聚合物电阻浆料的研究

采用环氧-酚醛-缩醛改性复合粘结剂,导电材料用不同粒度和结构的碳黑,配制出的浆料对氧化铝等刚性基片有较大的附着力。同样可用树脂类柔性材料作基板,解决了浆料固化膜硬而脆、热老化性能差等问题,使固化膜形成一种致密的体型网状枝链,印刷膜层平滑,电性能一致。浆料的固化温度为170～250℃,固化时间为0.5～6h,能获得较好的电性能。     

两种热电分离式MCPCB导热性能的对比研究

利用SMT工艺将两种功率不同的LED分别与设计完全相同的热电分离式铜基板及铝基板组装成模组,然后借助结温测试系统及积分球系统对两种金属基板的散热性能进行了对比研究。结果表明,热电分离式铜基板较之热电分离式铝基板仅具备微弱的散热优势,这种优势随着LED的功率增加有所扩大。当LED功率为9 W时,铜基板及铝基板所对应的LED模组热阻分别是3.16℃/W、3.26℃/W;当LED功率为15 W时,铜基板及铝基板所对应的LED模组热阻分别是2.33℃/W、2.46℃/W。     

纳米添加剂对LED铝基板散热性能的影响

LED铝基板绝缘层的导热能力是影响大功率LED基板应用的主要因素.通过在环氧树脂中添加纳米级高导热填充物氧化铝、碳化硅、二氧化硅来提高绝缘层的导热能力,重点探讨填料种类、含量对基板绝缘层性能的影响,优化了填料配方.采用红外热像仪分析基板表面温度分布情况,通过散热实验测试铝基板的散热效果,结果证明导热效果良好.     

阳极氧化铝基板封装LED的结温与热阻的研究

采用阳极氧化法制备了氧化铝薄膜铝基板,并将3种功率(1W、3W、5W)的3种颜色(红、蓝、绿)的9种LED分别封装在所制备的铝基板和深圳光恒光电公司的铝基板上,利用正向压降法测试了其结温和热阻,发现:在LED颜色和功率相同的情况下,自制阳极氧化铝基板封装的LED的结温比封装在光恒铝基板上的低2.8～19.4℃,热阻低1.8～9.0K/W,表明自制铝基板的散热性能更优。     

厚膜陶瓷基片通孔填充工艺

随着厚膜电路技术的发展,混合集成电路的集成度越来越高,要求提高混合集成电路陶瓷基片布线密度,而陶瓷基片双面布线是提高集成密度的较好方式之一.双面布线需要在厚膜陶瓷基片上制作通孔,并对通孔进行导体填充,以实现陶瓷基片正反两面电性能导通和散热等功能,而制作性能良好的导体孔柱是厚膜工艺的难点.重点介绍了通过优化填孔设备压力参...     

铝膜穿透性阳极氧化技术

铝膜穿透性阳极氧化是实现阳极氧化铝薄膜多层布线基板制作的关键技术。研究了电流密度、电解质溶液温度和铝膜厚度对氧化时间的影响。绝缘电阻测定及扫描电子显微镜分析的结果证实了采用穿透性阳极氧化技术制作导带 ,导带间不存在残余铝薄膜。     

氮化铝-铝复合封装基板的制备

采用磁控溅射法在阳极氧化预处理过的铝板上沉积氮化铝薄膜,制备氮化铝-铝复合基板。制备的氮化铝为非晶态,抗电强度超过700 V/μm,阳极氧化铝抗电强度达75 V/μm。当阳极氧化铝膜厚约10μm、氮化铝膜约1μm时,制备的复合封装基板击穿电压超过1350 V,绝缘电阻率1.7×106 MΩ·cm,氮化铝与铝板的结合强度超过8 MPa;阳极氧化铝膜作为缓冲层有效缓解了氮化铝与铝热膨胀系数失配的问题,在260℃热冲击下,铝板未发生形变,氮化铝膜未破裂,电学性能无明显变化。氮化铝与阳极氧化膜的可见光高透性保持了镜面抛光金属铝的高反射率,当该复合基板应用于LED芯片COB封装时,有助于提高封装光效。     

大功率LED散热用微通道铝基板的有限元仿真

对带微通道的铝基板上封装的不同功率LED,用Comsol Multiphysics软件对其温度场进行了有限元模拟,重点研究了微通道的孔大小、孔间距、绝缘层的厚度和热导率对基板散热性能的影响,结果表明:铝基板厚度为1.5mm左右,微通道方形孔,孔长0.8mm,孔间距0.8mm,绝缘层厚度50μm,热导率1.5 W/(m·K),为最佳散热性能铝基板.微通道铝基板封装3W灯珠与普通铝基板和氮化铝基板相比,热阻分别下降了5.44和3.21℃/W,表明微通道铝基板能更好地满足大功率LED散热的需求.     

