Electrical characteristics of printed Ag nanopaste on polyimide substrate

We investigated the effects of sintering temperature on the microstructural evolution and electrical characteristics of screen-printed Ag patterns. A conducting paste containing 20 nm Ag nanoparticles (73 wt%) was screen printed onto a polyimide (PI) substrate and sintered at a temperature of 150, 200, 250 and 300 degrees C for 30 min. The microstructures of the sintered patterns were examined using field emission scanning electron microscopy (FESEM). The resistivity under the application of a DC signal decreased with increasing temperature. In the frequency range from 10 MHz to 20 GHz, the S-parameters of the sintered Ag conducting patterns were measured. The S-parameters indicated that the insertion losses at high frequency decreased with increasing sintering temperature due to the formation of interparticle necking after sintering.     

Effect of sintering temperature on electrical characteristics of screen-printed Ag nanopaste on FR4 substrate

We investigated the feasibility of a printing technology for Ag circuit formation on a FR4 substrate. A conductive paste containing Ag nanoparticles (73 wt%) of 20-50 nm diameter was screen printed on an FR4 substrate and sintered under a sintering temperature ranging from 100 degrees C to 200 degrees C for 30 min. We carried out the thermal analysis of the Ag nanopaste to confirm the suitability of the set-up conditions. To investigate the sintering degree with various temperatures, fractured cross-sections were observed by field emission scanning electron microscopy (FESEM). For electrical characterization of the printed Ag circuit, a four-point probe method was used to measure the direct current (DC) resistivity, while a network analyzer and Cascade's probe system in the frequency range from 10 MHz to 20 GHz were used to measure the scattering parameters (S-parameter) of the sintered Ag conducting patterns. The resistivity under the application of a DC signal decreased as the temperature increased. The measured S-parameters indicated that the electrical losses decreased as the sintering temperature increased due to the interparticle neck formation after heat treatment at high temperatures.     

Flexibility of silver conductive circuits screen-printed on a polyimide substrate

The microstructural evolution and mechanical characteristics, especially folding endurance, of screen-printed Ag circuits under various sintering conditions were investigated. The circuits were constructed on a polyimide (PI) film by a screen printing technique using a commercial Ag nanopaste. The sintering temperature and time were raised from 150 to 300 degrees C and from 15 min to 1 hour while the sintering time and temperature were fixed at 30 min and 200 degrees C, respectively. The Massachusetts Institute of Technology (MIT)-type folding endurance tester was used to measure the flexibility of the screen-printed Ag circuits. We observed the change of electrical resistance while the printed Ag patterns were being folded. The folding endurance was better at lower sintering temperature and time, which was explained by the microstructural evolution and macrostructural change of the screen-printed Ag circuits; however, the electrical characteristics were generally poor. Further research is therefore required to improve the electrical and mechanical properties of patterns using direct printing technologies simultaneously.     

Evaluation of the flexibility of silver circuits screen-printed on polyimide with an environmental reliability test

The flexibility of screen-printed silver (Ag) circuits on a polyimide (PI) substrate was investigated under a high temperature and relative humidity (RH). The conductive circuits were constructed on a PI film with a commercial Ag nanopaste via screen printing. The printed patterns were sintered at 200 degrees C for 30 min in a box-type furnace, after which they were placed in a chamber at 85 degrees C/85% RH for various durations: 100, 300, 500, and 1000 h. The Institute for Interconnecting and Packaging Electronic Circuits (IPC) flexural resistance endurance test was conducted to measure the flexibility of the conductive circuits, and the flexibility of the printed patterns was evaluated by detecting the variation of the electrical resistance. The flexibility of the screen-printed conductive circuits decreased as the duration of the 85 degrees C/85% RH test increased. After the 1000 h run of the 85 degrees C/85% RH test, the flexibility of the printed circuits was almost halved compared to that after the 100 h test. To demonstrate the decreased flexibility, the microstructural evolution and partial volume were investigated with a field emission scanning electron microscope (FE-SEM) and a 3D surface profiler, respectively.     

Development of low-power loss Mn-Zn ferrites using microwave sintering method

Microwave sintering (MS) method has been successfully used for densifying Mn- Zn ferrites used for high frequency applications. This method needs only a short time to obtain high density when compared to conventionally sintered (CS) Mn- Zn ferrites. The lowest power loss was also achieved at 100 kHz and 200 mT condition for the microwave sintered samples. Conductor- embedded ferrite transformers were constructed using CS and MS samples and output power, efficiency, and surface rise of temperature were measured at sinusoidal voltage of 25 V with frequency, 1 MHz. The efficiency and surface rise of temperature of transformer were found to be high and low, respectively.     

