IPC-SM-782A 表面安装设计和焊盘设计标准(带BGA).pdf - 第15页

slot or edge, used exclusively to position the board or panel or to mount components accurately . (See Fiducial) *V ia – A plated-through hole used as a through connection, but in which there is no intention to insert a …

Footprint – (see preferred term ‘‘Land Pattern’’)

*Grid – An orthogonal network of two sets of parallel

equidistant lines used for locating points on a printed

board. (Note: Connections should be located on the cross-

points of the gridlines. The position of conductors may be

independent of the grid, i.e., not necessarily following the

gridlines.)

Integrated circuit (IC) – An assembly of miniature elec-

tronic components simultaneously produced in batch pro-

cessing, on or within a single substrate to perform an elec-

tronic circuit function.

*Jumper wire – An electrical connection that is a part of

the original design, added between two points on a printed

wiring board after the intended conductive pattern is

formed.

*Land – A portion of a conductive pattern usually, but not

exclusively, used for the connection, or attachment, or both

of components.

Land pattern – A combination of lands intended for the

mounting, interconnection and testing of a particular com-

ponent.

Leadless chip carrier – An electronic component whose

external connections consist of metallized terminations

containing a single integrated circuit chip.

Leaded chip carrier – An electronic component whose

external connections consist of leads eminating from the

sides of the package, which contains a single circuit chip.

*Master drawing – A document that shows the dimen-

sional limits or grid locations applicable to any or all parts

of a printed board (rigid or ﬂexible), including the arrange-

ment of conductive and nonconductive patterns or ele-

ments; size, type, and location of holes; and any other

information necessary to describe the product to be fabri-

cated.

Mixed mounting technology – A component mounting

technology that uses both through-hole and surface mount-

ing technologies on the same packaging and interconnect-

ing structure.

*Module – A separable unit in a packaging scheme

Nominal – Design dimension for the size of a feature. (The

tolerance on a nominal dimension gives the limits of varia-

tion of a feature size.)

Packaging and interconnecting structure (P&IS) – The

generic term for a completely processed combination of

substrates, metal planes or constraining cores, and intercon-

nection wiring used for the purpose of mounting compo-

nents.

*Plated-through hole (PTH) – A hole in which electrical

connection is made between internal or external conductive

patterns, or both, by the plating of metal on the wall of the

hole.

Primary side – That side of the packaging and intercon-

necting structure that contains the most or more complex

components. The primary side establishes layer one of the

P/I structure. (The same as the ‘‘component side’’ in

through-hole component mounting technology.)

*Printed board – The general term for completely process

printed circuit or printed wiring conﬁgurations. It includes

rigid or ﬂexible, single, double and multilayer boards.

*Printed wiring – The conductive pattern intended to be

formed on a common base, to provide point-to-point con-

nection of discrete components, but not to contain printed

components.

*Registration – The degree of conformity of the position

of a pattern, or a portion thereof, with its intended position

or with that of any other conductor layer of a board.

Secondary side – That side of the packaging and intercon-

necting structure that is opposite of the primary side. (The

same as the ‘‘solder side’’ in through-hole component

mounting technology.)

Single in-Line package (SIP) – A component which termi-

nates in one straight row of pins and lead wires.

Static electricity – An electrical charge that has accumu-

lated or built up on the surface of a material.

Static electricity control – A technique where materials and

systems are employed to eliminate/discharge static electric-

ity buildup by providing continuous discharge paths.

*Supported hole – A hole in a printed board that has its

inside surface plated or otherwise reinforced.

Supporting plane – A planar structure that is a part of a

packaging and interconnecting structure to provide

mechanical support, thermo-mechanical constraint, thermal

conduction and/or electrical characteristics. (It may be

either internal or external to the packaging and intercon-

necting structure.)

Surface mount technology (SMT) – The technology where

electrical connection of components is made to the surface

of a conductive pattern of a printed board and does not uti-

lize component lead holes.

Thermal expansion mismatch – The absolute difference in

thermal expansion of two components.

*Through connection – An electrical connection between

conductive patterns on opposite sides of an insulating base,

e.g., plated-through hole or clinched jumper wire.

