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    #41
    Re: Advice for a new BGA rework station owner please

    Hi guys
    I'm still managing to break stuff

    I decided to remove a north bridge from an ASUS P5P43TD motherboard today

    This one https://www.badcaps.net/forum/showthread.php?t=79353

    One thing I found out last week is I have to get quite a bit of heat into ATX motherboards for quite some time to remove large components (such as CPU sockets) My temperature probe right next to the chip has to get up to a good 260C-270C for 20-30 seconds (which requires an upper and lower nozzle temperature up to 285C for the last 15 seconds) or they don't come off. 230-240C on the PCB temp probe (260-265C final nozzle temperature) just doesn't seem to do it even though you would think the solder should have melted already.

    So I used a hotter profile I created for LGA sockets and I cleanly removed the north bridge first time.

    But examining it under the microscope before cleaning I could see that two pads right on one corner of the BGA had come off the PCB (and they were still stuck to the BGA)

    I decided to clean the chip and the PCB anyway (for practice) and that went well with no further pads lifted. Following previous advice from here I was using my T12 with BC3 tip at the slightly lower temp of 320C and small 1-2cm strips of braid cut from the reel this time. I also warmed the area of PCB (and the BGA) with my hot air station first as well.

    I also noticed after cleaning that two pads on the PCB right next to the two lifted ones were dull plain matt grey. I scratched them very lightly with a needle point and the grey whatever-it-was rubbed off leaving shiny pads

    So two pads lifted from the PCB in one corner, all others (and all pads on the BGA) were good = not quite a success LoL

    I know I need to post some pics, I'll grab some tomorrow or on Monday.

    I'm not sure if the problem was too much heat during removal of the BGA, or if there was a problem with some sort of corrosion/damage on those pads anyway (bear in mind the motherboard did not work)

    Also can I ask - are you folks using any flux during BGA removal?

    I'm not using any but I do have some Topnik liquid flux I could possibly get to run under the edges of the BGA before removal. Maybe that is my problem?
    Last edited by dicky96; 02-14-2020, 12:23 PM.
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      #42
      Re: Advice for a new BGA rework station owner please

      Perhaps more/longer bottom heat. Yes use flux, it will stop oxidization and aid removal.

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        #43
        Re: Advice for a new BGA rework station owner please

        For this profile I have the bottom IR heater at 220C and the bottom air at same temp as the top air

        The bottom air nozzle is considerably larger than the BGA and top air nozzle is a bit larger than the BGA. it's the largest top nozzle I have.

        Here is some pics of what went wrong this time. I cant' see any tracks going to the two missing pads so I guess they were on an internal layer

        I will try running some liquid flux under the next large BGA I try to desolder. This motherboard wasn't worth much anyway even if I fixed it, so no big loss (other than I would like to have seen whether the north bridge was actually causing the fault).

        Still, I'm sure I will get a nice bag full of useful MOSFETS and other parts off this board before it goes in the trash

        I must get a memory card for my microscope camera instead of taking pics of the monitor screen on my mobile phone lol
        Attached Files
        Last edited by dicky96; 02-15-2020, 09:09 AM.
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          #44
          Re: Advice for a new BGA rework station owner please

          The two lifted pads were clearly attached to the relevant balls on the BGA before I cleaned it.

          I think I have another one of those dull matt grey pads I was trying to describe earlier (see pic)


          'I also noticed after cleaning that two pads on the PCB right next to the two lifted ones were dull plain matt grey. I scratched them very lightly with a needle point and the grey whatever-it-was rubbed off leaving shiny pads'


          What causes those?
          Attached Files
          Last edited by dicky96; 02-15-2020, 11:27 AM.
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            #45
            Re: Advice for a new BGA rework station owner please

            The pads that lifted are most likely No Connection (NC). They are more susceptible to lifting when heated compared to those with tracks. Nothing to worry about (If they are NC ofcourse).

            The dull grey could be corrosion. I recently pulled a BGA from a TV motherboard which was water damaged and 80% of the pads were dull grey (got them to shine again after some scratching with a needle).

            Liquid flux (in my opinion) is good for reflow. If you are removing BGA, use flux paste as they provide longer working time compared to liquid flux.

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              #46
              Re: Advice for a new BGA rework station owner please

              Originally posted by dicky96 View Post
              One thing I found out last week is I have to get quite a bit of heat into ATX motherboards for quite some time to remove large components (such as CPU sockets) My temperature probe right next to the chip has to get up to a good 260C-270C for 20-30 seconds (which requires an upper and lower nozzle temperature up to 285C for the last 15 seconds) or they don't come off. 230-240C on the PCB temp probe (260-265C final nozzle temperature) just doesn't seem to do it even though you would think the solder should have melted already.
              Try checking the calibration of your temperature probes.

