A mathematical model to predict surface roughness and pattern thickness in roll-to-roll gravure printed electronics

The roll-to-roll printing processes have recently been applied for the manufacturing of printed electronics due to their advantages, such as their high-throughput capabilities and low associated costs. In a roll-to-roll printing machine, a web or substrate is moved from an unwinding roll to a winding roll. During printing, the operating tension is important for correct substrate handling to prevent substrate defects, such as wrinkles, scratches and breaks. Accordingly, the operating conditions of the moving web can affect the quality of the printed pattern. In this study, a mathematical model has been developed to predict the thickness and surface roughness of printed patterns. Because the dynamics of roll-to-roll printing systems are complicated and non-linear, a statistical model is preferred. A full factorial method has been used with four independent variables: operating tension, print speed, ink viscosity and theoretical transfer volume. This model accurately predicted the surface roughness and thickness of the printed pattern.     

Tactile sensors based on conductive polymers

This paper presents results from a selection of tactile sensors that have been designed and fabricated. These sensors are based on a common approach that consists in placing a sheet of piezoresistive material on the top of a set of electrodes. We use a thin film of conductive polymer as the piezoresistive material. Specifically, a conductive water-based ink of this polymer is deposited by spin-coating on a flexible plastic sheet, giving it a smooth, homogeneous and conducting thin film. The main interest in this procedure is that it is cheap and it allows the fabrication of flexible and low cost tactile sensors. In this work, we present results from sensors made using two technologies. Firstly, we have used a flexible printed circuit board (PCB) technology to fabricate the set of electrodes and addressing tracks. The result is a simple, flexible tactile sensor. In addition to these sensors on PCB, we have proposed, designed and fabricated sensors with screen-printing technology. In this case, the set of electrodes and addressing tracks are made by printing an ink based on silver nanoparticles. The exhaustive characterization provides us insights into the design of these tactile sensors.     

Fabrication of wireless sensors on flexible film using screen printing and via filling

Wireless sensors are fabricated on flexible plastic films by means of screen printing and via-hole filling. The wireless sensors are battery free with data and power transmission functions. The sensors, fabricated on polyethylene terephtalate films, are designed based on RFID technology. Using an additive patterning process known as screen printing, metallization on polymer films is created. Both sides of a polymer film are printed with metallic patterns and connected with micro vias filled with conductive paste. One side of the film consists of printed electrical traces for discrete components like resistors and transistors that would be mounted onto it; the other side consists of a printed inductive coil used for wireless data and power transmission. The micro vias, which have a diameter of 120 μm, are formed by mechanical punching and filled with conductive silver paste. The size of one sensor unit is approximately 2 cm × 1.5 cm; an array of 4 × 7 sensor units are printed over an area of 15 cm × 15 cm on a PET film. Details of manufacturing processes, component assembly and functionality test are presented in this paper.     

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.     

Characterization of silver nanoparticle based inkjet printed lines

Inkjet of conductive patterns is a topic which already attracted much interesting research. Its importance arises from the ability to deposit electrical circuits on almost any kind of substrates. Understanding the controlling parameters to obtain lines with suppressed coffee stain effect still remains an important goal. The results reported here were obtained with a commercial nanoparticle based silver ink printed with a Dimatix 2800 printer. They show the effect of the printing parameters (drop spacing, substrate temperature, ink concentration and substrate type) on the 3D shape of straight lines. In particular it is shown that flat lines can be obtained at any ink concentration on the two different substrate types tested but at specific substrate temperature and drop spacing. Dependence of line cross-section area and line width on drop spacing is also analyzed.     

Realization of embedded capacitors using polymer matrix composites with barium titanate as high-k-active filler

Polymer matrix composites (PMC) with barium titanate as high-k-active filler have high potential in embedded capacitors within a printing circuit board (PCB) enabling high permittivity values and low loss factors. These PMCs allows for the use of established polymer processing techniques like screen printing and curing, which are compatible to the established PCB-materials and shaping processes. In this work a process chain, starting with a material optimization of the nano-sized barium titanate, dispersed in an unsaturated polyester-styrene reactive resin, and a further specific process development, will be presented. With respect to the optimization of the individual process steps the flow behaviour of the uncured composite, the polymerization process and the dielectric properties were characterized comprehensively. Using a composite with a barium titanate filler load of 74?wt% allows for a dielectric layer formation by a modified screen printing technique. After capacitor mounting and composite curing an initial capacity density of 13.3?pF/mm² could be achieved.     

