Page 1 Rogers RT/duroid® laminates, TMM® laminates, RO3000® materials and RO400

Page 1 Rogers RT/duroid® laminates, TMM® laminates, RO3000® materials and RO4000® materials have key electrical and mechanical properties designers use to select the ideal material for a particular application. These properties are listed on our data sheets, selector guide and website. For those who are not design engineers, what the values and units represent may not be easily understood. The test methods used to determine these values might not be known, and the impact these properties have on design may not be readily evident. The purpose of this properties guide is to define each key property, how we test it and how each property is critical to design. High Frequency Circuit Materials Properties Guide Featured in this guide: • Key Properties Definitions • Key Properties Aliases • Symbols • Units of Measure • Target Ranges • Test Methods • Design Criteria • Conversion Tables Table of Contents Dielectric Constant ................................................................................................................. page 2 Dissipation Factor..................................................................................................................... page 2 Insulation Resistance ............................................................................................................... page 3 Volume Resistivity ..................................................................................................................... page 3 Surface Resistivity ..................................................................................................................... page 3 Thermal Coefficient of Dielectric Constant ......................................................................... page 4 Dielectric Strength ................................................................................................................... page 4 Young’s Modulus...................................................................................................................... page 5 Compressive Modulus ............................................................................................................. page 5 Flexural Modulus....................................................................................................................... page 5 Moisture Absorption ................................................................................................................ page 6 Thermal Conductivity .............................................................................................................. page 6 Coefficient of Thermal Expansion ......................................................................................... page 7 Peel Strength ............................................................................................................................ page 7 Glass Transition Temperature ................................................................................................. page 8 Dimensional Stability................................................................................................................ page 8 Flammability Rating ................................................................................................................. page 9 Impact, Notch Izod ................................................................................................................. page 9 Acknowledgements ................................................................................................................ page 9 Conversion Tables.................................................................................................................. page 10 Key Properities Main Chart ................................................................................................... page 11 The world runs better with Rogers.™ Advanced Circuit Materials Division 100 S. Roosevelt Avenue Chandler, AZ 85226 Tel: 480-961-1382, Fax: 480-961-4533 www.rogerscorporation.com Page 2 DEFINITIONS Dielectrics are materials that do not conduct electricity, that is, they are insulators. In the most fundamental electrostatic terms, two quantities of electrical charge, Q and Q’, in free space (vacuum) at a given distance, r, will repel each other with a mechanical force, F, by the relationship where the value of ε is the absolute permittivity of free space, ε0, that is, the smallest possible value. Replacing free space with a dielectric reduces the force in proportion to its value of ε. If Q and Q’ have the same sign (+ or –), then the value of F is positive, indicating repulsion. If they differ, then F is negative, indicating attraction. The ratio of ε to ε0 is called the relative permittivity or dielectric constant, Dk. Any dielectric other than a vacuum has the internal capability of responding by limited charge separation to the electric field imposed by the Q and Q’ charges, thus reducing the force. This charge separation is also called a dipolar response. Another way to view this is to imagine two metal plates at a fixed separation in a vacuum with a constant voltage from an external source between them. Voltage represents potential energy of an electrical charge. Current represents the movement of electrical charge. Move the plates closer and current must flow to increase the charge to keep the same voltage. Move a high dielectric DIELECTRIC CONSTANT and DISSIPATION FACTOR constant insulator between them and again current must flow to keep the same voltage. The ratio of electrical charge to voltage is referred to as capacitance of the system of plates and separation. Dielectric constant is the ratio of capacitance for a system having a dielectric insulator versus having a vacuum. Suppose an alternating sinusoidal voltage is applied to the plates. The amount of alternating current associated with the voltage is proportional to the capacitance. At an instant when the voltage is greatest the current is at zero and changing direction, and when the current is greatest the voltage is at zero and changing