convection correlations for pcb
TRANSCRIPT
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Chapter 65: Convection Correlations for PCB
65 Convection Correlations for
Printed Circuit Board (PCB)
Summary 1209
Introduction 1210
Modeling Details 1210
Solution Highlights 1210
Results 1218
Modeling Tips 1219
Input File(s) 1219
Video 1219
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1209CHAPTER 65
Convection Correlations for Printed Circuit Board (PCB)
Summary
Title Chapter 65: Convection Correlations for PCB
Features Natural convection correlation 701 by using PCONV1 entry
Forced convection correlation 507 by using PCONV1 entry
Contact loads by using PRJCON and SET3 cards
Geometry
The dimension of PCB is 9 x 6 x 0.0093 inches (copper thickness)
Material properties PCB: Copper K = 9.9 W/in C; Copper Thickness = 0.0093 in
Chips: K = 2.24 W/inC
Air: K = 6.66e-4 W/inC; Cp = 456.2 J/lbmC; = 5.01e-5 lbm/in; = 1.03e-6 lbm/in s, = 3.43e-3/C
Analysis characteristics Solution 400/RC Network solver. Steady state thermal analysis.
Boundary conditions Wall temperature = 25C
For Natural convection model: Tair = 20C
For Forced convection: Inlet Air Temperature = 20C
Applied loads Total surface heat = 5W, Total Heat on chips: 7.5W, 5W, 5W
Contact load between PCB and chips with coefficient =12 W/in C Convection with correlation 701 for natural convection model
Coupled advection with correlation 507 for forced convection model
Mass flow rate = 3.2E-3 lbm/s
Hydraulic Diameter = 0.2 in
Flow Cross Section = 0.6 in
Interval between chips and next PCB = 0.1 in
Element type CQUAD4 for PCB
CTETRA for chips CHBDYP/FTUBE for air flow (for natural convection model)
FE results Temperature result:
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MD Demonstration Problems
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Introduction
This problem demonstrates the convection correlation feature of SOL 400 RC Network Solver.
Modeling DetailsThe dimension of PCB is 9 x 6 x 0.0093 inches (copper thickness). The two edges are fixed to the slots and have a
constant boundary temperature of 25C. The total circuit power on the PCB is 5W, and the total power of the three
chips is 7.5W, 5W, and 5W, respectively. The PCB mesh and chip mesh do not match each other. RC Network Solver
has a special contact algorithm to deal with that.
The convection correlation 701 is used to simulate the natural convection of PCB and chips. The air temperature is
20C. The convection correlation 507 is used to simulate the forced convection. The forced convection is applied to
both sides of the PCB and outer side of the chips. The inlet air temperature is 20C.
Figure 65-1 PCB and Chips Model
Figure 65-2 Natural and Forced Convection Models
Solution HighlightsConvection correlations are used to calculate the convection coefficients in different situations. MD Nastran RC
Network Solver supports 44 convection correlations. Each convection correlation consists of three tabs: CorrelationView, Variables, and Additional Coefficient. Correlation View form includes the description, formula, illustration, and
5 W
Constant Boundary Temperature = 25 CoContact Coefficient = 1.2 W/in C2 o
20 Co
20 Co
Inlet T = 20 Co0.1 in
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1211CHAPTER 65
Convection Correlations for Printed Circuit Board (PCB)
some geometry related parameters. These parameters are also displayed in the Variable form, along with the fluid
material parameters. Additional Coefficient is reserved for future use for some P/Thermal correlations.
Figure 65-3 Natural Convection Correlation 701 Forms
The natural convection model defines the convection correlation 701 by using PCONV1 entry, which is referenced by
CONV entry. The following are the highlights of the Nastran input file necessary to model the natural convection
problem with convection correlations:
......
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Figure 65-4 Forced Convection Correlation 507 Forms
The forced convection model uses the coupled advection load to link the fluid stream and surfaces. Instead of a
constant convection coefficient, a convection correlation is used to calculate the convection coefficient at run time.
PCONV1 entry defines the forced convection correlation 507. This entry is referenced by the CHBDYP and PRJCON
cards. The following are the highlights of the Nastran input file necessary to model the forced convection problem
with convection correlations:
......
......
......
......
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PRJCON entry is used to link the two SET3 cards. A convection correlation PID (PCONV1 ID) is referenced if the
HEAT2 option is used. The inlet temperature is defined as a SPC for each inlet node of the fluid stream.
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Defines the properties required to calculate convective heat transfer. It can exist in a simple mode with convection
coefficient defined in the MID or in advanced mode where the H value is calculated using the geometric parameters and
referenced material.
Format
Example
PCONV1 Thermal Convection Calculation Properties
1 2 3 4 5 6 7 8 9 10
PCONV1 PID Corr ID MID Mdot Velocity Length or
Diameter
Flow Cross
Section
+
+ Length
function
type
Flow Cross
Section
type
Mdot f Velocity f Length or
Diameter f
Flow Cross
Section f
+
+ C1 C2 C3 C4 C5 C6 C7 C8 +
+ C9 C10 C11 C12 C13 C14 C15 C16 +
+ C17 C18 C19 C20 C21 C22 C23 C24
1 2 3 4 5 6 7 8 9 10
PCONV1 2 701 2 1.0
Field Contents Type Default
PID Property identification number, referenced by CHBDYP
and/orCONV.
I 0
Corr ID ID of convection type in correlation library. I 0 0
MID Material identification number for convection
calculation.
