BGA Bond out lengths

Forums Devices OSD32MP15x BGA Bond out lengths

Viewing 4 reply threads
  • Author
    Posts
    • #10309
      Ian Guffickiguffick
      Participant

        I’m trying to match the lengths of PCB traces for the high speed signals.
        But simply matching the external length does not take into account any internal bond-out length difference.
        Do you have any data on the BGA bond out lengths for each pin.

        This is more important for the high speed signals, such as USB & DSI.
        But also for matching external Ethernet PHY signals on the normal port pins.

        Regards,
        Ian.

      • #10332
        Neeraj Dantu
        Moderator

          Ian,

          You don’t have to worry about SiP internals. If you match the trace lengths from the SiP balls to the external devices, you should be able to achieve optimal performance.

          Best,

          Neeraj

        • #10334
          Ian Guffickiguffick
          Participant

            Hi Neeraj,

            Sorry, but the internal BGA length is just as important as the external length.
            The BGA pins are 1mm apart, so even if they came from very close together on the STM die, there is a 1mm difference getting them to the pad.
            The same applies to the tracks placed on the PCB. The extra 1mm to get to the matched BGA pad needs to be taken into account.
            It’s the total length the matters not just the length of the external PCB track. The external PCB track length should be adjusted so that the total length matches.
            This is critical for both USB and DSI.

            For example have a look at STs AN5031 en.DM00389996.pdf page 69 and 76. This shows how ST specify the length difference for the normal BGA packages.

            It’s not quite as critical for the external Ethernt PHY RGMII signals, but then the difference between used BGA balls can be up to 5mm.

            Can you publish the internal BGA lengths used for bond out please?

            Regards,
            Ian.

          • #10440
            Tobias ScholzTobias
            Participant

              Is there an update on this question?

              • This reply was modified 4 years, 3 months ago by Tobias ScholzTobias.
            • #10449
              Neeraj Dantu
              Moderator

                Ian & Tobias,

                We apologize for the delay in getting you a response to this question. Please see below for the requested data for the high speed buses below:

                Signal NameTrace Length(um)Differential(um)
                DSIDSI_D1_N14889.249387.191
                DSI_D1_P14502.058
                DSI_D0_N15464.216927.249
                DSI_D0_P14536.967
                DSI_CK_N15307.686-410.481
                DSI_CK_P15718.167
                USB1USB1_N15379.511559.346
                USB1_P14820.165
                USB2USB2_N18453.704572.107
                USB2_P17881.597

                Note that all lengths are in microns.

                Best,

                Neeraj

            Viewing 4 reply threads
            • You must be logged in to reply to this topic.