Transcript LEAD-FREE AND MIXED ASSEMBLY SOLDER JOINT RELIABILITY TRENDS by Jean-Paul Clech, EPSI Inc. Montclair, NJ, USA Tel: +1 (973)746-3796, fax: +1 (973)655-0815 E-mail: [email protected], URL: http://jpclech.com Presented.

LEAD-FREE AND MIXED ASSEMBLY
SOLDER JOINT RELIABILITY
TRENDS
by Jean-Paul Clech, EPSI Inc.
Montclair, NJ, USA
Tel: +1 (973)746-3796, fax: +1 (973)655-0815
E-mail: [email protected], URL: http://jpclech.com
Presented at
IPC / SMEMA Council APEX Conference
Anaheim, CA, February 26, 2004
Clech, APEX 2004 - Copyright © EPSI Inc., 2004
1
Introduction


Objective: Compare lead-free vs. SnPb solder joint
reliability over a wide range of circumstances
 Preliminary study limited to thermal cycling data
Where are we on the learning curve?
METRIC
SNPB RELIABILITY
SAC RELIABILITY
1. AUTHOR’S REFERENCE ~ 2500 PUBLICATIONS ~ 250 PUBLICATIONS
LIST
2. YEARS OF INDUSTRY ~ 50 YEARS
~ 12 YEARS
EXPERIENCE
Clech, APEX 2004 - Copyright © EPSI Inc., 2004
RATIO
(“SAC” COLUMN /
“SNPB” COLUMN)
10%
24%
2
SAC Test Data
1.E+05
3.5 X
Resistors
CBGAs
LCCC
PBGA
CSP
1.E+04
27 data points (100% SAC)
0.7
1
3.5 X
1.E+03
1%
CHARACTERISTIC LIFE:
component
(cycles)
Thermal
Conditions:
0/100C
-40/125C
-55/125C
1.E+02
1.E-03
1.E-02
1.E-01
1.E+00
CYCLIC SHEAR STRAIN RANGE

Coffin-Manson approach:


Not much data for Dg < 1%
Correlation coefficient: R2 ~ 0.6
Clech, APEX 2004 - Copyright © EPSI Inc., 2004
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First Order Correlation of SAC Test Data
Thermal
Conditions:
0/100C,
-40/125C
-55/125C
2X
1.E+08
CSP
PBGA
CBGA
RES. 0603
RES. 1206
LCCC
RES. 2512
1.7
1.E+07
1
1.E+06
R2 = 0.9649
1%
CHARACTERISTIC LIFE / SOLDER CRACK AREA
2
 joint / A (CYCLES/IN )
1.E+09
1.E+05
1.E-03
1.E-02
1.E-01
1.E+00
CYCLIC SHEAR STRAIN RANGE

First-order correlation obtained by:



Scaling characteristic life for solder joint crack area
Using characteristic life for population of critical solder joints
Do not use for life predictions or AF calculations
–
Dwell time, frequency effects etc… not included
Clech, APEX 2004 - Copyright © EPSI Inc., 2004
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Correlation of SAC Test Data:
Sorted by Board Finish
CHARACTERISTIC LIFE / SOLDER CRACK AREA
2
joint / A (CYCLES/IN )
1.E+09
na
Ag
NiAu
OSP
1.E+08
(na = Not Available)
1.E+07
1.E+06
1.E+05
1.E-03
1.E-02
1.E-01
1.E+00
CYCLIC SHEAR STRAIN RANGE

First-order correlation does not show significant board finish effect

Slide # 4 data re-plotted by board finish type
Clech, APEX 2004 - Copyright © EPSI Inc., 2004
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Correlation of SAC Test Data:
Sorted by Alloy
1.E+09
CHARACTERISTIC LIFE / SOLDER CRACK AREA:
2
joint / A (CYCLES/IN )
Sn3.8Ag0.7Cu
Sn3.9Ag0.6Cu
1.E+08
1.E+07
1.E+06
1.E+05
1.E-03
1.E-02
1.E-01
1.E+00
CYCLIC SHEAR STRAIN RANGE
Clech, APEX 2004 - Copyright © EPSI Inc., 2004
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SAC versus SnPb Test Data Correlation
(Leadless Assemblies)
3.5 X
2
CHARACTERISTIC LIFE / CRACK AREA (cycles/in )
1.E+10
SnPb
SAC
SAC
1.E+09
SnPb
"HIGH STRESS":
SN-PB > SAC
1.E+08
1.E+07
"LOWER STRESS":
SAC > SN-PB
6.2%
1.E+06
1.E+05
1.E-04


