高性能导热绝缘环氧封装料的研究进展

环氧封装料具有强粘结、高强度、耐高温与耐腐蚀等优点,广泛应用于电子封装领域。随着电子产业的升级换代,环氧封装料在导热、热膨胀、介电和绝缘等性能方面表现不足,阻碍了其在高频与高压等极端条件下的使用,如何解决这些不足是该研究领域的挑战性科学与应用问题。本文首先介绍复合材料的基本导热理论与模型,进而系统综述近年来高导热、低热膨胀、低介电和高击穿环氧封装料领域的研究进展,分析总结其中存在的共性科学问题,并提出解决方法与思路。最后,对环氧封装料在基体、填料、界面及加工等研究方面亟需解决的关键问题及研究重点进行了展望。

IGBT用环氧树脂封装料的制备与性能研究

以甲基六氢苯酐(MeHHPA)为固化剂,端羧基液体丁腈橡胶(CTBN)为增韧剂,对混合环氧树脂SRTEM-80/REDG-80/E-158进行改性;采用不同用量的硅烷偶联剂KH-570对氧化铝和硅粉复配填料进行改性;最终制备了绝缘栅双极晶体管(IGBT)用环氧树脂封装料。并对封装料的黏度、凝胶化时间、热导率、电气性能、弯曲强度和吸水率等进行测试。研究结果表明,此环氧树脂封装料具有低黏度、良好的绝缘性能和耐湿性等;硅烷偶联剂KH-570用量为1.5%时,封装料的热导率最高为1.191W/(m·K),体积电阻率5.95×10^(15)Ω·m,击穿场强为28.28kV/mm,tgδ为0.62%,弯曲强度为74.32MPa,吸水率小于0.1%;最佳的固化工艺条件为80℃/2h、120℃/2h。

聚硅氧烷在环氧封装料改性中的应用

综述了用功能性聚硅氧烷对环氧树脂封装料进行改性从而实现环氧封装料低应力化的几种方法；并对改性后封装料的结构、热性能和机械性能作了详细介绍。

Microstructure and properties of Cu matrix composites reinforced with surface-modified Kovar particles

The thermal conductivity of Cu/Kovar composites was improved by suppressing element diffusion at the interfaces through the formation of FeWO_(4)coating on the Kovar particles via vacuum deposition.Cu matrix composites reinforced with unmodified(Cu/Kovar)and modified Kovar(Cu/Kovar@)particles were prepared by hot pressing.The results demonstrate that the interfaces of Cu/FeWO_(4)and FeWO_(4)/Kovar in the Cu/Kovar@composites exhibit strong bonding,and no secondary phase is generated.The presence of FeWO_(4)impedes interfacial diffusion within the composite,resulting in an increase in grain size and a decrease in dislocation density.After surface modification of the Kovar particle,the thermal conductivity of Cu/Kovar@composite is increased by 110%from 40.6 to 85.6 W·m^(-1)·K^(-1).Moreover,the thermal expansion coefficient of the Cu/Kovar@composite is 9.8×10^(-6)K^(-1),meeting the electronic packaging requirements.

Microstructures and properties of Al-50%SiC composites for electronic packaging applications

Al？50%SiC （volume fraction） composites containing different sizesofSiC particles （average sizesof 23, 38 and 75 μm） were prepared by powder metallurgy. The influences of SiC particle sizes and annealing on the propertiesof the compositeswere investigated. The results show that SiC particles are distributed uniformly in the Al matrix. The coarse SiC particles result in higher coefficient of thermal expansion （CTE） and higher thermal conductivity （TC）, while fine SiC particles decrease CTE and improve flexural strength of the composites. The morphology and size of SiC particles in the composite are not influenced by the annealing treatment at 400℃for 6h. However, the CTE and the flexural strength of annealed composites are decreased slightly, and the TCis improved. The TC, CTE and flexural strength of the Al/SiC composite with averageSiC particlesize of75 μm are 156 W/（m·K）, 11.6×10^-6K^-1 and 229 MPa, respectively.

