IPC-T-50F_.pdf.pdf - 第42页

Laminate Thickness 41.0673 The thickness of single- or double-sided metal-clad base material prior to any subsequent processing. (See also ‘ ‘Board Thickness.’ ’) Laminate (n.) 55.0672 A product made by bonding together …

Intermetallic Compound, Solder 75.1428

An intermediate layer in a wetted solder connection

between the wetted surface and the solder, consisting of the

solution of at least one constituent of the wetted surface

and at least one constituent of the solder.

Intermittent Fault 97.0657

A fault whose effect on a circuit appears and disappears at

irregular intervals.

Internal Layer 22.0658

A conductive pattern that is contained entirely within a

multilayer printed board.

Interstitial Via 22.0659

see ‘‘Blind Via’’ and ‘‘Buried Via.’’

Intumescence 56.0660

The foaming or swelling of a material when it is exposed

to high surface temperatures or ﬂames.

Ion Exchange 76.0661

A reversible chemical reaction between a solid and a ﬂuid

by means of which ions are interchanged from one sub-

stance to another.

Ionic Cleanliness 76.0663

The degree of surface cleanliness with respect to the num-

ber of ions or weight of ionic matter per unit square of sur-

face.

Ionizable (Ionic) Contamination 76.1222

A polar (ionic) compound, usually a processing residue,

that dissolves in water as free ions. (This includes ﬂux

activators, ﬁnger prints, etching or plating salts, etc., that

decrease the resistivity of water when they are dissolved in

it.)

J-Leads 36.1752

The preferred surface mount lead form used on PLCC’s, so

named because the lead departs the package body near its

Z axis centerline, is formed down then rolled under the

package. Leads so formed are shaped like the letter ‘‘J.’’

Job Set 25.0664

A group of one or more data-information modules.

Jumper Wire 37.0665

A discrete electrical connection that is part of the original

design and is used to bridge portions of the basic conduc-

tive pattern formed on a printed board. (See also ‘‘Hay-

wire.’’)

Junction Temperature 35.0666

The temperature of the region of a transition between the

p-type and n-type semiconductor material in a transistor or

diode element.

Just-in-Time (JIT) 17.1429

Production control techniques that minimize inventory by

delivering parts and material to a manufacturing facility

just before they are incorporated into a product.

Kerf 77.0667

A laser-beam or abrasive-jet cut (slit) in a ﬁlm component

as a part of the trimming operation.

Key 37.0668

A device that assures that the coupling of two components

can occur in only one position.

Keying (n.) 37.1430

A device that is used in addition to, or in lieu of, a polar-

ization feature to assure that the coupling of identical mat-

ing components can occur in only one position.

Keying (v.) 37.1431

The use of a device in addition to, or in lieu of, a polariza-

tion feature to assure that the coupling of identical mating

components can occur in only one direction.

Keying Slot 22.1432

A slot in a printed board that permits the printed board

assembly to be plugged into its mating connector and pre-

vents the board from being plugged into any other connec-

tor. (See also ‘‘Polarizing Slot.’’)

Keyway 37.0669

A general term that encompasses both keying slots and

polarizing slots.

Known Good Board (KGB) 92.0671

A correctly fabricated printed board that serves as a stan-

dard unit by which others can be compared.

Known Good Assembly (KGA) 92.0670

A correctly operating printed board assembly that serves as

a standard unit by which others can be compared.

L Cut 77.1433

A trim notch in a ﬁlm component that is created by a cut

that starts perpendicular to the component’s major axis and

then turns ninety degrees to complete the trimming opera-

tion.

June 1996 IPC-T-50F

Laminate Thickness 41.0673

The thickness of single- or double-sided metal-clad base

material prior to any subsequent processing. (See also

‘‘Board Thickness.’’)

Laminate (n.) 55.0672

A product made by bonding together two or more layers of

material.

Laminate Void 91.0674

The absence of resin or adhesive in an area that normally

contains them.

Land 22.1622

A portion of a conductive pattern usually, but not exclu-

sively, used for the connection and/or attachment of com-

ponents.

Land (Drill) 51.0676

The peripheral portion of the drill body that is between

adjacent drill ﬂutes.

Land Pattern 22.0678

A combination of lands that is used for the mounting, inter-

connection and testing of a particular component.

Land Width Angle (Drill) 51.1223

The angle between the leading edge and the heel of a drill

land as measured at the drill axis.

Land Width (Drill) 51.0679

The perpendicular distance from the leading edge to the

heel of a drill land.

Landless Hole 22.0677

A plated-through hole without land(s).

Lap Shear Strength 74.0680

The shearing pressure at which an adhesive-bonded (and

cured) lap joint fails. (See also ‘‘Shear Strength’’ and ‘‘Tor-

sional Strength.’’)

