Optical fibre coating speed prediction from flow properties of coating materials

A prediction method of the maximum coating speed of a coating material has been proposed. The maximum smooth coating speed at which the coating thickness fluctuation begins to increase can be predicted from a critical shear rate value at which the flow curve, measured by a viscometer, deviates from a power law.     

High-speed coating of optical fibres with thermally curable silicone resin using a pressurised die

A high-speed optical fibre coating technique using thermally curable silicone resin was studied. By developing a pressurised die, a smooth coating layer, more than 100 ?m thick, can be successfully achieved at a coating speed of 360 m/min. The coating thickness can also be controlled by adjusting the pressure in the die.     

Interfacial shearing stress in pull-out testing of dual-coatedlightguide specimens

A simple analytical model is developed for the evaluation of the interfacial shearing stress at the glass fiber surface in dual-coated optical fiber specimen subjected to tension. It is shown that the distribution of this stress is nonuniform and that, for the given specimen's length, its maximum value increases with a decrease in the thickness of the primary coating. The obtained results can be useful for comparing the adhesive strength of the primary coating material in fibers of different lengths and with different coating designs, as well as for the in situ evaluation of Young's (shear) modulus of this material from the measured axial displacement of the glass fiber     

High-speed drawing of optical fibers with pressurized coating

To make progress in high-speed drawing of optical fibers, a pressurized coating method was developed on the basis of viscous flow behavior of the coating resin. In a pressurized die, when the shear rate at the fiber surface is minimized, the pressure which is affected by the resin viscosity reaches on optimum condition, resulting in the coating diameter being dependent only on fiber and die diameters. Coating tension is given as a function of pressure so that it is closely related to the optimum pressure through the viscosity. Based on these fundamentals, a 1200-m/min drawing speed was achieved, indicating a smooth and uniform coating with good concentricity. It is clarified that fiber transmission loss does not fundamentally change in relation to the speed.     

Separation of low molecular siloxanes for electronic application byliquid-liquid extraction

Silicone resins are widely used for electronic packaging as potting and encapsulating materials. Silicone resins have many advantages for electronic packaging applications such as superior electrical properties, thermal stability, low water absorption, etc. Furthermore, silicone resins are not only used as protective materials for integrated circuit (IC) devices but also as conducting materials for interconnection. However, silicone resins have two big drawbacks: low adhesion strength and low molecular weight creep. A simple liquid-liquid extraction method has been developed to purify silicone resins, which will improve adhesion strength and eliminate low molecular weight creep. This paper describes the results of the liquid-liquid extraction method to remove low molecular weight cyclic siloxanes. Fourier transform-infrared (FT-lR) spectroscopy was used to monitor the removal rate of low molecular weight cyclic siloxanes. Thermogravimetric analysis (TGA) was used to evaluate the purity of silicone resin. Gas chromatography-mass spectrometry (GC/MS) was used to identify the low molecular weight cyclic siloxanes. Thermomechanical analyzer (TMA), dynamic mechanical analyzer (DMA), and die shear test were used for evaluate the properties of silicone resin     

衍射光学元件制作中的基片涂胶方法

在基片上涂布一层厚度均匀的光刻胶层,是衍射光学元件制作中的一个重要步骤。介绍了目前用于衍射光学元件制作的两种主要涂胶方法———提拉法和旋转法,分析了这两种方法的特点和影响胶层厚度的主要因素,尤其是对其均匀性的影响,并提出了获得均匀胶厚的途径。对于提拉涂胶,选择粘度较高的光刻胶溶液与合适的提拉速度将有助于减小Marangoni流动和Van derWaals力对膜厚均匀性的影响;对于旋转涂胶,可以通过密封基片所在空间,或者通过气流控制器使基片上方空气流动处于层流状态来获得均匀一致的溶剂挥发速率,从而提高胶层的均匀性。     

Aging studies of PBGA solder joints reflowed at different conveyorspeeds

In this paper, the shear cycle fatigue properties of plastic ball grid array (PBGA) assemblies' solder joints reflowed with three different profiles, and aged at 125°C for four, nine, 16, 25, and 36 days are studied. The profiles were devised to have the same "heating factor," which was defined as the integral of the measured temperature above the liquidus (183°C) with respect to dwell time in the reflow profile, but to have different conveyor speeds. The effects of conveyor speed on the solder joint (nonaged and aged) fatigue lifetimes were investigated. It was found hat with increasing the conveyor speed the solder joint shear fatigue lifetime could be improved substantially. Also, the shear fatigue lifetimes of aged solder joints decreased with increasing aging time and variation in fatigue lifetimes increased for faster conveyor speed. SEM and optical micrographs show that faster cooling rate caused a rougher interface of solder/IMC and less crystallization microstructure in solder joints. Rougher interface solder joints have a longer nonaged fatigue life. The thickness of IMC increases with increasing aging time and the growth rate for solder with faster cooling rate was larger. SEM cross section views reveal that cracks initiated at the acute position near the solder pad, then propagated along the interface of the bulk solder/IMC layer. Thicker IMC layers deteriorated fatigue life, so the fatigue lifetime variation of aged solder joints with fast cooling rate was larger     

