IPC-CM-770D-1996.pdf - 第22页

January

1996

IPC-CM-770

3.46 *Supported Hole

A hole in a printed board that has

its inside surface plated or otherwise reinforced.

3.47 *Supporting Plane

A planar structure that is a part

of a packaging and interconnecting structure in order 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.) (see also “Constraining Core.”)

3.48 *Surface Mounting

The electrical connection of

components to the surface of a conductive pattern that does

not utilize component holes.

3.49 Thermal Expansion Mismatch

The absolute differ-

ence in thermal expansion of two components, usually a

component and a packaging and interconnecting structure,

due to the influence of heat dissipation of an operating cir-

cuit and/or to changes in ambient temperature. (This term

is not to be confused with Coefficient of Thermal Expan-

sion Mismatch).

3.50 *Through Connection

An electrical connection

between conductive patterns on opposite sides of an insu-

lating base, e.g., plated-through hole or clinched jumper

wire.

3.51 *Tooling Feature

A physical feature that is used

exclusively to position a printed board or panel during a

fabrication, assembly or test process. (See also “Locating

Edge,” “Locating Edge Marker,” “Locating Notch,”

“Locating Slot,” and “Tool Hole.”)

3.52 *Unsupported Hole

A hole in a printed board that

does not contain plating or other type of conductive rein-

forcement.

3.53 *Via Hole

A plated-through hole that is used as a

interlayer connection, but in which there is no intention to

insert a component lead or other reinforcing material. (See

also “Blind Via” and “Buried Via”.)

Blind Via

-

A plated-through hole connected to either the

primary side or secondary side and one or more internal

layers of a multilayer packaging and interconnecting

structure.

Buried Via

-

A plated-through hole connected to neither

the primary side nor the secondary side of a multilayer

packaging and interconnecting structure: i.e., it connects

only internal layers.

Tented Via

-

A blind or through via whose exposed sur-

face(s) is fully covered by a masking material, such as

dry

film polymer coating (solder mask), preimpregnated glass

cloth (prepreg), etc., in order to prevent hole access by

process solutions, solder, or contamination.

*Through Via

-

A plated-through hole that connects the

primary side and secondary side of a packaging and inter-

connecting structure.

4.0 COM PONENT TYPE

This section contains a general introduction to the kinds of

components that will be discussed in detail in Parts Two

through Four (Sections

5

through

19).

Common character-

istics of components, component selection and general

issues will be considered here.

Components are selected for electrical, thermal, or

mechanical characteristics that are determined by the

requirements of the contents of the package. The material

composition, finish and configuration of both the body and

the terminations of a component must be considered in the

choice of assembly methods.

All components must be qualified for the assembly pro-

cesses to be used. The physical dimensions of the compo-

nent must adequately mate with the physical handling

devices of the placement equipment. The parts must not be

degraded, physically or electrically, by soldering or other

high temperature processes used. Also, the parts must be

able to tolerate exposure to the chemicals used in adhesive

bonding, soldering, cleaning or any other chemical process-

ing.

Electronic components come in a great variety of package

styles and shape. This relates not only to the electrical

functions which the components perform but sometimes

the same function is available in different packaging con-

figuration.

Component selection should consider the following factors

when applicable:

Electrical Characteristics

Electrical Performance

Mating Forces

Environmental Requirements

Durability

Repairability

Manufacturing Methods

Mechanical Requirements

Thermal Requirements

Electrical Environment

PlacemendAttachment Equipment

Polarization

Cleaning

Corrosion

Part IdentificationNerification

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IPC-CM-770

Januaty

1996

4.1 Discrete Axial-Leaded Components

Discrete axial-

leaded devices are two-leaded board mounted components

that have the leads exiting from the ends of the component

along the axis of the components. They are considered suit-

able for automatic component insertion. The most common

axial-leaded devices are resistors, capacitors and diodes.

Detailed description of axial leaded components in con-

tained in Section

5.

4.2 Discrete Radial-Leaded Components

Discrete

radial-leaded devices are two-leaded board mounted com-

ponents that have all of the leads exiting from one side of

the component. Sometimes this side is on the perimeter of

the package and sometimes it is the bottom of the compo-

nent.

The body shapes vary from simple disc-shaped capacitors

to transistor-outline “TO” package high power transistors.

Details of radial-leaded components are contained in Sec-

tion 6.

4.3 Chip Components

Chip components comprise a

wide variety of two-terminal devices for surface mount

attachment. Some of the chip components have formed

metal leads for attachment but most are simple ceramic

devices with plated or solder dipped terminations that are

integral with the body of the component, chip components

are small and are designed and packaged for automatic

component handling. The details of chip components are

contained in Section 7.

