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.

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

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.

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

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

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

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

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.

A device that includes a source and driving electronics. It functions as an electricalto-optical converter.

Underwriter’s Laboratory.

The use of ultrasonic energy along with a chemical solvent to clean a component or a PCB assembly immersed in solvent. Mechanical oscillation is introduced by the ultrasonic energy to facilitate cleaning.

The invisible region of the spectrum just beyond the violet end of the visible region. Wavelengths range from 1 to 400 nm.

In flip chip applications, the material injected under the die after testing to ensure reliability. This material is particularly important for flip chips mounted on substrates with different CTEs than silicon, such as FR-4 and some ceramics.

Operating in one direction only.

Ultraviolet.

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.

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

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

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

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