ASSOCIATION CONNECTING
ELECTRONICS INDUSTRIES ®
IPC/JEDEC-9702
Monotonic Bend Characterization
of Board-Level Interconnects
IPC/JEDEC-9702
June 2004
A standard developed by IPC and JEDEC
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Fax 703.907.7583
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IPC/JEDEC-9702
ASSOCIATION CONNECTING
ELECTRONICS INDUSTRIES ®
Monotonic Bend
Characterization
of Board-Level
Interconnects
Developed by the SMT Attachment Reliability Test Methods Task Group
(6-10d) of the Product Reliability Committee (6-10) of IPC and the
JEDEC Reliability Test Methods for Packaged Devices Committee
(JC-14.1)
Users of this publication are encouraged to participate in the
development of future revisions.
Contact:
IPC
2215 Sanders Road
Northbrook, Illinois
60062-6135
Tel 847 509.9700
Fax 847 509.9798
JEDEC
Solid State Technology Association
2500 Wilson Boulevard
Arlington, VA 22201-3834
Tel 703 907.7559
Fax 703 907.7583
This Page Intentionally Left Blank
June 2004
IPC/JEDEC-9702
Acknowledgment
Members of the JEDEC Reliability Test Methods for Packaged Devices Committee (JC-14.1) and the SMT Attachment
Reliability Test Methods Task Group (6-10d) of the Product Reliability Committee (6-10) have worked together to develop
this document. We would like to thank them for their dedication to this effort. Any document involving a complex technology draws material from a vast number of sources. While the principal members of the SMT Attachment Reliability Test
Methods Task Group are shown below, it is not possible to include all of those who assisted in the evolution of this standard. To each of them, the members of the JEDEC and IPC extend their gratitude.
Product Reliability
Committee
JEDEC Reliability Test Methods
for Packaged Devices Committee
Chair
Reza Ghaffarian, Ph.D.
Jet Propulsion Laboratory
Chair
Jack McCullen
Intel Corporation
SMT Attachment Reliability
Test Methods Task Group
Chair
Reza Ghaffarian, Ph.D.
Jet Propulsion Laboratory
Vice-Chair
Werner Engelmaier
Engelmaier Associates, L.C.
Technical Liaisons of the
IPC Board of Directors
Peter Bigelow
IMI Inc.
Sammy Yi
Flextronics International
SMT Attachment Reliability Test Methods Task Group
Mudasir Ahmad, Cisco Systems, Inc.
Denis Gignac, Nortel Networks
Patricia J. Amick, Boeing Aircraft &
Missiles
Lavanya Gopalakrishnan, Ciena
Corporation
Pierre Audette, Nortel Networks
Jean Bobgan, Guidant Corporation
Michael R. Green, Lockheed Martin
Space Systems Company
Dr. John Kirk Bonner, Jet Propulsion
Laboratory
Samy Hanna, AT&S Austria
Technologie & Systemtechnik
Mark Brillhart, Cisco Systems Inc.
Hana Hsu, Mitac International
Corporation
Nicole Butel, Agilent Technologies
Srinivas Chada, Ph.D., Jabil Circuit,
Inc.
Phillip Chen, Northrop Grumman
Canada Corporation
Beverley Christian, Ph.D., Research
In Motion Limited
Thomas Clifford, Lockheed Martin
Space Systems Company
Yves Desrochers, Nortel Networks
Howard S. Feldmesser, Johns
Hopkins University
Jean-Yves Gagne, Nortel Networks
Mahendra S. Gandhi, Northrop
Grumman
Phil Geng, Intel Corporation
Kim Hyland, Solectron Corp.
Thomas E. Kemp, Rockwell Collins
Vincent B. Kinol, Umicore America
Inc.
Gregg Klawson, General Dynamics C4 Systems
Dennis Krizman, Celestica
Kuan-Shaur Lei, Hewlett-Packard
Company
James F. Maguire, Intel Corporation
Wesley R. Malewicz, Draeger
Medical Systems, Inc.
