CFD Cooling Analysis for
Electronics Systems
Cuong
g Nguyen
g y
Field Application Engineer
cuong@edadirect.com
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Technology Trend - Integrated Circuits
Increasing
g in Heat Dissipation
p

Increasing IC power
dissipation
p
driven byy speed
p
and density
— Boards exceeding 300W
— Systems exceeding 1000’sW
— Smaller form factors driving heat
density
Alcatel-Lucent >300W per blade
Source: Intel
© 2013 Mentor Graphics Corp. Company Confidential
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Electronics Cooling
Application Categories
Fan Sizing
g & Placement
6

Correct fan sizing is required to overcome
system pressure drop and ensure the fan
operates on the correct part of the fan
curve

Local flow features resulting from fan
swirl can have a drastic effect on local
cooling and fan
fan-fan
fan interaction can
impede fan performance

Proximity of electronics to fans
impacts fan performance and
hence system airflow.
© 2010 Mentor Graphics Corp. Company Confidential
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Heatsink Design
g & Selection
7

Select the most suitable heat sink from a
range of vendors standard profiles

Optimize heatsink design for a specific
application to minimize cost, weight and
pressure drop whilst meeting
temperature performance criteria

Minimize wake effects that cause
maldistribution of the downstream air
flow.
© 2010 Mentor Graphics Corp. Company Confidential
www.mentor.com
Vent Sizing
g & Location
8

Vent design and positioning plays a
critical role in optimizing the rate and
uniformity of system-level air flow

Correct venting eliminates recirculation
in the air that leads to hot spots in an
enclosure.
© 2010 Mentor Graphics Corp. Company Confidential
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Air Flow Optimization
p
9

Increasing product complexity is making
air flow optimization a major design
challenge for many classes of equipment

Identify hotspots caused by flow
obstructions such as connectors and
heatsinks

Design plenums to distribute the air

Achieve uniform cooling by avoiding
maldistribution that leads to hot cardslots

Equalize the flow impedance of each card
to balance the system.
© 2010 Mentor Graphics Corp. Company Confidential
www.mentor.com
PCB & Substrate Thermal Design
g
10

Component placement can be checked
for thermal compliance before layout
closure

Assess the effect of buried GND and
PWR planes, and thermal VIAs
before routing

Verify the thermal design after routing
routing,
detailed layer data can be imported to
before manufacture

Thermal verification during design
reduces PCB design re-spins
© 2010 Mentor Graphics Corp. Company Confidential
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PCB Trace Heating
g

Joule heating (
) in traces can
cause additional voltage drop,
drop trace
de-lamination, and even melting of
the dielectric

Import HyperLynx PI detailed net
geometry and DC Drop Joule
heating power dissipation

Subsequent FloTHERM temperature
prediction accounts for:
— Net self heating
— Background heating from actives
— Effects of the PCB environment.
11
© 2010 Mentor Graphics Corp. Company Confidential
www.mentor.com
Joule Heating
g

Coupled electro-thermal and CFD
simulation:
— Joule heating in a circuit breaker
— Natural convection cooling of a
choke.
12
© 2010 Mentor Graphics Corp. Company Confidential
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Case & Junction Temperature
Prediction
13

Detailed and compact thermal
package models enable junction
and case temperature prediction
during design

This ensures the product will meet
specification, whether it’s a power
package
package, LED
LED, microprocessor or
ASIC.
© 2010 Mentor Graphics Corp. Company Confidential
www.mentor.com
Enclosure Thermal Design
g
14

Enclosure design should account for
the environment
environment, including solar loads
and heat from neighbour equipment

Constructional detail, such as card
guides and mounting rails often
ignored in PCB-level simulations
negatively impact air flow causing
localized thermal problems

CFD provides a holistic, system-level
approach to thermal design, ensuring
efficient heat transfer to the ambient

Ensure touch temperature limits are
not exceeded and prevent dust ingress.
© 2010 Mentor Graphics Corp. Company Confidential
www.mentor.com
Package
g Thermal Design
g


Optimizing the complex 3D heat
flows within an IC package
requires detailed thermal
simulation
i l ti
Investigate sensitivity of:
—
—
—
—
—
15
die attach material and thickness
leadframe material
internal heat spreader
fusing
g leads to die pad
p
thermal solder balls and
substrate vias
© 2010 Mentor Graphics Corp. Company Confidential
www.mentor.com
FLOTHERM
© 2013 Mentor Graphics Corp. Company Confidential
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What Makes The Difference? (1/4)
( / )

