Beam Lead (BL) is a bare silicon chip, an early chip-scale package (CSP). Beam lead technology is a method of fabricating a semiconductor device. Its original application was high-frequency silicon switching transistors and high-speed integrated circuits. It eliminated the labor-intensive wire-bonding process used for integrated circuits at the time and allowed automated assembly of semiconductor chips onto larger substrates to produce hybrid integrated circuits.
In the early 1960s, M.P. Lepselter developed the techniques for fabricating a structure consisting of electroforming an array of thick, self-supporting gold patterns on a thin film Ti-Pt Au base, hence, the name “beams”, deposited on the surface of a silicon wafer. The excess semiconductor from under the beams was removed, thereby separating the individual devices and leaving them with self-supporting beam leads or internal chiplets cantilevered beyond the semiconductor. The contacts served as electrical leads in addition to also serving the purpose of structural support for the devices.