Honeycomb air vent panels are used to help cool electronics with airflow and while maintaining electromagnetic interference (EM) shielding. Recently, our team of experts held a webinar on EMI shielding air vent panels, now available on-demand. This blog post will highlight some topics discussed in the webinar.
The most important factors of honeycomb air vent panels are shielding effectiveness and airflow, which are both directly related to the cell size. Both factors have a large impact on the size, material, and design of the vent panel. While you will need to balance the tradeoffs between airflow and EMI shielding needs, you should also ask yourself if air particle filtration is needed as well.
The thickness of the air vent panel also has an impact on both the airflow and the shielding effectiveness. If the cell size were kept the same, the lower the thickness of the vent panel, the greater the allowable airflow.
The decreased airflow is caused by the surface friction of the air flowing through the honeycomb cells. However, reducing the vent thickness will also reduce the attenuation capabilities of the honeycomb. Again, the key is to try and find the middle ground between good air-flow (less pressure drop) and shielding effectiveness.
Aluminum honeycomb is made from thin ribbons of bent aluminum that are adhered together using a non-conductive adhesive. The points at which the ribbons come together are known as nodes and can cause EMI shielding leakage. With single-layer honeycomb vents, there is actual directional EMI shielding. This is known as the polarization principle.
It’s also important to note that this is only the case with aluminum honeycomb vents because, with brass and steel vent construction, the nodes are welded together and therefore are inherently conductive.
One way to reduce the directionality of attenuation in vent panels is by using what Parker Chomerics calls an OMNI CELL construction. This means that the second layer of aluminum honeycomb is stacked on top of the first at a 90-degree angle.
The directionality is offset by the second layer and the new panel should have nearly equal attenuation in both directions. One small drawback is that the two layers will reduce airflow across the new vent panel.
OMNl-CELL can be a great option in many cases, but for applications where an OMNI-CELL construction will not work because of space or high attenuation needs, you can achieve the same effect by plating the honeycomb. The plating of aluminum honeycomb will bridge the non-conductive node, and eliminate the directional effect of the honeycomb.
It’s also a much more thorough coverage, which results in better shielding. Platings will protect the vents from corrosion and standard wear and tear. Electroless nickel is one of the most common plating options, as is a chromate conversion coating.
And lastly, EMI vents can be coated with aesthetic paints to match any enclosure design. This includes CARC paints and common military color patterns.
Want to learn more about specific applications and get more detail? Watch our on-demand webinar EMI Shielding Honeycomb Air Vent Panels: Application and Design 101 now!
This blog was contributed by Jarrod Cohen, marketing communications manager, Parker Chomerics.