Example6 Cooling of IC by Natural Convection

General

Heat dissipation of an IC by the forced convection is solved by 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.

Analysis Space

Item	Setting
Analysis Space	3D
Model Unit	mm

Analysis Conditions

Item	Setting
Solver	Fluid Analysis [Bernoulli] Thermal analysis [Watt]
Analysis Type	Fluid analysis: Steady-state analysis Thermal analysis: Steady-state analysis
Laminar Flow/Turbulent Flow	Select Turbulent Flow
Options	Select Take Buoyancy into Account (Natural Convection)
Layer Mesh Setting for Wall Surface (General Settings)	Parameters for Automatic Creation Expected Temperature Difference: 50[deg]
Meshing Setup	General Mesh size: 10 [mm]

Model

The model is a box solid body. The material is Air (000_Air).

Set natural inflow/outflow to the outer boundary condition of Inlet/Outlet.

The substrate (VOL1) and IC (VOL2) are solid bodies.

Setting of Body Attributes, Materials, and Mesh Sizes

Body Number/Type	Body Attribute Name	Material Name	Mesh Size
0/Solid	VOL1	006_Glass_epoxy *	0.2
1/Solid	VOL2	001_Alumina *	0.2
2/Solid	Air	000_Air(*)	–

* Available from the material DB

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

Body Attribute Name	Tab	Setting
VOL2	Heat Source	1W

Boundary Condition

Boundary Condition Name/Topology

Tab

Boundary Condition Type

Setting

Outer Boundary Condition

Fluid-Thermal

Inlet/Outlet

Natural Inflow/Outflow

Inflow temperature: Use ambient temperature (25[deg])

Results

The temperature distribution is shown below.

For easy viewing of the temperature distributions of the substrate and the IC, the ambient air field is hidden by right-clicking the air body and selecting [Hide Body Field].

You can see the heat around the IC is higher than the other area.

The cross section at x=0 is shown as below. The air body is shown as well.

There is a high-temperature area above the IC. It can be observed that the heat is transmitted mainly upward.

Next, switch the solver type from thermal to flud analysis. The flow velocity vectors are show as below.

In the graphics setup, the 3D vector is set OFF.

It is observed that the air heated by the IC is moving upward.