4.4 Multileaded-Radial Components

Multileaded radial

components are assembled components that have all of the

leads exiting from one side of the component or from the

perimeter of the component base. Generally active semi-

conductor devices or arrays of two terminal devices can be

packaged in multileaded radial configurations. The details

of multileaded radial components are contained in Section

8.

4.5 Small Outline Components

Small outline compo-

nents (SOTS) are a family of three- or four-lead plastic

post-molded components intended for surface mount

attachment. Small outline integrated circuits (SolCs) com-

prise a family of multileaded surface mount components

that have two rows of formed leads on

5.08

mm centers.

Details of

“SO”

components are contained in Section

9.

4.6 ln-Line-Lead Components

This class of components

includes the traditional through board mounted components

that have the leads arrayed in one or more rows of formed

metal leads spaced on 2.54 mm centers. The body configu-

rations are variable but most of them are designed for

assembly with automatic machinery. The details of dual-

inline (DIP) and single-inline (SIP) packages are contained

in Section

10.

4.7 Multiple-Ribbon-Lead Components

Ribbon-leaded

components have flat wire ribbon leads that are arrayed

around the perimeter of the component. They are fre-

quently used to package high density integrated circuits

with special electrical requirements. Ribbon-leaded compo-

nent details are contained in Section

11.

4.8 Chip Carriers

Chip carriers are currently the most

common multileaded surface mount package. Their termi-

nations are arrayed around the perimeter of the rectangular

body and can be in the form of either formed metal leads

or pads that are integral to the body of the component. For

printed board mounting most chip carrier leads are located

on 1.27 mm centers but newer designs are considering

0.635 mm and smaller spacings between leads. The small

lead spacing and the large number of leads can require

special assembly procedures. Chip carrier package details

are contained in Section 12.

4.9 Pin Grid Arrays

Pin grid arrays form a class of very

high inputloutput (I/O) through board mount integrated cir-

cuit package. The leads are arranged in a solid area-filling

array across the bottom of the package, frequently with

space left free under the chip mount area. Details of pin

grid array packages are contained in Section 13.

4.1

O

Unpackaged Semiconductors

This type of compo-

nent includes all semiconductor devices that are not in indi-

vidual discrete packages. They may consist of individual

semiconductor dice that have termination bonding pads or

they may be semiconductor dice bonded to flexible sub-

strates, such as TAB, to aid in their handling and intercon-

nection. These components are used primarily with chip-

on-board technology as described in Section 14.

4.1 1 Connectors

Connectors form the means to inter-

connect between a printed board structure and another level

of interconnection with a separable connection. Connectors

between printed wiring boards and cables, backplanes and

special printed board structures are common. Frequently

connectors consist of a molded plastic housing that con-

tains formed metal contacts. Connectors can be either

through board or surface mount assembled. Connector

details are contained in Section

15.

4.12 Sockets

A socket is a form of connector used to

make separable contact between a printed board structure

and the terminations (leads) of a component. Sockets are

frequently assembled with the same technologies used for

components. Details of sockets are contained in Section 16.

4.1 3 Electromechanical and Interconnect Compo-

nents

Other board mounted components, such as pins,

wires, terminals, and mechanical hardware comprise a wide

set of parts that are assembled to printed wiring products to

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January

1996

IPC-CM-770

enhance the interconnection capabilities and to interface

with housings, supports, test equipment and other periph-

eral structures. The details of these special components are

contained in Sections

16,

17

and

18.

4.1 4 Packaging and Interconnecting (Printed Board)

Structures

Printed board structures include conventional

and modified organic printed boards, inorganic ceramic

printed boards, and supporting planekore structures.

Details concerning printed board structures are described in

Section

19.

4.1

5

TAB

Tape Automated Bonding (TAB) involves the

automated bonding of semiconductor devices (dies) to a

flexible lead frame in tape and reel format. The devices are

delivered to the assembly operation on tape where the indi-

vidual devices and part of the interconnecting lead frame

are excised, the leads formed and the devices directly

mounted to a printed board structure. TAB devices are fre-

quently encapsulated after mounting to the printed board

structure. Details are contained in Section

24.

4.16 Pad Grid Arrays

Pad Grid Arrays, also known as

Land Grid Arrays are surface mount packages where the

interconnections are distributed in an area array on the bot-

tom of the package. The interconnections are typically sol-

der columns connecting lands on the bottom of the pack-

age to a matching set of lands on a printed board structure

beneath it. Details of Pad Grid Arrays are contained in

Section

13.

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