John Manock, Lucent Technologies,
Inc.
Susan S. Mansilla, Robisan
Laboratory Inc.
Lei L. Mercado, Ph.D., P.E., Intel
Corporation
Frank Mortan, Texas Instruments
Keith G. Newman, Sun Microsystems
Inc.
Bob Ogden, Raytheon Systems
Company
Deepak K. Pai, C.I.D.+, General
Dynamics-Advanced Information
Mel Parrish, Soldering Technology
International
Kumar Pavuluri, Texas Instruments
Inc.
Mike Pfeifer, Motorola Inc.
Sundar Sethuraman, Solectron
Corporation
Rocky Shih, Hewlett-Packard
Company
Vern Solberg, Tessera Technologies,
Inc.
Vish Sundararaman, Ph.D., Texas
Instruments Inc.
Vasu S. Vasudevan, Intel Corporation
Dewey Whittaker, Honeywell Inc.
Greg Wood, ACI/EMPF
iii
IPC/JEDEC-9702
June 2004
Table of Contents
1
FOREWORD ............................................................. 1
ANNEX A
...................................................................... 9
2
INTRODUCTION ....................................................... 1
ANNEX B
.................................................................... 12
3
SCOPE ...................................................................... 1
4
TERMS AND DEFINITIONS ..................................... 1
5
SYMBOLS AND ABBREVIATED TERMS ............... 2
6
SAMPLING ................................................................ 2
7
APPARATUS ............................................................. 2
Figures
Figure 7-1
Universal Tester .................................................. 2
Figure 8-1
Test Board Layout ............................................... 4
Figure 8-2
Rectangular Package Orientation ....................... 5
Figure 8-3
Single Package Daisy-Chain Configuration
(Example) ............................................................ 5
Figure 8-4
Strain Gage Placement ....................................... 7
7.1
7.2
Universal Tester ....................................................... 2
Strain Measurement Equipment .............................. 3
Figure 9-1
Interconnect Fracture Modes (Solder
Ball Array Devices) .............................................. 8
7.3
Continuity Monitoring Equipment .......................... 3
Figure A.1
Example Configuration (PWB Thickness
= 1.00 mm) .......................................................... 9
PROCEDURE ............................................................ 3
Figure A.2
Example Configuration (PWB Thickness
= 1.55 mm) ........................................................ 10
Figure A.3
Example Configuration (PWB Thickness
= 2.35 mm) ........................................................ 11
8
8.1
8.2
8.3
8.4
Component Sample .................................................
Test Board Material .................................................
Test Board Thickness and Metal Layer Count .......
Test Board Surface Finish .......................................
3
3
3
4
8.5
8.6
8.7
Test Board Land Pads ............................................. 4
Test Board Layout ................................................... 4
Test Board Daisy-Chain Links ................................ 4
8.8
8.9
8.10
8.11
Board Assembly ......................................................
Storage .....................................................................
Strain Gages ............................................................
Set-Up Test Board ...................................................
6
6
6
6
Tables
Table 7-1
Universal Tester Requirements ............................ 2
Table 8-1
Recommended Test
Board Thickness & Layer Count .......................... 3
Table 8-2
Test Board Layout Requirements ......................... 4
Table 8-3
Monotonic Bend Test Requirements .................... 7
Table B.1
Test Report Recommendations
(Equipment & Materials) ..................................... 12
Table B.2
Test Report Recommendations
(Board Assembly) ............................................... 12
Table B.3
Test Report Recommendations
(Test Results) ..................................................... 12
8.12 Four-Point Bend Test .............................................. 6
9
iv
FAILURE CRITERIA AND ANALYSIS ..................... 7
June 2004
IPC/JEDEC-9702
Monotonic Bend Characterization
of Board-Level Interconnects
1 FOREWORD
Strain:
This publication on monotonic bend testing is intended to
characterize the fracture strength of a component’s boardlevel interconnects. The document is applicable to surface
mount components attached to printed wiring boards using
conventional solder reflow technologies. The monotonic
bend characterization results provide a measure of fracture
resistance to flexural loading that may occur during conventional non-cyclic board assembly and test operations,
and supplements existing standards that address mechanical shock or impact during shipping, handling or field
operation.
