Screen Printing Technology Research Articles

Development of Copper Electro-Plating Technology on a Screen-Printed Conductive Pattern with Copper Paste

An electro-plating technology on a cured isotropic conductive pattern with a hybrid Cu paste composed of resin matrix, copper, and solder powders has been developed. In a conventional technology, Ag paste was used to perform a conductive pattern on a PCB or silicon substrate. From previous research, the electrical conductive mechanism and prin- ciple of the hybrid Cu paste were concisely investigated. The isotropic conductive pattern on the PCB substrate was per- formed using screen-printing technology. The optimum electro-plating condition was experimentally determined by processing parameters such as the metal content of the hybrid Cu paste, applied current density, and time for the electro- plating in the plating bath. The surfaces and cross-sections were observed using optical and SEM photographs. In con- clusion, the optimized processing conditions for Cu electro-plating technology on the conductive pattern were a current density of 40mA/cm 2 and a plating time of 20min on the hybrid Cu paste with a metal content of 44 vol.%. More details of the mechanical properties and processing conditions will be investigated in further research.

Nanostructured Fe2O3/TiO2 thick films: Analysis of structural and electronic properties

Thick films using starting nanopowders of TiO2 (anatase 99.7%) and α-Fe2O3 (hematite) mixed in the weight ratios 60:40 and 40:60 for thick film paste were fabricated by screen printing technology on an alumina substrate. Samples were sintered at temperatures of 800–950°C for 60min. Structural and electronic properties were analyzed by XRD and SEM analysis, UV/vis spectroscopy and current–voltage analysis in view of potential application as gas sensors and anodes in photoelectrochemical cells for hydrogen generation and water splitting. XRD analysis showed that at 800°C monoclinic pseudobrookite formed and anatase had transformed into rutile. Increase in sintering temperature lead to a gradual transformation of monoclinic pseudobrookite into the orthorhombic phase. SEM analysis showed that a homogenous small grain structure was obtained especially in the case of thick film samples with the 40:60 ratio of starting anatase and hematite sintered at 850°C.

All Silk-Screen Printed Polymer-Based Remotely Readable Temperature Sensor

In this paper, we present the fabrication and characterization results of a remotely readable flexible temperature sensor. The sensor has been fabricated with screen printing technology and it consists of a polymer-based capacitor (ASAHI CR18-KTI polymer paste) as a temperature sensitive component added to the antenna coil (ASAHI LS411-AW silver paste) for remote reading purposes. The resonance frequency of the sensor (i.e., the formed LC network) is measured as a function of temperature. The sensor has been characterized in the temperature range of 0 °C-70 °C and the total sensitivity over this range is ~9 kHz/°C. The sensor's normalized temperature response is independent from the polymer capacitor's thickness and the effective capacitor area, which enables reasonable performance despite fabrication process induced inaccuracies. Due to the inexact nature of the resonance peak measurement, a dataanalysis algorithm was developed to enhance the accuracy of the measurement method. In addition, the sensor response to the misaligned reader and the sensor self-heating effect, due to the inductive excitation voltage, are considered. Finally, the calibration of such a sensor is discussed.

One-step firing for electroded PZT thick films applied to MEMS

Free-standing electroded piezoelectric thick-films are straightforwardly fabricated thanks to the association of the low-cost screen-printing technology to the sacrificial layer method. After subsequent printing and drying of a stack of sacrificial, Au, PZT and Au layers on an alumina substrate, the final firing is performed at 900 °C. Then, the partial or total releasing step of the Au/PZT/Au is achieved in a diluted acidic solution. Bridges (3.3 × 3.3 × 0.080 mm3) and cantilevers (8 × 2 × 0.09 mm3) are directly attached to the alumina substrate on top of which they are processed. Studies of the electromechanical behavior of these components show the influence of both the releasing and the densification processes on the piezoelectric properties of the final component. Cantilevers fabricated with this method exhibit favourable properties for sensing applications.

