Copper lines on circuit board

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  • SmartVision
    Senior Member
    • Jun 2011
    • 58

    #1

    Copper lines on circuit board

    Hi everyone, I need help!

    I tried to change voltage regulator (transistor) on circuit board of my monitor and I got in trouble with copper line.

    First I tried to desolder transistor but somehow I tore whole copper line...

    Now I cant solder back replacement transistor and I don't know what can I do so if anyone could help me I would be thankful.
  • trebo
    Badcaps Veteran
    • Feb 2010
    • 514
    • Wales, UK

    #2
    Re: Copper lines on circuit board

    lets have a close up picture of damaged area if you can, it helps

    Comment

    • SmartVision
      Senior Member
      • Jun 2011
      • 58

      #3
      Re: Copper lines on circuit board

      Side legs of the transistor (see the picture), middle one is not used.

      Picture is before the damage happened.
      Attached Files
      Last edited by SmartVision; 10-05-2012, 11:59 AM.

      Comment

      • t.j.
        Badcaps Veteran
        • Apr 2010
        • 383
        • canada

        #4
        Re: Copper lines on circuit board

        follow to where the trace goes to! solder down the good side an take 30g wire an link messed end to where trace goes to!

        Comment

        • mariushm
          Badcaps Legend
          • May 2011
          • 3799

          #5
          Re: Copper lines on circuit board

          That regulator is a standard 1084 voltage regulator :



          The tab and the pin in the middle is the output voltage, and in your case it's probably 1.8v

          If you look at the second picture in your last post, the pin on the left of the tab is the INPUT, which should be the thin copper trace that probably goes to the + sign of that capacitor. You see it just under the text saying C107, taking a right turn under the capacitor there. See if the trace goes to the + sign of the capacitor.

          If that's the copper trace you broke, you could either take a razor blade or some small screwdriver and scrape off the "paint" from the copper trace on top and use a small wire to connect the chip pin , or use a longer insulated wire and solder this wire to the + lead of the capacitor on the other side and then to the pin.


          The third pin is the ground or adjust pin , it's connected either to a large pad of copper or to a resistor near it.

          The tab is soldered to a large area of copper with those bumps of solder all around and a lot of small drilled holes. That's basically a heatsink... those tiny holes connects the large copper surface under the chip with another large copper surface on the other side, and those bumps of solder also help increase the surface of the "heatsink", it helps the chip stay cool.

          Comment

          • SmartVision
            Senior Member
            • Jun 2011
            • 58

            #6
            Re: Copper lines on circuit board

            Thanks everyone for answers, I'll do my best to do it right.

            Also I have a problem with new transistor's dimensions. I ordered this one from ebay and it's bigger than the old one:

            http://www.ebay.com/itm/LD1084D2T-R-...item2322fc0d3f

            Crap

            Comment

            • 999999999
              Badcaps Veteran
              • Sep 2006
              • 774
              • USA

              #7
              Re: Copper lines on circuit board

              ^ Drill a couple holes in the side of the heatsink on the processor in the middle of the board, get a piece of plate metal and drill two slightly larger holes in it, put the regulator w/thermal grease on it, between the heatsink and the piece of plate mental and screw that together.

              Solder wires from the regulator pins to the appropriate PCB traces... or just order another regulator IC.

              Also note, that you might be able to bend the larger regulator's pins inward to be the same spacing as the original, and scrape away the lacquer on the PCB so there's sufficient copper exposed.
              Last edited by 999999999; 10-06-2012, 12:59 PM.

              Comment

              • mariushm
                Badcaps Legend
                • May 2011
                • 3799

                #8
                Re: Copper lines on circuit board

                No, I don't really recommend drilling that heatsink above the processor, you might break some pins from the vibrations or do more damage.

                That metal tab on the chip needs to be soldered on the pcb but you don't have to solder it exactly in the place of the old chip, that whole surface around the chip is its heatsink.

                Look at the picture:



                All that area surrounded by red is a connected to the tab of the IC. So you can solder the tab to any of those bumps of solder.

                Heat up one or two of those bumps and add some solder to them. Take the new chip, put some solder on the tab on the back.
                Now put the chip over the solder on the pcb you just put before, keep the chip in place with something (screwdriver or something) and heat up the solder and the tab for a few seconds until everything is liquid and then the chip should be soldered there.
                Now you can use two short pieces of wire to solder the legs to where they were supposed to go.

                But remember, you need to put solder on both surfaces, mainly because solder has flux in it and flux is important to remove the oxides that are there on the surface of that pcb heatsink. The oxides would not make the chip "stick" to the heatsink, they would prevent the heat from being radiated into the pcb.
                Attached Files

                Comment

                • 999999999
                  Badcaps Veteran
                  • Sep 2006
                  • 774
                  • USA

                  #9
                  Re: Copper lines on circuit board

                  ^ I was thinking the heatsink would be taken off to do the drilling, I skipped a lot of the details in describing a general process and didn't think about the issue of not everyone having thermal epoxy or tape.

                  Comment

                  • SmartVision
                    Senior Member
                    • Jun 2011
                    • 58

                    #10
                    Re: Copper lines on circuit board

                    Thank you guys vecry much

                    Comment

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