Thick Film Resistors Research Articles

Исследование фликкер-шума толстопленочных резисторов

Исследование фликкер-шума толстопленочных резисторов

Noise Properties of Graphene-Polymer Thick-Film Resistors

AbstractGraphene is a very promising material for potential applications in many fields. Since manufacturing technologies of graphene are still at the developing stage, low-frequency noise measurements as a tool for evaluating their quality is proposed. In this work, noise properties of polymer thick-film resistors with graphene nano-platelets as a functional phase are reported. The measurements were carried out in room temperature. 1/f noise caused by resistance fluctuations has been found to be the main component in the specimens. The parameter values describing noise intensity of the polymer thick-film specimens have been calculated and compared with the values obtained for other thick-film resistors and layers used in microelectronics. The studied polymer thick-film specimens exhibit rather poor noise properties, especially for the layers with a low content of the functional phase.

Electrical and Humidity Sensing Properties of WO3 Thick Film Resistor Prepared by Screen Printing Technique

Electrical and Humidity Sensing Properties of WO₃ Thick Film Resistor Prepared by Screen Printing Technique

Effect Of Formation Conditions of Thick Granular Films Based on Dispersed Co3b On Their Phase Composition and Magnetoresistance

An important scientific and technical problem on developing thick resistive granular films used in microelectronics and tool manufacturing is solved. Magnetoresistive Co-containing granular films are obtained by screen printing the pastes consisting of fine-grained cobalt boride Co3B and organic binder on a dielectric substrate. Then, the deposited films are heat treated in air with no protection at all. Differential thermal analysis and thermogravimetric analysis reveal that only ferromagnetic Co (FCC) and amorphous B2O3 are present in the structure of the films at T = 650–850°C. On this basis, the modes for the heat treatment of films are developed. The effect of magnetic field on the electrical resistance of films is studied.

Influence of HVP trimming on primary parameters of thick resistive films

The revival of thick-film technology can be attributed to increasing use of ceramic MEMS devices. Thick-film resistors that are being used both as sensing and as resistive elements are facing reduction in dimensions, higher required tolerances and increasing use of buried components. For these reasons standard trimming procedures are being replaced by an alternative method—trimming by energy of high-voltage pulses (HVP trimming). Aim of this paper is to determine primary geometrical, physical and technological parameters responsible for resistance and noise index changes in thick resistive films caused by this alternative trimming method. Both theoretical and experimental considerations are taken into account using three groups of resistors based on commercially available 1, 10 and 100 kΩ/sq thick-film resistor compositions that were subjected to a series of pulses with increasing amplitudes in such a manner that resistance values gradually changed. Possible causes of observed micro and macro structural changes are determined using presented evaluation method resulting in defining primary parameters responsible for reported behavior.

Assessment of stability and reliability of embedded components in printed circuit boards

PurposeThe purpose of this paper is to investigate the basic functional parameters of passive embedded components in printed circuit boards (PCBs) under environmental exposures such as thermal-humidity and thermal exposure.Design/methodology/approachThe investigations were based on the thin-film resistors made of NiP alloy, thick-film resistors made of carbon or carbon–silver inks, embedded capacitors made of FaradFlex materials and embedded inductor made in various configurations. The capacitors and thin- and thick-film resistors were tested in the climatic chamber in conditions of thermal-humidity exposure at 85°C and 85 per cent RH for 500 h. The embedded inductors were tested in two different environmental conditions: thermal-humidity exposure at 60°C and 95 per cent RH, and thermal exposure at 150°C and additionally at the temperature in the range of +25°C to +150°C.FindingsStudies show that in the case of embedded capacitors, the changes caused by exposure to thermal-humidity are durable and lead to the capacity increase. The embedded thin-film resistors behave in the same manner, whereas the thick-film resistors were the least resistant to the conditions of exposure. Most of the polymer thick-film resistors have been damaged. The changes of coils' properties during aging are small, and what is most important is that, after some time of exposure, their parameters stabilize at a particular level. The changes resulting from the increase in temperature are typically related to the change of material resistance (Cu) of which coils are made, and as such, they cannot be avoided but they can be predicted.Research limitations/implicationsThe realized studies allowed determination of the properties of the embedded passive elements with respect to specific environmental exposures. The studies show that embedded resistors can be used interchangeably with chip passive elements. It allows saving the area on the surface of PCB, occupied by these passive elements, for assembly of active elements integrated circuits (ICs) and thus enabling the miniaturization of electronic devices.Originality/valueThe knowledge about the behavior of the operating parameters of embedded components, considering the environmental conditions, allows for development of more complex systems with integrated PCBs.

