聚合物基复合封装材料导热性能的参数仿真

鉴于聚合物基复合封装材料导热性能传统研究方法的不足(效率低、预测模型不合理等),提出了一种基于VC++结合ANSYS和MATLAB联合编程的方法,对聚合物基复合材料的导热性能进行参数化有限元分析。用户只需要在由VC++开发出来的人机交互界面上输入复合材料的相关导热参数,即可由ANSYS与MATLAB相互协作完成导热模型的构建、模型导热率的数值仿真、结果输出的可视化处理等一系列工作。通过分析氮化铝填充环氧树脂复合材料的导热性能,检验了该方法的可靠性。研究结果表明,该方法不仅能够有效地预测实验结果,而且还方便易用。     

高导热聚合物基复合封装材料及其应用

微电子封装密度的提高对传统环氧塑封料的导热性能提出了更高的要求,将高导热的陶瓷颗粒/纤维材料添加到聚合物塑封材料中可获得导热性能好的复合型电子封装材料。文章结合高导热环氧塑封材料的研究工作,评述了高热导聚合物基复合封装材料的材料体系、性能特点和在微电子封装中的应用情况。分析讨论了影响聚合物基复合电子封装材料导热性能和介电性能的因素,提出了进一步提高聚合物基复合电子封装材料导热性能的途径。     

无机导热粒子对铝基板导热性能的影响

随着电子信息产业的高速发展,对铝基板覆铜板导热性能的要求也越来越高,提升铝基板覆铜板导热率的关键在于提高绝缘层的导热率,绝缘层以环氧树脂为基体材料,填充的无机导热粒子间通过相互接触形成三维导热网络通路,从而提升铝基覆铜板的导热性能。实验结果表明,当基体材料与主要填充的三种无机陶瓷导热粒子的比例达到ＥＰ∶ＢＮ∶ＡｌＮ∶Ａｌ２Ｏ３＝ 1.9∶1∶3∶6时,绝缘层的导热系数最终可以达到2.8Ｗ/ (ｍ·Ｋ)。     

新产品与新技术（5）

采用LCP的多层电路板技术实用化瑞士的挠性印制板制造企业Diconecs公司成功使用液晶聚合物(LCP)材料制作多层印制板,并达到实用化。LCP作为印制板基材,适应电子信号高频高速传     

导热印制板的研制和应用

在常规印制电路板的表面覆合漏空的绝缘层和铝板,做成新颖的印制电路板,即导热印制板。与常规印制板相比,导热印制板具有与之相当的焊接性能和加工性能,但具有常规印制板所缺乏的高导热性、高抗干扰能力,以及较高的耐热、耐燃及结构稳定性。在电子产品中使用导热印制板可以有效地提高设备可靠性。延长使用寿命,并可以不用或少用散热器,从而缩小体积。导热印制板是印制电路板热设计的一种新颖结构形式。本文说明了导热印制板的结构原理,概要地介绍了研制过程、工艺方法及性能测试,较详细地叙述了应用试验情况和使用效果,并对导热印制板的特性作了分析归纳。     

石墨烯/聚合物功能化复合材料的研究进展

石墨烯是一种具有二维结构的纳米碳材料,具有独特的物理性能,如比表面积大、导电导热性好、机械强度高等,因此在材料的轻质高强、导热、导电、电磁屏蔽等领域均备受关注。本文主要侧重介绍石墨烯/聚合物功能化复合材料的代表性研究成果,并对目前石墨烯复合材料的规模化应用进行评述,综合分析石墨烯/聚合物复合材料存在的关键问题及未来发展趋势。     

T-Lam材料体系

随着PCB高密度化多功能化和微小型化的发展,PCB热设计已成为突出的问题。除了加强PCB外部装置外,重要的是将PCB内部的热量迅速而及时的传导或散发出来,除了金属印制板外,采用导热好的介电(绝缘)材料显得十分重要,只要把导体线路的热通过导热好绝缘材料再传导散发出去。这种T-Lam材料具有高的导热率,高介电强度。优良的粘结力和热稳定性。其半固化片(T-preg)用于导热性多层板中是十分理想的。无疑这种T-Lam材料具有越来越广阔的应用天地。现将胜庚义同志译编并经林金堵审议后刊出。本刊将刊出“T-Lam材料体系”“第一部分:关于IMPCB性能和可靠性设计指南”“第二部分:关于Thenagon T-Lam材料的可制造性指南”和“用导热性半固化制造印制板”等四个部分,以使同行业者有个较完整的概念。     

高频铜基板加工技术研究

随着高频接收机、大功率模块电源的快速发展,因高频铜基板有效兼顾了高频信号传输与导热性而作为一种最常见的金属基印制板被广泛应用。本文通过加工试验高频材料制作铜基板,总结出相应加工工艺并解决了加工中的难题,引入新的技术监测层压空洞问题,为高频金属基印制板的批量生产奠定了基础。     

