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Design007-Oct2020

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68 DESIGN007 MAGAZINE I OCTOBER 2020 the greatly reduced effects of pump out, mak- ing PCMs an excellent choice for applications that undergo widely varying temperatures. The application methods of PCMs for high volume production mean that most can be utilised in existing production processes with minimal—if any—changes, whilst also allow- ing for easy rework, offering many of the same benefits of traditional thermal pastes. PCMs offer greater long-term stability compared with thermal greases as they are better suited to thermally challenging applications where product life expectancy and reliability may be critical, such as automotive/aerospace elec- tronics or remotely-located wind power invert- ers. Traditional thermal pastes/greases will continue to be a popular choice, although for some applications, especially those requiring greater long-term stability, a PCM is likely to win over the crowd. 2. What are the options for the automated application of thermal management products? Automated applications involve the use of specialist equipment that typically consists of an applicator head where the material is fed to the applicator via dispensing equipment. Due to the high viscosities of the thermal manage- ment materials, the dispensing equipment is usually a follower-plate system that connects to the thermal paste container as supplied. In addition, automated stencil and screen appli- cators are widely used. For example, we work with a number of local and international equip- ment manufacturers. 3. When would I feasibly require an encapsulation resin with high thermal conductivity? Electronic components and devices will pro- duce varying levels of heat during their opera- tion. Where significant amounts of heat are generated, intervention in the form of ther- mal management may be required to prolong working life and increase reliability. For cer- tain types of applications, it may be beneficial to encapsulate the whole device in a heatsink enclosure using a thermally conductive encap- sulation resin. This method offers both heat dissipation and protection from the surround- ing environment, such as high humidity or corrosive conditions. Once again, it is important to ensure that no air inclusions occur during the potting opera- tion, as these will interfere with heat transfer to the metal case. Mineral fillers used in some resins systems have a higher thermal conduc- tivity than the resin base, so filled resins are better than unfilled resins, as far as thermal control is concerned. The higher the filler level, the higher the thermal conductivity. However, higher filler levels will lead to higher viscosity and a greater possibility of air inclusions in the potting. 4. What options are available for more environmentally friendly thermal management products? In recent years, we have seen demand increase for more environmentally friendly products across all our product groups. How- ever, within the thermal management range, we have developed a high-performance ther- mal management paste that is entirely free from zinc oxide (ZnO). The non-silicone heat transfer compound is recommended for applications where the use of zinc oxide is restricted; for instance, in the marine industry, ZnO is a pollutant, and silicones are prohibited in places like offshore utilities. HTCX_ZF is a highly stable, non-curing paste that enables simple and efficient rework of components (if needed) and is recommended where efficient and reliable thermal coupling of electrical and electronic components is required, as well as between any surface where thermal conductiv- ity and heat dissipation is important. 5. What is the importance of a bulk thermal conductivity value? The initial selection of suitable TIMs for testing is often conducted based on high bulk thermal conductivity, indicating the efficiency

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