Towards a fully printed electrochemical NO2 sensor on a flexible substrate using ionic liquid based polymer electrolyte

An electrochemical amperometric nitrogen dioxide sensor with solid polymer electrolyte was fabricated by means of screen printing technology on both rigid and flexible substrates. The sensor concept is based on a semi-planar, three-electrode topology that enables low power, high performance, thin, and selective gas sensors to be produced on poly(ethylene terephthalate) (PET) and/or Kapton foil. The sensor response mechanism, i.e. the reduction of nitrogen dioxide at the boundary of a solid polymer electrolyte/working electrode/gas analyte, was predicted by using a Langmuir adsorption isotherm. It was demonstrated that a new platform for the electrochemical NO2 sensor can be completely manufactured by screen printing, which allows the fabrication of a flexible and low cost device suitable for mass production. Further, it was demonstrated that the fully printed sensor can be fabricated without using metal-based printing pastes, which is important from the point of view of the environment. The fully-printed, metal-free electrochemical sensor exhibited a linear response in the range of 0–10ppm, fast response/recovery times (70/60s, respectively), a resolution of 0.2ppm, and a sensitivity of 590nA/ppm, which enables the sensor to be used for both the monitoring of NO2 exposure in the workplace as well as environmental air pollution.

Flexible screen printed thick film thermoelectric generator with reduced material resistivity

This work presents a flexible thick-film Bismuth Tellurium/Antimony Tellurium (BiTe/SbTe) thermoelectric generator (TEG) with reduced material resistivity fabricated by screen printing technology. Cold isostatic pressing (CIP) was introduced to lower the resistivity of the printed thermoelectric materials. The Seebeck coefficient (α) and the resistivity (ρ) of printed materials were measured as a function of applied pressure. A prototype TEG with 8 thermocouples was fabricated on flexible polyimide substrate. The dimension of a single printed element was 20 mm × 2 mm × 78.4 pm. The coiled-up prototype produced a voltage of 36.4 mV and a maximum power of 40.3 nW from a temperature gradient of 20 °C.

Single precursor route to efficient cobalt sulphide counter electrodes for dye sensitized solar cells

ABSTRACT In this work a novel preparation method is proposed for the one step synthesis and thin-film deposition of cost effective counter electrodes for dye sensitized solar cells (DSSC). This method is fast and allows depositing CoS nanoparticles onto F-doped SnO2 (FTO) substrates within 2 hours. The cost of reagents needed is significantly less than the cost of the products based on hexachloroplatinic acid used in the production of platinum transparent counter electrodes, and the method is compatible with the ink-jet and screen-printing technologies. The whole process does not require expensive equipment and is of simple implementation. Electrochemical Impedance Spectroscopy, Cyclic Voltammetry and I-V curves under simulated sunlight were used to characterize the electrode efficiency and stability. The counter electrodes prepared according to our procedure were transparent and show good catalytic activity with the I-/I 3 - redox couple in a high stability electrolyte for DSSC (HSE). Under the best deposition conditions the charge transfer resistance of the electrodes was 1.3 Ωcm 2 , less than that of the screen printed platinum on FTO glass (2.3 Ωcm 2 ). Power conversion efficiencies up to 6.6% were reached using the CoS counter electrodes. The optimized CoS counter electrodes were demonstrated to work also with a ferrocene besed redox liquid electolyte.

Research of Stability and Interference With the Potentiometric Flexible Arrayed Glucose Sensor Based on Microfluidic Framework

The excellent stability and anti-interference of the flexible arrayed glucose sensor based on microfluidic framework were successfully fabricated in this research. First, the ruthenium dioxide sensing membranes were deposited on the polyethylene terephthalate by the radio frequency sputtering technology. Because the ruthenium (Ru) was better catalyst which commonly used in the hydrogenated reaction, the Ru was chosen as the sensing membrane. Second, the conducted wires and the insulation layer were prepared by screen-printed technology. Nafion could increase the stability and prevent the interferences from passing the sensing membrane. Finally, the mixed solution was doped on the sensing membrane by entrapment method that the glucose sensor was successfully fabricated. In order to get the low consumption and decrease required volume of fluid, we combined the flexible arrayed glucose sensor and the microfluidic framework. The sensitivity, stability and anti-interference of glucose sensor based on the microfluidic framework were investigated. According to experimental results, the linearity was 0.994 and the average sensitivity was 0.192 mV/(mg/dL) at the best flow rate of the dynamical condition ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$20~{\mu}$ </tex-math></inline-formula> L/min).