激光淬火基体对镀铬层界面剪切强度的影响

为了揭示激光淬火预处理基体提高镀铬身管寿命的机理,采用多裂纹拉伸技术分别对激光淬火处理和激光未处理基体上的镀铬层界面剪切强度进行了测量,发现激光淬火基体可以提高镀铬层界面剪切强度77.7%,并从基体与铬层的界面材料结构和力学两个方面进行了分析。结果表明,激光预处理的界面是连续过渡的,而原始基体的界面存在一个过渡;激光淬火基体表面残余压应力的存在提高了铬层的断裂应力;基体表面硬度的提高减小了最大裂纹间距。     

Low-temperature excess loss of UV-curable acrylate/nylon-coated optical fibres

Ultraviolet (UV) radiation curable acrylate/nylon-coated optical fibres show much higher excess loss at low temperatures than silicone/nylon-coated fibres. The difference in low-temperature excess loss between UV-curable acrylate/nylon- and silicone/nylon-coated fibres has been related to the degree of slip between the primary and nylon secondary coating layers during nylon extrusion coating process. The application of a lubricant to the acrylate and nylon interface has been found to be effective in reducing the excess loss at low temperatures.     

Optical loss increase in optical fibre coated with silicone resin containing Si?D

One possible origin of the loss increase phenomenon with heat treatment at 200°C (H2 evolution from the coating material) has been investigated, using optical fibre coated with silicone resin containing the Si?D group. Although OH absorption at 1.4 ?m increases with 200°C heat treatment, no OD peak is observed. It is suggested that silicone resin containing no Si?H and Si?CH2?CH2?Si groups is appropriate as a coating material as no H2 evolution is present.     

Competition between the buckling-driven delamination and wrinkling in compressed thin coatings

The competition between two common failure modes of a thin coating under in-plane compression, the surface wrinkling and the buckling-driven delamination, is studied to assess the critical strain when the mechanical instability may occur at given geometrical and material parameters. A buckling map is constructed based on results of a finite element analysis, which relates the critical applied strain for the onset of instability to the interface adhesion and elastic properties of materials. An approximate scaling relation is derived for the energy release rate of buckling-driven delamination of a coating deposited on a compliant substrate.     

Experimental investigation on liquid-phase fabrication techniques for multilayer infrared hollow fiber

Infrared hollow fiber with metal and dielectric inner-coatings has found applications in medical and industrial fields. It is a commonly used method to lower the loss by inner-coating multi dielectric layers. In this paper, SiO₂ and AgI were selected to fabricate the multilayer mid-infrared hollow fiber. Liquid-phase coating techniques were experimentally discussed in order to control the film thickness. It is shown that concentration and flow speed of the coating solution are key parameters to modify SiO₂ film thickness. AgI film was obtained by firstly coating a silver layer and then iodinating the silver layer into AgI. SiO₂ and AgI films were deposited orderly on the inner wall of a 0.7-mm bore glass capillary. Both thicknesses for SiO₂ and AgI films were well controlled and optimized according to the theoretical calculation. The measured infrared loss spectrum of SiO₂/AgI/SiO₂/Ag multilayer hollow fiber has a good agreement with the calculated result and shows band gap effect around the wavelength of 5.3 μm.     

Dependence of opto-electric properties of (semi-)conducting films in polymer based solar cells on viscous shear during the coating process

Organic photovoltaic is a promising technology for low-cost energy conversion. One of its major challenges is the transfer of the manufacturing process to a continuous roll-to-roll process. Previous research showed that the coating method has a significant impact on film properties, which may be explained by a shear-rate induced crystallization of the polymer–fullerene-blend.In this paper we report on a controlled variation of the shear-rate during slot-die coating of photoactive and conductive layers for polymer solar cells. Light absorption of photoactive layers increased towards higher coating speed and thus higher shear-rate by up to 28% from 0.6 m/min to 12 m/min. The currently lower performance of roll-to-roll processed solar cells, compared to laboratory scale devices may be increased by intentionally applying a high shear rate during the coating process. In contrast, a shear induced crystallization is insignificant for conductive (PEDEOT:PSS and Ag-nanoparticle) films, where conductivity decreased when the operating point approached the stability limit. Thus, a low capillary number is desirable for PEDOT:PSS layers, whereas the performance of the photoactive layer increased within the investigated velocity range. These tendencies, shown here for a standard material system (P3HT:PCBM), are substantial for the design of a roll-to-roll process for efficient polymer solar cells.     

涂胶膜厚优化试验与控制方法

针对本公司目前所用RC-550涂胶机,对影响涂胶膜厚的主要参数（胶轮压力、光刻胶粘度和流量以及胶轮转动速度等）进行试验,得出光刻胶涂布的最优化条件,并对如何获得稳定的涂胶膜厚提出合理化建议.     

