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iphone 6 - oxidation on meson pads?

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  • iphone 6 - oxidation on meson pads?

    Hello,
    I have a very simple question : I am on an iphone 6 whose screen does not respond.
    I removed Meson, but before putting a new one, could you tell me what you think about the pads : is this yellow/orange color meaning oxidation?
    I don't manage to put any tin on these pads (they are mainly on the bottom left on the photos). For the other pads it's ok.
    Thanks a lot for your advices!


  • #2
    Actually flat grey is the cracks when solder ball separated from the pads. You will need to gently rub the pads with soldering tip wet with bit of solder and flux to get solder wetted on the pad properly, then prepare the pads so they are all uniform pillows or desoldered before putting meson back on, No peaks on pads.

    I just redid a Meson plus cumulus just in case for warranty job with extra jumper on M1 and original jumper on D10 or E10 (this one with very thin trace from a pad to a via on a 6. Not the 6 plus.

    Cheers, Jason

    Comment


    • #3
      Ok thanks.
      I am french so I try to understand properly what you said: what you call “flat grey” is what I call yellow/orange? I made a red circle on the photo to be sure. Is it correct?
      When you rub it with the soldering tip I think there a risk to pull it off? So I will have to do it gently.

      The jumpers that you have put were on an iPhone 6 motherboard or on an iPhone 6 plus motherboard?
      I know that it’s a frequent repair on 6 plus but I didn’t know it was sometimes needed on a 6.
      Why did you decide to do this? After testing with a multimeter, or because the tracks looked cracked?

      Thanks.

      Comment


      • #4
        Ok I understand what happens with my pads : they are not connected pads.
        So no matter if there is tin or not.

        Comment


        • #5
          Ooohh I understand now,

          The ones that shows tan/brown circles where pads used to be is called pulled pads, The ones without connections is not important (not connected), ones that had connected pads ripped off leaving stem (the bit of copper in the center of the pad and other pads that does have tracks leading off to somewhere has to be reconnected with gentle scraping clean the track down to copper with fine point knife, install wire jumpers using solder and flux.

          Solder on the good pads has to be quality (pillows) or cleaned off leaving flat pads, No solder peaks as they tend to be badly oxidized and also causes overheating of IC trying to heat pads' solder to remelt due to excessive spacing. To fix this, warm board on the heater and use solder iron with little solder, and flux to wipe pads leaving all very beautiful low domes (pillows). Cannot do this with extra hot soldering iron as this glue binder decomposes (you can smell difference between heated flux and burnt board by testing with too hot iron on scrap boards) on the circuit board results in loose pads. Reason for need to have board heater is the answer because circuit boards acts like heat sink wicking away localized heat (soldering iron and hot air rework), causing solder peaks and solder bridges and roasted IC due to excessive heat or too long.

          I'm doing this soldering work for decades and knows this, also had been working on consumer electronics repair full time before and now recently started repairing cell phones. Difference of quality soldering is no different between normal size and microscopic size.

          Cheers, TVtechcellphone
          Last edited by TVtechcellphone; 04-25-2019, 09:32 PM.

          Comment


          • #6
            Thanks a lot for your advices!
            Fortunately there seems to be no pulled pads on my board.
            No I have cleaned all the pads with solder wick.
            So I just need to wait for a new meson chip and I hope it will be ok

            May I ask you 2 other simple questions:
            - how do you manage to make tin stay on the solder iron? In my case the tin stays on the tin wire, and makes a ball growing more and more. That’s really irritating!
            - which kind of cotton swab do you use to clean PCB? Do you use medical cotton swab? In my case they tear off, leaving lot of cotton.

            Thanks a lot ;-)

            Comment


            • #7
              Q-tips or decent ear swabs with good body of tips. Watch for fibres and just get any off with tweezer and keep gathering the fibres as you go cleaning till clean, then use fresh flux again before soldering.

              You need soldering tip cleaner paste, wipe the soldering on this lightly dampened yellow foam (made for this purpose, not the kitchen scrubbing block of foam!) and brass wool. This will make tip more solder wettable and leave solder on the tip between uses.
              Hakko, Quick and last choice chinese soldering stations. preferably with thermal temp adjustable soldering station, The cheap soldering irons does not have sturdy tip also anything hotter than 600F will corrode fast making you to clean tip often.

              Starting out in repair business?, This requires investment in quality tools to start with and much easier to do.

              Cheers, TVtechcellphone
              Last edited by TVtechcellphone; 04-27-2019, 05:52 PM.

              Comment


              • #8
                The yellow/orange spots are pulled pads. They are missing. The pads came off with the chip. Do not attempt to put solder on missing pads! If you are lucky the missing pads are all NC—not connected. If this is true, leave them alone and carry on.

                oxidized pads are dull grey like an elephant ear. Good pads are shiny and bright.