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                #47
                Re: Advice for a new BGA rework station owner please

                I already did that spider when I first got this machine. Well not exactly calibrated as I don't have any known temperature reference but I used two probes on different meters to compare the results and they were pretty much the same - I uploaded a couple of videos.

                I will do some more next week
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                  #48
                  Re: Advice for a new BGA rework station owner please

                  I decided to remove the South Bridge from the ASUS P5P45TD that I wrecked last week trying to remove the North Bridge

                  I used a lower temperature profile and it came off without damage to the BGA or motherboard. This was removed without flux.

                  I've posted some pics of the profile during soak phase and just at the moment the profile completed

                  Here are a couple of videos of the inspection before clean up https://youtu.be/p1byis97dcU

                  And afterwards https://youtu.be/C9g-5P1YD88

                  Sorry there is no audio on these - I'm trying some new recording software on my PC rather than using my phone and I need to get a microphone.

                  I'm not sure I am cleaning the PCB to the standard required for reballing and replacing the BGA. Please could you advise on that?

                  Also if you watch the video through (please.... I know i isn't very exciting) you will see some of those dull grey pads I was talking about on the BGA and PCB which I have to scrape to clean them up. It's like some sort of oxide that rejects flux. Anyone know what that is and why?

                  In the video of the BGA before cleanup you can see the balls look different in the corners than they do in the center area. Why is that and is it of any relevance to the lifted pads I had on one forner of the North bridge which looked similar before clean up?

                  I had already salvaged a load of capacitors from the board as you may notice in the pics, I'll get the MOSFETS off it as well before I sling it
                  Attached Files
                  Last edited by dicky96; 02-17-2020, 07:19 AM.
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                    #49
                    Re: Advice for a new BGA rework station owner please

                    The texture of the solder looks like the texture solder has when its in the 'paste' phase right before it turns liquid(which I doubt would be the case here).

                    The next most plausible thing is oxidation. Without flux and with heat, oxidation occurs at a much faster rate. Try using flux on your next BGA removal and compare new results with old.

                    With oxidation, solder won't adhere to the pads even if you use flux. At this point, the oxide layer needs to be removed before soldering/reballing.

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                      #50
                      Re: Advice for a new BGA rework station owner please

                      Now that is an interesting theory Mr Spider - because, if I remember my A level chemistry correctly, oxidation only occurs on the surface of a metal exposed to the atmosphere (or at least to Oxygen or an oxidising agent)...especially when heated. So if that is oxidation I am scraping off the surface of the BGA and the PCB then would that mean those balls were fractured to start off with, therefore allowing air to get to the surfaces of the fracture, before I started heating them?

                      If so then was that the fault to start off with? Broken balls, so to speak...
                      Last edited by dicky96; 02-17-2020, 04:35 PM.
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                        #51
                        Re: Advice for a new BGA rework station owner please

                        Or it occurred when you removed the chip because there was no flux.

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                          #52
                          Re: Advice for a new BGA rework station owner please

                          Originally posted by dicky96 View Post
                          So if that is oxidation I am scraping off the surface of the BGA and the PCB then would that mean those balls were fractured to start off with, therefore allowing air to get to the surfaces of the fracture, before I started heating them?

                          If so then was that the fault to start off with? Broken balls, so to speak...
                          No, there's quality assurance and all that good stuff for a reason!(Otherwise that would be very bad to say the least, though I would suspect the probability of it happening is not 0). It most likely happened during the desoldering process especially if no flux was used.

                          https://www.pcb-repair.com/resources...es-or-defects/
                          Last edited by Spider1211; 02-17-2020, 05:04 PM.

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                            #53
                            Re: Advice for a new BGA rework station owner please

                            OK I tried again on another scrap board - I removed the North Bridge and this time I used Topnik TK83 liquid flux which I ran under the BGA as best as I could

                            This time the profile I used to remove the South Bridge form an ASUS board yesterday did not work. It looks like it gets hot enough on the graph but it does not remove the chip and I can't move it with a pair of tweezers either.

                            I tried twice and the same thing happened. To be honest I don't think I have managed to remove a North Bridge or a CPU LGA Socket with this profile though South Bridge seems to come off fine

                            I used the hotter profile I created and that worked first time despite the temperature probe (cyan line) actualy reading lower than the previous profile!! This profile always worked so far

                            The chip came off much cleaner with flux, none of those dull grey pads, but I still managed to remove a few pads from the PCB :-(

                            Video here
                            https://youtu.be/JoTIw5pNZyQ

                            I'm finding this quite frustrating now and I am not sure what I am doing wrong.