Microstructure characterization and thermal properties of hypereutectic Si-Al alloy for electronic packaging applications

The rapid solidified process and hot press method were performed to produce three hypereutectic 55%Si-Al, 70%Si-Al and 90%Si-Al alloys for heat dissipation materials. The results show that the atomization is an effective rapid solidified method to produce the Si-Al alloy and the size of atomized Si-Al alloy powder is less than 50 μm. The rapid solidified Si-Al alloy powder were hot pressed at 550 ℃ with the pressure of 700 MPa to obtain the relative densities of 99.4%, 99.2% and 94.4% for 55%Si-Al, 70%Si-Al and 90%Si-Al alloys, respectively. The typical physical properties, such as the thermal conductivity, coefficient of thermal expansion （CTE） and electrical conductivity of rapid solidified Si-Al alloys are acceptable as a heat dissipation material for many semiconductor devices. The 55%Si-Al alloy changes greatly （CTE） with the increase of temperature but obtains a good thermal conductivity. The CTE of 90%Si-Al alloy matches with the silicon very well but its thermal conductivity value is less than 100 W/（m.K）. Therefore, the 70%Si-Al alloy possesses the best comprehensive properties of CTE and thermal conductivity for using as the heat sink materials.

Microstructure and properties of Al/Si/SiC composites for electronic packaging

The Al/Si/SiC composites with medium volume fraction for electronic packaging were fabricated by gas pressure infiltration.On the premise of keeping the machinability of the composites,the silicon carbide particles,which have the similar size with silicon particles（average 13 μm）,were added to replace silicon particles of same volume fraction,and microstructure and properties of the composites were investigated.The results show that reinforcing particles are distributed uniformly and no apparent pores are observed in the composites.It is also observed that higher thermal conductivity（TC） and flexural strength will be obtained with the addition of SiC particles.Meanwhile,coefficient of thermal expansion（CTE） changes smaller than TC.Models for predicting thermal properties were also discussed.Equivalent effective conductivity（EEC） was proposed to make H-J model suitable for hybrid particles and multimodal particle size distribution.

MT型硅氧烷低聚物及含MT结构的聚硅氧烷(三)

概述了乙烯基甲基苯基MT聚硅氧烷的合成方法及应用实例。

加成型室温和中温硫化硅橡胶

这种硅橡胶除了具有通常硅橡胶的性能外如可耐-65---+200℃、绝缘、防潮、耐紫外光等,同时它又是液态,可作为封装料和粘结剂,由于硫化时不放出付产物,所以橡胶制品尺寸稳定。这种胶国内虽有几个厂家生产。

Effects of rolling and annealing on microstructures and properties of Cu/Invar electronic packaging composites prepared by powder metallurgy

The Cu/Invar composites of 40% Cu were prepared by powder metallurgy, and the composites were rolled with 70% reduction and subsequently annealed at 750 ℃. Phases, microstructures and properties of the composites were then studied. After that, the amount of a-Fe（Ni,Co） in the composites is reduced, because a-Fe（Ni,Co） partly transfers into y-Fe（Ni,Co） through the diffusion of the Ni atoms into a-Fe（Ni,Co） from Cu. When the rolling reduction is less than 40%, the deformation of Cu takes place, resulting in the movement of the Invar particles and the seaming of the pores. When the rolling reduction is in the range from 40% to 60%, the deformations of Invar and Cu occur simultaneously to form a streamline structure. After rolling till 70% and subsequent annealing, the Cu/Invar composites have fine comprehensive properties with a relative density of 98.6%, a tensile strength of 360 MPa, an elongation rate of 50%, a thermal conductivity of 25.42 W/（m.K） （as-tested） and a CTE of 10.79× 10-6/K （20-100 ℃）.

Microstructure and properties of high-fraction graphite nanoflakes/6061Al matrix composites fabricated via spark plasma sintering

30-50 wt.%graphite nanoflakes(GNFs)/6061Al matrix composites were fabricated via spark plasma sintering(SPS)at 610℃.The effects of the sintering pressure and GNF content on the microstructure and properties of the composites were investigated.The results indicated that interfacial reactions were inhibited during SPS because no Al4C3 was detected.Moreover,the agglomeration of the GNFs increased,and the distribution orientation of the GNFs decreased with increasing the GNF content.The relative density,bending strength,and coefficient of thermal expansion(CTE)of the composites decreased,while the thermal conductivity(TC)in the X−Y direction increased.As the sintering pressure increased,the GNFs deagglomerated and were distributed preferentially in the X−Y direction,which increased the relative density,bending strength and TC,and decreased the CTE of the composites.The 50wt.%GNFs/6061Al matrix composite sintered at 610℃ under 55 MPa demonstrated the best performance,i.e.,bending strength of 72 MPa,TC and CTE(RT−100℃)of 254 W/(m·K)and 8.5×10^(−6)K^(−1)in the X−Y direction,and 55 W/(m·K)and 9.7×10^(−6)K^(−1)in the Z direction,respectively.

