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Engineering Edge

Introducing FloTHERM® XT

From concept through to verification for electronic cooling simulation

By Dr. Ian Clark Product Manager, FloTHERM XT

Traditionally the thermal design of electronic assemblies has been left to a relatively late stage in the design processes when much of the electronics and mechanical design is nearing completion. This has led to a lot of late-design rework and often further iterations due to problems found during physical prototyping. Consequently it can mean design costs skyrocket, products are frequently late to market, and there is not enough time for exploring better design approaches and optimization strategies in the upfront design phase where simulation has the most impact.

At Mentor Graphics we therefore felt there was a need to model the complete continuum of the design workflow that supports all phases of electronics cooling design, from concept through to verification and prototyping up to manufacture. In addition, we wanted to interconnect Electronics Design Automation (EDA) and Mechanical Computer Aided Design (MCAD) flows especially targeted at the design engineer as well as thermal specialist, but focused solely on electronics cooling. To do this we therefore harnessed two of our most powerful DNA’s:

The synthesis of these two technologies has yielded FloTHERM XT, a new specialized electronics cooling product supporting design processes from concept through to manufacturing thus extending our FloTHERM product-line capabilities even further.

FloTHERM®, with its world-leading 25 year electronics cooling pedigree, and FloEFD™ as the modern CAD-embedded computational fluid dynamics (CFD) enabling technology. The synthesis of these two technologies has yielded FloTHERM XT, a new specialized electronics cooling product supporting design processes from concept through to manufacturing thus extending our FloTHERM product-line capabilities even further. Its primary, and industry-unique attribute, is its ability to support thermal design requirements from concept through detailed implementation and on to final design verification, whilst retaining data model consistency and cleanly supporting data evolution as mechanical or board layout changes are introduced into the process.

A unique software solution has been developed that delivers interconnectivity between the MCAD and EDA design flows and, in particular, it introduces a powerful and industry-first, auto-update capability as the PCB layout evolves. FloTHERM XT is CAD centric (Figure 1) in design and operation, but has a configurable user interface that supports the needs of both design engineers and thermal specialists who may not require access to all the CAD functionality. The product is focused purely on electronics cooling applications and has been built on the innovative technology within FloTHERM while utilizing the general power and sophistication of FloEFD as the enabling technology for meshing and solving. Secondly, FloTHERM XT includes a module called FloEDA Bridge (Figure 2) where all of the EDA processing steps are semi-automated for the preparation of the PCB model, including component power definition, enabling a complete PCB model to be directly transferred to FloTHERM XT with ease.

Figure 1: FloTHERM XT CAD-centric Interface

Figure 2: FloEDA Bridge Interface

Worked Example: FloTHERM XT thermal design workflow of a brand new product, a wall-mounted internet box

The traditional product creation process follows that a design engineer builds a simple representation of a PCB (1) inside FloTHERM XT ahead of any information being committed to in the EDA system; then using SmartPart technology, quickly constructs a simple enclosure (2) before anything is formally designed in the MCAD system., A thermal simulation (3) is performed at this concept stage to assess the effectiveness of the cooling strategy . In this case the main heat generating component is found to be too hot (4). Adding a heat sink to the component and holes to the enclosure produces a design that works well enough at this stage, so we can quickly get to a ‘concept commit’ – and a decision to turn this into a product (5). The detailed product design then proceeds, and a later stage in the process involves the direct use of a PCB design from EDA. This can be imported into FloTHERM XT, replacing the simpler concept design of the board (6). In addition, the enclosure can be modified directly or replaced by a more precise mechanical CAD model with an aesthetic appearance created by the designer, along with a revised heat sink design to fit into this new housing (7). By this point everything in the early conceptual model has been replaced, and the thermal model has evolved into a representation of the actual detailed design of the product (8). The designs in the EDA and MCAD systems can then be iterated upon and refined to optimize the product’s thermal design, minimizing the cost of the cooling solution, and a final optimized thermal model (9) produced to verify the performance of a “first-time-right” prototype which should typically be the only prototype needed for the therm

Figure 3: Traditional CFD approach to Electronics Cooling MCAD/EDA workflow

If we contrast this to a FloTHERM XT enabled workflow (Figure 4) we see that the “Create Geometry” step is as before. The geometry employed can be imported CAD geometry, created within FloTHERM XT or SmartPart based. The “Assemble Model” step is greatly compressed within FloTHERM XT, though because it can directly work with CAD geometry and so CAD can be exported in the CAD system’s own native format and used directly inside FloTHERM XT. If required, unnecessary detail can be removed by rewinding features of the model within the CAD system.

Similarly, native EDA data can be exported into FloTHERM XT with all of the processing steps incorporated into the new FloEDA Bridge module that simplifies the preparation of complete 3-D models of boards and components. Meshing is also compressed in FloTHERM XT avoiding all the problems associated with a more traditional CFD approach to meshing, This is achieved by using object-based mesh controls and a tried-and-proven Cartesian-based, immersed boundary meshing approach that does not suffer from the mesh quality problems associated with body-fitted meshes. As a result, the solution process is more robust and proceeds very quickly without convergence problems. Report generation in FloTHERM XT is automated, so that recommendations from the simulation can be fed back to the design team in a very short elapsed period.

Figure 4: FloTHERM XT approach to Electronics Cooling MCAD/EDA workflow

FloTHERM XT offers significant advantages over traditional CFD simulation approaches. By starting simulation at the conceptual stage and retaining data and history consistency as the design evolves over time, it results in fewer design iterations to correct late in-process design errors and consequently reduces the time to get new designs to market very significantly. The software has been developed in the recognition that companies vary in terms of the types of personnel required to perform thermal analysis and simulation these days, and is intended to be utilized by both design engineers and thermal specialists. Meaning that what-if-studies and experimental or innovative design changes can be quickly assessed as to their effectiveness, resulting in more competitive products without over-reliance on existing over-burdened thermal experts. It has also been developed with a unique capability for bridging the gap between EDA and MCAD design flows and it takes advantage of Mentor’s leadership in PCB system design tools. In so doing, there is now a direct integration with PCB designs including an auto-update capability which is less error-prone and time consuming when working with board designs generally or with subsequent updates as the board design evolves.

This design flow using FloTHERM XT also introduces best-in-class filtering capabilities for thermally irrelevant devices and supports automatic connectivity to thermal model package libraries. In order to support the broadest possible range of user personas, we have developed intuitive object based meshing capabilities and customizable user interface and model building controls. The outcome being a significant reduction in overall simulation times and the most efficient solution possible for complex, cluttered electronics systems.

By incorporating a solid modeling engine into FloTHERM XT, and with native links to EDA software, it can help companies bring the mechanical and electrical design disciplines closer together through the creation of a 3D model of the product that can be very simple or as detailed as necessary and that is synchronized with the design in the MCAD and EDA systems. Ultimately XT can help companies further compress their design times for electronics cooling, thereby reducing cost and project risk leading to shorter times-to-market, more competitive products and, finally, higher product reliability.

Contact your local Mentor Graphics direct sales channel or reseller for a test drive and see for yourself.

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