SMD Capacitors Research Articles

Investigation of Soft-Switching QSW Technique in DC/DC SiC-Based Flying Capacitor Converter With Q2L Control

This paper investigates the soft-switching quasi-square-wave (QSW) technique in DC/DC SiC-based flying capacitor converter with quasi-two-level (Q2L) control establishing design guidelines for constructing high-efficiency soft-switched bidirectional converters with low-voltage power transistors. The general idea behind the soft-switching in the proposed system is based on near-CRM (critical conduction mode) operation using TCM (triangular current mode) and Q2L control with the addition of auxiliary transistor capacitances. The soft-switching process is based on a resonance between the capacitances in parallel to each transistor, and the main inductor - ZVS at turn-on is ensured through proper modulation pattern according to TCM-Q2L control, and the turn-off soft-switching mechanism is assured through the novelty in the form of adding auxiliary capacitance in parallel to each of the SiC power MOSFETs according to QSW operation. Thus, the converter can reach very high efficiency (peak at 99.5%), maintaining soft-switching for a wide operating range, using only small auxiliary SMD capacitors and a low-volume flying capacitor, leading to high power density. The presented study is based on experimental tests using a 1.5 kV model at up to 15 kW and includes the impact of various auxiliary capacitance values and optimal capacitor value selection for maximizing the converter efficiency.

RFID ve GSM 900 MHz Uygulamaları için Elektronik Ayarlanabilir Yeni Bir Anten Tasarımı

In microwave systems, frequency tunable planar antennas have become common place as it is increasingly difficult to cover all the necessary frequency bands required. These antennas are low profile, conformable to planar and nonplanar surfaces, simple and inexpensive to manufacture using modern printed-circuit technology. The work presented in this paper proposes a electronically reconfigurable planar antenna by using only one varactor diode. Varactor diode from Skyworks Solutions Inc. (SVM1251) has been used as tuning element. It provides a tunable capacitance range from 53.65 to 2.79 pF with reverse voltages varying between 0 and 8 V. A 50 Ohm resistor as dummy load, and two 68 pF SMD capacitors are incorporated within the structure in order to protect the DC supply to Network Vector Analyzer from dc current, in addition to having an effect on the size reduction. Proposed antenna operate frequency between 400 MHz and 1116 MHz that include ultra-high frequency (UHF) for radio frequency identification (RFID) and Global Systems for Mobile Communications (GSM) applications. Proposed compact antenna having the overall physical size of 8 mm x 8 mm (0.0203λ x 0.0203 λ) is numerically modeled on FR4 substrate having loss tangent, dielectric constant and height of 0.025, 4.3, and 1.61 mm respectively in the CST Microwave Studio numerical calculation program over the frequency range from 300 MHz to 1.5 GHz. The proposed electrically tunable directional antenna has better return loss level higher than 25 dB with reduced size with novel geometrical structure in the operating frequency between 400 to 1116 MHz.

Analysis of DGS filters using π‐circuit model

AbstractThe design and analysis of two defected ground structures (DGS)‐based filters have been proposed in this article. The first is a multifrequency bandstop filter (BSF) which utilizes a semi‐H defect in the ground plane. This structure is then prototyped on a Rogers 4350B substrate of overall size 45 mm × 15 mm with an external SMD capacitors employed to control the resonance of the circuit for the stopband frequencies of 433, 700, and 915 MHz. An equivalent π‐circuit is modified to validate this multiband filter. The second filter is a combination of a BSF and bandpass filter in one structure. The filter operating with a controllable passband and stopband frequency is fabricated on Rogers 4350B lossy substrate. Two SMD capacitors are loaded in the filter structure to control the passband and stopband frequencies of the filter with a structure size of 20 mm x 20 mm. Finally, the equivalent circuit from the BSF is modified further to encompass the bandpass and bandstop frequency response of the proposed work.

A New Compact Dual-Band Wireless Power Transfer System Using Interlaced Resonators

This letter presents a new compact dual-band wireless power transfer (DB-WPT) system. The proposed system is based on two individual transmitting (TX) and receiving (RX) structures. Each structure consists of two interlaced resonators to achieve compact size. A single microstrip line loaded by a surface mounted capacitor (SMD) is used for power feeding. Moreover, high miniaturization of the TX/RX structures is achieved by SMD capacitor loading. In the proposed DB-WPT system, power is transferred from/to the source/load through electromagnetic resonant coupling between the TX and the RX structures. An equivalent circuit of the proposed DB-WPT system is extracted, and then the optimized structures are fabricated and measured. The measured results are in good agreement with the simulated ones. The proposed DB-WPT system has a peak efficiency of 80% and 73% at a transmission distance of 17 mm for frequency 300 and 675 MHz, respectively.

