| Diameter |
2" |
3" |
4" |
5" |
6" |
| Orientation |
X-Cut, Y-Cut, Z-Cut, ST-Cut, AT-Cut or others |
| Thickness (um) |
280 |
380 |
500 |
625 |
675 |
| Material |
Crystal Quartz |
| Grade/Brand |
Optical, SAW |
| Surface Finished |
DSP/SSP |
| TTV (um) |
<8 |
<10 |
<10 |
<10 |
<15 |
| Bow/Warp (um) |
<30 |
<30 |
<40 |
<40 |
<60 |
| Top Side Ra (nm) |
<1 |
| S/D (um) |
40/20 |
I. Basic knowledge of quartz crystal
1. Chemical and physical properties
①the composition of the crystal is SiO2. At different temperatures under normal pressure, the structure of the quartz crystal is different. When the temperature is T < 573 ℃, αquartz crystal. When the temperature is 573 ℃< T < 870 ℃, βquartz crystal has a melting point of 1750 ℃. Generally speaking, the piezoelectric quartz crystal refers to αquartz crystal.
②with piezoelectric characteristics:
find
Piezoelectric effect:
Piezoelectric effect is the phenomenon that some media polarize inside due to external mechanical action (such as compression, stretching, etc.) and produce surface charge.
Reverse piezoelectric effect:
Some media placed in the external electric field, due to the role of the electric field, will cause the displacement of the positive and negative charge center inside the media, resulting in the deformation of the media, this effect is called the reverse piezoelectric effect.
When the quartz crystal acts on the force along the x-axis (or y-axis), the piezoelectric effect is produced in the x-direction, while the piezoelectric effect is not produced in the Y and z-directions. The x-axis is called the electric axis, and the y-axis is called the mechanical axis.
③it has anisotropy: quartz crystal is a good insulating material. Its thermal conductivity is near room temperature, which is about 2 times of that perpendicular to the z-axis along the z-axis. Its linear expansion coefficient A3 along the z-axis is about 1 / 2 of that A1 along the z-axis. Its dielectric coefficient ε, piezoelectric coefficient D and other values vary with the direction, at different temperatures, The values of thermal conductivity K and expansion coefficient a are also different.
④it is a single crystal with highly symmetrical shape, which is characterized by regular arrangement of atoms and molecules and well-developed quartz crystal. The most remarkable feature of the shape is regular configuration of crystal face. There are 30 crystal faces of quartz crystal, six m faces (cylinder), six R faces (large edge), six R faces (small edge), six s faces (triangular cone), six x faces (triangular plane), The angle between adjacent m-plane and R-plane is 60 °, the angle between adjacent m-plane and R-plane is 38 ° 13 ', and the angle between adjacent s-plane and X-Plane is 25 ° 57'.
There is a cubic symmetry axis C and three mutually formed axes a, B and D of 120 ° in quartz crystal. When discussing the physical properties of quartz crystal, it is more convenient to use the rectangular coordinate system shown in the figure below. Select the axis C as the axis Z, the axis a (or B, d) as the axis X, and the axis Y perpendicular to the axis X and Z. its direction is in accordance with the ire standard of 1949, and right-handed rectangular coordinate system is used for both left and right-handed rotating crystals.
As shown in the figure: A, B, C and D are crystal coordinate systems
X, Y, Z are rectangular coordinate systems
⑤birefringence:
However, when the light enters along the z-axis, there is no birefringence, so it is also called the z-axis.
⑥the density of quartz crystal ρ= 2.65g/cm2, the hardness is Mohs hardness 7, which is insoluble in three acids (HCl, H2SO4, HNO3) under normal temperature and pressure. It belongs to the substance with very small solubility, but hydrofluoric acid and ammonium hydrogen fluoride are good solution of quartz crystal, and their chemical reaction equation
SiO2+4HF=SiF4+2H2O （3SiF4+3H2O=H2SiO3+2H2SiF6）
SiO2+4HF+2NH4F=（NH4）2SiF6+2H2O
Its properties are used for the corrosion of quartz sheet.
3. Cutting of quartz wafer
The cutting of crystal axis by quartz wafer is called the cutting mode of quartz wafer. Due to the anisotropy of quartz crystal, the electrical and thermal properties of different cut quartz chips are different because of their elastic properties, piezoelectric properties and temperature properties.
The following figure shows the positions of various cutting patterns:
(1) the cut symbol indicates:
There are two ways to express the cut symbol of quartz crystal, one is the symbol representation stipulated by ire standard, the other is the customary symbol representation peculiar to quartz crystal. The cut symbols specified by ire are represented by a set of letters (xyzlwt) and angles, the thickness and length of the wafer along the original direction of the coordinate axis are represented by the sequence of three letters in XYZ, the direction of rotation is represented by T (thickness), l (length) and w (width), and the positive sign of the angle is represented by anticlockwise rotation and the negative sign is represented by clockwise rotation.
Example: (YXL) 35 ° original wafer angle: Y direction
Original wafer length: X direction
Rotate 35 ° anticlockwise around the length direction (x axis) to get the cutting direction of the wafer, (xytl) 5 ° / - 50 ° thickness t (x axis) 5 ° anticlockwise, and then rotate 50 ° clockwise around the length L (Y axis), which is the cutting direction of the quartz wafer.
The customary symbols of quartz crystal are mostly expressed in two English capital letters. For example, the customary symbols of (YXL) 35 ° cut type are expressed in at, and (xytl) 5 ° / - 50 ° are expressed in NT.
②common quartz crystal cutting type:
