Exxelia on the moon

Exxelia landed on the far side of the moon with its PM948S film capacitors on board the Chang'e 4 spacecraft


Exxelia landed on the far side of the moon with its PM948S film capacitors on board the Chang'e 4 spacecraft  

Published on 04 Jan 2019 by Rebecca Charles

How to Select the Right Precision Resistor for Your Needs

{ "@context": "https://schema.org/", "@type": "HowTo", "name": "How to Select the Right Precision Resistor for Your Needs", "description": "Learn how to choose the right precision high voltage resistor for your project and find the expert advice you need. Find out how to select the correct precision resistor for best performance.", "image": "https://exxelia.com/uploads/News/how-to-select-the-right-precision-resistor-for-your-needs-65772fa33dd61.png", "totalTime": "PT8M", "estimatedCost": { "@type": "MonetaryAmount", "currency": "USD", "value": "0" }, "step": { "@type": "HowToStep", "text": "" } } I. Introduction to Precision Resistors A. Overview of the Importance of Precision Resistors in Electronic Circuits Precision resistors are integral components in modern electronic circuits, playing a pivotal role in determining the performance and accuracy of these systems. Their primary function is to manage and regulate the flow of electric current, ensuring that other components within the circuit receive the correct amount of power. This precision is particularly crucial in applications requiring high degrees of accuracy and stability, such as in medical equipment, aerospace technology, and sophisticated measuring instruments. The reliability and accuracy of precision resistors directly impact the overall efficiency, reliability, and safety of these electronic systems. B. Explanation of How Precision Resistors Differ from Standard Resistors While standard resistors are used in everyday electronic devices for basic current regulation, precision resistors are engineered to offer much higher accuracy and stability. The key distinctions lie in their tighter tolerance levels, lower temperature coefficients, and superior long-term stability. Tolerance in resistors indicates the degree of variance permissible from their specified resistance value, and precision resistors have significantly lower tolerance levels compared to standard resistors. Additionally, precision resistors exhibit minimal change in resistance with temperature variations, making them ideal for applications where environmental conditions fluctuate. C. Brief Introduction to High Voltage Resistors as a Subset of Precision Resistors High voltage resistors are a specialized category within precision resistors, designed to operate reliably under high voltage conditions. These resistors are crucial in circuits where they must withstand and regulate large voltage levels without compromising performance or safety. They are constructed using materials and designs that can handle high energy loads, and they often feature specific construction techniques to prevent breakdowns or failures due to the high voltage environment. D. Statement Understanding the critical factors in selecting the right precision resistor, especially for high voltage applications, is essential for optimal performance and safety. The selection process involves a comprehensive understanding of various technical parameters, including voltage and power ratings, tolerance, temperature coefficient, and physical packaging. This knowledge ensures that the chosen resistor not only meets the specific needs of the application but also adheres to the highest standards of reliability and safety. Table: Comprehensive Technical Criteria for Selecting High Voltage Precision Resistors Criteria Sub-Criteria Key Considerations Technical Details Application Implications Voltage Rating Maximum Operating Voltage Highest voltage the resistor can handle without breakdown Values typically range from a few kilovolts (kV) to tens of kV; must exceed the maximum circuit voltage Ensures safety and reliability under peak voltage conditions Power Rating Power Dissipation Capacity Amount of power the resistor can dissipate as heat without damage Rated in watts (W); dependent on resistor size, material, and design Prevents overheating and thermal degradation, especially critical in high-load applications Tolerance Accuracy Level Acceptable range of resistance variation from the nominal value Expressed as a percentage (%); tighter tolerance indicates higher precision (e.g., ±0.1%, ±0.5%) Higher precision in control and measurement circuits; critical for calibration and testing equipment Temperature Coefficient Temperature-Dependent Resistance Change Rate at which resistance changes with temperature Expressed as parts per million per degree Celsius (ppm/°C); lower values indicate better stability Minimizes performance variance in fluctuating thermal environments; essential for outdoor and industrial applications Thermal Stability Long-term Resistance Stability at Operating Temperatures Ability to maintain consistent resistance over time at specific temperatures Assessed through accelerated aging tests and thermal cycling Ensures long-term reliability and accuracy in high-temperature applications Physical