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NASA NTRS2014

The Significance of Breakdown Voltages for Quality Assurance of Low-Voltage BME Ceramic Capacitors

Application of thin dielectric, base metal electrode (BME) ceramic capacitors for high-reliability applications requires development of testing procedures that can assure high quality and reliability of the parts. In this work, distributions of breakdown voltages (VBR) in variety of low-voltage BME multilayer ceramic capacitors (MLCCs) have been measured and analyzed. It has been shown that analysis of the distributions can indicate the proportion of defective parts in the lot and significance of the defects. Variations of the distributions after solder dip testing allow for an assessment of the robustness of capacitors to soldering-related stresses. The drawbacks of the existing screening and qualification methods to reveal defects in high-value, low-voltage MLCCs and the importance of VBR measurements are discussed. Analysis has shown that due to a larger concentration of oxygen vacancies, defect-related degradation of the insulation resistance (IR) and failures are more likely in BME compared to the precious metal electrode (PME) capacitors.

reliability↗

NASA NTRS2014

Insulation Resistance and Leakage Currents in Low-Voltage Ceramic Capacitors with Cracks

Measurement of insulation resistance (IR) in multilayer ceramic capacitors (MLCCs) is considered a screening technique that ensures the dielectric is defect-free. This work analyzes the effectiveness of this technique for revealing cracks in ceramic capacitors. It is shown that absorption currents prevail over the intrinsic leakage currents during standard IR measurements at room temperature. Absorption currents, and consequently IR, have a weak temperature dependence, increase linearly with voltage (before saturation), and are not sensitive to the presence of mechanical defects. In contrary, intrinsic leakage currents increase super-linearly with voltage and exponentially with temperature (activation energy is in the range from 0.6 eV to 1.1 eV). Leakage currents associated with the presence of cracks have a weaker dependence on temperature and voltage compared to the intrinsic leakage currents. For this reason, intrinsic leakage currents prevail at high temperatures and voltages, thus masking the presence of defects.

dielectric polarization↗

NASA NTRS2016

Insulation Resistance and Leakage Currents in Low-Voltage Ceramic Capacitors with Cracks

testing↗

NASA NTRS2017

A Thermal Runaway Failure Model for Low-Voltage BME Ceramic Capacitors with Defects

Reliability of base metal electrode (BME) multilayer ceramic capacitors (MLCCs) that until recently were used mostly in commercial applications, have been improved substantially by using new materials and processes. Currently, the inception of intrinsic wear-out failures in high quality capacitors became much greater than the mission duration in most high-reliability applications. However, in capacitors with defects degradation processes might accelerate substantially and cause infant mortality failures. In this work, a physical model that relates the presence of defects to reduction of breakdown voltages and decreasing times to failure has been suggested. The effect of the defect size has been analyzed using a thermal runaway model of failures. Adequacy of highly accelerated life testing (HALT) to predict reliability at normal operating conditions and limitations of voltage acceleration are considered. The applicability of the model to BME capacitors with cracks is discussed and validated experimentally.

reliability↗

NASA NTRS2019

Cracking Problems in Low-Voltage Chip Ceramic Capacitors

Cracking remains the major reason of failures in multilayer ceramic capacitors (MLCCs) used in in space electronics. Due to a tight quality control of space-grade components, the probability that as manufactured capacitors have cracks is relatively low, and cracking is often occurs during assembly, handling and the following testing of the systems. Majority of capacitors with cracks are revealed during the integration and testing period, but although extremely rarely, defective parts remain undetected and result in failures during the mission. This situation is aggravated by manual soldering and rework that are often used during low volume production of circuit boards for space. Although failures of MLCCs are often attributed to the post-manufacturing stresses, in many cases they are due to a combination of certain deviations in the manufacturing processes that result in hidden defects in the parts and excessive stresses during assembly and use. This report gives an overview of design, manufacturing and testing processes of MLCCs focusing on elements related to cracking problems. The existing and new screening and qualification procedures and techniques are briefly described and assessed by their effectiveness in revealing cracks. The capability of different test methods to simulate stresses resulting in cracking, mechanisms of failures in capacitors with cracks, and possible methods of selecting the most robust to manual soldering stresses capacitors are discussed.

testing↗

DOE OSTI2023

Investigation into the crystal structure–dielectric property correlation in barium titanate nanocrystals of different sizes

