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    #41
    Re: LED Resistor Calculations ...

    Originally posted by eccerr0r View Post
    The footprint model should have marked that node to be a DNC node so it would show up as a DRC or LVS error.
    If you're talking about the footprint that is used for the PCB design layout, I completely agree... that center pad should be electrically equivalent to the anode so that someone (like me) doesn't think it's available for a separate network in the schematic.

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      #42
      Re: LED Resistor Calculations ...

      Originally posted by diif View Post
      Your panel should really be Aluminium not FR4.
      OK, what I wanna know is ... if one uses an Aluminum backed PCB, aluminum can still conduct electricity ... unless they dope it with something that prevents that? I'm a little confused on how that works if you were to connect those center pins to an aluminum backing...

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        #43
        Re: LED Resistor Calculations ...

        Of course it conducts, it;s bare aluminium. You don't connect anything to it. The centre contact is the anode.
        https://www.pcbway.com/pcb_prototype...minum_PCB.html

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          #44
          Re: LED Resistor Calculations ...

          Originally posted by diif View Post
          Of course it conducts, it;s bare aluminium. You don't connect anything to it. The centre contact is the anode.
          https://www.pcbway.com/pcb_prototype...minum_PCB.html
          So then how would you connect the LED to the aluminum backing for heat dissipation? Or is it just having the aluminum close to the LEDs that it will pick up the heat they are kicking out and transfer it away?

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            #45
            Re: LED Resistor Calculations ...

            Aluminum PCB just means the backing is aluminum, of course this will not function as a regular PCB, so there's a layer of dielectric on the aluminum. Then there's another layer of copper over the dielectric which gets etched. Heat transfer still needs to go through the thin dielectric layer, so it's not as good as being soldered straight to the aluminum but it's better than FR-4.

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              #46
              Re: LED Resistor Calculations ...

              Yes, with large copper planes on the front and the back solid aluminium the whole PCB becomes a heatsink.

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                #47
                Re: LED Resistor Calculations ...

                Most high power LED dies have two bonding wires, with the die (substrate) glued or soldered to the cathode leg.
                OP's having a third pad seems like it's just cheap or something.
                Attached Files

                Comment


                  #48
                  Re: LED Resistor Calculations ...

                  Originally posted by eccerr0r View Post
                  Aluminum PCB just means the backing is aluminum, of course, this will not function as a regular PCB, so there's a layer of dielectric on the aluminum. Then there's another layer of copper over the dielectric which gets etched. Heat transfer still needs to go through the thin dielectric layer, so it's not as good as being soldered straight to the aluminum but it's better than FR-4.
                  So I did some re-design on the panel, and I also made a 12-volt version ... everything on one layer without any center pins on the LED at all on the board, and I had originally had some through-hole components but when I had PCBWay quote them, they wanted over $300 ... so I made everything surface without any through-hole components and am waiting for that quote... apparently, when you spec aluminum for the board, it takes longer to get it quoted, but if the quote remains at the price it was when I put it in the cart, then ill order them up and should end up with a better panel that I have now.


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                    #49
                    Re: LED Resistor Calculations ...

                    I have a dead GE A19 bulb I need to take apart and do failure analysis...

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                      #50
                      Re: LED Resistor Calculations ...

                      Originally posted by eccerr0r View Post
                      I have a dead GE A19 bulb I need to take apart and do failure analysis...
                      You're talking about a replacement light bulb? What's the point? Those things are cheap now a days.

                      Comment


                        #51
                        Re: LED Resistor Calculations ...

                        I think you should look at your design to better take advantage of the copper front.

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                          #52
                          Re: LED Resistor Calculations ...

                          Originally posted by diif View Post
                          i think you should look at your design to better take advantage of the copper front.
                          +1
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                            #53
                            Re: LED Resistor Calculations ...

                            Originally posted by diif View Post
                            I think you should look at your design to better take advantage of the copper front.
                            Could you be more specific?

                            Comment


                              #54
                              Re: LED Resistor Calculations ...

                              Originally posted by EasyGoing1 View Post
                              Could you be more specific?
                              You want the whole of the front to heat up evenly, remove those traces and have the + and - pads the full width of the board.

                              Comment


                                #55
                                Re: LED Resistor Calculations ...

                                Originally posted by diif View Post
                                You want the whole of the front to heat up evenly, remove those traces and have the + and - pads the full width of the board.
                                You mean like this?





                                The copper layer which is all on the GND net, is underneath each LEDs heat dissipation node without any exposed copper so it will heat the entire copper plane that is GND electrically then presumably that will pass to the aluminum for dissipation...
                                Last edited by EasyGoing1; 05-22-2021, 09:15 PM.

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                                  #56
                                  Re: LED Resistor Calculations ...

                                  No not like that, I still see traces, the heat is trapped under the LEDs and can't go sideways.
                                  Draw thick lines from almost the top to the bottom that is your + pad the a tiny gap then another for the - and so on. The only thin trace will be the - round the edge going pack to the - input.

                                  With LEDs you're routing heat as well as electricity, heat is your primary concern.
                                  Last edited by diif; 05-23-2021, 02:47 AM.

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                                    #57
                                    Re: LED Resistor Calculations ...

                                    And still the NC pad are all connected together? Or are you using a different chip now?

                                    note: depending on soldermask insulation is not a good idea...
                                    Last edited by eccerr0r; 05-23-2021, 03:18 PM.

                                    Comment


                                      #58
                                      Re: LED Resistor Calculations ...

                                      Originally posted by diif View Post
                                      No not like that, I still see traces, the heat is trapped under the LEDs and can't go sideways.
                                      Draw thick lines from almost the top to the bottom that is your + pad the a tiny gap then another for the - and so on. The only thin trace will be the - round the edge going pack to the - input.

                                      With LEDs you're routing heat as well as electricity, heat is your primary concern.
                                      Originally posted by eccerr0r View Post
                                      And still the NC pad are all connected together? Or are you using a different chip now?

                                      note: depending on soldermask insulation is not a good idea...


                                      OK, I colored the copper layer which is all electrically GROUND in yellow. Everywhere you see an X. the center pin of the LED is pressed against the SOLDERMASK on the board... the center pins are NOT soldered to the board. THEN, the back of the board is aluminum...

                                      Tell me how to dissipate heat better than this?

                                      Comment


                                        #59
                                        Re: LED Resistor Calculations ...

                                        I'm not sure why you're capitalising certain words but this photo should help explain.
                                        The thin bit you see is the only part of the board apart from near the edge there is no used copper, when i say used, I mean used for dissipating heat, power is coming top to bottom. The anodes and cathodes are all joined in big wide copper strips.
                                        The centre pad on your LED should be soldered it's connected to the anode.
                                        Attached Files

                                        Comment


                                          #60
                                          Re: LED Resistor Calculations ...

                                          Originally posted by diif View Post
                                          I'm not sure why you're capitalising certain words but this photo should help explain.
                                          The thin bit you see is the only part of the board apart from near the edge there is no used copper, when i say used, I mean used for dissipating heat, power is coming top to bottom. The anodes and cathodes are all joined in big wide copper strips.
                                          The centre pad on your LED should be soldered it's connected to the anode.
                                          "The anodes and cathodes are all joined in big wide copper strips" - so in my design, this is a problem ...

                                          Here is the schematic for my LED panel... as you can see, if I just connected all of the anodes and cathodes ... it would not work at all.



                                          Also, the center pin does NOT need to be soldered for the LED to work. The two ends of the LED are all that are necessary for the things to light up.

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