Thermal conductivity behavior of SPS consolidated AlN/Al composites for thermal management applications

AlN/Al composites are a potentially new kind of thermal management material for electronic packaging and heat sink applications.The spark plasma sintering (SPS) technique was used for the first time to prepare the AlN/Al composites,and attention was focused on the effects of sintering parameters on the relative density,microstructure and,in particular,thermal conductivity behavior of the composites.The results showed that the relative density and thermal conductivity of the composites increased with increasing sintering temperature and pressure.The composites sintered at 1550 ℃ for 5 min under 70 MPa showed the maximum relative density and thermal conductivity,corresponding to 99% and 97.5 W m-1 K-1,respectively.However,the thermal conductivity of present AlN/Al composites is still far below the theoretical value.Possible reasons for this deviation were discussed.     

Effect of powder mixing process on the microstructure and thermal conductivity of Al/diamond composites fabricated by spark plasma sintering

Two powder mixing processes, mechanical mixing (MM) and mechanical alloying (MA), were used to prepare mixed Al/diamond powders, which were subsequently consolidated using spark plasma sintering (SPS) to produce bulk Al/diamond composites. The effects of the powder mixing process on the morphologies of the mixed powders, the microstructure and the thermal conductivity of the composites were investigated. The results show that the powder mixing process can significantly affect the microstructure and the thermal conductivity of the composites. Agglomerations of the particles occurred in mixed powders using MM for 30 min, which led to high pore content and weak interfacial bonding in the composites and resulted in low relative density and low thermal conductivity for the composites. Mixed powders of homogeneous distribution of diamond particles could be obtained using MA for 10 min and MM for 2 h. The composite prepared through MA indicated a high relative density but low thermal conductivity due to its defects, such as damaged particles, Fe impurity, and local interfacial debonding, which were mainly introduced in the MA process. In contrast, the composite made by MM for 2 h demonstrated high relative density and an excellent thermal conductivity of 325 W·m-1·K-1, owing to its having few defects and strong interfacial bonding.     

Si含量对Si/Al复合材料组织及性能的影响(英文)

采用放电等离子烧结(SPS)技术制备不同Si含量的电子封装用Si/Al复合材料,测试复合材料的性能,包括密度、热导率、热膨胀系数及弯曲强度;进行成分及断口分析,研究Si含量对Si/Al复合材料微观组织及热、力学性能的影响规律。结果表明:Si/Al复合材料由Si、Al组成,Al均匀分布于Si晶粒之间;随着Si含量的降低,Si/Al复合材料的相对密度不断增大,当Si含量为50%(体积分数)时,复合材料的相对密度达到98.0%;复合材料的热导率、热膨胀系数及弯曲强度均随着Si含量的增加而减小,当Si含量为60%(体积分数)时,复合材料具有最佳的热导率、热膨胀系数及强度匹配。     

放电等离子烧结法制备Cu/金刚石复合材料的性能与显微组织

由于具备较高的热导率,铜/金刚石复合材料已成为应用于电子封装领域的新一代热管理材料。采用放电等离子烧结工艺（SPS）成功制备含不同金刚石体积分数的Cu/金刚石复合材料,研究复合材料的相对密度、微观结构均匀性和热导率（TC）随金刚石体积分数（50%、60%和70%）和烧结温度的变化规律。结果表明：随着金刚石体积分数的降低,复合材料的相对密度、微观结构均匀性和热导率均升高;随着烧结温度的提高,复合材料的相对密度和热导率不断提高。复合材料的热导率受到金刚石体积分数、微观结构均匀性和复合材料相对密度的综合影响。     

烧结助剂Y2O3和Pr6O11对Al2O3陶瓷相对密度和热导率的影响

采用高分子网络法制备混合纳米粉体,研究稀土氧化物Y2O3和Pr6O11加入量对Al2O3陶瓷相对密度和热导率的影响。采用阿基米德方法测定样品的体积密度,利用激光脉冲法测量试样的热扩散率并计算得出热导率。结果表明:两种添加剂都可以降低Al2O3陶瓷的烧结温度,提高Al2O3陶瓷的热导率,其中Y2O3的促进作用较强;当保温时间相同、烧结温度为1 500~1 650℃时,Al2O3陶瓷的相对密度和热导率都随烧结温度的升高而增大;当烧结温度相同、保温时间为30~120 min时,Al2O3陶瓷的相对密度和热导率也随保温时间的延长而增大。     

