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IWR1843: Need advice for mmwave PCB

Poh Kok Keng
Genius 5322 points
Part Number: IWR1843

Dear Sir/Madam,

Need your advise on the finishing as stated below (from your TI reference document)

Most common plating used in industry, Electroless Nickel-Immersion Gold (ENIG), is not a good choice for mmWave boards due to its high losses.

TI EVM uses immersion silver plating that has lesser loss, comparatively.

However, immersion silver is susceptible to oxidation on prolonged exposure to air.

This oxidation does not impact the RF performance.

However, proper storage of the PCB is recommended to reduce the oxidation.

 

We need your opinions on the following options  :

(1) Full Organic Solder Protection (OSP) over the SMT pads and Antenna

(2) Full Lead Free solder over the SMT pads and Antenna

(3) Full immersion Tin over SMT pads and Antenna

(4) Selective OSP over bare copper on the SMT pads and Immersion silver on the Antenna

(5) do we need Ro4350B materials for PCB build? 

best regards,
Felix

  • 0
    TI__Mastermind 31680 points

    Hello Felix,

    Thankyou for reaching out. 

    I've forwarded your concern to our hardware expert. Please expect a response by early next week. 

    Thankyou for your patience. 

    Regards,

    Ishita

  • 0
    TI__Mastermind 25825 points

    Hello Felix,

        Thank you for studying in detail on this subject. 

    For more information you could refer to, TI mmWave Radar sensor RF PCB Design, Manufacturing and Validation Guide (https://www.ti.com/lit/an/spracg5/spracg5.pdf)

    1) Yes thin layer of OSP could be used on SMT pads and Antenna. However rework on the OSP surface finish would be challenging. 

    2)  Full lead free solder over the SMT pads are ok  but not on the Antenna. 

    3) Full immersion Tin over SMT pads: Tin has Whiskering issues, also sensitive to handling, Hence not popular during mmWave design. 

    4) Selective OSP over bare copper on the SMT pads and Immersion silver on the Antenna: This could be used for mmWave designs. Process cost may be higher due to higher manufacturing complexity. 

    5) RO4350B is not needed for the Materials build, R04835LOPRO would be suffcient and it will bond easily with other FR4 materials. 

    Thanks and regards,

    CHETHAN KUMAR Y.B.