The CCS integrated busbar mainly consists of signal acquisition components (FPC/FFC/FDC/wire harness, etc.), plastic structural parts, aluminum bars, connectors, and other components. In addition to the mainstream connecting piece laser welding for connecting the signal acquisition component FPC with the aluminum bar, there are also new processes such as ultrasonic direct welding, as well as lesser-known wire bonding technologies, etc
As shown in Figure 1,the mainstream connecting piece laser welding process requires pre-welding a connecting piece (usually a nickel piece) on the FPC, and then welding the other end of the connecting piece on the aluminum bar to form a connection. The welding of the connecting piece and the FPC needs to adopt the reflow soldering process, which is complex and has a high cost.
As shown in Figure 2,the ultrasonic direct welding process extends the copper foil on the circuit board and directly welds it with the aluminum bar using the ultrasonic welding process, which can simplify the process and reduce costs.

Figure 1: CCS Module Connected by Nickel Plate

Figure 2 : CCS Integrated Busbar with Direct Welding between FPC and Aluminum Bar

Application of Wire Bonding Technology in Battery Connection

Figure 3: Structure of Wire Bonding (When the carrier is a Printed Circuit Board (PCB))

Since the 1970s, wire bonding technology has been widely used in the microelectronics and power electronics industries. Now it also has new applications in the continuously developing electric vehicle industry. For example, in the connection of single cells and busbars, a very famous application case is that Tesla took the lead in using aluminum wire bonding technology to achieve 18650 battery cell grouping in 2006. In addition to realizing the series and parallel connection of battery cells, the bonded aluminum wire can also act as a fuse in the event of battery overcurrent, playing the role of melting protection to ensure the safety and stability of the battery.

Figure 4 : Aluminum Wire Bonding Process of Model 3/Y

In addition to Tesla, many battery factories in China have also introduced this technology. For example, the battery used in Xpeng G3 also adopts aluminum wire bonding technology.
The main form of aluminum wire bonding technology for battery connections is wedge bonding, which is usually carried out at room temperature, and a connection is formed by pressing down two wedge-shaped welding points. 
The application of aluminum wire bonding technology in battery connections has the following advantages:
The aluminum wire can serve as both a power connection and a fuse. In the event of a short circuit, it will automatically blow, ensuring the safety of the battery pack;
The aluminum wire can meet the stress requirements and tensile testing requirements for battery connections, with high reliability;
The use of aluminum wire bonding can achieve repeated welding, greatly improving maintainability and recovery rate;
When using aluminum wire or aluminum strip welding, the temperature in the welding area will not increase;
Aluminum wire bonding is a clean welding process without flux residues or molten metal slag, avoiding reliability problems;
It is easy to detect whether there are welding defects when welding with aluminum wire, and it is easier to repair the defect location without causing welding damage;
The lead wire bonding process is mature, has a low cost, and the process is very flexible.

The application of aluminum wire bonding technology in battery pack production is not limited to the connection between battery cells and busbars. It can also be used for sampling connections of CCS integrated busbars. 
The application of bonding technology on CCS integrated busbars mainly refers to connecting FPC/PCB and aluminum bars through aluminum wires or aluminum strips by bonding process, to realize voltage sampling of each individual battery. Among them, the two ends of the aluminum wire or aluminum strip are respectively bonded with the solder pads on the FPC and the electrical connection pieces. The bonded aluminum wire/aluminum strip has an arched structure with a gentle transition, which can avoid stress concentration and is prone to fracture. The combination of FPC and bonding process, using aluminum wire/aluminum strip instead of the mainstream nickel sheets, can reduce costs in terms of materials.

Figure 5 : Aluminum wire welding connects the single board with the battery cell.

Figure 6 : CCS Busbar with Aluminum Wire Bonding