A viscoplastic theory for braze alloys

Neilsen, M. K.; Burchett, S.N.; Stone, C.M.; Stephens, J. A.

doi:10.2172/233338

Cited by 26 publications

(10 citation statements)

References 11 publications

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“…The creep deformation kinetics were determined from the steady-state or minimum creep-rate parameter, dε/dt min , using the sinh law representation described by Eq. 1: dε/dt min ϭ A sinh p (ασ) exp(Ϫ∆H/RT) (1) In Eq. 1, A is a constant (sec Ϫ1 ), p is the sinh term (stress) exponent, α is the stress coefficient (MPa Ϫ1 ), σ is the true stress (MPa), ∆H is the apparent-activation energy, R is the universal gas constant (8.314 kJ/mol-K), and T is the temperature (K).…”

Section: Introductionmentioning

confidence: 99%

Creep behavior of the ternary 95.5Sn-3.9Ag-0.6Cu solder: Part II—Aged condition

Vianco

Rejent

Kilgo

2004

Journal of Elec Materi

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Compression creep tests were performed on the 95.5Sn-3.9Ag-0.6Cu (wt.%) solder. The specimens were aged prior to testing at 125°C, 24 h or 150°C, 24 h. Applied stresses were 2-40 MPa. Test temperatures were Ϫ25°C to 160°C. The 125°C, 24-h aging treatment caused the formation of coarsened Ag 3 Sn particle boundaries within the larger ternary-eutectic regions. The 150°C, 24-h aging treatment resulted in contiguous Ag 3 Sn boundaries in the ternary-eutectic regions as well as a general coarsening of Ag 3 Sn particles. The 125°C, 24-h aging treatment had only a small effect on the strain-time curves vis-à-vis the as-cast condition. Negative creep was observed at 75°C for time periods Ͼ10 5 sec and stresses of 3-10 MPa. The creep kinetics exhibited a sinh term (stress) exponent, p, of 5.3 Ϯ 0.6 and an apparent-activation energy, ∆H, of 49 Ϯ 5 kJ/mol when data from all test temperatures were included. A good data correlation was observed over the [Ϫ25-125°C] temperature regime. Steady-state creep kinetics exhibited a greater variability in the [125-160°C] regime because of the simultaneous coarsening of Ag 3 Sn particles. The aging treatment of 150°C for 24 h resulted in a more consistent stress dependence and better reproducibility of the creep curves. Negative creep was observed in samples aged at 150°C for 24 h when tested at Ϫ25°C, 25°C, and 75°C. The values of p and ∆H were 4.9 Ϯ 0.3 kJ/mol and 6 Ϯ 5 kJ/mol, respectively. Only a slight improvement in the data correlation was observed when the analysis examined separated [Ϫ25-75°C] and [75-166°C] temperature regimes. Creep testing did not cause observable deformation in any of the sample microstructures.

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Section: Introductionmentioning

confidence: 99%

Creep behavior of the ternary 95.5Sn-3.9Ag-0.6Cu solder: Part II—Aged condition

Vianco

Rejent

Kilgo

2004

Journal of Elec Materi

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“…The unified creep plasticity model is based on the model for braze alloys developed by Neilsen et al [16]. For small elastic strains, the total strain rate,ε, can be additively decomposed into elastic,ε e , and inelastic (creep + plastic),ε in , parts as follows:ε =ε e +ε in .…”

Section: A Solder Fatigue Modelingmentioning

confidence: 99%

Predicting the Effect of Underfill Filler Volume Fraction on Solder Fatigue Life and Residual Stress for Surface Mount Components Using Nonlinear Viscoelastic Analyses

Neidigk

Shen

2012

IEEE Trans. Compon., Packag. Manufact. Technol.

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Glassy thermoset polymer underfills are commonly used for reliability enhancement in modern electronics. By adding filler to the polymer, underfill mechanical properties, such as bulk and shear moduli and coefficient of thermal expansion, can be altered. Addition of underfills can affect the solder reliability and component failure during dynamic environments. By modifying the nonlinear viscoelastic simplified potential energy clock model, a generic computational tool was created for analyzing filled polymers. Together with a unified creep plasticity model for solder and the Coffin-Manson fatigue criterion, solder fatigue life for underfilled surface mount components was investigated for various underfill filler materials and filler volume fractions (FVFs) using finite element analyses. By creating models of representative components with very different geometries, the effect of adding an underfill and increasing the FVF of hard and glass micro-balloons (GMB) fillers was analyzed. For a large stiff component, the addition of an unfilled underfill reduced the localized tensile stress in the component. Underfill filler volume fractions greater than 10% for hard filler and 15% for GMB filler resulted in a positive effect on the fatigue life. The results were different for a small flexible component. The addition of an unfilled underfill slightly increased the localized tensile stress in the component, but a positive effect on the fatigue life was still demonstrated if the underfill FVFs were greater than 15% for hard filler and 30% for GMB filler.Index Terms-Fatigue, finite element analysis, solder, underfill, viscoelastic model.

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“…The base and interlayer metals were all modeled as temperature-dependent, elastic-plastic materials. The braze alloys were modeled using a visco lastic model that was recently developed specifically for braze alloys (Neilsen et al, 1996). !i ?…”

Section: Materials Behaviormentioning

confidence: 99%