Quartz Crystals Glossary

• Aging

  It is the Change of nominal frequency and / or the resistance of a quartz crystal unit through the time.

• Angle

  It is the angle at which a resonator plate is cut from the quartz stone in relation to the original crystallographic axes. The angle of cut is critical to the performance of the crystal unit, particularly for frequency deviation over a temperature range.

• AT cut

  The commercial designation for a specifically oriented resonator plate, having desirable and repeatable operating characteristics. The "AT cut" is the most popular thickness-shear crystal unit manufactured today.

• AT Strip

  AT-cut crystal but in the shape of a rectangular strip. It has a higher ESR than a round AT-cut crystal but is smaller in size, thus allowing smaller crystal packages.

• Axis

  Direction in quartz stone. The plural is "axes."

• Base

  Base is the lower portion of a crystal holder. The base incorporates a resonator mounting structure and leads or pins to connect the device to an external circuit. Please also refer to "Holder."

• Bevel

  Modification to one or both of the major faces of a resonator plate, in which the face is altered for a partially spherical configuration. Please also refer to "Contour."

• Blank

  Quartz resonator plate. Also known as "wafer," "plate," or "resonator."

• BT cut

  Commercial designation for a specifically oriented resonator plate, having well known and repeatable characteristics. "AT-cut" is more popular than "BT-cut"

• C0

  Also known as "Shunt Capacitance."

• C1

  Also known as "Motional Capacitance." Often also abbreviated as "Cm."

• Capacitance

  Property exhibited by two conductors separated by a dielectric where an electric charge becomes stored between the conductors. Measured in "farads" and identified with the letter "C."

• Capacitor

  Passive electronic circuit component in its simplest form; consists of two metal electrodes separated by a dielectric.

• Can

  Please refer to "Cover"

• C.I.

  Abbreviation for "crystal impedance," sometimes also known as "resistance."

• C.I.M.

  Abbreviation for "crystal impedance meter." Please refer to "Test Set"

• Cold Weld

  Consist of a procedure in which the base and can are dissimilar metals that are pressed together to form one metal.

• Contour

  Modification to one or both of the major faces of a resonator plate, where the face is altered to have a completely spherical configuration. Please also refer to "Bevel."

• Coupled Mode

  An unwanted mode that is energized at the same frequency as the wanted mode; thus, draining energy from the desired mode.

• Cycle

  A complete repetition of an event

• Deviation

  Amount by which a quantity differs from its nominal value. In this case, the amount by which a frequency differs from the nominal or specified frequency.

• Dew Point

  The temperature at which components of a gas material starts to condense into liquid.

• Dip

  Term used to describe a sudden increase of activity, followed by a return to the previous level of the activity of a crystal unit.

• Drive Level

  Amount of power dissipated by the oscillating crystal unit. Expressed in terms of mW.

• Equivalent Circuit

  Vibration of a crystal is actually a mechanical vibration. However, the crystal unit can be expressed by two terminal networks if its behavior is electrically converted. The series circuit consisting of L1, C1 & R1 is related to elastic vibration, while the element C0 is connected in parallel to the series arm as a capacitance attributable to the dialectic body of a quartz crystal plate. The resistance R1 is a resonance resistance of the crystal unit at the series resonance frequency.

• ESR

  It is the abbreviation for "Equivalent Series Resistance." A crystal unit has a resistive element. This term is required to define and quantify that characteristic.

• Etch

  A process crystal manufacturers use to improve the surface condition of a crystal and to increase the frequency of a blank. The word "etch" is used to describe the material used in the etch process, as well as the process itself.

• Frequency

  It is a periodic repetition of an event within a unit of time. In an electrical circuit, it is the number of waves that pass through a given point in one second. In other words, it is the number of times a resonator plate oscillates or vibrates in one second. The customer usually specifies the nominal or desired frequency.

• Frequency Stability

  The acceptable deviation usually represented in parts per million (PPM), over a specified temperature range. Deviation is referenced to the measured frequency at +25? C.

• Frequency Tolerance

  The acceptable deviation from nominal frequency usually represented in parts per million (PPM), at a specific temperature, usually +25? C.

• Fundamental

  Lowest frequency a resonator plate will oscillate. Usually set by the physical dimensions of the plate.

• Geometry

  Shape of the resonator plate in a crystal unit. There are 3 geometrical forms available: Flat, Contoured, and Beveled.

• Henry

  Basic unit of inductance, represented by the letter "H." One henry of inductance is produced in a closed circuit by changing current uniformly at the rate of one Ampere per second.

• Hertz (Hz)

  Basic unit of measurement of frequency, "Hertz" used instead "cycle per second". Also used to denote one complete occurrence of an event in 1 second

• Impedance

  Total opposition presented by a circuit or device to the flow of alternating current. Impedance is measured in "ohms", denoted by the letter "Z."

• Inductance

  In a conductor, or circuit, the inertial property that opposes the flow of current when a voltage is applied. Inductance is identified by the letter "L" and measured in "henries."

• Inductor

  Electronic component used to introduce inductance into a circuit.

• Insulator

  Any material that does not allow electricity to pass though easily

• ISO

  Abbreviation for "International Organization for Standardization."

• Kilo

  A prefix abbreviated "k," used to denote units of thousands. One "Kilo" is one thousand. In our industry, a frequency of one kilohertz is a frequency of one thousand hertz (cycles per second).

• KHz

  Abbreviation for "kiloHertz," used to describe the frequency of a crystal or oscillator in terms of thousands of Hertz (cycles per second).

