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Trying my hand and BGA re-balling and I can't get the balls to stay put.

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    Trying my hand and BGA re-balling and I can't get the balls to stay put.

    So here is my story. I decided I wanted to play around with some BGA re-balling and bought myself a "BGA re-balling kit" that came with the following:
    • Re-balling station (the blue one with spring loaded base and black handles)
    • AMTECH RMA-223 flux
    • assorted stencils
    • assorted balls
    • solder wick
    • brushes
    • scraper
    • kapton tape


    I am trying to re-ball an ATMEL Cyclone III chip and I can't get the balls to stay put when heating with my hot air SMD wand (minimum air flow). My process is as follows:
    1. Mount BGA chip to re-balling station
    2. Clean old solder from the BGA chip.
    3. clean BGA chip with 99% isopropyl alcohol
    4. apply a small amount of RMA-223 to the chip and spread to a thin film
    5. mount 0.55mm stencil on re-balling station
    6. pour on 0.55 balls onto stencil
    7. once all stencil holes are filled pour out excess balls
    8. remove stencil
    9. apply heat to melt solder balls


    My problem starts when I pour the balls onto the stencil. The balls do not roll and flow like they do on demonstration videos I have seen on youtube. They seem to clump together and need quite a bit of force to make roll around, enough force to knock out the balls that are already sitting in the holes. Note that the stencil is clean. Once the holes are filled and I lift the stencil off the chip a good dozen balls are left holding onto the stencil holes. I replace the missing balls by hand. Once I begin to heat the chip most balls stay put and attach properly but three or four groups seem to static cling together once the flux begins to liquefy from the heat.

    I can't seem to get the process to work as smoothly as I see it done on YouTube. Anybody have any advice?

    #2
    Re: Trying my hand and BGA re-balling and I can't get the balls to stay put.

    a number of ideas here.
    first i would use an aerosol flux that dries not a paste.
    second, you usually melt the balls *before* you remove the stencil.

    but more importantly, are the balls actually round, and are they the right size?
    because they should not get stuck in the stencil.

    Comment


      #3
      Re: Trying my hand and BGA re-balling and I can't get the balls to stay put.

      Originally posted by stj View Post
      but more importantly, are the balls actually round, and are they the right size?
      because they should not get stuck in the stencil.
      What I meant by get stuck is that they seem to be sticking, as in adhesion or static cling.

      Comment


        #4
        Re: Trying my hand and BGA re-balling and I can't get the balls to stay put.

        well i doubt static, are the stencils clean?

        Comment


          #5
          Re: Trying my hand and BGA re-balling and I can't get the balls to stay put.

          The reballing kit you bought uses indirect heat stencils, they are the type that you remove before you apply heat. These can only be used with an IR station or a hot plate. Attempting to solder the balls with a hot air rework station will result in the balls sticking together because the airflow pushes them around. For reballing with a hot air rework station, you need direct heat stencils.

          But from what you say, the balls are sticking to the stencil before you even get to the heating process. Clean the stencils with IPA and a toothbrush and let them dry (or dry them using hot air) before you start working.
          Originally posted by PeteS in CA
          Remember that by the time consequences of a short-sighted decision are experienced, the idiot who made the bad decision may have already been promoted or moved on to a better job at another company.
          A working TV? How boring!

          Comment


            #6
            Re: Trying my hand and BGA re-balling and I can't get the balls to stay put.

            invest in a cheap ultrasonic cleaner if you can, they clean stencils much better than a toothbrush.

            Comment


              #7
              Re: Trying my hand and BGA re-balling and I can't get the balls to stay put.

              for me : AMTECH RMA-223 flux is that a fake?

              buy a good flux, put small quantity and clean with a credit card (similar to themto make u understand). put balls perfectly alligned.

              hot air set to 350-400° at 4-5cm distance. when ball start to melt u can put around 3-4cm distance. just make however soem practice.

              it ll be easy with 0.6 balls, harder when balls are smaller like 05 0.35 and so on.

              just princilal things are good flux, i use or 223 original or 559 tfp original for solder reball, remove the extra flux on bga and hot air temperature and distance.

              ps post a picture of your 223 to see if original or fake and useless
              Last edited by dellxps15; 10-23-2014, 07:57 AM.

              Comment


                #8
                Re: Trying my hand and BGA re-balling and I can't get the balls to stay put.

                Reballing takes a great deal of patience, attention to detail, and practice. As you practice/learn, you will develop methods that will make it easier for you.

                (I've made some assumptions in my reply/below).
                -- I assume that your solder balls/spheres are of good quality, NOT expired, and are NOT the issue. (Of course, it's entirely possible that you may need to try a different bottle/brand)
                -- I assume that you are using the proper size balls for your stencil and the package? If so, (and your stencil is clean, as you say) the spheres should fall freely into/thru the holes in your stencil)
                -- I assume that you have setup your stencil/holder/station properly? (You can have the stencil too close to (or too far away from) the chip.
                -- I assume that you are using Leaded (replacement) solder balls/spheres, and the proper heat for same?