阳极氧化铝薄膜多层布线基板技术

本文介绍了一种制作多层布线基析的新技术－－选择性阳极氧化技术，用这种新技术，把非导体型区域的铝膜转变成隔离导带和通柱的绝缘氧化铝膜。在绝缘基板或者铝基光板上，形成多层布线结构。分析和阐述了这种多层布线基板的平面化结构特性、高导热特性、材料电特性及独特的封装形式，这种多层布线基板的平面化特性，使导体互连具有高密度和高可靠性优点，以铝基板为载体作为封装的一部分，充分体现了这种封装具有良好的电特性和热特     

一种新的LED灯具散热技术

散热一直是困扰LED灯具发展的难题,文章揭示一种新的散热技术：在铝基板上钻孔裸露出铝板并镀上金属层,使LED直接焊接在铝基板的铝板上,极大增强了LED灯具的散热能力,提高了LED灯具的寿命。     

高导热挠性铝基覆铜板用环氧胶粘剂的研究

采用高导热填料球形氧化铝填充环氧胶粘剂,并添加了适量离子捕捉剂有效地控制有害离子的离子迁移,利用该胶粘剂粘接铝箔和铜箔制备成挠性铝基覆铜板。文章中探讨了环氧胶粘剂的热固化温度和时间、球形氧化铝含量对胶膜热导率的影响,通过显微镜测试了导热填料在胶粘剂中的分散均匀性,最后确定最优配方制备出一种综合性能优异的挠性铝基覆铜板。     

Experiments on low velocity cooling of high conductivity substrates

Experiments are reported on low velocity cooling of a heater-on-substrate geometry for high conductivity substrate materials. Four different substrate materials were studied: 1) aluminum 6061-T6; 2) aluminum nitride; 3) alumina; 4) FR-4. The effects of combined buoyancy and forced air flow, geometric orientation, substrate size, thermal conductivity, and emittance on heat transfer are evaluated. Results define the performance of the substrates and the limits of conjugate mixed convection for horizontal substrates, and of orientation effects for substrates tilted from buoyancy-opposing to buoyancy-assisting orientations. An analytical approximation is described that predicts the experimental data with good accuracy over broad parameter ranges     

Formation of Thick Porous Anodic Alumina Films and Nanowire Arrays on Silicon Wafers and Glass

A method for the fabrication of thick films of porous anodic alumina on rigid substrates is described. The anodic alumina film was generated by the anodization of an aluminum film evaporated on the substrate. The morphology of the barrier layer between the porous film and the substrate was different from that of anodic films grown on aluminum substrates. The removal of the barrier layer and the electrochemical growth of nanowires within the ordered pores were accomplished without the need to remove the anodic film from the substrate. We fabricated porous anodic alumina samples over large areas (up to 70 cm²), and deposited in them nanowire arrays of various materials. Long nanowires were obtained with lengths of at least 9 μm and aspect ratios as high as 300. Due to their mechanical robustness and the built‐in contact between the conducting substrate and the nanowires, the structures were useful for electrical transport measurements on the arrays. The method was also demonstrated on patterned and non‐planar substrates, further expanding the range of applications of these porous alumina and nanowire assemblies.     

Metal-Core Printed Circuit Board With Alumina Layer by Aerosol Deposition Process

Heat dissipation properties of metal-core printed circuit boards (MCPCBs) having a ceramic dielectric layer are presented for high-power light-emitting diodes (LEDs). The proposed MCPCB is composed of a dense alumina thin film on an aluminum plate, instead of the conventional MCPCB with ceramic polymer composite, which shows low thermal conductivity. Dense alumina thin films, deposited by an aerosol deposition process, showed low leakage current and good dielectric breakdown for high-power applications. Thermal transient measurements of LEDs with the proposed MCPCB were compared to that of LEDs with conventional MCPCB. The MCPCBs proposed here showed better heat dissipation performance and lower thermal resistance.      

