11 May, 2017
Electromagnetic shielding, also known as RF shielding, is common in many electronic devices. It is used to protect sensitive components from being affected by electromagnetic interference. Getting shielding right can be important to a product. In February, Apple Stores stopped selling the LG UltraFine 5k in the wake of connection issues due to poor shielding which forced LG into a swift redesign. Electromagnetic interference caused by placing the screen within six feet of a Wi-Fi router resulted in recurring disconnections and, in some cases, MacBook Pro’s freezing.
Shielding can also have implications thermally as it involves enclosing a component in metal shielding (typically steel, copper alloy 770 or aluminium). Thorough consideration needs to be given to how to transfer heat away from components. This can be done using holes (providing they are smaller than the EM wave that needs to be blocked), by using the shield like a heat sink and conducting heat from the component(s) to it via thermal interface material or by some combination of the two.
In previous versions of 6SigmaET it was possible to model EM/RF shielding using a combination of solid obstructions, vents and holes although this was a challenging process. In R11, a dedicated ‘shielding can’ object has been added to simplify and expedite this process.
It is possible to add a shielding can object as the child of a PCB or component. The geometry of a shielding can be defined as either a rectangle or polygon; this allows any shape that isn’t curved to be replicated. Both holes and vents can be added as children of the top/sides of the shielding can to model any holes; hole and vent properties can be varied as part of a parametric study.
The default material is aluminium. However, any material from the vast material library can be attached. If you can’t find the material you desire, there is always the ‘create new’ function which allows a new material to be created by inputting various material properties.
As with other solid objects, you can view the surface temperature plot on each individual side by setting the ‘render style’ to ‘surface temperature’ in ‘display options’. You can also view a multitude of numerical results. Selecting the parent ‘shielding can’ object in the model tree allows you to see the max/min/mean surface and volume temperatures of the objects as a whole in the ‘results’ tab of the property sheet. Selecting individual sides allows you to view the heatfluxes occurring at each side.
By: Matt Evans, Product Engineer