SMT: Glossary Of Terms - Uvwxyz Stage
Glossary of terms
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.
