Home / Examples / Thermal Analysis [Watt] / Example 28: Thermal Resistance with Heat Sink (Steady-state Analysis)

Example 28: Thermal Resistance with Heat Sink (Steady-state Analysis)

General

• The IC that generates constant heat is cooled with the heat sink having a known thermal resistance. The heat dissipation by natural convection is solved in the steady-state analysis.
   

• The temperature distribution and the heat flux vectors are solved.
   

• Unless specified in the list below, the default conditions are applied.
   

• Obtain this session's project file. (Right-click and choose 'Save link as')




• Results will vary depending on Femtet version and the PC environment.

 

Analysis Space

Item	Setting
Analysis Space	3D
Model Unit	mm

 

Analysis Conditions

Item	Setting
Solver	Thermal Analysis [Watt]
Analysis Type	Steady-state Analysis
Analysis Options	None

 

Model

A substrate (VOL1) and an IC (VOL2) are solid bodies.

Natural convection is set for the outer boundary condition.

The boundary condition [Heatsink] is set to the top of the VOL2 to analyze the heat transfer of the heat sink.

 

 

 

 

Body Attributes and Materials

Body Number/Type	Body Attribute Name	Material Name	Mesh Size
0/Solid	VOL1	006_Glass_epoxy *	2.0
1/Solid	VOL2	001_Alumina *	2.0

* Available from the material DB

 

 

IC (VOL2) is set as follows on the Heat Quantity tab.

Body Attribute Name	Tab	Setting
VOL2	Heat Quantity	1 W

Boundary Condition

The boundary conditions are set as follows:

Boundary Condition Name/Topology	Tab	Boundary Condition Type	Setting
Outer Boundary Condition	Thermal	Heat Transfer/Convection	Natural Convection (Automatic Coefficient Calculation) Room Temperature (Ambient Temperature): 25 [deg]
BC_Heatsink/Face	Thermal	Heat Transfer/Convection	Heat Sink Thermal Resistance: 17 [deg/W] Room Temperature (Ambient Temperature): 25 [deg]

 

 

 

Results

The temperature distributions of the substrate and IC are shown below.

 

The surface temperature of the IC is 40 deg. Removing the boundary condition [Heat Sink] and setting the outer boundary condition to natural convection (automatic coefficient calculation), the surface temperature of the IC rises to 93 deg.

This shows that the heat sink is dissipating heat.