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· Crystal oscillator cutting process
It is to cut at a certain angle to the crystal coordinate axis. There are many types of cutting. Because quartz is anisotropic, different cutting types have different physical properties.
The angle between the direction of the cut surface and the main axis has a very important influence on its performance, such as frequency stability, Q value, temperature performance, etc.
· The more common cutting types of crystal oscillators are briefly introduced in three types: AT, BT, and SC cutting.
AT cutting: It is a common quartz crystal cutting method. Its chip frequency-temperature characteristics are equivalent to cubic equations. It has the characteristics of high frequency, wide frequency range, high piezoelectric activity, good frequency-temperature characteristics in a wide temperature range (-40℃~85℃) and easy batch processing. It is mainly used to manufacture quartz oscillators.
BT cutting: It is mainly used to manufacture high-frequency oscillators and filters. It is suitable for applications that require high temperature stability, such as industrial control equipment and avionics equipment.
For crystal oscillators of the same frequency, AT cutting has a smaller temperature coefficient than BT cutting, and the slice thickness is thinner, but the Q value is lower than BT cutting.
SC cut: It has advantages that other cut crystals cannot match in terms of power-on characteristics, short stability, long-term aging, and radiation resistance. High-precision S-cut crystal resonators have high technical content and have high requirements for design, manufacturing process, manufacturing experience, etc. They are mainly used in high-precision and high-stability applications, such as precision timers, reference oscillators in communication equipment, navigation systems, etc.
Summary:
AT cut: It is suitable for high-frequency applications in a wide temperature range, with low cost and easy mass production.
BT cut: It is suitable for high-frequency applications that require high-temperature stability and has a high Q value.
SC cut: It is suitable for high-end applications that require extremely high frequency stability and precision, but has a high cost.
· The relationship between crystal frequency and slice thickness and cutting type:
The frequency calculation formulas for the two cutting methods can be simply calculated, namely AT cut and BT cut.
k represents different cutting method coefficients (1670 for AT cut and 2560 for BT cut), t represents thickness (unit: meter), and f represents frequency (unit: Hertz). The formula is as follows:
For AT cut, k=1670; for BT cut, k=2560. In this way, you only need to know the thickness of the cutting method to directly calculate the frequency.
The calculation formula for SC cutting is different from that for AT cutting and BT cutting, and the specific value depends on the specific manufacturer and application. Assuming that the coefficient of SC cutting is KSC (where ksc needs to be determined according to the specific application and manufacturer data), the formula is:
The YXC crystal oscillator manual also gives the cutting type of the crystal oscillator. The following example is YSX321SL, and the cutting method is AT cutting.
