Home / Examples / Coupled Analysis / Electric-Thermal Analysis [Coulomb/Watt] / Example 1: Heating of Conductive Strip (Steady-State Analysis)

Example 1: Heating of Conductive Strip (Steady-State Analysis)

General

The model is a strip line having bend shapes. An electric potential is given across the strip line and the electric current is solved in the electric analysis.
Then the eventual joule loss and the resulting temperature rise are solved in the thermal analysis.
The distributions of current and temperature are viewed.
Unless specified in the list below, the default conditions will be applied.

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

Analysis Space

Item	Settings
Analysis Space	3D
Model Unit	mm

Analysis Conditions

Select an electric solver [Coulomb] and a thermal solver [Watt].

This is a steady-state analysis.

Item

Settings

Solver

Electric Analysis [Coulomb]

Thermal Analysis [Watt]

Analysis Type

Steady-state Analysis

Model

The substrate is a box solid body.
The strip line is a sheet body on the substrate.

Body Attributes and Materials

Body Number/Type	Body Attribute Name	Material Name
0/Solid	Board	001_Alumina *
6/Sheet	Strip	008_Cu *

* Available from the material DB

It is assumed that there is no current flow in the alumina substrate.

The conductive strip is a sheet body. The thickness must be defined in the body attribute, where the resistance can be entered too.

Current and heat source will vary depending on the thickness.

Body Attribute Name	Thickness/Width	Analysis Domain
Board		Solver: Deselect Electric Analysis (Coulomb)
StripLine	Thickness of Sheet Body: 0.1 mm

Resistivity/conductivity is required to be set to “Board” to run the Coulomb/Watt solver
even though it is not used in the electric analysis. As the resistivity in the database of the 001_Alumina is not defined by default,

the value is temporarily set to 1.0. (The result will not be affected)

Material Name	Resistivity
001_Alumina	1.0 [Ωm]

Boundary Conditions

The temperature of the bottom face of the substrate is set to 25 [deg] using the boundary condition of T0.
The [Adiabatic] boundary condition is set to the faces that the strip line ends using the boundary condition of T_Wall.
This keeps the outer boundary condition from being applied on the faces.
Boundary conditions, V0 and V1, define the electric potential at each end of the microstrip line.
The heat transfer to the ambient is defined by the outer boundary condition.

Boundary Condition Name/Topology	Tab	Boundary Condition Type	Settings
T_Wall/Face	Thermal	Adiabatic
T0/Face	Thermal	Temperature	25 [deg]
V0/Edge	Electric	Electric Wall	Electric Potential Specified, Waveform: Constant, Electric Potential: 0.00 V
V1/Edge	Electric	Electric Wall	Electric Potential Specified, Waveform: Constant, Electric Potential: 0.01 V
Outer Boundary Condition *	Thermal	Heat Transfer: Convection	Heat Transfer Coefficient: 10 [W/m2/deg] Ambient Temperature: 25 [deg]

* To set Outer Boundary Condition, go to the [Model] tab

and click [Outer Boundary Condition] .

Results

The vectors of the current density are shown below.

The current density is not even at around the bending area of the strip.

The temperature contour as a result of thermal analysis (Watt) is shown below.

Temperature rise due to heat generation occurs along the strip line, and the heat is transmitted to the alumina substrate.