Global SMT & Packaging issue 8.9

Update on lead-free solder joint reliability
of accelerated reliability results and postulate appropriate coefficients for the Joint Reliability in a Lead-Free
illustrate the importance of following the Engelmaier-Wild model for SAC305/405 World, Part 2,” Global SMT &
temperature cycles mandated in IPC-9701. as well as SnAg solder joints. Packaging, Vol. 7, No. 8, August
Jean-Paul Clech has been trying 2007, pp. 44-46.
to make sense out of this plethora References:
of confusing data. Figure 14 shows a [1] Engelmaier, W., “Reliability of Lead- Werner Engelmaier will be giving some of
collection of data for which enough Free (LF) Solder Joints,” Global his solder joint reliability and PCB reliability
information was available to determine an SMT & Packaging, Vol. 3, No. 3, workshops at the SMTAI, August 17-19, 2008
“average shear strain.” April 2003, pp. 36-38. in Orlando, FL, the Reliability Conference
The important information from Figure [2] Engelmaier, W., “Reliability of Lead- in Stockholm, Sweden, September 3, 2008,
14 is that for accelerated testing, for Free (LF) Solder Joints Revisited,” and the IPC Fall Meeting, September 21-24,
which the creep process in each cycle is Global SMT & Packaging, Vol. 3, 2008 in Schaumburg, IL; for details on the
substantially incomplete, there is little No. 7, October 2003, pp. 26-27. workshops go to www.engelmaier.com; for more
difference in the creep-fatigue results [3] Engelmaier, W., “Lead-Free (LF) information about the workshops in Schaumburg
for Sn37Pb and SAC305/405. Since the Wave-soldering: Can (should) it contact www.ipc.org, for the SMTAI 2008
creep process is much slower for SAC- be Eliminated,” Global SMT & workshops www.smta.org, and for Stockholm
solders, and thus the creep process is Packaging, Vol. 5, No. 9, October LarsWallin@ipc.org.
much less complete for SAC-solders than 2005, pp. 46-50.
SnPb-solders for the typical 10-minute [4] Engelmaier, W., “Achieving Solder Werner Engelmaier has over 42 years
dwells, it needs to be expected that SAC Joint Reliability in A Lead-Free experience in electronic packaging and
solder joints result in somewhat lower World, Part 1,” Global SMT & interconnection technology and has published
fatigue lives than SnPb solder joints under Packaging, Vol. 3, No. 6, June 2007, over 180 papers, columns, book chapters and
identical product operational conditions. pp. 40-42. White Papers. Known as ‘Mr. Reliability’ in
In the next column, I will attempt to [5] Engelmaier, W., “Achieving Solder the industry, he is the president of Engelmaier
Fig. 9

400 I/O 21 mm

Ceramic 169 CSP on FR-4
90
Package on FR-4,

90
ATC: -40 +125°C
25 mil balls, Dwells: ??
75

ATC: per IPC-9701
75

SnPb/SnPb , = 6.6
0100°C,
50
10°C/min ramps,

50
SAC/SAC, = 11.3

14 minute dwells

SnPb/SAC, = 7.7

25
Sn37Pb

25
SAC 305

% Failed
90Pb10Sn
10

% Failed
10

5

5

2 2
1 1
10
2
200 500 10
3
2,000 5,000 10
4
10
2
200 500 10
3
2,000 5,000
11
10
4
Cycles-to-Failure
9
Cycles-to-Failure
Figure 9. Weibull plots of Sn37Pb, SAC305 and 90Pb10Sn Figure 11. Weibull plots of SnPb/SnPb, SAC/SAC and mixed SnPb/SAC solder joints
[Source: S. Movva, et al., Kyocera, USA]. [Source: iNEMI, USA].
169 CSP on FR-4
PBGA 676 on FR-4
90
ATC: 0 100°C 90
ATC: 0 100°C
Dwells: ??
Dwell @ 0°C: 10 min
75
75
SnPb/SnPb , = 7.5
Dwell @ 100°C: 10 min
60 min
50
SAC/SAC, = 4.1 50 SnPb/SnPb, =11.8

SnPb/SAC , = 2.9

SAC/SAC, = 12.0
25
SAC/SnPb, = 6.1
25 SAC/SAC, = 12.6
SAC/SnPb, = 6.9
% Failed
% Failed
10
10
5
5
2
2
1
1
10
3
2,000 3,000 5,000 7,000
4
12
10
10
2
200 500 10
3
2,000 5,000
Cycles-to-Failure
10
10
4
Cycles-to-Failure
Figure 12. Weibull plots of SnPb/SnPb, SAC/SAC and mixed SnPb/SAC solder joints
Figure 10. Weibull plots of SnPb/SnPb, SAC/SAC and mixed SnPb/SAC solder joints with 10-minute and asymmetric 10/60-minute dwells (Note: All failures on component
[Source: iNEMI, USA]. side) [Source: J. Bath, Solectron, et al., (Lead-Free working Group), USA].
48 – Global SMT & Packaging - August 2008 www.globalsmt.net
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