Size & Form Factor Dimensions and Mounting Style Physical dimensions and installation method of the resistor Includes through-hole, surface-mount, and custom designs; size influences heat dissipation Determines compatibility with circuit board layout and influences thermal management Packaging Material and Construction External materials and construction methods used Options include conformal coating, encapsulation, and use of flame-retardant materials Affects durability, heat dissipation, and environmental resistance (moisture, chemical exposure) Environmental Resistance Resistance to External Conditions Ability to withstand environmental stressors Includes moisture resistance, vibration tolerance, and chemical resistance Ensures stable operation in harsh conditions like high humidity, industrial settings, or mobile equipment The following sections will delve into these aspects in detail, providing a thorough guide for professionals in selecting the most suitable high voltage precision resistors for their specific requirements.     II. Understanding Precision Resistors A. Definition and Characteristics 1. Explanation of What Precision Resistors Are Precision resistors are components in electronic circuits designed to offer high accuracy in their resistance values. Unlike standard resistors, which may have significant variance in resistance, precision resistors are manufactured to have minimal deviation from their specified resistance values. This accuracy is critical in applications where precise control of current and voltage is necessary to ensure the proper functioning of sensitive and high-precision electronic equipment. 2. Key Characteristics: Tolerance, Temperature Coefficient, Noise, and Stability - Tolerance: This refers to the allowable deviation of a resistor's resistance value from its nominal value, expressed as a percentage. For precision resistors, tolerance values are typically much tighter, often below 1%, ensuring greater accuracy. - Temperature Coefficient: This is a measure of how much a resistor's resistance changes with temperature. Precision resistors have low temperature coefficients, meaning their resistance remains stable across a range of temperatures, which is vital for consistent performance. - Noise: In the context of resistors, noise is the random variation in resistance, which can affect the signal quality in sensitive circuits. Precision resistors are designed to minimize noise, ensuring cleaner and more reliable signal transmission. - Stability: This characteristic refers to the ability of a resistor to maintain its resistance value over time, despite environmental factors and usage. Precision resistors have high stability, ensuring long-term reliability. B. Types of Precision Resistors 1. Overview of Various Types - Metal Film: These resistors are known for their high accuracy and low noise. They are made by depositing a thin metal film on a ceramic body. - Wirewound: These are made by winding a metal wire around an insulating core. They are known for high power ratings and stability. - Foil: Foil resistors offer the highest precision and stability. They are made by bonding a metal foil onto a ceramic substrate. 2. Pros and Cons of Each Type in Different Applications - Metal Film: Pros include good temperature coefficient and low noise, making them suitable for precision analog circuits. However, they may not be ideal for high-power applications. - Wirewound: These resistors excel in high-power applications and have good temperature performance. Their downside is their inductance, which may not be suitable for high-frequency applications. - Foil: While offering unparalleled precision and stability, foil resistors can be more expensive and may not be necessary for applications where extreme precision is not required. C. Importance in High Voltage Circuits 1. Role and Significance in High Voltage Applications In high voltage circuits, resistors must handle and regulate large voltages without degradation or failure. Precision resistors in these applications ensure that voltage is managed accurately, which is crucial for the safety and effectiveness of the overall system. Their precision and stability are key in maintaining the integrity of high voltage circuits found in power supplies, medical equipment, and industrial machinery. 2. Challenges Posed by High Voltage Environments High voltage environments pose unique challenges for resistors. They must be designed to withstand high electric fields without breakdown. This includes considerations for dielectric strength, insulation resistance, and physical construction to prevent arcing and physical damage. The materials used must be able to endure these stresses while maintaining their resistive properties over time, ensuring long-term reliability and safety.     III. Criteria for Selecting High Voltage Resistors A. Voltage Rating and Power Rating 1. Understanding Voltage Rating and Its Importance The voltage rating of a resistor indicates the maximum voltage it can handle before it risks breakdown or damage. This is particularly crucial in high voltage applications where resistors are exposed to high potential differences. Selecting a resistor with an appropriate voltage rating is essential to prevent premature failure and ensure safety. The voltage rating must be higher than the maximum voltage expected in the circuit to accommodate transient spikes without compromising the resistor's integrity. 