Issue link: https://iconnect007.uberflip.com/i/1285883
SEPTEMBER 2020 I DESIGN007 MAGAZINE 61 ing aerodynamic type applications when dealing with a small number of discrete objects, we recognized that electronic systems are built from many hundreds, if not thousands of objects. In Simcenter Flotherm objects carry information about the mesh refinement they need, so they can be moved around in the model or stored in the software's library infra- structure and used again in another model, or provided from a supplier to a customer to use at the next packag- ing level. In Simcenter Flotherm, the meshing is instantaneous. The time overhead of creating a body-fitted mesh was prohibitive back then, and there is additional overhead in terms of computing time per mesh cell. That may be warranted for aerodynamic-type challenges, where the only thing that matters is the fidelity of the CFD, but not for electronics cooling. The reason is that the focus is not on predicting lift and drag, which depend entirely on the airflow, but pre- dicting temperature. A large proportion of the temperature rise we are attempting to predict occurs within the solid structures, from the die outward, and not in the air, so the need for sophistication principally lies in how the com- ponents and boards are modeled from a ther- mal perspective. That sent us down the road of using a Cartesian-based mesh approach, and we haven't looked back. Other tools are now rediscovering the value of Cartesian cell topologies. Shaughnessy: We're starting to see more com- panies in the PCB community paying attention to thermal management now. What segments are driving this trend? Parry: With device miniaturization has come reduced switching voltages to reduce power consumption. While the power consumption per transistor has been reduced, the number of transistors has exploded, so the power dis- sipation per unit area at the board level has increased. That means that the current run- ning through power and ground planes, and power delivery nets, has increased to the point where the current flowing through the copper heats it up, so we now need to consider the board itself as a heat source, not just the active components. The reason this is affecting the PCB design community is that the temperature rise in the copper changes its electrical proper- ties, so we are starting to see situations where, to close the PCB design, that has to be taken into account. The PCB design flow needs to be made temperature aware through tools like Mentor's HyperLynx PI and its interfacing with Flotherm. Electronics systems today are a long way from being simple boxes with boards and lots of space. Even data center servers are densely packed, with power densities now at a level where the main CPUs may be liquid cooled using chiller blocks, or the boards fully liq- uid cooled. Some of the biggest challenges are being faced by companies in industries that fall outside of traditional electronics, such as auto- motive. This is everything from electric vehicle powertrains, where power electronics are used as an inverter/converter between the motors and the battery, to ever more advanced driver assist systems, including head-up displays that the driver directly interacts with and thorough to sensor fusion boxes used to process sen- sor data in autonomous vehicles, where the amounts of data being processed are huge, and processing dissipates hundreds of watts. 5G is a big challenge both for mobile devices and wearables and for the networking infra- structure to support it. With 5G, we are seeing Minnowmax MAX board with fansink.