1.E-03
1.E-02
1.E-01
CYCLIC SHEAR STRAIN RANGE
1.E+00
Difference in slopes suggests opposite reliability under low and
high stress conditions
Do not use for life predictions or AF calculations
–
Dwell time, frequency effects etc… not included
Clech, APEX 2004 - Copyright © EPSI Inc., 2004
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SAC vs. SnPb: Creep Rate Comparison
1.E+00
1.E+00
Darveaux, Sn40Pb, 67C
1.E-01
Zhang, SAC 3906, 25C
1.E-01
Zhang, SAC 3906, 75C
1.E-02
Dusek, SAC 3807, 21C
1.E-02
Pang, SAC 3807, 75C
STRAIN RATE (/SEC)
STRAIN RATE (/SEC)
Darveaux, Sn40Pb, 27C
Pang, SAC 3807, 25C
1.E-03
SAC & SnPb
1.E-04
18.1 MPa
1.E-05
1.E-06
1.E-07
1.E-08
21-27C DATA
(294-300K, D = 2.0%)
SnPb
1.E-05
1.E-06
1.E-07
SnPb
67-75C DATA
(340-348K, D = 2.3%)
1.E-09
1
10
~ 25°C
100
~ 75°C
SHEAR STRESS (MPa)
1.E+00
Darveaux, Sn40Pb,
132C
Zhang, SAC 3906,
125C
Pang, SAC 3807,
125C
1.E-01
STRAIN RATE (/SEC)
13.8 MPa
1.E-04
1.E-08
1.E-09
1.E-02
1.E-03
1
10
100
SHEAR STRESS (MPa)
9.2 MPa
SAC
1.E-04
1.E-05

1.E-06
SnPb
1.E-07
1.E-08
125-132C DATA
(398-405K, D = 1.8%)
1.E-09
1.0
~ 125°C
1.E-03
SAC & SnPb
10.0
Under high stress conditions,
SAC creeps as fast as SnPb
regardless of temperature
100.0
SHEAR STRESS (MPa)
Clech, APEX 2004 - Copyright © EPSI Inc., 2004
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SAC vs. SnPb: Creep Rate Comparison (2)
1.E-01
1.E-01
Shi, Sn37Pb, 25C
Whitelaw, Sn40Pb, -55C
1.E-02
Neu, Sn2.5Ag0.8Cu0.5Sb, -55C
1.E-04
1.E-05
1.E-06
1.E-07
SAC
1.E-08
Takahashi, Sn3.5Ag0.5Cu, 25C
Neu, Sn4.0Ag, 25C
Neu, Sn2.5Ag0.8Cu0.5Sb, 25C
1.E-04
-55C Data
(218K)
1.E-05
SnPb
1.E-06
1.E-07
SAC
Sn3.5Ag
1.E-09
1.E-10
10
100
TENSILE STRESS (MPa)
1
~ 25°C
10
100
TENSILE STRESS (MPa)
1.E-01
Sn1.0Ag0.75Cu
Shi, Sn37Pb
1.E-02
1.E-02
Whitelaw, Sn40Pb, 75C
Takahashi, Sn3.5Ag0.5Cu
1.E-03
SnBi
1.E-03
Neu, Sn4.0Ag
1.E-04
Neu, Sn2.5Ag0.8Cu0.5Sb
1.E-05
Power (Whitelaw, Sn40Pb,
75C)
1.E-06
STRAIN RATE (MPa)
STRAIN RATE (MPa)
Data at 23C-30C
(296-303K, D = 2.4%)
SnPb
1.E-10
1
1.E-01
SnPb
SAC
1.E-07
1.E-08
1.E-04
SnPb
1.E-05
1.E-06
SAC
1.E-07
Data at 75C
(348K)
1.E-10
1
10
TENSILE STRESS (MPa)
Clech, APEX 2004 - Copyright © EPSI Inc., 2004
100
1.E-09
~ 125°C
Data at 120-125C
(393-398K, D = 1.3%)
Amagai, Sn1.0Ag0.75Cu, 125C
Shi, Sn37Pb, 125C
Whitelaw, Sn40Pb, 125C
Raeder, Sn52Bi, 120C
Takahashi, Sn3.5Ag0.5Cu, 125C
Neu, Sn4.0Ag, 125C
Neu, Sn2.5Ag0.8Cu0.5Sb, 125C
1.E-08
1.E-09
75°C
SnBi
Huang, Sn3.5Ag
1.E-08
1.E-09
-55°C
Raeder, Sn52Bi, 30C
1.E-03
SnPb
STRAIN RATE (MPa)
STRAIN RATE (MPa)
1.E-03
Whitelaw, Sn40Pb, 23C
1.E-02
Neu, Sn4.0Ag, -55C
1.E-10
1
10
100
TENSILE STRESS (MPa)
9
Sn0.7Cu vs. SnPb
1.E+06
SnPb
1.E+04
1.E+05
Sn
-40Pb
CYCLES TO FAILURE
SAC
Sn0.7Cu
1.E+03
Sn3.5Ag
1.E+04
Sn1Cu
1.E+03
1.E+02
1.E+02
1.E+01
6.2%
CHARACTERISTIC LIFE (CYCLES)
1.E+05
1.E+01
1.E-02
1.E+00
1.E-01
1.E+00
CYCLIC SHEAR STRAIN RANGE
Correlations based on Bare Flip-Chip
Thermal Cycling Data (references in paper)

10
100
SHEAR STRESS (MPa)
Fatigue Testing Data at 20C
(ITRI Pub. # 656 ).
Compared to SnPb, SnCu fatigue trend appears opposite
that of SnAg / SAC trend
Clech, APEX 2004 - Copyright © EPSI Inc., 2004
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SAC vs. SnPb: Alloy 42 TSOPs
1.E+04
CHARACTERISTIC LIFE (CYCLES)
Intersect at
DT = 9°C
1
1.90
2.02
1
1.36X
1.31X
1.E+03
1.63X
PASTE / LEAD FINISH:
Sn37Pb / SnPb
Sn37Pb / Sn10Pb
Sn3.9Ag0.6Cu / SnPb
Sn3.0Ag0.7Cu / Sn10Pb
Sn3.0Ag0.7Cu / Sn2Bi
1.E+02
10
100
1000
DT (deg. C)

Alloy 42 TSOPs assembled with SAC have shorter test
lives than when assembled with SnPb

Sn2Bi finish provides for 31% life improvement over SnPb finish
Clech, APEX 2004 - Copyright © EPSI Inc., 2004
11
SAC vs. SnPb: Summary

Reversed trends under high vs. low to medium stress
conditions


Situation requires accurate life prediction models or acceleration factors
for reliability assessment under service conditions.
Need to consider data over a wide range of conditions
before conclusions can be drawn.

Lack of data at cyclic strain ranges < 1%
Clech, APEX 2004 - Copyright © EPSI Inc., 2004
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Mixed Assembly Test Results

Leadless SMT: with or without Pb contaminant

SnPb balls: SAC or SnPb paste

Clech, APEX 2004 - Copyright © EPSI Inc., 2004
SAC balls: SAC or SnPb paste
13
Leadless SMT with Pb Contamination
SAC + Pb Contaminant: Cycles to 1% Failure
1000
R1206 (-55 to 125C)
Board finish: Immersion Ag
Component finish: Sn0.7Cu or SnPb
800
1
1
LCCC 20 (-40 to 125C)
Board finish: SnPb HASL
or Immersion Ag
600
400
R2512 (-55 to 125C)
Board finish: SnPb HASL
or Cu / OSP
1
R0603 (-55 to 125C)
Board finish: SnPb HASL or Cu / OSP
200
Low Failure Count
for SAC + Pb
contaminant
R1206 (-55 to 125C):
Board finish: NiAu
Component:
Sn0.7Cu or SnPb finish
0
0
200
400
600
800
1000
100% SAC (no Pb): Cycles to 1% Failure

-55 to 125°C and -40 to 125°C data

Pb contamination (< 1% wt.) is from component (R1206) or board finish
(HASL SnPb).
Clech, APEX 2004 - Copyright © EPSI Inc., 2004
14
Area Array Assemblies with SnPb Paste
SAC Balls / SnPb Paste: Cycles to Low % Fails
SAC Balls
vs. SnPb
Balls
3000
-40 to 125C data
0 to 100C data
-55 to 125C data
1
1
FC-PBGA*
OSP
2000
0.74X
0.77X
CSP**
Cu
fleXPBGA
Ni/Au
1000
CSP**
NiAu
PBGA
NiAu or OSP
wbPBGA
OSP
0.68X
* : Cycles to First Fail between 1% and 5%
**: Cycles to 0.1% Failure
Others: Cycles to 1% Failure
TABGA
Ni/Au
0
0
1000
2000
3000
SnPb Balls / SnPb Paste: Cycles to Low % Fails

“Backward compatibility”: mixed record.

Limited data under 0/100°C conditions
Clech, APEX 2004 - Copyright © EPSI Inc., 2004
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Area Array Assemblies with SAC Balls
3000
SAC Balls / SAC Paste: Cycles to Low % Fails
SAC Paste
vs. SnPb
Paste
-40 to 125C data
0 to 100C data
-55 to 125C data
1
PBGA
NiAu or OSP
2000
CSP**
NiAu
1
FC-PBGA*
OSP
WCSP*
OSP
CSP**
Cu
1000
fleXPBGA
Ni/Au
* : Cycles to First Fail between 1% and 5%
**: Cycles to 0.1% Failure
Others: Cycles to 1% Failure
TABGA
Ni/Au
0
0
1000
2000
3000
SAC Balls / SnPb Paste: Cycles to Low % Fails

Under stated conditions, assemblies with SAC paste have similar
or longer life than with SnPb paste.
Clech, APEX 2004 - Copyright © EPSI Inc., 2004
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Area Array Assemblies with SnPb Balls
SAC Paste
vs. SnPb Paste
8000
-40 to 125C Data
1
1
PBGA 388
CSP 169
2000
PBGA 357
CSP 151
1000
0
1000
2000
SnPb Balls / SnPb Paste: Cycles to 1% Failure

0 to 100C Data
7000
1
1
6000
PBGA
5000
0.84
1
4000
3000
WCSPs
2000
PBGA 144 (15 to 95C)
FCPBGA
1000
2 data points
CSP
0
0

SnPb Balls / SAC Paste: Cycles to 1% Failure
SnPb Balls / SAC Paste: Cycles to 1% Failure
3000
3000
0
1000
2000
3000
4000
5000
6000
7000
8000
SnPb Balls / SnPb Paste: Cycles to 1% Failure
“Forward compatibility”: opposite trends depending on thermal
cycling conditions (-40/125°C vs. 0/100°C)
Test conditions matter, possible issue under milder conditions
Clech, APEX 2004 - Copyright © EPSI Inc., 2004
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Lead-free Assembly Reliability
- Conclusions

Lead-free assembly reliability is dependent on
package, assembly and test conditions

Reliability rank-ordering is strongly dependent on test conditions:
–


SnPb test standards may have to be optimized for Pb-free assemblies
Need accurate life prediction model(s) and acceleration factors to
extrapolate to use conditions
Mixed assemblies

Both “backward” and “forward” compatibility situations require
further attention.
Clech, APEX 2004 - Copyright © EPSI Inc., 2004
18
Speaker’s Bio



Jean-Paul Clech is the founder of EPSI Inc. in Montclair, New-Jersey. His activities at EPSI include technical
consulting with clients across the electronics industry, software development and professional training. He is the
principal developer of the Solder Reliability Solutions model and application software. His research interests cover
multi-disciplinary aspects of electronics packaging, Surface Mount Technology (SMT) and circuit board assemblies,
with emphasis on materials characterization and the application of materials and mechanical engineering
fundamentals to sound product design. He has consulted on the physical design of small and large circuit boards
and is constantly challenged by design and reliability problems brought about by emerging packaging and soldering
technologies, and the application of SMT in harsh environments. His current research interests are in the areas of
flip-chip assemblies, chip scale packages, mechanical flexing and vibration of board assemblies, lead-free material
properties and lead-free reliability assessment.
Jean-Paul previously was a member of the technical staff at AT&T Bell Laboratories and manager of electronic
packaging at a European super-computer start-up. He was trained as a metallurgist and received the "Diplôme d’
Ingénieur" degree (Materials Science major) from Ecole Centrale de Paris, France. He then received the M.S. and
Ph.D. degrees in mechanical engineering from Northwestern University, Evanston, Illinois, where he worked on the
mechanics and failures of hip and knee joint replacements. His interest in soldering and solder fatigue started during
a post-doctoral assignment in the Materials Science department at Northwestern. He is a recognized expert in the
field of surface mount assembly quality and reliability and has assisted law firms as an expert witness on packaging,
board and soldering related issues. Jean-Paul is an active member of ASME, IEEE, IMAPS, SMTA and TMS, has
published over thirty five papers and a book chapter, and has chaired numerous workshops and technical sessions at
international conferences. He has been an invited speaker, lecturer and seminar leader at corporations, universities
and R&D institutions in Asia, Europe and North America.
Contact information:



Home page URL: http://jpclech.com
E-mail: [email protected]
Tel.: +1 (973)746-3796; fax: +1 (973)655-0815
Clech, APEX 2004 - Copyright © EPSI Inc., 2004
19