What is aluminum ultrasonic wire bonding technology?
Automatic ultrasonic wire bonding machine is a welding machine that uses aluminum as a metal wire.Wire bonding is a primary internal interconnection method used as the initial level of internal interconnection to the actual die surface or device logic circuitry, which connects the logic signals or electrical signals of the chip to the outside world.
Wire bonding has two forms: ball welding and wedge welding. In this process, a molten gold ball is glued to a section of wire, pressed down and used as the first solder joint, then a bent wire is drawn from the first joint and attached to the wire in the shape of a crescent moon (a second wedge-shaped joint), and another new ball is formed for the next first ball joint. Gold wire ball welding is classified as a thermoacoustic process, meaning that the joint is formed by a combination of heat (typically 150), ultrasound, pressure and time. The second pressure welding method is the wedge process, which uses mainly aluminum wire, but also gold wire, usually at room temperature. Wedge welding presses down two wedge-shaped joints to form a joint, and no balls are formed in this process. The aluminum wire welding process is classified as ultrasonic wire welding, where only the parameters of ultrasonic energy, pressure and time are used to form the welded joint.
The use of different process types depends on the specific application. For example, wire pressure welding is used in mass production. Because this process is faster. Aluminum wire pressure welding is used for dry packaging or occasions where PCB cannot be heated. In addition, the wedge pressure welding process has a finer spacing than the wire pressure welding. At present, the spacing limit of wire pressure welding is 60pm; The spacing of less than 60pm can be achieved by using thin aluminum wire wedge pressure welding.
Bonding wire is an electrical lead used in the assembly of semiconductor devices and integrated circuits to make an electrical connection between the input/output connection point of the circuit inside the chip and the internal contact point of the lead frame. The diameter of Bonding Wire is usually between 25 and 75 pm. There are four main materials available in the market for Bon ding Wire, namely gold, silver, copper and aluminum.
Wire bonding technology in the field of electric vehicle power battery
Wire bonding has been widely used in the field of microelectronics and power electronics since 1970. Now Wire bonding technology has a new field of application, namely the growing field of electric vehicles, especially for battery connections. Wire bonding is used in the production of some electric vehicles for the connection between battery packs.
（一）Since the widespread use of wire bonding in microelectronics in 1970, some electric vehicle manufacturers have been using wire bonding for battery connection.
In 2006, TESLA pioneered the use of wire bonding as a model for connecting cells into a large battery pack. In TESLA's view, the traditional soldering process was time consuming and prone to failure. It is also difficult to test the connections between cells and conductors for problems. In addition to simple connections, TESLA has also designed a way to use Aluminum wire bonding, a fusible connection technology. TESLA engineers believe that other bonding techniques create electrical protection problems, and that without fuse protection, a single cell can become internally short-circuited after a failure or damage, rendering all other cells connected in parallel with it unusable.
（二）Advantages
Traditional brazing and fusion welding techniques have been used for many years and have some disadvantages. For example, the generation of thermal stresses, post-weld cleaning problems, lack of flexibility and difficulty in quality control, etc. Wire bonder's wire and tape welding performs much better than conventional welding in this respect and allows good control of each weld without any adverse effects on the production process.
- When aluminum wire welding or aluminum strip welding is used, it can be carried out at room temperature. No external temperature is required, and the temperature of the welding zone will not rise during ultrasonic friction welding. Other traditional welding methods require heating to melt the metal.
- Wire bonding is a clean welding technology and does not require any cleaning after welding. After the traditional welding technology, there will be some flux residues or molten metal explosives that need to be removed to avoid reliability problems. Wire bonding requires cleaning only when there are some pollutants or stubborn oxides on the surface.
- Wire bonding has good flexibility and strong compatibility, including low wire height, multi-pin selection, large working range, ribbon or circular wire selection.
- The wire can have good flexibility in direction and can control the mismatch between various thermal expansion parameters.
- Lead wire connection process, bonding wire can be directly used as fuse process, without resistance welding of nickel sheet in use, simplifying production process and reducing equipment investment.
- Wire bonding machine adopts digital automatic frequency tracking ultrasonic system, digital control pressure regulation function, first-class image recognition equipment and full closed-loop motion control circuit, and is widely used in the connection of battery, cell and bus aluminum wire in the new energy automobile industry.
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