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solders in terms of frequency and interconnect will perform its intended References
mean temperature. Osterman, et al., function for a specified period of time 1. J. H. Lau, (Ed.), Solder Joint Reliability:
[11] proposed another modification of under a given operating condition Theory and Applications, Van Nostrand
the classical Norris-Landzberg equation without failure. Reinhold, New York, April 1991.
by replacing the maximum temperature • The one and only way to determine 2. J. H. Lau, “Design for reliability,
during thermal cycling with the mean the interconnect (e.g., solder joint) reliability testing and data analysis,
temperature during thermal cycling. The reliability is by reliability testing and failure analysis of solder joints,”
revised equation takes the following form: to determine the parameters of a NEPCON West Workshops, Anaheim,
life distribution, F(x). Once F(x) is CA, Feb. 1990.
estimated, the reliability, failure 3. J. H. Lau, E. Schneider, T. Baker, “Shock
rate, cumulative failure rate, average and vibration of solder bumped flip-
where a, b, and c are the constants for the failure rate, mean-time-to-failure, chip on organic coated copper boards,”
temperature range (∆ T ), frequency (f), and etc., of the interconnect are readily ASME Trans., J. of Elec. Packaging, Vol.
mean temperature during cycling (T mean ), determined. 118, June 1996, pp. 101-104.
respectively. For lead-free solders such as • The life distribution, F(x), is package/ 4. J. H. Lau, Y. Pao, Solder Joint Reliability
SAC305, SAC405, SAC205, SAC105, component dependent. Actually, of BGA, CSP, Flip Chip, and Fine Pitch
SAC0307, SN100C, SN100C-SAC305, it is also affected by the chip size, SMT Assemblies, McGraw-Hill, New
SAC105-Ni, and SAC107, a nonlinear curve solder alloy, type of pastes, PCB York, 1997.
fit of the thermal cycling data of the material, PCB thickness, number 5. J. H. Lau, N. C. Lee, Assembly and
CABGA and CTBGA on PCB at various of copper layers in the PCB, reflow Reliability of Lead-Free Solder Joints,
t e m p e r a t u r e r a n g e s s u c h a s condition, solder joint volume, voids Springer, New York, 2020.
0 100ºC, -40 100ºC, -40 125ºC, 25 in the solder joint, test condition, 6. J. H. Lau, M. Li, M. M. Li, I. Xu,
125ºC, and -15 125ºC, the constants a, b, continuity measurement, number of T. Chen, Z. Li, et al., “Design,
and c of the above equation have been measurements during each cycle, materials, process, fabrication, and
obtained by Osterman, et al., [11] and are the data acquisition system, failure reliability of fan-out wafer-level
tabulated in Table 2. criteria, data analysis method, etc. packaging,” IEEE Trans. on CPMT,
For example, the test conditions are: 0 • For a given confidence level, the Vol. 8, No. 6, June 2018.
100ºC with 24 cycles per day and find the method to determine the true Weibull 7. J. Lau, W. Dauksher, P. Vianco,
product with SAC305 solder that survives slope, true characteristic life, and “Acceleration models, constitutive
990 cycles. Is it sufficient for a 10-year true mean life can be found in [5]. equations and reliability of lead-free
operating condition of 20 60ºC with 1 • The procedure for determining the solders and joints,” IEEE/ECTC Proc.,
cycle per day? confidence when comparing the mean May 2003, pp. 229-236.
life of two difference populations can 8. N. Pan, G. Henshall, F. Billaut, S. Dai, M.
also be found in [5]. Strum, R. Lewis, et al., “An acceleration
• All the papers in the literature, model for Sn-Ag-Cu solder joint
The product with SAC305 will survive whether intentional or not, are reliability under various thermal cycle
4.73 x 990 cycles per day = 4682.7 ÷ 365 = dealing with liner acceleration, i.e., conditions,” SMTA Inter. Conf. Proc.,
12.82 years > 10 years. x o =αx T or N o =αN T , where α is the Sept. 2005, pp. 876-883.
linear acceleration factor. Other 9. J. Miremadi, G. Henshall, A. Allen, E.
Summary and recommendations accelerations and factors have to Benedetto, M. Roesch, “Lead-free solder-
S o m e i m p o r t a n t r e s u l t s a n d be experimentally investigated for joint-reliability model enhancement,”
recommendations are summarized follows: different SMDs, lead-free solder IMAPS Proc., Oct. 2009, pp. 316-323.
alloys, and test conditions. 10. P. Lall, A. Shirgaokar, D. Arunachalam,
• Reliability engineering consists • Linear acceleration factors for “Norris-Landzberg acceleration factor
of three major tasks: design for various lead-free solder alloys based and Goldmann constants for SAC305
reliability, reliability testing and data on: a) frequency and maximum lead-free electronics,” ASME Trans.,
analysis, and failure analysis. temperature, b) dwell time and J. of Elec. Packaging, Vol. 134, Sept.
• The reliability of an interconnect maximum temperat ure, and c) 2012, pp. 1-8.
(e.g., solder joint) of a particular frequency and mean temperature 11. M. Osterman, “Modeling temperature
package in an electronic product is have been systematically presented. cycle fatigue life of select SAC solders,”
defined as the probability that the SMTA Inter. Conf., Sept. 2018.

Biography
John H. Lau is the CTO at Unimicron Technology Corporation, Taoyuan City, Taiwan (ROC). He has more
than 40 years of R&D and manufacturing experience in semiconductor packaging, 500 peer-reviewed papers,
30 issued and pending US patents, and 20 textbooks. He is an ASME Fellow, IEEE Fellow, and IMAPS Fellow.
He earned a PhD degree from the U. of Illinois at Urbana-Champaign. Email John_Lau@unimicron.com

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