Component Rework With Low-Melt Alloy Solder
Original Publication Date: 1979-May-01
Included in the Prior Art Database: 2005-Feb-20
A dual solder alloy preform is used for the rework of individual components on printed-circuit boards. The preform consists of a thin bottom layer of a very low melting point (M.P.) solder, such as the eutectic of tin, lead, and bismuth (M.P. 208 degrees F), and a solder alloy top layer, such as SnBi (M.P. 281 degrees F), of sufficient volume and composition to produce a solder alloy of significantly lower melting point when combined with the solder already present in the plated through hole (PTH). A typical operating sequence is as follows: 1. Flux the PTH work site and apply the dual alloy preform. 2. Apply localized heat to the rework site, e.g., hot gas, until the bottom preform layer melts and is superheated about 253.