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Title: Multi-foci laser separation of sapphire wafers with partial thickness scanning
Authors: Lye, Celescia Siew Mun
Wang, Zhongke
Lam, Yee Cheong
Keywords: Engineering::Mechanical engineering
Issue Date: 2022
Source: Lye, C. S. M., Wang, Z. & Lam, Y. C. (2022). Multi-foci laser separation of sapphire wafers with partial thickness scanning. Micromachines, 13(4), 506-.
Project: U12-M-007JL 
Journal: Micromachines 
Abstract: With multi-foci laser cutting technology for sapphire wafer separation, the entire cross-section is generally scanned with single or multiple passes. This investigation proposes a new separation technique through partial thickness scanning. The energy effectivity and efficiency of the picosecond laser were enhanced through a two-zone partial thickness scanning by exploiting the internal reflection at the rough exit surface. Each zone spanned only one-third thickness of the cross-section, and only two out of three zones were scanned consecutively. A laser beam of 0.57 W and 50 kHz pulse repetition rate was split into 9 foci, each with a 2.20 μm calculated focused spot diameter. By only scanning the top two-thirds sample thickness, first its middle section then upper section, a cleavable sample could result. This was achieved with the lowest energy deposition at the fastest scanning speed of 10 mm/s investigated. Although with partial thickness scanning only, counter intuitively, the cleaved sample had a previously unattained uniform roughened sidewall profile over the entire thickness. This is a desirable outcome in LED manufacturing. As such, this proposed scheme could attain a cleavable sample with the desired uniformly roughened sidewall profile with less energy usage and faster scanning speed.
ISSN: 2072-666X
DOI: 10.3390/mi13040506
Schools: School of Mechanical and Aerospace Engineering 
Organisations: Singapore Institute of Manufacturing Technology (SIMTech), A*STAR
Genuine Solutions Pte Ltd.
Research Centres: SIMTech-NTU Joint Laboratory (Precision Machining)
Rights: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (
Fulltext Permission: open
Fulltext Availability: With Fulltext
Appears in Collections:MAE Journal Articles
SIMTech Journal Articles

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