Low-temperature sintering properties of the screen-printed silver paste for a-Si:H/c-Si heterojunction solar cells

For a-Si:H/c-Si heterojunction (SHJ) solar cells, low-temperature sintered silver paste is necessary to fabricate the metal electrodes on transparent conductive oxide layer. Here, the thermal characteristic, the conductivity, the adhesion strength on indium tin oxide substrate and the microstructure evolution of the screen-printed low-temperature sintered silver grid were investigated by varying the sintering temperature and the sintering time. The results show that the grid performance is closely related to its microstructure. A relatively high sintering temperature and a long sintering time are beneficial to make the organics in the Ag paste burn out and the adjacent Ag particles coalesce together to be larger ones. As a result, the Ag grid can get a dense microstructure and tightly adhere onto the substrate surface. Thus, low line and contact resistance is achieved. What is more, the evolution of the preferential orientation of Ag particles has some contributions to the improved grid conductivity. Specifically, for the SHJ solar cell fabrication, in order to be compatible with the low-temperature deposition of a-Si:H, a long sintering time larger than 60 min with the sintering temperature in the range of 200–230 °C is preferred to realize high performance Ag electrical contacts.     

Preparation of nickel–silver core–shell nanoparticles by liquid-phase reduction for use in conductive paste

Nickel–silver (Ni–Ag) core–shell nanoparticles (NPs) were prepared by depositing Ag on Ni nanocores using the liquid-phase reduction technique in aqueous solution, and their properties were characterised using various experimental techniques. The core–shell NPs had good crystallinity, and the thicknesses of the Ag nanoshells could be tuned effectively. The oxidation resistance of the Ag surface and the electroconductive properties of the Ni core allowed these Ni–Ag core–shell NPs to be used in a conductive paste. Thick films composed of Ni–Ag core–shell NPs were screen-printed on a polycrystalline silicon substrate then sintered at temperatures ranging from 500 °C to 800 °C. Stable resistivity was obtained when the sintering temperature was higher than 650 °C, and the electrical properties of the Ni–Ag core–shell paste were close to those of pure Ag paste. Thus, the Ni–Ag NPs can partly replace pure Ag NPs in conductive pastes.     

Study on the characteristics of building bricks produced from reservoir sediment

This research investigates the feasibility of building bricks produced from reservoir sediment sintering using various sintering temperatures and clay additions. The experimental results indicate that sintered specimen densification occurred at sintering temperatures of 1050-1100 degrees C. Increasing the sintering temperature decreases the water absorption and increases the shrinkage, density and compressive strength of sintered specimens. The experiments were conducted at a temperature ranged from 1050 to 1150 degrees C with clay addition contents varying from 0% to 20%. All sintered specimens made from reservoir sediment were in compliance with Taiwan building bricks criteria. This means that raw materials for producing building bricks can be replaced with reservoir sediment. The metals concentrations of the leachate from the toxicity characteristics leaching procedure (TCLP) test are all complying with the current regulatory limits. These results confirm the feasibility of using reservoir sediment to produce sintered construction brick.     

Microstructural stability of Ag sinter joining in thermal cycling

As a heat-resistant die attach technology processed at low temperatures, three Ag filler-based sinter joining materials have been proposed. Among these, Ag flake pastes exhibited the greatest potential. Joining was carried out by sintering Ag nanoparticles/flakes in air at 200 °C for 60 min. All of the joined samples survived up to 1,000 thermal cycles in a temperature range from ?40 to 180/250 °C with a 30 min dwell time. In particular, the joining strengths with the Ag micron and, Ag nano-thick flake pastes maintained excellent strength. Neither thermal fatigue cracks nor large voids were observed in the Ag sintered layers. Thus, low-temperature and low-pressure sinter joining with Ag flakes is expected to have an application in high power semiconductor devices for ultra-high temperature operation.     

High frequency characteristics of printed Cu conductive circuit

The effects of sintering temperature on microstructural evolution and electrical characteristics of screen printed Cu patterns were observed. A commercial conducting paste containing Cu nanoparticles was screen printed onto a sodalime wafer sintered under a sintering temperature range of 300 degrees C to 450 degrees C. A network analyzer and Cascade's probe system in the frequency range of 10 MHz to 20 GHz were employed to measure the S-parameters of the sintered Cu conducting patterns. From the measured S-parameters, the insertion losses in high frequencies decreased with increasing sintering temperature due to the formation of an interparticle necking after heat treatment at high temperatures. However, oxidation of Cu nanoparticles during the sintering deteriorated the RF performance of the circuits, resulting large deviation of the S-parameters from the simulated curves.     

