LED-Based Display Processing

Figure 1: Multi-scanner system utilizing the IFOV A3200 controller feature to easily
perform complex, large-scale, high-dynamic laser processing between multiple axes.

Technology Overview

Light-Emitting Diode (LED) display technology is set to replace the ubiquitous liquid crystal display (LCD) that is incorporated into phones, computers, and flat-screen televisions. LEDs have a number of advantages over LCDs. From a user’s perspective, LED displays have a significantly higher contrast ratio, pixel resolution, brightness, refresh rates, color range, and increased viewing angle. Additionally, LEDs are more power efficient than LCDs and consist of a simpler, more durable design that allows them to operate in a broader range of environments. Most interesting about LEDs is the ability to produce them in very thin form factors, and their “light emitting” characteristics. Because they are “light emitting” they do not require a backlight like LCD technology and can be embedded in super thin, flexible, and even transparent sheets that have the potential to turn almost any surface into a display.

LED displays are manufactured in panels consisting of a number of complex layers. Much like the integrated circuit industry, most of the early manufacturing consists of vapor deposition and chemical coating processes where the panel is moved from one subsystem step to the next via robots and conveyors. Once the panel layers are fully assembled, the difficult process of cutting-out the individual component displays must occur. This process occurs via galvanometer laser scanner with the assistance of servo stages, as seen in Figure 1. The complex assembly of polymer and organic layers in the display makes the output quality of cut parts very sensitive to laser parameters and general process control. At the same time, there is a desire for high rates of throughput as there are extreme pressures on manufacturing capacity in this industry. LED technology is set to completely overtake LCD technology in the mobile phone and TV markets over the coming years.

The manufacturing of small flexible LED displays is a difficult endeavor. The material/laser interaction required to make high quality cuts through the various layers of a display is sensitive to many factors. Also, the complex motion paths and tracking error requirements are more demanding than in previous display manufacturing processes. On top of this is the stress of large demands, tight timelines, and the challenges of unforeseen problems that go along with new technologies and production processes.

Aerotech’s AGV-HP is a new generation of galvo laser scanner that uses precision principles and complete motion system integration concepts. The AGV is extremely fast, is the most accurate scanner on the market, and is stable enough to maintain accuracy all day in a 24/7 production environment. At the same time it has the most advanced laser control features and works seamlessly with other motion axes, eliminating many design constraints and making any system it’s used in more versatile.


The Challenge: Irregular Display Form Factors

LED display technology enables production of irregular display form factors and shapes. With LEDs mobile phone displays now include curved surfaces and are aimed at being made “bendable.” This, in addition to larger screens, the continued popularity of tablets, and the growing use of LED displays in other markets like the automotive industry, make producing them within a single field-of-view of a galvo very difficult. The cutting of the layered material requires small spot sizes, which in turn makes the FOV less than the size of the complete display component. This makes processing the complete display component with high-throughput nearly impossible.

The Aerotech Solution: Infinite Field of View (IFOV)

Aerotech’s Infinite Field of View (IFOV) can be used to eliminate the connection between field size and spot size. With IFOV a machine designer can pick the lens they need to achieve the desired spot size and ensure high quality cuts of the complex material. The processing area is extended as large as desired by adding stages to carry the scanner for use with IFOV in combined scanner and servo stage motion. This also allows the user to make large component displays as well as small mobile displays on the same machine. By seamlessly combining galvo and servo motion, a system with IFOV is capable of cutting very large, irregular, and complex shapes all with high throughput & quality. See our brochure Infinite Field of View for more details.

The Challenge: Tightly Controlling Both Laser Energy/Power and Motion

Cutting the various layers within the LED display material is very sensitive to laser parameter control. In order to get a high-quality cut and high yield, the amount of energy and power sent to the part by the laser must be finely controlled in conjunction with the motion. This can be difficult with traditional galvo/servo combined systems as they operate independently. Failure to synchronously control the laser with the motion will cause poor parts, less yield, and a sub-optimum process.

