دانشجویان کارشناسی ارشد سرامیک
دانشگاه آزاد اسلامی واحد نجف آباددانشجویان کارشناسی ارشد سرامیک
دانشگاه آزاد اسلامی واحد نجف آبادBoron Nitride
Boron Nitride.
HEXAGONAL BORON NITRIDE (HBN). Hexagonal boron nitride is a soft, graphite-like material. It can be hot-pressed into a wide variety of shapes, which can then be machined to final dimensions. It is available as powder that has excellent lubricating properties for applications such as a mold release medium. When mixed with epoxies or mold compounds, its high thermal conductivity, 55 W/(m ⋅ K), greatly enhances the thermal conductivity of the body. Thus, hBN-filled adhesives can be used for mounting semiconductor chips in high-power circuitry without compromising circuit performance.
Lelonis56 reports that boron nitride–filled epoxy molding compounds reduced thermal resistance of a 176-lead integrated circuit package from 20°C/W to 11°C/W. Boron nitride–filled epoxy demonstrated higher thermal conductivity than epoxies filled with aluminum oxide, aluminum nitride, or silica, over the 35 to 60 percent fill range. This result, along with its low thermal expansion and high electrical resistance make hBN an attractive filler material.
Boron nitride is a highly refractory material with physical and chemical properties similar to those of carbon. Known polymorphs of BN are graphite-like, wurtzite, and zinc blend, corresponding to the graphite (hexagonal) and diamond (cubic) structures. These two forms of boron nitride, hexagonal and cubic, have attracted the attention of potential users because of high thermal conductivity,38,56,57 hardness, compatibility with other materials, and other features. Both forms have properties that make manufacture of finished parts difficult. However, progress is being reported for both materials, and they are finding their way into wider usage. Both materials are discussed briefly below.
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