Heater Structure Research Articles

Reliability of platinum electrodes and heating elements on SiO2 insulation layers and membranes

In this work, failure mechanisms of Pt electrodes including adhesion problems, material migration due to thermally induced compressive stress and electromigration that could occur in the platinum electrodes and heater structures at temperatures above 600°C have been systematically studied, after the deposition. Lifetime determination, scanning electron microscopy and XRD analysis have been applied for samples which have experienced different loading conditions in order to qualitatively and quantitatively understand the phenomena. Electromigration testing is performed with the aim to enable time-to-failure prediction for sensor elements and compare different platinum layers in terms of their stability. Dedicated, application-related test structures are used so that the results are applicable to sensor lifetime estimations. Furthermore, a method for the determination of thermal conductivity of thin insulating films has been adapted for the characterization of plasma-enhanced chemical vapor deposition (PECVD) silicon oxide and successfully applied on two materials with different deposition recipes. These two materials are used for the fabrication of platinum-based heating elements with PECVD SiO2 as insulation or membrane layer. The results for the two recipes are similar but with a significant difference. A slight increase of the conductivities has been observed due to a thermal anneal of the test structures at temperatures above 700°C.

Reliability characterization of a soot particle sensor in terms of stress- and electromigration in thin-film platinum

In this work we present a systematic investigation of various failure mechanisms for thin-film platinum heater structures and interdigitated electrodes as components of a resistive type soot particle sensor. We study the role of stress-migration and electromigration and their interaction for the reliability of these sensors. The influence of a titanium adhesion layer and gases from the ambient atmosphere are also studied. Lifetime determination and optical and scanning electron microscopy are applied for samples which have experienced different load conditions to understand qualitatively and quantitatively the phenomena. The aim of this work is to enable time-to-failure prediction and thus provide guidelines for limiting temperature and current density in the actual sensor to ensure its stability over lifetime. We use dedicated, application-related test structures to ensure that the results are applicable to sensor lifetime estimations.

Experimental Investigation on the Performance of a Novel Solar air Heater Based on Flat Micro-heat Pipe Arrays (FMHPA)

Abstract In order to improve the efficiency of solar air heater, a novel solar air heater with flat micro-heat pipe arrays (FMHPA) is presented in this study. The structure of FMHPA-solar air heater, the working principle and experimental test facility have also been described in detail. The efficiency, the pressure drop and the time constant are determined for the FMHPA-solar air heater. The results showed that the average thermal efficiency of the solar air heater is up to 70% of stable operation and time constant is about 14 minutes. Experimental results indicate better thermal efficiency for FMHPA-solar air heater compared to a traditional flat plate heater.

Load characteristics of a suspended carbon nanotube film heater and the fabrication of a fast-response thermochromic display prototype.

The influence of heating load on the thermal response of a CNT film heater has been studied. Two kinds of heat dissipation modes, thermal radiation in a vacuum and convection in the atmosphere, are investigated, respectively. It is found that the thermal response slows down with the load quantities in the both cases. We have further studied the thermal response of a CNT film loaded with thermochromic pigment, which is a kind of phase change material. In addition to the thermal response slowing down with the load quantity, it is also found that the phase change of the thermochromic pigments can also slow down the thermal response. With a suspended CNT film heater structure, we have fabricated a thermochromic display prototype, which can switch from room temperature to 50 °C in about 1 s with a brightness contrast of 4.8 under normal indoor illumination. A 16 × 16 pixel thermochromic display prototype can dynamically display Chinese characters driven by a homemade circuit.

Robust Control for a Spatially Three-Dimensional Heat Transfer Process

Reliable modeling and robust control of heat transfer processes are tasks with many applications in engineering. Such tasks are relevant, for example, in control of high-temperature fuel cells, in manufacturing of semiconductor devices, control and modeling of welding processes, and for a reliable description of tube-like gas heater structures. For this reason, control-oriented modeling procedures for spatially distributed heating systems are described in this paper. The resulting models, derived from a spatial semi-discretization employing a finite volume modeling technique, are parameterized by means of experimental identification procedures. These models are then used for the design of robust controllers as well as for state and disturbance observers. An experimental validation on a test rig available at the Chair of Mechatronics at the University of Rostock concludes this paper.

