超大长径比极细硬质合金微型钻头结构及涂层技术研究

Research on the structure of ultra small cemented carbide micro drill with ultra high aspect ratio and the coating technology

针对超大长径比极细微型钻头工作中的微弯曲变形情况进行了分析。通过软件计算,得到微型钻头未钻入板材时不同旋转速度对微型钻头偏摆距离的影响。随后模拟微型钻头钻入板材后的受力情况,计算了微型钻头在槽长区域有、无约束条件下的变形量,研究了微型钻头槽长区域不同约束位置、约束方式对微弯曲变形的影响。研制了新型自对正结构的超大长径比极细微型钻头,并应用于加工8 mm大厚度高速通信印制电路板。利用两端对向钻削的方法对其进行通孔加工,研究了微型钻头的结构和涂层对孔偏距的影响。结果表明,钻入板材前,随着转速从150 kr/min增加到245 kr/min,钻尖偏摆距离从0.02 mm增加到0.6 mm;钻入板材后,在槽长区域设计约束结构可有效降低微弯变形量;通过超润滑涂层解决了极细微型钻头的断刀问题、减小了孔偏距。相比于常规结构的微型钻头,新型微型钻头涂层后可将孔偏距从56μm降低到35μm,满足使用要求。

The micro bending deformation of ultra small micro drill with ultra high aspect ratio was analyzed. The influence of different rotation speeds on the swing distance of the micro drill when it was not drilled into the plate is calculated by software. Then, the stress of the micro drill after drilling into the PCB was simulated, and the deformation of the micro drill in the flute length area with or without constraints was calculated. The influence of different constraint positions and constraint modes on micro bending deformation in the flute length area of micro drill was studied. A new type of micro drill with ultra high aspect ratio and a new self-aligning structure was developed and applied to machining the high communicating speed printed circuit board with 8 mm in thickness. Through hole machining is carried out by using the method of opposite drilling at both sides, and the influence of the structure of the micro drill and coating on the hole offset is tested. The result showed that the swing distance of drill bit increased from 0.02 mm to 0.6 mm as the rotation speed increased from 150 kr/min to 245 kr/min before the micro drill drilling into the board. After drilling into the board, the constraint structure was designed in the flute length area, which can effectively reduce the micro bending deformation. By preparing the super lubricating coating, the problem of tool breaking of ultra high micro drill was solved, and the hole offset was reduced simultaneously.Compared with the conventional micro drill, the coated new type micro drill can reduce the hole offset from 56μm down to 35μm, meeting the demand.