Honeycomb ventilation for the data centre

And that cooling comes in many forms — air cooling, thermal interface materials (TIMs) and liquid cooling, to name a few. Electronics also require shielding from electromagnetic interference (EMI) for optimum performance. In the data centre, one pervasive approach to ensuring both conditions are met is the use of honeycomb vents. You've undoubtedly seen these familiar structures as part of electronic housings of all types.

So, why this design? The honeycomb shape acts as a wave guide, using attenuation and reflection to shield electromagnetic radiation and control the frequency range. The honeycomb cores, available in numerous designs, can deliver on various EMI performance requirements. In data centres, where good airflow is critical to server, router and switch functionality, honeycomb venting is everywhere. Generally, the honeycomb core is attached to an aluminium or steel frame and then placed in a housing opening to allow airflow and cooling while providing EMI protection. In addition to the core's functionality, the method of attaching the vent to the frame is also an essential aspect of its performance.

The vent cores are often connected to metal frames with high-performance electrically conductive adhesives. While it may seem a minor point, optimising the adhesive material is central to the integrity of the honeycomb venting, its functionality and its overall cost. Certain chemistries like silicone may not deliver the adhesion required. Other challenges with material viscosity, conductive fillers and processability are also considerations.

Traditional lower-viscosity materials tend to flow out of the interface, which can cause aesthetic issues and block vent openings, impeding airflow and, therefore, limiting cooling effectiveness. In addition, the silver fillers generally used for electrically conductive adhesives can be expensive and have the potential to dramatically increase adhesive cost depending on the filler loading. Finally, to deliver the most effective EMI shield for the entire vent assembly, the adhesive bead must be intact -— with no voids or skips — to provide a cohesive barrier to any interference. In modern data centres, every element of functionality is essential to deliver the data processing speeds and volumes required for today's digitised society.

Balancing performance, cost and lifetime is the ultimate sweet spot for any product. The same holds true for advanced materials employed in the data centre. In the case of honeycomb core-to-vent frame attachment, it has been revealed that adhesives with highly stable, unique filler technology can lower costs significantly compared to a conventional low-viscosity, silver-filled material. Henkel has had recent success with its epoxy-based EMI adhesive, LOCTITE^® ABLESTIK CE 3520-3, which uses a filler alternative to silver but has proven to deliver EMI shielding effectiveness aligned with data centre requirements.

In addition to optimised conductivity/volume resistivity properties, and along with the cohesiveness of the dispensed material with no voids or gaps, LOCTITE^® ABLESTIK CE 3520-3 provides a solid EMI barrier in combination with the honeycomb core so that the entire vent assembly is shielded. With a gel-like, high-viscosity consistency, the Henkel material has excellent adhesion and positional stability once dispensed. This is crucial to the honeycomb core fixturing before cure and to the assembly's long-term integrity. Depending on the location of the dispensed bead of EMI adhesive, the viscosity of the formulation is key to ensuring there is no potential for migration or blockage of airflow openings. LOCTITE^® ABLESTIK CE 3520-3 has demonstrated these characteristics, in addition to good dispensing performance for high-volume production.

With digital data underpinning most of our daily existence and volumes continuing to explode, optimising server, router and switch performance at every opportunity is essential. Henkel's honeycomb-core EMI adhesive delivers solid EMI protection, lower cost and robust adhesion, among other benefits. This solution helps secure cost competitiveness and protected airflow in state-of-the-art data centres.