Reduction of photoresist usage during spin coating

To reduce the photoresist usage and understand the film spreading process, this study performs flow visualization experiments and numerical simulations. This paper is the first work to show that in the early stage of the spin coating process, the spreading of photoresist is mainly governed by the photoresist injection. Then, instability fingers are formed due to the centrifugal forece. Accompanied by the growing of fingers in length, the Coriolis force broadens the width of the fingers. The numerical results agree with the measured liquid front history at very short times. The difference between the numerical results and experiment data gradually arises due to the formation of instability fingers. The critical injection rate for fully coating a wafer increases with decreasing injection volume. Under a fixed wafer rotating speed, increasing the injection rate can significantly reduce the photoresist usage. To assist in the design and operation of the spin coating process, a regime map for injection rate and injection volume is provided.     

Doping-spike PtSi Schottky infrared detectors with extended cutoffwavelengths

A technique incorporating a p⁺ doping spike at the silicide/Si interface to reduce the effective Schottky barrier of the silicide infrared detectors and thus extend the cutoff wavelength has been developed. In contrast to previous approaches which relied on the tunneling effect, this approach utilizes a thinner doping spike (<2 nm) to take advantage of the strong Schottky image force near the silicide/Si interface and thus avoid the tunneling effect. The critical thickness, i.e., the maximum spike thickness without the tunneling effect has been determined and the extended cutoff wavelengths have been observed for the doping-spike PtSi Schottky infrared detectors. Thermionic-emission-limited and thermally assisted tunneling dark current characteristics were observed for detectors with spikes thinner and thicker than the critical thickness, respectively     

Inhomogeneous Consumption of the Electroless Ni-P Layer at the Solder Joint Formed with Sn-3.5Ag-0.7Cu

This report investigates the phenomenon of interfacial serration at the joint between Sn-3.5Ag-0.7Cu solder (SAC) and electroless Ni-P underbump metallization (UBM) during aging. For comparison, the interface between SAC and electrolytic Ni UBM was also examined under similar aging conditions. The joint in the electrolytic Ni/SAC sample showed a smooth, flat interface between the Ni and intermetallic compounds, even after a long aging time. In contrast, electroless Ni-P/SAC exhibited an irregular interface, the irregularity of which became more severe with increased aging time. This observed roughness was initiated by large breaks across the P-rich layer. The breaks were filled with the overlying Ni-Sn-P phase material, which provided an easier interdiffusion path for Ni and Sn in the opposite direction. As a result, the local consumption of the Ni(-P) layer was accelerated, and the interface was serrated. The local maximum consumption rate of the Ni-P layer, as calculated from the minimum thickness of this layer in each sample with aging time, was similar to that of an electrolytic Ni layer.     

Nepenthes Pitcher Inspired Anti‐Wetting Silicone Nanofilaments Coatings: Preparation,Unique Anti‐Wetting and Self‐Cleaning Behaviors

Nepenthes pitcher inspired anti‐wetting coatings, fluoro‐SNs/Krytox, are successfully fabricated by the combination of fluoro‐silicone nanofilaments (fluoro‐SNs) and Krytox liquids, perfluoropolyethers. Fluoro‐SNs with different microstructure are grown onto glass slides using trichloromethylsilane by simply repeating the coating step, and then modified with 1H,1H,2H,2H‐perfluorodecyltrichlorosilane. Subsequently, the Krytox liquid is spread on the fluoro‐SNs coatings via capillary effect. The fluoro‐SNs/Krytox coatings feature ultra‐low sliding angle for various liquids, excellent stability, and transparency. The sliding speed of liquid drops on the fluoro‐SNs/Krytox coating is obviously slower than on the lotus inspired superhydrophobic and superoleophobic coatings, and is controlled by composition of the coating (e.g., morphology of the fluoro‐SNs, type of Krytox and its thickness) and properties of the liquid drops (e.g., density and surface tension). In addition, the self‐cleaning property of the fluoro‐SNs/Krytox coating is closely related to properties of liquid drops and dirt.     

sol-gel法制备纳米TiO_2-SiO_2宽带高增透膜

通过模拟计算设计出一种透射比为99%、包含一层TiO2薄膜和一层SiO2薄膜的宽带高增透膜。两层薄膜均由溶胶-凝胶法制得并采用提拉法成形于玻璃基片上。对增透膜样品的透射比、表面形貌、膜厚等进行了表征,考察了提拉速度、退火温度、催化条件等对其透射比、表面均匀性的影响。结果表明:增透膜的使用提高了玻璃基片的透射比;当提拉速度为9cm/min,增透膜厚约为255nm时,基片在400～800nm波段的透射比提高了7%。控制退火温度,可以使增透膜在某些波段的透射比增强。增透膜样品的表面均匀性良好,室温下膜层的均方根表面粗糙度(RMS)为1.682,平均粗糙度(RA)为1.208,在550℃的温度以下,随着退火温度升高,表面粗糙度降低。