Electrical conductivity of CdS films for gas sensing: Selectivity properties to alcoholic chains

Nanophased cadmium sulfide powder was synthesized with a simple route and characterized with thermal, structural and morphological analysis. Conductometric gas sensors based on thick films of synthesized CdS were fabricated by means of screen-printing technology and their sensing properties were tested on a selection of alcohols, aldehydes, ketones and other gaseous compounds. We found that, at working temperature of 300°C, the CdS films show a strong selectivity vs alcohols, proving that they can efficiently detect alcohols in mixtures where aldehydes and other interferers are present. The response was found to be proportional to the length of the alcoholic chain, and a possible sensing mechanism that accounts for this property was proposed.

Screen Printed Asymmetric Supercapacitors based on LiCoO2 and Graphene Oxide*

AbstractAiming at both high energy and power density, asymmetric supercapacitors with screen printed lithium cobalt oxide (LiCoO2) and graphene oxide GO as electrode materials were assembled. LiCoO2 was synthesized by a facile and inexpensive hydrothermal method, whereas GO was synthesized according to a modified Hummer's method. Both powders were coated on flexible stainless steel substrates using screen printing technology. Finally, asymmetric supercapacitors were assembled using LiCoO2 as positive and GO as negative electrode with a porous polypropylene sheet as separator and an aqueous electrolyte solution of LiClO4. The electrochemical properties of this asymmetric cell were investigated by cyclic voltammetry and galvanostatic charge/discharge experiments. The asymmetric supercapacitor LiCoO2//GO could be cycled reversibly in the wide voltage region 0–1.5 V; it shows an impressive performance with an energy density of 19.2 Whkg–1 (based on the total mass of the active materials of the two electrodes). Importantly, this device exhibits an excellent long cycling life with 85 % specific capacitance retained after 1500 cycles. A demonstration cell could effectively light up an LED.

Research of Novel Phosphor Membrane Packaging Technology for LED Illuminant

A ultra-thin phosphors membrane which realized a good matching of the SMD bracket was prepared by the silk screen printing technology, and the white LED illuminant with the ultra-thin phosphors membrane had a significant advantage over the traditional packing production. The experiment results indicated that the white LED of conventional color rendering index made by membrane packing technology had the same luminous efficiency with the standard sample, while it had an obvious advantage in luminous decay. In 3000 hours, the luminous decay of the white LED illuminant made by membrane packing technology was less than 2%, better than the standard sample with the luminous decay of 3%. The luminous efficiency of the high color rendering index white LED illuminant made by membrane packing technology was higher about 3% than the standard sample; also the luminous decay performance was outstanding.