                Comment


                • #9
                  Most people use standard household cotton swabs. Use more alcohol when cleaning to thin the flux and decrease shedding/fibers

                  Comment


                  • #10
                    Thanks for all these useful advices.

                    Now I have a professional soldering station, so I hope that the use of soldering tip cleaner paste will solve my problem.

                    For the missing pads on my board, they all seem to be NC pads so I hope it will be ok.

                    Comment


                    • #11
                      Hello,

                      I’ve tried with 3 new meson chips and I didn’t succeed for a strange reason.




                      I made all the pads completely clear, by using solder wick.

                      Then I’ve put some flux.

                      With hot air the meson chip was soldered, it was perfectly in the right place (I have another iPhone 6 board to compare). But it stayed a little bit higher than it’s neighbour chip.

                      The 3 times it was impossible to make the meson chip go down “to the floor”.

                      And in fact a lot of pads were ok but some pads were not properly connected (OL in diode test on some capacitors instead of 0,5V on my other board).




                      I really don’t understand what’s happening. The PCB is perfectly clear, no mountain on it, no more tin.




                      I’ve tried to put very hot air (380 degrees) but no change.




                      Is it possible that the tin doesn’t melt when it’s on pulled pads, and make it impossible for the chip to go down?




                      Or another explanation: is it possible that the flux stays like a prisoner under the chip, and doesn’t manage to go away to the sides of the chip?




                      Thanks

                      Comment


                      • #12
                        IC Sitting higher means 2 issues: Not good enough hot air station, the Chinese knock offs is the the problem, either you roast the board or not able to solder well I cuss at that thing badly before we invested in Quick hot station. And the pads is not prepared properly as I have mentioned before. Ditto to soldering station too!

                        This means NO peaks on the pads (cones, mountain, or too tall domes, or few pads has too much solder. Needs to be all consistent solder on all pads, two choices: desoldering would be nice but more dangerous due to more chances of disturbing other components around this area, Or use board heater and less hotter soldering iron carefully wipe pads with little amount of solder on the tip and flux applied to the board, Or bit more hotter tip to do the same without board heater, but my experience shows that more chance of burning the board with too hot tip leading to more pads looser, undesirable situation.

                        Also sometimes you have to heat the pads with flux and hot air station to reform the solder on the pads properly, watch the solder melt and don't stay around too long otherwise other side and around it with parts's solder might melt again and break connections. Building experience helps here with junk boards and develop your favorite procedures, how hot air is and how hot soldering tip that works best for you, how you hold the tool to direct the gives best work results.

                        Cheers, TVtechcellphone
                        Last edited by TVtechcellphone; 04-30-2019, 05:45 PM.

                        Comment


                        • #13
                          1.) Does this phone still boot? If not, then troubleshoot that.

                          2.) What made you decide to replace meson to begin with? What is the history of the device and problem?

                          3.) Chip not sitting at same height---that may be normal or may not be. Not all chips sit at the same height.

                          4.) "I made all pads completely clear" In my opinion that is not a good idea. The chip is not meant to go on blank pads. I do not braid pads on iPhones--it causes problems and solves none. I prefer to solder a new chip on top of tinned pads or "puffy pillows" like small candies. This means the new chip will sit unevenly on top of the pads at the start of the process--good! Then I can see it shift into place by itself with the hot air. This shift is my visual cue that all the balls are liquid. If I don't see a significant shift, then I will give the chip an "imperceptible nudge" to be sure that everything was liquid under the chip. I can NOT push down on the chip, or guide it in any way once I begin to apply hot air. Only the power of surface tension and cohesion must pull the chip to its final spot--not me.

                          5.) Do you have no touch at all? Or partial touch with dead lines? If none at all, then let's go back to the beginning of your diagnosis. Have you confirmed power to the touch chips with a voltage test with screen connected?

                          Comment


                          • #14
                            Another way to confirm that newly soldered IC is level, not tilted, is look at how the reflections of many chips' top reflects as you tilt the board. If reflections they moves the same as the soldered IC, I'd call this good one.

                            Cheers, TVtechcellphone

                            Comment


                            • #15
                              Hello,
                              Thanks for your advices.
                              I’ve read everything and checked everything again.
                              My problem was indeed the excessive quantity of flux I was putting on the PCB.
                              This time I carefully cleaned the board with alcohol, and then put a little quantity of flux, put some hot air to spread it, and only after that put the Meson IC.

                              I also had to create a jumper for B10 which had disappeared.

                              And now it works!
                              I am so glad!
                              That’s the first time that a phone that I repair works better after the repair than before

                              There’s only one issue : there’s a thin vertical line which seems not to respond : the quality of the image is perfect but I’m not able to write letters that are in this line : I,k,n...

                              During the repair I have moved C2427. I have put it back to its place but I’m not sure about the quality of my soldering.
                              Do you think it can explain the not responding line?

                              Comment

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