AT-Cut Single Crystal Quartz Wafers

University Wafer Silicon Wafers and Semicondcutor Substrates Services
University Silicon Wafer for Production

Get Your Quote FAST!


What is the Most Common Quartz Cut?

AT-Cut Quartz is the most common cut. First developed in 1934, AT-Cut quartz plate contains the crystal's x axis and is inclined by 35°15' from the z (optic) axis. The frequency-temperature curve is a sine-shaped curve with inflection point at around 25–35 °C. Has frequency constant 1.661 MHz mm.[48] Most (estimated over 90%) of all crystals are this variant. Used for oscillators operating in wider temperature range, for range of 0.5 to 200 MHz; also used in oven-controlled oscillators.[49] Sensitive to mechanical stresses, whether caused by external forces or by temperature gradients. Thickness-shear crystals typically operate in fundamental mode at 1–30 MHz, 3rd overtone at 30–90 MHz, and 5th overtone at 90–150 MHz;[50] according to other source they can be made for fundamental mode operation up to 300 MHz, though that mode is usually used only to 100 MHz[51] and according to yet another source the upper limit for fundamental frequency of the AT cut is limited to 40 MHz for small diameter blanks.[48] Can be manufactured either as a conventional round disk, or as a strip resonator; the latter allows much smaller size. The thickness of the quartz blank is about (1.661 mm)/(frequency in MHz), with the frequency somewhat shifted by further processing.[52] The third overtone is about 3 times the fundamental frequency; the overtones are higher than the equivalent multiple of the fundamental frequency by about 25 kHz per overtone. Crystals designed for operating in overtone modes have to be specially processed for plane parallelism and surface finish for the best performance at a given overtone frequency.[44]

 

 

What Applications Use AT-Cut Quartz?

Quartz crystals have established themselves as precise frequency generators, but how does a thin quartz disk determine the heartbeat of an application? Quartz crystals work by determining the angle between the quartz crystals, which determine their exact frequencies as generators.

It sounds simple, but it is very complex because not all quartz blanks are the same and every quartz blank is different. The ambient temperature changes slightly, so does the frequency of the desired frequency. This affects the stability of the frequencies produced by the quartz and can cause the temperature to change more, which in turn can lead to more change.

Quartz crystals also differ in their oscillations, but not as much as other types of quartz blanks, such as quartz crystals from other parts of the world.

They act like bow tendons, alternately tensed and relieved, and the longitudinal oscillator stretches its longitudinal axis as if stretched by a rubber band. Quartz crystals made of flexible U-tube quartz vibrate mainly in the middle of the blank.

The most common type of oscillation, however, is the thick shear oscillator, and at the same time the quartz disk changes its thickness. The figure shows the vibrations of a thick - scissor oscillator and a thin - hearing oscillator.

AT-Cut Vibration Type and Temperature Coefficient Defined

Cutting quartz crystals based on mathematical calculations and removing the quartz disk from the crystal is crucial. These changes can have a serious impact on the quality of the part and can be influenced during the production process.

One of the most common angle cuts is the at-cut, which is used in the production of Jauch crystals, which is cut at an angle of 90 degrees from the centre of a crystal.

Quartz blanks produced in this way have a good temperature coefficient, and the at-cut is one of the most frequently selected angle cuts for the production of Jauch crystals. This cut can be performed at temperatures of up to 1,000 degrees Celsius and is the second most popular and popular cut in the world in the field of angle cutting.

How to Make Quartz Vibrate

To make quartz vibrate, fine electrodes must be attached to the quartz, but quartz crystals are passive components and completely useless without external voltage. The big advantage of the further processing is that the quartz crystal produced during AT grinding is twice as thick as a sheroscillator.

However, the application of electrodes is a big challenge depending on the type of vibration and the thickness of the shear oscillator makes it much easier than with the above mentioned bending and longitudinal oscillators. Nevertheless, a further processing step in quartz is also necessary: electrodes should be attached to the quartz in such a way that they only deform minimally, even when voltage is applied.

The thin metal electrodes evaporate, attach the quartz holder to the tapered end and sand the blank before removing it.

Firstly, it ensures the shape of the blank and the thickness of its scissors and oscillator, and secondly, it determines the width and length of the AT and AT section. The AT cut thus fulfils the dual function of quartz production: Firstly, it ensures the smoothness and uniformity of all the scissors in the quartz and the stability and stability of each individual scissors.

Quartz Temperature Vs. Frequency

The FV performance is measured in parts per billion (ppb), and the SC cut will provide improved oscillator performance. Frequency and temperature stability is a specification that describes how the frequency output of an oscillator changes at each temperature.

Normally the incline of the SC section is bent, and the main reason for this is the steep curve (crystal bending point).

Compared to 27C. AT, SC will achieve greater stability in this range, and this improvement could be up to 5x over the extended temperature range. SCs can be cut at a bending temperature of 30 - 40C, which is much higher than for downhole applications. This is a great opportunity to improve the performance of the FAT, but not as much as the bending temperatures.

Quartz Crystal Aging

The ageing of a crystal is described in the specification described in the first part of this article "Aging of a crystal: a chemical analysis of crystal ageing."

Crystal aging is caused by impurities in the oscillator and is also measured with ppb. SC grinding is measured in ppB for the aging effect of the casting molding and the aging effect of the crystals when casting.

What is G-Sensitivity?

G - Sensitivity describes the sensitivity of the human body to changes in temperature, pressure, humidity and other environmental factors.

Quartz crystal is an electromechanical device that vibrates at a voltage potential and measures the sensitivity G with PPB - G. The noise is fed gradually into the oscillator and the electrical output characteristics change.