Adhesion characteristics of silver tracks screen-printed on polyimide with an environmental reliability test

Printable and flexible electronics are increasingly being used in numerous applications that are miniaturized, multi-functional and lightweight. Simultaneously, reliability issues of the printed and flexible electronic devices are getting more attention. The adhesion of screen-printed silver (Ag) tracks on a polyimide (PI) film was investigated after two kinds of the environmental reliability test: a constant-temperature storage test, and a steady-state temperature and humidity storage test. Atmospheric-pressure plasma (APP) was adopted on the PI film surface to improve the poor adhesion derived from the inherent hydrophobicity. The Ag tracks constructed via screen printing were sintered at 250 degrees C for 30 min in air using a box-type muffle furnace. Some samples were exposed under 85 degrees C and 85% relative humidity (RH) for various durations (24, 72, 168 and 500 h), and others were aged at 85 degrees C with same durations to compare the influence of moisture on the adhesion. The adhesion of the screen-printed Ag tracks was evaluated by a roll-type 90 degrees peel test. The peel strength of the screen-printed Ag tracks decreased by 76.74% and 69.88% after 500 h run of the 85 degrees C/85% RH test, and the aging test, respectively. The weakest adhesion was 4.98 gf/mm after the 500 h run of the 85 degrees C/85% RH test. To demonstrate these experimental results, the microstructural evolution and chemical bonding states of the interfacial surfaces were characterized using a field emission scanning electron microscope (FE-SEM), and X-ray photoelectron spectroscope (XPS), respectively.     

Effect of submicron grains on ionic conductivity of nanocrystalline doped ceria

Doped ceria has been considered for high oxygen ion conductivity for solid oxide fuel cells. In the present study, 20 mole% samarium doped nano ceria powder was prepared by wet chemical synthesis and sintered at different temperatures to retain submicron grains (> 92-96% density). ionic conductivity of the sintered pellets was measured using impedance spectroscopy as a function of temperature (200-800 degrees C). The total maximum conductivity was 1.0 x 10(-2)S.cm(-1) (at 600 degrees C) for samples sintered at 1200 degrees C. The activation energy at higher test temperature decreases with the decrease in the sintering temperature (by 25%). The grain boundary, grain interior conductivity and activation energy of the electrolyte were correlated to the resulting microstructure. It has been demonstrated that use of doped nano ceria powder as precursor not only reduced the sintering temperature but also provided segregation free grain boundary for engineering higher conductivity dense electrolytes.     

Effect of fluorine content on mechanical properties of sintered fluoridated hydroxyapatite

The effect of fluorine content, preparing method, and sintering temperature on both the bulk density and biaxial flexural strength of sintered fluoridated hydroxyapatite (FHA) was studied. Both uniaxially pressed un-milled (UPU) and cold isostatically pressed milled (IPM) FHA discs were sintered at temperatures between 1200∼1400 °C at an interval of 100 °C. It was found that the fluorine content had significant impact on the sintering behavior, densification, and mechanical properties of FHA discs. At a low fluorine content, the specimens decomposed between 1200–1400 °C, which resulted in a relatively low sintered density and biaxial flexural strength of the specimens. In comparison, the specimens with high fluorine content did not decompose even at the sintering temperature of 1400 °C. The sintered density and biaxial flexural strength of these specimens increased with the sintering temperature. The maximum sintered density and biaxial flexural strength of the UPU specimens were only 85% of the theoretical density and 45 MPa, respectively. In contrast, much higher sintered density (∼95% of the theoretical density) and mechanical strength (∼100 MPa) were attained for the specimens subjected to the cold isostatic pressing and ball milling. A close correlation between the sintered density and biaxial flexural strength of the specimens was revealed, where the biaxial flexural strength increased exponentially with the sintered density.     

一次烧成制度对SrTiO3基电容—压敏复合功能陶瓷材料的影响

研究了一次烧成制度对ＳｒＴｉＯ３基电容－压敏复合功能陶瓷材料性能的影响。结果表明：适宜的烧成温度有利于促进ＳｒＴｉＯ３的致密化,并获得理想显微结构。中温氧化温度及保温时间对材料的晶界层厚度和晶界势垒高度影响显著。氧化温度低,可使材料具有大的介电常数ε和低压敏电压Ｖ１ｍＡ,但同时介电损耗ｔｇδ上升,非线性系数α减小;保温时间越长,材料中的α值越低,ｔｇδ降低,但ε值减小,Ｖ１ｍＡ增大。通过对比空气中     

Effect of sintering temperature on the characteristics of sludge ceramsite

In order to investigate the effect of sintering temperature on the characteristics of sludge ceramsite and find an optimal sintering temperature, dried sewage sludge, clay, and water glass were mixed at ratios of dried sewage sludge/clay=33% and water glass/clay=15%. Then these mixtures were heated to 850, 900, 950, 1000, 1100, and 1200 degrees C for production of sludge ceramsite. The sludge ceramsite were characterized by DTA-TGA, SEM-EDS, XRD, and XRF. The results indicate that the differences in thermal behaviours are caused by the compositional and structural variations; the ceramsite sintered at 1000 degrees C has more uniformly distributed finer pores (0.5 microm相似文献   