Through-hole technology (THT) – An assembly process

for mounting component packages where leads are passed

through supported (plated through) or unsupported (bare)

holes in an interconnection substrate.

*Tooling feature – A speciﬁed physical feature on a printed

board or a panel such as a marking, hole, cut- out, notch,

IPC-SM-782A December 1999

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slot or edge, used exclusively to position the board or panel

or to mount components accurately. (See Fiducial)

*Via – A plated-through hole used as a through connection,

but in which there is no intention to insert a component

lead or other reinforcing material.

Blind via – A via that is connected to either the primary

side or secondary side and one or more internal layers of a

multilayer packaging and interconnecting structure, but not

to both sides.

Buried via – A via that is connected to neither the primary

side nor the secondary side of a multilayer packaging and

interconnecting structure, i.e., it connects only between

inner layers.

Tented via – A blind or through-hole via that has the

exposed surface of the primary or secondary or both sides

of a packaging and interconnecting structure fully covered

by a masking material, such as a dry ﬁlm polymer coating

(solder mask), preimpregnated glass cloth (prepreg), etc., in

order to prevent hole access by process solutions, solder, or

contamination.

3.2 Component Acronyms

In an attempt to standardize

on component characteristics the Joint Electronic Device

Engineering Council (JEDEC) of the Electronic Industries

Association (EIA) has developed a set of recommended

acronyms that can be used to describe the shape, material,

lead position, package style, lead form and lead count.

These details are deﬁned in JEDEC Publication JESD1C

and have been circulated and approved as an international

document published by the International Electrotechnical

Commission (IEC) as IEC Publication 30. These concepts

are supported and adopted in this land pattern document to

facilitate communication between design, component

manufacturer, board manufacturer, quality assurance etc.

Some of the information from the JEDEC publication is

presented to assist the reader. The acronym systems is

divided into six parts. They are:

• SHAPE – A single-letter preﬁx that identiﬁes the

mechanical package proﬁle (round, rectangular, square,

etc.)

• MATERIAL – A single-letter preﬁx that identiﬁes the

predominant package body material (glass, metal,

plastic, etc.)

• POSITION – A single-letter preﬁx that identiﬁes termi-

nal or lead position related to the package proﬁle (see

3.2.1)

• PACKAGE – A double-letter designation that identiﬁes

the package-outline style (see 3.2.2)

• FORM – A single letter suffix that identiﬁes the terminal

or lead form (see 3.2.3)

• COUNT – A one, two, or three-digit suffix that identiﬁes

the number of leads or terminations (12, 84, 160, etc.)

The minimum acronym consists of the position, package,

form and count identiﬁers. Shape and material preﬁxes are

optional acronym designations. As an example the designa-

tion R-PDIP-T14 describes a rectangular part (R), made of

plastic (P), with dual terminals or leads (D), coming from

an in-line package style (IP) with through-hole leads (T)

and a lead count of 14.

3.2.1 Position Designation

The single-letter preﬁx for

terminal position shall be identiﬁed in accordance with

Table 3–1. The position deﬁnition ‘‘terminal’’ applies to

either lead or leadless. The descriptions assume that the

seating plane is the bottom of the package. Reference to

package shape does not take into account ﬂanges, notches

or irregularities.

3.2.2 Package-Outline Style Designators

The package

double-letter designator shall be in accordance with Table

3–2. Figure 3–1 provides some examples of the compul-

sory package outline style acronyms.

3.2.3 Form Designation

The single-letter suffix that

deﬁnes the terminal form (termination or lead) conﬁgura-

tion shall be in accordance with Table 3–3. Figure 3–2

shows a few diagrams of various package lead conﬁgura-

tions.

3.3 Dimensioning Systems

There are many methods of

dimensioning and tolerancing mechanical parts, all of

which are deﬁned in ANSI Y14.5. All the methods work,

but it must be recognized that some methods work better

than others and some methods cost less to inspect or evalu-

ate product than others. This section describes a set of

dimensional criteria for components, land patterns, posi-

tional accuracy of the component placement capability and

the opportunity to create a certain size solder joint com-

mensurate with reliability or product performance analysis.

