Development of new polymer�CBaTiO3-composites with improved permittivity for embedded capacitors

A series of commercially available nanosized barium titanates has been investigated with respect to their use as high-k-ceramic filler in polymer based composites with improved dielectric properties. The thermal treatment of the barium titanate powders at 1,000°C causes a significant increase of the composite’s permittivity. X-ray diffraction experiments prior and after heat treatment revealed that the barium titanate with smallest particle size and the largest specific surface area possesses the thermodynamically unstable cubic phase. In case of the other investigated barium titanates the crystal lattice is distorted. Thermal treatment induces the phase change into the tetragonal one and crystal lattice relaxation enabling higher permittivity values. Composites with a solid load around 78 wt% with a bimodal particle size distribution show high permittivities around 50 and a low loss factor around 5‰ suitable for the realization of embedded capacitors via screen printing or tape casting.     

Dielectric property improvement of polymer-nanosized strontium titanate-composites for applications in microelectronics

With respect to applications in microelectronics the frequency and temperature dependent dielectric properties of a series of polymer-based composites, consisting of a thermally curable unsaturated polyester-styrene resin and nanosized strontium titanate filler, have been characterized. Following earlier investigations targeting an improvement of dielectric properties the impact of a thermal treatment of the dielectric filler on the resulting composite properties was determined. In case of composites containing 55 wt% strontium titanate heat treatment at 1,000°C increases the permittivity by almost 25% and lowers the loss factor value by a factor of almost 10 due to grain growth and larger crystallite sizes.     

微压电复合材料超声波探测器的制备及应用

基于微细加工工艺,设计并制备了一种指向性良好的压电复合材料的超声波探测器。该探测器由压电振子、阻尼器、中继板和特高频（UHF）连接器构成。压电振子由4×4个（80μm×80μm×130μm）（长×宽×高）的锆钛酸铅（PZT）压电柱状阵列及阵列缝隙填充环氧树脂而构成。当压电振子施加高频交流电压时,柱状PZT阵列产生纵向伸缩运动,从而产生超声波并向介质辐射。作为填充材料的环氧树脂,能够吸收掉因柱状PZT阵列其他方向振动而引起的噪声,使探测器在纵向上能产生指向性良好的超声波,从而提高了该探测器的灵敏度。测试结果表明,该微压电探测器指向性好,灵敏度高,精度高和抗干扰性好,可应用在泥沙的含水量测量中。     

Quantum dots printing paste for display backlights: Preparation,characterization, and applications

Quantum dots (QDs) are one kind of photoluminescent materials with excellent properties, such as adjustable spectrum, narrow full width at half maximum (FWHM), and high color gamut. In this paper, a photoluminescent QDs printing paste suitable for light guide dots array applied in the backlight for liquid crystal display (LCD) was presented. The QDs printing paste was first prepared and characterized with different kinds of solvents. Then, triphenyl phosphite (TPP), a kind of antioxygen, was added into the QDs printing paste to improve the stability of the QDs printing paste. Finally, a QDs light guide plate (LGP) was fabricated by screen printing with QDs printing paste added with silicon dioxide (SiO₂) light scattering particles. The color gamut of QDs LGP arrived 131.6%NTSC due to light scattering interaction between blue LED, red QDs, green QDs, and SiO₂ particles. The results showed that the QDs-chloroform printing paste had uniform light output and the highest photoluminescent peak intensity. Therefore, the composite screen printing paste has wide application prospects in the backlight of LCD, with the advantages of simple process, high production efficiency, and low cost.     

Fabrication of the plastic component for photonic crystal using micro injection molding

In this decade, many techniques have been introduced to fabricate photonic crystal in optical applications. Most of the processes used to fabricate the photonic crystal are time consuming and not cost effective. This study demonstrates an efficient method to fabricate photonic crystals. A polymer-based photonic crystal slab has been developed by embedding mixture with a high dielectric constant. Photonic crystals have patterned structures in which periodicity of dielectric properties can manipulate electromagnetic waves. The operation wavelength is about half of the characteristic dimension. Technique of injection molding is applied to make polymer parts with the photonic crystal pattern. Then mixture of barium titanate powder and epoxy is embedded on the patterned structure of the polymer part. The contrast of dielectric coefficients between mixture and polymer can constitute a structure with some photonic band gap. By means of polymer processing, mass production of photonic crystal devices like optical switch, optical waveguide, optical filter and so forth can be realized in a cost effective way.     