The Aerotech Solution: Position Synchronized Output (PSO) & Analog Vector Tracking

Position Synchronized Output (PSO) gives the motion programmer the ability to trigger laser energy as a function of the real-time tool position, rather than through fixed temporal frequencies. This allows the user to select the desired energy density across the cut path and maintain that setting through modulating delivered energy in the spatial domain. Now the motion equipment can ensure quality cuts even through the changes in velocity and acceleration required to maintain the high level of tracking accuracy required during complex cuts. Additionally, the Analog Vector Tracking feature allows the user to modulate pulse energy or laser power as a function of the true tool-on-part velocity, even in combined IFOV-based motion systems – slow in sharp corners to maintain dynamic accuracy without the concern of pulses bunching up and giving poor cutting quality in those areas. See Position Synchronized Output (PSO) – Coordinate Part Position with Process Control for more details.

The Challenge: f-Theta Lens Distortion

Again, the cutting of the various layers within the LED display material is very sensitive to laser parameter control. In order to get a high-quality cut and high yield of the final component, the amount of energy and power sent to the part by the laser must be finely controlled at the same time as the motion is controlled. The distortion due to the f-theta lens as the laser spot moves is enough to negatively affect part quality. However, limiting the scanner’s FOV to avoid the areas of high distortion causes losses in throughput.

The Aerotech Solution: Power Correction Mapping

Power Correction Mapping is an integrated controller function that gives the user the ability to scale power output of the laser via an analog output as a function of position within the scanner’s field of view. The effects of spot size distortion by the f-theta lens can be largely nullified by changing the power output of the laser to account for diameter changes in the laser spot. Using this power correction map will result in very even energy densities distributed to the substrate, regardless of where you are in the galvo’s field of view. The result will be increased yield and overall increased system efficiency.

The Challenge: A Rapidly Changing Market

As the LED display market grows and changes, different production techniques will be required to support the different markets in which the displays are used. Manufacturers want to make sure that they’re investing in a product and company that can stand up to the inevitable next unknown challenge.

The Aerotech Solution: Flexible Control and a Thermally Stable, High-Precision Galvo

The AGV galvo and A3200 machine controller offer the best available combination of both open data architecture and dynamic ability to perform precision moves. The A3200 gives the user the ability to monitor and capture hundreds of different data items from the system, including the scanner’s actual position in coordination with laser firing and other activity. Aerotech’s state-of-the-art controller and trajectory generator make the AGV the most accurate and dynamically capable galvo on the market today.

An accurate and stable galvo is required as features on displays get smaller and more complex. The AGV is the most thermally stable galvo on the market with <10 µrad/°C drift, and is capable of achieving single-digit micron accuracies over the full field-of-view. Most importantly, it comes with the data to back-up those claims. It also is available with water cooling to ensure stability while in variable environments, and is a proven technology in hundreds of successful systems around the world.

The Challenge: Technical and Time Constraints

The display market is changing extremely fast and deadlines to ship displays are pressing. Choosing a motion component supplier that is agile and knows the manufacturing processes is key. Technical challenges and obstacles are sure to come up as production continues to ramp up. Falling behind on a production schedule due to an unforeseen technical complication that your motion partner couldn’t help you solve would hurt future revenue.

The Aerotech Solution: A History of Success

Aerotech’s world-class support is key to production challenges like these. Aerotech has offices in all parts of the globe, and service issues can be handled in the user’s time-zone. Also, Aerotech offers advanced motion programming support through our Application Engineering & Applied Technologies Groups in order to get the LED production processes up and running successfully as fast as possible. Aerotech is a world leader in motion control and precision equipment design. Its staff has the experience and the skills to be leveraged to overcome any challenge, seen or unseen. Selecting Aerotech as a supplier helps mitigate production start-up risk and minimizes time to production.