wire bond

Wire bonding is the classic way to connect a chip to its package: thin gold, copper, or aluminium wires are stitched one at a time from pads on the edge of the die up and over to leads on the package, like a tiny sewing machine throwing a loop of thread between two posts. A bonding tool presses the wire against a pad, adds a dab of heat and a buzz of ultrasonic vibration to weld the metals together, then arcs across and welds the other end — hundreds of times per second.

It is cheap, forgiving, and dominates low-pin-count and cost-sensitive parts (sensors, microcontrollers, LEDs, memory). But the wires only reach the perimeter of the die, so pin count is limited; each loop adds inductance that hurts high-speed signals; and the loops take vertical space. That is why high-performance processors moved to flip-chip, while wire bond still ships in astronomical volume — most chips in the world are wire-bonded.