Are there Different Grades of Synthetic Quartz Crystals?
Just like there are grades for diamonds and other gemstones, there are quality standards and grades for synthetic quartz crystals.
Standards are defined in International Standards (IEC 60758) and Japanese Industrial Standards (JIS C 6704).
As NDK, we are pushing forward with the development of high purity products in order to expand new horizons for quartz crystal products.
The three most important quality items for synthetic quartz crystals are as follows.
Infrared Absorption (α3585)
The quantification of infrared absorption is called the infrared absorption (α3585) value, and the smaller the α value, the higher the Q value and quality.
Inclusions refer to inclusions in crystals, and the fewer they are, the higher the quality.
[ Inclusion Density (Pieces) Per 1m3 ]
Etch Channel Density
Tubular pores along the line defects in the crystals are called etch channels, and the lower the density, the higher the quality.
[ Density of Occurrence Per 1 cm2 on the AT-cut Surface ]
High Purity Synthetic Quartz Crystal "N-Grade" Series
N-Grade is a brand of high purity synthetic quartz crystals grown by NDK, a leading synthetic quartz crystal manufacturer.
The impurity concentration, linear defect density, and inclusion density in the crystals, which can impede performance, are kept to an extremely low level.
The N-Grade, the highest grade with high purity, and N-Grade-EX, which exceeds the N-Grade in ultimate purity, are stably supplied with high yields.
N-Grade EX (Utra High Purity Synthetic Quartz Crystal)
"Improved Durability of Optical Devices"
High purity materials are used to produce the highest grade synthetic quartz crystal in all quality standards.
High durability to support high power lasers and radiation.
Ultimate Low Loss
Grade "Aa" with infrared absorption (α3585). This is an ultralow loss that is an additional 40% lower than Grade A. Optical devices have excellent durability due to extremely low energy loss.
Ultimate High Purity with No Impurities
Inclusion density is grade "1a." Of course, this is the highest grade. This is a strict specification of no more than one inclusion particle of only 30-70 μm in 1 cm3, and it has been met with a comfortable margin. In addition, the concentration of impurities in N-Grade EX is significantly reduced compared to ordinary synthetic quartz crystals for optical components (Figure 1).
[Figure 1. Comparison of Impurities Contained in Synthetic Quartz Crystals for Optical Components and N-Grade EX]
Ultimate High Quality with No Defects Allowed in the Crystals
The etch channel density grade, which affects performance and stability, is "1a." Strict specifications are set for 1a, with no more than five pieces.
[Example of an Etch Channel Occurring on an AT-cut Surface]
They are used as optical devices for exposure/steppers in semiconductor manufacturing machines and high power lasers by taking advantage of their high durability performance.
N-Grade (High Purity Synthetic Quartz Crystal)
"Improved Quartz Crystal Device Performance"
High purity grade synthetic quartz crystal that boasts top class purity.
The infrared absorption (α3585) is small and stable frequency temperature characteristics can be obtained.
While EX is utilized as an optical device due to its high durability performance, this is used as a timing device in fields that require extreme system stability and high performance, such as 5G base stations, due to its outstanding electrical characteristics.
Product Lineup of NDK's Synthetic Quartz Crystals
At NDK, we produce high quality synthetic quartz crystals suitable for a variety of applications in addition to the N-Grade series.
Synthetic Quartz Crystal