一类新型高导热环氧模塑料的制备

采用Si3N4陶瓷作填料,制备了一类新型高导热的环氧模塑料,研究了Si3N4的含量、分布及其形态对复合材料的导热性能及介电性能的影响。结果表明:随着Si3N4粉末体积填充量的增加,复合材料的热导率显著提高,当填充量体积分数为60%时,复合材料的热导率达到2.3W/(m·K),其介电常数随体积填充量的增加亦有所增加,但仍然维持在低水平。采用Agari模型进行理论计算的结果表明,该体系导热性能的提高与Si3N4填料之间热传导网络的形成有关。     

导热功能橡胶的导热机理及其导热性能的影响因素

本文介绍了导热功能橡胶的研究现状及导热机理,着重分析了影响填充型导热功能橡胶导热性能的主要因素,并阐述了导热橡胶的应用及发展方向。     

Rudimentary Finite Element Thermal Modeling of Platelet-Filled Polymer-Ceramic Composites

In order to improve the thermal performance of polymeric materials, they can be filled with intrinsically high thermal conductivity fillers that provide heat-conducting paths through the resulting composite. The thermal performance of polymers loaded with platelet-shaped fillers was modeled using finite element analysis in order to provide a prediction of thermal conductivity as a function of variables such as filler thermal conductivity, orientation, and polymer matrix thermal conductivity. Modeling results were compared to experimental data. An unexpectedly strong effect that the matrix conductivity has on the conductivity of the polymer-ceramic composite was predicted by modeling and confirmed experimentally.     

In-situ analysis of thermal properties of polymer composites by embedded LED temperature sensor

Real time and accurate measurement of thermal conductivity of polymer composites with thermal conductive fillers challenges researchers in industrial application. Here, we present an in-situ measurement approach by embedding a LED or diode as a combined heat source and temperature sensor into the filled polymer and using the well-established transient measuring method based on forward voltage variation to determine the temperature response of the sensor in polymer. Numerical model fitting is applied to estimate the thermal conductivity of the polymer composites with different filler/polymer ratios. These findings are compared with other thermal conductivity test methods such as the laser flash method and the Modular Differential Scanning Calorimeter (MDSC). The proposed approach provides a quick way of measuring the thermal conductivity in relatively thin polymer composites and agrees well with the MDSC method. Another advantage is that it can work with the real samples made for the application in mind, so its results can be used directly.     

Improving thermal conductivity of polymer composites in embedded LEDs systems

Polymer embedding of LEDs increases safety and waterproof levels in LED based lighting systems. The embedding allows for mechanical flexibility of these systems. The increase of polymer thermal conductivity has been a research challenge for decades. Here, we suggest materials for enhancing thermal conductivity in polymer embedded LED systems. We demonstrate that thermally conductive fillers into the polymer matrix to form a composite improved heat transfer from the LEDs to the environment. Non metallic boron nitride with a high intrinsic thermal conductivity is a good candidate. Thermal conductivity of basic polymer PDMS with various filler size and polymer ratios is reported here. Here, an in situ measurement tool to fast evaluate the quality of the composites in LED applications is demonstrated. Future work will focus on further increasing the thermal conductivity of the composites by using different mixtures.     

ECWC13中的PCB基材技术

本文对第13届世界电子电路大会中收录的关于PCB基材技术方面的论文进行了综述：杜邦公司推出了基于高频高速、热量管理及设计方面的新型高频高速挠性板材料Du Pont TM Pyralux TK（TK）及Du Pont TM Pyralux JT（JT）;台湾工研院对于环保材料在CCL的应用中有较深入的研究,并介绍了气相生长碳纤维材料应用于聚酰亚胺挠性板中的研究情况;广州兴森快捷公司对含有热致液晶材料的PCB板的生产参数进行摸索和考察,以验证其在电子电路行业的实际应用;EIPC主席Alun Morgan撰写的关于阻燃剂的论文,则对含卤阻燃剂在行业中的继续应用仍然抱有很大的信心;德国Nabaltec AG公司的Carsten W.IHmels的文章详细介绍了阻燃剂勃姆石在PCB材料中的应用。这些论文展示的一些研究结果,我们可以大概了解到当今PCB基材发展的大致趋势,及一些新型材料的在PCB基材中应用情况。     

Towards Thermoconductive,Electrically Insulating Polymeric Composites with Boron Nitride Nanotubes as Fillers

Ultilizing boron nitride nanotubes (BNNTs) as fillers, composites are fabricated with poly(methyl methacrylate), polystyrene, poly(vinyl butyral), or poly(ethylene vinyl alcohol) as the matrix and their thermal, electrical, and mechanical properties are evaluated. More than 20‐fold thermal conductivity improvement in BNNT‐containing polymers is obtained, and such composites maintain good electrical insulation. The coefficient of thermal expansion (CTE) of the BNNT‐loaded polymers is dramatically reduced because of interactions between the polymer chains and the nanotubes. Moreover, the composites possess good mechanical properties, as revealed by Vickers microhardness tests. This detailed study indicates that BNNTs are very promising nanofillers for polymeric composites, allowing the simultaneous achievement of high thermal conductivity, low CTE, and high electrical resistance, as required for novel and efficient heat‐releasing materials.     

