The automotive market presents one of the greatest opportunities for free-form displays, allowing panel and automotive designers to use much more than square corners and straight lines. In the past, the ability to only produce rectangular panels imposed significant creative limitations. Now, with new advanced manufacturing solutions available to detect, test and repair defects, designers can create displays for vehicles in any shape and with greater complexity and features.
With smarter and increasingly more autonomous vehicles becoming a reality over the next decade, the automotive market is forecasted to grow significantly. New vehicles will include more free-form displays in number and type, including interactive mirrors, heads-up displays, dashboards or instrument panels and in-vehicle entertainment displays. Every manufacturer and every model will have different designs, increasing the complexities for manufacturing.
The advent of free-form displays means automotive designers can include display geometries in any shape, including along its outer perimeter or throughout the display plane. As a result, features like cameras and sensors in the display plane that would have been impractical to manufacture previously are now possible. Displays can now be offered in more shapes and sizes to accommodate the increasing need for electronics within vehicles, now and in the future.
Trends in Display Design
Trends in automotive display design include larger sizes, free-form and multi-curve designs, high brightness, fast response time, increased viewing angles, and reduced power consumption. LCD displays limit the adoption of these automotive display trends and we can see that many panel makers are moving toward new display technologies like OLED and microLED.
The application areas within smart and autonomous vehicles include center stack displays, instrument clusters, driver information displays and camera information displays (pictured below). The designs for these new and increasing applications will require many or all of the following attributes:
- Free-form display shapes in a growing number of positions within a vehicle
- Ultra-slim bezels to maximize the usable area of each display
- High durability and reliability due to extreme temperatures and safety-critical needs
- Display high macro quality for uniformity and minimizing shading defects
- Emerging display technologies like OLED and microLED that provide better image quality and are highly luminous
Automotive designers can be assured there are new and forthcoming technology solutions that will enable manufacturers to produce high-quality displays with these increasingly important attributes.
Clockwise starting from top left: Center stack display, instrument cluster, heads-up display, driver information display, camera information display, rear seat entertainment
Free-form shapes and ultra-slim bezels
The quality and reliability of the safety-critical displays used in automotive applications are often impacted by defects formed during production processes. The free-form shapes and/or slim bezels can exacerbate this problem. Two process control technologies that enable quality control to preserve the defect-free requirements in automotive and enable free-form shapes and ultra-slim bezels are automated optical inspection (AOI) and electrical testing.
AOI solutions can use smart algorithms that provide defect detection and classification on constantly varying design geometries (area, shape, form or pattern) of the main display and peripheral areas. Traditional rectangular designs have simple and repeated patterns of thin film transistor-backplane (TFT-backplane), while free-form and ultra-slim bezel designs have complex and non-repeated TFT-backplane patterns. Some inspection solutions also include dedicated detection algorithms for holes inside the active area of a design. Time to production can be reduced significantly by using panel design data so manufacturers can achieve a mature setup from first glass – with full immunity to process variation and adaptive detection sensitivity, which has the potential to identify even the slightest process variation in multiple layers.
Electrical testing, another advanced manufacturing solution, detects electrical faults that affect the optical quality of free-form display by measuring the electrical field generated by the actual display pixels during the manufacturing process. This solution can test a wide variety of display shapes and sizes, such as those described, and can reduce operation setup, while increasing testing throughput.
High durability and reliability
Automotive displays require high durability and reliability to ensure safety. Undetected defects can cause critical display quality issues affecting the vehicle’s safety. A variety of manufacturing control solutions are required to ensure the quality level demanded in the automotive market: AOI, electrical testing, artificial intelligence (AI) and repair solutions such as photoresist repatterning.
Some AOI solutions provide superior inspection capabilities by using multiple illumination angles and wavelengths in a single scan. The images include bright field (reflective), dark field (angular) and backlight (transmitted) views. Backlight illumination provides very high contrast for the metal layers, creating a high level of sensitivity for open and short defects. It also enables detection of “backside” defects. Dark field illumination is a unique inspection technique that highlights edges, height differences and particles, and can be operated from multiple directions. It increases the system’s sensitivity to various types of small defects, such as missing or excess material in the pattern.
Ultra-high-resolution detection available in some optical inspection solutions can detect sub-micron defects. These fine defects range from nuisancects. Over time, if not discovered, these faults can become killer defects in the electronic circuitry. The defects are exacerbated by heat and cold, as well as by pressure and the shrinking and expansion of materials that occurs naturally in extreme conditions.
Revealing stresses through electrical testing can predict potential killer defects. For example, a “near open” may become an open defect during a stress test in which the line defect is detected at a very early stage of production. Taking this a step further, AI can be applied for classifying all point defects to reduce false alarms and killer point defect leakage and, ultimately, increase yield. AI can ensure a very high rate of killer defect capture, while providing the early alerts required to improve the manufacturing process and reduce scrap. With Industry 4.0 compliance also becoming a requirement in the automotive manufacturing market, AI can support the traceability required. AI can verify the history and location of any defects with documented identification.
Repair of defects is possible through a solution called photoresist repatterning, which ensures high display quality. It can repair photoresist shorts safely without causing any damage to the display.
Macro display quality
In the case of macro display quality, it is critical to detect both macro – shadow, contrast and/or color/gray-scale changes – and micro defects. AOI solutions can detect both types of faults in the displays resulting from problems in the production process. By using multiple illumination angles and wavelengths in a single scan, optical inspection solutions can identify and classify different types of macro defects.
Electrical testing and AI are also useful for macro display quality to provide Mura yield control, early alarms for process events that may cause defects, and the automation of the Mura control process.
OLED and microLED technologies
As the automotive industry moves toward using flex OLED and microLED displays, AOI solutions will become critical for the optimal detection and testing of the complex patterns required for touch displays. With flex OLED, manufacturers should consider AOI touch solutions that enable detection in long and complex pattern periodicity. In addition, solutions should be able to apply special image processing algorithms handling the complex and long pattern periodicity.
Though microLED will likely be used first for watches, it will eventually be used in larger displays such as those for automotive applications. MicroLED, which is still in the R&D phase, will require precisely matched points numbering in the millions for each display. Inspection, metrology, testing and repair solutions will need to detect LED shift, placement and rotation, missing and abnormal tilt of LEDs and color quality.
New standards
Given the high-level requirements for automotive displays, the industry needs new standards that ensure reliability and safety for new and emerging display designs. The standards should be comprehensive and achieved by yield-enhancing solutions for any display, any touch panel and any pattern design. The prediction and repair of defects that may become critical over time should be included, along with zero defect leakage. This would enable the detection and classification of active and peripheral areas and include both micro and macro defects.
Industry 4.0 compliance is also important, using AI-driven technology for enhanced detection, classification and automation of inspection and testing. This compliance standard also enables traceability by providing a saved history (more than one year) of detected defects and the process step for each display panel. Lastly, the standards should enable a faster time to production – a benefit to all in the manufacturing process – by achieving mature setup from first glass.
Gal Shaham is Senior Director of Marketing, Display Division, and Nilly Peltz is Senior Strategic Marketing Manager, Display Division, at Orbotech, Ltd.