Stability of electrical properties for mechanically exposed thick- and thin-film resistors on flexible substrates

PurposeThe paper aims to verify the influence of mechanical factors (longitudinal elongation at constant stretching velocity, constant elongation strain and cyclic compressive and tensile stresses) on the electrical properties of thin-film and polymer thick-film resistors on flexible substrates.Design/methodology/approachKapton foil was used as a substrate for all test samples. Designed resistive structures were made with the aid of two polymer thick-film resistive inks or OhmegaPly Ni-P resistive foil. Two different topologies – the horseshoe and triangular – were used. These topologies should have the opposite stability parameters.FindingsAlmost all presented data confirm the influence of the topology of resistors on stability of their electrical properties. The resistive materials applied for test structures also affect the stability under various mechanical exposures.Originality/valueIn general, the largest changes were caused by longitudinal elongation at constant stretching velocity, whereas other tests caused smaller changes of electrical properties. The measurements confirm the influence of topology on stability of electric properties.

Measurement of sub-picoampere direct currents with uncertainties below ten attoamperes.

A new type of the ultrastable low-noise current amplifier (ULCA) is presented. It involves thick-film resistors to achieve a high feedback resistance of 185 GΩ at the input amplifier. An improved noise level of 0.4 fA/Hz with a 1/f corner of about 30 μHz and an effective input bias current well below 100 aA are demonstrated. For small direct currents, measurement uncertainties below 10 aA are achievable even without current reversal or on/off switching. Above about 1 pA, the stability of the ULCA's resistor network limits the relative measurement uncertainty to about 10 parts per million. The new setup is used to characterize and optimize the noise in the wiring installed on a dilution refrigerator for current measurements on single-electron transport pumps. In a test configuration connected to the wiring in a pulse tube refrigerator, a total noise floor of 0.44 fA/Hz was achieved including the contributions of amplifier and cryogenic wiring.

Effect of Morphology on the Electrical Resistivity of Silver Nanostructure Films

The relatively high temperatures (>200 °C) required to sinter silver nanoparticle inks have limited the development of printed electronic devices on low-cost, heat-sensitive paper and plastic substrates. This article explores the change in morphology and resistivity that occurs upon heating thick films of silver nanowires (of two different lengths; Ag NWs), nanoparticles (Ag NPs), and microflakes (Ag MFs) at temperatures between 70 and 400 °C. After heating at 70 °C, films of long Ag NWs exhibited a resistivity of 1.8 × 10-5 Ω cm, 4000 times more conductive than films made from Ag NPs. This result indicates the resistivity of thick films of silver nanostructures is dominated by the contact resistance between particles before sintering. After sintering at 300 °C, the resistivity of short Ag NWs, long Ag NWs, and Ag NPs converge to a value of (2-3) × 10-5 Ω cm, while films of Ag MFs remain ∼10× less conductive (4.06 × 10-4 Ω cm). Thus, films of long Ag NW films heated at 70 °C are more conductive than Ag NP films sintered at 300 °C. Adding 10 wt % nanowires to a film of nanoparticles results in a 400-fold improvement in resistivity.

An optical method for evaluating the degradation mechanism of a developing RuO<sub>2</sub> thick film resistor element for power modules

We devised a simple and noninvasive method for evaluating the spacial distribution of local electron densities of a thick-film RuO2-based chip resistor using UV–VIS-IR reflectance microscopy. After a long-term durability test for 874 h under an elevated temperature of 623 K, RuO2 resistors were thermally damaged, and their resistance became more than 10% higher. We identified the thermally damaged region by this new method and found that the thermal degradation is mainly due to an increase in the resistance between the Ag electrode and the RuO2 resistor film.

Effects of high voltage pulse trimming on structural properties of thick-film resistors

Nowadays, compact and reliable electronic devices including up-to-date ceramic micro-electro-mechanical systems require thick-film resistors with significantly reduced dimensions and stable and precise resistance values. For that reason, instead of standard laser trimming method, high voltage pulse trimming of thick-film resistors is being introduced. This method allows controlled and reliable resistance adjustment regardless of resistor position or dimensions and without the presence of cuts. However, it causes irreversible structural changes in the pseudorandom network formed during sintering causing the changes in conducting mechanisms. In this paper results of the experimental investigation of high voltage pulse trimming of thick-film resistors are presented. Obtained results are analyzed and correlations between resistance and low-frequency noise changes and changes in conducting mechanisms in resistors due to high voltage pulse trimming are observed. Sources of measured fluctuations are identified and it is shown that this type of trimming is a valid alternative trimming method to the dominant laser trimming.

Study of the two dimensional imaging performance for the gas electron multiplier using the resistive anode readout method

The new type of micro-pattern gaseous detector (MPGD) like the gas electron multiplier (GEM), features the advantage of good spatial resolution ( 100 m). However, abundant and high density electronic channels are needed to obtain the high spatial resolution, which will lead to a great pressure on the detector construction, power consumption, spatial utilization, etc. The resistive anode readout method can help to obtain a good spatial resolution comparable to the pixel readout structure with an enormous reduction of the electronic channels. By using the thick film resistor technology, a new type of resistive structure, composed of high resistive square pad array with low resistive narrow border strips, is developed and applied to the readout anode of the triple GEM detector. For the resistive anode readout board used in the experiment, there are 66 resistive cells, which means that the detector needs only 49 electronics channels. To obtain a good spatial resolution, the cell size is set to be 6 mm6 mm. The surface resistivity of the pads and the strips are 150 k/□ and 1 k/□, respectively. The performances of the detector, especially the two-dimensional imaging performance, are studied by using a 55Fe (5.9 keV) source and an X ray tube (8 keV). The test results show that the spatial resolution of the detector is better than 80 m () by using the imaging of a 40 m wide slot, and the nonlinearity is better than 1.5% by the scanning along the x-axis of the readout board in the steps of 1 mm. Furthermore, quite a good two-dimensional imaging capability is achieved by the detector. These good performances of the detector show the feasibility of the resistive anode readout method for the GEM detector with large area and other detectors with similar structures in the two-dimensional imaging applications.

Influence of Sn4+ on Structural and DC Electrical Resistivity of Ni-Zn Ferrite Thick Films

Among the soft ferrites, Ni-Zn ferrite is one of the most versatile ceramic materials because of their important electrical and magnetic properties. These properties were improved by substituting Sn4+ in Ni-Zn ferrites with chemical composition of NixZn1+y−xFe2−2ySnyO4 (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0; y = 0.1, 0.2). To achieve homogenous ferrite powder at lower sintering temperature and smaller duration in nano-size form, the oxalate co-precipitation method was preferred as compared to other physical and chemical methods. Using this powder, ferrite thick films (FTFs) were prepared by the screen printing technique because of its low cost and easy use. To study structural behavior, the FTFs were characterized by different techniques. The x-ray diffraction and thermo-gravimetric and differential thermal analysis studies show the formation of cubic spinel structure and ferrite phase formation, respectively. There is no remarkable trend observed in lattice constants for the Sn4+ (y = 0.1)- and Sn4+ (y = 0.2)-substituted Ni-Zn ferrites. The bond lengths as well as ionic radii on the A-site of Ni-Zn-Sn ferrites were found to decrease with increasing nickel content. The bond length and ionic radii on the B-sites remained almost constant for Sn4+ (y = 0.1, 0.2)-substituted Ni-Zn ferrites. The energy dispersive x-ray analysis confirms the elemental analysis of FTFs. The Fourier transform infrared spectra show two major absorption bands near 400 cm−1 and 600 cm−1 corresponding to octahedral and tetrahedral sites, respectively, which also confirms the formation of the ferrites. The field emission scanning electron microscopy images shows that the particles are highly porous in nature and located in loosely packed agglomerates. The average particle size of the FTFs lies in the range 20–60 nm. Direct current (DC) resistivity of Ni-Zn-Sn FTFs shows the semiconductor nature. The DC resistivity of Ni-Zn-Sn0.2FTFs is lower than Ni-Zn-Sn0.1 FTFs. The DC resistivity is found to decrease with the increase in Ni2+ content up to x = 0.6. It increases thereafter for a further increase in Ni2+ content up to x = 1.0, and a similar trend is observed for the variations of activation energy with Ni2+ content.

