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    DrMOS just won't desolder

    I've tried everything - my blower is at 480C on max speed (Yihua 995D) and this IC on the PALIT 980Ti just won't move.

    Any ideas on how to get it off? I believe the ground plane is just sinking the heat too quick.

    I've added loads of flux and I am trying to remove with tweezers whilst applying hot air directly on the DrMOS.

    #2
    Re: DrMOS just won't desolder

    Use a pre heater and perhaps upgrade to one of the 1000w stations, either the Quick or the Atten.

    Comment


      #3
      Re: DrMOS just won't desolder

      Originally posted by whc14765 View Post
      I've tried everything - my blower is at 480C on max speed (Yihua 995D) and this IC on the PALIT 980Ti just won't move.

      Any ideas on how to get it off? I believe the ground plane is just sinking the heat too quick.

      I've added loads of flux and I am trying to remove with tweezers whilst applying hot air directly on the DrMOS.
      If you do not need the chip, then just cut the legs off and deal with them individually.

      Comment


        #4
        Re: DrMOS just won't desolder

        Originally posted by keeney123 View Post
        If you do not need the chip, then just cut the legs off and deal with them individually.
        It's a QFN, the legs are flowing, it's the huge ground pad that is keeping it in place.

        Comment


          #5
          Re: DrMOS just won't desolder

          If it is shorted, most probably it has fused to the underlying pad, you can grind it off. too much heat or force can damage the underlying planes

          Comment


            #6
            Re: DrMOS just won't desolder

            Originally posted by whc14765 View Post
            I've tried everything - my blower is at 480C on max speed (Yihua 995D) and this IC on the PALIT 980Ti just won't move.

            Any ideas on how to get it off? I believe the ground plane is just sinking the heat too quick.

            I've added loads of flux and I am trying to remove with tweezers whilst applying hot air directly on the DrMOS.

            ok hiyua has bad temperature set....
            take a temp probe and cal the station
            normally u can desolve it using max 330 degres
            if u use high a have risk to damage component and the pcb

            use an hair dryer 1st to put the card warm bedore trying to desolve
            and use a 3rd hand to be sur than temperature is not absord by the surface in contact with the pcb...
            often more the card is small easier the desolvering is
            Last edited by klendatu; 04-06-2022, 11:52 PM.

            Comment


              #7
              Re: DrMOS just won't desolder

              Just get a decent hot air station.
              OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

              Comment


                #8
                Re: DrMOS just won't desolder

                I had same issue with cheap station, got a 2nd hand Quick 861DW from ebay and its the world of difference, definitely preheat the board also first.

                Comment


                  #9
                  Re: DrMOS just won't desolder

                  If it is near a choke line, these chokes are quite massive, and steel the heat from the pcb, you need time to desolder, sometimes several minutes before you can get off the device. Original tin is lead free, so flow temperature is higher then normal leaded tin (254C instead 224C). Use a bigger nozzle, do not use too much flux, it evaporates and steels the heat too. Use flux which is appropriate for non-leaded temperatures (can be used in higher temperatures).
                  Definitely preheat the board, set preheater even to 220-240C for unleaded tin, preheat at least some 5 minutes. Hotair you can set up to 440C, but heat also not too long, and keep some distance (min 1cm), move the nozzle from time to time also in circles to heat the area around. Heat only until the tin becomes fluid (you may use a temperature sensor attached to PCB and with some flux to monitor the real PCB temperature, it should not go over 270-280C).

                  If you have no success with this, then most probably the mosfet did have a massive short, and it did melt and is welded to the pcb copper. Then only solution is grinding and lot of time to do it very slowly and carefully to preserve the copper pads, do not use force. Such a "welded" pad must be tinned again. As it may have then changed it's consistence (no more pure copper, very hard and contaminated with the device metal) it may be very difficult to attach the tin to it. Then you may need to use some non-electronics aggressive flux to tin the pads before refitting a new device. If using such "non-noclean" flux, very good cleaning is necessary. However if you're lucky, and the demage is not too big, you can get also to a clean copper layer.
                  If you have bad luck, then the melt process did go inside the PCB, and you may have a short with the gound/heat dissipation plane. In such a case it's difficult, you may try to grind off the broken area and reconstruct it, but it is lot of fiddling, and may not be worth to do. Then transplanting the GPU and memories to another PCB, provided they are OK, would be a better option in my opinion.
                  Last edited by DynaxSC; 04-07-2022, 05:44 AM.