sign. Current and voltage are out of phase by one quarter of the sinusoidal cycle in an ideal system with no dissipation of energy. In a real system there will be some degree of electrical energy converted to heat because of resistance to current flow in the conductors and of resistance to dipolar response to voltage in the insulator. The loss in the insulator is referred to as dissipation factor. It is the ratio of energy loss in the dielectric to energy stored in the dielectric per cycle. The frequency of the alternating voltage and current is the number of sinusoidal cycles per unit of time. As frequency is increased, we can expect to see changes in the way the insulation responds and thus the values for dielectric constant and dissipation factor can vary with frequency. This is why we measure insulating materials near the frequency at which they are to be used. KEY ALIAS SYMBOL UNIT OF MEASURE UNITS PROPERTY Dielectric Relative K’, DK, εr Ratio of the None Constant Permittivity permittivity of a substance to the permittivity of free space. Dissipation loss tangent tan δ Ratio of loss to None Factor tanδ, approx DF capacity power factor K’’/K’ Page 3 INSULATION RESISTANCE/VOLUME RESISTIVITY/SURFACE RESISTIVITY DEFINITION Insulation resistance is the measure of the material’s ability to resist the flow of current through it. Surface resistivity is the resistance to leakage current along the surface of an insulating material. Volume resistivity is the resistance to leakage current through the body of an insulating material. The higher the surface/volume resistivity, the lower the leakage current and the less conductive the material is. DIELECTRIC CONSTANT and DISSIPATION FACTOR - continued TESTING There are several methods for measuring dielectric constant and dissipation factor at the microwave frequencies of interest including:
Stripline Resonator Method, IPC-TM-650 2.5.5.5 (8-12.4 GHz)
Long Stripline (LSL), IPC-TM-650 2.5.5.5.1 (1-14 GHz)
Full Sheet Resonance (FSR), IPC-TM-650 2.5.5.6
Damaskos, Inc. Cavity Resonator Rogers Corporation utilizes the Stripline Resonator Method (IPC-TM-650 2.5.5.5) when testing production laminates for quality control purposes. This method is considered the “standard” test method for most of the high frequency industry due to the ability to perform rapid measurements with the same test set-up. The stripline circuit consists of a resonator pattern card between two laminate samples etched to remove cladding. Advantages of this method include the ability to perform rapid measurements, an uncomplicated procedure and being operator independent. DESIGN G. Robert Traut (who developed the Long Stripline test method) explains why measurements matter: “Users fabricate our microwave circuit materials into devices which guide and process cyclic microwave signals whose wavelength is small compared to the device…Many design features are built around the expected wavelength and won’t work as planned if the wavelength deviates from the expected value…In almost every microwave system, it is very desirable to keep dissipation of energy down to minimize heat generation, to avoid more costly components for signal generation or amplification, to raise the sensitivity or signal to noise ratio. For transmission line elements in a device, [dielectric constant] affects both wavelength and characteristic impedance (Z0), with an inverse square root proportionality. Changes in Z0 give rise to reflections of the signal… Thus successful products for these users must have low [dissipation factor] and tightly controlled [dielectric constant] values.” In other words, tightly controlled dielectric constant values are required because it affects wavelength and characteristic impedance, two critical components when designing RF circuitry. A large K’ tolerance could cause unwanted reflections within the design. Dissipation factor must be minimized to avoid heat generation and having to add extra components. KEY ALIAS SYMBOL UNIT OF MEASURE UNITS PROPERTY Insulation - - Resistance Gohm Resistance Volume - ρ v Resistance length Mohm-cm Resistivity Surface - ρs Resistance Mohm Resistivity Page 4 THERMAL COEFFICIENT OF DIELECTRIC CONSTANT DEFINITION TCK’ is a measure of how the relative permittivity (dielectric constant) is affected by changes in temperature. TESTING The Stripline Resonator Method, IPC-TM-650 2.5.5.5 is used to measure the dielectric constant where the test fixture is mounted in a thermostatically controlled oven programmed to vary in steps from minus 50°C to plus 150°C. DESIGN Temperature changes can greatly affect the dielectric constant property depending on the dielectric material used in the laminate. Changes in the dielectric constant can affect signal integrity and cause unstable performance within the design. INSULATION RESISTANCE/VOLUME RESISTIVITY/SURFACE RESISTIVITY - continued TESTING Surface and volume resistivity are measured using the test method specified by IPC-TM-650 2.5.17.1. This test method involves a sample etched with a specified conductor pattern and test electrodes attached. A potential of 500 volts direct current is supplied to the sample in a controlled environment (due to correlation between resistivity and temperature/humidity) and the surface and volume resistivity is measured. The surface and volume resistivity values are then calculated using these measured values. DESIGN Resistivity of a dielectric material is critical to design because it affects electrical performance of the signal. The important factor is to ensure there is no leakage through the dielectric, so high values of resistivity are ideal. The composition of the dielectric material will determine the surface and volume resistivity. DIELECTRIC STRENGTH KEY ALIAS SYMBOL UNIT OF MEASURE UNITS PROPERTY Thermal Thermal TCK’ Concentration per ppm/°C Coefficient of Coefficient temperature Dielectric of εr Constant uploads/Voyage/ properties-guide-pdf.pdf

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• Détails
• Publié le Apv 18, 2022
• Catégorie Travel / Voayage
• Langue French
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