Yield Strength

The load in pounds per square inch where the material under test begins to change dimensions and will not completely recover when the load is removed. Yield strength will normally be lower than ultimate strength. Generally speaking, the more rigid a material is, the closer will be yield and ultimate strengths. Furthermore, the more resilient a material is, the greater the spread between yield and ultimate strengths.

Wire Bonding

The use of fine wires to connect semiconductor packages to the next level of packaging. Wires are composed of gold or aluminum.

Working life

The period of time during which an epoxy after mixing with a curing agent, remains workable and suitable for use.

Wetting Balance

An instrument used to measure wetting forces, and consequently, estimate solderability.

Whisker

A metallic growth, needle-like in size, that appears on the surface of a PCB.

Wetting

The thorough impregnation of a material by a liquid. The more viscous a fluid, and the higher its surface tension, the more difficult it is for the liquid to “wet” materials. Certain additives, for example, water softeners, reduce surface tension, or viscosity and improve wetting properties, allowing the material to flow out more.

Wavelength Isolation

A WDM’s isolation of a light signal in the desired optical channel from the unwanted optical channels. Also called far-end crosstalk.

Wavelength

The distance between points of corresponding phase of two consecutive cycles of a wave. The wavelength is related to the propagation velocity, and the frequency. It is indirectly proportional to frequency.

W

See Watt.

Visible Light

Electromagnetic radiation visible to the human eye; wavelengths of 400-700 nm.

V

Volt. Unit of eletric potential, also known as electromotive force. Represents the potencial difference between two points of a conducting wire carrying a constant current of 1 ampere when the power dissipated between these points is equal to 1 watt.

Wave Soldering

A process in which many potential solder joints are brought in contact with a wave of molten solder for a short period of time and are soldered simultaneously.

WAN

See wide area network.

Watt

Linear measurement of optical power, usually expressed in milhwatts, microwatts, and nanowatts.

Viscosity

The property of resistance to flow exhibited within the body of a fluid. Usually measured in centipoise.

Visible Spectrum

Light which can be seen by the unaided human eye, defined in our case as between 400 nm and 750 nm.

Vias

Drilled holes in laminate that interconnect different layers of circuitry. Vias can be used for electrical connections or thermal dissipation.

Waffle Pack

A matrix tray for holding bare die. Typically, waffle packs are 2″ x 2″ or 4″ x 4.” The pockets for die in waffle packs are typically designed for specific die sizes; they are not standardized.

Waveguide

A system or material designed to confine and direct electromagnetic waves in a direction determined by its physical boundaries.

Wave Cleaning

Cleaning a PCB by passing it through a wave of solvents (similar to the concept used in a wave fluxer or a wave soldering process).