TIMs are used to enhance heat dissipation between the components in an electronic device. They are typically inserted between a heat-producing component and the metal housing enclosing it.
There are many different types of TIM available. They range from thermally conductive gap fillers to more rigid materials like thermal grease and pads.
Dielectric Pads
Several studies have shown that dielectric pads improve the signal-to-noise ratio of MRI scans by reducing local shading1,4 and inhomogeneous RF distributions5-6. However, pad degradation over time and a large amount of water needed for their MR-invisibility limit the application of these devices in clinical imaging.
To address these issues, a new generation of RF-dielectric pads was developed based on barium titanate powder mixed with water. This material enables the achievement of high relative permittivity values, and it allows for a reduction of pads size and thickness.
Although these artificial dielectric slabs improve the B1+ field magnitude over the whole phantom, they are still much larger than the original pads and have limited flexibility. Therefore, it is important to optimize the geometry of the pads and the artificial dielectric slab to obtain better performance. Currently, researchers are looking into using silicon carbide as a replacement for the traditional water-based perovsite pads. This would make the pads invisible in MRI and prolong their performance.
Adhesive Pads
A logical follow-up to gap fillers, thermal pads are soft, flexible, and thermally conductive. They are designed to conform to uneven rough mating surfaces to reduce air gaps during assembly and help displace heat from the components. They are available in a variety of fabricated films and wet dispensed products to fit your needs.
Some are designed to be molded to the component and replace external attachment hardware, reducing cost and reducing the chance of misalignment and failure due to improperly clamped hardware. Others are filled with pressure sensitive adhesives (PSAs) coated on a support material such as polyimide film or a fiberglass mat that, when slight pressure is applied, stick to the surface by contact.
Gels are a newer option and operate much like grease, but are cured to a partially cross-linked structure to reduce the possibility of pump-out issues. They provide a more stable performance than greases and offer the same level of long-term reliability.
Phase Change Materials
A phase change material (PCM) is solid at room temperature and changes to a liquid at its transition temperature. Once it reaches this temperature, the material absorbs and releases heat energy efficiently.
PCMs are ideal for storing thermal energy as they have high latent heat capacities. They can be re-charged by cooling them to crystallise back into a solid state and used thousands of times for sustainable energy storage.
When applied as a thermal interface, the thermal performance of a PCM can be improved by combining it with a TC filler in a TIM matrix. This allows the product to conform to the microscopic irregularities of the components it contacts, resulting in minimal thermal contact resistance and preventing migration or pump-out.
LOCTITE Bergquist’s dispensable and printable phase change thermal compounds are easy to handle in your manufacturing processes. They provide better long-term thermal stability than grease and also offer lower volatile content, enabling them to avoid pump-out during thermal shock testing.
Solder
TIMs are used to improve the transfer of heat from electronic components to the cooling mechanism, preventing electronics from reaching dangerous temperatures. They are generally placed between the component and the heat sink.
Typical liquid TIMs consist of various liquid polymers, pads that are made from wax, aluminum, graphite, or silicone, tapes, gels and solders. They all have different characteristics that impact their performance. Some require a significant amount of force to create a strong joint, while others have low thermal conductivity.
Bergquist SIL PAD Q-type materials are ideal for those applications where maximum heat transfer is required, but electrical isolation is not necessary. They offer a much easier application that is cleaner and more cost effective than greases and other messy products. They are also formulated for easy dispensing and placement. This is particularly beneficial in automated assembly lines. They are available in a variety of thicknesses and with different metal fillers to meet specific requirements.Thermal Interface Material