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The entry drilling process of flexible printed circuit board and its influence on hole quality

Lijuan Zheng (Guangdong University of Technology, Guangzhou, China AND University of Kentucky, Lexington, Kentucky, USA)
Chengyong Wang (Guangdong University of Technology, Guangzhou, Guangdong, China)
Xin Zhang (Guangdong University of Technology, Guangzhou , Guangdong, China)
Yuexian Song (Guangdong University of Technology, Guangzhou, Guangdong, China)
Lunqiang Zhang (Shenzhen Newccess Industrial Co., Ltd., Shenzhen, Guangdong, China)
Kefeng Wang (Guangdong Shengyi SCI Tech Co., Ltd., Dongguan, Guangdong, China)

Circuit World

ISSN: 0305-6120

Article publication date: 2 November 2015

241

Abstract

Purpose

The purpose of this study is to present the entry drilling process of flexible printed circuit board (FPCs) and its influence on hole quality, especially hole location accuracy. Compared with the traditional PCB drilling process, the technology of drilling FPCs is facing more problems, such as hole location accuracy, smear on the hole wall surface, burned hole wall surface, etc. Moreover, the materials of FPCs are quite different from the rigid printed circuit boards (RPCs). FPCs no longer contain glass fiber cloths to reinforce resin, resulting in flexibility. Micro-hole quality is the most important issue in FPC drilling. Suggestions were given to obtain higher hole qualities and higher FPC reliability.

Design/methodology/approach

The entry drilling process of FPC with different kind of entry boards was observed by a high-speed camera. The hole qualities of FPC micro-drilling, especially hole location accuracy and hole entrance quality, were measured. The relationship between entry boards and hole quality was analyzed.

Findings

Significant sliding occurred when drilling FPC with using no-entry board or pure aluminum plate entry board. On the contrary, no significant sliding occurred when using LC-110 or resin-coated aluminum foil (MVC) entry boards. The type, thickness and use-pattern of entry boards influenced hole location accuracy of FPCs seriously. In addition, entry board also influenced the micro-hole entrance quality and micro-hole diameter. The entrance quality of drilling FPC with LC-110 entry board was the best. The diameter variation of drilling FPC with MVC entry board was the smallest. The hole location accuracy decreased as the thickness of entry board increased. Thus, the best use-pattern of entry board was putting a LC-110 under MVC entry board, resulting in best entrance quality and hole location accuracy.

Originality/value

The technology and manufacturing of FPCs in China are obviously behind. Research of FPCs micro-drilling and research data are lacking so far. Thus, it is most necessary to improve the technology level of FPCs micro-drilling in China. Researches on hole quality, especially hole location accuracy of FPCs drilling, were performed in this paper. Suggestions were given to obtain higher hole quality of FPCs.

Keywords

Acknowledgements

This research was funded by the National Science Foundation for Young Scientists of China (Grant No. 51405090), the Special National Science Foundation for Post-doctoral Scientists of China (Grant No. 2013T60789), the National Science Foundation for Post-doctoral Scientists of China (Grant No. 2012 M521574) and a grant from the Key Program of the NSFC-Guangdong Joint Fund of China (Grant No. U0734007).

Citation

Zheng, L., Wang, C., Zhang, X., Song, Y., Zhang, L. and Wang, K. (2015), "The entry drilling process of flexible printed circuit board and its influence on hole quality", Circuit World, Vol. 41 No. 4, pp. 147-153. https://doi.org/10.1108/CW-11-2014-0054

Publisher

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Emerald Group Publishing Limited

Copyright © 2015, Emerald Group Publishing Limited

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