基于改进粒子群算法的多机器多任务3D打印智能调度方法

针对批量3D打印成本高,多机器多任务的3D打印批次调度复杂的问题,建立以最小单位体积平均成本为目标的优化模型,并提出一种基于改进粒子群算法的智能调度方法求解该模型;首先,分析打印工场、生产流程,构建3D打印单位体积平均成本模型;之后基于改进粒子群算法,以单位体积平均成本为适应度,以调度序列为粒子的位置信息,采用十进制顺序二维编码方式表示问题的解,并在更新策略上应用线性递减权值的动态惯性因子来调整全局与局部的搜索能力;算法迭代后,得到目标函数最优值及对应解集;经实验算例结果表明,该方法较单独打印加工的单位体积平均成本降低了0.101 3GBP/cm3,有效地降低工厂生产的总成本,提高了3D打印机的利用效率。     

太阳电池超细栅电极喷印控制系统设计与实现

针对传统丝网印刷技术制造太阳电池金属化栅极容易造成基材破损,且制造的栅极精度和高宽比很难提高的问题,采用喷墨技术直接将纳米银墨水打印到太阳电池基材上实现栅极金属化,并设计实现了太阳电池栅极喷印样机系统．样机系统通过USB模块实现高速数据通信;两组动态随机存储器（SDRAM）内存模块构成乒乓操作,实现不间断打印;喷印控制模块采用现场可编程门阵列（FPGA）产生喷头复杂时序波形和压电驱动波形．基于流体体积法建立了微液滴喷射模型,研究了微滴喷射机制及压电驱动波形幅值对微液滴尺寸、速度一致性的影响,并进行实验验证．通过优化喷印分辨率和在线固化温度进行系统测试,结果表明,多晶硅硅片固化温度80 ℃条件下,随着喷印层数的增加,栅极高度线性增加,喷印一层大约增高0.5 μm,栅极宽度基本维持在35～40 μm,打印层数60～80层时,形成三维形貌均匀的具有高“高宽比”的栅极．     

Process study and optimization for fabrication of poly‐Si thin‐film transistors on plastic substrates

Abstract— A complete poly‐Si thin‐film transistor (TFT) on plastic process has been optimized to produce TFT arrays for active‐matrix displays. We present a detailed study of the poly‐Si crystallization process, a mechanism for protecting the plastic substrate from the pulsed laser used to crystallize the silicon, and a high‐performance low‐temperature gate dielectric film. Poly‐Si grain sizes and the corresponding TFT performance have been measured for a range of excimer‐laser crystallization fluences near the full‐melt threshold, allowing optimization of the laser‐crystallization process. A Bragg reflector stack has been embedded in the plastic coating layers; its effectiveness in protecting the plastic from the excimer‐laser pulse is described. Finally, we describe a plasma pre‐oxidation step, which has been added to a low‐temperature (<100°C) gate dielectric film deposition process to dramatically improve the electrical properties of the gate dielectric. These processes have been integrated into a complete poly‐Si TFT on plastic fabrication process, which produces PMOS TFTs with mobilities of 66 cm² /V‐sec, threshold voltages of ?3.5 V, and off currents of approximately 1 pA per micron of gate width.     

All‐additive ink‐jet‐printed display backplanes: Materials development and integration

Abstract— Methods used to deposit and integrate solution‐processed materials to fabricate TFT backplanes by ink‐jet printing are discussed. Thematerials studied allow the development of an all‐additive process in which materials are deposited only where their functionality is required. The metal layer and semiconductor are printed, and the solution‐processed dielectric is spin‐coated. Silver nanoparticles are used as gate and datametals, the semiconductor used is a polythiophene derivative (PQT‐12), and the gate dielectric is an epoxy‐based photopolymer. The maximum processing temperature used is 150°C, making the process compatible with flexible substrates. The I_ON/I_OFF ratio was found to be about 10⁵?10⁶, and TFT mobilities of 0.04 cm²/V‐sec were obtained. The influence of surface treatments on the size and shape of printed features is presented. It is shown that coffee‐stain effects can be controlled with ink formulation and that devices show the expected pixel response.     