                  Comment


                    #10
                    Re: DrMOS just won't desolder

                    Originally posted by DynaxSC View Post
                    If it is near a choke line, these chokes are quite massive, and steel the heat from the pcb, you need time to desolder, sometimes several minutes before you can get off the device. Original tin is lead free, so flow temperature is higher then normal leaded tin (254C instead 224C). Use a bigger nozzle, do not use too much flux, it evaporates and steels the heat too. Use flux which is appropriate for non-leaded temperatures (can be used in higher temperatures).
                    Definitely preheat the board, set preheater even to 220-240C for unleaded tin, preheat at least some 5 minutes. Hotair you can set up to 440C, but heat also not too long, and keep some distance (min 1cm), move the nozzle from time to time also in circles to heat the area around. Heat only until the tin becomes fluid (you may use a temperature sensor attached to PCB and with some flux to monitor the real PCB temperature, it should not go over 270-280C).

                    If you have no success with this, then most probably the mosfet did have a massive short, and it did melt and is welded to the pcb copper. Then only solution is grinding and lot of time to do it very slowly and carefully to preserve the copper pads, do not use force. Such a "welded" pad must be tinned again. As it may have then changed it's consistence (no more pure copper, very hard and contaminated with the device metal) it may be very difficult to attach the tin to it. Then you may need to use some non-electronics aggressive flux to tin the pads before refitting a new device. If using such "non-noclean" flux, very good cleaning is necessary.
                    Will preheating the board to 220C not desolder the components from the back when I start applying hot air to the front? Also, will the plastic connectors for PCIE 6pin/8pin be safe at 220C?

                    Sorry, I've never used a preheater before, might have to buy one now. I see these 1600W IR ones for around 120GBP, if you have any expereicne with them?

                    Comment


                      #11
                      Re: DrMOS just won't desolder

                      Originally posted by benwaterson View Post
                      I had same issue with cheap station, got a 2nd hand Quick 861DW from ebay and its the world of difference, definitely preheat the board also first.
                      Is it worth getting a cheap preheater or instead spending the money on a better hot air station and use that hot air to "preheat" the board.

                      Comment


                        #12
                        Re: DrMOS just won't desolder

                        Originally posted by whc14765 View Post
                        Will preheating the board to 220C not desolder the components from the back when I start applying hot air to the front? Also, will the plastic connectors for PCIE 6pin/8pin be safe at 220C?

                        Sorry, I've never used a preheater before, might have to buy one now. I see these 1600W IR ones for around 120GBP, if you have any expereicne with them?
                        No, setting preheater to 220C does not mean, that the board will achieve that temperature, as it is heated from one side, and cooled from the other with room temperature, so the board will never achieve 220C, more something like 110-120 (the board material has a high heat conductivity and is comparably thin to the distance between the preheater and the board, usually ca 3 cm). Also the tin used melts at 254C, so even 220C will not make the tin fluid. Only in the area where you will use the hotair, there it can happen that the tin will become fluid also on the backside, but the components are usually not falling off, because they are held by the surface tension of the tin, many of them are also glued to the board in factory to allow the wave soldering process. So if you do not move/shake the board, and wait some time after the board did cool off, nothing should happen. So good fixing the board before the process is good idea. Also if there are a lot of small components around (on the side where you use the hot-air), I use to make pictures before applying hot-air, as too strong air flow can move the small components. In areas with high density of small comnponents it's better to set hotair to higher temperature, but the airflow low, eg 25-40% of max. Having a picture helps to recover the original placing. This is essential, if you do not have a boardview/schematics or a second board to compare.

                        The Atx power connectors, as well as the memory and PCI slots, or backside I/O connectors, USB connectors, etc. (black plastic) must be protected from the hot air. If the distance is some 5-6 cm from the hot air apply, they should withstand. Also the electrolytic caps must be mandatory protected (they can explode and hurt your eyes).
                        You can use for it captan tape, but in my opinion it's not very effective, you need to take 2-3 layers of it, if the distance is short (eg 1-2 cm), and its somewhat expensive. I use for it most of the times a Mc Guyver solution: a combination of a layer of Tetrapack material (paper + aluminium foil) combined with a layer of captan tape. The alu foil should be towards the heat source, captan tape on the alu side tetrapack material, in very narrow places (eg between the main ATX power socket and memory socket) I use even two tetrapak layers. It's much more insulating, but the tetra pack material (eg an empty milk container) is only for one time use, the paper inside is destroyed. Such a protection is essential everywhere you work near of the parts I listed before. Also assure good ventilation, as the flux fumes are not healthy - try not to inhalate them, a PC ventilator can help here to direct the fumes away, and does not cool the board too strong.
                        Last edited by DynaxSC; 04-07-2022, 08:11 AM.

