Effect of Isothermal Aging on Microstructure and Creep Properties of SAC305 Solder: A Micromechanics Approach

2013 ◽  
Author(s):  
Preeti Chauhan ◽  
Subhasis Mukherjee ◽  
Michael Osterman ◽  
Abhijit Dasgupta ◽  
Michael Pecht
Keyword(s):  
Isothermal Aging ◽  
Solder Joints ◽  
Volume Fraction ◽  
Coarse Grained ◽  
Creep Model ◽  
Secondary Creep ◽  
Dispersion Strengthening ◽  
Sac305 Solder ◽  
Particle Spacing ◽  
Cu6sn5 Imcs

SnAgCu (SAC) solders undergo continuous micro structural coarsening during both storage and service. In this study, we use cross-sectioning and image processing techniques to periodically quantify the effect of isothermal aging quantitatively on phase coarsening and evolution, in SAC305 (Sn3.0Ag0.5Cu) solder. SAC305 alloy is aged for (24–1000) hours at 100°C (∼ 0.7–0.8Tmelt). The characteristic parameters monitored during isothermal aging include size, volume fraction, and inter-particle spacing of both nanoscale Ag3Sn intermetallic compounds (IMCs) and micronscale Cu6Sn5 IMCs, as well as the volume fraction of pure tin dendrites in SAC305 solder. Effects of above microstructural evolution on secondary creep constitutive response of SAC305 interconnects were modeled using a mechanistic multiscale creep model. The mechanistic phenomena modeled include: (1) dispersion strengthening by coarsened nanoscale Ag3Sn IMCs and reinforcement strengthening by micronscale Cu6Sn5 IMCs, respectively; and (2) load sharing between pure Sn dendrites and the surrounding eutectic Sn-Ag phase. The coarse-grained polycrystalline Sn micro structure in SAC305 solder was not captured in the above model because isothermal aging did not appear to cause any significant change in the initial grain morphology of SAC305 solder joints. The above model is shown to predict the drop in creep resistance due to the influence of isothermal aging on SAC305 solder joints.

scholarly journals Suppression of the Growth of Intermetallic Compound Layers with the Addition of Graphene Nano-Sheets to an Epoxy Sn–Ag–Cu Solder on a Cu Substrate

Materials ◽  
2019 ◽  
Vol 12 (6) ◽  
pp. 936 ◽  
Author(s):  
Min-Soo Kang ◽  
Do-Seok Kim ◽  
Young-Eui Shin
Keyword(s):  
Intermetallic Compound ◽  
Isothermal Aging ◽  
Solder Joints ◽  
Solder Paste ◽  
Shear Tests ◽  
Sac305 Solder ◽  
Epoxy Solder ◽  
The Relationship ◽  
Bonding Characteristics ◽  
Preventive Effects

This study investigated the suppression of the growth of the intermetallic compound (IMC) layer that forms between epoxy solder joints and the substrate in electronic packaging by adding graphene nano-sheets (GNSs) to 96.5Sn–3.0Ag–0.5Cu (wt %, SAC305) solder whose bonding characteristics had been strengthened with a polymer. IMC growth was induced in isothermal aging tests at 150 °C, 125 °C and 85 °C for 504 h (21 days). Activation energies were calculated based on the IMC layer thickness, temperature, and time. The activation energy required for the formation of IMCs was 45.5 KJ/mol for the plain epoxy solder, 52.8 KJ/mol for the 0.01%-GNS solder, 62.5 KJ/mol for the 0.05%-GNS solder, and 68.7 KJ/mol for the 0.1%-GNS solder. Thus, the preventive effects were higher for increasing concentrations of GNS in the epoxy solder. In addition, shear tests were employed on the solder joints to analyze the relationship between the addition of GNSs and the bonding characteristics of the solder joints. It was found that the addition of GNSs to epoxy solder weakened the bonding characteristics of the solder, but not critically so because the shear force was higher than for normal solder (i.e., without the addition of epoxy). Thus, the addition of a small amount of GNSs to epoxy solder can suppress the formation of an IMC layer during isothermal aging without significantly weakening the bonding characteristics of the epoxy solder paste.

Is the Heterogeneous Microstructure of SnAgCu (SAC) Solders Going to Pose a Challenge for Heterogeneous Integration?

