Co含量和微裂纹对WC喷嘴抗激光冲击性能的影响

Effect of Co Content and Microcracks on Laser Shock Resistance of WC Nozzle

以激光喷射锡球键合时使用的抗激光冲击性能存在明显差异的WC喷嘴为研究对象,借助扫描电子显微镜/能量色散X射线光谱仪对比观察了微观组织及成分之间的差异,结合材料与光束相互作用理论,研究了Co含量和微裂纹影响WC喷嘴抗激光性能的微观机制。测试结果显示,WC颗粒尺度、贯通状微裂纹和金属黏结剂Co含量存在明显不同。分析表明:因烧结压强过大引起的贯通状微裂纹会对激光产生“光陷”现象,并在其周围形成温度较高的热影响区,该区域内熔点较低的Co易于熔化;在喷嘴小孔前端热影响区附近,熔化后的Co和锡球容易发生冶金反应,形成沾锡,严重时喷嘴失效;裂纹越严重、Co含量越高,WC喷嘴的抗激光冲击性能越差。由此可知,降低Co含量和烧结压强,可以有效改善喷嘴的抗激光冲击性能。

Taking the WC nozzle with obvious difference in laser shock resistance performance used in laser jet solder ball bonding as the research object, the difference between microstructure and composition was observed by means of scanning electron microscope/energy dispersive X-ray spectrometer. Combined with the theory of material beam interaction, the micro mechanism of the influence of Co content and microcracks on the laser resistance of WC nozzle was studied. The test results show that WC particle size, through microcrack, and metal binder Co content are obviously different. The analysis shows that the through microcracks caused by excessive sintering pressure will produce light trapping phenomenon to the laser, and form a heat affected zone with higher temperature around it, in which the Co with lower melting point is easy to melt. Near the heat affected zone at the front end of the nozzle small hole, the molten Co and tin ball are prone to metallurgical reaction, forming tin, and the nozzle will fail in severe cases. The more serious the crack and the higher the Co content, the worse the resistance to laser shock of WC nozzle. Therefore, reducing Co content and sintering pressure can effectively improve the laser shock resistance of the nozzle.