In integrated circuit packaging, a solder ball, also known as a solder bump (often referred to simply as "ball" or "bumps") is a ball of solder that provides the contact between the chip package and the printed circuit board, as well as between stacked packages in multichip modules; in the latter case, they may be referred to as microbumps (μbumps, ubumps), since they are usually significantly smaller than the former. The solder balls can be placed manually or by automated equipment, and are held in place with a tacky flux.
A coined solder ball is a solder ball subject to coining, i.e., flattening to a shape resembling that of a coin, to increase contact reliability.