Cutting edge preparation of microdrills by shear thickening polishing for improved hole quality in electronic PCBs

doi:10.1007/s11465-024-0786-2

Front. Mech. Eng.

2024, Vol. 19

Issue (2) : 15 https://doi.org/10.1007/s11465-024-0786-2

Cutting edge preparation of microdrills by shear thickening polishing for improved hole quality in electronic PCBs

Jiahuan WANG^1,^2,³, Mingfeng KE^1,², Jiepei LIAO⁴, Yu ZHOU^1,², Saurav GOEL^3,⁵, Jaya VERMA³, Xu WANG^1,², Weigang GUO⁶, Julong YUAN^1,²(

), Binghai LYU^1,²(

)

¹. College of Mechanical Engineering, Zhejiang University of Technology, Hangzhou 310000, China
². Ultra-precision Machining Center, Key Laboratory of Special Purpose Equipment and Advanced Manufacturing Technology, Zhejiang University of Technology, Hangzhou 310000, China
³. School of Engineering, London South Bank University, London SE1 0AA, UK
⁴. Shenzhen Jinzhou Precision Technology Corporation, Shenzhen 518116, China
⁵. Department of Mechanical Engineering, University of Petroleum and Energy Studies, Dehradun 248007, India
⁶. Special Equipment Institute, Hangzhou Vocational & Technical College, Hangzhou 310018, China

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Abstract

Printed circuit boards (PCBs) are representative composite materials, and their high-quality drilling machining remains a persistent challenge in the industry. The finishing of the cutting edge of a microdrill is crucial to drill performance in machining fine-quality holes with a prolonged tool life. The miniature size involving submicron scale geometric dimensions, a complex flute shape, and low fracture toughness makes the cutting edge of microdrills susceptible to breakage and has been the primary limiting factor in edge preparation for microdrills. In this study, a newly developed cutting edge preparation method for microdrills was tested experimentally on electronic printed circuit boards. The proposed method, namely, shear thickening polishing, limited the cutting edge burrs and chipping on the cutting edge, and this in turn transformed the cutting edge’s radius from being sharp to smooth. Moreover, the edge–edge radius could be regulated by adjusting the processing time. PCB drilling experiments were conducted to investigate the influence of different cutting edge radii on wear, hole position accuracy, nail head value, and hole wall roughness. The proposed approach showed 20% enhancement in hole position accuracy, 33% reduction in the nail head value, and 19% reduction in hole wall roughness compared with the original microdrill. However, a threshold is needed; without it, excessive shear thickening polishing will result in a blunt edge, which may accelerate the wear of the microdrill. Wear was identified as the primary factor that reduced hole quality. The study indicates that in printed circuit board machining, microdrills should effectively eliminate grinding defects and maintain the sharpness of the cutting edge as much as possible to obtain excellent drilling quality. Overall, shear thickening polishing is a promising method for cutting edge preparation of microdrills. Further research and optimization can lead to additional improvements in microdrill performance and contribute to the continued advancement of printed circuit board manufacturing.

Keywords microdrill shear thickening polishing cutting edge preparation electronic printed circuit boards hole quality

Corresponding Author(s): Julong YUAN,Binghai LYU

About author:

#usheng Xing, Yannan Jian and Xiaodan Zhao contributed equally to this work.]]>

Just Accepted Date: 28 February 2024 Issue Date: 30 May 2024

Cite this article:

Jiahuan WANG,Mingfeng KE,Jiepei LIAO, et al. Cutting edge preparation of microdrills by shear thickening polishing for improved hole quality in electronic PCBs[J]. Front. Mech. Eng., 2024, 19(2): 15.

URL:

https://academic.hep.com.cn/fme/EN/10.1007/s11465-024-0786-2
https://academic.hep.com.cn/fme/EN/Y2024/V19/I2/15

Fig.1 Schematic of cutting edge preparation by shear thickening polishing: (a) macro and (b) micro views.

Tab.1 Experimental parameters

Fig.2 (a) Schematic of cutting edge preparation by shear thickening polishing and (b) illustration of the shear thickening polishing apparatus.

Tab.2 Drilling parameters used in the experiments

Fig.3 Schematic of the microdrilling system for processing the electronic printed circuit board. CNC: computer numerical control.

Fig.4 Influence of polishing time on the cutting edge radius.

Fig.5 Wear topography of the flank face: (a) illustration of the microdrill structure, (b) microdrill in Trial I after drilling 2000 holes, (c) microdrill in Trial II after drilling 2000 holes, (d) microdrill in Trial III after drilling 2000 holes, and (e) microdrill in Trial IV after drilling 2000 holes.

Fig.6 Statistics of the unworn area in the different trials.

Fig.7 Hole position accuracy in the different trials: (a) CPK statistics and (b) actual locations. 1 mil = 25.4 μm.

Fig.8 Nail heads in the different trials.

Fig.9 Images of the hole wall slices in (a) Trial I and (b) Trial II, and (c) statistics of hole wall roughness in the Trials I–IV.

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