Resistivity of Metallically Conducting Resistance and Contact Materials

B63: Standard Test Method for Resistivity of Metallically Conducting Resistance and Contact Materials

For engineers and designers working with materials critical to electrical performance, understanding and controlling electrical resistivity is paramount. ASTM B63 provides the authoritative framework for accurately measuring this fundamental property, ensuring the reliability and performance of resistance and contact materials in demanding applications.

What is B63?

ASTM B63 is a comprehensive standard test method for determining the electrical resistivity of metallic materials specifically intended for use in resistors, heating elements, and electrical contacts. Originating from established industry practices, its primary purpose is to provide a precise and repeatable procedure for material characterization, enabling informed material selection and quality assurance.

Scope & Purpose

This industry-leading standard governs the testing of metallically conducting materials used in applications where their electrical resistance characteristics are critical. This includes materials for resistive components and those forming electrical contacts. The scope is focused on the determination of resistivity to a precision of 2%, ensuring reliable data for design and manufacturing. It does not cover the resistivity of general electrical conductor materials, which are addressed by other ASTM standards.

Who Must Comply?

• • Primary audience: Materials Engineers, Metallurgists, Electrical Engineers, Quality Control Technicians, and R&D Scientists involved in the development and production of electrical components.
• • Industries affected: Electrical Equipment Manufacturing, Electronics, Aerospace, Automotive, and Materials Science Research.
• • Compliance nature: Voluntary, but highly recommended by industry for ensuring product quality and performance.
• • Enforcement: Typically checked during internal quality control processes, supplier qualification, and by customers during acceptance testing.

Key Requirements Overview

The standard outlines several crucial requirements for accurate resistivity measurement:

• • Specimen Preparation: It mandates specific requirements for test specimen dimensions and quality, depending on whether the material is ductile or non-ductile, to ensure accurate measurements.
• • Dimensional Accuracy: Professionals must ensure that specimen length and mean cross-sectional area are measured with high precision (within 0.5%) to achieve the overall 2% resistivity accuracy.
• • Resistance Measurement: The standard specifies the use of calibrated electrical measurement equipment (e.g., bridges, potentiometers, ohmmeters) capable of providing resistance readings with a low limit of error.
• • Lead Placement: For specimens with low resistance, specific guidelines are provided for the placement of current and potential leads to minimize contact resistance effects.
• • Density Determination: For non-ductile or porous materials, the standard provides proven methods for determining material density when direct dimensional measurements are insufficient for accurate cross-sectional area calculations.

Related Standards & References

ASTM B63 often works in conjunction with other ASTM standards. For instance, ASTM B193, Test Method for Resistivity of Electrical Conductor Materials, addresses a related but distinct area, focusing on materials primarily used for current conduction rather than resistance or contact applications. Understanding the nuances between these standards is crucial for precise material characterization.