1. Ultrasonic metal spot welding of lithium-ion batteries
Because the positive electrode tab of a lithium-ion battery cell is made of aluminum strip, it cannot be directly soldered. Therefore, a nickel strip needs to be added. This is typically achieved using ultrasonic metal spot welding: the high-frequency oscillations of ultrasound cause localized high heat generation between the two metal strips through friction, fusing them together. Frequency: 20K~35KHZ; Time: approximately 0.*/S
When using ultrasonic welding machines for metals, it is important to select suitable welding equipment and to use appropriate welding parameters.
Prevent over-soldering of the positive electrode aluminum strip, otherwise it will easily break. Prevent loose welding of the positive electrode aluminum strip, otherwise the battery will easily disconnect.
2. Soldering connections in lithium-ion batteries
Key principle: The soldering iron heats up and melts the solder wire, causing the solder to adhere to the part being soldered. After cooling, the part is connected.
1) Soldering iron classification:
A. Internal heating type and external heating type. Internal heating type soldering iron heats up faster.
B. Ordinary soldering iron, temperature-adjustable soldering iron, anti-static constant temperature soldering iron.
2) Soldering iron power: 30W, 35W, 40W, 50W, 55W
60W, 65W, etc.
3) Soldering iron temperature: Set according to the solder area and the amount of solder used. If the temperature is too low, the solder wire will not melt quickly enough, affecting the soldering speed; if the temperature is too high, the solder joints will not be smooth. The soldering iron temperature is generally set at...
360℃±10℃
4) Welding posture: Be natural and upright.
5) Welding techniques: There are pen-grip method and straight grip method.
6) Welding angle: The welding angle using the pen-holding method is 30°~
Between 60 and 60 degrees, the optimal angle is 45 degrees between the soldering iron tip and the object being soldered.
7) Solder composition: Tin (Sn) 60~63%, Lead (Pb)
40-37%, rosin 1.0%-1.2%
Some companies are now starting to use lead-free solder.
8) Welding time: <3 seconds
9) Method: First place the soldering iron on the part to be soldered, then place the solder wire in the gap between the soldering iron tip and the part to be soldered.
10) Solder Amount: A suitable amount of solder is sufficient to cover the object being soldered. 10) Solder Quality: The solder joint should be bright, uniform, and firm, without bridging, missed solder joints, false solder joints, porosity, or delamination. The size of the solder joint is related to the amount of hot solder in contact.
3. Lithium-ion battery casing super-welding process and requirements
1) The encapsulation connection of the outer shell is generally achieved by ultrasonic plastic welding.
2) Working principle: The ultrasonic waves generate high-frequency oscillations, causing friction between the upper and lower shells. This results in a sharp rise in local temperature, leading to high heat. Plastic flow of the material will occur between the two parts, which will solidify under pressure to form a uniform weld.
3) Select a suitable ultrasonic welding machine.
4) Use appropriate welding parameters: Power factor: force × speed. Force includes pressure (air pressure) and descent speed. Speed includes frequency and amplitude. Energy = power × time. Frequency: 20kHz welding time, holding time.
5) Special attention should be paid to the size fit of the outer casing and protective plate to prevent them from being too tight or not fitting properly.
6) The thickness of the protective plate and the arrangement of components should fully consider the impact of ultrasonic waves to prevent components from being loosened by vibration.
7) Factors affecting welding results include: plastic materials, welding design, and molds.
8) Over-welding quality: No over-damage, no melted glue, no over-height, uniform weld lines, tight fusion, the sample is dropped from a height of 1m onto a wooden board, once on each of the X, Y, and Z sides (a total of six times), meeting the requirements.