Effortless Model Preparation and Pre-Processing:
— Library and SmartPart-driven drag & drop model creation
— Intelligent interfacing for design (model) re-use
17
© 2010 Mentor Graphics Corp. Company Confidential
www.mentor.com
What Makes The Difference? (2/4)
( / )

Powerful and robust Cartesian-based gridding capable of
handling Real World geometry:
— Automated, Instant, and controllable
— Delivers solution speed, accuracy and
robustness
b t
18
© 2010 Mentor Graphics Corp. Company Confidential
www.mentor.com
What Makes The Difference? (3/4)
( / )

19
Fast, powerful and accurate automatic design parametric sweep optimization:

Heatsink design

Fan sizing
i i & positioning
ii i

PCB layout
© 2010 Mentor Graphics Corp. Company Confidential
www.mentor.com
What Makes The Difference? (4/4)
( / )

Results visualization and interpretation:
— Photo
Photo-realistic
realistic image creation assists review and communication

Unique post-processing
diagnostics show where
to make design changes:
— Patented Bottleneck &
Shortcut numbers:
20
© 2010 Mentor Graphics Corp. Company Confidential
www.mentor.com
Interfacing
g to ECAD Tools

Direct interface to
—
—
—
—
—

Mentor Graphics Expedition PCB
Mentor Graphics Boardstation
Cadence Allegro/APD
Zukan CR 5000
PADS PCB
Extracting all data required for a
complete PCB the
thermal
mal model
— Board shape, layout, stack-up and
detailed description of metallic
d
distribution
b

21
Import Power List
© 2010 Mentor Graphics Corp. Company Confidential
www.mentor.com
Interfacing
g to MCAD Tools – FloMCAD Bridge
g

Direct interface to Import
— IGES, STL, SAT, STEP, Pro/E,
— Catia V4, DxF, SolidWorks

Simplify MCAD structures
— Remove small Holes
Holes, non
non-planar
planar
faces, small humps, flatten small
drafts, etc.. to optimize Thermal
simulation times
— User-definable Voxelization settings
to convert MCAD Part of Body to
ssmaller
a e cubo
cuboids
ds
22
© 2010 Mentor Graphics Corp. Company Confidential
www.mentor.com
FloTHERM Key
y Technologies
g
Summary
y

Models built quickly using

Fast and Robust Solver

Powerful 3D Airflow Visualization
Parametric Design Optimization

23
23
— Predefined objects
(S
(SmartParts)
P
) such
h as
PCBs or Fans
— Existing Libraries
— User built libraries saved
from previous projects
— CAD/ECAD Import
— H
Heatsink
t i k design,
d i
componentt
placement, fan failure, baffles,
etc.
Optimized heatsink
dropped component
temperature by 6ºC
© 2010 Mentor Graphics Corp. Company Confidential
www.mentor.com
Our History of CFD Industry
Innovation & Leadership
p



Over the last 25+ years has pioneered new
markets for thermal analysis
y in electronics for
Analysts, ME, and Designers, as well as worldleading MultiCAD-embedded CFD technologies
with unparalleled ease-of-use
Changed the way electronics and manufactured
products are designed and improved many
manufacturing process workflows
Concentrate mesh where needed
CFD innovations:
—
—
—
—
—
24
Localized grids & Embedded-Conduction Solvers
SmartParts & Compact
p
Thermal Models of Packages
g
First with Design of Experiments & Automated Optimization
Unique 2-Layer k-epsilon turbulence model
Shortcut and Bottleneck numbers for electronics cooling
postprocessing
© 2010 Mentor Graphics Corp. Company Confidential
www.mentor.com
Bn
Mentor Graphics CFD applications
in the Electronics Industry
y
25
© 2010 Mentor Graphics Corp. Company Confidential
www.mentor.com
Electronics CFD Design/Thermal
Management
g /
g
IC Package
Design
g
26
PCB
Design
g
PCB/System
Design
g
System
g
Design
© 2010 Mentor Graphics Corp. Company Confidential
www.mentor.com
FloTHERM
Demo
27
© 2010 Mentor Graphics Corp. Company Confidential
www.mentor.com
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