Mechanical properties and expansion coefficient of Mo-Cu composites with different Ni contents

Mo-Cu composites were fabricated by powder metallurgy with addition of various Ni contents.The effect of Ni contents on mechanical and thermal properties of Mo-Cu composites was investigated.The results show that mechanical and thermal properties of Mo-Cu composites are greatly affected by the addition of Ni contents.The composite powders with Ni addition exhibits high sinterability.The sintering temperature is greatly decreased and the comprehensive properties of Mo-Cu composites are obviously improved.Mo-Cu composites with a content of 1.5 wt.％ Ni have relative density 99.2％,bending strength 1057.9 MPa,hardness 72.5 HRA,electronic resistivity 1.28× 10 -7Ω.m-1,thermal conductivity 139 W·m-1·K-1,and lower coefficient of thermal expansion 7.4×10-6 K 1.Mo-Cu composites have homogeneous and fine microstructure.The fracture mechanism is ductile fracture.     

液固分离法近净成形SiC_p/Al电子封装壳体的组织和性能(英文)

采用液固分离工艺制备高SiC体积分数Al基电子封装壳体(54%SiC,体积分数),借助光学显微镜和扫描电镜分析壳体复合材料中SiC的形态分布及其断口形貌,并测定其物理性能和力学性能。结果表明:SiCp/Al壳体复合材料中Al基体相互连接构成网状,SiC颗粒均匀镶嵌分布于Al基体中。复合材料的密度为2.93 g/cm3,致密度为98.7%,热导率为175 W/(m·K),热膨胀系数为10.3×10-6K-1(25~400°C),抗压强度为496 MPa,抗弯强度为404.5 MPa。复合材料的主要断裂方式为SiC颗粒的脆性断裂同时伴随着Al基体的韧性断裂,其热导率高于Si/Al合金的,热膨胀系数与芯片材料的相匹配。     

具有双层结构的电子封装用可激光焊接Si_p-SiC_p/Al混杂复合材料(英文)

结合预制件一次性模压成型和真空气压浸渗技术制备具有双层结构的高体积分数(60%~65%)、可激光焊接Sip-SiCp/Al混杂复合材料。该复合材料的组织结构均匀、致密,增强相颗粒均匀地分布在复合材料中,Sip/Al-SiCp/Al界面均匀、连续、结合紧密。性能测试表明,Sip-SiCp/Al混杂复合材料具有密度低(2.96 g/cm3)、热导率高(194 W/(mK))、热膨胀系数小(7.0×10-6K-1)、气密性好(1.0×10-3(Pacm3)/s)等优异特性。焊接试验表明,Sip-SiCp/Al混杂复合材料具有良好的激光焊接特性,其焊缝平整、致密,微观组织均匀,没有生成明显的气孔和脆性相Al4C3。同时,Sip-SiCp/Al混杂复合材料激光封焊后优异的气密性(4.8×10-2(Pacm3)/s)能够满足现代电子封装行业对气密性的严格要求。     

高温高压烧结金刚石-铜复合材料的研究

采用高温高压烧结工艺制备了金刚石体积分数为80%的金刚石-铜复合材料。研究了金刚石颗粒大小、烧结温度、烧结时间等因素对复合材料成分、界面状态和热导率的影响。结果表明:金刚石颗粒直径为80μm时,在高温高压条件下可获得热导率高达639 W.m-1.K-1的金刚石-铜复合材料。当金刚石体积分数一定时,存在一临界粒径,随金刚石颗粒直径增大复合材料热导率先增大后减小。恰当的烧结温度和时间有助于获得黏结良好的界面和高热导率。     

高温高压下新型金刚石/碳化硅热沉材料的热导率研究

本文针对国内外对高导热、低热膨胀系数的热沉材料需求,以金刚石为基体、硅粉为添加物,用国产六面顶压机在5.1 GPa,1 350～1 650℃的条件下,采用高压固液渗透法合成出金刚石/碳化硅陶瓷热沉材料,并对高压烧结体的相组成、密度与热导率进行了分析.研究结果表明:初始材料中硅含量、烧结时间与温度对烧结体的成分以及密度有...     

