I-Corps: Thermally Conductive Polymer Based Interface Materials and Substrates

随着电子系统不断缩小，能量变得越来越密集，散热成为持续性能和可靠性的障碍。散热的主要挑战之一是在器件封装过程中两个表面接触的界面上的热传输。为了最大限度地提高界面之间的热传递，在两个表面之间放置导热材料，这些材料形成了近10亿美元的热界面材料(TIM)市场(BCC Research)。TIM几乎存在于所有形式的电子设备中，包括消费产品(手机、手提电脑等)、电力电子产品(电动汽车和用于可再生能源应用的电力转换器)和照明组件(包括新兴的发光二极管领域)，仅举几例。随着这些设备的性能和功率需求持续增加，产生的热量越来越多，需要移除的热量也越来越多，但传统的TIM缺乏足够的热量释放所需的热性能。该团队开发了一种新技术来制造聚合物，这种聚合物传统上不能很好地导热，具有非常高的导热系数，可用作TIM。这些材料将为包装和热工程师提供一种新的武器来解决电子发热问题，这将允许在广泛的技术系统中继续创新。提出的热界面材料(TIMs)表现出更强的机械柔韧性和导热性，从而产生了完全由具有前所未有的导热性的聚合物组成的“软”材料。传统上，“软”和力学兼容的材料，如聚合物，受到分子无序导致声子散射的低导热系数的困扰。为了克服导热系数低的问题，经常加入高导热系数的填料来提高复合材料的导热系数，但导热系数的提高受到界面声子散射的限制，高填充分数会影响材料的力学性能。该团队发现，纳米尺度的限制(迫使聚合物进入非常小的孔)可以用来诱导聚合物链的排列，这大大提高了聚合物在排列方向上的导热系数。使用氧化铝纳米多孔模板，该团队能够制造大面积的纳米受限聚合物纳米线阵列，具有更好的导热性，用作热界面材料。建议的材料通过熔融或电化学方法加工，可以使用多种聚合物系统和体系结构来制造，使它们适合于许多潜在的热管理应用。这些材料的导热系数高于块状聚合物的50倍，并将允许改进的电子设备，即使在功率密度增加的情况下也能保持较低的工作温度。

As electronic systems continue to shrink and become more energy dense, thermal dissipation is emerging as a roadblock to sustained performance and reliability. One of the main challenges to heat removal is heat transport across interfaces where two surfaces are placed in contact during device packaging. In order to maximize the thermal transport across interfaces, thermally conductive materials are placed between the two surfaces and these materials form the nearly 1 billion dollar market for thermal interface materials (TIMs) (BCC Research). TIMs are found in nearly all forms of electronic devices including consumer products (cell phones, labtops, etc.), power electronics (electric vehicles and power converters for renewable energy applications), and lighting assemblies (including the emerging field of light emitting diodes), to name a few. As the performance and power demands of these devices continues to increase, more heat is being generated and needs to be removed, yet traditional TIMs lack the thermal properties required to enable sufficient heat removal. This team has developed a new technique to fabricate polymers, which traditionally do not conduct heat well, with very high thermal conductivity for use as TIMs. These materials will provide packaging and thermal engineers with a new weapon to combat the electronics heating problem, which will allow for continued innovation across a wide breath of technological systems. The proposed thermal interface materials (TIMs) demonstrate enhanced mechanical compliance and thermal conductivity, resulting in "soft" materials that are exclusively composed of polymer with unprecedented thermal conductivity. Traditionally, "soft" and mechanically compliant materials such as polymers are plagued by low thermal conductivity due to molecular disorder which results in phonon scattering. To overcome low thermal conductivity, high conductivity fillers are often added to improve composite conductivity, but the improvement in thermal conductivity is limited by interfacial phonon scattering and high fill fractions can compromise the materials mechanical properties. This team has found that nanoscale confinement (forcing the polymer into very small pores) can be used to induce alignment of polymer chains, which greatly improves polymer thermal conductivity in the direction of alignment. Using alumina oxide nanoporous templates the team is able to fabricate large area arrays of nanoconfined polymer nanowires with improved thermal conductivity for use as thermal interface materials. The proposed materials are processed through melt or electrochemical methods and can be fabricated using a multitude of polymer systems and architectures, making them suitable for many potential thermal management applications. These materials exhibit thermal conductivities greater than 50x that of bulk polymer and will allow for improved electronics that can maintain low operational temperatures even at increased power densities.