                        Comment


                          #13
                          Re: DrMOS just won't desolder

                          Originally posted by DynaxSC View Post
                          No, setting preheater to 220C does not mean, that the board will achieve that temperature, as it is heated from one side, and cooled from the other with room temperature, so the board will never achieve 220C, more something like 110-120 (the board material has a high heat conductivity and is comparably thin to the distance between the preheater and the board, usually ca 3 cm). Also the tin used melts at 254C, so even 220C will not make the tin fluid. Only in the area where you will use the hotair, there it can happen that the tin will become fluid also on the backside, but the components are usually not falling off, because they are held by the surface tension of the tin, many of them are also glued to the board in factory to allow the wave soldering process. So if you do not move/shake the board, and wait some time after the board did cool off, nothing should happen. So good fixing the board before the process is good idea. Also if there are a lot of small components around (on the side where you use the hot-air), I use to make pictures before applying hot-air, as too strong air flow can move the small components. In areas with high density of small comnponents it's better to set hotair to higher temperature, but the airflow low, eg 25-40% of max. Having a picture helps to recover the original placing. This is essential, if you do not have a boardview/schematics or a second board to compare.

                          The Atx power connectors, as well as the memory and PCI slots, or backside I/O connectors, USB connectors, etc. (black plastic) must be protected from the hot air. If the distance is some 5-6 cm from the hot air apply, they should withstand. Also the electrolytic caps must be mandatory protected (they can explode and hurt your eyes).
                          You can use for it captan tape, but in my opinion it's not very effective, you need to take 2-3 layers of it, if the distance is short (eg 1-2 cm), and its somewhat expensive. I use for it most of the times a Mc Guyver solution: a combination of a layer of Tetrapack material (paper + aluminium foil) combined with a layer of captan tape. The alu foil should be towards the heat source, captan tape on the alu side tetrapack material, in very narrow places (eg between the main ATX power socket and memory socket) I use even two tetrapak layers. It's much more insulating, but the tetra pack material (eg an empty milk container) is only for one time use, the paper inside is destroyed. Such a protection is essential everywhere you work near of the parts I listed before. Also assure good ventilation, as the flux fumes are not healthy - try not to inhalate them, a PC ventilator can help here to direct the fumes away, and does not cool the board too strong.
                          Thanks for the detailed response. I have a feeling this DrMOS might be fused to the ground pad. It isn't showing a short but when I first opened the card, that DrMOS had 2 loose solder balls close to the edge of the IC. I assume it must have gotten extremely hot. But there's no shorts and coil Resistance is fine at 2.5ohms too.

                          Comment


                            #14
                            Re: DrMOS just won't desolder

                            Yes, there is no other explanation for these solder balls, I'm afraid.

                            Comment


                              #15
                              Re: DrMOS just won't desolder

                              Solder balls can be present out of the factory sometimes, doesn't necessarily means something has gone wrong.
                              OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

                              Comment


                                #16
                                Re: DrMOS just won't desolder

                                [QUOTE=whc14765;1123753]It's a QFN, the legs are flowing, it's the huge ground pad that is keeping it in place.[/QUOTE

                                Is it possible to take a Dremel and cut into the chip just behind the pins that the solder is flowing? Just have to be careful not to cut the board. If you had a vice that was adjustable you might lock the Dremel in the vice and then adjust it over and down to the chip. I think after it was cut about half-way through you might be able to bend the flowing pins up when heat is applied. Once you got that far you would be closer to the center pad. and could apply 40/60 flux solder directly to the center pad.
                                The other way would be to use the Dremel in the same adjustable vice and cut horizontal and vertical lines close together across the chip about half-way down into the chip and lift the little cut pieces with a pick. Once all pieces are lifted then try and heat the chip up again and see if it will come off.