Large-Scale Integration (LSI) 30.0681

An integrated circuit with over 100 gates.

Larger-the-Better Characteristic 91.1434

A parameter of quality that improves performance as its

value increases. (See also ‘‘Nominal-Is-Best Characteris-

tic’’ and ‘‘Smaller-the-Better Characteristic.’’)

Laser Soldering 75.1753

A soldering process using laser energy, generally in the

infrared wave length, to heat and form solder bonds.

Laser Trimming 77.0682

The modiﬁcation of a ﬁlm component’s value by the

removal of ﬁlm by applying heat from a focused laser

source.

Latch (Connector) 37.0683

A device at both ends of a connector header that is used to

hold in place and eject a mating receptacle connector.

Layback 51.0684

The negative rake angle or rolled condition in the face of a

drill ﬂute. (See Figure L-1.) (See also ‘‘Hook’’ and ‘‘Over-

lap, Drill.’’)

Layer 22.1624

Stratum of a Printed Board. Layers are differentiated

according to their function (conductor layer, insulating

layer) and their location.

Layer-to-Layer Registration 55.0685

The degree of conformity of a conductive pattern, or por-

tion thereof, to that of any other conductor layer of a

printed board.

Layer-to-Layer Spacing 22.0686

The thickness of dielectric material between adjacent lay-

ers of conductive patterns in a printed board. (See Figure

L-2.)

Leaching, (v.) Metalization 75.0687

The loss or removal of a basis metal or coating during a

soldering operation.

IPC-I-002328

Figure L–1 Layback

Lay Back

▼

IPC-I-000000

Figure L–2 Layer-to-layer spacing

IPC-T-50F June 1996

Lead 36.0688

A length of insulated or uninsulated metallic conductor that

is used for electrical interconnections.

Lead Extension 75.0691

That part of a lead or wire that extends beyond a solder

connection.

Lead Frame 74.0692

The metallic portion of a component package that is used

to interconnect with semiconductor die by wire bonding

and to provide output terminal leads.

Lead Mounting Hole 22.0695

see ‘‘Component Hole.’’

Lead Pin 36.0696

see ‘‘Component Pin.’’

Lead Projection 73.0697

The distance that a component lead protrudes through the

side of a printed board that is opposite from the one upon

which the component is mounted.

Lead Wire 36.0698

see ‘‘Component Lead.’’

Leaded Chip Carrier 31.1224

A chip carrier whose external connections consist of leads

that are around and down the side of the package. (See also

‘‘Leadless Chip Carrier.’’)

Leaded Surface-Mount Component 33.1435

A surface-mount component for which external connec-

tions consist of leads that are around and down the side of

the package. (See Figure L-3.) (See also ‘‘Leadless

Surface-Mount Component.’’)

Leadless Chip Carrier 33.1436

A chip carrier whose external connections consist of met-

allized terminations that are integral part of the component

body. (See also ‘‘Leaded Chip Carrier.’’)

Leadless Component 30.1754

see Leadless Surface Mount Components .

Leadless Device 33.0694

see Die and Leadless Surface Mount Component .

Leadless Inverted Device 33.1437

A shaped metallized-ceramic form used as an intermediate

carrier for diode or transistor die that has been especially

adapted for leadless surface mounting.

Leadless Surface-Mount Component 33.1438

A surface-mount component whose external connections

consist of metallized terminations that are integral part of

the component body. (See also ‘‘Leaded Surface-Mount

Component.’’)

Leakage Current 21.0699

The undesired ﬂow of electrical current over or through an

insulator.

Learn Time 92.0700

The time it takes to do initial programming (teaching) to

store feature coordinate locations and other data in an

inspection/test machines memory.

Least Material Condition (LMC) 22.0701

The condition in which a feature of size contains the least

amount of material within the stated limits of size.

Legend 22.1439

A format of letters, numbers, symbols and patterns that are

used primarily to identify component locations and orien-

tations for convenience of assembly and maintenance

operations.

Leno End Out 44.0702

Warp-end wrapper that is missing from the end of a fabric.

Levelling 56.0703

see ‘‘Fusing.’’

Levelling Flux 56.0704

see ‘‘Fusing Flux.’’

Levelling Oil 56.0705

see ‘‘Fusing Oil.’’

Library 20.0706

A catalog of related items that contains all of the informa-

tion about the items that is necessary for processing by a

computer program.

Lifted Land 60.0707

A land that has fully or partially separated (lifted) from the

base material, whether or not any resin is lifted with the

land.

IPC-I-001034

Figure L–3 Leaded surface mount component gull-wing

shaped lead

FOOT

HEEL

TOE

LAND

KNEE

UPPER

BEND RADIUS

LOWER

BEND RADIUS

June 1996 IPC-T-50F