Discussion on the Structure of Low-Temperature Radiant Heater of Gate Station

As the city develops radiady, the natural gas is widely used nealy in every filed of people’s lives. During the pressure regulation, the phenomenon of ice jam, which can affect the normal utilization, happens. Heater can be regarded as one of the most important measures that prevents pipe from freezing occurring due to temperature drop caused by pressure regulation. Low-temperature radiant heater with tight structure is specifically designed for gad gate station. The heat transfer process of the gate station is analyzed. In the meantime, the mathematical model of radiant heater, which could be fitted for the gate station, is erected. At the same time, the influence of heat exchange size, radiant panel size and radiant efficiency, brought by tube are discussed. The result shows that the tube type of radiant heater has a greatest performance. Considering the tubes with compact structure, taking tube type of radiant heater as the heater used in gate station is the optimal decision. The analysis combined in this paper is the foundation to choose the heater of gate station.

Accurate High Temperature Measurements Using Local Polysilicon Heater Structures

Conventionally, measurements of temperature-dependent device parameters and degradation are performed using thermo chucks or dedicated test-furnaces. With such an equipment, the available temperature range is limited (typically to a maximum of 300 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> C) and reliable temperature switches are rather slow, i.e., in the range of minutes to hours. We refine the recently suggested use of polycrystalline silicon wires, so-called poly-heaters, embedded directly on the chip next to a semiconductor device under test, allowing for fast, accurate, and reliable local temperature control. Based on our previous experience with such structures, we extend the use of the poly-heater to even higher temperatures using a simple methodology. For this, we determine the temperature of the device by the electrical power dissipated in the heater wires, where we take the temperature dependency of the thermal resistances of the materials surrounding the heater and the device into account. With this approach, we obtain convincing agreement for comparisons with experimental data and three-dimensional electrothermal FEM simulations.

Numerical Study on the Flow and Heat Transfer for the inside of the Cylinder Type Natural Gas Heater

The cylinder type natural gas heater is an indispensable piece of equipment in gas production, transmission, and application systems. According to the distinctive structure of the cylinder natural gas heater, the natural convection heat transfer model of both heating surface and cooling surface in the cylinder was built, the temperature and velocity field of the natural convection of the heat-transfer medium--ethylene glycol were numerically simulated. The simulation results show that the symmetrical arrangement of heating and cooling surfaces is not conducive to the formation of an effective heat flow field. Therefore, effective optimizing the layout of the heating and cooling surfaces is obviously a problem that must be solved, to help the heat-transfer medium form a well-organized flow and enhance the heat transfer.

Controlled Crystallization Process of Phase Change Memory Device by a Separate Heater Structure

A Phase change Memory (PCM) device with a separate heater structure was proposed in order to control the crystallization process of the device. Some experimental works have been done to investigate the possibility. A SET pulse with amplitude ranging from 0 V to 3 V and pulse width of 100 ns was applied to the separate-heater layer, TiSi3 for heating up the memory layer, Ge2Sb2Te5. From the experimental result, the resistance of the memory layer dropped gradually by more than two orders of magnitude. This will allow multilevel storage for the memory device.

Design of flowing liquid lithium device for HT-7 tokamak

Lithium is a very attractive element due to its very low radiation power, strong H retention as well as strong O getter activity. Flowing liquid lithium (FLiLi) device, to be used as a plasma-facing limiters, has been designed and will be tested in HT-7 tokamak. It is mainly composed of distributor, guide plate, collector, and heater as well as cooling loop. The heater uses heater strip and cooling loop design, to control the temperature of lithium on the guide plate ranging from 200°C to 400°C. The distributor attached to feeding pipe, distributes liquid lithium (LiLi) flowing on the guide plate. The collector was designed to reclaim the superfluous LiLi and transport it out of device.The paper focuses on the design of flowing liquid lithium device. In addition to the process of design, thermal analysis has been carried out using finite element method (FEM) for optimizing the structure of heater and cooling loop and results of analysis are presented.

Heater optimization for polymer in silica optical switch

An optimization process of specialized heater electrode design for a Multimode Interference (MMI) based polymer in silica thermo-optical switch is described. The switch is designed based on the waveguide structure of photodefinable BenzoCyclobutene (BCB 4024-40) polymer core, sandwiched by a 6μm thickness of silica (SiO2) upper clad layer and BK7 glass as a substrate. The upper clad thickness has been chosen such that to avoid any attenuation due to lossy behavior of the metal electrode. The light path is controlled by embedded thermal heater on top of the waveguide at specified location. Starting from a straight rectangular heater at pre-designed location, a migration technique and optimization toward a trapezoidal heater structure has been proposed which utterly claimed a significant improvement in terms of tuning power by more than 15%.

