Solder resist coating adhesion to melting metal surfaces
(solder coating, tin/lead plating, etc.) cannot be assured, as
boards are subjected to temperatures that cause redistribution
of the melting metals. When solder resist coating is
required over melting metal surfaces, the maximum recommended
conductor width, where the coating completely
covers the conductor, shall be 1.3 mm.
When conductors of melting metal have a width larger than
1.3 mm, the design of the conductor shall provide a relief
through the metal to the base laminate substrate. The relief
should be at least 6.45 mm2 in size and located on a grid
no greater than 6.35 mm.