A disposable cobalt-based phosphate sensor based on screen printing technology

Screen printing is a promising technology because of its simplicity, low-cost, high reproducibility, and efficiency in large-scale production. In this work, a cobalt-based phosphate sensor was successfully fabricated using the screen printing technology for the determination of phosphate concentration in the aqueous solution. The disposable sensor consists of a fully integrated cobalt (Co) electrode, which is a layer of carbon conductive ink (C) physically doped with Co powder, and Ag/AgCl reference electrode. The SEM images show that the morphology of the Co electrode changes after exposure to the phosphate solution, indicating that the expendable reaction exists during the measurement. At the Co/C ratio of 1:99, the cobalt-based phosphate sensor shows phosphate-selective potential response in the range of 10-4 to 10-1 mol/L, yielding a detection limit of 1×10-5 mol/L and a slope of over 30 mV/decade in acidic solution (pH 4.5) for H2PO4-. The proposed screen-printed sensor also exhibited significant reproducibility with a small repeated sensing deviation (i.e., relative standard deviation (R.S.D.) of 0.5%) on a single sensor and a small electrode-to-electrode deviation (i.e., R.S.D. < 3.2%). The recovery study of H2PO4- in real wastewater samples gave values from 95.4% to 101.8%, confirming its application potential in the measurement of phosphate in real samples. Apart from its high selectivity, sensitivity, and stability comparable with a conventional bulk Co-wire electrode, the proposed phosphate sensor still yields many other advantages, such as low price, compactness, ease of use, and the possibility of integration with other analytical devices such as flow injection analysis.

Disposable screen printed electrochemical sensors: tools for environmental monitoring.

Screen printing technology is a widely used technique for the fabrication of electrochemical sensors. This methodology is likely to underpin the progressive drive towards miniaturized, sensitive and portable devices, and has already established its route from “lab-to-market” for a plethora of sensors. The application of these sensors for analysis of environmental samples has been the major focus of research in this field. As a consequence, this work will focus on recent important advances in the design and fabrication of disposable screen printed sensors for the electrochemical detection of environmental contaminants. Special emphasis is given on sensor fabrication methodology, operating details and performance characteristics for environmental applications.

Ni/Cu electroplating, a worthwhile alternative to use instead of Ag screen-printed front side metallization of conventional solar cells

For commercial purposes, it is necessary to manufacture high-efficiency and low-cost solar cells using simple processes. The front contact formation is one of the most critical steps in solar cell processing. Although silver paste screen-printed solar cells are the most widespread on the photovoltaic market, their efficiency is strongly limited as a result of shading and resistive losses, or more precisely the high contact resistance. Cu metallization for crystalline Si solar cells has attracted much attention as an alternative to the screen-printing technology. The low-cost Ni/Cu metal contact is regarded as the next generation of metallization processes to still improve the efficiency with a low specific contact resistance; it is formed using low-cost electroless plating and electroplating. A diffusion barrier should be placed between Cu and Si, to prevent Cu diffusion. Ni is shown to be an adequate barrier to Cu diffusion. For these reasons, geometry optimization of metal contacts of the front face, deposited by commercial processes, is investigated in this paper, in order to improve the spectral response of conventional multicrystalline mc-Si silicon solar cells. Their efficiency variation is analyzed as a function of changes in cell parameters (finger separation distance, height and width of finger, sheet resistance emitter...) using simulation programs in MATLAB, using contours to represent the efficiency evolution in terms of two variables. Efficiency gain of more than 0.7% has been achieved in this study. The simulation results were then compared with experimental data in order to be validated.

Development of a Novel Polishing Pad with a Phyllotactic Pattern, and Experimental Studies

In this paper we discuss the development of a novel polishing pad, and polishing experiments on wafers. The phyllotaxis theory of biology was used to position tin alloy blocks which contained fine diamond abrasive grains on the pad surface. The effects of phyllotactic pattern properties were simulated, and are discussed in detail. Prototype pads were fabricated by use of screen-printing technology. The polishing performance of the pad was tested on wafers. Significant improvements were achieved for polished wafer surface roughness, and its nonconformity was reduced from 3 μm to 1 μm. The suggested range of the diameter of the tin alloy block and the phyllotactic coefficient were from 1.9 mm to 2.1 mm and from 2.0 to 2.2, respectively. These improvements can be attributed to the phyllotactic distribution of the tin alloy blocks, which resulted in favorable contact pressure and temperature distributions, slurry flow, and removal of waste between the polishing pad and the workpiece.