2. How Power Rating Affects Resistor Performance in High Voltage Circuits Power rating is a measure of how much power a resistor can dissipate without exceeding its maximum operating temperature. In high voltage circuits, resistors often encounter high power levels. If a resistor's power rating is too low, it can overheat and fail. It's essential to choose a resistor with a power rating that matches or exceeds the power levels in the circuit. This ensures that the resistor can operate reliably over its intended lifespan without degrading due to thermal stress. B. Tolerance and Accuracy 1. Importance of Tolerance in Precision Resistors Tolerance, the permissible deviation from the nominal resistance value, is critical in precision resistors. In high voltage applications, even small inaccuracies can lead to significant errors or malfunctions. Precision resistors with tight tolerance are essential for applications where precise control of voltage and current is necessary, such as in calibration equipment or high-accuracy measuring devices. 2. Balancing Tolerance and Cost in High Voltage Applications While tighter tolerance is generally desirable, it often comes at a higher cost. Therefore, selecting a resistor involves balancing the need for precision with budget constraints. It's important to evaluate the level of tolerance required for the application’s performance and safety, and choose a resistor that provides the necessary precision without unnecessary expense. C. Temperature Coefficient and Thermal Stability 1. Role of Temperature Coefficient in Resistor Performance The temperature coefficient of a resistor indicates how its resistance changes with temperature. A low temperature coefficient is desirable in high voltage applications, as it ensures that the resistor maintains a stable resistance across a range of operating temperatures. This stability is vital in environments where temperature variations are common, as it affects the accuracy and reliability of the circuit. 2. Managing Thermal Stability in High Voltage Environments In addition to selecting resistors with low temperature coefficients, managing thermal stability involves considering the resistor’s environment. Factors such as ventilation, heat sinks, and placement within the circuit can influence the resistor’s temperature. Proper thermal management ensures that resistors operate within their specified temperature range, maintaining performance and prolonging lifespan. D. Physical Size and Packaging 1. Considering Physical Constraints and Mounting Styles The physical size and form factor of a resistor are important in applications with space constraints or specific mounting requirements. In high voltage circuits, larger resistors might be necessary to ensure adequate spacing for preventing arcing or breakdown. The choice of mounting style (such as through-hole or surface-mount) also impacts the resistor's thermal management and mechanical stability. 2. Impact of Packaging on Heat Dissipation and Durability The packaging of a resistor affects its ability to dissipate heat and withstand environmental stresses. In high voltage applications, resistors must be packaged in a way that promotes efficient heat dissipation to prevent overheating. The materials used in the packaging should also be durable and resistant to environmental factors such as humidity, chemicals, or mechanical stress. This ensures the long-term reliability and performance of the resistor in demanding high voltage environments.     IV. Application-Specific Considerations A. Industry-Specific Requirements 1. Tailoring Resistor Selection to Industry Standards Different industries have unique standards and requirements that significantly influence the selection of precision resistors, especially in high voltage applications. - Aerospace: This industry demands resistors that can withstand extreme conditions such as high altitudes, temperature fluctuations, and vibrations. Resistors must comply with stringent standards for reliability and durability. For example, they often require a very low temperature coefficient and exceptional stability to ensure accurate performance in critical aerospace systems. - Medical: In medical applications, precision resistors are used in sensitive and life-supporting equipment. They must meet high safety standards, ensuring accuracy and reliability. Resistors in these applications often need to be highly precise, with low noise and minimal variability to ensure patient safety and accurate readings. B. Environmental Factors 1. Dealing with Environmental Challenges Environmental conditions such as humidity and temperature extremes play a significant role in the performance of high voltage resistors. - Humidity: High levels of moisture can affect the insulation properties of resistors, potentially leading to short circuits or degradation of components. Selecting resistors with appropriate moisture resistance and protective coatings is