Chip on paper technology utilizing anisotropically conductive adhesive for smart label applications

Smart labels are a new generation of low cost transponders consisting of a transponder chip and a flexible type of antenna. Applying a flip chip assembly technology yields a new generation of low cost radio frequency identification (RFID) system that is a paper-thin smart label. Anisotropically conductive adhesive (ACA) is utilized to attach a flip chip onto a paper substrate to form the BiStatix RFID tag. Unlike bar codes, which are passive tags, smart labels can dynamically transmit and receive information to help identify, track and route packages remotely. The concept of flipping or inverting a silicon chip to be mounted on a paper substrate offers distinct advantages and enables achieving the cost and performance goals of this new product technology.Significant process development and reliability assessment was required to develop this smart label application. This paper discusses the process development and reliability assessment that was completed to achieve a low cost flip chip on paper assembly process. The various characteristics of ACA made it an enabling technology for this smart label application. A bare (unbumped) flip chip––without a dielectric layer and conductive polymer bumps––was aligned and placed on the paper substrate with compressive force. A thin layer of anisotropically conductive adhesive was used to attach the IC chip to the conductive ink antenna on the paper substrate. The conductive adhesive underfills and cures in only seconds. Advantages of this environmentally preferred process include the elimination of additional curing processes and reduced equipment requirements as well as the reduction of total IC packaging thickness.     

纸基RFID标签天线印刷工艺参数的优化试验

材料与制作工艺造成的成本过高是RFID标签普及化应用的障碍。应用导电银浆与丝网印刷技术,可以解决RFID标签的低成本化问题。本文以丝网印刷技术在纸基材上印刷导电银浆而制作出RFID标签天线,研究了丝网印刷天线的工艺参数,讨论了工艺参数对制作RFID标签性能的影响,并通过优化试验对刮板施加给网版的压力,印刷速度,导电银浆固化温度与时间等制作工艺参数进行优化,得出最佳工艺参数,并制作出满足电阻特性的RFID标签天线。     

Investigation of a Biocompatible Polyurethane-Based Isotropically Conductive Adhesive for UHF RFID Tag Antennas

As a candidate dispersant for silver-based isotropically conductive adhesives (ICAs), polyurethane (PU) is an environmentally benign material that can withstand a high deformation rate and that exhibits excellent reliability. In this work we investigated methyl ethyl ketoxime (MEKO) blocked isophorone diisocyanate (IPDI) and MEKO blocked hexamethylene diisocyanate (HDI) as dispersant materials, and we characterize the electrical conductivity, mechanical properties, and reliability of these PU-based ICAs with silver-flake filler content ranging from 30 wt.% to 75 wt.%. Results of temperature–humidity testing (THT) at 85°C and 85% relative humidity (RH) and thermal cycling testing (TCT) at −40°C to 125°C show that these ICAs have excellent reliability. Our experimental results suggest that the MEKO blocked PU dispersants are suitable for preparing ultralow-cost, flexible, high-performance ICAs for printing antennas for ultrahigh-frequency radiofrequency identification (RFID) tags. These tags can potentially be used for identifying washable items and food packaging.     

Inkjetting dielectric layer for electronic applications

Printed electronics is expected to increase its market share significantly in near future. The emerging applications include e.g. display applications, RFID tags, and photovoltaic applications. A benefit of printing is the additive character of the process, which means that material is deposited only the amount that is needed. Digital printing increases flexibility of the process, because circuits are manufactured directly from a digital file, which removes need of fixed masks or patterned screens for each layout. Formation of a multilayer circuitry requires printing of conductive and insulative layers. This paper focuses on printing of a dielectric layer with an inkjet printer. Six sigma DMAIC approach was applied during the process characterization and analysis. The study began by defining the process parameters and evaluating their importance to the outputs. Highest rated parameters were taken into consideration and a design of experiments was established. Measured values were analyzed and it was observed which parameters had the highest effect on the outputs. The results were further verified and it was observed that electrically the printed structures were successful.     

