The development of LED’s is expected to continue over the coming decades to the point where they become one of the predominant light sources. The pace of development however, differs depending on specific requirements and constraints. Currently one of the most promising markets is display backlight technology. Experts forecast a four-fold increase in the number of LCD displays with LED backlighting in 2010, superseding that of conventional cold cathode fluorescent lamps (CCFL). Laser marking is an essential step in manufacturing the LEDs used for this purpose.
Reliable High-speed Marking with Real-Time Compensation of Position Tolerances
There are currently two main methods of using LED backlighting in LCD flat panel televisions: LED edge-lighting and full array LED backlighting. The latter places about one hundred backlight segments behind the entire screen allowing for local dimming and providing a significant increase in the contrast range available. Each segment consists of hundreds of minuscule LEDs. As each LCD display requires a huge number of LEDs, their production has to be extremely cost-efficient, which also means fast.
Rofin is one of the few suppliers who can reliably meet these criteria, clearly demonstrated following extensive application tests using the PowerLine E-12 SHG IC laser source (532nm wavelength) configured with twin marking heads.
The laser marking process for this application is extremely demanding requiring a 0.080mm character height, 0.035mm line widths, exact positioning and marking speeds of more than 1000 characters per second. Engraving is performed within a tiny area and often on white plastic housings. Rofin‘s strengths include real-time compensation of position tolerances, which is an indispensible part of a reliable production process. Moreover, the PowerLine E series lasers offer cost-efficient operation and ease of integration.
Traceability Marking of High-Power LEDs
Mass market production of LEDs for LCD backlighting typically requires simple marking of type codes and connection labels. But there is now also a growing market for high-power LEDs which require full product traceability, such as those used in the automotive and mobile phone industries. Interior lights within modern cars already make full use of LEDs. Growth in the use of LED’s for rear lights, brake-lights and headlights will follow in the next few years according to expert opinion. Mobile devices rely on LEDs for display and keyboard backlighting, flashlights and more.
High-power LED production usually requires traceability markings on GaN, sapphire, SiC or GaAs wafers with OCR or T7 data matrix codes. Rofin’s Waferlase systems are designed to meet the most stringent requirements for wafer marking, assuring traceability of the manufacturing process for fault analysis of semiconductor devices. The systems all produce marks that are machine-readable, have no negative influence on subsequent manufacturing operations and still permit clear identification at the end of the process chain.
The PowerLine E-12 SHG IC laser is used to engrave tiny 2D matrix codes, made up of spots which are just 0.043mm diameter, on lead-frames during the LED production process Rofin‘s PowerLine E-30 SHG IC laser marks the white ceramics used as a substrate for LEDs, with characters just 0.15mm high and line widths of 0.020mm and ECC200 data matrix codes which have a 1mm edge length.
Market with Significant Growth Potential
LED backlighting technology will develop in several stages according to expert opinion. Local dimming currently debuts in high-end displays and is expected to enter more price-sensitive segments while RGB backlighting will find its way into the mass market. This will undoubtedly open up further interesting and challenging application fields for laser processing.