Glossary - alphabet order - "S"

SAW

Abbreviation for Surface Acoustic Wave (wave that is propagated across surfaces). A structure that alternates positive and negative electrodes is implemented on the surface of a piezo-electric element, so that a wave-like vibration is emitted from the surface. The oscillation frequency is inherent in interval between electrodes and the propagation speed of sound within the substrate. This type of crystal is able to produce higher frequencies (several hundred MHz) than a tuning fork crystal or AT cut crystal. Epson's SAW products line ups are SAW resonators (FS Series), SAW oscillators (EG Series and EV Series), and SAW filters (FF Series).

Structure of SAW resonator SAW vibration mode
SAW's output frequency f = k / λ (where λ = electrode interval, k = constant)


SAW filter

This is a filter that uses a SAW. Epson offers SAW filters in models FF-555 and FF-585 and TQS series.



SAW oscillator

This is a crystal oscillator that houses a SAW resonator chip and IC chip including crystal oscillation circuit in a package. Epson offers SAW oscillators under the EG series. In particular, the EG-2121 and EG-2102 have improved frequency-temperature characteristics to one-half their previous levels.

Reference: Frequency versus temperature characteristics



SAW resonator

This is a crystal device that employs a SAW (surface acoustic wave) in order to output a particular resonating frequency as an electrical signal. The element is for a high frequency range (at least several hundred MHz). For description of the SAW's frequency-temperature characteristics, see "Frequency-temperature characteristics". Epson offers SAW resonators under the FS/NS series.

Reference: SAW oscillator , frequency versus temperature characteristics



SIP package


SIP package

Abbreviation for Single In-line Package. This type of package has leads (pins) that protrude from one side, and which are inserted into holes in the circuit board to mount the package.



SMD package

This is a general term for any package that is mounted onto the surface of a PCB. SMD is an abbreviation for "Surface Mounted Device". This is one of the newer types of crystal device packages, which typically use ceramic or plastic as the package material.

Plastic SMD package (SG-8002JF) Ceramic SMD package (SG-710)


SOJ package

Abbreviation for Small Outline J-leaded package. In this surface-mount package, the leads (pins) protrude from both sides and the lead ends are bent inward, beneath the package.

SOJ package crystal oscillator (MC-306) SOJ package crystal oscillator (SG-615)


SOP package

Abbreviation for Small Outline Package. In this surface-mounted package, the leads (pins) protrude from both sides and the lead ends are bent outward.



Reflow

Sealing means that the inside of crystal device container is kept airtight. In order for a crystal unit to stably maintain its characteristics for long, the crystal chip's surfaces, including any electrodes, must be protected from moisture or other impurities in the outside air. To assist in this, nitrogen gas is usually inserted into crystal containers. Sometimes, a vacuum is created in the sealed container of tuning fork crystal units to improve the oscillation efficiency. Package sealing methods have been developed, including insertion through soft wax-like material, resistance welding, molten glass welding, adhesion by resin, and other methods, depending on the package's materials, size, and features.



Serial interface

This is a connection method between devices that communicate by sending signals serially across a data line. The RS-232C, IrDA, USB, and IEEE1394 interfaces are typical serial interfaces. This method is suitable for long-distance transmissions because there is no need to synchronize the data lines.

Reference: Parallel interface



Shock resistance

This refers to a crystal device's resistance to shocks. This is evaluated by the amount of change in characteristics (particularly frequency variation) and damages caused by a specified impact. Quartz crystal is a hard and brittle material that fractures easily, so shock resistance is a key characteristic for crystal devices used in mobile products. In the past, an evaluation method was used whereby a certain amount of shock was applied to crystal products by shock testing equipment. Recently, the evaluation method is used wherein a crystal device fixed in a testing tool weighing 100-gram weight is repeatedly dropped from a certain height.



Shunt capacitance


Equivalent circuit diagram of crystal unit

Shunt capacitance is an electrostatic capacitance component that is generated between two electrodes in a crystal oscillator. It is shown as C0 in the equivalent circuit diagram at right.



Soldering conditions

These are conditions that help ensure the operation and characteristics of mounted devices. When soldering exceeds the specified temperature or time, soldered device's characteristics may be degraded or the device may get damaged.

Reference: Reflow profile



Soldering heat resistance

This refers to resistance against the temperature condition required for soldering to mount devices on circuit boards. Each device is evaluated not only by the heating temperature but also by the changes in characteristics due to solder reflow profile conditions and any damage that has occurred, including in the package. In crystal products, high temperatures can cause gas to occur inside packages and can weaken the adhesive that fastens the crystal chip.

Reflow profile soldered product Pb free soldered product

Reference: Reflow profile



Spacial frequency

It is a quantity that indicates resolution of periodical structure of an image or an object expressed as the number of frequencies resolved per 1 mm. For example, this would be the number of fringes spaced 1 mm apart when viewing a fringe pattern projected onto a CCD or CMOS image sensing device.



Spectral characteristics

Plotted with wavelength on the lateral axis and relative sensitivity (intensity, transmissivity, reflectivity, etc.) on the vertical axis. (Same as electrical frequency characteristics or filter characteristics.)



Standby

The standby is a function which can stop operation of the oscillation circuit and output of a crystal oscillator. This is useful in eliminating power consumption.



Storage temperature

This is the temperature range for maintaining the operability and characteristics of a crystal device that is in storage (not being operated). Storing crystal devices in an environment that is outside this temperature range can cause degradation of characteristics or other damage. Degradation of characteristics can also occur if crystal devices are stored for a long time at temperatures near the upper or lower limits of this range, so Epson recommends that crystal devices be stored under normal room temperature and humidity conditions whenever possible.



Surface Acoustic Wave

See "SAW".

Reference: SAW



Surface mount

See "SMD package".

Reference: SMD package



Synthetic quartz crystal


Synthetic quartz crystal

This refers to quartz crystal that is made artificially, in contrast to naturally occurring quartz crystal. Both types of quartz crystal are used as a material for crystal devices. Whereas naturally occurring quartz crystal contains a lot of impurities and experiences a wide range of quality fluctuation, synthetic quartz crystal contains few impurities, which enables more stable crystal devices to be manufactured. A method called hydrothermal synthesis is used to grow various quartz crystals in specified sizes. The crystals are grown over a period of two months in an autoclave which maintains the processing conditions of a temperature of approximately +400 ℃ and air pressure of 1000 atmospheres.



S-polarized light (Senkrecht polarized light)

P -polarized light is linearly polarized light that runs in a plane formed by the axis of light propagation and the line normal to a sample surface. S- polarized light is linearly polarized light that runs perpendicularly to this plane. In the case of a cubic prism comprising two triangular prisms, the line normal to a sample surface is the line normal to coated surfaces of these two triangular prisms that are opposed and attached each other.




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