A production master used in the process of making two or more printed boars simultaneously.
MultimeterA portable test instrument which can be used to measure voltage, current and resistance.
MarginThe distance between the reference edge of a flat cable and the nearest edge of the first conductor.(See also Edge Spacing)
Manhattan_DistanceThe orthogonal distance between two points.
Major_DefectA defect that could result in failure or significantly reduce the usability of the part for its intended purpose.
Multi_layer_PCBPrinted circuit boards consisting of three or more conducting circuit planes separated by insulating material and boned together with internal and external connections of the circuitry as required.
MuffleAn enclosure that is located between the heating elements and the parts being processed that contains the atmosphere required for the re-flow soldering process.
Mounting_HoleA hole used for the mechanical mounting of a printed board or for the mechanical attachment of components to the printed board .
Mother_BoardAlso called back plane, or matrix board. A relatively large printed circuit board on which modules, connectors, sub-assemblies or other printed circuit boards are mounted and inter connections made by means of traces on the board.
ModuleA separable unit in a packaging scheme displaying regularity of dimensions.
ModifierA chemically inert substance added to a resin to change its properties.
Mixed_Component_Mounting_TechnologyA component mounting technology that uses both through-hole and surface-mounting technologies on the same packaging and interconnecting structure.
Mis_registrationThe lack of dimensional conformity between successively produced features or terns.
Minor_DefectA defect which is not likely to reduce the usability of the unit for its intended purpose, It may be a departure from established standard having no significant bearing on the effective use or operation of the unit.
Minimum_Electrical_SpacingThe minimum allowable distance between adjacent conductors that is sufficient to prevent dielectric breakdown, between the conductors at any given voltage.
MilOne thousandth (0.001) of an inch. Not to be confused with Mil (short for millimetre).1Inch=25.4mm; 1mil=0.0254mm.
Micro_stripA type of transmission line configuration which consists of a conductor over a parallel ground plane, and separated by a dielectric.
Micro_sectioningA destructive test procedure in which a section of specimen it cut and removed for close examination.
MetallizationA deposited or plated thin metallic film used for its protective or electrical properties.
Metal_Clad_Base_MaterialBase material covered with metal on one or both of its sides.
MeniscusThe contour or shape of molten solder as formed by surface tension forces in turn controlled by wetting.
Melting_RangeThe temperature range over which the solder alloy melts .An alloy with a single melting point, rather than a melting range, is known as a eutectic alloy .
MELFA metal electrode leadless face surface mount component that is round with metallic cap terminations.
MeaslingA condition existing in the base laminate in the form of discrete white sports or crosses below the surface of the base laminate, reflecting a separation of fibres in the glass cloth at the weave intersection.
Mean_Time_between_Failure_(MTBF)The statistical mean average time interval, usually in hours, that may be expected between failures of an operating unit. Results should be designated actual. Predicted or calculated.
MCRMoulded Carrier Ring. A tape of fine-pitch chip package named for the method of supporting and protecting the leads. The leads are left straight; the ends of the leads are embedded in a strip of plastic, which is the Moulded Carrier Ring.
Maximum,_Plated_Through_hole_SizeA hole size equal to the specified hole size before plating, plus the manufacturing tolerance, less twice the minimum plating thickness.
Master_PatternAn accurately scaled pattern which is used to produce the printed circuit within the accuracy specified on the master drawing.
Mass_SolderingMethods of soldering in which many joints are made in the same operation.
MaskA material applied to enable selective etching, plating or the application of solder to a printed circuit board.
Master_DrawingA document that shows the dimensional limits or grid locations applicable to any or all parts of a printed board(rigid or flexible),including the arrangement of conductive and non-conductive patterns or elements; size, type and location of holes.
Mass_ArtworkA document showing dimensional limits and grid locations for all parts ofan assembly to be fabricated. It includes the arrangement of conductors and non-conductive patterns and the size, type and location of holes.
MAR(Minimum_Annular_Ring)The minimum metal width, at the narrowest point between the circumference of the hole and the outer circumference of the land. This measurement is made to the drilled hole on internal layers of multi-layer printed circuit board to the edge of the plating on outside layers of multi-layer boards and double-sided boards.