What are SAW Wafers and Crystals

A Surface Acoustic Wave (SAW) device is a device that transfers the input electrical signal into acoustic signal through the converse piezoelectric effects or vice versa, The acoustic wave propagates along the surface of the SAW substrates or wafer, and eventually the acoustic signal will be transferred into electrical signal at the other terminal of the substrates . SAW devices provide wide application possibilities across the fields of radio and television, mobile and wireless telephone, satellite communication, GPS system, identification system (e.g. electronic tag) etc.. Where SAW devices are used as filters, oscillators, correlators and delay line etc. Especially in the mobile communication industry, SAW devices are the essential components that determines the efficiency of information transmission. SAW devices continue to be of interest because of their superior functional characteristics in delay lines, filters, and other UHF, VHF and microwave devices.

SAW wafers or substrates are crucial parts of the SAW device to attain the energy conversion between mechanic wave and electrical signal. Because the velocity of SAW is extremely low, it is very conventional to sample signals and alternate them when the signals travel between the two terminals.

Since the discovery of piezoelectric effects in crystals such as quartz and tourmaline by French scientists Curie brother in 1880, research developed manifolds of new piezoelectric crystals in succession. Due to various factors, however, among those only a few types of materials could be actually industriously manufactured in bulk, majorly Quartz, Lithium Niobate (LiNbO3) and Lithium Tantalate (LiTaO3). Quartz possesses fine temperature stability, but its eletromechanical coupling coefficient is relatively low; LiNbO3 has great eletromechanical coupling coefficient but its negative temperature coefficient are also undesirably large; LiTaO3 has advantage over LiNbO3 in terms of temperature coefficient but its eletromechanical coupling coefficient does not even reach a quarter of LiNbO3’s.

Hangzhou Shalom EO has abundant experience in manufacturing surface acoustic wave substrates and is able to provide both off-the-shelf versions and custom versions of SAW wafers. LiNbO3, LiTaO3, Quartz and LGS SAW crystals ingots, wafer blanks, polished SAW wafers, up to 6 inches diameter are available:

SAW Grade LiNbO3 Wafers:

LiNbO3 Crystals Specifications:

Specifications for 3”/4”/5”/6” LN Wafers

SAW Grade LiTaO3 Wafers:

Lithium tantalate is a chemical substance with the chemical formula LiTaO3, sometimes briefly referred to as LT. It belongs to the trigonal system,with distorted perovskite structure and point group c63vr3c. The crystal system is uniaxial and optical properties measured on a single crystal are, therefore, anisotropic. The anisotropy of the refractive index in the visible region is mainly related to the anisotropy of the oxygen polarizability and is surprisingly small. These small anisotropies are related to the fact that the structure of LiTaO3 derives from the cubic perovskite structure. At the intermediate frequencies, the anisotropy of the structure induces very different lattice dynamical properties and band structure, so that the spectra of the index of refraction n and extinction coefficient k are very different for the polarizations parallel and perpendicular to the ferroelectric c axis. Reflection spectra in the optical range 2-35 eV is obtained.

Lithium tantalate crystals appears to be Colorless or shallow yellowish green. Lithium tantalate (LiTaO3) crystal is an excellent multifunctional material with high versatilities. Its general applications include Q-switch in laser technology, pyroelectric detector in infrared technology, filter and resonator in electronic industry.

Lithium tantalate is favorable for SAW uses. Polished LT wafer is widely used in the manufacture of resonators, filters, transducers and other electronic communication devices, especially for its good mechanical and electrical coupling, temperature coefficient and other comprehensive performance. It is used in the manufacture of high-frequency surface acoustic wave devices, and in many high-end communication fields such as mobile phones, walkie talkies, satellite communications, aerospace and so on.

Besides its applications in the SAW field,LiTaO3 crystal is the optimized choice for pyroelectric infrared detector because of its high chemical stability (insoluble in water), high Curie point above 600 ℃, low dielectric loss and high detection rate.Lithium tantalate  is  as well a kind of ferroelectric material with spontaneous polarization.

Hangzhou Shalom EO offers the SAW grade lithium Tantalate (or LiTaO3) crystals s and wafers, advanced facilities are equipped for crystals growing, wafer cutting, wafer lapping, wafer polishing and wafer checking, all finished products are passed at Testing of curie Temp and QC inspections. The SAW grade LiTaO3 crystals boules, blanks, wafer blanks and polished wafers are available upon customer’s request.

Specifications for 3”/4” LT Wafers

Quartz (SiO2) Crystals and Wafers

Quartz crystal,which has chemical composition of SiO2, belongs to the trigonal crystal system,space group P3121 or P3221 depending on the chirality. The ideal crystal shape is a six-sided prism terminating with six-sided pyramids at each end.Under natural circumstances, quartz crystals are often distorted, or so intergrown with adjacent crystals of quartz or other minerals, twinned (with twin right-handed and left-handed quartz crystals),  as to only form imperfectly the ideal prism shape ,or to lack obvious crystal faces altogether and appear massive.

Quartz single crystals has no pyroelectric effect and no ferroelectricity. Its melting point is 1750℃. The density is 2.65×103 kg/m3, and the Mohs hardness is 7. The main performance characteristics of quartz crystal are: good temperature performance of piezoelectric coefficient and dielectric coefficient, almost unchanged at room temperature; high mechanical strength and quality factor, high rigidity, good dynamic characteristics; no pyroelectricity, good insulation, Good repeatability. Its piezoelectric coefficient hardly changes with temperature in the normal temperature range. In the range of 20 to 200 ℃, the temperature increases by 1 ℃. The piezoelectric coefficient d11 is only reduced by 0.016%. 

Quartz crystals is the most representative and widely used piezoelectric crystal among single crystals. The applications of piezoelectric quartz include resonators, filters, and is widely used in navigation, remote control, telemetry, electronics, and electric equipment for automatic weapons, supersonic aircraft, missiles, nuclear weapons, electron microscopes, chronographs, electronic computers, artificial earth satellites, etc..

Hangzhou Shalom EO offers the SAW grade quartz materials and wafers, advanced facilities are equipped for crystals growing, wafer cutting, wafer lapping, wafer polishing and wafer checking, all finished products are passed at Testing of curie Temp and QC inspections. The quartz crystals boules, crystals blanks, wafer blanks and polished wafers are available upon customer’s request.

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