Design of Quad Band Microstrip Patch Antenna for Electromagnetic Energy Harvesting Applications

In this paper, a modified circular microstrip patch antenna is simulated and fabricated for RF energy harvesting applications. Energy harvesting technologies have risen in term of technical developments gradually recently because of the limitation of energy storage and wired power supply. This paper focuses on quad RF energy harvesting in the operating frequency ranges 2.1 GHz, 2.4 GHz, 2.6 GHz and 5.8 GHz emitting from wi-fi, Wimax, LTE, 3G and 4G. The receiving antenna picking up the radio signal in the aforementioned frequencies then converts it from a radiated electromagnetic wave into an alternating signal and, via rectifier, it is converted later into DC voltage. This voltage can be stored inside battery or the load may be fed directly. In this paper, SMD capacitors resistors and Schottky diode model SMS7630-005LF were chosen in the construction of the rectifier circuit due to their low forward voltage between between 0.15 to 0.45 V, fast switching action and small size.

Transient analysis of latent damage formation in SMD capacitors by Transmission Line Pulsing (TLP)

Latent defects were provoked in SMD capacitors by short TLP current pulses. Simultaneously the transient evolution of the device's charge was extracted to generate its Q(V) characteristics and to determine its capacitive behaviour during the transient current stress. We could alter the capacitors so that normal operation was influenced only slightly, but the dielectric breakdown behaviour was considerably changed, which would result in an endangered application. The proposed method can generate and analyse those latent defects simultaneously.

Lifetime and manufacturability of integrated power electronics

In case of battery electric cars, market data show a traditional exponential gradient of sales figures, known from other technology transitions. The worldwide installed wind and photovoltaic capacity show also an exponential gradient. Even the power density of power electronics is growing exponentially.Power electronics is a prerequisite to enable the exponential growth of power density.Requirements on power electronic packaging technologies are electric performance, thermal performance and robust design. Due to the lack of bond wires, SMD capacitors can be mounted close to semiconductors, resulting in a minimization of parasitic inductance. Thermally, the packaging technology benefits from heat spreading inside the copper leadframe and thin dielectric layers. It obtains a thermal resistance of 0.5K/W, and there is potential to further reduce the thermal resistance by alternative dielectric material. The thermal resistance can be further reduced to at least 0.42K/W by the construction of a double side chip cooling.A robust design can be offered by the combination of a chip copper metallization connecting to copper microvias connecting to the top copper layer, which means no difference in coefficients of thermal expansion. On the bottom side, a silver sinter layer offers a reliable connection between chip and leadframe.This paper describes production process optimizations, thermal optimization possibilities, power cycling lifetime measurements and first conductive anodic filament lifetime measurements at 1000VDC. The outlook onto an integrated 120A 700V SiC MOSFET demonstrator is given.

Lower cutoff frequency improvement of planar EBG‐patterned PDN using edge termination

A designed, fabricated and tested electromagnetic bandgap (EBG) structure is proposed for resolving the problem of the lower cut-off frequency of conventional planar-type EBGs. Bandwidth enhancement is achieved by incorporating edge termination along the edges of the whole EBG-patterned power plane. Measurement results show that the lower cutoff frequency is shifted downwards from 800 to 13 MHz. This structure also improves the upper cutoff frequency of 4.3 GHz for the conventional planar EBG to 5.2 GHz. Using this structure, simultaneous switching noise can be suppressed over the relative bandwidth of 63%, which is higher than the commonly used EBGs. The structure is easily fabricated with the current method of printed circuit board manufacturing processes and commonly used SMD resistors and capacitors.

Assessment of mechanical reliability of surface mounted capacitor by an accelerated shear fatigue test technique

In this study mechanical reliability of Sn3.5Ag0.75Cu solder joints in SMD capacitors has been investigated. Tensile response of the solder joint with respect to thicknesses and aging conditions was studied by using Cu/SnAgCu/Cu model samples. Isothermal lifetime curves of SMD devices subjected to high strain vibrational loading were obtained by using an ultrasonic fatigue testing set-up. Mechanical reliability and the failure modes of solder joints in the SMD capacitors were found to be highly dependent on the microstructure of the solder and the intermetallic compound layer and the testing temperature. Testing at elevated temperature resulted in a clear change of crack path and fracture mode of the solder joints.