Chipless RFID tags fabricated by fully printing of metallic inks

This paper reviews recent advances in fully printed chipless radio frequency identification (RFID) technology with special concern on the discussion of coding theories, ID generating circuits, and tag antennas. Two types of chipless tags, one based on time-domain reflections and the other based on frequency domain signatures, are introduced. To enable a fully printed encoding circuit, linearly tapering technique is adopted in the first type of tags to cope with parasitic resistances of printed conductors. Both simulation and measurement efforts are made to verify the feasibility of the eight-bit fully printed paper-based tag. In the second type of tags, a group of LC tanks are exploited for encoding data in frequency domain with their resonances. The field measurements of the proof-of-concept of the tag produced by toner-transferring process and flexible printed circuit boards are provided to validate the practicability of the reconfigurable ten-bit chipless RFID tag. Furthermore, a novel RFID tag antenna design adopting linearly tapering technique is introduced. It shows 40 % save of conductive ink materials while keeping the same performance for conventional half-wave dipole antennas and meander line antennas. Finally, the paper discusses the future trends of chipless RFID tags in terms of fabrication cost, coding capacity, size, and reconfigurability. We see that, coupled with revolutionary design of low-cost tag antennas, fabrication/reconfiguration by printing techniques, moving to higher frequencies to shrink tag sizes and reduce manufacturing cost, as well as innovation in ID generating circuits to increase coding capacities, will be important research topics towards item-level tracking applications of chipless RFID tags.     

Flexible RFID Tag Metal Antenna on Paper‐Based Substrate by Inkjet Printing Technology

A reliable and low‐cost solution‐processing procedure to synthesize a highly adhesive flexible metal antenna with low resistivity for radio‐frequency identification device (RFID) tags on paper substrates via inkjet printing combined with surface modification and electroless deposition (ELD) is demonstrated in this paper. Through the surface modification of colloidal solution of hydrolyzed stannous chloride and chitosan solution, the paper‐based substrate is able to reduce the penetration rate of ink and further increase the adsorption amount of silver ions, which could create a catalytic activating layer to catalyze the subsequent ELD of a conductive deposited metal antenna. The resulting metal antenna for RFID tags presents good adhesive strength and low resistivity of 2.58 × 10^?8 Ω·m after 40 min of ELD, and maintains a reliable reading range of RFID tags even after over 1000 times of bending and mechanical stress. Consequently, the developed technology proposed allows for cheap, efficient, and massive production of metal antenna for paper‐based RFID tags with excellent mechanical and electrical properties. Furthermore, this process is especially advantageous for the fabrication of next‐generation flexible electronic devices based on paper substrates.     

Problem of dynamic change of tags location in anticollision RFID systems

Presently the necessity of building anticollision RFID systems with dynamic location change of tags appear more often. Such solutions are used in identification of moving cars, trains (automatic identification of vehicles – AVI processes) as well as moving parts and elements in industry, commerce, science and medicine (internet of things). In the paper there were presented operation stages in the RFID anticollision system necessary to communicate with groups of tags entering and leaving read/write device interrogation zone and communication phases in conditions of dynamic location change of tags. The mentioned aspects influence RFID system reliability, which is characterized by the efficiency coefficient and the identification probability of objects in specific interrogation zone. The communication conditions of correct operation of multiple RFID system are crucial for efficient exchange of data with all tags during their dynamic location changes. Presented problem will be the base to specify new application tag parameters (such as maximum speed of tag motion) and synthesis of interrogation zone required for concrete anticollision RFID applications with dynamic location change of tags.     

基于动态位隙分组盲分离的UHF RFID防碰撞算法

提出一种基于独立成分分析(ICA)和位隙动态分组技术的超高频(UHF)射频识别(RFID)多标签防碰撞算法。利用ICA算法实现多目标的同时识别,利用动态位隙标签分组保证阅读器同时读取的标签数少于或等于其天线数,从而使ICA工作于非欠定状态。理论分析和实验结果表明,该算法的标签识别率远高于传统随机或确定性TDMA RFID防碰撞算法的标签识别率。     

模切法RFID天线制造技术

现有被动式RFID标签天线制造技术存在着不足：主流的蚀刻法工艺繁琐,产出速度慢,对环境有污染;印刷法使用的导电银油墨的成本居高不下,而且天线可靠性也存在问题;电镀法在大批量生产时才有成本优势。为此,提出了一种基于模切技术的天线制造方法：针对一款图案精细的超高频RFID天线,用两次模切排废的方法,得到了天线图形。天线与R...     