                            I uploaded pics.
                            Settings and graph for first profile (didn't work)
                            Pic of PCB
                            Settings and graph for second profile (did work)
                            Attached Files
                            Last edited by dicky96; 02-18-2020, 12:07 PM. Reason: speeling
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                              #54
                              Re: Advice for a new BGA rework station owner please

                              The difference between the two profiles is..
                              slightly higher temperatures from stage 3 onwards
                              5 seconds longer on stage 6
                              IR heater plate goes up to 220C instead of 200C

                              I'm not sure if the pads came off when the BGA was removed, I thought I couldn't see them stuck to the BGA balls like previously, or when I cleaned the flux off the PCB with a brush (similar to toothbrush) and Isopropyl.

                              However looking closely at my own video I think the pads are stuck to the balls. There are some gold looking bits on the side of some balls in the corner nearest to pin 1 and one that looks the same in the opposite corner and they appear to correspond to the missing pads on the PCB. It's like they have slid half way round the ball on the BGA. I need to look again with my microscope tomorrow to double check that.

                              I let the PCB cool down and applied more flux under the BGA between each attempt.
                              Last edited by dicky96; 02-18-2020, 12:24 PM. Reason: more info
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                                #55
                                Re: Advice for a new BGA rework station owner please

                                The chip came off much cleaner with flux, none of those dull grey pads
                                Glad to hear the positive results!

                                but I still managed to remove a few pads from the PCB
                                Let's start fresh;

                                Here is a few things I would try:
                                1. Ensure any edge bonding is fully removed - Sometime some remains stuck under the chip.

                                2. Use a secondary independent temperature temperature probe right next the BGA machine probes on your next trial just to ensure the readings are being reported correctly to the machine (I know you said you already checked calibration, but lets recheck anyway). Try also putting a temperature probe on the bottom side of the board right at the center of the chip.

                                3. Ensure the upper nozzle effectively surrounds the chip and overlapping the latter by atleast a few millimeters on each edge

                                4. Use plenty of flux (try different types if possible - paste and/or liquid) - I have had good results with the 559 (clone most likely). The only 'issue' I have with it is its a bit of a pain to clean since its tacky and dries thick.

                                5. Try a manual lift. - When the BGA reaches melting temperature, do not pick it up straight away. Poke it with something on two edges like you are trying to move it up/down & right/left (use a screwdriver or something of the like) to ensure the chip is freely moving and you don't feel any excess resistance.


                                From a previous post: I'm not sure I am cleaning the PCB to the standard required for reballing and replacing the BGA. Please could you advise on that?
                                It should be smooth to touch. Use a piece of lint free wipes (such as kimwipes) or swabs as listed by diif. If it pull fibers or you feel it catching, you have some rough spots. Add flux, (fresh solder is also a good idea) and wick again. This applies to both chip (before reballing) and PCB.

                                When cleaning, its best to use the same type of solder as the solder balls you plan to use. For example, if you plan on using leaded solder balls; clean the old solder, 'flush' residual old solder with leaded solder and wick

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                                  #56
                                  Re: Advice for a new BGA rework station owner please

                                  Other than that, I think the BGA reflow profile should be modified.

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                                    #57
                                    Re: Advice for a new BGA rework station owner please

                                    Hi guys
                                    I've come back to this after several days working on 'paying jobs'

                                    Looking at spider's list

                                    1. These chips have no edge bonding that I can see
                                    2. I've tried this - more later
                                    3. Yes it does. I have various size top nozzles with the machine
                                    4. Yes I'm trying flux
                                    5. Didn't try this


                                    OK so I did the tests as per suggestion 2 using the built in probe and two standalone temperature meters. I tried on a south bridge using my lower temp profile. I have no problem removing south bridge on the last few attempts. I took some video and pics ready to upload... but then I tried a different combination on a north bridge.

                                    Previously I had found I can't remove north bridge or LGA CPU socket unless I use an even hotter profile. The hotter profile works in as much as it does desolder the component but always ends up lifting pads from the PCB towards the corners or on one edge

                                    This happened even when I used liquid flux under BGA before desoldering - the chip would come off with the pads looking 'cleaner' but I was still lifting pads on the PCB

                                    Then I decided to use my lower temp 'south bridge' profile with flux on a north bridge - and it worked! In fact I have done three on the run now and they all came off cleanly at the lower temp when I used flux. And no pads were lited from the PCB

                                    So by a lot of trial and error I seem to have found a combination that is working for me, at least so far.