Data Fusion and Fault Diagnosis for Flexible Arrayed pH Sensor Measurement System Based on LabVIEW

This paper concerns the data fusion (DF) and fault diagnosis (FD), which could increase the reliability of measured results when one sensing window was faulty. The flexible arrayed pH sensor was fabricated by radio frequency sputtering system and screen-printed technology, which the ruthenium dioxide was deposited on the polyethylene terephthalate substrate as sensitive membranes and the miniature reference electrodes were fabricated by screen-printed technology. We measured pH buffer solutions for five times and the flexible arrayed pH sensor had a wide sensing range of pH 1-13 solutions. The average sensitivity and linearity were 47.70 mV/pH and 0.839, respectively. We used the Laboratory Virtual Instrumentation Engineering Workbench to do deficient diagnosis which could remove the fault sensing window. The average DF with FD, self-adaptive data fusion with FD and coefficient of variance data fusion with FD could increase sensitivity and linearity ~ 22% and 0.14, respectively.

Passive wireless pressure sensor fabricated in low-temperature co-fired ceramic technology

A passive wireless pressure sensor based on low-temperature co-fired ceramic was investigated. The sensor is equivalent to a LC resonant circuit, which has a planar spiral inductor and an interdigital capacitor electrically connected. The inductor and capacitor are fabricated by screen printing technology. The working principle of the sensor is based on the pressure-sensitive resonant frequency of the LC circuit. Wireless detection can be realized by electromagnetic coupling with two inductor coils. The results show that the resonant frequency of sensor decreases with the increase in pressure, and sensitivity of the sensor is about 412.32 kHz/bar.

High efficiency large area n -type front junction silicon solar cells with boron emitter formed by screen printing technology

In this paper, we report on commercially viable screen printing (SP) technology to form boron emitters. A screen-printed boron emitter and ion-implanted phosphorus back surface field were formed simultaneously by a co-annealing process. Front and back surfaces were passivated by chemically grown oxide capped with plasma-enhanced chemical vapor deposition silicon nitride stack. Front and back contacts were formed by traditional SP and firing processes with silver/aluminum grid on front and local silver back contacts on the rear. This resulted in 19.6% efficient large area (239 cm2) n-type solar cells with an open-circuit voltage Voc of 645 mV, short-circuit current density Jsc of 38.6 mA/cm2, and fill factor of 78.6%. This demonstrates the potential of this novel technology for production of low-cost high-efficiency n-type silicon solar cells. Copyright © 2014 John Wiley & Sons, Ltd.

Study of Free-Standing Electroded PZT Thick-Films: From Materials to Microsystems

Free-standing electroded piezoelectric PZT thick-lms are straightforward fabricatedthanks to the association of the low-cost screen-printing technology with the sacricial layermethod. Au/PZT/Au bridges are directly attached onto the alumina substrate on top of it theyare processed. In addition, completely released disks are also processed. A study of the behaviourof these components shows the inuence of both the releasing process and the densicationon the piezoelectric properties of the PZT layer. From the electromechanical measurements,electroded PZT cantilevers and disks are promising for actuator, sensor or SHM applications.

Printed all-solid flexible microsupercapacitors: towards the general route for high energy storage devices

A novel method for fabricating all-solid flexible microsupercapacitors (MSCs) was proposed and developed by utilizing screen printing technology. A typical printed MSC is composed of a printed Ag electrode, MnO2/onion-like carbon (MnO2/OLC) as active material and a polyvinyl alcohol:H3PO4 (PVA:H3PO4) as solid electrolyte. A capacity of 7.04 mF cm−2 was achieved for the screen printed MnO2/OLC MSCs at a current density of 20 μA cm−2. It also showed an excellent cycling stability, with 80% retention of the specific capacity after 1000 cycles. The printed all-solid flexible MSCs exhibited remarkably high mechanical flexibility when the devices were bent to a radius of 3.5 mm. In addition, all-solid MSCs were successfully demonstrated by screen printing technique on various substrates, such as silicon, glass and conventional printing paper. Moreover, the screen printing technique can be extended to other active materials, such as OLC and carbon nanotubes. This method provides a general route for printable all-solid flexible MSCs, which is compatible with the roll-to-roll process for various high performance active materials.