高性能嵌入电容元件用的最佳环氧-钛酸钡纳米复合物

概述了旨在获得高性能和可靠的嵌入电容元件的最佳环氧-钛酸钡（BaTiO3）纳米复合物。为了在高填充量下改善聚合物-陶瓷纳米复合物的可靠性，采用仲橡胶处理的环氧进行环氧基体的改性，在连续的原环氧相（海洋）中形成隔离的柔性区域（岛屿）。系统地评估了海洋-岛屿结构对嵌入电容元件的热机械性质，附着性和热应力可靠性的影响。最佳的橡胶处理的纳米复合物组成具有50以上的高介质常数，成功地通过了严格的热应力可靠性试验。大面积的薄膜电容器测得89MV／m的高击穿电压和约为1．9×10^-11A／cm^2的低漏电流。     

High dielectric constant polymer-ceramic (Epoxy varnish-barium titanate) nanocomposites at moderate filler loadings for embedded capacitors

Polymer-ceramic nanocomposites are the major candidate dielectrics for embedded capacitors. Due to the poor adhesion and poor thermal stress reliability at high filler loadings, commercially available polymer-ceramic composites can only achieve a maximum dielectric constant of ∼30. However, a high dielectric constant of ∼50–200 is required to make the layout area small enough for embedding applications. In this work, we systematically studied the material formulations in order to obtain a high dielectric constant (κ>50) at the lowest ceramic filler loading. It was found that material design and processing were critical. By modifying the epoxy matrix with a chelating agent and using bimodal fillers and a proper amount of dispersing agent, dielectric constants ∼50 were obtained at moderate filler loadings.     

Laser Micromachining of Barium Titanate $({hbox {BaTiO}}_{3})$-Epoxy Nanocomposite-Based Flexible/Rollable Capacitors: New Approach for Making Library of Capacitors

This paper discusses laser micromachining of barium titanate (BaTiO₃)-polymer nanocomposite thin films. In particular, recent developments on high-capacitance, large-area, thin, flexible, embedded capacitors are highlighted. A variety of barium titanate (BaTiO₃)-epoxy polymer nanocomposite-based flexible/rollable thin films ranging from 2 to 25 mum thick were processed on large-area substrates (330 mm times 470 mm, or 495 mm times 607 mm) by liquid coating processes. The electrical performance of composites was characterized by dielectric constant (Dk), capacitance, and dissipation factor (loss) measurements. Nanocomposites provided high capacitance density (10-100 nF/in²) and low loss (0.02-0.04) at 1 MHz. Scanning electron microscopy (SEM) micrographs showed uniform particle distribution in the coatings. Uniform mixing of nanoparticles in the epoxy matrix results in high dielectric (> 3 times 10⁷ V/m) and mechanical strengths (> 3700 PSI). Reliability of the capacitor was ascertained by thermal cycling. Capacitance change was less than 5% after baking at 140degC for 4 h, and 1100 cycles from -55degC to 125degC (deep thermal cycle). A frequency-tripled Nd:YAG laser operating at a wavelength of 355 nm was used for the micromachining study. The micromachining was used to generate arrays of variable-thickness capacitors from the nanocomposites. The resultant thickness of the capacitors depends on the number of laser pulses applied.     

Novel polymer-ceramic nanocomposite based on new concepts for embedded capacitor application (I)

A rapid growth of mixed-signal integrated circuits is driving the needs of multifunction and miniaturization of the component in electronics applications. Polymer-ceramic composites have been of great interest as embedded capacitor materials because they enabled companies to combine the processability of polymers with the high dielectric constant of ceramics. This paper presents the preparations and performance characterizations of novel polymer-ceramic nanocomposites based on new concepts for embedded capacitor application. First, metal particle nickel-filled nanocomposite with high dielectric constant was evaluated as a candidate for embedded capacitors. Two types of nickel particles were selected with the size of 400 and 150nm, respectively. With proper filler loading and highly dispersed, a high dielectric constant of over 90 was observed with a filler loading ratio of 60-vol%. Second, the surface modification of a barium titanate (BTO) particle was also attempted in nanocomposite. Phthalocyanine-coated BTO (Pc-coated BTO) was selected as filler to prepare the composite. Its dielectric constant was observed as over 80 at 1MHz, which was much higher than that of composite derived from commercial BTO. Last, in order to improve the processability of the nanocomposite, 4, 4'-diphenylmethane bismaleimide (BMI) was selected as a matrix polymer by the combination with polyamide (PA). Higher dielectric constant nanocomposite derived from PA/BMI and Pc-coat BTO was obtained, and its potential application towards embedded capacitors was also evaluated.     

