The international technology group SCHOTT showed what great influence glass can have on the future of mobile devices such as smartphones and tablets at an innovation event held in the “Chinese Silicon Valley” Shenzhen. Not only obvious components such as display screen protection glass are paving the way for the device designs of tomorrow, however – specialty glasses from SCHOTT are also positioned to revolutionize sensors, chips and antenna designs due to their physical compatibility with silicon.
Smartphone users share an average of over 2,500 daily touches with their mobile device1. This high number comes from fingertip swipes and app usage, making a relationship between users and the device’s display protection glasses. What is much less obvious: It is also glass that performs important tasks inside the mobile devices, for example in sensors and chips. The international technology group SCHOTT has now presented the topic of “glass in smartphones” in detail at an innovation event held in Shenzhen, China, and had a few surprises in its bag.
High-resolution digital cameras – only ready to deliver maximum performance with NIR cutoff filters
Modern high-end smartphones now allow digital photography with a resolution of ten or more megapixels. Most people are aware of the fact that not only the mere number of pixels is responsible for the quality of images. Besides the so-called CMOS sensors, the filters placed in front of it have a major impact on the true-color and realistic appearance of photographs. High-quality filters are made of glass, as are the protective glasses that protect the camera module from scratches.
The filter plays a vital role: it is an absorbing near-infrared cutoff filter (NIR cutoff filter). These filters show their strengths especially with difficult light and extreme photographic conditions. Absorbing NIR cutoff filter glasses from SCHOTT are a component in the camera module of high-tech and smartphone cameras and offer advantages over other materials. Interference filters, for example, filter near-infrared light much less reliably and are usually used for low resolution cameras. SCHOTT offers different glass products which serve the field of near-infrared cutoff filter application from low to high end. Regarding high end NIR cutoff filter glass, SCHOTT is now one of the major players due in no small part to the high quality and availability of its NIR cutoff filters. “Whenever someone shoots a high resolution photo with a high-end smartphone or a digital single-lens reflex camera, the picture was probably created with an infrared cutoff filter,” says Andreas Haedrich, Director of Sales for Europe at SCHOTT Advanced Optics. “In general, you can assume that all digital cameras that have a resolution of more than five megapixels use an absorbing NIR cutoff filter. The demand for our filter glasses has doubled over the past few months due to the current trend towards dual cameras in smartphones, a combination of a telephoto and a wide-angle lens,” he adds. “This positive development is motivating SCHOTT to pursue further developments. For instance, the technology group is currently working hard to make NIR cutoff filters even thinner to support the trend toward ever slimmer smartphone designs.
Ultra-thin glass – for curved designs and tomorrow’s sensors
SCHOTT has been advancing the development of its ultra-thin glass for many years. With industrially manufactured thicknesses of down to 30 micrometers, the ultra-thin glass penetrates into spheres that hardly anyone would associate with glass. Glass thinner than a human hair offers a wide range of application possibilities in electronics. Whether designed to be a display protection glass, a cover for fingerprint sensors or a cover for camera chips or lenses, thin glasses are predisposed for use in electronic components due to their special material properties. Yet even much more is possible. Thanks to its flexibility, ultra-thin glass already allows for the curved device designs of tomorrow.
SCHOTT AS 87 eco is a specialty glass that is perfectly suited for these types of applications. It was developed in international collaboration between SCHOTT sites in Germany and Asia, is produced in Germany in an environmentally friendly manner. The glass delivers an ultra-thin and ready to use thickness range, is extremely robust and flexible, and offers unique physical properties. For example, it has excellent transmission characteristics that are particularly important to fingerprint sensors. Furthermore, the unique production process eliminates the need of harmful acids for further slimming. The application fields are quite diverse. SCHOTT AS 87 eco could also be used as protective glass for curved displays, for instance.
The ultra-thin glass is drawn directly from the melt in the desired thickness using the so-called “down-draw process.” This is a technology for manufacturing thin-film lenses and SCHOTT is the only company in the world that has a command of it. This is also a pioneer for ultra-thin glasses for use even at the nanometer level of tomorrow’s chips and sensors.
Specialty glass with a penchant for silicon – for use in sensors and 5G antennas
Just like SCHOTT AS 87 eco, SCHOTT MEMpax is also pulled directly from the melt using the down-draw process. It allows the customer to work cost-effectively on fire-polished surfaces even at thicknesses of below 500 micrometers. The special feature of MEMpax is that the linear coefficient of thermal expansion of borosilicate glass with a fire-polished surface corresponds to that of silicon. Furthermore, this glass is ideally suited for anodic bonding. It can be joined with silicon, the chemical element that is the basis for ever-faster computer chips, processors and sensors in the semiconductor industry, by using a special process.
MEMpax is already used today in sensors in the automotive industry that measure tire and oil pressure. Here, the glass is joined to silicon by pressure, heating and tension and provides reliable measurement results as a part of a micromechanical system (also called “MEMS” or microelectromechanical systems).
Glass as a substrate for massive MIMO systems (5G) and radar applications
The extremely homogeneous material is not only suited for use as an ideal substitute for expensive polymers in sensors of the future, but also as a substrate for the integration of high-frequency applications. This bulky term means nothing more than to assemble as many circuit elements and antennas as possible in a very small space in an optimally developed component while enabling higher performance. This is particularly interesting for multiple input/multiple output radio systems, which are also referred to as “Massive MIMOs” and serve as the basis for the 5th generation telecommunications networks, the LTE successor “5G.”
In Massive MIMO concepts, dozens of antennas are combined inside a small space. By comparison: “only” a handful of transmit and receive antennas is responsible for transmission in LTE networks or the fast WiFi standard 802.11ac. The increased number of antennas is intended to not only increase transmission speed, but also guarantee stable connections to as many users as possible in defined spatial directions. This is particularly advantageous when many receivers meet in a small space, such as in soccer stadiums or dense city centers. This more targeted transmission also allows for the transmission power to be reduced.
“Whether a company is a manufacturer of radar-based distance measuring devices in the automotive sector or a reliable substrate on which a large number of mobile radio antennas are combined, ultra-thin special glasses from SCHOTT offer great freedom of design, high manufacturing precision and excellent high-frequency properties,” says Martin Letz, who works in Material Development at SCHOTT. “In addition, glass is significantly more metallizable than Teflon, for example, a standard material for high-frequency systems. And then glass also offers high tensile stiffness compared to plastics and good dielectric properties,” he concludes.