What Is Thermally Conductive Insulators

Thermal management is one of the top concerns when designing advanced 3D integrated circuit technologies. To ensure the highest levels of performance and reliability, manufacturers must ensure that chips, packages, underlying PCBs, and other components do not overheat or otherwise suffer from degradation due to thermal expansion. This can be challenging, especially when the different components are made from a variety of materials that have varying thermal properties.

The thermal properties of a material are dictated by its composition and microstructure. For example, metals have high thermal conductivity while ceramics and polymers have low thermal conductivity. In addition, The Power of Thermally Conductive Insulators behavior of a material is also influenced by its chemical and physical properties. The thermal conductivity of a material decreases with increasing temperature due to the adiabatic compression effect, which results in the formation of crystal lattice defects that scatter quantized vibrations known as phonons.

To minimize the energy loss caused by these defects, insulating materials must have low thermal conductivity. This is achieved by lowering the thermal conductivity of a material by filling it with low-conducting compounds or adding surface treatments to improve its thermal properties.

There are four main types of thermal insulation materials: granular, fibrous, cellular, and reflective. Granular materials, such as calcium silicate or rock wool, have air entrained in the matrix. Fibrous materials, like mineral wool, cellulose fibers, or reed mats, consist of small fibers that are separated from each other by air gaps. Cellular materials, such as foamed plastics or cellular glass, contain small air pockets that are completely or partially separated from each other by other air pockets. Reflective insulation materials have a layer of low-emissivity material, such as aluminum foil or stainless steel sheeting.

Although a number of factors influence the thermal conductivity of a material, the most important characteristic is its density. For this reason, the thermal conductivity of a material can be estimated by its density and temperature, with higher densities having lower thermal conductivities. Typical values for various insulating materials are given in Table 10.1.

In many applications, the insulating property of a material depends not only on its thermal conductivity but also on its specific heat, which is a function of its temperature. This is particularly true in a building environment where the temperature of the air and outdoor temperatures vary over time.

In order to reduce the energy loss associated with the movement of heat and moisture within a building, it is necessary to select an insulating material that has both low thermal conductivity and high specific heat. Unfilled polymer adhesives are inherently thermal insulators, but they can be improved by formulating them with fillers that are either metallic or inorganic. Common fillers include silver, gold, and nickel. Adding metal to the resin increases its thermal conductivity but also renders it electrically conductive, which is not suitable for applications requiring electrical insulation or isolation. Silica aerogels and boron nitride are nonconductive inorganic fillers that are useful as thermal insulation.