Latest Tools for Thermal Analysis of Electronics by alq49994



Latest Tools for Thermal
Analysis of Electronics
A wide range of ANSYS software is available to study cooling
in ICs, components, PCBs and complete electronics systems.
By David Rosato            Rajesh Nair
Product Manager            Manager, ICE Division
ANSYS, Inc.                Fluent Inc.

In the rapidly changing electronics industry, designers
are cramming ever-increasing capabilities into smaller
and smaller products such as cell phones, PDAs and
laptops. Moreover, electronics is being integrated into
an expanding variety of formerly all-mechanical
products. This pushes the limits of air cooling to
protect sensitive circuitry from its number-one enemy:
excessive heat build-up. In these demanding applica-
tions, there is little time for mechanical, thermal and
electrical simulation in launching quality electronic
products to meet narrow windows of market
opportunity — and there is absolutely no room for
failure. In this fast-paced, high-stakes industry, ANSYS
tools are used in meeting these challenges for thermal
analysis relating to chips, components, printed circuits
and complete systems.
                                                             Temperatures of a four-BGA package-on-package were
                                                             determined by ANSYS PTD.
Thermal Analysis
The electronics industry can be segmented into four
general areas: chip, component, printed circuit board
(PCB) and system. The chip is the part of the package
that has active circuitry on it — and where the majority   ANSYS PTD has direct interfaces to Cadence® APD
of the heat is generated. Chips typically are made of      and Sigrity® UPD, the leading ECAD tools used to
silicon, gallium arsenide (GaAs) or gallium nitride.       design these components. Every part of the design is
Active features on a chip can be smaller than a micron.    imported from these tools, leaving little to be defined
     Many companies use the special features of            by the user. Three-dimensional models usually can be
ANSYS TAS software to thermally simulate GaAs              automatically generated and solved in a few minutes.
power amplifiers. This feature allows RF design                  ANSYS PTD tools can simulate almost any
engineers to easily define the geometry. The full chip     package style including BGA, multi-chip, leaded and
model is generated automatically with details to the       leadless. Package-on-package (PoP)- and package-
sub-micron level. Typical solve time is less than          in-package (PiP)-type devices can also be simulated.
a minute.                                                  These devices integrate multiple individual parts into a
                                                           single package. Complex geometry such as lead-
Simulating Electronic Components                           frames can be imported through DXF or DWG MCAD
To thermally simulate electronic components, ANSYS         files. The component can be placed on a JEDEC
offers ANSYS PTD, or Package Thermal Designer,             board, and standard thermal characterization tests
software. For ball grid array (BGA)-type packages,         can be simulated accurately. With the easy-to-use                                                                 ANSYS Solutions | Volume 7, Issue 5 2006

     environment, direct ECAD interfaces, fast geometry         tools like ProEngineer ® or ECAD tools (Cadence,
     processing and model solving, simulations that once        Mentor ®) if necessary. Predefined object models like
     took days can now be done in minutes.                      heat sinks, integrated circuit packages, PCBs, fans
                                                                and blowers allow users to rapidly build a system
     Studying Printed Circuits                                  prototype even before designs are committed to CAD.
     At the printed circuit board level, ANSYS offers                A variety of advanced physical models —
     ANSYS TASPCB technology. Like ANSYS PTD,                   including those for turbulence, flow and temperature
     ANSYS TASPCB has interfaces with the ECAD tools            resistance modeling, radiation, shell conduction, and
     used to design them. ANSYS TASPCB software                 heat exchanger models — make Icepak software the
     imports every layer, trace, plane and via in the board.    state of the art in thermal modeling. Network modeling
     As components get smaller and their power dissipa-         options allow the user to optionally represent complex
     tion increases, the local thermal behavior of the PCB      IC packages using simple RC-type network models.
     to which they are attached becomes more important.         Automated meshing algorithms take user input in
     A PCB can have as many as 20 to 40 layers with tens        the form of local (object-based) and global sizes
     of thousands of traces and vias. Each of these is a        and generate a high-quality mesh. Assembly-level
     local heat transfer path.                                  meshing allows the user to include minute details in a
           ANSYS TASPCB software accounts auto-                 system-level model yet keep the model sizes small
     matically for every one of them in the 3-D model of the    and solution times short. The backend solver, provided
     board that is automatically generated. As power            by Fluent, is robust and fast.
     dissipation on the board increases and operating
     voltages decrease, the current going through the           Evaluating IC Package Designs
     planes and traces increases. This causes a voltage         Icemax software is an advanced parasitic extraction
     drop in the traces and planes that turns into heat.        tool for analyzing complex IC package designs.
     ANSYS TASPCB can calculate this voltage drop and           Increasing circuit and transistor density has led to
     automatically make the dissipated heat part of the         problems of cross-talk and signal integrity that cannot
     overall thermal solution. The solution also accounts for   be easily analyzed using design rules or correlations at
     how the electrical resistance of copper significantly      the package level.
     changes with temperature by increasing the heat                  The Icemax modeling interface is trivially simple.
     generated with increased temperature.                      It eliminates the major bottleneck in the model-
           The 3-D models generated by ANSYS TAS,               building process by being compatible with all EDA
     ANSYS TASPCB and ANSYS PTD software can                    platforms that are used across the IC design industry.
     be exported to ANSYS Mechanical software and the           A full three-dimensional model is generated in a matter
     ANSYS Workbench environment. Temperature results           of minutes from industry-standard layout data using
     are included, permitting thermal–stress simulation.
     A simplified version of the ANSYS TASPCB board with
     components and power can be exported to Icepak
     software, the electronics cooling design tools that are
     now part of the ANSYS suite from the company’s
     recent acquisition of Fluent Inc. The component
     geometry from ANSYS PTD also can be exported to
     Icepak for system-level analysis.