高体分比SiCp／Al复合材料的近净成形技术

高体积分数SiCp／Al复合材料具有优异的热物理性能,且密度较低,是非常理想的电子封装材料。但是由于其本身高的脆性和硬度,使得该材料很难通过二次机械加工成所需要的形状,严重制约了该材料的应用：采用粉末注射成形-无压熔渗工艺成功实现了高体积分数SiCp／Al复合材料的近净成形：采用该工艺所制备的复合材料的致密度高于99％,可实现热膨胀系数在（5—7）×10^-6K^-1范围内进行调节,材料的热导率高于185W／（m·K）,抗弯强度高于370MPa,气密性可达10^-11Pa·m^3·s^-1,各项指标均叮以满足电子封装对材料的性能要求,另外为了实现SiCp／Al复合材料与其他材料的封接,项目成功开发了一种Al—Si—Cu系焊料,封接后器件的各项性能指标尤其是气密性也均能满足使用要求。     

可加工AlN-BN复合陶瓷的制备

以碳热还原法合成的 AlN 粉末和市售 BN 粉末为原料,添加 5%Y2O3 为烧结助剂,利用无压烧结制备 AlN-15BN复合陶瓷,研究了烧结温度对 AlN-15BN 复合陶瓷相变、致密度、微观结构以及性能的影响,结果表明:Y2O3 可与 AlN粉末表面的 Al2O3 发生反应生成液相促进烧结,随着烧结温度的升高,复合陶瓷的致密度、热导率和硬度逐渐增加,片状的 BN 形成的卡片房式结构会阻碍复合陶瓷的收缩和致密。在 1 850℃烧结 3 h,可以制备出相对密度为 86.4%,热导率为104.6 W?m-1?K-1,硬度为 HRA56.2的 AlN-15BN复合陶瓷。研究表明,通过添加加工性能良好的 BN制备可加 AIN-BN复合陶瓷,是解决 AIB 陶瓷复杂形状成形问题的一个重要途径。     

放电等离子烧结Ti/Al_2O_3复合材料机制及性能

利用放电等离子烧结技术制备了Ti/Al_2O_3复合材料,并探讨了其烧结机理,对复合材料性能进行测试.结果表明,Ti/Al_2O_3导电网络结构的形成,有利于在烧结过程中形成的"电容器"瞬间击穿,使Al_2O_3遭到轰击而产生放电离子,活化Al_2O_3晶粒,降低烧结温度;当Ti 含量为40%(体积分数,下同)时复合材料的相对密度、弯曲强度、断裂韧性和显微硬度分别为99.74%、1002 MPa、19.73 MPa·m~(1/2)和18.14 GPa;裂纹的桥联、偏转是试验材料力学性能得以提高的主要原因.     

高温高压法制备金刚石/铜复合材料的研究

采用高温高压法制备金刚石/铜复合材料。研究金刚石体积分数、烧结压力、保温时间、烧结温度、金刚石表面金属化对金刚石/铜复合材料热导率及热膨胀系数的影响。实验表明:金刚石体积分数70%,烧结压力2 GPa,烧结时间300 s,烧结温度1200℃时,金刚石/铜复合材料热导率达426 W/（m·K）。      

AlN陶瓷基板材料的典型性能及其制备技术

AlN陶瓷是一种新型的基板材料,具有优异的电性能和热性能,被誉为新一代高密度封装的理想基板材料。介绍AlN陶瓷的典型性能和导热机理;讨论AlN粉末的5种合成方法：铝粉直接氮化法、Al2O3碳热还原法、化学气相沉积法、溶胶？凝胶法、自蔓延高温合成法和等离子化学合成法;分析AlN烧结助剂的选择和5种烧结工艺：热压烧结、无压烧结、放电等离子烧结、微波烧结及自蔓延烧结;阐述AlN基板的制备工艺及其影响因素。     

高分数GNFs/6061Al基复合材料的放电等离子体烧结制备及其显微组织与性能

采用放电等离子体烧结(SPS)工艺在610℃制备30％～50％(质量分数)纳米石墨片(GNF)/6061Al基复合材料,研究烧结压力及GNF含量对复合材料显微组织和力学、热学性能的影响.结果表明,SPS有效抑制GNFs/6061Al基复合材料中Al4C3等界面反应产物的生成.随着GNF含量的增加,GNFs团聚程度增加,...     

