Studies were conducted to determine the strength and thermal stability of samples of glass with edges obtained by cutting a moving ribbon of float glass by mechanical and laser cutting. The advantage of laser cutting was demonstrated.Brittleness is a problem in using sheet glass. The weakest part of the glass sheet is the edges due to the large number of gross stress concentrators that remain in the edges after cutting the moving ribbon and keeping the degree of its hazardousness unchanged over the entire time of shipment, storage, and use of the glass [1].Mechanical cutting (as the simplest and most accessible) is used in continuous production of sheet glass; it consists of making a median crack with a hard-alloy roller. In order to obtain a quality edge, i.e., a defect-free edge and smooth, shiny end with perpendicular surfaces, the optimum cutting parameters must be rigorously observed. Otherwise, the edge will have a coarse shape with a large number of chips and pits. The transverse bending strength and thermal stability are quantitative criteria for evaluating the quality of the glass edge.Mechanical cutting reduces the strength of the glass by 60% on average. The strength of such glass can be increased by treating the edges. The most common method is mechanical (grinding followed by polishing). However, the strength of the glass increases by approximately 30% [2].A laser cutting unit (Fig. 1) for separating the edges from the moving glass ribbon has now been introduced in the ÉPKS-4000 float line (Saratov Glass Institute Co.). The method of controlled thermal cleavage is used in the unit, and it essentially consists of projecting the beam of a molecular gas CO 2 laser, which provides for local heating (to 350 -450°C) of the cutting line, and feeding an air-water mixture under pressure on the surface of the glass. As a result of the temperature gradient that arises at a small depth from the surface of the glass, a microtrack is formed and causes separation.The edge is separated after the glass ribbon is transversely cut into sheets of the required length with edge cutters. The ends of samples obtained after laser and mechanical cutting of a float-glass ribbon are shown in Fig. 2.The qualitative evaluation with a MIN-8 (´50) microscope showed that both ends are smooth and shiny. However, although a defect-free edge is obtained after laser cutting,

No abstract

PACS 65.40.-b, 78.20.-e The glass precise cutting by CO 2 laser appeared to be effective for sapphire wafer die separation. A standard sapphire wafer can be processed in 2 min, neither thinning, no final cleaving are needed. A commercial equipment LED chip cutting demonstrated no degradation after 5000 h of the LED test. IntroductionThe traditional mechanical die separation is not well suited to sapphire substrate devices, mainly using c-oriented sapphire surfaces. Meanwhile the cutting process, described in this manuscript, for other sapphire surface orientations is effective as well. The laser ablation for cutting was successfully demonstrated by Emcore, K-Jet International Inc. and J. P. Sercel Associates Inc. companies [1]. They use a high power UV laser for sputtering grooves into the sapphire substrates, followed by conventional scribe and break methods. Compared with the mechanically scribing with a diamond tool the UV method increases die yields and wafer throughput and reduces the equipment operation and maintenance costs. Meanwhile the cost and the lifetime for the UV laser are still subject for further development. Moreover, the technique described in this paper allows to get rid of the fracturing machine cleaving and even the wafer thinning if needed. The quality of the cutting edge appeared to be effective mirrors for laser dies. We used for GaN-based LED wafers the Laser Controlled Thermocracking Die Separation Technique with the laser wavelength 10.2 µm. The Laser Controlled Thermocracking Technique (LCTCT) [2] is widely used for the precise cutting for flat panel display production, including liquid crystal displays and plasma display panels [3].

No abstract