The effect of Sn grain number and orientation on the shear fatigue life of SnAgCu solder joints

Arfaei, Babak; Xing, Yan; Woods, J.; Wolcott, J.A.; Tumne, Pushkraj; Børgesen, Peter; Cotts, E. J.

doi:10.1109/ectc.2008.4550012

Cited by 30 publications

(10 citation statements)

References 21 publications

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“…The variable undercooling causes the microstructure to vary from joint to joint [12] and the small number of grains per joint is a concern because βSn is tetragonal and has highly anisotropic properties such as thermal expansion [13] stiffness [14], and the diffusion of Ni and Cu [15,16]. The orientation of the βSn grain(s) plays an important role in electromigration resistance [17][18][19][20][21] and in the lifetime of a joint during thermal cycling [22,23]. The presence of few βSn grains that are oriented differently in each joint makes every joint unique which is a problem for predicting reliability.…”

Section: Introductionmentioning

confidence: 99%

Grain refinement of electronic solders: The potential of combining solute with nucleant particles

Shang

Belyakov

et al. 2017

Journal of Alloys and Compounds

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Sn-Ag-Cu electronic solder joints typically solidify from a single nucleation event producing either a single βSn grain or twinned grains. With so few and variable βSn orientations, each joint is mechanically unique due to the anisotropy of tetragonal βSn. Here we explore the potential of increasing the number of βSn orientations in solder joints by promoting heterogeneous nucleation during solidification. It is shown that large (60 g) samples can be grain refined effectively by combining growth restricting solute with potent heterogeneous nucleant particles introduced by alloying additions of Zn, Ti, Co, Ir, Pd, or Pt. These mechanisms are discussed with reference to the grain refinement of structural casting alloys.In 500 μm solder balls, these grain refinement approaches were less effective and a relatively high cooling rate of 17 K/s combined with solute and nucleant particles were required to trigger multiple nucleation events. With this approach, up to 12 independent grains formed in 500 μm balls of Sn-3Ag-0.5Cu alloyed with Pt, Co, or Ti, compared with one independent grain in balls without nucleant particle additions.

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Section: Introductionmentioning

confidence: 99%

Grain refinement of electronic solders: The potential of combining solute with nucleant particles

Shang

Belyakov

et al. 2017

Journal of Alloys and Compounds

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“…Indeed, detailed studies have shown thermal cycling of SnAgCu joints to first lead to the formation of new subgrains within the individual b-Sn dendrites 12 ), and eventually between the densely spaced precipitates as well, after which these subgrains then continue to rotate during ongoing cycling. 8,12,23,25 In fact, while the extent of the recrystallized region does not seem to change much beyond the stage shown in Fig. 6, the subgrains continue to rotate towards ever greater degrees of misorientation.…”

Section: Recrystallizationmentioning

confidence: 99%

“…Bieler and co-workers suggested that crack evolution is controlled by the ongoing rotation of subgrains until they reach a particular orientation. 23,25 More work is needed to fully understand the actual mechanism, but that is not important for our model at the present stage.…”

Section: Damage and Failurementioning

confidence: 99%

A Mechanistic Thermal Fatigue Model for SnAgCu Solder Joints

Børgesen

Wentlent

Hamasha

et al. 2018

Journal of Elec Materi

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The present work offers both a complete, quantitative model and a conservative acceleration factor expression for the life span of SnAgCu solder joints in thermal cycling. A broad range of thermal cycling experiments, conducted over many years, has revealed a series of systematic trends that are not compatible with common damage functions or constitutive relations. Complementary mechanical testing and systematic studies of the evolution of the microstructure and damage have led to a fundamental understanding of the progression of thermal fatigue and failure. A special experiment was developed to allow the effective deconstruction of conventional thermal cycling experiments and the finalization of our model. According to this model, the evolution of damage and failure in thermal cycling is controlled by a continuous recrystallization process which is dominated by the coalescence and rotation of dislocation cell structures continuously added to during the hightemperature dwell. The dominance of this dynamic recrystallization contribution is not consistent with the common assumption of a correlation between the number of cycles to failure and the total work done on the solder joint in question in each cycle. It is, however, consistent with an apparent dependence on the work done during the high-temperature dwell. Importantly, the onset of this recrystallization is delayed by pinning on the Ag 3 Sn precipitates until these have coarsened sufficiently, leading to a model with two terms where one tends to dominate in service and the other in accelerated thermal cycling tests. Accumulation of damage under realistic service conditions with varying dwell temperatures and times is also addressed.

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“…Since the microstructure of Pb-free BGA or flip-chip joints are known to be either a single crystal or composed of a few grains [28,97], the fatigue performance of Pb-free solder joints would be strongly affected by the crystal orientation of Sn matrix. In the conventional thermal cycling test, solder bumps at the corner of a Si chip or module with the largest DNP would expect to fail first, but this situation would not be warranted when the crystal orientation of Sn matrix plays into the failure process.…”

Section: Thermal Fatigue Resistancementioning

confidence: 99%

“…In the conventional thermal cycling test, solder bumps at the corner of a Si chip or module with the largest DNP would expect to fail first, but this situation would not be warranted when the crystal orientation of Sn matrix plays into the failure process. An example was discussed with Pbfree BGA solder joints, where the c-axis of Sn-crystal was oriented parallel to the substrate direction, premature failures were observed regardless of the position of solder joints [28,97].…”

Section: Thermal Fatigue Resistancementioning

confidence: 99%

‘Effects of Minor Alloying Additions on the Properties and Reliability of Pb‐Free Solders and Joints’

Kang¹

2012

Lead‐Free Solders: Materials Reliability for Electronics

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Since July, 2006, following the EUs RoHS legislation, the consumer electronics industry has been offering 'green' products by eliminating Pb-containing solders and other toxic materials. This transition has been relatively smooth, because the reliability requirements are less stringent. However, the Pb-free transition for high-performance electronic systems (such as servers and telecommunication) is still on-going due to their rigorous reliability requirements. For example, the research and development efforts to implement Pb-free flipchip interconnections for high-end applications are still very active.In this chapter, the recent progress in Pb-free solder development, especially minor alloy additions to Sn-rich solders is reviewed in light of improving various physical, mechanical, metallurgical or electrical properties of solder joints. The topics to be discussed include those such as control of undercooling, microstructure, interfacial reactions, or void formation, as well as enhancing impact resistance, electromigration, and other mechanical properties.

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The effect of Sn grain number and orientation on the shear fatigue life of SnAgCu solder joints

Cited by 30 publications

References 21 publications

Grain refinement of electronic solders: The potential of combining solute with nucleant particles

Grain refinement of electronic solders: The potential of combining solute with nucleant particles

A Mechanistic Thermal Fatigue Model for SnAgCu Solder Joints

‘Effects of Minor Alloying Additions on the Properties and Reliability of Pb‐Free Solders and Joints’

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