Effect of microstructure evolution on Pb-free solder joint reliability in thermomechanical fatigue

Yin, Liang; Meilunas, Michael; Arfaei, Babak; Wentlent, Luke; Børgesen, Peter

doi:10.1109/ectc.2012.6248876

Cited by 7 publications

(5 citation statements)

References 22 publications

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“…For Sn-Ag-Cu alloys, additional difficulties come from the nonuniform distribution of particles and location-dependent coarsening kinetics. Isothermal shear fatigue experiments on as-solidified Sn-1.0Ag-0.5Cu joints showed a higher level of recrystallization than Sn-3.0Ag-0.5Cu joints, 49 although the two alloys had comparable average particle diameters of 0.33 lm for the former and 0.31 lm for the latter. The corresponding particle number densities were, however, 299 and 767 per 1000 lm 2 , respectively, suggesting that interparticle spacing played a more important role than particle size as far as recrystallization is concerned.…”

Section: Microstructure Evolutionmentioning

confidence: 86%

Recrystallization and Precipitate Coarsening in Pb-Free Solder Joints During Thermomechanical Fatigue

Yin

Wentlent

Yang

et al. 2011

Journal of Elec Materi

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102

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The recrystallization of b-Sn profoundly affects deformation and failure of Sn-Ag-Cu solder joints in thermomechanical fatigue (TMF) testing. The numerous grain boundaries of recrystallized b-Sn enable grain boundary sliding, which is absent in as-solidified solder joints. Fatigue cracks initiate at, and propagate along, recrystallized grain boundaries, eventually leading to intergranular fracture. The recrystallization behavior of Sn-Ag-Cu solder joints was examined in three different TMF conditions for five different ball grid array component designs. Based on the experimental observations, a TMF damage accumulation model is proposed: (1) strain-enhanced coarsening of secondary precipitates of Ag 3 Sn and Cu 6 Sn 5 starts at joint corners, eventually allowing recrystallization of the Sn grain there as well; (2) coarsening and recrystallization continue to develop into the interior of the joints, while fatigue crack growth lags behind; (3) fatigue cracks finally progress through the recrystallized region. Independent of the TMF condition, the recrystallization appeared to be essentially complete after somewhat less than 50% of the characteristic life, while it took another 50% to 75% of the lifetime for a fatigue crack to propagate through the recrystallized region.

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Section: Microstructure Evolutionmentioning

confidence: 86%

Recrystallization and Precipitate Coarsening in Pb-Free Solder Joints During Thermomechanical Fatigue

Yin

Wentlent

Yang

et al. 2011

Journal of Elec Materi

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102

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“…Since portable electronic products frequently experience mechanical shock loading caused by accidental dropping of devices resulting from mishandling and cyclic temperature variation during customer usage, the solder joints should be reliable under drop impact reliability and thermo-mechanical loading [1,2]. Common approaches to improve the reliability of solder joints including drop and thermo-mechanical reliability are to control the solder composition by adding the minor elements into the solders [3][4][5][6][7], and to diversify the metallization of wetting layer [8][9][10].…”

Section: Introductionmentioning

confidence: 98%

An eco-friendly Cu-Zn wetting layer for highly reliable solder joints

Kim

2013

2013 IEEE 63rd Electronic Components and Technology Conference

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“…11 Crack growth did, however, remain quite limited until a continuous network of high-angle grain boundaries had been established across the high-strain region in the joint. 11,13 At that point, fatigue cracks started to propagate much more rapidly through the region (Fig. 6).…”

Section: Damage and Failurementioning

confidence: 99%

“…For sufficiently low-strain ranges and initial precipitate sizes, the rate of recrystallization remains strongly reduced until after significant coarsening. 12,13,30,33 Since the initial precipitate size is sensitive to the degree of undercooling after reflow, this leads to systematic effects of solder joint dimensions and pad finishes on acceleration factors. 46 Clearly, failure to account for effects of precipitate coarsening on the damage function would lead to conservative extrapolations of test results to life span in milder cycling.…”

Section: Precipitate Coarseningmentioning

confidence: 99%

“…Instead, failure in thermal cycling almost always occurs by recrystallization of the Sn to form a network of high-angle grain boundaries across the joint [5][6][7][8][9][10] , followed by cracking along these boundaries. [11][12][13] It is our belief that the general picture below can be extended to explain the superior performance of a so-called interlaced twinning structure, 14 but that may require more work. The most credible approaches to quantitative modeling rely on the finite element modeling (FEM)-based calculation of stresses and strains, and often other factors derived from these (work, entropy, etc.…”

Section: Introductionmentioning

confidence: 99%

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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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Effect of microstructure evolution on Pb-free solder joint reliability in thermomechanical fatigue

Cited by 7 publications

References 22 publications

Recrystallization and Precipitate Coarsening in Pb-Free Solder Joints During Thermomechanical Fatigue

Recrystallization and Precipitate Coarsening in Pb-Free Solder Joints During Thermomechanical Fatigue

An eco-friendly Cu-Zn wetting layer for highly reliable solder joints

A Mechanistic Thermal Fatigue Model for SnAgCu Solder Joints

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