Novel tube-type LTCC transducers with buried heaters and inner interdigitated electrodes as a platform for gas sensing at various high temperatures

Novel tube-type sensor transducers manufactured in LTCC technology with inner interdigital electrodes and equipped with buried heater structures were developed for high temperature gas sensing up to 700°C. A homogenous temperature distribution of the sensitive layer was achieved by optimization of the structures of the buried heaters by FEM modeling and validated by infrared camera measurements. The thermal time constants of the tubular transducer upon heating and cooling were evaluated. The electrical insulation resistance of the uncoated transducers is in the range of those of 96% pure alumina substrates which are commonly applied for gas sensors. The suitability of the presented tubular sensor transducers was demonstrated exemplarily by depositing a NOx sensitive layer on the screen-printed inner interdigital electrodes. By accumulating NOx molecules as nitrates this sensitive device works like a dosimeter with additionally temporal information about the actual NOx level. The novel rotational symmetry of the transducer geometry with the gas flowing inside of the tube is particularly advantageous for NOx sampling, especially at varying flow rates. The self-heated structure allows a sensitivity variation by adjusting the temperature and a periodic thermal regeneration of the storage sites. From 350 to 450°C, the sensor signal correlates with the total amount of NOx while the NOx concentration is obtained from the signal derivative at a constant flow rate. Thereby, the sensitivity increases with temperature. However at 650°C, the sensitive device works like a common gas sensor allowing a direct concentration detection.

Inkjet Printed Structures for Smart Lab-on-Chip Systems

Lab-on-Chip microfluidic systems require onboard functionalities such as fluid pumping, heating and fluorescent or chemical sensing. An approach is presented to realize these structures by inkjet printing of functional materials or material sandwiches and subsequent curing or sintering. In detail an electro-active polymer membrane pump with passive microstructured valves, an open loop controlled ohmic heater structure for maintaining discrete fluid temperatures and electrodes for free-flow isoelectric focusing along with fluorescent hydrogel pads for pH sensing are discussed that all together are printed onto the cover foil of a polymer based microfluidic chip platform at the size of a microscope slide.

Temperature Uniformity Control in the Low Pressure Process Champer of the IC Equipment

The production of IC equipments requires tight control of temperature uniformity within the substrates during the vacuum deposition process chamber. Though traditional approaches such as PID control methods result in substantial improvements, but they fail in meeting the stringent requirement of less than 1°C variation to guarantee the long-term stability of the temperature. To this end, this paper describes the application of information fusion closed-loop control system.A heater structure was designed and the heating wire was divided into 3 sections. Then a multi-loop temperature coordinated control system model has been developed and the temperature heating process has been divided into five intervals. In order to achieve the desired temperature uniformity of 1°C, information fusion technology was used to predict the parameters of PID controller. Through experiments, the coordinated control system model can attaining the desired uniformity levels.

Design and fabrication of gas tight optical windows in LTCC

Beside the possibilities low temperature co-fired ceramics (LTCC) offer for electric devices they also enable the fabrication of micro fluidic elements like channels and embedded cavities. Hence, LTCC facilitate the realization of complex and integrated micro fluidic systems. Examples can be applied in many areas like micro fuel cells and reaction chambers for synthesis of chemical compounds. However, for many applications it is necessary to have an optically transparent interface to the surroundings. The integration of optical windows in LTCC opens up a wide field of new and innovative applications such as the observation of chemiluminescent reactions. These chemical reactions emit electromagnetic radiation and thus offer a method for noninvasive detection. The optical windows consist of thin glasses (≤ 500 μm) bonded by thermocompression onto a LTCC substrate. As the bonding agent, a low temperature sealing glass paste was used. Borosilicate glasses and fused silica as well as silicon were successfully bonded onto LTCC. In order to bond materials with a large CTE mismatch (i.e. fused silica) to LTCC, it is necessary to limit the heat input to the bond interface. Therefore, a heater structure was integrated into the LTCC substrate beneath the bond interface. This bonding process provides a vacuum proof and gas tight optical port (&amp;lt; 5 × 10−10 mbar·l/sec) with a high bond strength.