Modeling the Electrical Conduction in Epoxy–BaTiO3 Nanocomposites

Epoxy–BaTiO₃ nanocomposites are widely used as the dielectric material in embedded planar capacitors. To maximize the effective dielectric constant of this nanocomposite, the loading of BaTiO₃ is kept as high as possible, but at high loadings of BaTiO₃ the magnitude of undesirable leakage current in the dielectric also increases. This paper investigates the conduction mechanism in epoxy–BaTiO₃ nanocomposites. Further, the effects of BaTiO₃ loading and the size of BaTiO₃ particles on the electrical conduction are investigated and also modeled. To investigate the conduction mechanism, capacitor structures (Cu/dielectric/Cu) with nanocomposite dielectric were fabricated using the colloidal process. The loading and size of BaTiO₃ particles were varied in the nanocomposite dielectric. Once the capacitor structures were fabricated, the leakage current was measured across the capacitor dielectric as a function of temperature and voltage. The leakage current data were checked for any consistency with the standard conduction models using regression analysis, and the dominant conduction mechanism was identified. Finally, the activation energy of the dominant conduction mechanism was trended as a function of BaTiO₃ loading and particle size both experimentally and theoretically.     

环氧/BaTiO3复合物埋入电容膜和电容膏

概述了环氧/BaTiO3复合物埋入电容膜和电容膏的开发,它们适用于PCB之类的有机基材内制造具有高介质常数和低误差的埋入电容.     

A precise numerical prediction of effective dielectric constant forpolymer-ceramic composite based on effective-medium theory

Nanostructure polymer-ceramic composite with high dielectric constant (ϵ_τ~90) has been developed for embedded capacitor application. This polymer-ceramic system consists of lead magnesium niobate-lead titanate (PMN-PT) ceramic particle and modified high-dielectric constant low-viscosity epoxy resin. In order to obtain precise prediction of effective dielectric constant of this composite, an empirical prediction model based on self-consistent theory is proposed. The electrical polarization mechanism and interaction between epoxy resin and ceramic filler has been studied. This model can establish the relevant constitutional parameters of polymer-ceramic composite materials such as particle shape, composition, and connectivity that determine the dielectric properties of the composite. This model is simpler, uses fewer parameters and its prediction compares better with experiment (error <10%). The precision and simplicity of the model can be exploited for predictions of the properties and design of nanostructure ferroelectric polymer-ceramic composites. The effective-medium theory (EMT) has been proved a good tool to predict effective properties of nanocomposites     

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.     

Preparation and Dielectric Characteristics of Semitransparent CoFe2O4–P(VDF-TrFE) Nanocomposite Films

Polymer–ceramic nanocomposites play an important role in embedded capacitors. However, polymer–ceramic dielectrics are limited for commercial applications due to their low transmittance, poor adhesion, and poor thermal stress reliability at high filler loadings. Thus, materials design and processing is critical to prepare films with improved dielectric properties and low filler loading. In this work, we use a spin coating-assisted method to fabricate poly(vinylidene fluoride-co-trifluoroethylene) [P(VDF-TrFE)]–CoFe₂O₄ (CFO) nanocomposite films. Magnetic CFO nanoparticles in the size range of 10 nm to 40 nm were successfully synthesized using a hydrothermal process. The dispersion of the nanoparticles, the dielectric properties, and the transmittance of the nanocomposite films were studied. The dielectric constant of the nanocomposite films increased by about 45% over the frequency range of 100 Hz to 1 MHz, compared with that of pristine P(VDF-TrFE) film. Optical measurements indicated that the transmittance of the films remains above 60% in the visible range, indicating a relatively low content of CFO in the polymer matrix. Our experimental results suggest that spin coating-assisted dispersion may be a promising route to fabricate dielectric polymer–ceramic nanocomposite films of controllable thickness.     