length)
Dimensionless unit, (change in length) ÷ (original
Change in strain divided by the time interval
during which this change is measured
Strain-Rate:
Planar copper foil pattern that is adhered to
an underlying surface and exhibits a change in resistance
when subjected to a strain
Strain Gage:
Strain Gage Element: Sensing area of strain gage defined
by the serpentine copper grid pattern
Uniaxial Strain Gage: Strain gage incorporating a single
strain gage element, i.e., capable of detecting strain along a
single axis
2 INTRODUCTION
Semiconductor devices are assembled in a variety of package configurations, and are used in a multitude of applications. Given the diversity of package constructions and
end-use conditions, it is not feasible to establish a single
qualification requirement relating to bend testing; however,
definition of a uniform test methodology and a standard
reliability characterization reporting process are increasingly necessary to ensure adequate product quality.
3 SCOPE
This publication specifies a common method of establishing the fracture resistance of board-level device interconnects to flexural loading during non-cyclic board assembly
and test operations. Monotonic bend test qualification pass/
fail requirements are typically specific to each device application and are outside the scope of this document.
For the purposes of this standard, the selected terms and
definitions listed below apply.
General Terms
Packaged semiconductor device
Conductive element used for electrical
interconnection, e.g., solder ball, lead, etc.
Interconnect:
Monotonic Test:
Non-reversing, test to fail
Strain Related Terms
Global PWB Strain: Four-point bending strain of uniform
printed wiring board, ignoring any effects due to the package(s)
6
Dimensionless unit, 10 x (change in length)
÷ (original length)
Microstrain:
Four-point assembly fixture support with a rounded
contact surface
Anvil:
Crosshead Assembly: Clamping/attachment assembly of
universal tester that moves relative to the base of the test
equipment, and creates the forces necessary for specimen
testing
Four-Point Bending Fixture: Test assembly that supports a
specimen on two anvils or rollers, and symmetrically loads
the specimen on the opposite surface with two anvils or
rollers
Load Span: Distance between the two anvils or rollers
that load the test specimen
Roller: Four-point assembly fixture support that incorporates a cylindrical bar as the contact surface
Distance between the two anvils or rollers
that support the test specimen
Support Span:
4 TERMS AND DEFINITIONS
Component:
Mechanical Test Equipment Terms
Test equipment capable of tensile/
compressive loading using controlled linear motion of a
crosshead assembly
Universal Tester:
Electrical Test Terms
Daisy-Chain: A conductive link that can be connected in
series with other conductive links (like a chain of daisies)
to form a continuous electrical net
In-Situ Measurement: Measurement conducted during a
test, i.e., in place, rather than during an interruption of the
test condition
Failure Analysis Term
Dye exposure of package/board assembly
followed by mechanical removal of the package
Dye-and-Pry:
1
IPC/JEDEC-9702
June 2004
5 SYMBOLS AND ABBREVIATED TERMS
Unit
board thickness
crosshead travel distance
crosshead speed
degree Celsius
degree Fahrenheit
Hertz
load span
microstrain
second (time)
strain
strain-rate
support span
Symbol
t
δ
δ̇
°C
°F
Hz
LL
µε or µStrain
s
ε
ε̇
LS
Term
ball grid array
chip scale (size) package
intermetallic compound
organic solderability preservative
printed wiring board
surface mount
small outline package
Abbreviation
BGA
CSP
IMC
OSP
PWB
SMT
SOP
6 SAMPLING
A statistically relevant sample size is required. It is recommended that several manufacturing lots be sampled to
evaluate lot-to-lot variability. Depending on failure distribution, desired sensitivity, confidence limits, etc., sample
quantities such as 23, 30, 45, etc., may be appropriate.