2017 ◽  
Author(s):  
Qian Jiang ◽  
Abhishek Deshpande ◽  
Abhijit Dasgupta
Keyword(s):  
Scale Effect ◽  
Solder Joints ◽  
Volume Fraction ◽  
Coarse Grained ◽  
Heterogeneous Integration ◽  
Length Scale ◽  
Dendrite Morphology ◽  
Heterogeneous Microstructure ◽  
Anisotropic Models ◽  
Lower Tier

The coarse heterogeneous microstructure of SAC alloys makes the behavior of interconnections highly sensitive to its geometric length-scale. Heterogeneous integration and the resulting increase in package complexity and miniaturization are making this scale-effect ever more important. This scale effect derives from the anisotropy of tin and the coarse multi-tiered microstructural heterogeneities in SAC solders. As a result, no two joints behave the same and every joint is unique depending on its specific microstructure. Product teams responsible for reliable heterogeneous integration have to ensure that they have adequate methods to deal with this variability. This paper highlights the multi-tiered microstructural morphology in SAC solders due to the solidification and crystallization process. At the highest tier in the joint microstructure are individual (highly anisotropic) grains that can be 100s of microns in size. At the next lower tier the primary heterogeneity is due to individual dendrites of pro-eutectic β tin, that can have lobes as large as 10–20 microns. At the next lower tier the characteristic heterogeneity is a eutectic mix of nanoscale Ag3Sn IMC particles dispersed in a Sn matrix. Researchers have long recognized that the grain morphology is extremely important to mechanical behavior of BGA solder joints because they are coarse-grained (i.e. there may be only a few anisotropic grains in each BGA solder joint). However, heterogeneous integration has now led to joints that are much smaller (less than 100 microns tall), thus making them of the same length-scale as individual tin dendrites within each grain. In other words, there may be just a few dendrites through the thickness of the joint. Unfortunately, very little attention has focused on SAC behavior at such a small length-scale. This study focuses on the effect of the tin-dendrite morphology on the effective behavior of SAC solder joints, using a combination of experiments and multi-tiered anisotropic models that combine dislocation nano-mechanics with composite micromechanics. The volume fraction of β-Sn dendrite within one crystal could vary from 20% to 80%, depending on the time and temperature above the liquidus temperature and the cooling rates. The effects of volume fraction and aspect ratio of Sn dendrites on the anisotropic steady-state creep rate of single crystal SAC specimen are examined. The objective of the study is to provide insights into the role that solder microstructural heterogeneity will play on package reliability in heterogeneous integration.

Effect of Cyclic Damage on the Constitutive Behavior & Microstructure of Sn3.0Ag0.5Cu (SAC305) Solder

2009 ◽  
Vol 1158 ◽  
Author(s):  
Gayatri Cuddalorepatta ◽  
Abhijit Dasgupta
Keyword(s):  
Strain Rate ◽  
Creep Strain ◽  
Room Temperature ◽  
Solder Joints ◽  
Constitutive Behavior ◽  
Secondary Creep ◽  
Sac305 Solder ◽  
Elastic Plastic ◽  
Mechanical Cycling ◽  
Cyclic Damage

AbstractThis study examines the effect of cyclic damage on the constitutive response and microstructural evolution of SAC305 solder. Cyclic damage is induced through isothermal, mechanical cycling tests at high strain rate and room temperature, using modified lap shear microscale specimens (180μm wide solder joint). The properties of interest are elastic, plastic, yield, and viscoplastic material constitutive behavior. In the current study, creep strain accumulation is accommodated when determining the constants, unlike those reported in prior studies [1]. Insights into the evolution of the measured properties are provided by correlating previously reported microstructural grain evolution of microscale SAC305 solder as a function of cyclic damage [2, 3].The hysteresis response and the elastic, plastic and yield measurements from the initial cycles show significant piece-to-piece variability (similar to prior virgin state viscoplastic measurements [3]). The scatter arises since as-reflowed SAC solder joints at length scales of 200μm consist of only a few anisotropic Sn grains that make the joint mechanically inhomogeneous. However, when subject to mechanical cycling fatigue at room temperature these joints undergo grain homogenization due to recrystallization, which is a possible explanation to the drop in scatter with progressing damage. The observed grain evolution is similar to that seen in solder joints under life-cycle loading.The elastic-plastic response and yield strength of SAC305 solder do not show significant contribution from creep deformations at the chosen load levels. The properties degrade with increasing accumulated cyclic damage, at a rate that is proportional to the severity of the cyclic load. The yield stress measurements suggest that SAC305 obeys an independent hardening rule, rather than isotropic or kinematic hardening. The performance of a continuum damage mechanics based model from prior studies in representing the measured degradation in elastic, plastic and yield properties is discussed [4,5].Comparison of the creep behavior of cycled SAC305 specimens (at 50% load drop) with that of uncycled specimens shows that the effective creep compliance and effective secondary creep strain rate increase significantly. As a point of comparison, the creep resistance of cycled SAC305 specimens is even lower than that of as-reflowed Sn37Pb specimens. Similar changes are seen in the stress relaxation behavior. Challenges and limitations of the current studies are included.