     System-Level Design and Optimization
     Icepak software is interactive, object-based thermal
     management software for performing thermal design
     and optimization at the system level. The technology’s
     model-building features include search and selection
     from libraries of pre-defined parts and components,
     placement and sizing using the mouse, and use of
     complex geometries including direct import from CAD

                                                                  Temperature and air flow in this server system with blowers
                                                                  and heat sinks were predicted by Icepak software.                                                                  ANSYS Solutions | Volume 7, Issue 5 2006

                                                                         because of stringent regulations regarding electro-
                                                                         magnetic emission and specific absorption rate (SAR).
                                                                         Issues related to cross-talk are experienced when EM
                                                                         radiation from one device interferes with the operation
                                                                         of another device. Additionally, use of cooling devices
                                                                         like heat sinks in order to solve thermal problems at
                                                                         the packaging level result in these devices behaving
                                                                         like antennae, thereby compounding the problem of
                                                                         minimizing EM radiation. Furthermore, a thermal solu-
                                                                         tion for a system usually tries to maximize the flow
                                                                         through the system by ensuring larger intakes and
                                                                         exhausts from the system; however, this works at
                                                                         cross-purposes with an EM system design that tries to
                                                                         minimize radiation from the system by closing off or
                                                                         minimizing the size of these openings.
                                                                               Icewave technology shares its CAD import
                                                                         capabilities with Icepak, thereby allowing import from
Icemax was used to extract SPICE models for this                         a variety of CAD tools and formats. Model-building
multi-chip module.
                                                                         capabilities are similar to those of Icepak, allowing
                                                                         users to build relevant parts like heat sinks,
                                                                         enclosures, vents, sources and lumped elements
                                                                         quickly and efficiently without having to start with
                                                                         basic entities. Mesh generation is fully automated.
               super-fast geometry processing engines. Model-            Advanced material models such as dispersive
               building tasks then get reduced to a simple sequence      dielectrics and frequency-dependent skin effects on
               of events that include importing layout information;      conductors also are available. s
               assigning material properties; and including additional
               information like wire bonds, solder bumps and solder
               balls. This is performed through a wizard-style inter-
               face that leads the user through the steps required to
               complete the 3-D package geometry. The user merely
               needs to specify the operating frequency, the net (or
               the entire package) to be simulated and the number of
               neighbors to be included in the simulation.
                    Package designers, engineers and researchers
               involved in IC package design can easily generate
               detailed, reliable RLC information for the entire
               package in a matter of minutes. Output can be
               generated in matrix, SPICE or IBIS formats for
               signal integrity, power integrity and simultaneous
               switching noise analysis. The output is ready for
               circuit simulation.

               Full Wave Simulation for EMC and EMI
               Icewave software is a time-domain 3-D full wave
               simulation tool for EMC and EMI analysis of electronic
               products. Icewave uses a robust finite-difference time
               domain (FDTD) field solver to solve complex real-world
               electromagnetic (EM) radiation and propagation
               problems. EM radiation problems have become
               increasingly important for the average consumer

                                                                           Icewave was used in determining the electric field
                                                                           in this electronic enclosure.

                                                                      ANSYS Solutions | Volume 7, Issue 5 2006

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