crucial in humid environments. - Temperature Extremes: Resistors must be chosen based on their ability to operate reliably under extreme temperatures. This involves selecting materials and designs that can withstand thermal expansion and contraction, as well as maintain their resistive properties across the specified temperature range. C. Customization for Special Requirements 1. When to Consider Custom Solutions for Unique Applications There are scenarios where standard precision resistors might not meet the specific requirements of a high voltage application. In such cases, custom-designed resistors become necessary. - Unique Electrical Requirements: If an application has unusual voltage, current, or power demands that standard resistors cannot meet, custom resistors can be designed to handle these specific requirements. - Physical Space Limitations: In applications where space is constrained, standard resistors might not fit. Custom resistors can be designed with specific sizes and shapes to fit into limited spaces without compromising performance. - Special Environmental Conditions: For applications operating in extreme or unusual environments, such as deep-sea exploration or space missions, custom resistors can be developed with materials and coatings specifically engineered to withstand these conditions.     V. Best Practices in Selecting High Voltage Precision Resistors A. Comprehensive Needs Assessment 1. Identifying Key Parameters Based on Application Needs Before selecting high voltage precision resistors, a thorough assessment of the application’s needs is essential. This involves identifying key parameters that will influence the choice of resistor. Important factors to consider include: - Voltage and Power Requirements: Determine the maximum voltage and power the resistor needs to handle. This ensures the resistor can operate safely under the highest expected loads. - Tolerance and Accuracy Needs: Assess the level of precision required in the application. High-precision applications may necessitate resistors with very tight tolerances. - Environmental Conditions: Consider the operating environment, including temperature ranges, humidity levels, and potential exposure to chemicals or mechanical stress. - Physical Space Constraints: Evaluate the available space for the resistor in the circuit, which will influence the size and form factor of the resistor. - Regulatory and Industry Standards: Identify any industry-specific standards or regulations that the resistors must comply with. B. Vendor Selection and Quality Assurance 1. Choosing Reputable Vendors for High-Quality Components The quality of precision resistors is largely dependent on the manufacturer. Selecting reputable vendors is crucial for ensuring the reliability and performance of the components. Look for vendors with: - Proven Track Record: Choose manufacturers known for their quality and reliability in the industry. - Expertise in High Voltage Applications: Select vendors with specific experience and expertise in manufacturing high voltage precision resistors. - Good Customer Support: A vendor who offers strong technical support can be invaluable, especially for custom applications or when addressing specific technical challenges. 2. Importance of Quality Certifications and Testing Quality certifications and thorough testing are vital for ensuring that the resistors meet the required standards and specifications. - Quality Certifications: Look for resistors that come with relevant quality certifications, such as ISO standards. These certifications indicate that the resistors have been manufactured and tested according to rigorous quality control procedures. - Product Testing: Ensure that the resistors have undergone appropriate testing for parameters such as tolerance, temperature coefficient, and long-term stability. This can include in-house testing by the manufacturer and independent third-party testing. In conclusion, selecting the right high voltage precision resistors involves a detailed needs assessment and careful consideration of various technical parameters. Partnering with reputable vendors and ensuring quality certifications and testing are also critical steps in the selection process. Following these best practices will help in acquiring resistors that meet the specific needs of high voltage applications, ensuring safety, reliability, and optimal performance.

What you should know about Ceramic Capacitors ?

