PCB Glossary : H to M

Hole Breakout:
A condition in which a hole is partially surrounded by the land.

Hole Pattern:
The arrangement of all holes in a printed board with respect to a reference point.

Hot Air Solder Leveling (HASL):
A method of coating exposed copper with solder by inserting a panel into a bath of molten solder then passing the panel rapidly past jets of hot air.

Imaging:
The process by which panelization data are transferred to the photoplotter, which in turn uses light to transfer a negative image circuitry pattern onto the panel.

Impedance:
The total passive opposition offered to the flow of electric current. This term is generally used to describe high-frequency circuit boards.

Inner-layers:
The internal layers of laminate and metal foil within a multi-layer board.

Insulation Resistance:
The electrical resistance of an insulating material that is determined under specific conditions between any pair of contacts, conductors, or grounding devices in various combinations.

Known Good Board (KGB):
A board or assembly that is verified to be free of defects. Also known as a Golden Board.

Laminate:
The plastic material usually reinforced by glass or paper that supports the copper cladding from which circuit traces are created.

Laminate Thickness:
Thickness of the metal-clad base material, single- or double-sided, prior to any subsequent processing.

Laminate Void:
An absence of epoxy resin in any cross-sectional area that should normally contain epoxy resin.

Land:
The portion of the conductive pattern on printed circuits designated for the mounting or attachment of components. Also called a pad.

Layup:
The process in which treated prepregs and copper foils are assembled for pressing.

Legend:
A format of lettering or symbols on the printed circuit board: e.g. part number, serial number, component locations, and patterns.

Liquid Photoimageable Soldermask (LPI):
A mask using photographic imaging techniques to control deposition.

Line:
See Conductor.

Lot:
A quantity of circuit boards that share a common design.

Major Defect:
A defect that is likely to result in failure of a unit or product by materially reducing its usability for its intended purpose.

Mask:
A material applied to enable selective etching, plating, or the application of solder to a PCB. Also called soldermask or resist.

Metal Foil:
The plane of conductive material of a printed board from which circuits are formed. Metal foil is generally copper and is provided in sheets or rolls.

Microsectioning:
The preparation of a specimen of a material, or materials, that is to be used in metallographic examination. This usually consists of cutting out a cross-section followed by encapsulation, polishing, etching, and staining.

Minor Defect:
A defect that is not likely to result in the failure of a unit of product or that does not reduce the usability for its intended purpose.

Multi-Layer Board:
Printed boards consisting of a number (four or more) of separate conducting circuit planes separated by insulating materials and bonded together into relatively thin homogeneous constructions with internal and external connections to each level of the circuitry as needed.