陶瓷电路基板的新型金属化技术

研制成功一种新型的陶瓷电路基板的金属化技术，它兼容了薄膜和厚膜技术的优点，采用ＳＥＭ研究了陶瓷基体的浸蚀特性。测量了金属化导体的附着强度、可焊性、薄层电阻、导热能力及微波损耗，并进行了温循和老化等可靠性试验。测试及应用结果表明，采用该技术可在氧化铝瓷基板上制作附着牢固的铜金属化电路图形，其机、电、热性能优良，可靠性好，为微波和混合集成电路衬底金属化技术开辟了新的工艺途径。     

Frequency effects on the dielectric properties of AlN film deposited by radio frequency reactive magnetron sputtering

Applications insulated metal substrates (IMS) for high-density and high-power mounting are greatly extending with miniaturizing of electronic components. Recently, aluminum nitride film has been used as a potential insulator and/or passivation material in insulated metal substrate because of its high intrinsic thermal conductivity, low thermal expansion coefficient, low dielectric constant and high electric resistivity. In this investigation, AlN films were deposited on Al substrates by radio frequency (RF) reactive magnetron sputtering. The metal-interfacial insulator layer-metal (Al/AlN/Al MIM) structures were obtained with AlN layer on Al substrates. Electrical properties of the MIM structures were investigated by meaning of C-V and C-f characteristics in the frequency range of 100 Hz-500 kHz and voltage range of −4 V to 4 V. Experimental results show that the dielectric constant of this structure decreases gradually with increasing frequency. While the dielectric loss tangent was tested from low frequency to high frequency, it is found that the dielectric loss tangent decreases from 0.03375, reaches a minimum (0.00424) at approximately 65 kHz and then increases sharply. These results are in accordance with modified model of Goswami and Goswami for such structure. The dielectric dispersion is observed due to distribution of interface states as well as ionized space charge carriers such as the oxygen atoms, nitrogen vacancies and defects. The AC conductivity results show that the electrical resistance decreases as the frequency increasing due to hopping type conduction.     

Polymer thick-films on silicon: a route to hybrid microsystems

The integration of polymer thick-film transducers and silicon offers a low-cost technology for the fabrication of hybrid microsystems. This paper presents a study on the feasibility and processing parameters of this integration. Selected transducer films were printed on silicon wafers covered with aluminum or various passivation layers and also on alumina for comparison. The quality of film adhesion was investigated using standard tape pull and scratch tests. Scanning electron microscopy and energy dispersive X-ray spectra analysis were used to investigate the interface between the films and the substrates. It was found that the films did not contaminate the wafers. We also characterized the film resolution by researching the wetting behavior of the pastes and the quality of printed patterns. The influence of the substrate's thermal coefficient of expansion on the resistance of a carbon polymer film was also analyzed. The experiments showed that the same design rules can be applied on both alumina and silicon substrates. Furthermore, dry and wet methods of etching and cleaning wafers from the thick-films were assessed. An insight into the potential and limitations of the technology is developed by discussing the issues of bonding mechanism, silicon contamination and influence of substrate on the resolution, electrical properties and infrared curing of the films. A design methodology for hybrid microsystems is proposed along with a suggestion for potential applications     

用于高温压力传感器的AIN绝缘膜的研究

采用直流磁控反应溅射法制备了高温压力传感器用的AIN薄膜。用X射线衍射对薄膜的晶向结构进行了分析，研究了薄膜的绝缘特性和化学稳定性，分析了AIN与Si的热膨胀系数、热导系数的关系。选用AIN在力敏电阻条和硅弹性膜之间进行绝缘隔离，由于无p-n结，力敏电阻无反向漏电，得到了极好的压力传感器特性，即零点电漂移及热漂移小及非线性小。     

Optoelectronic properties of expanding thermal plasma deposited textured zinc oxide: Effect of aluminum doping

Aluminum-doped zinc oxide films exhibiting a rough surface morphology are deposited on glass substrates utilizing expanding thermal plasma. Spectroscopic ellipsometry is used to evaluate optical and electronic film properties. The presence of aluminum donors in doped films is confirmed by a shift in the zinc oxide bandgap energy from 3.32 to 3.65 eV. In combination with transmission reflection measurements in the visible and NIR ranges, charge carrier densities, optical mobilities, and film resistivities have been obtained from the free carrier absorption. Film resistivities are consistent with direct measurements, values as low as 6.0×10⁻⁴ ω cm have been obtained. The interdependence of electrical conductivity, film composition, and film morphology is addressed.     

纳秒激光去除铝板表面漆膜热力学过程分析

为了研究并分析纳秒脉冲激光去除金属表面漆膜的机理,采用1064nm的纳秒激光对涂有漆膜的铝板样品进行了单脉冲辐照实验。依据热传导理论分别模拟出作用过程中漆膜以及铝板表层的温度分布,计算出漆膜与铝板界面处由于铝板基底热膨胀而产生的分离力,并分析了等离子体冲击波对去除漆膜的影响。结果表明,纳秒激光去除漆膜时力的作用为主导,其中热膨胀产生的分离力为漆膜的去除提供必要条件,漆膜对激光等离子体的约束最终导致其自身断裂和剥落。采用热力学理论对纳秒激光去除金属表面漆膜机理进行分析是可行的。