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Thermal resistance from Junction to board & junction to case required for HMC516LC5

Iam perfoming thermal analysis of PCB enclosed in enclosure, From datasheet of the component Thermal resistance(channel to die bottom) given is 76.9 °C/W. The value of which i considered is  Thermal resistance from junction to board 

This consideration is because iam performing thermal analysis in Ansys  ICEPAK  in which IC is modelled as a two resistor network

Since these components have exposed pad technically resistance towards board will be less question is my understanding of Resistance towards board is it correct & the how to find resistance towards top of the case

Parents Reply
  • Hi Mohamed023,

                                           First of all theHMC815B is a totally different chip with a different Pdiss and layout. So the theta numbers will be different. I also find it hard to believe that theta JA & theta JC for an air cavity package can be with in 0.3 degrees.

    Die layout and the Pdiss of the device all affect the thermal resistance.

    The interface from the channel to the ceramic lid is air. Air is not a very good thermal conductor. I would expect the Theta JC top for the HMC516LC5  as a rough estimate, to be double the theta JC to the exposed pad, ~153.8 C/W.


    Jim B

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