Cryogenic auxiliary drilling of printed circuit boards. Issue 4 (4th November 2019)

• Record Type: Journal Article
• Authors: Lin, Dantian; Wang, Chengyong; Fu, Lianyu; Ke, Yong; He, Yuxing; Fang, Gexian; Yao, Junxiong; Huang, Xin; Zheng, Lijuan
• Is Part Of: Circuit world. Volume 45:Issue 4(2019)
• Page Start: 279
• Page End: 286
• Publication Date: 2019-11-04
• Subjects: Tool wear -- FR-4 -- Chip morphology -- Chip removal -- Cryogenic drilling -- Hole wall roughness; Electronic circuits -- Design and construction -- Periodicals; Electronic circuits -- Periodicals; 621.381505
• DOI: 10.1108/CW-03-2019-0024
• Languages: English
• ISSNs: 0305-6120

Abstract

Abstract : Purpose: Large capacity current carrier printed circuit board (PCB) imposes strict control requirements on the hole wall roughness. The key factors are chip removal, drilling temperature and tool wear. This paper aims to find out a cryogenic drilling process to control the chip removal, chip morphology, tool wear and finally reduce the hole wall roughness. Design/methodology/approach: The chip removal process, chip morphology, tool wear and hole wall roughness of glass fiber epoxy resin copper clad laminate (FR-4) drilling were observed and analyzed. The influence of cold air on the chip removal process, chip morphology, tool wear and hole wall roughness was also investigated. An optimization process of cold air auxiliary drilling was proposed to control the hole wall roughness of FR-4. Findings: The results showed that the discharge time of copper foil chips with obvious characteristics can be used as the evaluation criterion for the smoothness of chip removal. The cold air can promote chip removal and reduce tool wear. In addition, the chip removal and cooling performance will be the best when using −4.7 °C cold air with the injection angle consisted with the angle of helical flute of the drill. The hole wall roughness of FR-4 could be controlled by drilling with −4.7°C cold air. Originality/value: This paper was the first study of the effect of three kinds of cold air on PCB drilling. This provided a reference for the possibility that the cryogenic drilling methods apply to PCB drilling. A new cold air auxiliary drilling process was developed for large capacity current carrier FR-4 manufacturing.