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
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.
L J Zheng, C Y Wang, L P Yang, Y X Song, L Y Fu. Characteristics of chip formation in the micro-drilling of multi-material sheets. International Journal of Machine Tools & Manufacture, 2012, 52(1): 40–49 https://doi.org/10.1016/j.ijmachtools.2011.08.017
2
L P Khoo, K M Loh. A genetic algorithms enhanced planning system for surface mount PCB assembly. The International Journal of Advanced Manufacturing Technology, 2000, 16(4): 289–296 https://doi.org/10.1007/s001700050159
3
N Geier, K Patra, R S Anand, S Ashworth, B Z Balázs, T Lukács, G Magyar, P Tamás-Bényei, J Y Xu, J P Davim. A critical review on mechanical micro-drilling of glass and carbon fibre reinforced polymer (GFRP and CFRP) composites. Composites Part B: Engineering, 2023, 254: 110589 https://doi.org/10.1016/j.compositesb.2023.110589
4
Q L An, J Q Dang, J L Li, C Y Wang, M Chen. Investigation on the cutting responses of CFRP/Ti stacks: with special emphasis on the effects of drilling sequences. Composite Structures, 2020, 253: 112794 https://doi.org/10.1016/j.compstruct.2020.112794
5
J Q Dang, F Zou, X J Cai, Q L An, W W Ming, M Chen. Experimental investigation on mechanical drilling of a newly developed CFRP/Al co-cured material. The International Journal of Advanced Manufacturing Technology, 2020, 106(3–4): 993–1004 https://doi.org/10.1007/s00170-019-04659-1
6
F Zou, J Q Dang, Q L An, M Chen. Mechanism and feasibility study of low frequency vibration assisted drilling of a newly developed CFRP/Al co-cured material. Journal of Manufacturing Processes, 2021, 68: 115–127 https://doi.org/10.1016/j.jmapro.2021.05.020
7
H S Yoon, R Z Wu, T M Lee, S H Ahn. Geometric optimization of micro drills using Taguchi methods and response surface methodology. International Journal of Precision Engineering and Manufacturing, 2011, 12(5): 871–875 https://doi.org/10.1007/s12541-011-0116-6
8
X Y Qiu, Z Yu, C P Li, Q L Niu, S J Li, P N Li, T J Ko. Influence of main cutting edge structure on hole defects in CFRP/titanium alloy stacks drilling. Journal of Manufacturing Processes, 2021, 69: 503–513 https://doi.org/10.1016/j.jmapro.2021.07.061
9
S Sahoo, A Thakur, S Gangopadhyay. Application of analytical simulation on various characteristics of hole quality during micro-drilling of printed circuit board. Materials and Manufacturing Processes, 2016, 31(14): 1927–1934 https://doi.org/10.1080/10426914.2016.1140189
10
B Bhandari, Y S Hong, H S Yoon, J S Moon, M Q Pham, G B Lee, Y C Huang, B S Linke, D A Dornfeld, S H Ahn. Development of a micro-drilling burr-control chart for PCB drilling. Precision Engineering, 2014, 38(1): 221–229 https://doi.org/10.1016/j.precisioneng.2013.07.010
11
L J Zheng, C Y Wang, X Zhang, X Huang, Y X Song, K F Wang, L Q Zhang. The tool-wear characteristics of flexible printed circuit board micro-drilling and its influence on micro-hole quality. Circuit World, 2016, 42(4): 162–169 https://doi.org/10.1108/CW-08-2015-0040
12
L J Zheng, C Y Wang, L Y Fu, L P Yang, Y P Qu, Y X Song. Wear mechanisms of micro-drills during dry high speed drilling of PCB. Journal of Materials Processing Technology, 2012, 212(10): 1989–1997 https://doi.org/10.1016/j.jmatprotec.2012.05.004
13
F J Wang, B W Qian, Z Y Jia, R Fu, D Cheng. Secondary cutting edge wear of one-shot drill bit in drilling CFRP and its impact on hole quality. Composite Structures, 2017, 178: 341–352 https://doi.org/10.1016/j.compstruct.2017.04.024
14
D S Raj, L Karunamoorthy. A new and comprehensive characterisation of tool wear in CFRP drilling using micro-geometry and topography studies on the cutting edge. Journal of Manufacturing Processes, 2018, 32: 839–856 https://doi.org/10.1016/j.jmapro.2018.04.014
15
X Lei, B Shen, L Cheng, F Sun, M Chen. Influence of pretreatment and deposition parameters on the properties and cutting performance of NCD coated PCB micro drills. International Journal of Refractory and Hard Metals, 2014, 43: 30–41 https://doi.org/10.1016/j.ijrmhm.2013.10.016
16
Y Zhou, W Fang, L Y Shao, Y F Dai, J H Wang, X Wang, J L Yuan, W G Guo, B H Lyu. Edge preparation methods for cutting tools: a review. Frontiers of Mechanical Engineering, 2023, 18(4): 50 https://doi.org/10.1007/s11465-023-0766-y
17
B Boswell, M N Islam, I J Davies. A review of micro-mechanical cutting. The International Journal of Advanced Manufacturing Technology, 2018, 94(1–4): 789–806 https://doi.org/10.1007/s00170-017-0912-y
18
