超薄方型鋰電池鋁質薄殼雷射顯微封銲氣密品質之研究

Abstract

隨著無線通訊產品的普及，鋰離子電池的需求量持續呈高度成長，且不斷的朝薄型化、輕質化發展，殼體材料已由更輕的鋁合金取代過去所使用的不鋼，尺寸也突破以往的極限，但鋁合金的高反射率及高熱傳導率特性，使得超薄方型鋰電池外殼雷射封銲技術，遭受到相當高的困難與挑戰。 本研究使用最大平均功率40W之脈衝式Nd:YAG雷射系統，搭配機械手臂加工系統與自行設計之工件夾治具，成功地完成 AA 3003鋁質超薄方型鋰離子電池殼體微封銲作業，並藉由調整脈衝能量大小來進行不同重疊率下的銲道分析。結果顯示銲點直徑大小約為聚焦透鏡直徑的兩倍，且不隨脈衝能量改變，故在固定銲接走速為1 mm/sec時，重疊率僅與脈衝頻率有關。當重疊率大於60％以上時，銲道之氣孔和裂紋趨於穩定，此所對應之脈衝能量為17J以下。進而考慮銲深與銲道凹陷量，所 得最佳脈衝能量輸入值介於15~17J之間。

The quick development of the information and communication system has required small and portable equipment like cellular phones and notebook style computers. The important requirements of the battery for these applications are reliability, compactness and minimum weight. Lithium-ion batteries were commercialized and extensively used for portable equipment. Lightweight lithium-ion batteries for cellular phones have been developed using an aluminum alloy case. However, there are many problems in the laser microwelding of aluminum containers owing to the high reflection and high heat conductivity of aluminum alloy . The battery casing plays an important packaging role in maintaining an interior pressure to keep a good contact between the battery components. In this studyt, AA3003 aluminum alloy has been used as the material of Li-ion battery case. The Li-ion battery cases were sealed with a 40W pulsed Nd:YAG laser, combining with a 6-axis robot manufacturing system and a self-design fixture. The input energy of laser was adjusted to obtained different overlap rate in the welding line. The experimental results show that the diameter of weld spot is not related to the pulse energy, and which is about the double of the achromatic lens size. Therefore, the overlap rate should be concerned with pulse frequency in constant welding velocity 1 mm/sec. Furthermore, when the overlap rate is exceeded 60？HH, the porosity and cracking of welds are becoming stable. In these conditions, the corresponding pulse energy is under 17 J. Combining with the penetration and surface slumping of weld, the best pulse energy should be between 15 J and 17 J.