Metal particulate-containing conformal coatings for improved IT hardware reliability in harsh environments

A method to overcome IT hardware corrosion-related failures in geographies with highly concentrated atmospheric pollution is presented. Metal particulate was incorporated into a standard silicone conformal coating to form composite materials in which the metal particulate acts as a sacrificial material to react with elemental sulfur. Metal particulates (copper and silver) were chosen based on their strong propensity to corrode in sulfur-rich environments. Through absorption of sulfur into silicone composites, the metal particulate is able to react to form either copper sulfide or silver sulfide before reaching the underlying metallic architectures, thus preventing failures. This approach resulted in up to a ~123% life improvement of the coated component over that of a standard silicone conformal coating. In addition, this approach has shown that the sacrificial material can slow the rate of metal sulfide formation at the metallic interface of thick-film surface mount resistors. The metal particulate-containing conformal coatings developed here overcome many limitations brought about by the use of non-silicone conformal coatings, potentially leading to its incorporation into IT hardware to prevent metallic corrosion of components in harsh environments.

Computational analysis of electrical conduction in hybrid nanomaterials with embedded non-penetrating conductive particles

In this work, a comprehensive multi-resolution two-dimensional (2D) resistor network model is proposed to analyze the electrical conductivity of hybrid nanomaterials made of insulating matrix with conductive particles such as CNT reinforced nanocomposites and thick film resistors. Unlike existing approaches, our model takes into account the impenetrability of the particles and their random placement within the matrix. Moreover, our model presents a detailed description of intra-particle conductivity via finite element analysis, which to the authors’ best knowledge has not been addressed before. The inter-particle conductivity is assumed to be primarily due to electron tunneling. The model is then used to predict the electrical conductivity of electrospun carbon nanofibers as a function of microstructural parameters such as turbostratic domain alignment and aspect ratio. To simulate the microstructure of single CNF, randomly positioned nucleation sites were seeded and grown as turbostratic particles with anisotropic growth rates. Particle growth was in steps and growth of each particle in each direction was stopped upon contact with other particles. The study points to the significant contribution of both intra-particle and inter-particle conductivity to the overall conductivity of hybrid composites. Influence of particle alignment and anisotropic growth rate ratio on electrical conductivity is also discussed. The results show that partial alignment in contrast to complete alignment can result in maximum electrical conductivity of whole CNF. High degrees of alignment can adversely affect conductivity by lowering the probability of the formation of a conductive path. The results demonstrate approaches to enhance electrical conductivity of hybrid materials through controlling their microstructure which is applicable not only to carbon nanofibers, but also many other types of hybrid composites such as thick film resistors.

Highly Sensitive NO2 Detection and DMP Sensing at Room Temperature using Flexible SWNT Thick Film Sensor

