IPC-D-279 EN.pdf - 第15页

IPC-279-02 Figure 1−2 Flow Chart for Reliability Assurance Processes ▼ ▼ ▼ ▼ ▼ ▼ ▼ ▼ ▼ ▼ ▼ ▼ ▼ ▼ ▼ ▼ ▼ ▼ ▼ ▼ ▼ ▼ ▼ ▼ ▼ ▼ ▼ ▼ Determine missing data. Is information complete enough for reliability analysis? Is reliability…

1.3.7 Testing Section 8.0 details the various testing

strategies, their purposes and their impact on reliability.

Also discussed are design for testability considerations.

Checklists for DfT from various sources are provided in

Appendix J.

1.4 Terms and Definitions Terms and deﬁnitions used

here are in accordance with IPC-T-50, and IPC-SM-785

except as otherwise speciﬁed.

IPC-279-01

Figure 1−1 General Design Steps

▼

1. Years of Service

2. Acceptable Failure Rate Limit

3. Repair/Replacement Strategy

Identify Reliability Reqts.

Levels:

•

Component

•

Assembly

Identify Life Environment

Phases:

•

Storage

•

Transportation

•

Processing

•

Testing

•

Operating

Temp. Range

•

Vibration/Shock

Identify Storage Env.

Transp. Env.

Proc.

ESD

•

Atmosphere

Analyze & Select

•

Components

•

Materials

•

Assembly Processes

•

Test Strategy

•

Thermal Mgt. Strategy

•

Solder Attachments

•

PWB Design

July 1996 IPC-D-279

IPC-279-02

Figure 1−2 Flow Chart for Reliability Assurance Processes

▼

Determine

missing

data.

information

complete enough

for reliability

analysis?

reliability in

Appendices

A, B & C

Estimate product

reliability

Appendices A, B & C

Redesign product.

Redefine

requirements.

estimated

reliability

adequate?

Finish

Solution:

Redesign

Redefine

Reduce

Uncertainties

Solution:

Redesign

Redefine

Review test

program for

correct-

ness

Finish

reliability

adequate

Collection of all

available inform-

ation & requirements

Flow Chart for Reliability Assurance Processes

Define proper

test, conditions,

IPC-SM-785

Accelerated

reliability

test(s)

Evaluate results

Failure Mode

Analysis

Estimate product

reliability from

test results

▼

Yes

Main Focus of Document

IPC-D-279 July 1996

2.0 APPLICABLE DOCUMENTS

The following documents of the issue in effect on the date

of issuance of this speciﬁcation, form a part of this speci-

ﬁcation to the extent speciﬁed herein. Subsequent issues of,

or amendments to, these documents may become a part of

this speciﬁcation.

2.1 Institute for Interconnecting and Packaging Elec-

tronic Circuits (IPC)

IPC-T-50 Terms and Deﬁnitions for Interconnecting and

Packaging Electronic Circuits

IPC-D-275 Design Standard for Rigid Printed Boards and

Rigid Printed Board Assemblies

IPC-TR-476 How to Prevent Electrically Induced Failures

(Electromigration) in Printed Wiring Board Assemblies

IPC-TM-650 Test Methods Manual

2.6.20 Assessment of Plastic Surface Mount Compo-

nents for Susceptibility to Moisture Induced Damage

IPC-ET-652 Guidelines and Requirements for Electrical

Testing of Unpopulated Printed Boards

IPC-PE-740 Troubleshooting guide for Printed Board

Manufacture and Assesmbly

IPC-SM-782 Surface Mount Design and Land Pattern

Standard

IPC-SM-785 Guidelines for Accelerated Surface Mount

Solder Attachment Reliability Testing

IPC-SM-786 Procedures for Characterizing and Handling

of Moisture/Reﬂow Sensitive ICs

IPC-SM-816 SMT Process Guideline and Checklist

2.2 Electronic Industries Association

EIA-541 Packaging Material Standards for ESD Sensitive

Items

EIA-583 Packaging Material Standards for Moisture Sen-

sitive Items

EIA-625 Requirements for Handling Electrostatic Dis-

charge Sensitive (ESD) Devices

JESD 22-A112 Moisture-Induced Stress Sensitivity for

Plastic Surface Mount Devices

JESD 22-A113 Preconditioning Procedures of Plastic Sur-

face Mount Devices Prior to Reliability Testing

JESD 42 Requirements for Handling Electrostatic-

Discharge Sensitive (ESDS) Devices

JEP113 Symbol and Labels for Moisture Sensitive

Devices

2.3 Joint Industry Standards

J-STD-001

Requirements for Soldered Electrical and Elec-

tronic Assemblies

J-STD-004 Requirements for Soldering Fluxes

3.0 DESIGN FOR RELIABILITY FOR SURFACE MOUNT

ASSEMBLIES

During the initial design stages of any project, a full

knowledge of the product requirements must be under-

stood. These requirements include the life cycle environ-

ment, printed board design constraints, thermal effects, ser-

viceability, and all aspects of reliability. This section

reviews these considerations and the effects caused by

each. The design details for DfR are discussed in Appendi-

ces A, B, and C.

3.1 Life Cycle Environment The environmental inﬂu-

ences that determine the reliability of surface mount assem-

blies have to include all environments from manufacture to

the end of the design life. These life cycle environments

include manufacturing processes, burn-in and/or ESS pro-

cedures, transport, storage and use conditions.

Depending upon the product application, any of the life

cycle environment periods may have an overwhelming

effect on the product reliability. The effects of all these life

cycle environment periods can accumulate and need to be

summed together using the Palmgren-Miner’s rule. (See

Equations #9 through #11 in Appendix A)

3.1.1 Manufacturing Processes Many manufacturing

processes used in Surface Mount Assembly require changes

in temperature. The most severe of these are processes

requiring the melting of solder. These processes can affect

PTH and PTVs, solder attachments, components and

printed boards. Other processes include bake-out of printed

boards, curing of adhesives, and curing of polymeric coat-

ings.

3.1.2 Processing Temperature Excursions During pro-

cessing and assembly of electronic assemblies, temperature

excursions, particularly during solder reﬂow and repair,

cleaning, or imposed thermal cyclic testing, take place that

are damaging to some parts of the assemblies and consume

part of the available life. These thermal excursions can

cause fractures in the PTVs of the multilayer printed board.

1. IPC, 2215 Sanders Road, Northbrook, IL 60062-6135.

2. Electronic Industries Association, 2001 Eye Street, N.W., Washington, DC 20006.

July 1996 IPC-D-279