7 APPARATUS
7.1 Universal Tester A universal tensile tester incorporating a deflection measuring device shall be used to generate a controlled board deflection rate. The tester shall
include a four-point bending fixture (see Figure 7-1) to
apply a theoretically uniform bending moment across the
load span.
Table 7-1 lists dimensional and operational requirements
for the universal tester.
Table 7-1
Universal Tester Requirements
Description
Requirement
Anvil/roller radius
3 mm
[0.12 in.], min.
Anvil/roller length
> board width
Ambient temperature
23 °C ± 2 °C
[73 °F ± 4 °F]
Non-standardized bend test methods in practice today often
specify an applied load, span and/or crosshead travel distance to characterize mechanical resistance to failure of
board-level device interconnects. Unfortunately, these
parameters are not readily transferable to differing board
thicknesses, package configurations or board layouts. The
dimensionless unit of strain, ε, however, can be applied
more broadly to differing board/package geometries and
relates more directly to analytical and computational failure
models.
IPC/JEDEC-9702-7-1
Figure 7-1
2
Universal Tester
June 2004
IPC/JEDEC-9702
The crosshead travel distance (δ) and crosshead speed (δ̇)
of a universal tester are approximately proportional to the
test board assembly strain (ε) and strain-rate (ε̇), respectively. The relationship between these variables can be
determined empirically by testing a mechanically representative package/board assembly (set-up test board); however, these relationships may prove non-constant or nondeterminant, depending on universal tester capability and
board/ package configuration.
This test method specifies use of the following simplified
analytical relationships (see Equations 1 & 2) to establish
the universal tester control settings for crosshead travel
distance and crosshead speed, based upon global PWB
strain and strain-rate input variables, respectively. These
equations are derived from classic beam theory and ignore
any effects due to the package(s), or to the Poisson’s ratio
effect of a plate in bending.
Equation 1
δ=
ε (LS − LL) (LS + 2LL)
6t
where
δ
ε
LS
LL
t
=
=
=
=
=
crosshead travel distance
global PWB strain
support span
load span (centered within support span)
PWB thickness
Equation 2
δ̇ =
ε˙ (LS − LL) (LS + 2LL)
6t
where
δ̇
ε̇
LS
LL
t
=
=
=
=
=
crosshead speed
global PWB strain-rate
support span
load span (centered within support span)
PWB thickness
7.2 Strain Measurement Equipment A strain measurement equipment scan frequency of 500 Hz (min.), and a
data signal resolution of 16 bits (min.) are preferred for the
short duration (<5 seconds, typ.) monotonic bend test.
Continuity monitoring is preferably performed by the same high scan frequency equipment used for strain measurements, allowing
simultaneous recording of net resistance and strain.
examples. Discrete SMT devices, e.g., capacitors, resistors,
etc., are outside the scope of this test method. The test
component must contain daisy-chain connections to allow
in-situ continuity monitoring of the device board-level
interconnects during the bend test. It is likely that the same
daisy-chain package construction may be used for both
bend testing and thermal cycle testing. For bend testing of
array-based packages; however, only the outermost package daisy-chain links need to be connected to a corresponding PWB daisy-chain link and electrically monitored.
The daisy-chain package materials, dimensions, and construction must be representative of a typical production
device. The layout of solder balls or leads for the daisychain package should represent a typical leadcount configuration expected for a production device of that package
body size. As indicated previously, the monitored daisychain links on the package consist of the outer component
interconnects. Each package daisy-chain link should consist of a pair of adjacent solder joints or leads.
Functional devices may be used in lieu of a daisy-chain
package if the electrical continuity monitoring requirements defined in this publication can be met.