<p class="p1"> </p><p class="p2"><span class="s1"> </span>Low cost; easy to fabricate and flexible single wall carbon nanotubes thick film resistor (SWNT-TFR) for detailed study of NO<span class="s2">2 </span>detection is reported. SWNT-TFR was fabricated by vacuum filtration technique on flexible polycarbonate membrane. SWNT-TFR sensor shows selective response to NO<span class="s2">2</span>. The response increases from 1.47 per cent to 17.34 per cent with increasing the NO<span class="s2">2 </span>concentration from 0.2 ppm to 10 ppm, respectively. Different energy sources, IR, thermal and UV were explored for achieving fast recovery of the SWNT-TFR sensor. The results showed that the gas sensor gives immediate and fast recovery in the presence of UVC light. The calculated detection limit is less than 764 ppt for NO<span class="s2">2</span>. We are also presenting sensing of dimethyl methylphosphonate (DMMP) as a simulant of sarin. SWNT-TFR gives repeatable response of ~2.7 per cent for 500 ppm of DMMP. This work suggests the possibility to utilise SWNTs-TFR as NO<span class="s2">2 </span>sensors for air-quality monitoring. </p>

Effect of Firing Temperature on the Glucose Sensing Properties of In<SUB>2</SUB>O<SUB>3</SUB> Based Thick Film Resistors

Effect of Firing Temperature on the Glucose Sensing Properties of In<SUB>2</SUB>O<SUB>3</SUB> Based Thick Film Resistors

High accuracy computational methods for behavioral modeling of thick-film resistors at cryogenic temperatures

Abstract The aim of this work was to elaborate two-dimensional behavioral modeling method of thick-film resistors working in low-temperature conditions. The investigated resistors (made from 5 various resistive inks: 10 resistor coupons, each with 36 resistors with various dimensions), were measured automatically in a cryostat system. The low temperature was achieved in a nitrogen-helium continuous-flow cryostat. For nitrogen used as a freezing liquid the minimal temperature possible to achieve was equal to −195.85 °C (77.3 K). Mathematical model in the form of a multiplication of two polynomials was elaborated based on the above mentioned measurements. The first polynomial approximated temperature behavior of the normalized resistance, while the second one described the dependence of resistance on planar resistors dimensions. Special computational procedures for multidimensional approximation purpose were elaborated. It was shown that proper approximation polynomials and sufficiently exact methods of calculations ensure acceptable modeling errors.

Influence of mechanical exposures on electrical properties of thin and thick-film flexible resistors and conductors

Purpose – The purpose of this paper is to determine the influence of mechanical factors (such as longitudinal elongation or cyclic compressive and tensile stresses) on electrical properties of thin- or thick-film resistors or conductors. Design/methodology/approach – All test samples were made on Kapton foil. Copper foil or silver-based polymer thick-film conductive inks were used for fabrication of conductors. Resistive structures were made with the aid of two polymer thick-film resistive inks or OhmegaPly Ni-P resistive foil. Test structures differ not only in materials applied for resistors or conductors but also in geometrical shape of functional tracks (meanders consisted of many horse-shoes, semicircles, squares or triangles). Findings – Presented results showed significant role of material on range of reversible resistance changes. But shape of test samples also affects relation between relative resistance changes and relative elongation. Originality/value – In general, changes induced by cyclic compressive and stretching stresses were smaller than those caused by substrate elongation.

Noise Measurements Of Resistors With The Use Of Dual-Phase Virtual Lock-In Technique

Abstract Measurement of low-frequency noise properties of modern electronic components is a very demanding challenge due to the low magnitude of a noise signal and the limit of a dissipated power. In such a case, an ac technique with a lock-in amplifier or the use of a low-noise transformer as the first stage in the signal path are common approaches. A software dual-phase virtual lock-in (VLI) technique has been developed and tested in low-frequency noise studies of electronic components. VLI means that phase-sensitive detection is processed by a software layer rather than by an expensive hardware lock-in amplifier. The VLI method has been tested in exploration of noise in polymer thick-film resistors. Analysis of the obtained noise spectra of voltage fluctuations confirmed that the 1/f noise caused by resistance fluctuations is the dominant one. The calculated value of the parameter describing the noise intensity of a resistive material, C = 1·10−21 m3, is consistent with that obtained with the use of a dc method. On the other hand, it has been observed that the spectra of (excitation independent) resistance noise contain a 1/f component whose intensity depends on the excitation frequency. The phenomenon has been explained by means of noise suppression by impedances of the measurement circuit, giving an excellent agreement with the experimental data.