▎ 摘　　要

NOVELTY - Solder composition comprises a compound layer comprising an alloy of bismuth and tin, and a graphene coating positioned on the compound layer. USE - Solder composition used in solder joints of printed circuit board. ADVANTAGE - The solder composition has melting temperature of 150℃ and grain size of less than 50 micrometer. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for: a printed circuit board; and a method for depositing a solder joint composition on a printed circuit board by depositing an alloy comprising bismuth and tin on PCB to form a compound layer; melting alloy to form a solder ball joint on the PCB; and coating the compound layer with graphene.