IPC-SM-782A 表面安装设计和焊盘设计标准(带BGA).pdf - 第70页

3.2 Resistance to Cleaning Processes Parts must be capable of withstanding cleaning processes currently used by board assembly manufacturers. This may include as a mini- mum 4-minute exposures to solvent cleaning solutio…

1.0 INTRODUCTION

This section covers land patterns for various discrete compo-

nents. Each subsection contains information in accordance

with the following format:

1.0 Scope

2.0 Applicable Documents

3.0 General Component Description (Figure 1)

4.0 Component Dimensions (Figure 2)

5.0 Land Pattern Dimensions (Figure 3)

6.0 Tolerance and Solder Joint Analysis (Figure 4)

The following is the table of contents for this section:

Table of Contents

Rectangular Leadless Components

Section Component

8.1 Chip Resistors

8.2 Chip Capacitors

8.3 Inductors

8.4 Tantalum Capacitors

Circular Leadless Components

Section Component

8.5 MELF (Metal Electrode Face) Resistors and Diodes

Small Outline Transistors (SOT) and Diodes (SOD)

Section Component

8.6 SOT 23

8.7 SOT 89

8.8 SOD 123

8.9 SOT 143

8.10 SOT 223

Modiﬁed Through-Hole (TO) Packs

for Transistors and Diodes

Section Component

8.11 TO 252

2.0 APPLICABLE DOCUMENTS

The following documents, of the issue in effect on the revision

date of this section, form a part of this specification to the

extent specified herein.

2.1 Electronic Industries Association (EIA)

EIA-PDP-100

Registered and Standard Mechanical Outlines

for Electronic Parts

EIA-481-A

Taping of Surface Mount Components for Auto-

matic Placement

EIA-481-1

8 mm and 2 mm Taping of Surface Mount Com-

ponents for Automatic Handling

EIA-481-2

16 mm and 24 mm Embossed Carrier Taping of

Surface Mount Components for Automated Handling

EIA-481-3

32 mm, 44 mm, and 56 mm Embossed Carrier

Taping of Surface Mount Components for Automated Han-

dling

2.2 International Electrotechnical Commission (IEC)

IEC 97

Grid System for Printed Circuits

3.0 GENERAL INFORMATION

3.1 Packaging

Discrete components are generally pur-

chased in 8 mm and 12 mm wide tape and reel. See Figure

1. EIA-481 is the applicable specification for tape and reel.

Consult your manufacturers guide for the packaging availabil-

ity of your component.

Parts susceptible to damage by electrostatic discharge shall

be supplied in a manner that prevents such damage. Tape

peel strength shall be 40 ±30 grams. Peel from the top for the

top cover of the tape. Reel materials used in the construction

of the reel shall be easily disposable metal, chip board, sty-

rene plastic or equivalent. Reels shall not cause deterioration

of the components or their solderability. Reels must be able to

withstand high humidity conditions.

IPC-782-8-0-1

Figure 1 Packaging

Top cover tape

Sprocket hole

Component cavity

Embossed carrier tape

Sprocket hole

Embossed carrier tape

Component cavity

▼

IPC-SM-782

Surface Mount Design

and Land Pattern Standard

Date

8/93

Section

8.0

Revision Subject

Discrete Components

Page1of2

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3.2 Resistance to Cleaning Processes

Parts must be

capable of withstanding cleaning processes currently used by

board assembly manufacturers. This may include as a mini-

mum 4-minute exposures to solvent cleaning solutions at

40°C, plus a minimum of a 1-minute exposure to ultrasonic

immersion at a frequency of 40 kHz and a power of 100 watts

per square foot. Alkaline systems in use shall also not damage

parts or remove markings.

1. Application for copies should be addressed to EIA, 2001

Pennsylvania Ave N.W., Washington, DC, 20006-1813 or

Global Engineering Documents, 1990 M St. N.W., Wash-

ington, DC 20036.

2. Application for copies should be addressed to IEC, 3 rue

de Varembe, PO Box 131—1211 Geneva 20, Switzerland

IPC-SM-782

Subject

Discrete Components

Date

8/93

Section

8.0

Revision

Page2of2

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1.0 SCOPE

Microminiature leadless devices are available to the circuit

designer in rectangular form for discrete components such as

chip resistors.

This subsection provides the component and land pattern

dimensions for chip resistors, along with an analysis of toler-

ance and solder joint assumptions used to arrive at the land

pattern dimensions. Basic construction of the chip resistor is

also covered.

2.0 APPLICABLE DOCUMENTS

See Section 8.0 for documents applicable to the subsections.

3.0 COMPONENT DESCRIPTIONS

A variety of values exist for resistors. The following sections

describe the most common types.

3.1 Basic Construction

The resistive material is applied to

a ceramic substrate and terminated symmetrically at both

ends with a ‘‘wrap around’’ metal U-shaped band. The resis-

tive material is face-up, thus trimming to close tolerances is

possible. Since most equipment uses a vacuum-type pickup

head, it is important that the surface of the resistor is made flat

after trimming, otherwise vacuum pickup might be difficult.

See Figure 1.

3.1.1 Termination Materials

End terminations should be

solder coated with a tin/lead alloy. The solder should contain

between 58 to 68% tin. Solder may be applied to the termi-

nation by hot dipping or by plating from solution. Plated sol-

der terminations should be subjected to a post-plating reflow

operation to fuse the solder. The tin/lead finish should be at

least 0.0075 mm [0.0003 in.] thick.

The termination shall be symmetrical, and shall not have nod-

ules lumps, protrusions, etc., that compromise the symmetry

or dimensional tolerances of the part. The end termination

shall cover the ends of the components, and shall extend out

to the top and bottom of the component.

Solder finish applied over precious metal electrodes shall have

a diffusion-barrier layer between the electrode metalization

and the solder finish. The barrier layer should be nickel or an

equivalent diffusion barrier, and should be at least 0.00125

mm [0.00005 in] thick.

3.1.2 Marking

Resistors equal to or larger than 2012

[0805] are labeled. Resistors smaller than 1608 [0603] are

generally unlabeled.

3.1.3 Carrier Package Format

Bulk rods, 8 mm tape/4

mm pitch is preferred for best handling. Tape and reel speci-

fications provide additional requirements.

3.1.4 Resistance to Soldering

Parts should be capable of

withstanding five cycles through a standard reflow system

operating at 215°C. Each cycle shall consist of 60 seconds

exposure at 215°C. Parts must also be capable of withstand-

ing a minimum of 10 seconds immersion in molten solder at

260°C.

IPC-782-8-1-1

Figure 1 Chip resistor construction

Resistor

Alumina Chip

Platinum-silver

Wrap-around

termination

Wire Bond Construction

Glass

Passivation

IPC-SM-782

Surface Mount Design

and Land Pattern Standard

Date

5/96

Section

8.1

Revision

Subject

Chip Resistors

Page1of4

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