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Sapphire has become a versatile material that is useful in a wide variety of industries for a wide variety of applications including LED, optical, and RFIC. Sapphire tiles have a number of physical characteristics that make them suitable for a wide variety of end markets, including hardness and resistance to physical damage and chemical erosion. LEDs are the largest end market for sapphire related products such as sapphire wafers. In this market, the main end-uses are general lighting and LCD backlight. Other notable segments of the LED market are signage and automotive. However, the benefits of sapphire vary depending on the application. For example, lighting, industry, and automotive benefit from long life, which is relatively less critical for LEDs for mobile phones and notebooks where priority is high brightness and low power consumption. In this blog article, we will analyze the markets that use sapphire, including emerging and developing applications, key market trends, and the migration to large diameter sapphire wafers.
Sapphire is a typical variety of the mineral corundum and alumina precious stones. Due to its extraordinary hardness, they rate it at 9 on the Mohs scale, the third hardest mineral after diamond and moissanite. Sapphire wafers are especially attractive to those working in the laser industry due to their uniform dielectric constant and high-quality crystal structure. As a result, the use of sapphire substrates for blue laser diodes has increased, while sapphire has become the basis for modern RF switch applications.
The production process of sapphire wafers begins with the growth of single crystals. A core with a circular incision is drilled in a single crystal. The manufactured item is carefully checked for defects and stains. The core is then cut into thin wafers which are polished and prepared for the growth of the epitaxial layer. At the last stage, the product is packed for transport in special wooden containers. Production meets the ecological requirements of ecological production and employee safety. The production is ecologically clean, safe, and waste-free. Growth Technology is confidential and protected. In practical production, a sapphire waffle is made by cutting a crystal rod, followed by grinding and polishing. Generally, a semiconductor wafer is cut into wafer by wire cutting or multi-wire cutting machine. Since the cutting conditions always change during the cutting process, there are variations in the thickness and flatness of the cut sapphire. If the cutting conditions change, it will cause a deep layer of damage. Due to the small amount of material surface removal during wafer polishing, sanding is necessary to improve the flatness, curvature, and deviation of the plate before polishing and to reduce the thickness of the cut damage layer.
Orientation & Slicing
Accurately locate the position of the sapphire crystal rod on the slicer to facilitate precise cutting. Then, cut the sapphire rod into thin wafers.
Sanding & Chamfering
Remove the layer of chip cutting damage and improve the flatness of the wafer. Trim the plate edge to form a circular arc to improve the mechanical strength of the plate edge to avoid defects due to stress concentration
Polishing and cleaning
Improve the roughness of the wafer to achieve the precision of the sapphire wafer and remove contamination from the wafer surface.
The quality of the sapphire wafer should be checked with precision test equipment to meet customer requirements
On Sapphire Wafer Polishing
The goal of polishing the Sapphire tiles is to reduce the final thickness of the substrate to the required target value, with a TTV better than +/- 2 microns and improved surface roughness below 2 nm. This complete process can be achieved with precision systems, from bonding with the Wafer Substrate Bonding Unit to polishing with lapping and polishing systems. Each polished wafer will have an equal amount of material removed during the process and a consistently flat surface finish. By varying the pressure loads, an optimal material removal rate (MRR) of 1-2 microns per hour can be achieved.
General lighting is the largest future revenue market for LEDs, although still smaller than the overall backlight market which includes monitors, notebooks, and televisions. LED lighting often requires a larger matrix size, more power, and more brightness than other applications, bringing this market closer to state-of-the-art technology. The lighting market is characterized by a very fragmented customer base and regionally oriented markets. Here, new LED technology meets an older and more established industry. The lighting market is dominated by white GaN-based LEDs, other types such as red AlInGaP, covering only a small part of the market. Durability, reliability, brightness, and color quality are key factors.
Consumer electronics applications are characterrized by the use of white LEDs of medium brightness and matrix size. In some applications, blue and other LEDs can also be used. GaN-based LEDs are certainly dominant, especially in LCD backlighting, although other types of LEDs may be used in some consumer applications. For these LEDs, low cost is paramount, but certain product specifications also need to be met. Reliability over a long lifetime is less important in this area, especially for certain applications such as mobile phones which have a relatively short lifetime.
Signs and LED Displays
Signage including large LED displays is characterized by the use of multi-chip RGB LEDs for video walls. These products can be many square meters and cost hundreds of thousands or millions of dollars. Additionally, traffic signals and channel letters are illuminated by internal LEDs that might use sapphire wafers. The overall size of the matrices is considered to be medium in size, less bright than the illumination but brighter than the primary indication. Both AIInGaP and GaN / InGaN matrices are used. The main suppliers of LED packaging are Nichia and Cree.
The automotive market has a wide range of applications for sapphire wafers, including basic turn signals available for less than $ 0.01, so depending on the end-use, a wide range of quality is required. Most LEDs used in the automotive sector, especially outside the vehicle, must meet industry or government requirements and be of high quality and reliability, more important than low cost. Long service life is also important in this application. Outdoor lighting requires red, white, and yellow LEDs, and indoor lighting requires a wide range of colors, although a trend towards white LEDs has been observed in the last few years.
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