[Dry goods] Wire bonding aluminum wire ultrasonic welding technology knowledge

[China Aluminum Network] 1. What is the wire bonding aluminum ultrasonic welding technology?
Ultrasonic welding of aluminum wire is actually a wire bonding technique using aluminum as a wire. Wire bonding is a primary internal interconnect method used as an internal interconnect to the actual die surface or the initial stage of a device logic circuit. This connection connects the logic signal or the chip's electrical signal to the outside world. Connect it.
There are two forms of wire bonding: ball bonding and wedge bonding. Gold wire ball welding is a more commonly used method. In this process, a molten gold ball is stuck on a section of wire and pressed down as a front solder joint, and then a curved wire is drawn from the previous solder joint and then used again. The moon shape connects the wire (second wedge weld) and then another new ball is formed for the next ball weld. Gold wire ball welding is classified as a thermoacoustic process, that is, solder joints are formed under the combined effect of heat (usually 150), ultrasonic waves, pressure, and time. The second type of pressure welding method is a wedge-shaped process. This process mainly uses aluminum wire, but gold wire can also be used, usually at room temperature. Wedge welding depresses the two wedge joints to form a joint. No balls are formed during this process. The aluminum wire welding process is classified as ultrasonic wire welding, and only the ultrasonic energy, pressure, and time are used to form the solder joint.
The use of different process types depends on the specific application. For example, gold wire pressure welding is used in mass production because of the faster process speed. Aluminum wire bonding is used when the package or PCB cannot be heated. In addition, the wedge-shaped pressure welding process has a finer pitch than the gold wire pressure welding. At present, the pitch limit of gold wire pressure welding is 60 Î¼m; a pitch of less than 60 Î¼m can be achieved with thin aluminum wire wedge welding.
The metal wire used in this technology, Bonding Wire, is an inner lead for making electrical connection between the input/output connection point of the intra-chip circuit and the inner contact point of the lead frame when the semiconductor device and the integrated circuit are assembled. Bonding Wire, as the connecting inner lead, should have the advantages of high conductivity, strong conductivity, strong bonding with conductive materials, and stable chemical properties. The diameter of Bonding Wire is usually between 25 and 75 Î¼m. There are four main materials on the market for Bonding Wire, namely gold, silver, copper and aluminum.
Second, Wire Bonding technology in the field of electric vehicle power battery
Wire bonding has been widely used in microelectronics and power electronics since 1970. Currently Wire bonding technology has a new application field, namely the growing electric vehicle field, especially in battery connection. In the production process of some electric vehicles, Wire bonding technology is used for connection between battery packs.
(a) Since Wirebond was widely used in microelectronics in 1970, some electric car manufacturers began to apply Wire bonding to battery connections.
TESLA is a typical company that uses this technology. In 2006, TESLA pioneered the use of wire bonding technology as a technology model for connecting batteries into a large battery pack. According to TESLA, the traditional welding process is time consuming and prone to failure. At the same time, it is also difficult to test whether there is a problem with the connections and conductors between the batteries.
In addition to the simple connection, TESLA has also designed a way to use aluminium wire bonding, which is a fusible joining technology. Aluminum wire welding technology allows the passage of current in the range, but it will be blown when overcurrent occurs due to a short circuit. TESLA's engineers believe that other welding techniques will create electrical protection problems, there is no fuse protection, a single cell may cause an internal short circuit after failure or damage, resulting in other batteries in parallel with it can not be used.
(B) Advantages:
Traditional brazing and fusion welding technologies have been used for many years and have some disadvantages. For example, the generation of thermal stress, post-weld cleaning problems, lack of flexibility, and difficult to control quality. Bonding's wire and tape welding performs much better than conventional welding in this regard, and it is possible to control each weld well without any adverse effects on the production process.
1. When using aluminum or aluminum ribbon welding, it can be done at room temperature. No external temperature is required, and the welding zone temperature during ultrasonic friction welding does not increase. Other traditional welding methods require heat to melt the metal.
2. Wire bonding is a clean welding technique that does not require any post-weld hygiene cleanup. After the traditional welding technique, there will be some flux residue or melted metal explosives that need to be removed to avoid reliability problems. Wire bonding requires cleaning only if there are some contaminants or stubborn oxides on the surface.
3. Wire bonding has good flexibility, strong compatibility, including low gold wire height, multiple pin selection, large working range, strip or round wire selection.
4. The wire can have good directional flexibility and can well control the mismatch between various thermal expansion parameters.
5. Lead connection technology,bonding wire can be directly used as a fuse process, without the need for resistance welding of nickel, simplifying the production process and reducing equipment investment.

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