Embedded Capacitors in Printed Wiring Board: A Technological Review

This paper reviews the technology of embedded capacitors, which has gained importance with an increase in the operating frequency and a decrease in the supply voltage of electronic circuits. These capacitors have been found to reduce the number of surface-mount capacitors, which can assist in the miniaturization of printed wiring boards. This paper describes various aspects of embedded capacitors, such as electrical performance, available dielectric materials, manufacturing processes, and reliability. Improvement in electrical performance is explained using a cavity model from the theory of microstrip antennas. The advantages and disadvantages of dielectric materials such as polymers, ceramics, polymer–ceramic composites, and polymer–conductive filler composites are discussed. Various manufacturing techniques that can be used for the fabrication of embedded capacitors are also discussed. Embedded capacitors have many advantages, but failure of an embedded capacitor can lead to board failure since these capacitors are not reworkable. The effect of various environmental stress conditions on the reliability of embedded capacitors is reviewed.     

High-Performance MIM Capacitors Using HfLaO-Based Dielectrics

Metal-insulator-metal (MIM) capacitors fabricated with (8%) La-doped HfO₂ single layer as well as HfLaO/ LaAlO₃/HfLaO multilayer dielectric stack are demonstrated. While the La-doped HfO₂ single layer is crystallized at 420^°C annealing, HfLaO/LaAlO₃/HfLaO multilayer dielectric stack remains amorphous. A high dielectric-constant value of 38 can be obtained when 8% La-doped HfO₂ is crystallized into cubiclike structure. However, it is observed that the linearity of MIM capacitor is degraded upon crystallization. The multilayer film has lower average dielectric constant but shows low quadratic voltage linearity of less than 1000 ppm/V² up to a capacitance density of 9 fF/?m² . It is observed that the HfLaO single-layer MIM is suitable for the applications with requirements of high capacitance density and robust reliability, while the multilayer MIM is suitable for a precision circuit.     

Effects of ${hbox{CNT/BaTiO}}_{3}$ Composite Particles Prepared by Mechanical Process on Dielectric Properties of Epoxy Hybrid Films

A new type of composite filler mechanically treated with multi-walled carbon nanotubes (MWNTs) and (BT) particles was prepared to produce higher dielectric properties in the composite. The hybrid film fabricated by incorporating these composite fillers in an epoxy matrix had a high dielectric constant and similar dielectric loss as compared to the composite which contained neat BT particles. The dielectric properties of these hybrid films were found to be dependent on both the content of MWNTs and mechanical processing time. Results suggest that this novel hybrid film composed of the composite filler and the epoxy matrix can be used for embedded capacitor material.     

嵌入电容膜（ECF）用的环氧／SrTiO3复合物

概述了高频用途的环氧／SrTiO3复合物嵌入电容膜（ECF）的开发。采用变化SrTiO3粒子填料的3种不同的SrTiO3粉,测量环氧／SrTiO3复合物嵌入电容膜的介质常数。试验数据符合判断环氧／SrTiO3复合物ECF中的SrTiO3粉的有效介质常数的Lichtenecker方程。应用矩形谐振腔法测量环氧／SrTiO3复合物ECF在千兆赫范围（1GHz、10GHz）的介质常数。在千兆赫频率范围内环氧／SrTiO3复合物ECF的介质常数几乎稳定。因此环氧／SrTiO3复合物ECF可以有效地应用于高频用途中。     

Novel Integration of Metal–Insulator–Metal (MIM) Capacitors Comprising Perovskite-type Dielectric and Cu Bottom Electrode on Low-Temperature Packaging Substrates

