Example10 Cooling of IC inside the Case by Natural Convection (Closed Space and Natural Convection Boundary Condition)

General

  • Heat dissipation of the IC by the natural convection is solved by the steady-state analysis. The IC is encased on the substrate.

  • The natural convection boundary condition is applied to the surface of the case to omit the analysis of open space outside the case. Only natural convection in the closed space inside the case is analyzed.

  • In [Example 9: Cooling of IC inside the Case by Natural Convection (Closed Space and Open Space)], the same model is used and the natural convection in the open space is analyzed as well.
    The outside of the case is analyzed in depth. Accordingly, the analysis time becomes longer.
     

  • 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 Condition

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

Option

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: 5 [mm]

Model

The substrate (VOL1), the IC (VOL2), and the case (CASE) are solid bodies.

The outer boundary condition is used. Natural convection (automatic calculation) is set for Heat Transfer: Convection.

Inside of the case (air) is a solid body.

 

Setting of Body Attributes, Materials, and Mesh Sizes

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

2/Solid

Air

000_Air(*)

3/Solid

CASE

001_Al *

4.0

* 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])

Thermal

Heat Transfer: Convection

Room temperature (ambient temperature): 25[deg]

Select Natural Convection (automatic calculation)

 

Results

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

The case and the air are hidden.

 

 

For comparison purpose, the results of
[Example 9: Cooling of IC inside the Case by Natural Convection (Closed Space and Open Space)] are shown as well where the outside of the case too is analyzed.

Similar results are obtained.

 

 

By switching the analysis type from thermal to fluid analysis, the flow velocity vectors are shown as below.

The cross section at x=0 is displayed.

In the graphics setup, the 3D vector is set OFF and the vectors are set to the same length.

Like the results of Example 9, the circulation is generated by the convection inside the case.