Common Specifications for Tin Lead Plating

Electroplating is a common metal treatment for a variety of industries, and most times these industries have specifications that must be followed. Tin Lead Plating is a fairly common form of electroplating, and there are two basic specifications that are often referenced: the ASTM B579 specification and the MIL-P-81728 Specification. PEP General Metal Finishing can, of course, perform tin lead electroplating to either of these specifications.

About Tin Lead Plating

Tin-Lead plating is used often in the electronics industry and has a fair degree of popularity due to its combination of effectiveness and affordability. Pieces with a plating of tin and lead have a dull gray appearance. These pieces tend to have excellent solderability and the tin lead plating process inhibits whisker growth, which is of great concern to the high reliability electronics market. With over 40 years of experience, PEP General Metal Finishing can apply this type of plating in a variety of applications.

ASTM B579 Specification

This specification calls for plating with a 50 to 70 percent tin content, with the remainder being lead. Classes under this specification include SC4, with a minimum thickness of 30 um for steel or copper and SC3, with a thickness of 20 um for steel and 15 um for copper. For these two classes, an undercoat of 2.5 um copper is recommended. Two other classes under the ASTM B579 specification are SC2, with a thickness of 10 um for steel and 8 um for copper and SC1, with a thickness of 5 um for steel or copper.

MIL-P-81728 Specification

This specification also calls for a plating with 50 to 70 percent tin content, but it allows for up to one percent of the mix to be made up of other metals, with the remainder being lead. This specification does not require underplating except when applied over an alloy with 15 percent or more beryllium or zinc. In these cases, copper or nickel is the appropriate material for the underplating, to a thickness of 0.0001 inch. The thickness of the actual plating should generally be between 0.0003 inches and 0.0005 inches. In terms of finish, either a bright luster or a matte would be acceptable.

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