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FR-2 (Flame Resistant 2) is a NEMA designation for synthetic resin bonded paper, a composite material made of paper impregnated with a plasticized phenol formaldehyde resin, used in the manufacture of printed circuit boards. Its main properties are similar to NEMA grade XXXP (MIL-P-3115) material, and can be substituted for the latter in many applications.
Applications
editFR-2 sheet with copper foil lamination on one or both sides is widely used to build low-end consumer electronic equipment. While its electrical and mechanical properties are inferior to those of epoxy-bonded fiberglass, FR-4, it is significantly cheaper. It is not suitable for devices installed in vehicles, as continuous vibration can make cracks propagate, causing hairline fractures in copper circuit traces. Without copper foil lamination, FR-2 is sometimes used for simple structural shapes and electrical insulation.
Properties
edit| Property | Value |
|---|---|
| Dielectric constant, or relative permittivity | 4.5 @ 1 MHz |
| Dissipation factor | 0.024–0.26 @ 1 MHz |
| Dielectric strength | 29 kV/mm (740 V/thou) |
Fabrication
editFR-2 can be machined by drilling, sawing, milling and hot punching. Cold punching and shearing are not recommended, as they leave a ragged edge and tend to cause cracking. Tools made of high-speed steel can be used, although tungsten carbide tooling is preferred for high volume production.
Adequate ventilation or respiration protection are mandatory during high-speed machining, as it gives off toxic vapors.
Trade names and synonyms
editSee also
editReferences
edit- ^ a b c d e f g Mehdorn, Walter (1949). Kunstharzpreßstoffe und andere Kunststoffe - Eigenschaften, Verarbeitung, Anwendungen (PDF) (in German) (3 ed.). p. 240. doi:10.1007/978-3-662-12205-1. ISBN 978-3-662-12206-8. Archived (PDF) from the original on 2021-03-20. Retrieved 2021-03-20. (viii+355 pages)
- ^ "lamitec.de". Archived from the original on 2006-08-04. Retrieved 2006-08-05.
- ^ "Pertinax – ein traditionsreiches Material mit neuer Zukunft" (in German). Müller Ahlhorn. 2014-01-06. Archived from the original on 2020-12-03. Retrieved 2021-03-20.
Further reading
edit- Industrial Laminated Thermosetting Products. National Electrical Manufacturers Association (NEMA). 2012-02-01 [2011, 1998]. NEMA LI 1-1998 (R2011).