An Automated-Switching Precision Decade Capacitor

A new automated-switching precision decade capacitor for applications in industries was designed and tested. By using coaxial microwave switches, the automated-switching precision decade capacitor can be automatically set by electrical TTL signals controlled by a computer. To prevent capacitance from drifting caused by variations of ambient temperature, the internal temperature of the automated-switching precision decade capacitor was effectively kept constant using a temperature-controlled oven with sufficiently thermal isolation. Furthermore, to fulfil the compact-size requirement for using at a high frequency, SMD capacitors with NP0 dielectric were used. The temperature stabilities and linearity of the automated-switching precision decade capacitor are presented in this paper.

Research on SMD Capacitor for RF Protection of SCB Initiators

According to the radio frequency effect mechanism, the performances of SMD capacitor used for RF protection of SCB initiators were studied theoretically and experimentally. The 99.9% firing RF power of SCB initiators without any protection is 14.15W, but none of SCB initiators in parallel with SMD capacitor fired at 20W. The results of capacitor discharge experiment indicate that SMD capacitor has no influences on electrical explosive performances of SCB initiators. Its RF protection capability for SCB initiators of SMD capacitor was tested by RF sensitivity experiment, and the results show that it could significantly reduce the RF sensitivity of SCB initiators when in parallel with appropriate SMD capacitor.

A 265 V<formula formulatype="inline"><tex Notation="TeX">$_{\rm RMS}$</tex></formula> Mains Interface Integrated in 0.35 <formula formulatype="inline"><tex Notation="TeX">$\mu$</tex></formula>m CMOS

A fully integrated 265 VRMS input AC-DC interface is demonstrated in a 0.35-μm CMOS technology, requiring only one optional external low-voltage SMD capacitor for improved performance. The converter can directly interface the universal line voltage (50-60 Hz) and converts this into a regulated DC voltage of 3.3 V. High input voltage operation is made possible through separation of the mains input from the active circuits by custom layout high-voltage capable passive components in between. A compact model of an ideal AC-DC capacitive step-down converter is presented and the proposed circuit architecture is designed to mimic ideal operation and approach the maximum attainable power throughput accordingly. The prototype converter demonstrates a maximum output power of 12.7 μW on a die area of 6 mm2 and enables integrated circuits to be supplied straight from the ubiquitous mains voltage, hereby circumventing the need for traditional converters using expensive and bulky high-voltage discrete components.

Inkjetprinting of Vertically Integrated RC-Circuits

Both capacitors and resistors are widely used passive components. Considering micro hybrid circuits printing of both devices is required. Striving for space-saving layouts, multi-layer capacitors are requested. Additionally, vertical integration of devices is desirable. However, today's screen printing technology cannot be applied to uneven surfaces, limiting the aspect ratio and the ability of vertical integration. Thus, usually SMD capacitors are preferred. In order to increase the degree of vertical integration, resistors are printed on top of printed capacitors, creating RC-circuits. The mask-less inkjet printing allows for realization of such structures. To keep the process simple, no in-between-sintering is applied; the entire component is co-fired in one final step.To model the electric behavior of the RC-circuits, both the capacitors' and resistors' behavior is compared to non-integrated devices of the same size and shape. Based on these results, it is shown how existing single-device models can be applied to integrated devices.To improve the sintering process, furthermore the impact of heat on the behavior of the used organic additives is examined. The solid additives have to burn thoroughly. It is analyzed whether there is a liquid phase during sintering and how this may affect the resulting structure.

230C Hermetically Sealed SMD Tantalum Capacitors

Certain electronic applications, such as oil and gas exploration drilling, are continuously demanding ever higher operating temperatures. Recently operating temperature requirements have increased from 200°C to 230°C with an increased operating life from hours to one thousand hours and beyond. This need is linked with the continuous development of oil drilling heads and sensors and their use for deeper drilling or drilling in more difficult geological conditions. Capacitors with high capacitance value are a common part of the electronic boards used in these applications, but over 125°C/175°C, available capacitor choice is very limited. Tantalum SMD capacitor technology has proved its reliability in operation up to 175°C and there is a limited choice of special designs up to 200°C. Long life wet tantalum capacitors up to 200°C are available from multiple sources, or up to 230°C with reduced operational life from a single source. Hermetically sealed MnO2 tantalum capacitors have demonstrated their ability to offer unique long life stability at 230C combined with solid, stable and robust design. [1]. The next testing and development presented in this paper discusses the basic behavior of the solid hermetically sealed MnO2 tantalum capacitor above 200°C. A certain type of “wear out” has been observed in a longer exposure at 230°C depending on applied voltage. Nevertheless, the basic capability of the capacitor meets the “best in class” requirement for 230°C 1000hours continuous operating life with 50% voltage derating. The paper discusses and summarizes the “wear out” phenomenon observed at temperatures above 200°C on these capacitors and impact of different voltage derating to operational life at 230°C .