In this letter, a novel integration scheme, for metal-insulator-metal capacitors comprising perovskite-type dielectrics and Cu-based bottom electrodes, has been demonstrated on low-temperature FR4 packaging substrates. Cu oxidation during dielectric deposition and postannealing is completely avoided by a dielectric-first process flow with Ti as oxygen-getter. By using evaporated barium strontium titanate as capacitor dielectric, a maximum capacitance density (~1250 nF/cm² at 100 kHz) and moderate leakage current (< 4 times 10^-5 A/cm² at 2 V) have been achieved with rapid thermal annealing at 700degC. Higher temperature leads to dielectric degradation. Combined with advanced deposition techniques, this integration scheme enables realization of high-performance embedded capacitors that can be integrated with printed circuit board technology.     

Good High-Temperature Stability of TiN/ Al2O3/WN/TiN Capacitors

For the first time, good thermal stability up to an annealing temperature of 1000degC has been demonstrated for a new TiN/Al₂O₃/WN/TiN capacitor structure. Good electrical performance has been achieved for the proposed layer structure, including a high dielectric constant of ~ 10, low leakage current of 1.2times10^-7 A/cm² at 1 V, and excellent reliability. A thin WN layer was incorporated into the metal-insulator-metal capacitor between the bottom TiN electrode and the Al₂O₃ dielectric suppressing of interfacial-layer formation at Al₂ O₃/TiN interfaces and resulting in a smoother Al₂O₃/TiN interface. This new layer structure is very attractive for deep-trench capacitor applications in DRAM technologies beyond 50 nm.     

Colloidal processing of polymer ceramic nanocomposite integral capacitors

Polymer ceramic composites form a suitable material system for low temperature fabrication of embedded capacitors appropriate for the MCM-L technology. Improved electrical properties such as permittivity can be achieved by efficient filling of polymers with high dielectric constant ceramic powders such as lead magnesium niobate-lead titanate (PMN-PT) and barium titanate (BT). Photodefinable epoxies as the matrix polymer allow fine feature definition of the capacitor elements by conventional lithography techniques. The optimum weight percent of dispersant is tuned by monitoring the viscosity of the suspension. The dispersion mechanism (steric and electrostatic contribution) in a slightly polar solvent such as propylene glycol methyl ether acetate (PGMEA) is investigated from electrophoretic measurements. A high positive zeta potential is observed in the suspension, which suggests a strong contribution of electrostatic stabilization. By optimizing the particle packing using a bimodal distribution and modified processing methodology, a dielectric constant greater than 135 was achieved in PMN-PT/epoxy system. Suspensions are made with the lowest PGMEA content to ensure the efficiency of the dispersion and efficient particle packing in the dried film. Improved colloidal processing of nanoparticle-filled epoxy is a promising method to obtain ultra-thin capacitor films (<2/spl mu/m) with high capacitance density and improved yield. Capacitance of 35 nF/cm/sup 2/ was achieved with the thinnest films (2.5-3.0 /spl mu/m).     

Highly reliable non-conductive adhesives for flip chip CSP applications

Non-conductive adhesives (NCA), widely used in display packaging and fine pitch flip chip packaging technology, have been recommended as one of the most suitable interconnection materials for flip-chip chip size packages (CSPs) due to the advantages such as easier processing, good electrical performance, lower cost, and low temperature processing. Flip chip assembly using modified NCA materials with material property optimization such as CTEs and modulus by loading optimized content of nonconductive fillers for the good electrical, mechanical and reliability characteristics, can enable wide application of NCA materials for fine pitch first level interconnection in the flip chip CSP applications. In this paper, we have developed film type NCA materials for flip chip assembly on organic substrates. NCAs are generally mixture of epoxy polymer resin without any fillers, and have high CTE values un-like conventional underfill materials used to enhance thermal cycling reliability of solder flip chip assembly on organic boards. In order to reduce thermal and mechanical stress and strain induced by CTE mismatch between a chip and organic substrate, the CTE of NCAs was optimized by filler content. The flip chip CSP assembly using modified NCA showed high reliability in various environmental tests, such as thermal cycling test (-55/spl deg/C/+160/spl deg/C, 1000 cycle), high temperature humidity test (85/spl deg/C/85%RH, 1000 h) and high temperature storage test (125/spl deg/C, dry condition). The material properties of NCA such as the curing profile, the thermal expansion, the storage modulus and adhesion were also investigated as a function of filler content.     