CCD在双玻璃晒架的精密光学定位中的设计

随着电子工业的不断发展,对印制电路板的质量要求越来越高。传统销钉/孔定位方式已经不能适合现代生产的精密要求。CCD光学定位是全新的定位概念,设计了CCD光学定位系统的结构,实验验证了CCD光学对位精度可达到10μm,该指标明显优于传统定位方式的对位精度。     

A scalable manufacturing process for flexible active‐matrix e‐paper displays

Abstract— A scalable manufacturing process for fabricating active‐matrix backplanes on low‐cost flexible substrates, a key enabler for electronic‐paper displays, is presented. This process is based on solution processing, ink‐jet printing, and laser patterning. A multilayer architecture is employed to enable high aperture ratio and array performance. These backplanes were combined with E Ink electrophoretic media to create high‐performance displays that have high contrast, are bistable, and can be flexed repeatedly to a radius of curvature of 5 mm.     

丝网印刷技术的发展和在印制电路板中的应用

本文列举了近十年来网印技术的进步,对部分国产PCB印料作了较为详细的介绍。指出只有丝网印刷材料、设备和工艺的创新才能使其向高科技领域拓展,在PCB制造业中占有优势。     

A path planning algorithm for PCB surface quality automatic inspection

Journal of Intelligent Manufacturing - The surface quality inspection of industrial printed circuit board (PCB) is a vitally important link in its manufacturing process. To inspect surface defects...     

Microvias: the next generation of substrates and packages

Shrinking traces and spaces combined with a rising layer count eventually enlarge density, but most fabricators merely choose to shrink via size. Vias (conductive vertical paths or holes in any substrate) were previously drilled mechanically. With the prevalence of lasers, however, the focus has turned to microvias or build-up technologies. Microvias (miniature holes smaller than 150 μm in diameter) enable connections between different layers of a PCB. But how do microvias affect substrate or integrated circuit packaging? The author believes that this innovative technology will revolutionize PCB technology-a point he demonstrates by focusing on how microvias are made and their potential impact on PCB technology. Microvias will dominate the next generation of electronic products because they provide for increased density on a smaller substrate     

Preview control of web position in roll-to-roll printing using alignment patterns

In printed electronics systems, the roll-to-roll process is a next-generation process technology that may be applied to the production of various electronic products such as flexible electronic devices, solar cells, and display panels. The process allows for production at low unit cost and high speed. As a factor for improving the print quality, there are ink viscosity, printing speed, printing pressure, and alignment precision. Among these factors, alignment precision, a critical factor in the performance of an electronic circuit, is the accurate alignment of layers in a multi-layered structure. In our previous study, we suggested a measurement method for improving the alignment precision by using an optical pre-measuring device and an alignment pattern that is printed by roll-to-roll printing process. In the measuring system, when a web is transported in the web feed direction, the optical pre-measuring device measures the quantity of light reflected by the alignment pattern. A lateral position can be aligned accurately based on the measured signal. However, because the position is measured in advance in the web feed direction, it is not applicable to a real-time printing system, and when the lateral position is measured using the optical pre-measuring device, a lateral position error, that is generated by disturbances induced by tension acting on the web and the vibration of the motor, can be estimated. A motor driven linear translation stage for lateral direction is used to minimize the lateral position errors in roll-to-roll systems. In this paper, we propose a preview control system to reflect the measured lateral position error to the printing result at the appropriate time for improving the alignment precision in roll-to-roll printing. As a control method, using roll-to-roll model, the system of disturbance, lateral angle and lateral position can be expressed as a state-space equation. Based on this equation, a preview controller to find the optimal value of state and control error is designed in a similar method to the conventional preview control method used for the active suspension system of a vehicle. Then, the alignment results are verified using another optical measuring device of a web transport system.

     

Printing of polymer thin‐film transistors for active‐matrix‐display applications

Abstract— We present a process for active‐matrix flat‐panel‐display manufacture based on solution processing and printing of polymer thin‐film transistors. In this process, transistors are fabricated using soluble semiconducting, conducting, and dielectric polymer materials. Accurate definition of the transistor channel and other circuit components are achieved by direct ink‐jet printing combined with surface‐energy patterning. We have used this process to create 4800‐pixel 50‐dpi active‐matrix backplanes. These backplanes were combined with polymer‐dispersed liquid crystal to create the first ink‐jet‐printed active‐matrix displays. Our process is, in principle, environmentally friendly, low temperature, compatible with flexible substrates, cost effective, and advantageous for short‐run length and large display sizes. As well as polymer‐dispersed liquid crystal, this technology is applicable to conventional liquid‐crystal and electrophoretic display effects.     

