Why the connections sit beneath the chip
A ball grid array (BGA) places electrical connections in a grid across the underside of a chip. This uses space that would otherwise be lost to rows of pins around the edges, allowing many connections in a compact footprint. It also means the joints are hidden once the chip is mounted.
Each ball meets a matching metal pad on the circuit board. During assembly, heat brings the solder to its melting point. The liquid solder wets the metal surfaces—spreading across them rather than staying as a loose bead—and forms an electrical and mechanical connection. As it cools, it hardens into a joint.
Why repair takes controlled heat
To remove or replace a BGA chip, a technician must heat the solder beneath it enough to melt while avoiding damage to the chip, board, and nearby components. Heat applied unevenly can leave some joints solid while others melt, or expose the board to damaging temperature changes. The chip must also be positioned accurately so its grid meets the board’s pads when the solder flows.
Because the finished joints are hidden, a chip can appear seated even when a connection underneath has failed. Inspection may therefore require specialized methods, such as X-ray imaging, rather than a simple visual check. The same compact layout that saves board space makes BGA work demanding: the critical connections are numerous, small, and out of sight.
