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3 Electrothermal Mechanical Stress Reference Design Flow for Printed Circuit Boards and Electronic Packages // ANSYS Mechanical Enterprise Mechanical solves complex structural engineering problems. In our problem, Mechanical calculates the thermal stress, deformation and elastic strain of the board. ANSYS SpaceClaim Direct Modeler SpaceClaim Direct Modeler (SCDM) is a 3-D MCAD modeling software package used to create, edit and repair geometry. SCDM is included with the ANSYS Mechanical Enterprise product. The PCB for our problem is imported into SCDM with the corresponding heat sinks. Essentially, SCDM acts as a bridge between ECAD, SIwave and Mechanical. ANSYS Workbench Workbench is a platform that integrates applications using common and compatible data models for multiphysics problems. In the multiphysics problem of our PCB, Workbench helps to link thermal simulation results f rom Icepak to Mechanical. Also, ECAD data is mapped onto the board geometry in Mechanical through Workbench. The reference design flow is described in the following sections. / Stage 1: Translate ECAD Geometry to ANSYS The first stage of our multiphysics simulation is to translate the ECAD geometries f rom third party vendors into ANSYS tools, particularly, SIwave. ECAD geometries for packages and PCBs are created in various layout tools. ANSYS actively supports ECAD translations f rom the vendors shown in Figure 3. From these third party layout tools, complete designs with arbitrary power and ground planes, vias, signal traces, wirebonds and circuit elements can be translated with unprecedented accuracy and speed into SIwave. Depending upon the type of layout tool, there are different options available for easy translation of ECAD geometries to SIwave. ANSYS products offer a lot of flexibility in this regard. For example, you can very quickly generate an ANSYS equivalent model f rom Cadence SPB by "dragging & dropping" the associated file (.brd, .mcm or .sip) into the SIwave interface, assuming Cadence is installed on the same machine as SIwave. Alternatively, if you install Layout Integrations for ECAD, which is a separate installation option within the ANSYS Electromagnetics Suite download, it adds ANSYS menu items within Cadence SPB products. Through this ANSYS menu, you can create .anf and .cmp files or launch HFSS and SIwave directly f rom within the Cadence environment. In this paper we illustrate the analysis flow using a printed circuit board that was originally created in Altium Designer. Altium Designer exports the design in ODB++ format. This ODB++ directory is imported into ANSYS SIwave. Design automation features in SIwave let you import ECAD files f rom many popular layout tools as shown in Figure 3. The translator binaries that come with the ANSYS EM Suite installation extract a complete list of nets f rom the ODB++ database easily. The full board with its layers, material properties, components, VRMs, ICs (microprocessors, FPGA, DDR2 RAM), vias and traces are all accurately translated to SIwave. Figure 4 shows the virtual prototype of the PCB in Altium Designer and the accurately translated version of the same prototype in ANSYS SIwave. Reference designators are labeled for your ready reference. In its physical form, this printed circuit board is used in electronic devices for multimedia applications. Note: To learn how to translate ECAD geometries to ANSYS watch the YouTube Videos available under the playlist ANSYS Electronics: Translating ECAD Databases into ANSYS. Figure 3. Supported ECAD translations Figure 4. PCB translated from Altium Designer to ANSYS SIwave

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