▲ What you should know about Ceramic Capacitors ?   1. Materials expert For 50 years and as a market leader, EXXELIA’s comprehensive knowledge of the materials properties and performances have enabled us to design capacitors in Porcelain, NPO, BX, 2C1, BP, X7R and –2200ppm/°C ceramics. > See our capacitors in catalog   2. Custom Designs Our catalog products don’t meet your application?  Based on the valuable experience accumulated over the design of 2,000+ specific ceramic capacitors, you can trust EXXELIA to define a qualitative custom solution in a time effective manner.   3. No Obsolescence Choosing a standard or custom EXXELIA product means you won’t have to worry about obsolescence.   4. Typical Applications Aerospace & Defense: cockpit panels, flight control, radio systems, missile  guidance systems… Space: military and commercial satellites, launcher… Medical: MRI, external defibrillators, implantable devices… Telecommunications: base stations… Oil and gas: drilling tools, MWD, LWD, wellheads…   5. ISO 9001 And AS9100C Quality is at the core of Exxelia’s corporate culture. Each sites has its own certifications.    6. Certifications Capacitors manufactured by EXXELIA comply with American and European standards and meet the requirements of many international standards. For Space qualified parts (ESA QPL), please refer to our catalog «Ceramic capacitors for Space applications».   7. Quality & Reliability EXXELIA is committed to design and manufacture high quality and reliability products. The test cycles reproducing the most adverse operating conditions over extended periods (up to 10 000 hours) have logged to date well over 5.109 hours/°Component. Failure rate data can be provided upon request. 8. Conflict minerals EXXELIA is committed to an approach based on «Conflict Minerals Compliance». This US SEC rule demands complete traceability and a control mechanism for the mineral procurement chain, encouraging importers to buy only «certified» ore. We have discontinued relations with suppliers that procure from the Democratic Republic of the Congo or an adjoining country.   9. Environment EXXELIA is committed to applying a robust environmental policy, from product design through to shipment. To control its environmental footprint and reconcile this with the company’ functional imperatives, our environmental policy provides for the reduction or elimination of hazardous substances. We also focus on compliance with European Union directives and regulations, notably REACH and RoHS. 10. RoHS Compliancy SMD CAPACITORS The capacitor terminations are generally protected by a nickel barrier formed by electrolytic deposit. This barrier gives chip capacitors leaching performance far exceeding the requirements of all applicable standards. The nickel barrier guarantees a minimum resistance to soldering heat for a period of 1 minute at  260°C in a tin-lead (60/40) or tin-lead-silver (62/36/2) bath without noticeable alteration to the solderability. It also allows repeated soldering-unsoldering and the longer soldering times required by reflow techniques. However nickel barrier amplifies thermal shock and is not recommended for chip sizes equal or greater than CNC Y (30 30) - (C 282 to C 288 - CNC 80 to CNC 94). LEADED COMPONENTS As well as for SMD products, leaded capacitors ranges can also be RoHS. These products, which are characterized by the suffix «W» added to the commercial type, are naturally compatible with the soldering alloys used in RoHS mounting technology. The connections coating is generally an alloy SnAg (with a maximum of 4% Ag). However, on a few products that EXXELIA will precise on request, the coating is pure silver.   11. MLCC Structure   12. Equivalent circuit Capacitor is a complex component combining resistive, inductive and capacitive phenomena. A simplified schematic for the equivalent circuit is:   13. Dielectric characteristics  Insulation Resistance (IR) is the resistance measured under DC voltage across the terminals of the capacitor and consists principally of the parallel resistance shown in the equivalent circuit. As capacitance values and hence the area of dielectric increases, the IR decreases and hence the product (C x IR) is often specified in Ω.F or MΩ.µF. The Equivalent Series Resistance (ESR) is the sum of the resistive terms which generate heating when capacitor is used under AC voltage at a given frequency (f). Dissipation factor (DF) is the ration of the apparent power input will turn to heat in the capacitor: DF = 2π f C ESR When a capacitor works under AC voltage, heat power loss (P), expressed in Watt, is equal to: P = 2π f C Vrms2 DF   The series inductance (Ls) is due to the currents running through the electrodes. It can distort the operation of the capacitor at high frequency where the impedance (Z) is given as: Z = Rs + j (Ls.q - 1⁄(C.q)) with q = 2πf When frequency rises, the capacitive component of capacitors is gradually canceled up to the resonance frequency, where : Z = Rs and LsC.q2 = 1 Above this frequency the capacitor behaves like an inductor.   Manufacturing steps > See our capacitors in catalog SMD environmental tests Ceramic chip capacitors for SMD are designed to meet test requirements of CECC 32100 and NF C 93133 standards as specified below in compliance with NF C 20700 and IEC 68 standards: Solderability: NF C 20758, 260°C, bath 62/36/2. Adherence: 5N force. Vibration fatigue test: NF C 20706, 20 g, 10 Hz to 2,000 Hz, 12 cycles of 20 minutes each. Rapid temperature change: NF C 20714, –55°C to + 125°C, 5 cycles. Combined climatic test: IEC 68-2-38. Damp heat: NF C 20703, 93 %, H.R., 40°C. Endurance test: 1,000 hours, 1.5 URC, 125°C. > See our capacitors in catalog   STORAGE OF CHIP CAPACITORS TINNED OR NON TINNED CHIP CAPACITORS Storage must be in a dry environment at a temperature of 20°C with a relative humidity below 50 %, or preferably in a packaging enclosing a desiccant.  