Wire bonding

Refers to the joining of aluminum, copper or gold wires to semiconductor surfaces or circuit carriers. This technique is usually used to connect the topside of chips to the circuit board. In power electronics, ultrasonic wedge-wedge bonding with aluminum bonding wires and a diameter of 300µm is the most commonly used process. The wedge guides the wire and applies ultrasonic energy. The actual joint is created by ultrasonic welding.

When bonding copper wires, a copper sheet usually has to be bonded to the semiconductors first for stress distribution, as copper is harder than aluminum and would otherwise damage the chip. When bonding gold wire, smaller wire diameters of 20 µm or less are used. The so-called ball-wedge process is used here. In this process, the gold wire is melted using electrical energy so that a ball is formed. This ball is then joined to the semiconductor by ultrasonic welding. The connection to the circuit carrier is then made using a wedge, as with aluminum wire bonding. This is why the process is also known as thermosonic ball-wedge bonding.

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