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IWR6843ISK: Own antenna design questions

user5310849
Intellectual 730 points
Part Number: IWR6843ISK

Hello TI,

my colleagues are starting with designing custom module based on your IWR6843ISK design. As they opened the Altium files they noticed many vias between antenna ground and next conductive layer of the board. These holes are moreover filled with epoxy and close again with conductive material. What is the purpose of all this?

Unfortunately, our PCB manufacturer is not able to make such dense micro-vias. Is this really critical? There is no note about this in your guidelines. Is there alternative to those micro-vias we can use in our design? 

Thank you

Lukas

  • 0
    TI__Mastermind 33805 points
    Hi Lukas,

    Please review linked document.
    www.ti.com/.../spracg5.pdf

    The IWR6843ISK mmWave antenna is a 60Ghz high frequency antenna, the design and manufacturing this antenna affects critical RF performance.

    Regards,
    Charles O
  • 0 in reply to Charles Oladimeji
    Intellectual 730 points

    Thank you Charles, unfortunately there are many unanswered questions.

    The guidelines do not say anything about micro-vias surrounding the RF paths and antenna.

    Is their size and density so critical?

    Thank you, Lukas

  • 0 in reply to user5310849
    TI__Mastermind 25825 points
    Hello,

    Micro vias around the GCPW (Grounded co-planar wave-guide ) transmission line and around the Antenna regions are the most important.
    Micro vias around the transmission line governs the 50 Ohm impedance requirements and return loss requirements. Micro vias around the Antennas helps in providing higher isolation between the Antennas both on the Rx antenna and Tx antenna pairs.
    Filling of vias are mandated only around the BGA area, and may not be needed all around the board.
    Around the Antenna area via fencing is provided to protect or shield for the EM signals. And there are micro vias placed ground planes top and inner layer so that tighter ground coupling is ensured between top layer and Layer 2 ground layers. Density of vias could be relaxed here.

    Thanks and regards,
    CHETHAN KUMAR Y.B.
  • 0 in reply to CHETHAN KUMAR Y.B.
    Intellectual 730 points

    Thank you very much for valuable info. I think now we understand most of it.

    What do you mean with filing vias only around the BGA area? Are we talking about those under the BGA chip or outside? Is it necessary to fill all the micro-vias in the BGA area or just those used for soldering BGA pads. What is the true purpose of filling?

    Thanks, Lukas

  • 0 in reply to user5310849
    TI__Mastermind 33805 points
    Hi,

    In general filled Vias help with
    1. Current handling
    2. Heat Transfer
    3. Improved manufacturing/soldering reliability

    Regards,
    Charles O