8.2 Test Board Material The test board material should
match the composition of the actual end-use PWB, typically FR4 epoxy/glass laminate.
8.3 Test Board Thickness and Metal Layer Count The
test board thickness and metal layer count should match the
actual end-use PWB. Definition of a ‘‘typical’’ printed wiring board is problematic given the expanding usage of
alternative board constructions and materials, and the widening form-factor gap between handheld electronic devices
and other application types. Table 8-1 provides a minimum
recommended test board thickness and metal layer count if
the device will be used in a variety of end-use applications,
or if the actual PWB configuration is unknown. Finite element modelling suggests that the ratio between package/
solder interfacial strain and global PWB strain increases
with increased board thickness and copper layer count.
Consequently, use of a thicker test board or higher metal
layer count than listed in Table 8-1 will typically lead to
more conservative bend test results.
Table 8-1 Recommended Test
Board Thickness & Layer Count
7.3 Continuity Monitoring Equipment
Copper
Layers,
min.
Max. Package Body
Dimension, X (mm) [in.]
PWB Thickness,
min. (mm) [in.]
Small: X ≤15 [0.59]
1.00
[0.039]
4
8 PROCEDURE
Medium: 15 [0.59]
< X <40 [1.58]
1.55
[0.062]
6
8.1 Component Sample This standard assumes a surface
Large: X ≥40 [1.58]
2.35
[0.093]
8
mount device; BGA, SOP and CSP are typical device
3
IPC/JEDEC-9702
The test board surface
finish should match the actual end-use PWB surface finish.
If the device will be used in a variety of applications, multiple surface finishes may need to be evaluated.
8.4 Test Board Surface Finish
8.5 Test Board Land Pads The test board land pads
should match the configuration of the actual end-use PWB,
typically non-solder mask defined (NSMD). If the end-use
configuration is unknown, NSMD land pads should be used
with exposed PWB land pad diameters that are 80-100% of
the package solder-wetted pad diameters.
Finite element simulations support the testing of multiple packages on a test board (see
Figure 8-1) given the specific test board layout requirements detailed in Table 8-2; however, variations in PWB
and solder strain are typically greater for test boards with
multiple components.
8.6 Test Board Layout
The lengthwise direction of rectangular packages should be
aligned with the longitudinal direction of the test board as
illustrated in Figure 8-2.
8.7 Test Board Daisy-Chain Links The combination of
daisy-chain links on the package and those on the test
board should result in completed daisy-chain nets after
board assembly. 100% daisy-chain coverage of the outer
package interconnects parallel to the anvils/rollers is
required, but the coverage may extend to the entire package interconnect footprint. Each package must have at least
June 2004
Table 8-2
Test Board Layout Requirements
Description
Requirement
Package quantity
per board
15 (3 row x 5 col.), max. - small* pkg
4 (2 row x 2 col), max. - medium* pkg
4 (2 row x 2 col), max. - large* pkg *
Note: see Table 8-1 for package body
size classifications
Distribution
Package sites must be uniformly
distributed
Symmetry
Package sites must be symmetrical
about both mid-span axis and PWB
longitudinal centerline
Package-topackage separation
(x-y directions)
5 mm [0.20 in.], min. (package edge
to package edge)
Package-to-anvil
separation
10 mm [0.39 in.], min. (package edge
to inner anvil/roller centerline)
Package-to-board
separation
8 mm [0.32 in.], min. (outermost
package edge to board edge)
Package orientation
Package orthogonal to PWB &
four-point bend fixture
Connector location
Outside support span anvils/rollers,
including when PWB is bent in its
max. condition
a single separately monitored daisy-chain net. See Figure
8-3 for an illustration of a test board daisy-chain configuration (single package).
Test boards using functional devices may require a modified configuration to satisfy the electrical continuity monitoring requirements.
