Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2021 Jun 12;12(6):688.
doi: 10.3390/mi12060688.

Elimination of Hole Mouth Burr in Multilayer PCB Micro-Hole by Using Micro-EDM

Xinke Feng  1 , Bin Xu  1 , Jianguo Lei  1 , Xiaoyu Wu  1 , Feng Luo  1 , Lianyu Fu  2
Affiliations

Elimination of Hole Mouth Burr in Multilayer PCB Micro-Hole by Using Micro-EDM

Xinke Feng et al. Micromachines (Basel). .

Abstract

The micro-hole is a key structure in multilayer printed circuit board (PCB), as it enables the effective transmission of electrical signals. At present, the most common way to machine PCB micro-holes is mechanical drilling using micro-bit. However, in the mechanical drilling of micro-holes, these holes are prone to burring at the hole mouth due to the micro-bit failing to cleanly cut through the first layer of copper foil on the PCB. Hole mouth burr can seriously affect the performance of the PCB, resulting in potential short circuiting or even ruining the PCB. To solve the above problems, this paper proposed to machine the first layer of copper foil on the PCB via micro electro-discharge machining (micro-EDM) to eliminate hole mouth burr. Compared with the mechanical drilling, micro-EDM is a form of non-contact machining, and the high temperature generated from the electric spark discharge can erode the first layer of copper foil, thus fully eliminating hole mouth burr. This paper performed a detailed study of the influence of spindle speed, machining voltage, pulse width, and pulse interval on hole mouth quality. After that, the technological parameters for eliminating hole mouth burr were obtained. Finally, under the effects of 20,000 rpm spindle speed, 26 V machining voltage, 4 μs pulse width, and 8 μs pulse interval, a micro-bit with a diameter of 200 μm was used to perform micro-EDM of the first layer of copper foil. From the machining results, it can be known that the PCB micro-hole was possessed of overall good quality, with good hole wall surface quality and almost no visible hole mouth burr.

Keywords: hole mouth burr; micro-EDM; micro-hole; multilayer PCB.

PubMed Disclaimer

Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Hole mouth burr in printed circuit board (PCB) micro-hole.
Figure 2
Figure 2
Specific technical process for machining PCB micro-hole by using micro electro-discharge machining (micro-EDM).
Figure 3
Figure 3
Experimental equipment: (a) experimental platform, (b) scanning electron microscope, (c) micrograph of PCB micro-hole.
Figure 4
Figure 4
Influence of spindle speed on the quality of micro-hole mouth.
Figure 5
Figure 5
Influence of spindle speed on the average length of the hole mouth burr.
Figure 6
Figure 6
Influence of machining voltage on the machining quality of micro-holes.
Figure 7
Figure 7
Influence of machining voltage on the average length of the hole mouth burr.
Figure 8
Figure 8
Influence of pulse width and duty cycle on the machining quality of micro-hole.
Figure 9
Figure 9
Influence of pulse width and pulse duty cycle on the average length of the hole mouth burrs.
Figure 10
Figure 10
Influence of duty cycle on the machining quality of the interior wall of the micro-hole: (a) duty cycle was 0.50, (b) duty cycle was 0.33, and (c) duty cycle was 0.25.
Figure 11
Figure 11
Micrographs of micro-holes machined by the two processes: (a) micro-hole machined by mechanical drilling; (b) micro-hole machined by micro-EDM.
See this image and copyright information in PMC

References

    1. Shi H.Y., Liu X.W., Lou Y. Materials and micro drilling of high frequency and high speed printed circuit board: A review. Int. J. Adv. Manuf. Technol. 2019;100:827–841. doi: 10.1007/s00170-018-2711-5. - DOI
    1. Huang L.X. Investigation of chip formation and burr control in PCB fixture hole. Circuit World. 2015;41:61–69. doi: 10.1108/CW-09-2014-0040. - DOI
    1. Li Z., Zheng L., Wang C., Huang X., Xie J. Investigation of burr formation and its influence in micro-drilling hole of flexible printed circuit board. Circuit World. 2020;46:221–228. doi: 10.1108/CW-05-2019-0049. - DOI
    1. Tang Z., Huang X., Wang C., Liao B., Lin D., Yao J., Zheng L. Micro-drilling characteristics of sequential glass fiber-reinforced resin-based/copper foil multi-layer sheets. Int. J. Adv. Manuf. Technol. 2020;107:399–410. doi: 10.1007/s00170-020-05038-x. - DOI
    1. Liu X., Shi H., Huang G., Tao S., Gao Z. Investigation on Drill Wear and Micro Hole Quality in High Speed Drilling of High Frequency Printed Circuit Board. IOP Conf. Ser. Mater. Sci. Eng. 2020;825:012034. doi: 10.1088/1757-899X/825/1/012034. - DOI

LinkOut - more resources