ASTM B735-16(2022) PDF
Standard Test Method for Porosity in Gold Coatings on Metal Substrates by Nitric Acid Vapor
Standard Test Method for Porosity in Gold Coatings on Metal Substrates by Nitric Acid Vapor
- Статус документа:
- Действующий
- Формат:
- Электронный (PDF)
- Количество страниц:
- 4
- Дата публикации:
- 1 октября 2022 г.
- Издание:
- B735
- ICS:
- 25.220.40
SIGNIFICANCE AND USE 5.1 Gold coatings are often specified for the contacts of separable electrical connectors and other devices. Electrodeposits are the form of gold that is most used on contacts, although it is also employed as clad metal and as weldments on the contact surface. The intrinsic nobility of gold enables it to resist the formation of insulating oxide films that could interfere with reliable contact operation. 5.2 In order that the nobility of gold be assured, porosity, cracks, and other defects in the coating that expose base-metal substrates and underplates must be minimal or absent, except in those cases where it is feasible to use the contacts in structures that shield the surface from the environment or where corrosion inhibiting surface treatments for the deposit are employed. The level of porosity in the coating that may be tolerable depends on the severity of the environment to the underplate or substrate, design factors for the contact device like the force with which it is mated, circuit parameters, and the reliability of contact operation that it is necessary to maintain. Also, when present, the location of pores on the surface is important. If the pores are few in number and are outside of the zone of contact of the mating surfaces, their presence can often be tolerated. 5.3 Methods for determining pores on a contact surface are most suitable if they enable their precise location and numbers to be determined. Contact surfaces are often curved or irregular in shape, and testing methods should be suitable for them. In addition, the severity of porosity-determining tests may vary. This test method is regarded as severe. 5.4 The relationship of porosity levels revealed by particular tests to contact behavior must be made by the user of these tests through practical experience or by judgement. Thus, absence of porosity in the coating may be a requirement for some applications, while a few pores on the critical surfaces may be acceptable for another. Such ac... SCOPE 1.1 This test method covers equipment and procedures for using nitric acid vapor for determining porosity in gold coatings, greater than 0.6 μm (25 μin.) in thickness, particularly electrodeposits and clad metals used on electrical contacts. 1.2 This test method is designed to show whether the porosity level is less or greater than some value that, by experience, is considered by the user to be acceptable for the intended application. 1.3 A variety of other porosity testing methods are described in Guide B765 and in the literature.2,3 Other porosity test methods are Test Methods B741, B798, B799, and B809. 1.4 The values stated in SI units are to be regarded as standard. The values given in parentheses are for information only. 1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to become familiar with all hazards including those identified in the appropriate Safety Data Sheet (SDS) for this product/material as provided by the manufacturer, to establish appropriate safety, health, and environmental practices, and determine the applicability of regulatory limitations prior to use. Specific precautions are given in Section 8 and 9.4. 1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Abstract
Overview
ASTM B735-16(2022) is the Standard Test Method for Porosity in Gold Coatings on Metal Substrates by Nitric Acid Vapor. Developed by ASTM International, this standard outlines the procedures and equipment for evaluating porosity in gold coatings, especially those used on electrical contacts and connectors. By applying nitric acid vapor to coated surfaces, the method reveals pores and defects that expose underlying base metals, providing key information on the integrity and durability of the gold coating.
Porosity in gold coatings can significantly impact electrical reliability and component longevity, particularly in demanding environments. Therefore, this test method is highly valued in industries where performance and reliability are critical.
Key Topics
- Porosity Detection: The standard specifies the use of nitric acid vapor to detect discontinuities such as pores, cracks, or other defects in gold coatings thicker than 0.6 μm (25 μin.). Reaction products formed at defect sites visibly indicate the location and number of pores.
- Applicability: Optimized for electrodeposited and clad gold coatings on metal substrates, particularly copper, nickel, and their alloys. The method accommodates complex geometries common in electrical contacts.
- Test Severity: This nitric acid vapor test is considered severe, suitable for applications that require a stringent assessment of porosity. It is not suitable for coatings thinner than 0.6 μm or metals less noble than gold.
- Interpretation: Allows users to determine whether the porosity is within acceptable limits based on experience and application requirements. It provides qualitative and quantitative data on pore distribution and severity.
- Health, Safety, and Environmental Considerations: The standard mandates proper handling and disposal procedures due to the use of corrosive acids, highlighting the importance of adherence to safety data sheets and appropriate lab practices.
Applications
ASTM B735-16(2022) is integral in several sectors including electronics, aerospace, communications, and critical electrical systems. The primary applications include:
- Quality Assurance: Ensures that gold coatings on connectors and contacts meet performance and reliability criteria by detecting porosity that might lead to corrosion or electrical failure.
- Product Development and Evaluation: Assists engineers and manufacturers in selecting appropriate gold plating processes or evaluating alternate coating solutions based on quantitative porosity data.
- Failure Analysis: Used for root cause investigations in cases of contact failure, enabling the identification of coating defects that compromise performance.
- Conformance Testing: Supports compliance with industry and customer requirements for gold-plated components, serving as an accepted standard method for porosity assessment during incoming inspections or lot release.
Related Standards
Several ASTM standards relate closely to ASTM B735-16(2022) and offer complementary test methods or terminology for porosity testing in metallic coatings:
- ASTM B374 - Terminology Relating to Electroplating
- ASTM B542 - Terminology Relating to Electrical Contacts and Their Use
- ASTM B741 - Test Method for Porosity in Gold Coatings on Metal Substrates by Paper Electrography (Withdrawn)
- ASTM B765 - Guide for Selection of Porosity and Gross Defect Tests for Electrodeposits and Related Metallic Coatings
- ASTM B798 - Test Method for Porosity in Gold or Palladium Coatings by Gel-Bulk Electrography
- ASTM B799 - Test Method for Porosity in Gold and Palladium Coatings by Sulfurous Acid/Sulfur-Dioxide Vapor
- ASTM B809 - Test Method for Porosity in Metallic Coatings by Humid Sulfur Vapor (“Flowers-of-Sulfur”)
These related documents can provide additional context or alternative methods suited to specific materials or application requirements.
Keywords: Porosity testing, gold coatings, nitric acid vapor test, electrical contacts, ASTM B735, plating reliability, metallic substrate analysis, connector porosity, quality control in electroplating
Технические детали
- Технический комитет
- B02 - Nonferrous Metals and Alloys
- SKU
- ASTM B735-16(2022)
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