Viscoplastic Behavior of Hypo-Eutectic Sn3.0Ag0.5Cu Pb-Free Alloy Under Creep Loading Conditions

2007 ◽  
Author(s):  
Gayatri Cuddalorepatta ◽  
Abhijit Dasgupta
Keyword(s):  
Primary Creep ◽  
Test System ◽  
Creep Model ◽  
Secondary Creep ◽  
Sac305 Solder ◽  
Different Temperatures ◽  
Creep Measurements ◽  
Creep Models ◽  
Future Work ◽  
Creep Loading

The time-dependent viscoplastic behavior of hypoeutectic Sn3.0Ag0.5Cu (SAC305) solder is presented. Mechanical shear tests are conducted at room and high temperatures, using a custom-built thermo-mechanical-microscale (TMM) test system. This test system uses a modified Iosipescu shear specimen with a 180 microns wide solder joint. Creep deformation is measured at constant stress levels between 3 MPa to 20 MPa, at different temperatures. The creep results are fit using Garofalo’s secondary creep model and a generalized exponential primary creep model. Secondary creep measurements from the current work are higher than those reported in literature. Discrepancies in the curve fits based on the chosen continuum creep models are discussed. Possible sources of the discrepancies are discussed. In future work the primary and secondary creep constants measured from this work will be used in viscoplastic finite element models to compare with stress relaxation behavior measured earlier on the TMM specimens at various temperatures and strain levels [1].

scholarly journals Modelling of Creep in Alloys Strengthened by Rod-Shaped Particles: Al-Cu-Mg Age-Hardenable Alloys

Metals ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 930 ◽  
Author(s):  
Chiara Paoletti ◽  
Michael Regev ◽  
Stefano Spigarelli
Keyword(s):  
Grain Size ◽  
Volume Fraction ◽  
Coarse Grained ◽  
Creep Model ◽  
Modified Model ◽  
Physically Based ◽  
Excellent Description ◽  
The Difference ◽  
Temperature Exposure

In recent years, a creep model that does not involve adjustable parameters has been successfully applied to coarse-grained aluminum. The main feature of this model is that it is fully predictable. On the other hand, in the case of age-hardenable alloys, any physically-based creep model should take into account the changes in the volume fraction, size and distribution of strengthening precipitates, and the effect of grain size. With this aim in view, in this paper, the original model previously applied to single phase-alloys has been modified to describe the effects of the grain size and of the consequences of the high-temperature exposure on the strengthening role of precipitates. To this end, phenomenological equations describing the coarsening phenomena and their dependence on the applied stress have been introduced. The modified model has given an excellent description of the experimental behavior of an AA2024-T3 alloy tested at 250 and 315 °C and has provided a sound explanation of the difference observed when comparing the minimum creep rate obtained using two different testing techniques.

Effect of Material Anisotropy on Deformation Behavior of Multiple Grained Sac305 Solder Joints

2021 ◽  
Author(s):  
Debabrata Mondal ◽  
Abdullah Fahim ◽  
KM Rafidh Hassan ◽  
Jeffrey Suhling ◽  
Pradeep Lall
Keyword(s):  
Deformation Behavior ◽  
Solder Joints ◽  
Material Anisotropy ◽  
Sac305 Solder

Determination of Anand Parameters From Creep Testing of Sac305 Solder Joints

2021 ◽  
Author(s):  
Mohammad Ashraful Haq ◽  
Mohd Aminul Hoque ◽  
Jeffrey Suhling ◽  
Pradeep Lall
Keyword(s):  
Solder Joints ◽  
Creep Testing ◽  
Sac305 Solder
Sign in / Sign up

Export Citation Format

Share Document