An Anisotropically High Thermal Conductive Boron Nitride/Epoxy Composite Based on Nacre‐Mimetic 3D Network

Polymer‐based thermal interface materials (TIMs) with excellent thermal conductivity and electrical resistivity are in high demand in the electronics industry. In the past decade, thermally conductive fillers, such as boron nitride nanosheets (BNNS), were usually incorporated into the polymer‐based TIMs to improve their thermal conductivity for efficient heat management. However, the thermal performance of those composites means that they are still far from practical applications, mainly because of poor control over the 3D conductive network. In the present work, a high thermally conductive BNNS/epoxy composite is fabricated by building a nacre‐mimetic 3D conductive network within an epoxy resin matrix, realized by a unique bidirectional freezing technique. The as‐prepared composite exhibits a high thermal conductivity (6.07 W m^?1 K^?1) at 15 vol% BNNS loading, outstanding electrical resistivity, and thermal stability, making it attractive to electronic packaging applications. In addition, this research provides a promising strategy to achieve high thermal conductive polymer‐based TIMs by building efficient 3D conductive networks.     

Thermal Transport in 3D Nanostructures

This work summarizes the recent progress on the thermal transport properties of 3D nanostructures, with an emphasis on experimental results. Depending on the applications, different 3D nanostructures can be prepared or designed to either achieve a low thermal conductivity for thermal insulation or thermoelectric devices or a high thermal conductivity for thermal interface materials used in the continuing miniaturization of electronics. A broad range of 3D nanostructures are discussed, ranging from colloidal crystals/assemblies, array structures, holey structures, hierarchical structures, to 3D nanostructured fillers for metal matrix composites and polymer composites. Different factors that impact the thermal conductivity of these 3D structures are compared and analyzed. This work provides an overall understanding of the thermal transport properties of various 3D nanostructures, which will shed light on the thermal management at nanoscale.     

Polyhedral Oligosilsesquioxane‐Modified Boron Nitride Nanotube Based Epoxy Nanocomposites: An Ideal Dielectric Material with High Thermal Conductivity

Dielectric polymer composites with high thermal conductivity are very promising for microelectronic packaging and thermal management application in new energy systems such as solar cells and light emitting diodes (LEDs). However, a well‐known paradox is that conventional composites with high thermal conductivity usually suffer from the high dielectric constant and high dielectric loss, while on the other hand, composite materials with excellent dielectric properties usually possess low thermal conductivity. In this work, an ideal dielectric thermally conductive epoxy nanocomposite is successfully fabricated using polyhedral oligosilsesquioxane (POSS) functionalized boron nitride nanotubes (BNNTs) as fillers. The nanocomposites with 30 wt% fraction of POSS modified BNNTs exhibit much lower dielectric constant, dielectric loss tangent, and coefficient of thermal expansion in comparison with the pure epoxy resin. As an example, below 100 Hz, the dielectric loss of the nanocomposites with 20 and 30 wt% BNNTs is reduced by one order of magnitude in comparison with the pure epoxy resin. Moreover, the nanocomposites show a dramatic thermal conductivity enhancement of 1360% in comparison with the pristine epoxy resin at a BNNT loading fraction of 30 wt%. The merits of the designed composites are suggested to originate from the excellent intrinsic properties of embedded BNNTs, effective surface modification by POSS molecules, and carefully developed composite preparation methods.     

An improvement of thermal conductivity of underfill materials for flip-chip packages

Effective heat dissipation is crucial to enhance the performance and reliability of electronic devices. In this work, the performance of encapsulants filled with carbon fiber was studied and compared with silica filled encapsulants. Encapsulants filled with mixed combination of fillers for optimizing key properties were also investigated. The thermal and electrical conductivities were investigated and glass transition temperature (Tg), thermal expansion coefficient (TCE), and storage modulus (E') of these materials were studied with thermal analysis methods. The composites filled with both carbon fiber and silica showed an increase of thermal conductivity three to five times of that of silica filled encapsulants of the same filler loading while maintaining/enhancing major mechanical and thermal properties.     

A Roadmap Review of Thermally Conductive Polymer Composites: Critical Factors,Progress, and Prospects

Recently, the need for miniaturization and high integration have steered a strong technical wave in developing (micro-)electronic devices. However, excessive amounts of heat may be generated during operation/charging, severely affecting device performance and leading to life/property loss. Benefiting from their low density, easy processing and low manufacturing cost, thermally conductive polymer composites have become a research hotspot to mitigate the disadvantage of excessive heat, with potential applications in 5G communication, electronic packaging and energy transmission. By far, the reported thermal conductivity coefficient (λ) of thermally conductive polymer composite is far from expectation. Deeper understanding of heat transfer mechanism is desired for developing next generation thermally conductive composites. This review holistically scopes current advances in this field, while giving special attention to critical factors that affect thermal conductivity in polymer composites as well as the thermal conduction mechanisms on how to enhance the λ value. This review covers critical factors such as interfacial thermal resistance, chain structure of polymer, intrinsic λ value of different thermally conductive fillers, orientation/configuration of nanoparticles, 3D interconnected networks, processing technology, etc. The applications of thermally conductive polymer composites in electronic devices are summarized. The existing problems are also discussed, new challenges and opportunities are prospected.