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Stealth dicing of LED and ultrafast laser

(Summary description)

Stealth dicing of LED and ultrafast laser

(Summary description)


Light Emitting Diode (LED) is a solid-state cold light source, which uses semiconductor as lighting material. When a forward voltage is applied on electrodes, carriers in the semiconductor material compounds, releasing energy, emitting photons, and generating visible beams. LED lamp can be with lifetime of up to 10,000 hours, and are 10 times more efficiency than incandescent lamp and twice as fluorescent lamp. It also features with anti-vibration, good safety, durable, environment friendly etc. LED is the fourth generation of new energy light source after incandescent lamp, fluorescent lamp, high intensity high pressure sodium lamp and metal halide lamp. Its unique illumination method makes it a typical green light source, and has been widely used in backlight lighting, road traffic, transportation and display such applications.


With development of LED chip technology, expanding market shares and involving requirements, LED dicing technology is constantly improving. In early days, diamond scribing was mainly used for dicing of nonmetal substrate materials (mainly sapphire) in LED production process. Since sapphire material is too hard to process, it caused great consumption of diamond during processing, besides that a certain degree of physical deformation such as micro cracks exist and affect final performance of the LED device. A second generation of LED dicing technology is using diamond wheel with blade saws, which embeds tiny diamond micro-balls around nickel wheel with blades of certain size and thickness. During dicing process, the blade moves forward with high-speed rotation along the cutting path, so as to cutting LED wafer. Nowadays LED is increasingly with GaN-based sapphire substrate, also benefited by development and innovation of laser technology, a third generation of dicing method has emerged, namely laser scribing technology.



Wafer dicing


The current mainstream technology of laser scribing is by "hot processing". During the process laser beam is focused and guidance into the material, it releases large amounts of energy in a very short time, making material melted and gasified, at the same time by moving laser galvanometer, it forms a cutting mark as to realize the purpose of the wafer dicing. Though "hot processing" has great advantages in cutting speed and cutting quality, with more and more diversified LED applications, the market has more higher requirements for the LED device. Due to existence of cracks and molten slag on the cutting surface caused by “hot processing”, people turned eyes to "cold processing" technology based on ultrafast laser.


Principle of stealth dicing


In order to solve above problems of "hot processing" technology, researchers continue to carry out technical exploration. Laser stealth dicing technology were invented by Hamamatsu company in Japan and has greatly solved the shortages of “hot processing”. The laser stealth dicing technique works by using an ultrafast laser, the laser beam passed through surface of LED substrate, then was focused inside the device and cuts through the surface of the material. The beam is focused to a spot inside the material, and then scanned along a set cutting line. Compared with past laser scribing technology, laser stealth dicing technology is a full dry process without defects caused by the wet treatment process, it also saves processing time during production.




Equipment of stealth dicing


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