Online proceedings - EDA Publishing Association

VIII. THE CASE FOR MCAD-EMBEDDED EC CFDMCAD-integrated and embedded solutions appeared inthe early 1990s and have been recently reported to be thefastest growing segment of the overall CFD market. Theyhave a smaller share of the EC market than stand-alone tools,but EC remains an important application area.MEs graduating today are almost certain to be proficientusers of 3D MCAD software, which has been available insome high schools for almost a decade [23]. In industryMCAD tools are being used from the concept design stage atthe start of the mechanical design process. New electronicproducts often re-use electronic and mechanical parts fromthe previous generation, so geometry that already exists inthe MCAD system forms a natural starting point. Formechanical reasons, such as interference checking, MCADsystems can already import a full geometric representation ofthe board from the EDA system. CircuitWorks is a bidirectionalIDF and PADS file interface for the SolidWorks3D CAD system for example [24].CFD vendors have shown that it is possible to embed CFDinto MCAD environments and provide useable facilities toinput the additional data etc. needed for the analysis and postprocess the results. SolidWorks Corp. and ParametricTechnology Corp. amongst others, have shown that MCADsuppliers are able to effectively market and sell sophisticatedFEA and CFD software through their direct and reseller saleschannels. All the necessary ingredients are available to adaptMCAD-embedded CFD for the EC market. As such,MCAD-embedded EC CFD offerings are a certainty.The suitability of CAD models for analysis remains apoint of contention [25, 26]. CAD models created formanufacturing typically contain a lot of detail such asthreads, seals, fillets, rounds, etc and have tolerances thatallow assembly, that can cause problems for analysis tools.From an analysis perspective the CAD model is oftenconsidered ‘dirty’ due to its lack of watertightness, whereasit was created for a quite different purpose. CAD ‘cleanup’(and simplification) is a recognized process step in generalpurposeCFD but can be time consuming, so it is tempting totry to keep these simplified copies up to date rather than reexportand clean up the manufacturing CAD model as thedesign progresses. However, this leads to ‘versionitis’ as thecopies become stale, and undetected differences creep in. Ifthe intention is to check the performance of a design beforecommitting to manufacturing it, a better approach is to firstcreate simplified parametric CAD models that are bothappropriate for the analysis and easy to modify. Early in thedesign process a ‘Design for Analysis’ paradigm is needed,with focus shifting to ‘Design for Manufacture’ only afterthe design’s performance is proven to be satisfactory.IX. CONCLUSIONSDesign practices tend to change slowly, driven by costreduction rather than the availability of innovative tools.Stand-alone tools will therefore be around for some time tocome. They work very well, companies have built their useinto their design flows and the MEs that use them have builtrelationships with EEs to obtain the data they need for theanalysis, facilitated by interfacing software. MCAD-24-26 September 2008, Rome, Italyembedded EC CFD effectively exists today [27]. Substantialimprovements are expected as future developments furtheraddress the unique and changing needs of the EC market.MCAD-embedded EC CFD entrenches the responsibility forthermal design within the ME community.Perhaps the greatest hope for the future of electronicsthermal design lies not in MCAD or EDA embeddedproducts as point solutions, but in broader electronic andmechanical co-design. Successful products are defined bythe user experience in terms of aesthetics, ergonomics andfunction. The product’s form is no longer defined by theelectronics it houses. Keypads and touch screens blur thedistinction between casing and electronics and hence thedistinction between the MCAD and EDA worlds. A singlecommon design environment is impractical, but 3Dmodeling in EDA would facilitate bidirectional notificationof relevant design changes and data exchange betweensystems. Progress is already being made in this area, drivenby the need for interference checks, etc. as products continueto miniaturize. As the EDA and MCAD worlds converge thepotential for communication between EC CFD toolsembedded within these design environments increases, andso may be expected to happen over time.What is clear is the importance of thermal design isunlikely to diminish as companies strive to achieve costeffectivedesigns whilst power densities in high performanceapplications continue to increase, driving innovations incooling technology and design practices. Developments inEC CFD software will need to keep pace with theseinnovations to meet the future challenges and opportunitiespresented by this changing market.ACKNOWLEDGMENTI’m grateful to Drs. David Tatchell, Clemens Lasance, IanClark and Robin Bornoff for their comments and suggestionsfor improving this manuscript. 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