梯度铝石墨散热器材料的制备及性能研究

发布时间：2018-06-09 22:50

  本文选题：梯度铝石墨材料 + 大功率LED　； 参考：《江南大学》2014年硕士论文

【摘要】：LED是备受世界各国推崇的新一代绿色光源，具有低碳环保，节能稳定，寿命长等特点。大功率LED的兴起，更是迅速打入了传统灯具的市场，成为各行各业的新光源。 但是，目前市场上的大功率LED光能转换效率低，85%左右的能量以热能的形式散出。这会使芯片工作温度过高，灯具的寿命大打折扣。而现有的散热材料热导低，不能满足大功率LED的散热需求。热胀系数大，与芯片不匹配。梯度铝石墨复合材料轻质且具有良好的热物理性能，在改善大功率LED散热的同时也保证了一定的机械强度，逐渐被大功率LED产业重视并开发。 课题主要由大功率LED的封装及热分析，铝石墨复合材料的制备，梯度铝石墨材料的制备三个方面构成。 本论文对大功率LED的封装工艺及散热进行了研究。通过数学模型，ANSYS建模及热分析，寿命实验验证了以当前封装工艺为基础，通过使用梯度材料作散热器来降低芯片工作温度，改善大功率LED的散热，提高其使用寿命是可行的。 在铝石墨复合材料的制备工艺方面，对石墨在铝中的低溶解度，和鳞片石墨受压成层状不容易被渗透这一特性进行了探讨。通过实验方案比对，最终决定利用石墨这一层状特性来制备各向异性的铝石墨复合材料，即在压力的作用下，使熔融铝液沿着石墨预制块层面方向渗入，与石墨颗粒复合。实验论证，采用该工艺可制备石墨体积分数高达70%的铝石墨复合材料，材料致密均匀，且物理性能优良，密度为2.346g/cm3，两向热导率为分别λ//=566.767W/(m·K)和λ⊥=289.154W/(m·K)，两向热膨胀系数分别为α//=12.0543×10-6·K-1(50-150℃)和α⊥=12.2763×10-6·K-1(50-150℃)，性能参数优于现有的大功率LED散热器材料。 论文通过系列实验分析了影响铝石墨复合材料性能的一些因素。主要从铝，石墨，压铸参数，脱模和密封工艺几个方面阐述。最终选择ZL104为实验用铝材，为保证其流动性，熔融温度为750℃-780℃。颗粒大小为32-50目的天然鳞片石墨为增强体。当石墨颗粒小于80目时，不适合制备高体积分数的各向异性铝石墨材料。石墨体积分数越高，热物理性能越好，层面越不平整，两向性能差距越小。模具预热温度在700℃以下，预热时间1h以内，石墨的氧化失重效果可以忽略。以压机数据为准，压铸压力为15Mpa时得到的复合材料效果最好。微速与渗铝的面积，时间，距离等相关，需要通过计算获得。压铸前对外模具需采用颗粒脱模剂-密封材料-半固态脱模剂进行涂覆，并先对其进行1h，，95℃的低温烘干处理，再进行700℃以下的高温预热以保证铝液渗透的环境。 最后，本文选择了改变石墨体积分数来制备梯度铝石墨材料的方案。通过对预制块压块和底面成型面的设计来形成预制块内部石墨体积分数梯度，再进行渗铝压铸。此外还进行了石墨和铝混粉制备梯度材料的实验，均成功制备出梯度铝石墨材料。
[Abstract]:Led is a new generation of green light source, which has the characteristics of low carbon environmental protection, energy saving and stability, long life and so on. The rise of high-power LED has rapidly entered the market of traditional lamps and lanterns and become a new light source from all walks of life. However, at present, about 85% of the energy of high-power LEDs in the market is dissipated in the form of heat energy. This will make the chip working temperature is too high, the life of lamps and lanterns will be greatly reduced. However, the existing heat-dissipation materials have low thermal conductivity and can not meet the needs of high-power LEDs. The thermal expansion coefficient is large and does not match the chip. The gradient aluminum-graphite composite is lightweight and has good thermal physical properties, which not only improves the heat dissipation of high-power LED, but also ensures a certain mechanical strength. It has been paid more and more attention to and developed by the industry of high-power LED. The main task is the packaging and thermal analysis of high-power LEDs, and the preparation of aluminum-graphite composites. In this paper, the packaging technology and heat dissipation of high power LED are studied. Through mathematical model ANSYS modeling and thermal analysis, the life test verifies that based on the current packaging technology, using gradient material as radiator to reduce the working temperature of chip and improve the heat dissipation of high-power LED. It is feasible to improve its service life. The properties of low solubility of graphite in aluminum and the low penetration of flake graphite in aluminum are discussed in the aspect of preparation process of Al-graphite composites. Through the comparison of experimental schemes, it is decided to make use of the layer characteristic of graphite to prepare anisotropic Al-graphite composite material, that is to say, under the action of pressure, molten aluminum liquid can be infiltrated along the plane of the graphite preform and compound with graphite particles. The experimental results show that aluminum-graphite composites with graphite content of up to 70% can be prepared by this process, and the materials are compact and uniform, and the physical properties are excellent. The density is 2.346g / cm ~ (3), the thermal conductivity in two directions is 位 / R 566.767W / m K) and 位 ~ (-) = 289.154W / m ~ (K), the coefficient of thermal expansion is 12.0543 脳 10 ~ (-6) K ~ (-1) 50-150 鈩

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