浅谈光盘丝网印刷制版技术

光盘丝网印刷是整个光盘生产过程中的一个重要环节,而好的印刷质量与高质量的网版是密切相关的。本文从绷网张力、网框选用、制网过程各环节控制等探讨了高质量网版制作的要点。     

Manufacturing an environmentally friendly PCB using existing industrial processes and equipment

This paper investigates the possibility of utilising an additive screen printing process with conductive ink and adhesive together with a degradable substrate to identify whether this process offers a viable alternative to current subtractive methods of PCB manufacture. Existing manufacturing equipment and production process were adopted in order to establish the compatibility of a sustainable and environmental friendly PCB with these processes. Experimental trials have shown that by using a stainless steel stencil 150 mm thick in conjunction with an MPM Ultraprint machine with a printing speed of 89 mm/s, a squeegee pressure of 0.97 bar and a downstop of 1.9 mm successful printing of the electrically conductive adhesive was achieved. It was also shown that the substrate was compatible with electronic placement technology and convection oven. Comparisons of the electronic assemblies to an industrial IPC standard illustrated that it is possible to develop a circuit, which is deemed acceptable under this standard. It can be concluded therefore that a screen printed conductive ink pattern, when printed on a degradable substrate can offer a viable alternative to current printed circuit boards and can be manufactured using existing technology and manufacturing processes.     

Experimental study on use of nickel powder-filled Portland cement-based composite for fabrication of piezoresistive sensors with high sensitivity

Nickel powder-filled Portland cement-based composite was prepared by adding nickel powder as functional filler into conventional Portland cement-based materials, and piezoresistive sensors were fabricated by embedding four loop electrodes in the nickel powder-filled Portland cement-based composite. The relationship between the fractional change in electrical resistivity and the stress/strain of piezoresistive sensors was established for the compressive stress and was found to be in the range from 0 to 12.5 MPa. Experimental results indicate that the electrical resistivity of nickel powder-filled Portland cement-based composite under uniaxial compression decreases by 62.6144% within elastic regime, which justifies the use of this composite in the fabrication of piezoresistive sensors with high sensitivity to stress and sensitivity to strain (gauge factor). The sensitivity of piezoresistive sensors to compressive stress is higher than 0.050092 MPa^?1 and goes up to 0.123648 MPa^?1. The gauge factor of piezoresistive sensors is higher than 895.450 and goes up to 1929.500. It is therefore concluded that the newly developed piezoresistive sensors have a high sensitivity to stress/strain, and they can be used for measurement of stress/strain or force/deformation.     

Modeling and optimization of stencil printing operations: A comparison study

This paper presents a comparison study for the optimization of stencil printing operations using hybrid intelligence technique and response surface methodology (RSM). An average 60% of soldering defects are attributed to solder paste stencil printing process in surface mount assembly (SMA). The manufacturing costs decrease with increasing first-pass yield in the stencil printing process. This study compares two hybrid intelligence approaches with RSM as methods of solving the stencil printing optimization problem that involves multiple performance characteristics. The optimization process is threefold. A data set obtained from an experimental design following data preprocessing process provides an accurate data source for RSM study and training neural networks to formulate the nonlinear model of the stencil printing process with/without combining multiple performance characteristics into a single desirability value, followed by a genetic algorithm searching the trained neural networks for obtaining the optimal parameter sets. The empirical defect-per-million-opportunities (DPMO) measurements demonstrate that the two hybrid intelligence methods can provide satisfactory performance for stencil printing optimization problem.     

基于BTO／CNTs复合压电薄膜制备

介绍了一种新型的钛酸钡／碳纳米管（BTO／CNTs）压电薄膜的制备方法及其特性研究,利用BTO纳米颗粒、CNTs和聚二甲基硅氧烷（PDMS）作为原材料,采用改进的sol—gel法制备出厚度均匀的复合薄膜,使用油浴极化法在一定条件下对复合薄膜极化。并利用SEM表征制备复合薄膜的掺杂效果,发现CNTs的加入加快了电子的转移速率。在周期性的外力作用下,发现其电压输出波形符合阻尼振荡模型,并测试不同配比下复合薄膜的压电电压输出,得出最佳BTO／CNTs质量比为10：l时,薄膜的输出电压最高可达4V。     

Saliency‐Preserving Slicing Optimization for Effective 3D Printing

We present an adaptive slicing scheme for reducing the manufacturing time for 3D printing systems. Based on a new saliency‐based metric, our method optimizes the thicknesses of slicing layers to save printing time and preserve the visual quality of the printing results. We formulate the problem as a constrained ?₀ optimization and compute the slicing result via a two‐step optimization scheme. To further reduce printing time, we develop a saliency‐based segmentation scheme to partition an object into subparts and then optimize the slicing of each subpart separately. We validate our method with a large set of 3D shapes ranging from CAD models to scanned objects. Results show that our method saves printing time by 30–40% and generates 3D objects that are visually similar to the ones printed with the finest resolution possible.     