Finite Element Prediction of the Thermal Conductivity of GNP/Al Composites

A 3D multi-scale finite element model was developed to predict the effective thermal conductivity of graphene nanoplatelet (GNP)/Al composites. The factors influencing the effective thermal conductivity of the GNP/Al composites were investigated, including the orientation, shape, aspect ratio, configuration and volume fraction of GNPs. The results show that GNPs shape has a little influence on the thermal conductivity of GNP/Al composites, and composites with elliptic GNPs have the highest thermal conductivity. In addition, with increasing the aspect ratio of GNPs, the thermal conductivity of GNP/Al composites increases and finally tends to be stable. The GNPs configuration strongly influences the thermal conductivity of GNP/Al composites, and the thermal conductivity of the composites with layered GNPs is the highest among the five configurations. The effective thermal conductivity is sensitive to volume fraction of GNPs. Ideally, when the volume fraction of layered GNPs reaches 1.54%, the thermal conductivity of GNP/Al composites is as high as 400 W/m K. The findings of this study could provide a good theoretical basis for designing high thermal conductivity GNP/Al composites.     

Effect of particle size on the microstructure and thermal conductivity of Al/diamond composites prepared by spark plasma sintering

Spark plasma sintering (SPS) was used to fabricate Al/diamond composites. The influence of diamond particle size on the microstructure and thermal conductivity (TC) of composites was investigated by combining experimental results with model prediction. The results show that both composites with 40 μm particles and 70 μm particles exhibit high density and good TC, and the composite with 70 μm particles indicates an excellent TC of 325 W·m⁻¹·K⁻¹. Their TCs lay between the theoretical estimated bounds. In contrast, the composite with 100 μm particles demonstrates low density as well as poor TC due to its high porosity and weak interfacial bonding. Its TC is even considerably less than the lower bound of the predicted value. Using larger diamond particles can further enhance thermal conductive performance only based on the premise that highly dense composites of strong interfacial bonding can be obtained.     

Microstructure and Lattice Parameters of AIN Particle-Reinforced Magnesium Matrix Composites Fabricated by Powder Metallurgy

Magnesium matrix composites reinforced with A1N particles were fabricated by the powder metallurgy technique.The evolution of lattice constants and solid solubility levels of Al in a-Mg and the microstructure of Mg-Al/AIN composites were investigated in the present study.The results showed that the solid solubility of Al in ot-Mg reached a relatively high level by the P/M process with a long time of milling.X-ray diffraction showed that the peaks of Mg phase clearly shifted to higher angles.The lattice constants and cell volume decreased significantly compared with those of standard Mg due to a significant amount of Al incorporated into a-Mg in the form of substitutional solid solution.The degree of lattice deformation decreased at a low sintering temperature and increased at higher sintering temperatures due to the presence of A1N.Microstructural characterization of the composites revealed a necklace distribution of A1N particles in the Mg matrix.Heat treatment led to precipitation of Mg_(17)Al_(12) from the supersaturated a-Mg solid solution.The precipitate exhibited granular and lath-shaped morphologies in Mg matrix and flocculent precipitation around A1 N particles.     

放电等离子烧结温度对超细晶W-40Cu复合材料的影响

采用高能球磨法制备了W-40Cu超细晶复合粉体,继而进行了放电等离子烧结(SPS),获得了致密的超细晶W-40Cu块体复合材料,着重研究了烧结温度对复合材料组织和性能的影响.结果表明,随着烧结温度升高,材料的致密度、硬度和电导率也随之升高;在950℃烧结5 min的W-40Cu复合材料,W颗粒尺寸约300～500 nm,相对致密度达98％,显微硬度HV为287,电导率为17.9 MS/m.