2021.08.18
Points of this article
・Thermal resistance and thermal characterization parameters are defined in JESD51, which is a JEDEC standard.
・There are basic applications for the different thermal resistances and thermal characterization parameters; the relevant thermal resistances and thermal characterization parameters are used in calculations.
In this article, we define θJA and ΨJT, parameters of actual thermal resistance data presented in the previous article.
We begin by reviewing the previous article.
The following schematic diagram enables the reader to conceptualize θJA and ΨJT.
θJA is the thermal resistance from the junction to the ambient environment; heat dissipation occurs over multiple thermal paths. ΨJT is the thermal characterization parameter from the junction to the center of the top surface of the package.
Moreover, the thermal resistance from the junction to the package top surface (θJC-TOP) and the thermal resistance from the junction to the package bottom surface (θJC-BOT) are also defined, and are illustrated below. Where θJC-TOP and ΨJT are concerned, it should be noted that there is a slight difference between the “package top surface” and the “center of the package top surface”.
These are defined by the JEDEC standard JESD51. Below we have summarized the definitions, applications, and calculation formulae.
Symbol | Definition | Applications | Formula |
---|---|---|---|
θJA | Junction-to-ambient thermal resistance※1 | Comparison of heat dissipation performance of packages with different shapes | θJA = (TJ ? TA) / P |
ΨJT | Thermal characterization parameter representing the temperature difference between junction and package top center for a power consumption P of the entire device | Estimation of the junction temperature for an entire equipment (actual heat dissipation environment) | ΨJT = (TJ ? TT) / P |
θJC-TOP | Junction-to-package-top thermal resistance. Heat dissipation path is at the package top surface only, thermal insulation elsewhere. | Used in simulations of heat conduction, thermal fluids, etc. Can also be applied to thermal resistance network method |
θJC-TOP = (TJ ? TC-TOP) / P |
θJC-BOT | Junction-to-package-bottom thermal resistance. Heat dissipation path is at the package bottom surface only, thermal insulation elsewhere. | Used in simulations of heat conduction, thermal fluids, etc. Can also be applied to thermal resistance network method |
θJC-BOT = (TJ ? TC-BOT) / P |
Downloadable materials, including lecture materials from ROHM-sponsored seminars and a selection guide for DC-DC converters, are now available.
Downloadable materials, including lecture materials from ROHM-sponsored seminars and a selection guide for DC-DC converters, are now available.