边缘电场传感器测量金属衬底绝缘层厚度

针对金属衬底上的绝缘层,研究基于边缘电场传感器的厚度测量方法。位于同一平面的传感电极形成边缘场电容,边缘电场将穿透绝缘层,在衬底表面发生突变。本文用三电容模型分析了传感器的测量原理,衬底作为一个浮动电极分别与两个传感器电极构成平行极板电容,与边缘场电容共同构成传感电容。通过二维仿真讨论了电容结构参数对传感电容的影响。实验结果表明,边缘场电容传感器应用于金属衬底上的绝缘层测量时,表现出边缘场电容与平行板电容复合的特性,传感器灵敏度高。当绝缘层厚度相比电极长度较小时,电极的间距对传感器电容输出影响小。     

Fabrication of electrostatic MEMS microactuator based on X-ray lithography with Pb-based X-ray mask and dry-film-transfer-to-PCB process

Lithographie Galvanoformung Abformung (LIGA) is a promising approach for fabrication of high aspect ratio 3D microactuator for dual-stage slider in hard disk drive. However, this approach involves practically challenging X-ray lithography and structural transfer processes. In this work, electrostatic MEMS actuator is developed based on a LIGA approach with cost-effective X-ray lithography and dry-film-transfer-to-PCB process. X-ray lithography is performed with X-ray mask based on lift-off sputtered Pb film on mylar substrate and photoresist application using casting-polishing method. High quality and high aspect ratio SU8 microstructures with inverted microactuator pattern have been achieved with the interdigit spacing of ~5 μm, vertical sidewall and a high aspect ratio of 29 by X-ray lithography using the low-cost Pb based X-ray mask. A new dry-film-transfer-to-PCB is employed by using low-cost dry film photoresist to transfer electroplated nickel from surface-treated chromium-coated glass substrate to printed circuit board (PCB) substrate. The dry film is subsequently released everywhere except anchor contacts of the electrostatic actuator structure. The fabricated actuator exhibits good actuation performance with high displacement at moderate operating voltage and suitably high resonance frequency. Therefore, the proposed fabrication process is a promising alternative to realize low-cost MEMS microactuator for industrial applications.     

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．     

A precise position measurement system of roll-to-roll printing using burst alignment patterns

Microsystem Technologies - Printed electronics involve a process of creating electrical devices by printing with conductive ink on flexible substrates. This process is environmentally-friendly and...     

喷墨打印制备的SnO_2薄膜的气敏特性

简介了喷墨打印制备薄膜技术的优势与特点,配制了SnO2前驱溶液墨水,并利用该技术在金叉指氧化铝基片上喷镀SnO2前驱溶液墨水,而制得了SnO2气敏薄膜元件。利用XRD分析了SnO2薄膜的晶体结构。通过控制喷打墨水的次数,方便地控制了最终薄膜的厚度。并初步探讨了喷墨打印次数对最终薄膜元件性能的影响。当薄膜只喷打一次时,具有极高的电阻值,而且灵敏度比较低。而随着喷打次数的增加,即薄膜厚度的提高,薄膜电阻也随之降低,并对乙醇具有较好的气敏性能。     

A portable wireless body sensor data logger and its application in video capsule endoscopy

Due to the advancement of low power miniature electronic devices, there is growing interest of physiological data sensing and recording using wireless body sensor networks. The paper presents the design of a portable physiological data logger that includes rechargeable battery, wireless radio frequency and Bluetooth connectivity, and graphical display with touch screen capability. The target application is video capsule endoscopy. Image data are logged in micro SD cards which can be easily transferred to PC or Smartphone using SD card reader, USB interface or Bluetooth wireless link. The hardware design is general and can be used in various medical or industrial applications by changing only the firmware of the microcontroller. The design is prototyped in 109 × 107 × 20 mm printed circuit board (PCB). Tests with animal tissues have been conducted to demonstrate the performance advantages of the data logger. A demonstration of wireless heart pulse monitoring and data logging is also presented.     

Suitable properties of ink to create inkjet-printed surface-directed microchannels that utilize the pinning effect of a triple line on a rough surface

If microfluidic devices can be directly produced using printing techniques, the combination of microfluidics and printing techniques for other applications, such as printed electronics, will make all-printed highly-functionalized microfluidic devices possible. Therefore, we have made efforts to develop a technique for producing microfluidic devices using an inkjet printer. The microchannels that could be created using this technique were a kind of surface-directed channels that utilize the pinning effect of a triple line on a rough surface. In this study, we focused on what were the required properties of the printer ink during the wetting and drying processes of the ink. As a result, one of the properties required during the wetting process was that the advancing contact angle of the ink should be smaller than a certain value, which depended on the average volume of the ink drops ejected from the printhead and the number of drops per unit area. The receding contact angle should be smaller than about one third of each advancing angle. In addition, during the drying process, a small amount of surfactant added to the ink played a critical role in order to leave a continuous stain of the ink. As an application of this inkjet-printed channel, we also created a device for mixing aqueous solutions.