For high capacitance multilayer ceramic capacitors, high dielectric constant and lead-free ceramic nanoparticles are highly desired. However, as the particle size decreases to a few tens of nanometers, their dielectric constant significantly decreases, and the underlying mechanism has yet to be fully elucidated. Herein, we report a systematic investigation into the crystal structure–dielectric property relationship of combustion-made BaTiO 3 (BTO) nanocrystals. When the nanocrystal size was 100 nm and below, a metastable paraelectric cubic phase was found in the as-received BTO (denoted as arBTO) nanocrystals based on an X-ray diffraction (XRD) study. A stable ferroelectric tetragonal phase was present when the nanocrystal size was above 200 nm. Notably, the cubic arBTO (particle size ≤100 nm) exhibited tetragonal fluctuations as revealed by Raman spectroscopy, whereas the tetragonal arBTO (particle size ≥200 nm) contained ~10% cubic fraction according to the Rietveld fitting of the XRD profiles. Thermal annealing of the multi-grain tetragonal arBTO at 950 °C yielded single crystals of annealed BTO (denoted as anBTO), whose dielectric constants were higher than those of arBTO. However, the single crystalline anBTO prevented the formation of 90° domains; therefore, they exhibited a low dielectric constant of ~300. Although X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy could not identify the exact structural defects, our study revealed that surface and bulk defects formed during synthesis affect the final crystal structures and thus the dielectric properties of BTO nanocrystals with different sizes. Finally, the understanding obtained from this study will help us design high dielectric constant perovskite nanocrystals for next-generation multilayer ceramic capacitor applications.

36 MATERIALS SCIENCE↗

NASA NTRS1981

Unstable insulation resistance in ceramic capacitors

The effects of low and varying values of insulation resistance (IR) and their significance in the cause of failure in ceramic capacitors were investigated. Two specific instances involving hardware failure involving ceramic capacitors were examined. It is shown that monolithic, multilayer ceramic capacitors may exhibit low and unstable IR at low voltages, or exhibit no voltage. Other significant results are reported.

Holladay, A. M.↗

NASA NTRS1981

Ultrasonic scanning of multilayer ceramic chip capacitors

Ultrasonic scanning is compared to neutron radiography and scanning laser acoustic microscopy (SLAM). Data show that SLAM and ultrasonic scanning evaluations are in good agreement. There is poor agreement between N-ray and both ultrasonic techniques because N-ray is insensitive to all but the grossest delaminations. Statistical analysis show a good correlation between ultrasonic scanning and destructive physical analysis.

Bradley, F. N.↗

NASA NTRS2014

2014 NEPP Tasks Update for Ceramic and Tantalum Capacitors

Presentation describes recent development in research on MnO2, wet, and polymer tantalum capacitors. Low-voltage failures in multilayer ceramic capacitors and techniques to reveal precious metal electrode (PME) and base metal electrode (BME) capacitors with cracks are discussed. A voltage breakdown technique is suggested to select high quality low-voltage BME ceramic capacitors.

ceramic capacitors↗

NASA NTRS2017

Reliability Issues with PME and BME Ceramic Capacitors

This work is a review of reliability issues specific for low-voltage precious metal electrode (PME) and base metal electrode (BME) multilayer ceramic capacitors (MLCC). A special attention is given to degradation and failures in capacitors with defects, in particular with cracks. Temperature and voltage reliability acceleration factors have been calculated based on approximation of distributions of degradation rates of leakage currents using a general log-linear Weibull model. Results show a substantial difference in behavior of BME and PME capacitors with defects. Mechanisms of degradation and failures in humid and dry environments and risks of overstressing capacitors during highly accelerated life testing (HALT) are discussed.

Teverovsky, Alexander↗

NASA NTRS2015

Evaluation of Case Size 0603 BME Ceramic Capacitors

High volumetric efficiency of commercial base metal electrode (BME) ceramic capacitors allows for a substantial reduction of weight and sizes of the parts compared to currently used military grade precious metal electrode (PME) capacitors. Insertion of BME capacitors in space applications requires a thorough analysis of their performance and reliability. In this work, six types of cases size 0603 BME capacitors from three vendors have been evaluated. Three types of multilayer ceramic capacitors (MLCCs) were designed for automotive industry and three types for general purposes. Leakage currents in the capacitors have been measured in a wide range of voltages and temperatures, and measurements of breakdown voltages (VBR) have been used to assess the proportion and severity of defects in the parts. The effect of soldering-related thermal shock stresses was evaluated by analysis of distributions of VBR for parts in 'as is' condition and after terminal solder dip testing at 350 C. Highly Accelerated Life Testing (HALT) at different temperatures was used to assess the activation energy of degradation of leakage currents and predict behavior of the parts at life test and normal operating conditions. To address issues related to rework and manual soldering, capacitors were soldered onto different substrates at different soldering conditions. The results show that contrary to a common assumption that large-size capacitors are mostly vulnerable to soldering stresses, cracking in small size capacitors does happen unless special measures are taken during assembly processes.