Polymer-ceramic nanocomposite capacitors for system-on-package (SOP) applications

This work focuses on optimizing the dispersion of nanosized ceramic particles for achieving higher dielectric constant, thereby higher capacitance density in polymer/ceramic nanocomposites. It has been observed that high solids loading leads to entrapment of porosity in the microstructure which lowers the effective dielectric constant of the films. The amount of solvent in the suspension and the speed at which spin coating was performed were found to impact the dielectric constant of high filler content nanocomposites. The interplay between the rheological properties of the suspension and processing parameters such as solvent content and coating speeds and its impact on the dielectric properties of the film are discussed. Porosity of thin film composites was measured for the first time to study the impact of these processing parameters. Powders of different particle sizes were mixed to obtain bimodal particle size distribution in order to increase the packing density of the composite. Packing density was improved by modifying the dispersion methodology. A nanocomposite with dielectric constant as high as 135 was obtained for the first time in the low-cost printed wiring board compatible epoxy system. A capacitance densities of /spl sim/35 nF/cm/sup 2/ on a nominal 3.5 micrometer films was achieved on PWB substrates with high yield. The manufacturability of these formulated nanocomposites and their applications as decoupling capacitors have been tested using a large area (300 mm /spl times/ 300 mm) system-on-package (SOP) chip-to-chip communication test vehicle.     

A Novel Nanocomposite With Photo-Polymerization for Wafer Level Application

A novel nanocomposite photo-curable material which can act both as a photoresist and a stress redistribution layer applied on the wafer level was synthesized and studied. In the experiments, 20-nm silica fillers were modified by a silane coupling agent through a hydrolysis and condensation reaction and then incorporated into the epoxy matrix. A photo-sensitive initiator was added into the formulation which can release cations after ultraviolet exposure and initiate the epoxy crosslinking reaction. The photo-crosslinking reaction of the epoxy made it a negative tone photoresist. The curing reaction of the nanocomposites was monitored by a differential scanning calorimeter with the photo-calorimetric accessory. The thermal mechanical properties of photo-cured nanocomposites thin film were also measured. It was found that the moduli change of the nanocomposites as the filler loading increasing did not follow the Mori-Tanaka model, which indicated that the nanocomposite was not a simple two-phase structure as the composite with micron size filler. The addition of nano-sized silica fillers reduced the thermal expansion and improved the stiffness of the epoxy, with only a minimal effect on the optical transparency of the epoxy, which facilitated the complete photo reaction in the epoxy.     

Reduced Temperature Coefficient of Capacitance (TCC) of Embedded Capacitor Films (ECFs) for Organic Substrates using SrTiO3 and Multifunctional Epoxy

Epoxy/ceramic composites have attracted great interest as embedded capacitor materials, mainly due to the process compatibility of epoxy with printed circuit boards (PCBs). However, one of the potential problems of epoxy/ceramic composites is the temperature dependence of their dielectric properties. This study focuses mainly on reducing the temperature coefficient of capacitance (TCC) of epoxy/ceramic composites using multifunctional epoxy and SrTiO₃ powder. The TCC of an epoxy/ceramic composite mainly depends on the properties of its epoxy and ceramic powder. Using multifunctional epoxy, the epoxy resin showed two glass-transition temperatures, resulting in a lower dimensional change after the first glass-transition temperature. Additionally, the TCC of epoxy/SrTiO₃ ECFs can be decreased by increasing the SrTiO₃ powder content. As a result, reduced TCC of epoxy/ceramic composite capacitors using a multifunctional epoxy and SrTiO₃ powder was successfully demonstrated for embedded capacitors in organic substrates.