Passive and Active Reconfigurable Scan-Beam Hollow Patch Reflectarray Antennas

The design concept of passive and active reconfigurable reflectarray antennas has been proposed and tested. The antenna elements in the array are identical hollowed patches. In the first phase of study the slots are loaded with a SMD capacitor to set the required phase shift needed for array implementation. Simulations show promising results. Mounting a SMD capacitor in such a configuration can be considered as the first step in using capacitive loading on a slotted patch for active microstrip reflectarrays. It is shown that by adjusting the capacitance values it is possible to scan the beam. In the second phase, the patch elements are loaded with active varactor-diode device which its reflected phase can be varied. This phase alteration is based on the variation of the diode capacitance which can be achieved by varying the biasing voltage of the active varactor device. In latter approach by activating these varactor devices, the phase of each antenna element in the array configuration can be adopted dynamically and consequently, its beam direction can be reconfigured. The reflectarrays incorporating passive and active elements have been built and tested at 7.0 GHz and 6.0 GHz, respectively. The performance of the proposed reconfigurable antennas is excellent, and there is good agreement between the theoretical and measurement results which pioneers design of arbitrarily reconfigurable antennas.

High channel-count neural interfaces for multiple degree- of-freedom neuroprosthetics

We have designed, fabricated, and tested an advanced neural interface based on the Utah Electrode Array (UEA) integrated with a custom ASIC that is currently able to acquire 200 channels of neural recordings. The Active Arrays are designed to acquire more neural data with the goal of controlling advanced prosthetic devices with as many as 17 degrees of freedom (DoF). The system is comprised of two modified UEAs, a custom ASIC, SMD capacitors, a Neu- roport™ (Blackrock Microsystems) percutaneous connector, 44 wires, and encapsulation materials. A photograph of the final device is presented in Fig. 1. The device has been tested in-vitro through soak testing in 0.15M PBS with synthetic neural signals applied to measure lifetime and recording fidelity. In-vivo measurements were collected using non-human primate (NHP) models.

Integrated wireless neural interface based on the Utah electrode array

This report presents results from research towards a fully integrated, wireless neural interface consisting of a 100-channel microelectrode array, a custom-designed signal processing and telemetry IC, an inductive power receiving coil, and SMD capacitors. An integration concept for such a device was developed, and the materials and methods used to implement this concept were investigated. We developed a multi-level hybrid assembly process that used the Utah Electrode Array (UEA) as a circuit board. The signal processing IC was flip-chip bonded to the UEA using Au/Sn reflow soldering, and included amplifiers for up to 100 channels, signal processing units, an RF transmitter, and a power receiving and clock recovery module. An under bump metallization (UBM) using potentially biocompatible materials was developed and optimized, which consisted of a sputter deposited Ti/Pt/Au thin film stack with layer thicknesses of 50/150/150 nm, respectively. After flip-chip bonding, an underfiller was applied between the IC and the UEA to improve mechanical stability and prevent fluid ingress in in vivo conditions. A planar power receiving coil fabricated by patterning electroplated gold films on polyimide substrates was connected to the IC by using a custom metallized ceramic spacer and SnCu reflow soldering. The SnCu soldering was also used to assemble SMD capacitors on the UEA. The mechanical properties and stability of the optimized interconnections between the UEA and the IC and SMD components were measured. Measurements included the tape tests to evaluate UBM adhesion, shear testing between the Au/Sn solder bumps and the substrate, and accelerated lifetime testing of the long-term stability for the underfiller material coated with a a-SiC(x):H by PECVD, which was intended as a device encapsulation layer. The materials and processes used to generate the integrated neural interface device were found to yield a robust and reliable integrated package.

Schadenslokalisierung an einem gelöteten SMD-Kondensator / Location of a Defect in a Soldered SMD Capacitor

An electrical failure was detected in an SMD capacitor. Visually, no defect was apparent. By the careful sequential grinding down of a metallographical cross-section through the capacitor, two discoveries were made: A stress crack running obliquely away from the end edge of the capacitor, downwards into the body of the component, and an agglomeration of the Ag/Pd electrode material of the same order of size as that of the distance between the electrodes.