IPC-CM-770D-1996 - 第29页

January 1996 IPC-CM-770 are used in the same assembly is rare to non-existent. Refer to general information related to class B/1 or B/2 assem- blies for consideration when leaded axial surface mount components are used w…

IPC-CM-770 Januaty

1996

CR1

R4 R3

+Cl

Not

Recommended

Sleeved component bridges more than one conductor.

IPC-1-00177

Figure

5-1

Horizontally Mounted Components

prevent damage to seals. Lead spacing should have

1.5

minimum forming allowances.

5.2.4.6 Rectangular Bodied Components

A component

with a rectangular body should be mounted

0.4

mm mini-

mum from the mounting base to enhance cleaning. When

required, assemblies with stringent conformal coating

requirements may need some type of board coating prior to

component mounting.

Recommended

Bridged conductors protected from moisture traps

by compatible insulating material.

IPC-1-00372

Figure

5-11

Components Mounted Over Conductors

Mounting

Hole

""""_

""_

""""_

R101

CR101

-+IlEl-

C"""""""1 C"""""""1 C"""""""1

Not recommended

Acceptable

1.5

Preferred

IPc-I-00020

Figure

5-1

2 Alignmentlboundaries

minimum of

0.4

mm clearance between the end of the

component body, which includes any packaging meniscus

and the surface of the board, to prevent potential heat dam-

age and entrapment problems. (See Figure

5-15.)

The maximum vertical misalignment shall be

15"

between

the body axis and a line perpendicular to the mounting sur-

face. Any bend in the lead should not fracture the case.

5.2.4.7 Mechanical Securing

Section

provides tech-

niques for component mounting that will prevent compo-

nent damage due to shock and vibration characteristics.

5.3

Surface Mounting

Axial-leaded components are pri-

marily suited for use in through-hole mounting technology.

However, when it is necessary to surface mount such com-

ponents, the guidelines of Section

22.1.2

should be fol-

lowed.

5.2.4.5 Hermetically Sealed Components

Hermetically

sealed components, such as reed relays, glass sealed

capacitors, and diodes, must be handled with caution to

5.4 Mixed Technology

Cases where both axial leaded

components with leads, through-hole and surface mount,

2-4

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January

1996

IPC-CM-770

are used in the same assembly is rare to non-existent. Refer

to general information related to class B/1 or

B/2

assem-

blies for consideration when leaded axial surface mount

components are used with chip components. When

through-hole axial components and chip components are

used in the same assembly, care must be taken to establish

proper assembly sequence, design for tool clearances and

shock resistance before soldering, cleaning, inspection/

testing, and rework.

5.5

Manual Assembly

Manual techniques for axial com-

ponents mounting are covered in Section 20.5 of this

guideline.

5.6 Automated Assembly

Automated techniques for

axial component mounting are covered in Section 20.6 of

this guideline. In addition, the following paragraphs repre-

sent additional considerations.

Multiple station sequencers and automatic variable center

distance (VCD) axial component insertion machines can be

utilized to perform high labor content kitting and compo-

nent preparation automatically for manual or operator

assisted component assembly. For this application, the cut

and clinch head of the VCD machine is removed and a

multiple cavity tray is placed in a modified board holder in

place of a printed board.

5.7

Handling and Storage

The handling and storage of

axial-leaded components should be in accordance with the

guidelines of Section 25.

5.10 Conformal Coating

General techniques for confor-

mal coating for all types of assemblies are described in

Section 28.

5.11 Quality Assurance

General quality assurance con-

siderations are described in Section 30.

6.0 RADIAL-LEADED DISCRETE COMPONENTS

Radial-leaded components come in a variety of shapes

from cylindrical, square, rectangular, wafer and kidney.

Leads exit from a common side of the component. The lead

is either ribbon or cylindrical. Selected devices can be

automatically inserted during assembly and also can be

modified with coined leads for surface mounting.

6.1 Part Type Description

Typical types of radial-lead

components are electrolytic, plastic, dipped, molded,

encapsulated capacitors, Figures 6-1, 6-2, 6-3, and transis-

tors, Figure 6-4.

6.1.1 Hermetically Sealed Components

Hermetically

sealed components such as electrolytic capacitors shall be

handled with caution to prevent damage to seals.

Bi-metallic welds should not be stressed.

6.1.2 Plastic Package Components

The integrity of the

interfacial adhesion between the plastic dip coating or

encapsulants to packaging or leads shall be maintained dur-

ing handling.

Washer or other mechanical hardware

1.5rnm

or more

Spacing less

(0.06

inches)

than

electrical

clearance

requirements

Not

Recommended

Spacing less than electrical

clearance requirements

Recommended

Spacing between printed wiring and mechancal hardware is 1.5rnm

(0.06")

IPC-I-O0030

Figure 5-1

Clearance

5.8 Soldering

General soldering techniques applying to

6.2 Through-Hole Mounting

all types of components are described in Section 26.

5.9 Cleaning

General techniques for cleaning applying

to all types of components are described in Section 27.

6.2.1 Component Preparation

Under certain circum-

stances, it may be advisable to provide stress relief for the

2-5

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IPC-CM-770

Januaty

1996

0.4

Not

Recommended Recommended

Component mounted flush to prlnted board. Component mounted wlth adequate clearance between end

NOTES:

The purpose of ralslng the component body off the

If the component

mounted tight to the board

(no

board surface is to facilitate solder flow, escape of

clearance) component movement will unduly Stress

gases in soldering and cleaning. Normally, this

the component lead.

accomplished only by raising the component

off

Conformal coating

application

and coverage may nec-

the board There are, however, certain hole

essitate

an increase

the

0.015’’

mlnlmum

dlmen-

support devices that can support the component

son.

and still accomplish solder flow, gas liberation,

Care should

taken when uslng spacers with

hlgh

and cleaning.

coefficlents of thermal expansion.

body and board; spacer may

used.

IPC-1-00145

Figure 5-1

Vertical Mounted Axial Lead Components

IPc-I-00040

Figure 6-1 Rectangular Radial Lead Capacitors

IPC-1-00155

Figure 6-2 Round Radial Lead Capacitor

leads of radial- lead components by forming the leads out-

ward from the normal component lead pattern to an

IPC-1-00149

Figure 6-3 Cast Radial Lead Capacitor

r”

IPC-1-00148

Figure 6-4 Radial-leaded “TO-3” Transistor Can

enlarged pattern to provide a degree of stress relief. (See

Figure

6-5.)

Another method of providing stress relief for

radial-lead components is the use of a flexible low-modulus

spacer supported by rounded protrusions.

2-6

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