I 0 0
Mdot Mass flow rate. R 0.0
Mdot f Mass flow rate TABLEDj table ID. I 0 0
Velocity Fluid velocity. R 0 0.0
Velocity f Fluid velocity TABLEDj table ID. I 0 0Length or Diameter Geometry, based on Corr ID. R 0.0 0.0
Length or Diameter f type Geometry function type: I 0 2
1 = time
2 = temperature
Length or Diameter f Geometric function TABLEMj orTABLEDj table ID I 0 0
Flow Cross Section Flow Cross Section. R 0.0 0.0
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Remarks
1. This entry is for RC Network solver only.
2. The PCONV1 entry contains the properties for a CONV and CHDBYP, and can be used for connecting with a
PRJCON. PID must be unique to both the PCONVID in PCONV and the PID in PHBDY. This will be the ID
referenced by CONV, PRJCON, and CHBDYP.
3. MATID must reference a MAT4 fluid material.
4. For Corr. ID and C1 thru C24, please referenceMSC SINDA Users Guide and Library Reference or
P/Thermal Users Guide.
Flow Cross Section f type Flow Cross Section function type I 0 2
1 = time
2 = temperature
Flow Cross Section f Flow Cross Section function TABLEMj orTABLEDj table
ID.
I 0 0
C1 thru C24 Geometric properties based on chosen convection
correlation
R 0.0
Field Contents Type Default
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Specifies a thermal connection between two regions of elements. The connection is automatically determined
geometrically as a projection of the slave region on to the master, and the strength of the connection is calculated based
on the properties given.
HEAT1
Format
Example
HEAT2
Format
Example
HEAT3
Format
PRJCON Thermal RC Element Contact
1 2 3 4 5 6 7 8 9 10
PRJCON BID +
HEAT1 SET3
Master
SET3 Slave h
1 2 3 4 5 6 7 8 9 10
PRJCON 1
HEAT1 1 2 1.2
1 2 3 4 5 6 7 8 9 10
PRJCON BID +
HEAT2 SET3
Master
SET3 Slave PID
1 2 3 4 5 6 7 8 9 10
PRJCON 1
HEAT2 1 2 1001
1 2 3 4 5 6 7 8 9 10
PRJCON BID +
HEAT3 SET3
Master
SET3 Slave F Emis
Master
Emis Slave
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Example
HEAT4
Format
Example
1 2 3 4 5 6 7 8 9 10
PRJCON 1
HEAT3 1 2 1. 0.85 0.5
1 2 3 4 5 6 7 8 9 10
PRJCON BID +
HEAT4 SET3
Master
SET3 Slave F RADC id
Master
RADC id
Slave
1 2 3 4 5 6 7 8 9 10
PRJCON 1
HEAT4 1 2 1. 1001 1002
Field Contents Type Default
BID BCBODY identification number. I 0 Required
HEATx Indicates the start of HEAT elements. C
SET3 Master ID of the master element collection for connection. I 0 Required
SET3 Slave ID of the slave element collection for connection. I 0 Required
h Convection correlation. R 0.0 Required
forHEAT1
PID PID of the property to be used forh value. I 0 Required
forHEAT2
F View factor between parts. 0.0 R
1.0
Required
forHEAT3& HEAT4
Emis Master Emissivity of master collection. R 0.0 Required
forHEAT3
Emis Slave Emissivity of master collection. R 0.0 Required
forHEAT4
RADC id Master RADMID of the material to be used for master emissivity
value.
I 0 Required
RADC id Slave RADMID of the material to be used for slave emissivityvalue.
I 0 Required
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Remarks
1. This HEATx and the later parameters are for RC Network solver only.
2. For HEAT2, PID must refer to a PCONV1 type, and not a PCONV orPCONVM.
3. RC Network Solver uses a projection method to determine the connection (not the nearest neighbor method).
In most of the cases, the projection method is more accurate than the nearest neighbor method.
Results
Figure 65-5 Temperature Contour of PCB with Natural Convection
Figure 65-6 Temperature Contour of PCB with Forced Convection
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Convection Correlations for Printed Circuit Board (PCB)
For now, SimXpert can not display the temperature contour on the fluid stream. Apparently, the cooling effect of the
forced convection is much better than the natural convection.
Modeling TipsIn SimXpert Structural workspace, when you pick the back face of the solid chips for the contact loads, you may need
to hide the PCB surface first, so that the back face of the solid chips can be picked correctly.
The convection correlations are defined in Material and Property/1D Properties / Correlation. If you want to use
constant convection coefficient in the coupled advection loads, please select the 1D Fluid Flow option. If you want to
use convection correlation to calculate the convection coefficient, please pick the Convection Correlation option.
Input File(s)
VideoClick on the image or caption below to view a streaming video of this problem; it lasts approximately 30 minutes and
explains how the steps are performed.
Figure 65-7 Video of the Above Steps
Files Description
QT22_pcb_natural.dat MD Nastran SOL400/RC Network Solver thermal input file
QT25_pcb_forced.dat MD Nastran SOL400/RC Network Solver thermal input file
http://www.mscsoftware.com/training_videos/mdug/ch065/2010/ch065.swfhttp://www.mscsoftware.com/doc/nastran/mdug/input_files/ch065/QT22_pcb_natural.dathttp://www.mscsoftware.com/doc/nastran/mdug/input_files/ch065/QT25_pcb_forced.dathttp://www.mscsoftware.com/training_videos/mdug/ch065/2010/ch065.swfhttp://www.mscsoftware.com/training_videos/mdug/ch065/2010/ch065.swfhttp://www.mscsoftware.com/doc/nastran/mdug/input_files/ch065/QT25_pcb_forced.dathttp://www.mscsoftware.com/doc/nastran/mdug/input_files/ch065/QT22_pcb_natural.dat