Types and Methods
Bare copper alloy conductors will oxidize due to air exposure, heat, moisture and foreign chemical presence. This oxide, once present on the conductor surface, will prevent good, reliable connections. To prevent oxidation, a conductor can be coated with a material that will not oxide easily.
- Tin—The most commonly used due to processing ease and relatively low cost (up to 150°C).
- Silver—Commonly used in conjunction with insulations made with high temperature fluoropolymers, such as TFE, silver can meet high temperature requirements typically up to 200°C.
- Nickel—Used when service temperature exceeds 200°C—mainly aerospace and select military applications.
- Gold—Rarely used due to expense, gold has been applied when a flexible high conductivity coating was needed for aerospace control cable.
- Hot Dip—A method where the strand or strands is passed through a molten bath of coating material.
- Electroplating—Using the electrolysis method of bonding the coating metal to base conductor.
- Cladding—Welding under heat and pressure two or more dissimilar metals.
- Tinned or Heavy Tinned—This is the simple application of a coating material by the dip or electroplating methods. Typically 40 micro inches of tin remains on each strand and for heavy tin, 100 micro inches.
- Prefused—Sometimes called "Pre-bonded", this method takes heavy tinned strands and fuses them with heat when they are in a stranded conductor form to create a bonded conductor.
- Topcoated—After bare copper strands are cabled together, a layer of coating material, typically tin, is applied over the entire conductor, creating a bonded conductor.
- Overcoated—After coated copper strands are cabled together, a layer of additional coating material, typically tin, is applied over.