Effect of sintering temperature on the properties of modified mechanical alloyed CaCu3Ti4O12

This paper presents the effects of calcination time and sintering temperature on the properties of CaCu(3)Ti(4)O(12). Electroceramic material of CaCu(3)Ti(4)O(12) was prepared using a modified mechanical alloying technique that covers several processes, which are preparation of raw material, mixing and ball milling for 5 hours, calcination, pellet forming and, sintering. The objective of this modified technique is to enable the calcination and sintering processes to be carried out at a shorter time and lower temperature. The x-ray diffraction (XRD) analysis result shows that a single-phase of CaCu(3)Ti(4)O(12) was completely formed by calcination at 750 degrees C for 12 hours. Meanwhile, the grain size of a sample sintered at 1050 degrees C for 24 hours is extremely large, in the range of 20-50 mum obtained from field emission scanning electron microscopy (FESEM) images. The dielectric constant value of 14,635 was obtained at 10 kHz by impedance (LCR) meter in the sintered sample at 1050 degrees C. However, the dielectric constant value of samples sintered at 900 and 950 degrees C is quite low, in the range of 52-119.     

Effect of spark plasma sintering on microstructure and electrical properties of ZnO-based varistors

Conditions for the elaboration of varistors by spark plasma sintering (SPS) are investigated, using 70 nm zinc oxide nano-particles. For this purpose, the system constituted of zinc oxide, bismuth oxide and other metal oxide is used. Material sintering has been performed by SPS at various temperatures and dwell times. Determination of the microstructure and chemical composition of the as-prepared ceramics are characterized by scanning electron microscopy and X-ray diffraction analysis. Micro-structural analysis revealed the presence of ZnO, spinel and bismuth rich phases. ZnO based Varistor samples sintered within climb speeds 100 and 400 °C/min are compared. The nonlinear electrical characteristics, current–voltage, are measured. The breakdown voltage of the varistors strongly depends on grain sizes. The results show that the best varistors are obtained by SPS at sintering temperatures ranging from 900 to 1200 °C.     

High-pressure Sintering and Microstructure Development of Aluminum Nitride Ceramics with Y2O3 as a Aintering Aid

在5.0 GPa、1300-1800℃条件下不使用烧结助剂高压烧结制备了AlN陶瓷, 研究了烧结温度和烧结时间对AlN高压烧结体微观结构和残余应力的影响. 结果表明: 高压烧结制备AlN陶瓷能有效地降低烧结温度和缩短烧结时间, 在5.0 GPa /1400℃/50 min条件下AlN烧结体表现出穿晶断裂模式; 将烧结温度提高到1800℃在AlN陶瓷中形成了单相多晶等轴晶粒组织; 在5.0 GPa/1700℃/125 min条件下AlN陶瓷内部存在2.0GPa的残余压应力, 其原因是在高压烧结AlN陶瓷出现了晶格畸变     

Optimization of selective emitter fabrication method for solar cells using a laser grooving

In this paper, screen-printing laser grooved buried contact (LGBC) method was applied, which is compatible with the existing screen-printed solar cell equipment and facilities. Experiments were performed in order to optimize short circuit current (I(sc)), open circuit voltage (V(oc)) and fill factor of high efficiency solar cells. To enhance I(sc), V(oc) and efficiency, heavy doping was performed at low sheet resistance in the laser grooved region of the cell. In contrast, light doping was carried out at a high sheet resistance in the non-laser grooved region. To increase fill factor, porous silicon found on the wafer after dipping in an HF solution to remove SiN(x), was cleared. The fabricated screen-printing LGBC solar cell using a 125 mm x 125 mm single crystalline silicon wafer exhibited an efficiency of 17.2%. The results show that screen-printing LGBC method can be applied for high efficiency solar cells.     

V~(5+)-Sr~(2+)共掺杂对TiO_2基压敏陶瓷性能的影响

研究了V~(5+)-Sr~(2+)共掺杂对TiO_2基压敏陶瓷电学性能的影响。采用固相烧结方法制备V~(5+)-Sr~(2+)共掺杂TiO_2样品。利用XRD衍射仪检测物相和SEM测定显微结构。用压敏电阻直流参数仪测定V~(5+)-Sr~(2+)共掺杂TiO_2样品在不同烧结温度和掺杂量下的电学性能。结果表明:掺杂0.35mol%的V_2O_5,XRD衍射仪没有检测到第二相的产生。随着SrCO_3掺杂量以及烧结温度的增加,样品压敏电压和非线性系数都有不同的变化趋势。当烧结温度为1 300℃、Sr~(2+)掺杂量为0.5mol%时,样品的各项电学性能最优:V~(5+)-Sr~(2+)共掺杂TiO_2样品压敏电压达到16.3V/mm,非线性系数α达到5.6。