What Is a Wire Bonder?
A wire bonder is a device used to electrically bond a large number of I/O electrodes to the substrate side of integrated circuits such as IC chips and LSI chips. Wire bonders are also used to connect electrodes between printed circuit boards.
Although flip chip bonders have been widely used for mounting integrated circuits in recent years, there is still a need for wire bonding.
There are two types of wire bonders: the manual type, in which bonding is performed while observing the bonding with a microscope, and the fully automatic type, in which the bonding address is programmed in advance.
Uses of Wire Bonders
Wire bonders are mainly used in the assembly process, which is the back-end process of the semiconductor manufacturing process. The manual type described above is used for experimental and prototype board circuits, while fully automated wire bonders are used in the mass production process.
Wire bonders require high productivity because they connect electrodes on a one-to-one basis. For this reason, products that connect wires at a high speed of about 0.05p/s per wire bonding location have become mainstream.
Principle of Wire Bonders
Ultra-thin wires made of gold, aluminum, copper, or other materials are used to connect electrodes on the substrate and integrated circuits. Ultrasonic welding technology is used to bond each electrode and wire, and bonding is completed in a very short time. The part where the wires are passed and joined is called the head, of which there are several types depending on its structure.
Since wire bonders require wire bonding between extremely tiny electrodes, the positioning accuracy is extremely precise, requiring an accuracy error of ±2 microns. It also requires precise management and control of the pressing load (bonding load) of the head and is equipped with a non-rebound servo mechanism and anti-vibration system that suppresses external vibrations to achieve high positioning accuracy.
The wire bonding process can be broadly classified into two categories: wire bonding and wire bonding.
Wire bonding can be roughly classified into two methods: ball bonding, in which electric discharge is generated between the wire and electrode, forming a ball-shaped molten part on both sides, followed by pressure bonding while applying heat or ultrasonic waves, in which the wire is directly pressed by ultrasonic waves onto the electrode without forming a ball-shaped molten part. There is a method called wedge bonding, in which the wire is pressed directly to the electrode without forming a ball-shaped melted portion, using ultrasonic waves.
There is a wide range of wire diameters from tens of microns to several hundred microns in ribbon wire, and the bonding method must be selected according to the wire.