Robust, cost-effective heat management must cater to differing applications and user requirements.

When it comes to addressing the thermal management demands of today’s advanced electronics devices, there is no “one size fits all” solution. Different applications and user preferences dictate the material type and performance to be selected. One thing is universal, however: effective thermal management – especially at the TIM2 level – is more critical than ever, as devices shrink in footprint and increase in functionality and, therefore, keep getting hotter. Robust, cost-effective heat management must also cater to differing applications and user requirements, and so a complete range of materials approaches for differing specifications is required.

Traditional thermal greases. Arguably, the most well-known thermal management materials are thermal greases. Well-liked for their good wetting ability, greases have historically been the material of choice for certain thermal applications. The lower processing costs of greases have also been part of the appeal, though they do have some performance challenges – such as “pump out” or migration -- over the long-term. While phase change liquids have to go through a step whereby they require a phase change transition to achieve desired performance, greases are functional as soon as they are applied and offer a viable alternative for manufacturers who want to avoid the extra processing requirements associated with phase change materials. Though phase change products generally offer better long-term reliability because they don’t pump out over time like greases, there are extra process steps required.

Thermal interface pads. There are applications and processes where pads are still an appropriate choice and are often used in place of traditional thermal grease. There are pads designed for applications that dictate extremely high reliability and are not bound by requirements for thermal performance. Examples where these materials have shown their effectiveness include base stations and power electronics. When electrical isolation is required, thermal interface pads that provide good thermal performance, cut-through resistance and dielectric strength should be utilized. Both of these interface pad types are excellent alternatives to thermal greases which, as mentioned, may suffer from reliability problems over time due to material migration.

Printable and dispensable phase change pastes. As an alternative to traditional phase change pads or films, liquid medium products that offer similar performance characteristics are enabling more process flexibility. The new materials, which are dispensable or printable, are phase change materials in liquid form that offer many of the advantages of thermal greases in terms of usability and throughput without the challenges that are inherent with greases. Both formats are pastes when applied and, over time, the materials dry and form a phase change pad. The reliability and performance of the materials are consistent with film phase change materials but, because they are liquids, thickness can be adjusted depending on the requirement. Films come in a variety of thicknesses, but extremely thin films are difficult to manufacture and often do not release cleanly from the liner. As the liquid materials can be fully automated, throughput is improved and adaptable to current equipment, permitting manufacturers to use standard dispensing or screen printing systems.

Thermal adhesives. To address emerging requirements for device size and weight and improved processability, many thermal management experts are turning to thermal adhesives as their preferred TIM2 materials. Not only do these products deliver the thermal performance required but, because of the permanent bond these materials provide, they eliminate the need for fastening devices such as screws and clips. Thermal adhesives in both paste and film formats enable manufacturing flexibility while facilitating the manufacture of smaller, lighter products. When thermal specialists want the advantages of an adhesive but require consistent thicknesses, the ability to bond large devices with complex patterns, and minimized voids, adhesive films are the obvious solution.

Clearly, there are no shortage of effective, application-specific thermal solutions from which to choose and each should be carefully evaluated in terms of cost, value, processability, ease-of-use and, of course, performance to specified requirements. I can say with relative certainty that we won’t see devices getting any bigger, making effective thermal management a huge factor in the reliability of next-generation devices.

Jie Bai is a chemist at Henkel Electronics Group (henkel.com); jie.bai@us.henkel.com.

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