                                    I will post some pics of the profile I am using tomorrow and also try again with the two even cooler profiles that came pre-programmed on the G720 with the addition of flux. Previously they would remove QFP128 /QFP256 and similar but not BGA

                                    I'm using a Topnik liquid flux at the moment. It comes with a little brush built into the bottle lid and I find that repeatedly dipping the brush then trying to get it under the edge of the BGA on all four sides while holding the PCB vertically seems to work well.

                                    I've also become quite expert in making a large ball of solder on my T12 BC3 tip and getting it to roll around the BGA and PCB to clean off the old solder without actually contacting with my soldering iron

                                    Rich
                                    Last edited by dicky96; 02-26-2020, 01:33 PM.
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                                      #58
                                      Re: Advice for a new BGA rework station owner please

                                      After yesterday's successes I did some more work on the BGA machine today

                                      I tried removing a LGA1151 socket using the same profile that was happily desoldering North and South Bridge chips yesterday on a different board

                                      I used Topnik liquid flux again and put the plastic pin shield (borrowed from the replacement part) on to the LGA socket (1st pic) - otherwise how was the machine vacuum going to pick it up?

                                      This time it didn't work. The profile (Lead Free 3) is the 2nd attached pic and the actual temperature graph is the 3rd pic. As you can see the temp probe next to the LGA got up to 224.9C but that wasn't enough and it did not desolder.

                                      I let it all cool down to room temperature and then applied fresh flux and tried again with the hotter profile (Lead Free LGA). You will see this profile goes up 15C higher than the previous one but on the temperature graph the probe went up and extra 10 degrees to 235.5C. This time it worked (pics 4&5)

                                      The lift was clean and all the pads on the PCB survived intact (pics 6&7)

                                      So now I need to solder the replacement socket - and this will be the first time i have tried soldering a BGA

                                      So more questions
                                      How do I know if the replacement is socket Lead or Lead free? (pics 8&9)

                                      Do I apply flux to the PCB and BGA?

                                      If I use the vacuum to pick up the LGA (so it need the plastic cover on) and optical alignment to position it then I probably need to apply flux to just the PCB after I aligned the socket - otherwise I am not sure if I will be able to see the pads on the PCB and LGA if there is flux all over them

                                      Do I just use the same profile that removed the old LGA socket?

                                      Anything else I should beware of?

                                      Wish me luck!

                                      Rich
                                      Attached Files
                                      Last edited by dicky96; 02-27-2020, 01:05 PM.
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                                        #59
                                        Re: Advice for a new BGA rework station owner please

                                        How do I know if the replacement is socket Lead or Lead free?
                                        1. Look at the texture. Lead free is dull while leaded will have some shine to it
                                        2. If the possibility it there, take an iron to it. Set the iron to around 185-187C. Leaded should melt or atleast will start to look like its 'crumbling' while lead free should be 'scarred' by it. Keep the iron on the solder for no more that 2-4seconds.
                                        3. Look at the ball/solder under microscope at high magnification. Lead free solder has a more pronounced 'crystal like' texture compared to leaded solder.
                                        4. Ask the seller if you bought it online.

                                        Do I apply flux to the PCB and BGA?
                                        Apply a thin film of flux paste on the pcb using a soft brush (for more or less uniform distribution)

                                        If I use the vacuum to pick up the LGA (so it need the plastic cover on)
                                        You could also use kapton tape instead of the plastic cover. If you do not have a wide enough tape, use strips with overlapping edges then stick a piece of Aluminium tape (cut in a square shape) at the center of the kapton tape.

                                        When doing BGA reworks, ensure a fairly constant environment around the machine. Even a light breeze could affect the profile.
                                        Last edited by Spider1211; 02-27-2020, 02:25 PM.

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                                          #60
                                          Re: Advice for a new BGA rework station owner please

                                          I've also become quite expert in making a large ball of solder on my T12 BC3 tip and getting it to roll around the BGA and PCB to clean off the old solder without actually contacting with my soldering iron
                                          That's how it should be done to avoid lifting pads. Using something like the T12-BCM2 or T12-BCM3 helps a lot. The hollow center on these tips help 'hold' the solder.

                                          These tip are also great for soldering QFP since the hollow center acts like a little 'greedy reservoir'
                                          Last edited by Spider1211; 02-27-2020, 02:37 PM.

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