General
Two heat sources are placed on a substrate. Some heat is conducted to the bottom of the substrate through via holes.
The heat is released to the ambient by natural convection. The steadystate analysis is performed.
The temperature distribution and the heat flux vectors are solved.
Unless specified in the list below, the default conditions will be applied.
Item 
Settings 
Analysis Space 
3D 
Model unit 
mm 
Item 
Settings 
Solvers 
Thermal Analysis [Watt] 
Analysis Type 
Steadystate analysis 
Options 
N/A 
The finer mesh size is set for via holes (HOLE), where the heat flux is expected to change drastically.
Body Number/Type 
Body Attribute Name 
Material Name 
Mesh Size 
0/Solid 
SUB 
006_Glass_epoxy * 

1/Solid 
GND 
008_Cu * 

2/Solid 
MAINCHIP 
001_Alumina * 

3/Solid 
SUBCHIP 
001_Alumina * 

4/Solid 
HOLE 
008_Cu * 
0.5 
5/Solid 
HOLE 
008_Cu * 
0.5 
6/Solid 
HOLE 
008_Cu * 
0.5 
7/Solid 
HOLE 
008_Cu * 
0.5 
8/Solid 
HOLE 
008_Cu * 
0.5 
9/Solid 
HOLE 
008_Cu * 
0.5 
10/Solid 
HOLE 
008_Cu * 
0.5 
11/Solid 
HOLE 
008_Cu * 
0.5 
* Available from the Material DB
The heat sources of MAINCHIP and SUBCHIP are set up as follows.
Body Attribute Name 
Tab 
Settings 
MAINCHIP 
Heat Source 
0.2[W] 
SUBCHIP 
Heat Source 
0.1[W] 
It is assumed that the heat is released to the ambient only from the top and bottom faces of the model. The heat released from the side faces is ignored because the total area of the side faces is much smaller than that of the top and bottom faces.
Boundary Condition Name/Topology 
Tab 
Boundary Condition Type 
Settings 
Bottom/Face 
Thermal 
Heat Transfer/Ambient Radiation 
Coefficient for natural convection (*1) : 1.39[W/m2/deg5/4] Room Temperature : 25[deg] 
TOP/Face 
Thermal 
Heat Transfer/Ambient Radiation 
Coefficient for natural convection (*2) : 2.78[W/m2/deg5/4] Room Temperature : 25[deg] 
MAINCHIPUPPER/Face 
Thermal 
Heat Transfer/Ambient Radiation 
Coefficient for natural convection (*3) : 6.41[W/m2/deg5/4] Room Temperature : 25[deg] 
SUBCHIPUPPER/Face 
Thermal 
Heat Transfer/Ambient Radiation 
Coefficient for natural convection (*4) : 7.62[W/m2/deg5/4] Room Temperature : 25[deg] 
The formulas to calculate the coefficients(*14) for natural convection are shown below. See [Heat Transfer/Ambient Radiation] for more information.
(*1) BOTTOM
2.51×C×（1/L)＾（1/4） = 1.39 [W/m2/deg5/4]
where
C = 0.26
Size of the substrate : 0.06×0.04
L (Typical Length) = (0.06 x 0.04 x 2) / (0.06 + 0.04) = 0.048
(*2) TOP
2.51×C×（1/L)＾（1/4） = 2.78 [W/m2/deg5/4]
where
C = 0.52
Size of the substrate : 0.06×0.04
L (Typical Length) = (0.06 x 0.04 x 2) / (0.06 + 0.04) = 0.048
(*3) MAINCHIPUPPER
2.51×C×（1/L)＾（1/4） = 6.41 [W/m2/deg5/4]
where
C = 0.96
Size of the chip : 0.02×0.02
L (Typical Length) = (0.02 x 0.02 x 2) / (0.02 + 0.02) = 0.02
(*4) SUBCHIPUPPER
2.51×C×（1/L)＾（1/4） = 7.62 [W/m2/deg5/4]
where
C = 0.96
Size of the chip : 0.01×0.01
L (Typical Length) = (0.01 x 0.01 x 2) / (0.01 + 0.01) = 0.01
The temperature distribution is shown below.
MAINCHIP has the highest temperature in this model.
The vectors of the heat flux are shown below.
The heat is well transfered through the via holes.