                                If you knew someone that worked in a machine shop then you might be able to borrow an adjustable vice. Actually a milling machine with a small ceramic cutter would be perfect.

                                Also, there is a such thing that is low temperature solder which might flow better under the chip.

                                After reading what DynaxSC had to say I would try that first. I do not know about todays boards but the old ones took heat good. We had a technician that was heating up a chip with a old Master heat gun a few inches from the chip. He got in a discussion this someone while he was doing this and forgot what he was doing. There was a bunch of chips falling off the board before he realized what happen. The board was still good and the chips needed to be replace and reinstalled.
                                Last edited by keeney123; 04-07-2022, 10:23 PM.

                                Comment


                                  #17
                                  Re: DrMOS just won't desolder

                                  I have cheap solder station too... because i'm home user. What i do something like that? I have mechanic solder in a liquid form. I apply it with a needle and i start to heat. After both solder mix it can easly come out. Sorry for the english.

                                  Comment


                                    #18
                                    Re: DrMOS just won't desolder

                                    Originally posted by Guilty_2121 View Post
                                    I have cheap solder station too... because i'm home user. What i do something like that? I have mechanic solder in a liquid form. I apply it with a needle and i start to heat. After both solder mix it can easly come out. Sorry for the english.
                                    What Brand do you use? I see the brand name is Mechanic. Could you provide a picture of what you use. The internet sites do not know the difference between a paste and a liquid. They actually say a liquid paste?
                                    Last edited by keeney123; 04-10-2022, 05:34 PM.

                                    Comment


                                      #19
                                      Re: DrMOS just won't desolder

                                      Originally posted by DynaxSC View Post
                                      If it is near a choke line, these chokes are quite massive, and steel the heat from the pcb, you need time to desolder, sometimes several minutes before you can get off the device. Original tin is lead free, so flow temperature is higher then normal leaded tin (254C instead 224C). Use a bigger nozzle, do not use too much flux, it evaporates and steels the heat too. Use flux which is appropriate for non-leaded temperatures (can be used in higher temperatures).
                                      Definitely preheat the board, set preheater even to 220-240C for unleaded tin, preheat at least some 5 minutes. Hotair you can set up to 440C, but heat also not too long, and keep some distance (min 1cm), move the nozzle from time to time also in circles to heat the area around. Heat only until the tin becomes fluid (you may use a temperature sensor attached to PCB and with some flux to monitor the real PCB temperature, it should not go over 270-280C).

                                      If you have no success with this, then most probably the mosfet did have a massive short, and it did melt and is welded to the pcb copper. Then only solution is grinding and lot of time to do it very slowly and carefully to preserve the copper pads, do not use force. Such a "welded" pad must be tinned again. As it may have then changed it's consistence (no more pure copper, very hard and contaminated with the device metal) it may be very difficult to attach the tin to it. Then you may need to use some non-electronics aggressive flux to tin the pads before refitting a new device. If using such "non-noclean" flux, very good cleaning is necessary. However if you're lucky, and the demage is not too big, you can get also to a clean copper layer.
                                      If you have bad luck, then the melt process did go inside the PCB, and you may have a short with the gound/heat dissipation plane. In such a case it's difficult, you may try to grind off the broken area and reconstruct it, but it is lot of fiddling, and may not be worth to do. Then transplanting the GPU and memories to another PCB, provided they are OK, would be a better option in my opinion.
                                      Dude. Preheating is to 120c

                                      Comment


                                        #20
                                        Re: DrMOS just won't desolder

                                        Originally posted by whc14765 View Post
                                        I've tried everything - my blower is at 480C on max speed (Yihua 995D) and this IC on the PALIT 980Ti just won't move.

                                        Any ideas on how to get it off? I believe the ground plane is just sinking the heat too quick.

                                        I've added loads of flux and I am trying to remove with tweezers whilst applying hot air directly on the DrMOS.
                                        hiyua temp is mesured just at the end of the air gun noze... mean 100 degres difference outside the tip !!!!
                                        put a temp probe ull see

                                        do same as me... put a tip on air gun
                                        after put a temp probe to touch the deep of the tip
                                        cal to 480 degres with air flow at MAX..

                                        ull be able to desolder using about 395-370 degres
                                        Last edited by klendatu; 04-18-2022, 07:44 AM.

                                        Comment

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