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October, 2017


A Hot Spot Solution: Dispensing Thermally Conductive Pastes


By Karin Prechtner, Marketing, Scheugenpflug AG T


hermally conductive materials are essential for minimizing heat buildup within electronic


components and for effective heat dissipation. They are usually highly- abrasive potting materials with a concentration of special fillers. These fillers are designed to provide reli- able heat transfer between two parts, such as a PCB and a heat sink. The potting materials help to


prevent performance loss and mal- function due to overheating. These materials are commonly referred to as gap fillers or thermal interface materials (TIMs). They are often one- or two-component potting media, based on silicone, epoxy or poly - urethane. Additives or fillers will precisely modify the properties of the thermally conductive pastes and can be precisely modified and adjusted to fit specific applications.


Customized Systems The thermal conductivity of


these pastes is established with such fillers as aluminum oxide, graphite, silver or boron nitride. These fillers often exhibit high degrees of hard- ness, as well as sharp edges. When choosing systems for preparing and


dispensing thermal pastes, it is imperative to look for manufacturing equipment which is specifically tai- lored to the application. Otherwise, users face the risk of high mainte- nance and repair costs. The use of single-component materials is quite common, since


they do not require mixing and are supposedly easier to process. In real- ity, they require more elaborate logistics than two-component sys- tems. Depending on whether cross- linking reactions are initiated through humidity, UV rays or tem- perature, certain precautions must


be taken so that the material does not cure prematurely. This may involve continuous


cooling of the medium or special stor- age conditions for pails and car- tridges. Two-component TIMs, on the other hand, often have better materi- al properties, such as shorter curing times and reduced VOC emissions.


Thermal Pastes vs. Pads and Foils


In contrast to solid, die-cut pads


Thermal density is an ever-growing issue as component and assembly sizes shrink.


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or foils, thermally conductive pastes offer the possibility of creating indi- vidual contours on the component, which enables design freedom. Because they are conformal, ther- mally conductive pastes are best for components with complex topogra- phies or surface textures. Also, the fluidity of the material when com- pressed after its application allows for improved compensation of possi- ble tolerances. Sensitive electrical parts are exposed to less stress dur- ing assembly, considerably reducing the number of rejects. Pastes also have a higher thermal conductivity than pads or foils. Further advan- tages include lower storage costs,


Continued on next page


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