Reliability of wafer level chip scale packages (WL-CSP) under dynamic loadings

Lee, Y.J.; Crosbie, P.; Brown, Matthew; Zbrzezny, A.R.

doi:10.1109/ectc.2008.4550222

Cited by 10 publications

(3 citation statements)

References 11 publications

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“…Dynamic loading was generated in the test vehicle through four-point bend test setup similar to the those reported earlier [2,4,5]. In this setup the test vehicle was centered in a fourpoint bend fixture and a known impact weight was dropped on to the top span fixture from different heights to control the stress and strain levels subjected to the test boards.…”

Section: Experimental Details Impact Bend Testmentioning

confidence: 99%

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Reliability of mixed alloy ball grid arrays using impact bend test and drop shock test

Pandher¹,

Pachamuthu²,

Raut³

2011

2011 IEEE 61st Electronic Components and Technology Conference (ECTC)

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Low-silver SnAgCu alloys are quickly becoming the standard Pb-free solders for portable electronic devices. However, the industry's quick adoption of near-eutectic SnAgCu alloys (SAC305 and SAC405, so called high-Ag Alloys) and its resistance to the adopted process change entails unavoidable situations where the components have a high-Ag SAC alloy while the paste used to assemble these components on the boards has a low-Ag alloy or vice versa. The impact of such mixed alloy assemblies has been and continues to be the subject of many recent studies.In this study, the mechanical reliability of printed circuit boards with a number of Pb-free BGA components assembled using two different Pb-free solder pastes (SACX and SAC105) has been studied using the Dynamic Four Point Bend Test (also called Impact Bend Test) and the Drop Shock Test. In the impact bend test, these boards were subjected to different mechanical shocks resulting in different strains. Results were plotted as the percentage of failed solder joints as a function of the strain experienced at the board and fitted to a Weibull distribution to estimate the usable life of the assembly in such circumstances. The drop shock test was conducted per JEDEC standard JESD22-B111 according to which the boards are subjected to the same mechanical shock repeatedly, and the failure fraction data was plotted as a function of the number of drops. The combinations of the BGA solder sphere alloy and the paste alloy used in the drop shock tests were exactly the same as those used in the Impact Bend Test.Results of both impact bend and drop shock tests show very good correlation. Analysis of the failed samples was done with the Dye and Pry test to identify whether the failure was on the board side or on the component side. Failure analysis of the impact bend test samples showed a slight difference in the distribution of failures on the component side and those on the board side. In drop shock test, most of the solder joints failed on the component side. Results show that even in the situations where the quantity of the solder coming from the solder paste was small relative to the quantity contributed by the sphere, the impact of the paste alloy was significant. An attempt was made to explain the observations in terms of solder inter-diffusion kinetics and resulting micro-structural changes. IntroductionIt is estimated that more than ten trillion solder joints are made annually in the electronics industries for various applications (e.g., mobile, aerospace, etc.). Solder joint is the interconnect technology that provides electrical continuity and mechanical integrity between the pad and component in the electronics assemblies [1]. With the recent trend towards

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Section: Experimental Details Impact Bend Testmentioning

confidence: 99%

“…The reliability of mid-size wafer level chip scale packages (WL-CSPs) with SAC105 for mobile applications was studied by Yeong Lee et al, and tested under dynamic loading using four-point bend test [5]. In a study by Reiff and Bradley, the impact bend test reliability of BGA 244 using Sn3.8Ag0.7Cu was studied.…”

Section: Introductionmentioning

confidence: 99%

Reliability of mixed alloy ball grid arrays using impact bend test and drop shock test

Pandher¹,

Pachamuthu²,

Raut³

2011

2011 IEEE 61st Electronic Components and Technology Conference (ECTC)

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“…Reflow profile for lead-free assembly: peak temperature 235 C, reflow under air. (1) Dynamic Bending Test (DBT) A high strain rate drop test reported by Motorola [1][2][3] was adopted in this work to measure failure behavior of the secondlevel package reliability for mobile applications. This test was found to regenerate the failure mode of solder joints in surface mount devices found in the phone drop [4].…”

Section: Introductionmentioning

confidence: 99%

Shock resistant and thermally reliable low Ag SAC solder doped with Mn

Goudarzi¹,

Brown

Liu³

et al. 2013

2013 14th International Conference on Electronic Packaging Technology

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98.5Sn0.5Ag1Cu0.05Mn (SAC0510M) exhibits a melting behavior similar to SAC105. It is two times better than SAC105 in the dynamic bending test; more than 8 times better in the modified JEDEC drop test; and more than 40-60% better in the -55 C/125 C thermal cycling test. The reduced hardness and much thinner and stable IMC layer on Ni are responsible for the superior nonfragility, while the stabilized IMC and microstructure are responsible for the thermal cycling performance. A thinner IMC layer on Ni is more important than reduced hardness in improving non-fragility. The thermal cycling performance of SAC0510M may override SAC305. A high Tg brittle board causes poor drop test results due to pad cratering. INTRODUCTIONLead-free soldering has been widely adopted by the electronics industry, with SnAgCu (SAC) having high Ag content being the initial main stream of choice. This selection was later challenged due to the fragility of solder joints toward drop and the high cost of Ag. Low Ag SAC was considered to be a solution for resolving both issues. However, this approach compromised temperature cycling performance, making it unacceptable for high end applications. Previously, a low Ag SAC alloy doped with Mn, SACM™, was reported to have considerable improvement in shock resistance and thermal fatigue performance. In this study, a second generation alloy within the SACM family was developed with significantly more improvement. It was evaluated against SAC105 for JEDEC22B111 drop, dynamic bending test, and IPC-9701 -55/125 C temperature cycling. The improvement essentially eliminated the need for underfilling for BGA and CSP on mobile devices, and the results are presented and discussed.

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Prevailing Lead-Free Materials

Lau

Lee

2020

Assembly and Reliability of Lead-Free Solder Joints

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Reliability of wafer level chip scale packages (WL-CSP) under dynamic loadings

Cited by 10 publications

References 11 publications

Reliability of mixed alloy ball grid arrays using impact bend test and drop shock test

Reliability of mixed alloy ball grid arrays using impact bend test and drop shock test

Shock resistant and thermally reliable low Ag SAC solder doped with Mn

Prevailing Lead-Free Materials

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