E Uhlmann, D Oberschmidt, A Löwenstein, Y Kuche. Influence of cutting-edge preparation on the performance of micro milling tools. Procedia CIRP, 2016, 46: 214–217 https://doi.org/10.1016/j.procir.2016.03.204
19
E Uhlmann, D Oberschmidt, Y Kuche, A Löwenstein, I Winker. Effects of different cutting edge preparation methods on micro milling performance. Procedia CIRP, 2016, 46: 352–355 https://doi.org/10.1016/j.procir.2016.04.004
20
J H Wang, B H Lyu, L Jiang, Q Shao, C B Deng, Y F Zhou, J H Wang, J L Yuan. Chemistry enhanced shear thickening polishing of Ti–6Al–4V. Precision Engineering, 2021, 72: 59–68 https://doi.org/10.1016/j.precisioneng.2021.04.002
21
L Wang, M X Wu, H Y Chen, W Hang, X Wang, Y X Han, H Chen, P Q Chen, T H Beri, L M Luo, B H Lyu. Damage evolution and plastic deformation mechanism of passivation layer during shear rheological polishing of polycrystalline tungsten. Journal of Materials Research and Technology, 2024, 28: 1584–1596 https://doi.org/10.1016/j.jmrt.2023.12.122
22
J H Wang, Y Zhou, Z Qiao, S Goel, J H Wang, X Wang, H Y Chen, J L Yuan, B H Lyu. Surface polishing and modification of Ti–6Al–4V alloy by shear thickening polishing. Surface and Coatings Technology, 2023, 468: 129771 https://doi.org/10.1016/j.surfcoat.2023.129771
23
B H Lyu, Q K He, S H Chen, Q Shao, Y Chen, Z Y Geng. Experimental study on shear thickening polishing of cemented carbide insert with complex shape. The International Journal of Advanced Manufacturing Technology, 2019, 103(1–4): 585–595 https://doi.org/10.1007/s00170-019-03600-w
24
B H Lyu, M F Ke, L Fu, S X Duan, Q Shao, Y F Zhou, J L Yuan. Experimental study on the brush tool-assisted shear-thickening polishing of cemented carbide insert. The International Journal of Advanced Manufacturing Technology, 2021, 115(7–8): 2491–2504 https://doi.org/10.1007/s00170-021-07176-2
25
J Span, P Koshy, F Klocke, S Müller, R Coelho. Dynamic jamming in dense suspensions: surface finishing and edge honing applications. CIRP Annals, 2017, 66(1): 321–324 https://doi.org/10.1016/j.cirp.2017.04.082
L Y Shao, Y Zhou, Y F Dai, B H Lyu. Experimental study on flexible fiber assisted shear thickening polishing for cutting-edge preparation of core drill. Lubricants, 2023, 11(2): 58 https://doi.org/10.3390/lubricants11020058
28
J H Wang, Z W Tang, S Goel, Y Zhou, Y F Dai, J H Wang, Q K He, J L Yuan, B H Lyu. Mechanism of material removal in tungsten carbide-cobalt alloy during chemistry enhanced shear thickening polishing. Journal of Materials Research and Technology, 2023, 25: 6865–6879 https://doi.org/10.1016/j.jmrt.2023.07.112
29
L Y Shao, M F Ke, J H Wang, B H Lyu, X Wang, J L Yuan. Experimental study on flexible fiber assisted stress rheological passivation and polishing of complex edge of cemented carbide insert. Diamond & Abrasive Engineering, 2022, 42(1): 1–9 (in Chinese)
30
C N Ramirez, R J Thornhill. Automated measurement of flank wear of circuit board drills. Journal of Electronic Packaging, 1992, 114(1): 93–96 https://doi.org/10.1115/1.2905448
31
H Y Shi, X W Liu, Y Lou. Materials and micro drilling of high frequency and high speed printed circuit board: a review. The International Journal of Advanced Manufacturing Technology, 2019, 100(1–4): 827–841 https://doi.org/10.1007/s00170-018-2711-5
32
S C Yang, W Ren, T J Wang, S Su. Parameter optimization of a micro-textured ball-end milling cutter with blunt round edge. The International Journal of Advanced Manufacturing Technology, 2020, 106(1–2): 577–588 https://doi.org/10.1007/s00170-019-04499-z
33
Y S Wang, B Zou, G G Yin. Wear mechanisms of Ti (C7N3)-based cermet micro-drill and machining quality during ultra-high speed micro-drilling multi-layered PCB consisting of copper foil and glass fiber reinforced plastics. Ceramics International, 2019, 45(18): 24578–24593 https://doi.org/10.1016/j.ceramint.2019.08.187
34
B Xu, X K Feng, X Y Wu, F Luo, L Y Fu, X T Zhai, Y H Zhao, H Zhao, J G Lei. Micro-EDM-assisted machining micro-holes in printed circuit board. The International Journal of Advanced Manufacturing Technology, 2021, 113(3–4): 1191–1201 https://doi.org/10.1007/s00170-021-06709-z
35
H Watanabe, H Tsuzaka, M Masuda. Microdrilling for printed circuit boards (PCBs)—influence of radial run-out of microdrills on hole quality. Precision Engineering, 2008, 32(4): 329–335 https://doi.org/10.1016/j.precisioneng.2008.02.004
36
T Atkins. The Science and Engineering of Cutting: the Mechanics and Processes of Separating, Scratching and Puncturing Biomaterials, Metals and Non-Metals. Oxford: Butterworth-Heinemann, 2009.