testing↗

DOE OSTI2021

In situ TEM measurement of electrical properties of individual BaTiO 3 nanocubes

We report on the measurement of the electrical properties of individual pristine and doped BaTiO 3 nanocubes by using in situ transmission electron microscopy with a two-electrode configuration. The dimensions of the nanocubes tested are between 10 and 20 nm, which rendered their in situ electrical characterization challenging. We characterized 4%Cr and 5%La (atomic percentage) doped BaTiO 3 nanocubes and compared them with the properties of pristine BaTiO3 nanocubes synthesized by the same solvothermal method. We found that the resistance of all three types of nanocubes when displayed in log-scale shows a nearly linear dependence on the applied electric field (R2 ≥ 0.95) over a wide range of electric fields (50–900 kV/cm). Compared with pristine BaTiO 3 nanocubes, the resistance of both 4%Cr and 5%La doped nanocubes showed reduced variation rates with respect to the electric field, with 5%La doping, demonstrating a better reduction in the variation rate. By developing techniques capable of evaluating the properties of individual BaTiO 3 nanocubes, we expect that our work to open the door to the use of BaTiO 3 nanomaterials in the design of future multilayer ceramic capacitors with improved volumetric efficiency and ferroelectrics-enabled nanodevices with advanced functionality.

36 MATERIALS SCIENCE↗

DOE OSTI2025

Correcting impedance measurements for background parasitics to characterize circuit components in cryogenic environments

Predictable circuit response is a critical prerequisite for accurate electronic measurements. Here, we describe a powerful yet straightforward experimental method and analysis model that utilizes an affordable LCR meter in conjunction with an in situ parasitic-impedance background-correction procedure to measure the temperature-dependent impedance (magnitude and phase) of up to ten individual passive circuit elements in a single cryostat run. We show how the model unambiguously identified a ∼20× drop in capacitance for 22 μF 5XR multilayer ceramic capacitors cooled from 300 K to 360 mK in an environment with a parasitic capacitance of ∼300 pF. The same experimental procedure, based on a simple two-wire measurement, was also used to measure 10 and 22 pF thin-film capacitors and 100 MΩ thick-film resistors. The results showed that the resistor values increased by up to an order of magnitude when the devices were cooled from 300 K to 360 mK. Most importantly, we showed that the simple data-acquisition method, coupled with our analysis model, enabled the measurement of component parasitics, and effectively extended the accuracy of a commercial LCR meter beyond its manufacturer-guaranteed values for a wide range of measurement frequencies. We also showed that, in the current configuration, our simple approach is limited to a capacitance accuracy of ∼10 pF.

Carpenter, R. J. [Santa Clara Univ., Santa Clara, ↗

DOE OSTI2024

Bragg Coherent Imaging of Fluctuating Domains

This review presents two examples of domain dynamics in crystalline solid state samples which were imaged recently with synchrotron X-rays by Bragg Coherent Diffraction methods. Domains are associated with sub-atomic phase shifts in the structure which are revealed by the strong phase contrast associated with Bragg diffraction. At low temperatures, La2-xSrxNiO4 has an antiferromagnetic spin-ordered phase with correlation lengths of 200 nm; its domains are imaged with magnetic Bragg Ptychography to visualize their slow fluctuations. Hydrothermally synthesized nanocrystalline BaTiO3 is found to be made up of ~50 nm domains using Bragg Coherent Diffraction Imaging; electric field induced movement of its internal domain walls is a likely explanation of the nano-material's anomalously large dielectric constant, which is used in the manufacture of multilayer ceramic capacitors

77 NANOSCIENCE AND NANOTECHNOLOGY↗

DOE OSTI2025

Nucleation and growth of polar clusters with in-phase tilts into a long-range ferroelectric matrix in a sodium niobate based complex relaxor

In this study, we have investigated the temperature dependence of atomic ordering at multiple length scales in a lead-free sodium niobate-based relaxor, i.e., 0.75 NaNbO 3 -0.25 Ba 0.9⁢ Ca 0.1⁢ TiO 3 (NN-25BCT) via synchrotron x-ray diffraction, Raman spectroscopy, and pair distribution function analysis. High-resolution synchrotron x-ray powder diffraction (SXRD) measurements reveal a ferroelectric phase transition in the relaxor ferroelectric NN-25BCT below the Vogel-Fulcher freezing temperature (𝑇 VF ≈ 270 K). In addition, SXRD analysis demonstrates the competition between in-phase octahedral tilting and ferroelectric order at the long-range scale using mode crystallography. On the other hand, Raman spectroscopic analysis provides evidence of polar ordering for 𝑇 > 𝑇 VF (with tetragonal symmetry) persisting up to the Burns temperature (𝑇 B ). Furthermore, pair distribution function (PDF) analysis reveals the presence of a polar antiferrodistortive tetragonal phase with 𝑃⁢4⁢𝑏𝑚 space group at short ranges throughout the studied temperatures (i.e., 110 K ≤ 𝑇 ≤500 K), irrespective of nonpolar long-range ordering above 𝑇 VF . Therefore, our measurements provide direct evidence for the presence of polar ordering at short ranges and their gradual transformation into long-range polar ordering using an integrated multiscale structural analysis. In conclusion, as a result of a transition from relaxor to a ferroelectric phase in the vicinity of room temperature, NN-25BCT can be exploited for applications in pyroelectric detectors, electrocaloric devices, and multilayered ceramic capacitors.