IPC/JEDEC-9702-8-1
Figure 8-1
4
Test Board Layout
June 2004
IPC/JEDEC-9702
IPC/JEDEC-9702-8-2
Figure 8-2
Rectangular Package Orientation
IPC/JEDEC-9702-8-3
Figure 8-3
Single Package Daisy-Chain Configuration (Example)
5
IPC/JEDEC-9702
For array-based SMT packages, the solder connections at
the package corner typically fail sooner during monotonic
bend testing than the connections on the middle of the
package edge. Consequently, separate daisy-chain nets for
the package corners are recommended. Finite element
analysis indicates that the package/solder interfacial strain
at the package corner is most severe for the largest package body sizes, and for the largest array of test packages on
a single test board.
Electrical monitoring traces should be routed on internal
PWB layers to reduce the likelihood of external trace contact damage during testing. Further, test board vias connecting internal electrical monitoring traces may fail prior
to the monitored package interconnections. Consequently,
it is recommended that any circuitry associated with continuity monitoring have redundant trace and via routing
wherever possible. Outer layer traces required by PWB
routing constraints should avoid anticipated strain gage
locations.
Probe pads are recommended for each component daisychain link, wherever possible, to facilitate fault isolation
and failure analysis.
8.8 Board Assembly The solder paste printing process
and thermal reflow profile should be optimized prior to
mass reflow or rework assembly of the test boards. Optimization of solder paste volume and paste registration typically requires evaluation of printing speed, squeegee pressure, stencil separation speed, stencil thickness, stencil
aperture geometries, etc. Similarily, optimization of solder
wetting, solder ball/fillet shape and solder surface finish
often involves evaluation of preheat temperature, peak
solder/package/board temperatures, duration above solder
liquidus temperature, cooling/heating ramp rates, etc.
8.9 Storage The measured fracture resistance of the
board-level interconnects can be affected by storage conditions (temperature, humidity, atmosphere) and storage
duration of the package/PWB assemblies prior to bend testing. A recommended duration between board assembly and
bend test is eight hours, minimum, and 168 hours, maximum.
8.10 Strain Gages For the test configuration defined in
this standard, finite element modelling indicates that the
PWB principal strain angle is essentially coincident with
the longitudinal board axis at all board locations. Therefore, the use of uniaxial strain gages for monitoring board
strain and strain-rate is acceptable. A nominal strain gage
element size of 1.5 mm x 1.5 mm [0.059 in. x 0.059 in.] is
recommended.
The sensing direction of the uniaxial strain gage must be
aligned with the longitudinal board direction. For test configurations meeting the specific requirements of this test
6
June 2004
method, analysis indicates that the PWB strain values are
generally uniform from one package location to another,
allowing for the requirement of only three strain gages per
test board (see Figure 8-4). Additional strain gages at the
opposite PWB diagonal can be used to verify symmetrical
loading.
Although PWB strain measurements from any single location in Figure 8-4 may prove more relevant to a particular
end-use PWB assembly condition or application, all three
strain gage locations relate to package interconnect strain
and fracture resistance. Cumulatively, the PWB strain readings at these locations provide enhanced characterization of
a device’s interconnect fracture resistance. Measurements
using the strain gage mounted on the top of the test board
as shown in Figure 8-4 approximate global PWB strain.
PWB strain readings using the gage placed at the package
center as shown in Figure 8-4 approximate minimum PWB
strain and help quantify the localized stiffening effect of the
test package. Finally, measurements using the strain gage
coincident with the cornermost solder joint, or lead,
approximate maximum PWB strain.
The strain gages should be mounted to the test board using
materials and procedures specified by the gage manufacturer, e.g., surface preparation, adhesive application, gage
attachment, adhesive cure, leadwire attachment, etc.
Although it is not preferred practice, strain gages may not
be necessary on every test board if a documented database
of past test results (using near-identical configurations) has
established minimal statistical strain variation between one
test board assembly and another, and the crosshead travel
distance at interconnect failure can be accurately recorded.
