Major defect

A defect likely to result in the failure of a unit or product by making it unusable.

Master Drawing

A document showing dimensional limits or grid locations for all parts on a PCB. Conductors and nonconductive material of  a PCB ( e.g. dielectric, resist, etc.) are also shown.

Measling

An internal condition that occurs in laminated base material in which the glass fibers are separated from the resin at the weave intersection. This condition manifests itself in the form of discrete white spots below the surface of the base material. This is often caused due to thermally induced stress.

MELF, Metal  Electrode Leadless Face

A component  package that is cylindrical and has metalized terminations on its two ends for surface mounting. The package is commonly used for diodes, capacitors, and resistors.

Metallization

A metallic deposited on  substrates and component terminations by itself, or over a base metal, to enable electrical and mechanical interconnections.

Mixed Mounting Technology

A component mounting technology that uses both through-hole and surface mount components on the same packaging and interconnecting structure.

Multilayer Board

A printed wiring board that uses more than two layers for conductor routing. Internal layers are connected to the outer layers by way of plated via holes.

Neutralizer

An alkaline chemical added to water to improve its ability to dissolve organic acid flux residues.

Nonwetting`

A condition whereby a surface has contacted molten solder, but the solder has not properly "wetted" all of the surface. The base metal remains exposed. Nonwetting is caused primarily due to impurities acting as physical barriers (intermetallic or oxide) between surfaces to be joined.

Open

Two electrically connected points that are electrically separated during the process of manufacturing. The reasons may be over-etching  or non-planarity of the leads at the point of connection etc.

Outgassing

De-aeration or other gaseous emission from a printed circuit board or solder joint.