Sections 8.0 through section 13.0 deﬁne the speciﬁc details

of various electronic and electromechanical component

families. Each section describes the mounting dimensions

for the component and the speciﬁc land pattern that may be

used to surface mount that particular component or compo-

nent family. In addition, an analysis is made to establish

the land pattern sizes that take into account the accuracy of

the placement operation and requirements for the solder

joint.

Proﬁle tolerances are used in the dimensioning system to

control the size range between maximum and minimum

component/lead dimensions without ambiguity. The proﬁle

tolerance is intended to control both size and position of

the land. Figure 3–3 shows the proﬁle tolerancing method.

The use of the proﬁle dimensioning system requires an

understanding of the concepts detailed in ANSI Y14.5. The

use of a set of requirements are adopted and invoke the

following rules, unless otherwise modiﬁed:

December 1999 IPC-SM-782A

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a. All dimensions are basic (nominal)

b. Limits of size control form as well as size.

c. Perfect form is required at maximum dimensions.

d. Datum references and position tolerances apply at maxi-

mum dimensions, and are dependent on feature size.

e. Position dimensions originate from maximum dimen-

sions.

f. Tolerances and their datum references other than size

and position apply regardless of feature size (RFS).

g. Interpretations are per ANSI Y14.5.

The dimensioning concepts used for this system of analy-

sis consider the assembly/attachment requirements as their

major goal. Speciﬁcation (data) sheets for components or

dimensions for land patterns on boards may use different

dimensioning concepts, however, the goal is to combine all

concepts into a single system. Users are encouraged to

establish the appropriate relationship between their dimen-

sioning system(s) and the proﬁle dimensioning system and

analysis concepts described herein to allow for ease of tai-

loring these concepts for robust process performance. As

an example, if the tolerance used for positioning is larger

than the machine tolerance used in production, a single

dimensional change in a ‘‘spread sheet’’ program could

modify the land pattern dimensions shown in sections 8.0

through 13.0 in order to optimize the process for a given

facility.

3.3.1 Component Tolerancing

The component manu-

facturers and the Electronic Industries Association (EIA)

are responsible for the dimensioning and tolerancing of

electronic components. Their concepts have been converted

to a functional equivalent using the proﬁle tolerancing

method with all components shown with their basic dimen-

sions as limit dimensions (maximum or minimum size).

Table 3–1 Terminal Position Preﬁxes

Code Name Position (see notes 1 and 2)

A Axial Terminal extend from both ends in the direction of the major axis of a cylindrical or elliptical

package.

B Bottom Terminals beneath the seating plan of the package.

D Dual Terminals on opposite sides of a square or rectangular package or located in two parallel rows.

E End Terminals are package endcaps having circular or elliptical cross section.

L Lateral Terminals are on the four sides of a square or rectangular package. The preferred name is

‘‘Quad,’’ code Q.

P Perpendicular Pins are perpendicular to seating plan on a square or rectangular package. Restrict to PGA

family.

Q Quad Terminals are on the four sides of a square or rectangular package or located in four parallel

rows.

R Radial Terminals extend radially from the periphery of a cylindrical or spherical package

S Single Terminals are on one surface of a square or rectangular package in a single row.

T Triple Terminals are on three sides of a square or rectangular package.

U Upper Terminals are perpendicular to and opposite the seating plane, and are on one surface of a

package.

X Other Terminal positions other than those described.

Z Zig-zag Terminals are on one surface of a square or rectangular package arranged in a staggered

conﬁguration. Restrict to ZIP family.

NOTE 1: These descriptions assume the seating plane is the bottom of the package.

NOTE 2: Reference to package shape does not take into account ﬂanges, notches, or irregularities.

Table 3–2 Package-Outline-Style Codes

Code Outline Style

CC Chip-carrier package

CY Cylinder or can package

DB Disc-button package

FM Flange-mount package

FO Fiber-optic-device package

FP Flatpack package

GA Grid-array package

IL In-line package. The preferred designator is IP

IP In-line package or inserted package. Restrict to

DIP/SIP/ZIP.

LF Long-form horizontal package.

MA Microelectronic assembly.

MW Microwave package

PF Press-ﬁt package

PM Post-/stud-mount package

SO Small-outline package

SS Special-shape package

UC Uncased chip

XA-XZ Nondeﬁend family; vendor or user option.

IPC-SM-782A December 1999

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