8.11 Set-Up Test Board A set-up test board is recommended for verification of test parameter settings. Strain
gage monitoring of the set-up board beyond the minimal
requirements shown in Figure 8-4 is recommended to provide more complete characterization of the PWB strain distribution.
8.12 Four-Point Bend Test The test assembly should be
oriented as shown in Figure 7-1 such that the component
leads or solder joints are placed in tension during the fourpoint bend test. Empirical testing, supported by finite element analysis, indicates that board-level package solder
connections are typically more susceptible to fracture with
increased strain-rate (at comparable PWB strain levels).
Testing conducted at crosshead speeds less than specified
in Table 8-3 will tend to overstate fracture strength of a
component’s board-level interconnects; hence, test equipment and test board configurations should be selected that
meet the minimum crosshead speed shown below, wherever possible, to insure consistent, conservative reporting
of interconnect strength.
A PWB pre-load is specified to ‘‘seat’’ the test board
against all four anvils/rollers prior to start of the test. The
June 2004
IPC/JEDEC-9702
IPC/JEDEC-9702-8-4
Figure 8-4
Strain Gage Placement
Table 8-3
Monotonic Bend Test Requirements
Parameter
Value
PWB pre-load, ε
100 µStrain, max.*
* Note: pre-load is measured using
strain gage mounted on the top of
the test board as specified in Figure
8-4
Minimum crosshead
speed, δ̇
Calculated value (see Equation 2),
using nominal global PWB
strain-rate, ε̇, of 5,000 µStrain/s
Maximum crosshead
travel distance, δ
Electrical failure of all daisy-chain
nets
actual monotonic bend test occurs at a constant crosshead
speed corresponding to the nominal global PWB strain rate
value specified in Table 8-3, terminating when all of the
monitored daisy-chain nets have electrically failed.
Although it should be avoided wherever possible, equipment and test configuration limitations may sometimes
results in test termination before failure.
Annex A provides example universal tester configurations
that satisfy the four-point bend test requirements of Table
8-3, using the crosshead speed as calculated by Equation 2,
and the PWB test board thicknesses referenced in Table
8-1.
Strain gage readings should be calibrated and set to zero in
the initial undeflected condition, prior to the specified preload. The test board strain gages should be continuously
monitored at a recommended scan frequency of no less
than 500 Hz, and recorded during the entire board deflection procedure.
Depending on board configuration and warpage, the preload level shown in Table 8-3 may not always result in
proper seating of the PWB against the anvils/rollers. The
test board assembly should be returned to an unloaded condition immediately upon conclusion of the test.
In-situ monitoring of the daisy-chain nets is preferably conducted using the same equipment used to measure strain,
with strain and net resistance recorded simultaneously.
9 FAILURE CRITERIA AND ANALYSIS
A recommended definition of electrical failure is a 20%
increase in daisy-chain net resistance; however, a lower or
higher threshold may be more appropriate, depending upon
test equipment capability and specific daisy-chain design
scheme.
The clear goal of failure analysis is the ability to detect the
location, mode and mechanism for the observed electrical
failure. Failure analysis should verify that detected failures
or resistance increases are not due to associated cabling,
connectors, testboard or test apparatus. For bend tests
stopped without electrical failure, failure analysis should be
performed to insure that failures were not missed due to
errors in daisy-chain design or test hardware.
Non-destructive failure analysis tools that may be used
include x-ray, coupled scanning acoustic microscopy
(CSAM), and side view optical microscopy. Common
methods and tools during destructive failure analysis
include cross section, dye-and-pry, x-ray, CSAM, scanning
7
IPC/JEDEC-9702
electron microscope (SEM) and energy dispersive x-ray
(EDX).
