Wave Soldering

The technique of joining parts to a PCB by passing the assembly over a wave of molten solder so as to coat the pre-fluxed areas to be joined.

Wave Exposure

A surface condition of base material in which the unbroken fibres of woven glass cloth are not completely covered by resin.

Voltage Plane

A conductor or portion of a conductor layer on or in a printed board which is maintained at other than ground potential. It can also be used as a common voltage source, for heat sinking, or for shielding.


The absence of any substances in a localized area.


The property of a fluid that enables it to develop and maintain a level of shearing stress dependent upon the velocity of flow and then offer continued resistance to flow. The absolute unit of viscosity measurement is poise, or more commonly, centipoise.

Virtual Prototype

A virtual (computer model) representation of an electronic product that can be used to explore different design scenarios and then verify that the product will work as planned before building a physical implementation.


A plated through-hole used as an interlayer connection and not as a terminating point for a component lead. It may also be blind (incomplete penetration) or buried (non-surfacing).

Via Hole

A plated through-hole whose only purpose is to connect a track on one layer or side of the board through to a track on another layer or side. In a via, there is no intention to insert a component lead or other reinforcing material.

Vapour Phase

The solder re-flow process that uses a vaporized solvent as the source for heating the solder beyond its melting point,creating the component-to-board solder joint.

Vacuum Pick-up

A component handling tool with a small vacuum cup for ease of pick-up and removal during de-soldering.

Unsupported Hold

A hole containing no conductive material nor any other type of reinforcement.

Underwriters’ Symbol

A logotype authorized for placement on a product which has been recognized (accepted) by Underwriters Laboratories, Inc. (UL).


A groove or excavation at one edge of a conductor caused by etching.

Ultrasonic Soldering

Fluxless soldering wherein molten solder is vibrated at ultrasonic frequencies while making the joint.


Underwriter’s Laboratories, Inc., a corporation for the purpose of establishing safety standards on types of equipment or components in USA and Canada.


The deformation of a rectangular sheet, panel or printed board, that occurs parallel to a diagonal across its surface in such a way that one of the comers of the sheet is not in the plane formed by the other three corners.

Trim Lines

Lines which define the borders of a printed board.


Dielectric material with higher glass transition temperature and better thermal stability than epoxy resin, however, more expensive and not in common use.

Transmission Line

A signal-carrying circuit composed of conductors and dielectric material with controlled electrical characteristics used for the transmission of high-frequency or narrow-pulse type signals.

Transmission Cable

Two or more transmission lines.

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