Reliability of washable wearable screen printed UHF RFID tags

Wearable antennas have an enormous potential in future welfare, healthcare, and childcare applications. These applications require the antenna to be an integral and unnoticeable part of clothing and to be able to endure different environmental conditions and repeated washing. We manufactured UHF RFID tags by screen printing polymer thick film ink antennas on two different fabric substrates and tested the effects of different types of washing cycles on two key properties of wearable passive UHF RFID tags: threshold power and theoretical read range. Despite the detrimental impact of the washing cycles and detergents, the RFID tags remained wirelessly readable at the distances of beyond 1.3 m, which is satisfactory for many field applications.     

Performance of Printed Polymer-Based RFID Antenna on Curvilinear Surface

The performance of flexible printed RFID tags affixed onto cylindrical containers is dependent on the inductive behavior of the bent antenna on the tag. Conductive polymeric coil antennas were screen printed onto flexible substrates, and the coil resistances, the inductances, and the S-parameters of the antenna coils were measured and analyzed. The RFID dies were mounted onto the antenna coils and the read ranges were characterized as a function of curvature. The results show that the coil inductance decreased slowly with increasing curvature, and the maximum read range of the tags was markedly reduced with the curvature. The decrease in the coil inductance and the maximum read range were hypothesized to vary with the projected bent coil area instead of the geometric coil area. Experimental results confirmed that the maximum read range of an RFID tag affixed on a curvilinear surface can be predicted by the classical inductive coupling model with the bent projected coil area. On the basis of the experimental and analytical results, a reading reliability factor of two is proposed as a design parameter for flexible RFID tags.     

RFID标签芯片的最新研究进展

射频识别(RFID)系统是一种具有广泛应用前景的自动识别系统。近年来,射频识别技术以快速增长趋势在供应链、门禁、公交系统、行李跟踪等领域获得了广泛的应用。文章详细论述了不同频段RFID标签芯片的最新研究进展,对标签芯片的核心模块射频模拟前端、数字控制器、存储器的研究及发展趋势进行了分析。最后,讨论了标签芯片的发展方向。     

SARIF: A novel framework for integrating wireless sensor and RFID networks

Radio frequency identification (RFID) is a promising technology for ubiquitous computing. When we embed RFID tags into environment-sensitive objects, RFID networks must be integrated with wireless sensor networks (WSNs). In this article, we first identify key requirements for designing an efficient and flexible integration framework. Based on the requirements, we propose a sensor and an RFID integration framework (SARIF). As middleware that operates on top of RFID networks and WSNs, SARIF enables the design of diverse applications flexibly and manages network resources efficiently. We also demonstrate the effectiveness of SARIF by implementing a prototype.     

Printed organic transistors for ultra-low-cost RFID applications

Printed electronics provides a potential pathway toward the realization of ultra-low-cost radio frequency identification (RFID) tags for item-level tracking of consumer goods. Here, we report on our progress in developing materials and processes for the realization of printed transistors for low-cost RFID applications. Using inkjet printing of novel conductors, dielectrics, and organic semiconductors, we have realized printed transistors with mobilities >10/sup -1/cm/sup 2//V-s. AC performance of these devices is adequate for 135-kHz RFID, and, with further optimization, 13.56-MHz RFID appears to be within reach. We review the performance of these devices, and discuss optimization strategies for achieving the ultimate performance goals requisite for realizing ultra-low-cost printed RFID.     

RFID System On-line Testing Based on the Evaluation of the Tags Read-Error-Rate

RFID systems are complex heterogeneous systems, consisting of analog and digital hardware components and software components. RFID technologies are often used into critical domains or within harsh environments. But as RFID systems are only based on low cost and low-performance equipments, they do not always ensure robust communications. All these points make the on-line testing of RFID systems a very complex task. This article proposes a new on-line testing approach allowing the detection of tags defects to enhance system reliability and availability. This approach is based on the characterization of a statistical system parameter, the tag Read-Error-Rate, to perform the on-line detection of faulty RFID components. As an introduction to RFID tags on-line testing, a Failure Modes and Effects Analysis first describes the effects of the potential defects on these systems. Second, a SystemC model of the RFID system is proposed as a way to evaluate the proposed test solutions. Then, our solution to enhance system reliability is presented. Finally, validation of our on-line test approach using system-level simulation is discussed.     

