Editor’s note: A wind turbine nacelle is a like a hot house in summer months and a terrible place to ask electrical components to work reliably for long periods. To accommodate the harsh temperatures, Mentor Graphics offers the paper titled by the headline above. This brief introduction presents the paper through part of the second tip.
Temperature distribution on the underside of a BGA package showing solder balls
Why is component temperature prediction important? Component temperature prediction is important from a number of points of view. Historically component temperature has been correlated with reliability, with early studies relating field failure rates to component temperature. More recently physics-based reliability prediction has related failure rates of electronic assemblies to the magnitude of temperature change over an operational cycle (power-on, power-off, power-on…), and rate of temperature change, both of which are influenced by steady-state operating temperature. Failures are often attributed to solder joint fatigue. In some applications, like computing, CPU speed is adversely affected by temperature, and in other cases components have to run at very similar temperatures to avoid timing issues. High temperatures can cause operational issues, such as latchup. Whether the intention is to increase reliability, improve performance, or avoid problems during operation, accurate prediction of component temperatures helps thermal designers to achieve their goals.
Reliable, accurate prediction of component temperatures allows designers to understand how close the design values come to the maximum allowable temperature. This white paper discusses how to achieve high fidelity component temperature prediction across the design flow, and to gain increased confidence in the final simulation results.
Tip 1: Model key components explicitly
It is perhaps self-evident that in order to accurately predict a key component’s temperature the component should be modelled explicitly as part of the thermal simulation. However, not all components need to be modelled, and it is often impractical to do so. Small components with a low power density that are not particularly thermally sensitive can be regarded as thermally benign, and do not need to be represented discretely. Heat from these components can be added as a background heat source applied over the whole board, or as a footprint heat source on the board. FloTHERM and FloTHERM PCB provide filtering options to do this automatically in late design when the populated board is imported from the EDA system. Larger components may disrupt the air flow, requiring them to be represented directly as 3D objects. One class of component that can fall into this category are electrolytic capacitors, used for example in power supplies. These are thermally sensitive, with a low maximum allowable temperature.
Large, high-power components and components with a high power density will need to be modelled discretely, as their thermal management and their influence on neighboring components is important to the overall thermal design of the product.
Tip 2: Use good power estimates
As noted above, part of the decision as to whether it is necessary to represent a component directly depends on its power density, which is the component power divided by its footprint area.
Mentor Graphics
www.mentorgraphics.com/thermal
Filed Under: News, Turbines
