JESD have specified the thermal so there is official documents in JESD official website, you can download directly
JESD15-3 Two-Resistor Compact Thermal Model Guideline - Junction-to-Case
JESD51-8 Integrated Circuit Thermal Test Method Environmental Conditions — Junction-to-Board
JESD51-12 Guidelines for Reporting and Using Electronic Package Thermal Information
https://www.jedec.org/ (need to registration if you don't have an account, free download)
Junction-to-board thermal resistance (θJB )
This parameter is measured in a ring cold plate fixture (see JESD51-8). This test fixture is designed to
ensure that all the heat generated in the package is conducted to the cold plate via the board.
The metric is defined as:
JB ( J B ) H θ = T − T / P
where θJB = thermal resistance from junction-to-board (ºC/W)
TJ = junction temperature when the device has achieved steady-state after application
of PH (ºC)
TB = board temperature, measured at the mid point of the longest side of the package no
more than 1mm from the edge of the package body (ºC)
PH = heating power which produced the change in junction temperature (W)
It is important to note that the θJB metric includes a contribution from the thermal resistance of the test
board. Therefore, the thermal conductivity of the board affects the measurement results. The JESD51-
8 standard requires that the metric be measured on a 2s2p board defined in JESD51-7, 9, 10, or 11.
Measurement of the board temperature very close to the edge of the package body is also intended to
minimize the contribution from the board.
Junction-to-case thermal resistance (θJCtop )
The metric is measured in a top cold plate fixture and is defined as:
( ) JCtop J Ctop H θ = T −T / P
where θJCtop = thermal resistance from junction-to-case (ºC/W)
TJ = junction temperature when the device has achieved steady-state after application
of PH (ºC)
TCtop = case temperature, measured at center of the package top surface (ºC)
PH = heating power in the junction that causes the difference between the junction
temperature TJ and the case temperature TCtop; this is equal to the power passing
through the cold plate (W)
Note: for more JEDEC standards, you can also search in this website.
Timing Knowledge Base
Thermal related reference documents
Silicon Labs have an application note about thermal, that is AN765, you can download from https://www.silabs.com/documents/public/application-notes/an765.pdf
JESD have specified the thermal so there is official documents in JESD official website, you can download directly
JESD15-3 Two-Resistor Compact Thermal Model Guideline - Junction-to-Case
JESD51-8 Integrated Circuit Thermal Test Method Environmental Conditions — Junction-to-Board
JESD51-12 Guidelines for Reporting and Using Electronic Package Thermal Information
https://www.jedec.org/ (need to registration if you don't have an account, free download)
Junction-to-board thermal resistance (θJB )
This parameter is measured in a ring cold plate fixture (see JESD51-8). This test fixture is designed to
ensure that all the heat generated in the package is conducted to the cold plate via the board.
The metric is defined as:
JB ( J B ) H θ = T − T / P
where θJB = thermal resistance from junction-to-board (ºC/W)
TJ = junction temperature when the device has achieved steady-state after application
of PH (ºC)
TB = board temperature, measured at the mid point of the longest side of the package no
more than 1mm from the edge of the package body (ºC)
PH = heating power which produced the change in junction temperature (W)
It is important to note that the θJB metric includes a contribution from the thermal resistance of the test
board. Therefore, the thermal conductivity of the board affects the measurement results. The JESD51-
8 standard requires that the metric be measured on a 2s2p board defined in JESD51-7, 9, 10, or 11.
Measurement of the board temperature very close to the edge of the package body is also intended to
minimize the contribution from the board.
Junction-to-case thermal resistance (θJCtop )
The metric is measured in a top cold plate fixture and is defined as:
( ) JCtop J Ctop H θ = T −T / P
where θJCtop = thermal resistance from junction-to-case (ºC/W)
TJ = junction temperature when the device has achieved steady-state after application
of PH (ºC)
TCtop = case temperature, measured at center of the package top surface (ºC)
PH = heating power in the junction that causes the difference between the junction
temperature TJ and the case temperature TCtop; this is equal to the power passing
through the cold plate (W)
Note: for more JEDEC standards, you can also search in this website.