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How do I remove the chip from the board

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    How do I remove the chip from the board

    I am new to hot air soldering. I need to remove one chip from the board. I have a hot air solder and I set the temperature to 350°C. I slowly started heating the chip, but the solder didn't melt. I heated it for about 5 minutes, but the solder still wouldn't melt. I increased the temperature to 450˚C and still nothing. After a while, the board started to change color, but the solder still didn't melt.
    Fortunately, I'm testing it on old network switches to see how it works.
    What am I doing wrong?
    I've seen a lot of videos on youtube and everyone got the solder melted and the chip was easy to remove from the board.

    #2
    i can't see it

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      #3
      I am attaching a photo. I have many devices that I can learn from 😊
      Attached Files

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        #4
        i would run some 60/40 leaded solder around the pins then get the hot air on it .
        and watch the other tiny things dont blow away like the 6 i can see right away . might be best to use kapton tape to mask them off .
        Last edited by petehall347; 10-08-2024, 12:22 PM.

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          #5
          Juist as a test : change the air flow to some lower quantity, and put a piece of solder on top of the chip. Then try dessoldering it, and watch for when the solder melts. Maybe your station is not producing air with the configured temperature.

          As a comparison : a chip like that is free here with the station at 450C in less than a minute.

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            #6
            The lead free solder has a higher melting point than the leaded solder. Put some leaded or low melt solder on the pins first then desolder the whole thing. You may have used a small nozzle, that would do it too. Take the small nozzle off and hold that hot air 1” above the chip.

            Holding the hot air for too long on the PCB will separate the PCB layers too and a bubble will form underneath.

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              #7
              After a while, the board started to change color, but the solder still didn't melt... it has melted long time ago regard to blowing arrounded components off. You probably use a small nozle, and trying to desolder big chip... take a nozzle out, and do narrow circle above chip legs in 1 Hz frequency. 350 is fine, but be sure that enough airflow is used. Do not lift chip before all pads are melted othervise you ended with ripped pads. Post photo with results and conclusion to motivate, encourige and help other who just start.

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                #8
                Everything went wrong for me. I used solder with a 38% pb content at home, but I still couldn't remove the chip from the board.
                I changed the tip of the hot air soldering iron from 4mm to 8mm. I set the air flow to the minimum.

                BTW, I removed the other smd components without problems.

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                  #9
                  Yes, I see... you choose wrong chip to practice with, on back side he have ground plate pad who is soldered on huge ground plane over whole pcb board and suck heat badly...
                  Attached Files

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                    #10
                    Originally posted by harp View Post
                    Yes, I see... you choose wrong chip to practice with, on back side he have ground plate pad who is soldered on huge ground plane over whole pcb board and suck heat badly...
                    agreed, that would do it. needs heat on both sides for this chip.

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                      #11
                      Ah, that's why I had problems. I chose the wrong learning chip. But I wonder if this chip can also be removed. Would heating from the other side of the plate help?

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                        #12
                        Yes, it can be desoldered. The proper way is to use bottom preheater arround 120-150 deg C and when board is set on desired temp attack from top side with hotair gun 300-350. When you practice, the goal is to build experiance regard to your equpment can do or cant do, and to do good desoldering with undamaged ic, pcb board and other surrounding parts and component. Do not fokus only to desolder ic... it is easy if you plan destroy everything else.

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                          #13
                          Either with a preheater or with another hot air gun. Just to take it off, there is another technique where you cut the legs from the IC off with an exacto knife, then you can drill into the middle of the IC and expose the metal it is heatsink end to on the bottom. Once you are there take a good soldering iron or a soldering gun and a bit of fresh solder and it will come right off like nobody's business.

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                            #14
                            I tried heating the Realtek chip on the switch from the other side of the PCB and it was removed nicely.

                            I found some chips on the old MB and it was much better (although I'm still not satisfied). I am adding a few photos
                            Attached Files

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                              #15
                              For a beginner, not too bad. I've seen much worse. A lot worse! Keep practicing! Also try small stuff. Maybe try cleaning and put chip back on, etc. Everyone has to start somewhere.

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                                #16
                                As you can see in the picture, I really need to replace this chip, but there are some SMD resistors and capacitors on the other side of the board. I'm afraid that when I heat the chip, the SMD components can be removed from the board. Is it necessary to secure the parts with some kind of tape, or will the heat on the other side of the board not be at such a temperature that the parts will fall out of the board?
                                Attached Files

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                                  #17
                                  Whenever you see the bunch of via grupped behind chip, it indicate that that ic probably have ground plane pad on center connected to board... so you expect trouble. Make a very good photos of that area, and do some measurements, note, say value od caps, shorts and soic8 all leg in diode mode and write that on picture... this value can use to compare it after work was done.................. When solder liquified, its surface tension hold component on place. In that state you must be very careful to do not touch any component, run hotair excessively on it or shake the board. If the board lay on desk on component side, you have to do some support that lift board from desk to not interference with bottom component. Do not cover it with anything on back side, but from heating side protect with metal shield (can of cola) electrolitic caps and connector and other valuable stuff.

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                                    #18
                                    I already bought a replacement chip (2x to be sure) and it doesn't have a grounding pad.

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                                      #19
                                      I don't like it at all

                                      I heat the chip with hot air and nothing happens. I set the temperature to 380°C and heated for 10 minutes. Then I increased the temperature to 400°C and heated for another 10 minutes. I don't see any solder melting. I increased the temperature to 420°C and nothing even after 10 minutes.

                                      After 30 minutes I resigned.
                                      Am I making a mistake somewhere?

                                      I was already warned that the metal surface can be soldered to the board from below. However, I have bought new chips and there is no metal surface on the chip.

                                      Specifically, it is a chip (see picture above) ADV 7623. It is an onkyo home theater page number. 13

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                                        #20
                                        Can you confirm that a thin wire like 0.1mm go from one corner to another diagonaly, like red drawing. If you have trouble putting it after chip, drag it behind legs like green drawing and pull up it to straight. You can determine if on center has barier observing lenght of wire.
                                        Attached Files

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