Vapour Phase Reflow

Soldering accomplished by primarily conductive heat transfer during condensation of a high-temperature vapor of boiling fluorocarbon. The latent heat of vaporization, given up during condensation of vapor on the relatively cool workpiece is the major source of heat for conductive transfer.

Via

A plated-through-hole used as a through connection between two or more layers of a multilayer printed circuit board in which there is no intention to insert a component lead or other reinforcing material.

Viscosity

A measure (in pascal/sec) of a material’s resistance to flow or change shape. Frequently it is measured in centipoises (cps) , which is one millipascal.

Visual Examination

The qualitative observation of physical characteristics ,  utilizing the unaided eye or within stipulated levels of magnification.

Void

The absence of material in a localized area. See also Blowhole.

Wave Soldering

A process of joining metallic surfaces (without the melting of the base metals) through the introduction of molten solder to metallized areas. Surface mount devices are attached using adhesive and are mounted on the secondary side of the PWB.

Wettability

The degree to which a metal surface will accept the flow of solder as permitted by its freedom of oxides.

Wetting

The effect of molten solder spreading along the base metal/ metallization surfaces to produce complete and uniform solder coverage. A good intermetallic bond between surfaces is formed. Good wetting is indicated by low contact angle between the solder fillet and the base metal/ metallization.

Whiskers

Slender acicular (needle shaped) metallic growth between conductors and lands.

Wicking

Absorption of liquid by capillary action along the fibers of the base metal. See also solder Wicking.

Work Life (of solder paste or adhesive)

The time a material can be left on the stencil without a change in its properties.

Worknest

The stage that holds the substrate throughout the print cycle.