                Pointers: (some have already been mentioned)

                Start out using SCRAP boards and or chips, and practice, Practice, PRACTICE !!!
                Keep your equipment (stencils) clean, Clean, CLEAN !!! (remove ALL flux between sessions (ultrasound is best, if you can afford it)

                Side note: Your stencil MUST be pristinely cleaned.. even alcohol can leave a film behind, and cause the balls to 'clump up' when you fill the stencil/holder with new spheres/try to roll them into place in their holes. If you don't have an ultrasound unit, you can follow up (after the alcohol) with a good detergent/water, a clean cloth, and your hot air wand (set just hot enough to remove the water)

                When you remove the old spheres/solder from the BGA, use enough flux on QUALITY BGA solder wick (not the thin/cheap stuff that you usually get in a "kit form" purchase. Chemtronics 60-BGA-5 works well). You can (I do) use a 'cheaper' flux for removal. I (many) use Kingbo, just MAKE SURE that you have proper ventilation !! (Kingbo is a 'fake' Chinese product, and NO ONE really knows for sure what is in it)

                Be sure not to get too aggressive and destroy the pads on the BGA when you remove the old spheres, but be sure to remove the solder down to the pads (NOT so far that you see copper!!!). You should be able to feel the pads afterwards, and not notice any 'humps' from leftover solder. The flatter the pads are, the less chance that the new solder spheres will migrate (the quantity and quality of your flux is also paramount here)

                Use the LEAST amount of (quality) flux for the new sphere attachement. There are MANY brands/types. Some that have received high accolades include: Amtech, Insat, Superior. A proven method involves using a thin film of Instat "Super Flux" (or Superior 99-2), which is liquid, applied in a thin film, allowed to dry to the touch, followed by a THIN film of paste flux (Amtech 559, LF-4300-TF, or even Kingbo (a topic in itself) and then placing the solder spheres on the BGA via a PROPERLY setup re-balling station/stencil (you want make sure that your stencil is not too close to the BGA/that you transfer flux to the stencil, or balls WILL stick to the stencil/in the holes of your stencil. If you can see flux on the bottom of your stencil when you remove it from the chip, it is too close (or you are using too much flux).
                Just keep in mind that too much flux on the BGA/Chip and the balls will float/move around when the flux becomes liquidus. (This is more pertinent as the spheres become smaller/lighter)

                After you remove the stencil, view the placement of the solder spheres (I use a lighted, bench mounted Magnifier, the type with an adjustable arm) to make certain that they are as centered on the pads as closely as possible before you start the attachment process. I often put the stencil back in place and move it in the direction needed to align all the spheres at once. You can even re-adjust your stencil in it's holder if necessary.

                Just as the proper profiling techniques are geared toward having 70%-80% of the heat applied to the bottom of the board/chip being reworked, using a hot plate (designed specifically for BGA rework, or one setup for precise control) can make the process easier, as the heat comes up from the bottom/thru the chip, as opposed to using a wand, whereby all the heat comes from the top (and the airflow becomes a factor for migration as well). You may find that this method is easier for you to master as you learn. There is NOTHING wrong with using hot air, it just requires a more deft touch, and it is very easy to cause migration from the airflow until you become experienced/familar with your equipment/capabilites.

                FORGET about the smaller chips/smaller balls UNTIL you have gained enough experience to master the art of reballing. The smaller the chip, the smaller/more closely spaced the pads/balls, the more difficult the process will be. (RAM Chips are a bitch!!)

                If you are using a handheld wand, consider buying or making some type of holder, at least until you streamline the process.

                Use COPIOUS (at Least 2.. or 3.. maybe 4) and QUALITY thermocouples (I ONLY use Omega/thin wire) and thermocouple meters (I also use Omega and/or FLuke, NO cheap/Harbor Freight stuff here!). After all, you are dealing with controlling heat (over time) as precisely as possible (and possibly airflow, depending upon your process) and there is a fine line between having too little (improperly attaching the spheres) or too much (destroying the package/BGA). The more precisely you are able monitor the heat/process, the easier it will be to control it properly.

                Oh, and did I mention.. practice, Practice, PRACTICE !!! ??

                Good luck.
                Last edited by WiseOldTroll; 10-23-2014, 03:38 PM.

                Comment


                  #9
                  Re: Trying my hand and BGA re-balling and I can't get the balls to stay put.

                  i would be wary of "insat" flux, it's more questionable than kingbo.

                  the guy at insat just buys it in and re-bottles it so nobody knows what it actualy is or where it comes from other than it is suspected of coming from israel.
                  HE DOES NOT SUPPLY THE CHEMICAL DATASHEET HE IS LEGALLY OBLIGED TO SUPPLY!!

                  Comment


                    #10
                    Re: Trying my hand and BGA re-balling and I can't get the balls to stay put.

                    In all probability, Insat is just rebottled Superior brand flux. (I know more about this than I can mention here). Superior has been around for ages and flux is all they do, so they are good at it, and if Insat is indeed rebottled Superior brand it is still a good product. The product itself has gotten positive reviews for many who use it/reball, hence the reason that I mentioned it. It IS pricey, and if one is based in the US, I would recommend Superior 99-2 as much as Insat, especially from a cost stand point. I DO NOT work for or represent either Superior or Insat, so I have no agenda to support either, I simply mentioned them in an effort to be helpful and make the point that a liquid type, tacky flux applied/allowed to dry before the application of the paste flux often leads to an easier attachment.
                    Last edited by WiseOldTroll; 10-23-2014, 04:19 PM.

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