本文選題：梯度鋁石墨材料 + 大功率LED�。� 參考：《江南大學》2014年碩士論文

【摘要】：LED是備受世界各國推崇的新一代綠色光源，具有低碳環(huán)保，節(jié)能穩(wěn)定，壽命長等特點。大功率LED的興起，更是迅速打入了傳統(tǒng)燈具的市場，成為各行各業(yè)的新光源。 但是，目前市場上的大功率LED光能轉換效率低，85%左右的能量以熱能的形式散出。這會使芯片工作溫度過高，燈具的壽命大打折扣。而現有的散熱材料熱導低，不能滿足大功率LED的散熱需求。熱脹系數大，與芯片不匹配。梯度鋁石墨復合材料輕質且具有良好的熱物理性能，在改善大功率LED散熱的同時也保證了一定的機械強度，逐漸被大功率LED產業(yè)重視并開發(fā)。 課題主要由大功率LED的封裝及熱分析，鋁石墨復合材料的制備，梯度鋁石墨材料的制備三個方面構成。 本論文對大功率LED的封裝工藝及散熱進行了研究。通過數學模型，ANSYS建模及熱分析，壽命實驗驗證了以當前封裝工藝為基礎，通過使用梯度材料作散熱器來降低芯片工作溫度，改善大功率LED的散熱，提高其使用壽命是可行的。 在鋁石墨復合材料的制備工藝方面，對石墨在鋁中的低溶解度，和鱗片石墨受壓成層狀不容易被滲透這一特性進行了探討。通過實驗方案比對，最終決定利用石墨這一層狀特性來制備各向異性的鋁石墨復合材料，即在壓力的作用下，使熔融鋁液沿著石墨預制塊層面方向滲入，與石墨顆粒復合。實驗論證，采用該工藝可制備石墨體積分數高達70%的鋁石墨復合材料，材料致密均勻，且物理性能優(yōu)良，密度為2.346g/cm3，兩向熱導率為分別λ//=566.767W/(m·K)和λ⊥=289.154W/(m·K)，兩向熱膨脹系數分別為α//=12.0543×10-6·K-1(50-150℃)和α⊥=12.2763×10-6·K-1(50-150℃)，性能參數優(yōu)于現有的大功率LED散熱器材料。 論文通過系列實驗分析了影響鋁石墨復合材料性能的一些因素。主要從鋁，石墨，壓鑄參數，脫模和密封工藝幾個方面闡述。最終選擇ZL104為實驗用鋁材，為保證其流動性，熔融溫度為750℃-780℃。顆粒大小為32-50目的天然鱗片石墨為增強體。當石墨顆粒小于80目時，不適合制備高體積分數的各向異性鋁石墨材料。石墨體積分數越高，熱物理性能越好，層面越不平整，兩向性能差距越小。模具預熱溫度在700℃以下，預熱時間1h以內，石墨的氧化失重效果可以忽略。以壓機數據為準，壓鑄壓力為15Mpa時得到的復合材料效果最好。微速與滲鋁的面積，時間，距離等相關，需要通過計算獲得。壓鑄前對外模具需采用顆粒脫模劑-密封材料-半固態(tài)脫模劑進行涂覆，并先對其進行1h，，95℃的低溫烘干處理，再進行700℃以下的高溫預熱以保證鋁液滲透的環(huán)境。 最后，本文選擇了改變石墨體積分數來制備梯度鋁石墨材料的方案。通過對預制塊壓塊和底面成型面的設計來形成預制塊內部石墨體積分數梯度，再進行滲鋁壓鑄。此外還進行了石墨和鋁混粉制備梯度材料的實驗，均成功制備出梯度鋁石墨材料。
[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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