ASTM F14-80(R2019) pdf free download

ASTM F14-80(R2019) pdf free download.Standard Practice for Making and Testing Reference Glass-Metal Bead-Seal
1. Scope
1.1 This practice covers procedures for preparing and test- ing reference glass-to-metal bead-seals for determining the magnitude of thermal expansion (or contraction) mismatch between the glass and metal. Tests are in accordance with Test Method F218 (see Section 2). 1.2 This practice applies to all glass-metal combinations, established or experimental, particularly those intended for electronic components. 1.3 The practical limit of the test in devising mismatch is approximately 300 ppm, above which the glass is likely to fracture. 1.4 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 establish appro- priate safety, health, and environmental practices and deter- mine the applicability ofregulatory limitations prior to use. 1.5 This international standard was developed in accor- dance with internationally recognized principles on standard- ization established in the Decision on Principles for the Development of International Standards, Guides and Recom- mendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
3. Summary of Practice
3.1 Seals of a standard configuration are prepared from a representative sample of each metal and glass to be tested. Each material is prepared by an approved method and sized as specified. The seal is formed, annealed, and measured for optical retardation from which the axial stress and expansion mismatch are calculated. At least two specimens are required from which average values are obtained.
4. Significance and Use
4.1 The term reference as employed in this practice implies that both the glass and the metal of the reference glass-metal seal will be a standard reference material such as those supplied for other physical tests by the National Institute of Standards and Technology, or a secondary reference material whose sealing characteristics have been determined by seals to a standard reference material (see NIST Special Publication 260). 4 Until standard reference materials for seals are estab- lished by the NIST, secondary reference materials may be agreed upon between producer and user.
6. Materials
6.1 Metal—Representative rod stock with out-of-round not exceeding 1 % shall be selected, preferably with a diameter in the range 0.5 to 4 mm. Smaller diameters result in a loss of sensitivity and larger diameters tend to be cumbersome and impractical. Surfaces shall be relatively free of scratches, machine marks, pits, or inclusions that would induce localized stresses. Length requirements are discussed in 6.2. 6.2 Glass—Representative glass tubing of suitable optical transmission with an inside diameter 0.15 to 0.25 mm larger than the metal rod diameter. The outside diameter ofthe tubing shall preferably be such that it produces a glass-to-metal diameter ratio between 1.5 and 2. The length ofthe tubing shall exceed four times the finished glass diameter. The length ofthe metal rod must exceed the length of the tubing. Surface contaminants shall be removed to reduce the risk of making bubbly seals. An ultrasonic water mark is recommended.
7. Seal-Making Procedure
7.1 The seal may be made either by flame-working tech- niques or by heating the tubing-rod assembly in a furnace. In either case, rotation of the assembly is strongly recommended to maintain geometrical symmetry. For furnace sealing, 5 to 10 min at a temperature 100 °C above the softening point ofthe glass will generally produce a satisfactory seal. 7.2 When used as an acceptance test by producer and user, the number oftest seals representing one determination shall be established by mutual agreement. However two seals are a minimum requirement for one determination. 7.3 Upon completion of the seal making, determine the rod diameter, glass bead diameter and length, and record these data.