36 MATERIALS SCIENCE↗

NASA NTRS1990

High power density dc-to-dc converters for aerospace applications

Three dc-to-dc converter topologies aimed at high-power high-frequency applications are introduced. Major system parasitics, namely, the leakage inductance of the transformer and the device output capacitance are efficiently utilized. Of the three circuits, the single-phase and three-phase versions of the dual active bridge topology demonstrate minimal stresses, better utilization of the transformer, bidirectional, and buck-boost modes of operation. All circuits operate at a constant switching frequency, thus simplifying design of the reactive elements. The power transfer characteristics and soft-switching regions on the Vout-Iout plane are identified. Two coaxial transformers with different cross-sections were built for a rating of 50 kVA. Based on the single-phase dual active bridge topology, a 50 kW, 50 kHz converter operating at an input voltage of 200 Vdc and an output voltage of 1600 Vdc was fabricated. Characteristics of current-fed output make the dual active bridge topologies amenable to paralleling and hence extension to megawatt power levels. Projections to a 1 MW system operating from a 500 Vdc input, at an output voltage of 10 kVdc and a switching frequency of 50 kHz, using MOS-controlled thyristors, coaxially wound transformers operating at three times the present current density with cooling, and multilayer ceramic capacitors, suggests an overall power density of 0.075 to 0.08 kg/kW and an overall efficiency of 96 percent.

Divan, Deepakraj M.↗

NASA NTRS2011

Humidity Steady State Low Voltage Testing of MLCCs (Based on NESC Technical Assessment Report)

Review of the low voltage reduced Insulation Resistance (IR) failure phenomenon in Multilayer ceramic capacitors (MLCCs)and NASA approaches to contend with this risk. 1. Analyze published materials on root cause mechanisms. 2. Investigate suitability of current test methods to assess MLCC lots for susceptibility. 3. Review current NASA parts selection and application guidelines in consideration of benefits vs. disadvantages.

Sampson, Mike↗

NASA NTRS2004

COTS Ceramic Chip Capacitors: An Evaluation of the Parts and Assurance Methodologies

Commercial-Off-The-Shelf (COTS) multilayer ceramic chip capacitors (MLCCs) are continually evolving to reduce physical size and increase volumetric efficiency. Designers of high reliability aerospace and military systems are attracted to these attributes of COTS MLCCs and would like to take advantage of them while maintaining the high standards for long-term reliable operation they are accustomed io when selecting military qualified established reliability (MIL-ER) MLCCs. However, MIL-ER MLCCs are not available in the full range of small chip sizes with high capacitance as found in today's COTS MLCCs. The objectives for this evaluation were to assess the long-term performance of small case size COTS MLCCs and to identify effective, lower-cost product assurance methodologies. Fifteen (15) lots of COTS X7R dielectric MLCCs from four (4) different manufacturers and two (2) MIL-ER BX dielectric MLCCs from two (2) of the same manufacturers were evaluated. Both 0805 and 0402 chip sizes were included. Several voltage ratings were tested ranging from a high of 50 volts to a low of 6.3 volts. The evaluation consisted of a comprehensive screening and qualification test program based upon MIL-PRF-55681 (i.e., voltage conditioning, thermal shock, moisture resistance, 2000-hour life test, etc.). In addition, several lot characterization tests were performed including Destructive Physical Analysis (DPA), Highly Accelerated Life Test (HALT) and Dielectric Voltage Breakdown Strength. The data analysis included a comparison of the 2000-hour life test results (used as a metric for long-term performance) relative to the screening and characterization test results. Results of this analysis indicate that the long-term life performance of COTS MLCCs is variable -- some lots perform well, some lots perform poorly. DPA and HALT were found to be promising lot characterization tests to identify substandard COTS MLCC lots prior to conducting more expensive screening and qualification tests. The results indicate that lot- specific screening and qualification are still recommended for high reliability applications. One significant and concerning observation is that MIL- type voltage conditioning (100 hours at twice rated voltage, 125 C) was not an effective screen in removing infant mortality parts for the particular lots of COTS MLCCs evaluated.

Brusse, Jay A.↗