AC-pulse modulated electrohydrodynamic jet printing and electroless copper deposition for conductive microscale patterning on flexible insulating substrates

This paper presents a novel micro-manufacturing method for fabrication of electrical features and patterns on highly insulating substrates and flexible substrates based on high-resolution AC-pulse modulated electrohydrodynamic jet (e-jet) printing of silver nanoink as seed layer followed by electroless copper deposition. Traditional ink jet printing method is limited in printing resolution which is determined by dimension of printing nozzle and dimension of droplets. Traditional e-jet printing has the disadvantage of residual charge problem especially for highly insulating substrates which cannot dredge remained charge of printed droplets, resulting in distorted electrostatic field and low printing controllability. Meanwhile, for printing of liquid phase ink, feature resolution contradicts with the required thickness, which is a key factor of conductivity of printed patterns. In this paper, a novel AC-modulated e-jet printing technique is applied to neutralize charges on substrates by switching polarity of consequent droplets for direct printing of high-resolution conductive silver patterns on insulating substrates. Electroless copper deposition is introduced in the fabrication process to solve the thickness problem of the resulting features. Variables of fabrication process, including amplitude and frequency of AC-pulsed voltage, plotting speed, curing temperature, number of layers, concentration of solution for copper growth, were identified to achieve reliable and conductive printed patterns. Sub-20 µm silver tracks with resistivity about 3.16 times of bulk silver were successfully fabricated. We demonstrated that ac-pulse modulated e-jet printing followed by electroless copper deposition can produce high resolution conductive patterns with improved thickness on insulating substrates and flexible substrates, which can be applied to direct printing and micro scale patterning for flexible electronics and wearable devices applications.     

聚合物纳米电介质材料研究进展及其在埋入式无源元件中的应用概述

聚合物纳米电介质材料由于其出色的机械加工特性、电可调制特性已成为当今高密度封装技术等诸多学科的前沿领域。通过在聚合基体中引入高介电陶瓷或纳米导电颗粒形成具有高介电常数的复合材料,并通过印刷电路板(Printed Circuit Board,PCB)制备工艺内置于PCB基板内部形成埋入式元件(电容、电感及其他无源元件),这已经在电子系统小型化方面显示出巨大的应用前景。文章综述了高介电纳米聚合物复合材料领域近年来的研究进展,探讨了聚合物纳米复合材料在埋入式电容器、电感器中的应用及埋入式无源滤波器的设计方法、制备工艺以及复合材料的电磁特性对埋入式元件电学性能的影响。     

Adhesive wafer bonding with photosensitive polymers for MEMS fabrication

Adhesive wafer bonding is a technique that uses an intermediate layer (typically a polymer) for bonding two substrates. The main advantages of using this approach are: low temperature processing (maximum temperatures lower than 400°C), surface planarization and tolerance to particles contamination (the intermediate layer can incorporate particles with the diameter in the layer thickness range). The main bonding layers properties required by a large field of applications/designs can be summarized as: isotropic dielectric constants, good thermal stability, low Young’s modulus, and good adhesion to different substrates. This paper reports on wafer-to-wafer adhesive bonding using SINR^TM polymer materials. Substrate coating process as well as wafer bonding process parameters optimization was studied. Statistical analysis methods were used to show repeatability and reliability of coating processes. Features of as low as 15 μm size were successfully resolved by photolithography and bonded. An unique megasonic-enhanced development process of the patterned film using low cost solvent was established and proven to exceed standard development method performance.     

A new control method for the relative dielectric constant of 1–3 piezoelectric composites realized with the LIGA process

 A plasma treatment for controlling the relative dielectric constant (ɛ_r) of fine-scale lead zirconate titanate (PZT) rods was developed. This new method made it easy to control ɛ_r of 1-3 piezoelectric composites, which were made up of fine-scale PZT rods in epoxy resin. The PZT rods were fabricated using the LIGA process, realizing an array of PZT rods with a cross section, height and volume fraction of 25 μm square, 250 μm and 25%, respectively. The new method consists of a plasma treatment applied before sintering of the PZT rods. By controlling the output RF power and duration of the plasma treatment, ɛ_r could be controlled between 250 and 400. Although extended plasma etching reduced ɛ_r, there were no changes in the piezoelectric properties and no defects in the sintered body. The ability to control ɛ_r of piezoelectric composites allows good electrical impedance matching with the electric circuit of diagnostic systems, thereby reducing signal transmission losses. Changing ɛ_r by varying the piezoelectric material or the sintering conditions requires lengthy process optimization. In contrast, controlling ɛ_r to establish a good impedance match can be done relatively easily with this new plasma technique because the piezoelectric properties are not affected.