Numerical simulation on thixoforging of electronic packaging shell with SiC_p/A356 composites

Based on the research of modem electronic packaging materials, thixo-forming technology was used to fabricate electronic packaging shell. The process of thixo-extrusion with SiCp/A356 composites was simulated by the finite element software DEFORM-3D, then the flow velocity field, equivalent strain field and temperature field were analyzed. The electronic packaging shell was manufactured by extrusion according to the results from numerical simulation. The results show that thixo-forming technology can be used in producing electronic package shell with SiCp/A356 composites, and high volume fraction of SiCp with homogeneous distribution can be achieved, being in agreement with the requirements of electronic packaging materials.

Microstructure and properties of electronic packaging shell with high silicon carbide aluminum-base composites by semi-solid thixoforming

The electronic packaging shell with high silicon carbide aluminum-base composites was prepared by semi-solid thixoforming technique. The flow characteristic of the Si C particulate was analyzed. The microstructures of different parts of the shell were observed by scanning electron microscopy and optical microscopy, and the thermophysical and mechanical properties of the shell were tested. The results show that there exists the segregation phenomenon between the Si C particulate and the liquid phase during thixoforming, the liquid phase flows from the shell, and the Si C particles accumulate at the bottom of the shell. The volume fraction of Si C decreases gradually from the bottom to the walls. Accordingly, the thermal conductivities of bottom center and walls are 178 and 164 W·m-1·K-1, the coefficients of thermal expansion(CTE) are 8.2×10-6 and 12.6×10-6 K-1, respectively. The flexural strength decreases slightly from 437 to 347 MPa. The microstructures and properties of the shell show gradient distribution.

Surface Morphology of Reactive Powder Concrete Containing Soil

Recent studies have revealed that concrete can be used as a media to contain As （arsenic） removed from drinking water. Concrete, which is a composite material, has been effective in solidifying hazardous wastes and contaminated soils. A research project was conducted to study the effects of uncontaminated soil and arsenic contaminated soil on the microstructure of concrete to qualitatively define the mechanisms of the encapsulation of soils containing inorganic material such as arsenic by application of solidification/stabilization technique. This research paper focused on studying the surface morphology of RPC （reactive powder concrete） containing soil.

Composites of graphene and encapsulated silicon for practically viable high-performance lithium-ion batteries

A facile and scalable approach to synthesize silicon composite anodes has been developed by encapsulating Si particles via in situ polymerization and carbonization of phloroglucinol-formaldehyde gel, followed by incorporation of graphene nanoplatelets. As a result of its structural integrity, high packing density and an intimate electrical contact consolidated by the conductive networks, the composite anode yielded excellent electrochemical performance in terms of charge storage capability, cycling life and coulombic efficiency. A half cell achieved reversible capacities of 1,600 mAh·g-1 and 1,000 mAh·g-1 at 0.5 A·g-1 and 2.1 A·g-1, respectively, while retaining more than 70% of the initial capacities over 1,000 cycles. Complete lithium-ion pouch cells coupling the anode with a lithium metal oxide cathode demonstrated excellent cycling performance and energy output, representing significant advance in developing Si-based electrode for practical application in high-performance lithium-ion batteries.

Focuses of material science development in recent years

Materials science is an interdisciplinary field applying the properties of matter to various areas of science and engineering. This scientific field investigates the relationship between the structure of materials at atomic or molecular scales and their macroscopic properties. It incorporates elements of applied physics and chemistry. With significant media attention focused on nanoscience and nanotechnology in recent years, materials science has been propelled to the forefront at many universities. Materials science encompasses various classes of materials, including electronic materials, functional ceramics, magnesium, material and processes for flat-panel displays, eco/environmental materials, sustainable energy materials, transportation materials, electronic packaging materials, etc.