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CC3235MODS: harsh environment survival question

Henry Nguyen3
Intellectual 290 points
Part Number: CC3235MODS
Other Parts Discussed in Thread: CC3235SF

Hello,

we have some questions about CC3235MODS.  in our application, this part just needs to survive through harsh shocking environment. 

we think we know how to deal with it by putting extra shock damping and support around the component, but we have some questions about the part in regarding about the data sheet: https://www.ti.com/lit/ds/symlink/cc3235mods.pdf?ts=1626129620520&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FCC3235MODS

1- what is the bottom terminated components (TBC) termination metallurgy?  is it ENIG terminations?

2- section 11.4 of the spec mentioned about the metal cap that is installed over the module.  we assume that this is for RF shield.  there are few questions:

      2.1 - is this shield soldered onto the module or connected mechanically?

      2.2 - I assume we have to have this lid for RF shield, otherwise, this module will not work right?   how come the shield is not needed on CC3235SF launch pad RF section layout?

      2.2 - if we put epoxy between the component and the metal lid to hold the lid and everything together, would it impact the RF performance?

3- section 11.2.2 falling section, we assume that you meant the part free falling without any shock damping support right?  what kinds of soldering (alloy and melting temperature) / construction are used on this board?  what are the fragile parameters or sections or components that can be destroyed on shock? 

     3.1- we are using lead-free reflow, do you see any issue with the secondary reflow issue in the module?

4- what is the PCB laminate material (FR4? Tg?) for CC3235MODS module?

Thanks and Best Regards,

Henry

  • 0
    TI__Mastermind 46761 points

    Hi Henry,

    The metal lid is actually not an RF shield. It is soldered onto the PCB. The module will operate without the lid. Epoxy under the metal lid will impact RF performance.

     I will look into your other questions and get back to you by next week at the latest.

    Thanks,

    Seong

  • 0 in reply to Seong Kim
    Intellectual 290 points

    Hi Seong,

    thanks for the answer.  I am confused now about the lid. 

    can you please let us know what the lid used for?  why is it on the module?  

    the epoxy is nonconductive (more like silicon glue), can you please give us a rationale on why putting epoxy under the lid impact the RF performance if the lid is not required first place.  we are very confused now.

    Thanks and Best Regards,

    Henry

  • 0 in reply to Henry Nguyen3
    TI__Mastermind 46761 points

    Henry,

    Actually, the epoxy will not affect RF if the compound is suitable for 2.4 and 5GHz band.

    Although the module is capable of working without the lid, it is recommended not to remove it as the module was designed to have the lid and removing it may affect the RF performance. More importantly, you will also not be able to leverage the module's certification without the lid. 

    BR,

    Seong

  • +1 in reply to Henry Nguyen3
    TI__Mastermind 46761 points

    Henry,

    1. Bottom terminal are Electroless Ni Immersion Gold (ENIG)
    2. Yes, we meant the module free falling could cause damage. The module was built with SAC 305 solder alloy. Reflow peak temp was 245C. We ran mechanical stress test and the module was able to withstand 300N without damage
    3. This module was qualified as MSL3, peak temp 260C. We expect customer to mount this module onto their PCB with no more than 2 times reflow.
    4. The laminate material is NPG-170N which is Glass Cloth Base Epoxy Resin, Flame Retardant Copper Clad Laminate. Tg is 170C.

    BR,

    Seong