• Load Capacitance

  It is the value of capacitance used in conjunction with the crystal unit. Load capacitance is a parameter normally set by the customer, typically expressed in pF (picoFarads).

• Load Resonance

  Term used to describe a crystal unit operating in conjunction with load capacitance.

• Mega

  Abbreviated with the capital letter "M," and used to denote units of millions, 106. One "Mega" is equal to one million. In this industry, one Mega hertz is a frequency of one million hertz (cycles per second).

• Milli

  Abbreviated "m," used to denote units of thousandths, 10-3. One "milli" is exactly the same as 1/1000th of a unit.

• MHz

  Abbreviation for "MegaHertz," describes the frequency of a crystal or oscillator in terms of millions of Hertz (cycles per second). A frequency denoted as "10.0 MHz" is the same as frequency of 10,000,000 Hertz (cycles per second).

• Motional Capacitance

  Abbreviated as "Cm" or "C1", it is the parameter associated with a quartz crystal unit, illustrates the electronic equivalence of the mechanical elasticity of the unit.

• Motional Inductance

  Abbreviated as "Lm" or "L1", it is the parameter associated with a quartz crystal unit, illustrates the electronic equivalence of the mechanical mass of the unit.

• OEM

  Abbreviation for "Original Equipment Manufacturer."

• Operating Temperature Range

  Temperature range at which the crystal's characteristics are guaranteed.

• Oscillation Mode

  A quartz crystal is designed to vibrate either on its fundamental frequency or one of its overtones. Deciding which oscillation mode to use becomes critical as frequency becomes higher. Fundamental vibration mode normally can go as high as 40MHz; although it may be more precise, cost can be an issue. Using overtones for high frequencies can be cost savings, however, it might not be as precise as desired.

• Overtone

  Odd numbered multiple of the fundamental frequency.

• Package

  Holder used to contain the crystal blank.

• Parabolic Temperature Curve

  BT-cut and Tuning Fork crystals' frequencies follow a parabolic curve over temperature. The frequency will change or decrease as the temperature goes above or below the turnover temperature.

• Parallel Resonant

  Oscillator circuit is normally uses a crystal unit that is designed to operate with a specified value of load capacitance. Resulting in a crystal frequency higher than the series resonant frequency, but lower than the true parallel resonant frequency.

• PF

  Abbreviation for "picoFarad," used to describe a fractional part 10-12, (one trillionth) of one Farad.

• Pico

  A prefix used to describe a sub-multiple of a number. One pico is one trillionth, 10-12, of a unit.

• Plate

  A quartz blank or resonator.

• Polish

  Polish is a term used to describe the process used in the manufacture of some types of quartz crystals. Which results in a very fine surface finish. Polish is also used to denote the material used in this process.

• PPM

  Abbreviation for "Parts Per Million," a method of calculation used to specify the acceptable frequency deviation of a crystal or oscillator.

• Pullability

  Change in frequency of a crystal unit; either from the natural resonant frequency (Fr) to a load resonant frequency (FL); or from one load resonant frequency to another. Frequency can be pulled in a parallel resonant circuit by changing the value of load capacitance.

• Quartz

  It is the crystalline form of Silicon Dioxide (SiO2). Material from which a blank is made.

• Quartz Crystal Unit

  A finished quartz crystal; consists of a resonator plate with electrodes, holder with suitable mounting structures, and a permanently sealed cover. Usually referred simply as a "crystal."

• Reactance

  Opposition to an alternating current presented by inductance, capacitance, or a combination of the two. Measured in "ohms" and denoted with the letter "X."

• Resistance

  The opposition to current flow in a circuit represented by the letter "R" and is measured in "ohms."

• Resistance Weld

  Procedure involving pressure sealing with electricity and back filling with nitrogen to force out oxygen and moisture. This process provides superior aging characteristics.

• Resistor

  Component used to introduce resistance into a circuit.

• Resonant Frequency

  Natural frequency at which a device vibrates. Abbreviated as "Frq" or "frq."

• Resonance

  Creation of vibrations in a system by applying periodic force; which is present when the frequency of the applied force is equal to the natural frequency of the system.

• Resonator

  Part that is capable of being set into resonance by the application of a periodic force.

• Second

  Basic unit of measurement of time, for our purposes, one "second" is 1/60th of a minute.

• Series Resonance

  Condition when a crystal unit is operated without the presence of load capacitance. "Series Resonance" is usually described as "series."

• Shunt Capacitance

  Parameter associated with a quartz crystal unit, used to denote capacitance resulting from the presence of the electrodes plus stray capacitance associated with the holder.

• SMD

  Abbreviation for "Surface Mount Device."

• Spur

  Substitution for the term "Spurious Frequency Response." Spur is used to describe a frequency occurring at some point higher than the desired mode but lower than the next overtone.

• Tape and Reel

  A packaging style which, can accommodate automated pick & place equipment.

• Test Set

  Measures the frequency and resistance characteristic of a quartz crystal unit. Also referred as "crystal impedance meter," abbreviated as "C.I.M."

• Trim Sensitivity

  Measurement of the incremental fractional frequency change for an incremental change in the value of load capacitance. Trim sensitivity (S) is expressed in terms of PPM/pF and is calculated as follows: Where (Ct) is the sum of the shunt capacitance (CO) and the load capacitance (CL).

• Turnover Temperature

  Temperature at which, the nominal frequency is at the up-most part of the parabolic curve.

• Twinning

  A condition within quartz stone where the optic and/or the electric axis suddenly reverse its natural order of polarity.

• Volt

  Basic practical unit of difference of (electrical) potenti