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CSD16327Q3: Thermal Resistance between Junction and Top of Package

Timothy Burroughs
Prodigy 60 points
Part Number: CSD16327Q3

Hello E2E Team,

I'm seeking confirmation on thermal resistance between the junction and the top of the CSD16327Q3 package.

I see two values listed in the product datasheet, but unsure if they are specifically for the thermal resistance through the plastic.

Thank you,

Tim

  • 0
    TI__Mastermind 34295 points

    Hi Tim,

    Thanks for your interest in TI FETs. TI specs thermal impedance from junction-to-case (bottom) and junction-to-ambient in the datasheet. The primary path to remove heat from the package is thru the large thermal pad on the bottom of the device and into the PCB. We do not spec junction-to-case (top) because it is much higher than the thermal impedance to the bottom of the package. Based on thermal simulations for similar packages, I would estimate it is between 20C/W and 30C/W but unfortunately, I have no data to back this up. Please refer to the blog in the link below for more information on how TI tests and specs thermal impedance of our FETs.

  • 0 in reply to John Wallace1
    Prodigy 60 points

    Hi John,

    Thank you for your reply and web link breaking down the datasheet parameters.

    Our design would use the device's bottom-side thermal pad as the primary conductive path to transfer heat.

    For high-power applications, where thermal vias on the bottom pad + a heatsink is an option, a few more questions:

    1. Is there an application note for installing the heatsink on the top of the package, with accompanying thermal transfer data?
    2. Any notes on optimal position of a heatsink for TI SON packages?

    We would like to parallelize our thermal strategy, by taking advantage of both sides of the FET (conduct heat to sinks in both directions, in parallel).

    Thank you,

    Tim

  • 0 in reply to Timothy Burroughs
    TI__Mastermind 34295 points

    Hi Tim,

    Thanks again for your interest in TI FETs. We do not have any application information on heatsinking this type of package. Adding a heatsink to remove heat from the top of the package is not going to be very efficient as most of the heat is removed thru the thermal pad on the bottom of the device and into the PCB. In my experience, I have seen users heatsink SON/QFN packages in a multiphase buck converter where multiple devices are placed in a line with a single heatsink covering all of them. The heatsink can be attached using screws, spring loaded push pins or with thermal epoxy (glue). A thermal interface material (TIM), pad or thermal grease is used to fill in imperfections where the two surfaces (package and heatsink) interface. I would recommend consulting with one of the heatsink manufacturers to get more ideas on how best to accomplish your thermal management objectives.