Novel in-line method for patterned deposition of conductive structures

We report on a novel method for patterned deposition of conductive polymers, which is derived from and fully compatible with fast in-line printing methods. The method is aimed at improving resolution, homogeneity and edge sharpness of printed conductive structures for applications in the field of printed electronics. The surface energy of a foil substrate, which has been increased by means of corona treatment, was reduced in selected areas through contact with materials that have suitable surface properties and can be patterned at micrometer scale (i.e. printing plates). A conductive fluid was sprayed onto the chemically heterogeneous surface. The fluid accumulated at areas with higher surface energy. After the drying process, the conductive polymer structures were used as source/drain contacts for the preparation of OFETs.     

一种新型的基于无源射频身份识别应答器的电源供给方案

提出了一种基于全集成的无源射频身份识别(RFID)应答器芯片的电源供给方案,并在特许半导体的0.35μm嵌入EEPROM的CMOS工艺线上流片成功.提出的AC/DC和DC/DC电荷泵能够为RFID的应答器芯片提供稳定的工作电压,同时具有极低的功耗和很高的充电效率.还给出了电压倍增器的分析模型、与其他电荷泵的升压原理的比较以及仿真结果和芯片测试结果.     

Concurrent Formation of Metallic Glass During Laser Forward Transfer 3D Printing

In recent years, bulk metallic glasses (BMGs) have drawn much research attention and are shown to be of industrial interest due to their superior mechanical properties and resistance to corrosion. In spite of the interest in harnessing MG for microelectromechanical systems devices, there are limitations in manufacturing such micrometer‐scale structures. A novel approach for the fabrication of 3D MG structures using laser‐induced forward transfer (LIFT) is demonstrated. Inherent tremendous cooling rates associated with the metal LIFT process (≈10¹⁰ k s^?1) make the formation of a variety of BMGs accessible, including also various binary compositions. In this work, it is demonstrated that LIFT printing of ZrPd‐based metallic glass microstructures can also be performed under ambient conditions. X‐ray diffraction analysis of the printed structures reveals > 95% of amorphous metal phase. Taking advantage of the properties of BMG, high quality printing of high aspect ratio BMG pillars, and microbridges are demonstrated. It is also shown how a composite, amorphous‐crystalline metal structure with a required configuration can be fabricated using multimaterial LIFT printing. The inherent high resolution of the method combined with the noncontact and multimaterial printing capacity makes LIFT a valuable additive manufacturing technique to produce metallic glass‐based devices.     

Using dummy data for RFID tag and reader authentication

Radio-Frequency IDentification (RFID) technology is an essential enabler of a multitude of intelligent applications. The robust authentication of RFID system components is critical in providing trustworthy data delivery from/to tags. In this paper, we propose an authentication protocol based on monitoring the transmissions between readers and tags in the system. The proposed authentication scheme is based on injecting decoys within the exchanged communications (between RFID readers and tags) and is used in the authentication process. Furthermore, the proposed authentication scheme is mathematically modeled and validated using extensive simulation. The simulations results show that the proposed scheme provides a 100% confidence level in the authentication of tags and detection of compromised readers.     

Phase-Encoded Chipless RFID Transponder for Large-Scale Low-Cost Applications

A novel 3 b chipless RFID transponder is presented. The transponder comprises three microstrip patch antennas, which are loaded with open circuited (O/C) high impedance stubs. The antennas are resonant at nearby frequencies, and when excited with their respective resonant frequency signals, they re-radiate backscattered signals with distinct phase characteristics. This phase information is encoded as hexadecimal bits for the proposed chipless RFID tag. Both the CST Microwave Studio full-wave solver and the anechoic chamber measurements show a 30$^{circ}$ phase step for the 3 b chipless RFID transponder. It it easily transferred to printed technology, and it may find applications in the mass identification market.