纳米金刚石涂层硬质合金微钻及其在封装基板上的应用

Nano-crystalline Diamond Coated Cemented Carbide Micro Drill and Its Application in Packaging Substrate

随着数据通讯讯号高频高速传输要求的提高,高性能芯片用封装基板的组成材料逐渐选用高硬度的陶瓷填料、改性玻纤布及改性树脂,特别是高比例无机陶瓷填料的添加给封装基板机械钻孔带来越来越严苛的挑战,钻头寿命急剧降低,且加工品质也得不到保障。为此,本文通过化学气相沉积方法,制作了极小直径的纳米金刚石涂层硬质合金印制电路板钻头,采用扫描电子显微镜和Raman光谱仪对涂层的微观组织进行了研究,采用日立20万转速高速钻机、高倍数码显微镜等仪器开展了涂层微型钻头的加工测试并对钻孔品质进行了评估。结果表明,金刚石涂层表面光滑、晶粒细小、组织致密,具有典型的纳米金刚石涂层特征;实验制作的金刚石涂层钻头加工高性能芯片用难加工封装基板HL832NSF(LCA-V)10万孔时,其后刀面最大磨损宽度仅为9.916μm,而普通未涂层钻头加工1 500孔时后刀面磨损宽度高达24.696μm,它表明金刚石涂层钻头具有很高的耐磨损性能;在相同的加工条件下,金刚石涂层钻头的加工寿命高达10万孔,是普通未涂层钻头寿命的60多倍,且其在该寿命时的孔位精度Cpk为1.925,孔壁粗糙度最大值7.543μm,加工品质完全满足封装基板的加工要求。

As the requirement is increased for high-frequency and high-speed transmission of data communication signals,more and more packaging substrate materials of chips with high performance are composed of ceramic fillers with high hardness,modified resin and modified glass fiber cloth.In particular,an increase in the proportion of inorganic ceramic fillers brings increasingly severe challenges to mechanical drilling of packaging substrates,which drastically reduces drill life and makes the processing quality fail to be guaranteed.In this paper,a nano-crystalline diamond coating was deposited on a cemented carbide micro drill with a rather small diameter for printed circuit board drilling by chemical vapor deposition.Further,a scanning electron microscope and a Raman spectrometer were employed to study the microstructure of the coating.A high-speed drilling machine (Maximum spindle speed up to 2×105r/min,Hitachi) and a high-magnification digital microscope were utilized in the machining tests of the coated micro drill and the evaluation of hole quality.The results reveal that the diamond coating has a small grain size with a smooth surface and a dense microstructure,which also has the characteristics of typical nano-crystalline diamond coatings.The flank wear of the diamond coated drill after 100 000 holes is 9.916μm wide when a difficult-to-machine packaging substrate named HL832NSF (LCA-V) is processed,while the flank wear of a conventional uncoated one is 24.696μm after 1 500 holes.This indicates that the diamond coated drill has excellent wear resistance.The service life of the diamond coated drill is up to100 000 holes,which is 60 times longer than that of the uncoated one under the same processing conditions.Meanwhile,the hole position accuracy Cpk is 1.925 and the maximum hole wall roughness is 7.543μm,which demonstrates that the processing quality of the diamond coated drill completely meets the processing requirements of packaging substrates.