Whisker and Hillock formation on Sn, Sn–Cu and Sn–Pb electrodeposits

Boettinger, William J.; Johnson, C.E.; Bendersky, Leonid A.; Moon, Kil-Won; Williams, Maureen E.; Stafford, Gery R.

doi:10.1016/j.actamat.2005.07.016

Cited by 309 publications

(223 citation statements)

References 28 publications

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“…Therefore, rapid diffusion because of the high temperature and the presence of a relatively poor diffusion barrier in the pathway of the Zn and Cu put the Sn coating under more compressive stress. 56 In addition, as suggested by Boettinger et al, 55 formation of Cu 6 Sn 5 IMC at the interface of the Sn and Cu substrate from the supersaturated Sn causes a fractional volume change of +0.022 leading to increased compressive stress in the Sn.…”

Section: Effect Of Thermal Treatment On Whisker Formationmentioning

confidence: 96%

“…Furthermore, the presence of an Ni interlayer can significantly slow diffusion of the substrate atoms (Cu or Zn) into the Sn coating; this also suppresses the growth of Cu 6 Sn 5 , an interfacial IMC credited with increasing the compressive stress in Sn coating. 55 In addition, diffusion of Zn from the brass substrate, as used in this study, into the Sn coating may mechanistically be very different from diffusion of Cu, only, into Sn. Therefore, the different results in this study and in that by Lal and Moyer 24 may arise because of the use of different substrates, grain sizes, the interlayer, and the bath chemistry.…”

Section: Texture and Whisker Formationmentioning

confidence: 99%

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Manipulating Crystallographic Texture of Sn Coatings by Optimization of Electrodeposition Process Conditions to Suppress Growth of Whiskers

Jagtap

Kumar

2015

Journal of Elec Materi

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The effects of two major electrodeposition process conditions, electrolyte bath temperature and current density, on the microstructure and crystallographic texture of pure tin coatings on brass and, ultimately, on the extent of whisker formation have been examined. The grain size of the deposited coatings increased with increasing electrolyte bath temperature and current density, which significantly affected the dominant texture: (211) or (420) was the dominant texture at low current densities whereas, depending on deposition temperature, (200) or (220) became the dominant texture at high current densities. After deposition, coatings were subjected to different environmental conditions, for example isothermal aging (room temperature, 50°C, or 150°C) for up to 90 days and thermal cycling between À25°C and 85°C for 100 cycles, and whisker growth was studied. The Sn coatings with low Miller index planes, for example (200) and (220), and with moderate aging temperature were more prone to whiskering than coating with high Miller index planes, for example (420), and high aging temperature. A processing route involving the optimum combination of current density and deposition temperature is proposed for suppressing whisker growth.

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Section: Effect Of Thermal Treatment On Whisker Formationmentioning

confidence: 96%

Section: Texture and Whisker Formationmentioning

confidence: 99%

Manipulating Crystallographic Texture of Sn Coatings by Optimization of Electrodeposition Process Conditions to Suppress Growth of Whiskers

Jagtap

Kumar

2015

Journal of Elec Materi

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“…This conclusion is also consistent with reported stress measurements within the Sn layer which are very near the nominal yield stress for Sn (14.5 MPa 15 ) and remain relatively constant over time. 7,11,13,16 In addition, self-diffusion along grain boundaries within Sn is assumed to provide a fast pathway for long-range transport. 5,17 The role played by these plastic deformation processes in the development of stress within Sn films, however, has not been quantitatively assessed.…”

Section: Introductionmentioning

confidence: 99%

“…However, there is no clear consensus regarding the mechanisms by which localized growth of IMCs produces stress within the Sn film. [5][6][7][8][9][10][11][12][13][14] In order to understand how stress develops in response to IMC growth, it is necessary to identify the mechanical deformation processes operating in the surrounding Sn film. Recent experimental work provides evidence of extensive dislocation activity within the Sn film, especially in the neighborhood of IMC grains, 13,14 indicating that the Sn grains yield plastically.…”

Section: Introductionmentioning

confidence: 99%

Finite Element Modeling of Stress Evolution in Sn Films due to Growth of the Cu6Sn5 Intermetallic Compound

Buchovecky

Jadhav

Bower

et al. 2009

Journal of Elec Materi

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We use finite element simulations to quantitatively evaluate different mechanisms for the generation of stress in Sn films due to growth of the Cu 6 Sn 5 intermetallic phase at the Cu-Sn interface. We find that elastic and plastic behavior alone are not sufficient to reproduce the experimentally measured stress evolution. However, when grain boundary diffusion is included, the model results agree well with experimental observations. Examination of conditions necessary to produce the observed stresses provides insight into potential strategies for minimizing stress generation and thus mitigating Sn whisker growth.

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“…1,2 The majority of recent tin whisker research has concentrated on coupons or components with an emphasis on the Sn plating composition, thickness, grain size, grain orientations, and Ni underlayer. [2][3][4][5][6][7][8][9][10][11][12] These studies produced a great deal of knowledge; however, they do not consider the very real situation in which components are assembled on circuit boards using Pb-free solder pastes. Recent observations have demonstrated the ability of Pb-free solder joints to grow whiskers.…”

Section: Introductionmentioning

confidence: 99%

Whisker Formation on SAC305 Soldered Assemblies

Meschter

Snugovsky²,

Bagheri³

et al. 2014

JOM

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This article describes the results of a whisker formation study on SAC305 assemblies, evaluating the effects of lead-frame materials and cleanliness in different environments: low-stress simulated power cycling (50-85°C thermal cycling), thermal shock (-55°C to 85°C), and high temperature/high humidity (85°C/85% RH). Cleaned and contaminated small outline transistors, large leaded quad flat packs (QFP), plastic leaded chip carrier packages, and solder balls with and without rare earth elements (REE) were soldered to custom designed test boards with Sn3Ag0.5Cu (SAC305) solder. After assembly, all the boards were cleaned, and half of them were recontaminated (1.56 lg/cm 2 Cl À ). Whisker length, diameter, and density were measured. Detailed metallurgical analysis on components before assembly and on solder joints before and after testing was performed. It was found that whiskers grow from solder joint fillets, where the thickness is less than 25 lm, unless REE was present. The influence of lead-frame and solder ball material, microstructure, cleanliness, and environment on whisker characteristics is discussed. This article provides detailed metallurgical observations and select whisker length data obtained during this multiyear testing program.

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Whisker and Hillock formation on Sn, Sn–Cu and Sn–Pb electrodeposits

Cited by 309 publications

References 28 publications

Manipulating Crystallographic Texture of Sn Coatings by Optimization of Electrodeposition Process Conditions to Suppress Growth of Whiskers

Manipulating Crystallographic Texture of Sn Coatings by Optimization of Electrodeposition Process Conditions to Suppress Growth of Whiskers

Finite Element Modeling of Stress Evolution in Sn Films due to Growth of the Cu6Sn5 Intermetallic Compound

Whisker Formation on SAC305 Soldered Assemblies

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