A highly sensitive methane sensor with nickel alloy microheater on micromachined Si substrate

A highly sensitive methane sensor on micromachined Si substrate (10Ω-cm, 400μm, p〈100〉) operating at relatively low temperature regime (∼200°C) is reported in this paper. A nickel alloy (DilverP1), having high yield stress ∼680MPa and low thermal conductivity ∼17.5W/m/°C, based microheater with appreciable temperature distribution uniformity and low power consumption (∼140mW at optimum operating temperature) was designed and fabricated for the purpose. Meander shaped heater structure for a device size of 4mm×4mm with a membrane dimension of 2mm×2mm (with an active area of 1.5mm×1.5mm) was investigated as a prototype. The temperature uniformity in the membrane region was further improved with the incorporation of a thin (50μm) Si membrane in place of normally reported SiO2/Si3N4 composite membrane. Thermal stress development during sensor fabrication (owing to high temperature processing steps involved in sensing layer formation) was avoided by incorporation of a low temperature chemical deposition technique of ZnO. MEMS based sensor (nano structured ZnO as sensing layer) with a noble metal catalytic contact Pd–Ag (70%) was tested for five different methane concentrations (e.g. 0.01%, 0.05%, 0.1%, 0.5% and 1.0%) in the temperature range of 125–225°C with N2 as the carrier gas. The response magnitude, response time and recovery time were studied in detail. The MEMS based sensor showed ∼97% response magnitude at an optimum operating temperature of 200°C with ∼47s response time at 1% CH4 in N2. Moreover, the sensor offered appreciable response at even much lower temperature (150°C) also.

Material Engineering for Low Power Consumption and Multi-Level Storage in Lateral Phase-Change Memory

The influence of the phase-change materials on the performance of memory devices for low power consumption and multi-level storage was investigated in this work. Doping N into chalcogenide phase-change materials resulted in higher resistivity and low-response to the temperature. The former characteristic leaded to high heating efficiency for phase change via self-heating and thus reduced the power consumption to about 1/20. The latter characteristic enabled easy control of phase change process in the memory device for multi-level storage. 16 distinct resistance levels were demonstrated in our lateral device by adopting a top heater structure

Tin oxide nanowire sensor with integrated temperature and gate control for multi-gas recognition

The selectivity of a chemiresistive gas sensor comprising an array of single-crystalline tin oxide nanowires (NWs) is shown to be greatly enhanced by combined temperature and gate voltage modulation. This dual modulation was effected by a novel microsensor platform that consisted of a suspended nitride membrane embedded with independently addressable platinum heater and back-gate structures. The sensor was evaluated in a chemical vapor exposure test consisting of three volatile organic compound (VOC) analytes in an air background; VOC concentrations ranged from 20 μmol/mol to 80 μmol/mol. During the exposure test, the temperature and gating conditions of the NW sensor were modulated in order to induce variations in the sensor's analyte response behavior. By treating these temperature- and gate-dependent analyte response variations as an identifying "fingerprint," analyte identification was achieved using a statistical pattern recognition procedure, linear discriminant analysis (LDA). Through optimization of this pattern recognition procedure, a VOC recognition rate of 98% was obtained. An analysis of the recognition results revealed that this high recognition rate could only be achieved through the combined modulation of temperature and gate bias as compared to either parameter alone. Overall, the highly accurate VOC analyte discrimination that was achieved here confirms the selectivity benefits provided by the utilized dual modulation approach and demonstrates the suitability of miniature nanowire sensors in real-world, multi-chemical detection problems.

Application and Research Progress of Heater in Natural Gas Industry

With high-speed development, the natural gas industry will lead and promote the development of related techniques and equipments. This article studies the application of the heater in the gas industry, and indicates that it is an indispensable piece of equipment in natural gas application systems. As a special furnace type, the natural gas heater is the main energy consumer for the process of gas production, transportation, and application. Thus, the development of highly efficient natural gas heaters has become an important research aspect. Investigations and improvements on the structure and heat-transfer process of the heater in order to improve its thermal efficiency are discussed in this article. It is concluded that as a weak point, the heat transfer effect inside the natural gas heater needs to be improved. A simple and effective improved structure of a diversion-type natural gas heater is put forward, so as to help the heat transfer medium form an organized flow and enhance the heat transfer, thus improving the thermal efficiency of the natural gas heater and saving energy considerably. This technology has been awarded a patent in China.

Induction Heating of Aluminum Billets With Linear Motion in a Strong DC Magnetic Field: Magnetothermal Analysis in Two-Dimensional

This paper presents a new structure of an induction heater for aluminum billets. The device consists in using a strong direct-current magnetic field created by a superconducting inductor in which the conducting billet is actuated by a linear motion at a constant velocity. The analysis, which is based on the analytical model for the magnetic field in the billet, has been developed, and then, the eddy currents and the induced heating power have been evaluated. The analytical results are compared with those issued from the finite-element software (COMSOL). The magnetothermal analysis shows that the temperature profile in the billet is homogenous.