STORAGE IN INDUSTRIAL ENVIRONMENT: 2 years for tin dipped chip capacitors, 18 months for tin electroplated chip capacitors, 2 years for non tinned chip capacitors, 3 years for gold plated chip capacitors. STORAGE IN CONTROLLED NEUTRAL NITROGEN ENVIRONMENT: 4 years for tin dipped or electroplated chip capacitors, 4 years for non tinned chip capacitors, 5 years for gold plated chip capacitors. Storage duration should be considered from delivery date and not from batch manufacture date. The tests carried out at final acceptance stage (solderability, susceptibility to solder heat) enable to assess the compatibility to surface mounting of the chips.   LEAD STYLES   SOLDERING ADVICES FOR REFLOW SOLDERING   Large chips above size 2225 are not recommended to be mounted on epoxy board due to thermal expansion coefficient mismatch between ceramic capacitor and epoxy. Where larger sizes are required, it is recommended to use components with ribbon or other adapted leads so as to absorb thermo-mechanical strains. RECOMMENDED FOOTPRINT FOR SMD CAPACITORS  Ceramic is by nature a material which is sensitive both thermally and mechanically. Stresses caused by the physical and thermal properties of the capacitors, substrates and solders are attenuated by the leads. Wave soldering is unsuitable for sizes larger than 2220 and for the higher ends of capacitance ranges due to possible thermal shock (capacitance values given upon request). Infrared and vapor phase reflow, are preferred for high reliability applications as inherent thermo-mechanical strains are lower than those inherent to wave soldering.    SOLDERING ADVICES FOR IRON SOLDERING Attachment with a soldering iron is discouraged due to ceramic brittleness and the process control limitations. In the event that a soldering iron must be used, the following precautions should be observed: Use a substrate with chip footprints big enough to allow putting side by side one end of the capacitor and the iron tip without any contact between this tip and the component, place the capacitor on this footprint, heat the substrate until the capacitor’s temperature reaches 150°C minimum (preheating step, maximum 1°C per second), place the hot iron tip (a flat tip is preferred) on the footprint without, touching the capacitor. Use a regulated iron with a 30 watts maximum, power. The recommended temperature of the iron is 270 ±10°C. The temperature gap between the capacitor and the iron tip must not exceed 120°C, leave the tip on the footprint for a few seconds in order to increase locally the footprint’s temperature, use a cored wire solder and put it down on the iron tip. In a preferred way use Sn/Pb/Ag 62/36/2 alloy, wait until the solder fillet is formed on the capacitor’s termination, take away iron and wire solder, wait a few minutes so that the substrate and capacitor come back down to the preheating temperature, solder the second termination using the same procedure as the first, let the soldered component cool down slowly to avoid any thermal shock.   14. Packaging TAPE AND REEL The films used on the reels correspond to standard IEC 60286-3. Films are delivered on reels in compliance with document IEC 286-3 dated 1991. Minimum quantity is 250 chips. Maximum quantities per reel are as follows: Super 8 reel - Ø 180: 2,500 chips. Super 8 reel - Ø 330: 10,000 chips. Super 12 reel - Ø 180: 1,000 chips. Reel marking complies with CECC 32100 standard: Model. Rated capacitance. Capacitance tolerance. Rated voltage. Batch number.   15. Dimensional characteristics of chips tray packages   16. High Q Capacitors Tape and Reel Packaging Specifications   17. EIA standard capacitance values Following EIA standard, the values and multiples that are indicated in the chart below can be ordered. E48, E96 series and intermediary values are available upon request.   18. EIA capacitance code The capacitance is expressed in three digit codes and in units of pico Farads (pF). The first and second digits are significant figures of the capacitance value and the third digit identifies the multiplier. For capacitance value < 10pF, R designates a decimal point.  See examples below:   19. Part marking voltage codes Use the following voltage code chart for part markings: 20. Part marking Tolerance codes Use the following tolerance code chart for part markings:   21. Reliability levels Exxelia proposes different reliability levels for the ceramic capacitors for both NPO and X7R ceramics.   As the world’s leading manufacturer of specific passive components, we stand apart through our ability to quickly evaluate the application specific engineering challenges and provide a cost-effective and efficient solutions. For requirements that cannot be met by catalog products, we offer leading edge solutions in custom configuration: custom geometries, packaging, characteristics, all is possible thanks to our extensive experience and robust development process, while maintaining the highest level of reliability. Where necessary, special testing is done to verify requirements, such as low dielectric absorption, ultra-high insulation resistance, low dissipation factor, stability under temperature cycling or under specified environmental conditions, etc. > See our capacitors in catalog