chip removal I will be puting leaded balls that melt at 185 but they are under the chip so the melting temp is about 205-208. TESTED every temp from 50 degrees colder. If i was using direct heating sorce then i could melt the leaded at 185 easy, but the heat sink is a problem.

    I will try heating around the center of the chip, DO YOU think a small alluminum heat sink placed right in the center will help with that 20 degree temperature difference.

    Also the poping of chips I believe is cause by the Chip collecting moisture I have desided to bake the boards at 80 degree celicius for 6 -10 hours to negate this occurance. ALSO i have discovered that using Methyl Ethyl Keatones on the chips will help draw out the moisture from them.

    I have perfected the chip removal without pad damage on either side.
    I have perfected the reballing process with perfect spherical balls.
    I believe my temp setting are perfect for the device I have and my temps for the device are with in their safe range as per 3 thermal couples.

    One last issue I think I am getting warping of the board litterly not precievible until i go to place my chip back on. (.5mm)

    I purchased a mount made for the device but it hs not come yet.
    so i made one out of aluminum using my band saw and drill. I have not yet tested the difference it makes.

    Thank you all for your information. Also please ask questions they make me think about things I would not have and help me think outside the box.

    THANK YOU
     
  12. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    I can understand your pain.

    The people wrapping a towel around the XBox360's with the RROD to "resolder" the CPU/GPU IC's properly are extremely lucky, I guess.

    Are you using tin-lead solder on the same spot that lead free solder was removed? They don't stick to each other very willingly.

    All I can say is I know BGA sucks for the people attaching them, but are very useful to make compact items.
     
  13. btwitche

    Thread Starter New Member

    Oct 6, 2010
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    OKAY I have figured evrything out but one thing.

    I originally thought that my issue derived from a floppy warped motherboard and now i have the best of the best support built for my board.

    AND found out that the damn BGA is the one acting up. It is getting warped by the natural process of being heated.

    I noticed a long time ago that there where resistor/diode on all 4 corners on some models and that the seemed to serve no function. I am guessing that they were line up marks at the time. But now i think they were being used as spacers so the bga could not flatten out on one side or the other.

    Some models just have 2 resistor/diodes and other have none.

    When i was using a board with the resistors present on all 4 sides I did not have this sexy mount so i think my issue was board warpage derived.

    Any ideas on what to do here???

    Thank you
     
  14. retched

    AAC Fanatic!

    Dec 5, 2009
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    Are you slowly cooling the board when done the process?

    If you are cooling too quickly, warping is a big problem..for the IC and the PCB.

    Slow pre-heating and post-cooling is key to this horrible headache called ball soldering.
     
  15. btwitche

    Thread Starter New Member

    Oct 6, 2010
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    0
    No i have been doing a quick cool.

    I get conflicting info on this point.

    solder need to heat fast and cool fast and in essence i am doing that.

    I do not understand why the soldering process is different that the ball array senerio.

    I will try anything and thats what ill try this time. thank you be back in an hour
     
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