The sealing performance of a Bluetooth headset button battery directly impacts its lifespan and safety. Especially with the trend towards miniaturization and high energy density, the packaging process requires a multi-dimensional technological collaboration to achieve reliable sealing. Core processes include laser welding, mold sealing, dual-sealing structures, and material optimization. These technologies collectively construct a complete sealing system from microstructure to macro-assembly.
Laser welding is one of the key processes for sealing button batteries. Traditional resistance welding is prone to sealing failure due to inaccurate weld size and oxidation blackening. Laser welding, however, uses a high-energy-density beam for non-contact processing, allowing precise control of the welding trajectory and penetration depth. For example, when welding the positive and negative electrodes of the core to the casing, the laser can penetrate highly reflective materials such as copper, forming a uniform molten pool and avoiding incomplete welds or casing penetration. During top cover sealing welding, the laser power and pulse width can be precisely matched to the 0.1mm thick casing and cover connection, ensuring weld strength and airtightness. Furthermore, laser welding equipment is equipped with a real-time monitoring system that detects energy fluctuations and molten pool morphology during the welding process, allowing for timely parameter adjustments and improving the welding success rate to over 99.5%.
The mold sealing process achieves sealing through physical deformation. The button battery sealing mold employs an upper and lower mold core structure. The sealing groove of the lower mold core gradually narrows inwards from the opening, with a ring-shaped heating element surrounding the outer side to evenly transfer heat to the outer casing. The pressing part of the upper mold core matches the sealing groove, and a heating element is also located on its outer side. During welding, after the outer and inner casings are initially joined, they are placed into the sealing groove. The upper mold core presses down, causing the outer casing to deform under heat and tightly fit against the inner casing, forming a mechanical locking structure. The mold core, made of high-polymer tungsten carbide, possesses high hardness and heat resistance, allowing it to withstand repeated sealing operations without deformation, ensuring reliable sealing during long-term use.
The double-sealing structure enhances the sealing level through multiple layers of protection. Taking a certain patented technology as an example, it adopts a composite structure of "sealing membrane assembly + sealing ring + support ring": the sealing membrane assembly consists of upper and lower sealing membranes, both with an area larger than the core package surface, which are joined at the edges to form a fold; the sealing ring is fitted onto the fold, cooperating with the upper and lower shells to form a closed cavity; the support ring wraps around the outside of the sealing membrane assembly, restricting core package displacement and dispersing sealing pressure. In this structure, the sealing membrane assembly wraps the core package through heat sealing to prevent electrolyte leakage; the tight fit between the sealing ring and the fold further blocks gas channels; the support ring prevents the upper and lower shells from squeezing the core package during sealing, reducing the risk of leakage. This three-layer protection allows the battery to maintain its sealing performance even under extreme environments such as high temperature and vibration.
Material optimization is the fundamental guarantee of sealing performance. Battery casings are typically made of stainless steel or aluminum alloy, and their surfaces undergo laser etching to increase surface roughness and improve weld adhesion. The separator material must have high porosity and low shrinkage to ensure uniform electrolyte wetting while preventing cracking after drying. The sealing film uses electrolyte-resistant polyimide or silicone, and its elastic modulus and coefficient of thermal expansion must match the casing to prevent gaps caused by temperature changes. Furthermore, battery assembly must be carried out in a drying room or glove box, with the dew point controlled below -40°C to prevent moisture from causing electrolyte decomposition or metal corrosion, ensuring reliable sealing from the outset.
Process control is the quantitative guarantee of sealing performance. Sealing pressure and time are key parameters that must be precisely set according to battery size and material characteristics. For example, the sealing pressure for a 12mm diameter button battery is typically controlled at 50-80N, and the sealing time at 0.5-1 second, ensuring that the casing deformation is within the range of 0.1-0.2mm, achieving an effective seal while avoiding excessive compression that could damage the internal structure. During assembly, airtightness testing is required to screen for defective products. The testing pressure is typically 0.5-1 MPa, with a holding time of 10-30 seconds. A pressure drop of less than 5% is considered acceptable.
The airtightness of the Bluetooth headset button battery is the result of laser welding, mold sealing, a double-sealing structure, and material optimization. These processes not only solve the challenge of sealing micro-batteries but also ensure mass production consistency through real-time monitoring and rigorous testing, providing a fundamental support for the long battery life and high reliability of Bluetooth headsets.