The mechanical failure mode(s) of each component should
be identified. Each observed failure mode shall be documented using cross-section (or other suitable analysis tech-
June 2004
nique) of one representative solder joint or lead, at a minmum. Example failure modes for solder ball array style
packages are illustrated in Figure 9-1. Failure modes for
leaded style packages include lead cracking, package body
cracking, and cracking between the various lead, IMC, solder and PWB metal pad interfaces.
IPC/JEDEC-9702-9-1
Figure 9-1
8
Interconnect Fracture Modes (Solder Ball Array Devices)
June 2004
IPC/JEDEC-9702
ANNEX A (Informative) - Example Universal Tester Configurations
This annex provides example universal tester configurations that satisfy the four-point bend test requirements of Table 8-3,
using Equation 2. The example configurations shown in Figures A.1 - A.3 represent a non-exhaustive summary of the possible options that satisfy this guideline’s requirements.
IPC/JEDEC-9702-a1
Figure A.1
Example Configuration (PWB Thickness = 1.00 mm)
9
IPC/JEDEC-9702
June 2004
IPC/JEDEC-9702-a2
Figure A.2
10
Example Configuration (PWB Thickness = 1.55 mm)
June 2004
IPC/JEDEC-9702
IPC/JEDEC-9702-a3
Figure A.3
Example Configuration (PWB Thickness = 2.35 mm)
11
IPC/JEDEC-9702
June 2004
ANNEX B (Informative) Test Report Recommendations
A test report including comprehensive documentation of the bend test is recommended (see Tables B.1 - B.3). Disclosure of
the test report contents will depend on specific customer/supplier agreements.
Table B.1
Test Report Recommendations (Equipment & Materials)
Category
Description
Equipment
Manufacturer, model number and operational conditions for the following:
• universal tester
• strain measurement equipment
• continuity monitoring equipment
Four-point bend
test fixture
• load span
• support span
• anvil/roller radius
• anvil/roller length
Component
• package outline drawing or reference to JEDEC outline
• die dimensions (width, length and thickness) and orientation (rectangular die)
• daisy-chain connection map and/or net list
• measured solder ball or lead coplanarity
• solder ball shear values or lead pull strength, and associated failure modes (parts from same production lot
as tested devices)
• solder-wetted pad dimensions, if applicable
• solder ball land pad type, if applicable (solder mask defined, etc.)
• lead finish/pad metallization, including thicknesses of all layers and composition of solder, if applicable
Test board
• width, length and thickness
• dielectric material
• surface finish
• external trace, pad and solder resist opening dimensions
• measured board coplanarity
Strain gage
• manufacturer and part number
• resistance
• strain gage element size
Table B.2
Test Report Recommendations (Board Assembly)
Category
Board assembly
Description
• preheat temperature, ramp rate, critical peak temperatures (solder, package surface, board, etc.) duration
above solder liquidus temperature and cooling rate
• solder composition
• solder paste metal percentage, particle mesh size type and flux type
• reflow atmosphere
• nominal solder paste volume
• nominal solder joint geometry
• component/PWB storage and/or bake-out conditions prior to board assembly
• storage conditions and duration following board assembly
Table B.3
Test Report Recommendations (Test Results)
Category
Description
Set-up data
• strain rate vs. crosshead speed*
• strain vs. crosshead travel distance*
• force vs. crosshead travel distance
Strain data (each
test board)
• strain vs. time*
• strain-rate vs. time*
• strain vs. strain-rate*
• force vs. time
Resistance data
(each test board)
• resistance vs. time
Failure distribution
• cumulative failure percentage vs. strain (2-parameter Weibull )
Failure mode
• failure mode histogram (all test packages)
• time-zero cross-section of a single pkg/board test assembly
• failure analysis of representative sample of each observed failure mode
* Note: Measurements at each strain gage location should be reported.
12
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Standard Improvement Form
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Technical Committee of IPC with input
from the industry regarding usage of
the subject standard.
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submit comments to IPC. All comments
will be collected and dispersed to the
appropriate committee(s).
IPC/JEDEC-9702
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