Nanomechanical Characterization of Aging Effects in Solder Joints in Microelectronic Packaging

2013 ◽  
Author(s):  
Mohammad Hasnine ◽  
Muhannad Mustafa ◽  
Jing Zou ◽  
Jeffrey C. Suhling ◽  
Barton C. Prorok ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Solder Joints ◽  
Bulk Solder ◽  
Lead Free ◽  
Lead Free Solder ◽  
Aging Effects ◽  
Single Grain ◽  
Free Solder ◽  
Aging Phenomena ◽  
Sac Solder

The mechanical properties of a lead free solder are strongly influenced by its microstructure, which is controlled by its thermal history including solidification rate and thermal aging after solidification. Due to aging phenomena, the microstructure, mechanical response, and failure behavior of lead free solder joints in electronic assemblies are constantly evolving when exposed to isothermal and/or thermal cycling environments. Through uniaxial testing of miniature bulk solder tensile specimens, we have previously demonstrated that large changes occur in the stress-strain and creep behaviors of lead free solder alloys with aging. Complementary studies by other research groups have verified aging induced degradations of SAC mechanical properties. In those investigations, mechanical testing was performed on a variety of sample geometries including lap shear specimens, Iosipescu shear specimens, and custom solder ball array shear specimens. While there are clearly aging effects in SAC solder materials, there have been limited prior mechanical loading studies on aging effects in actual solder joints extracted from area array assemblies (e.g. PBGA or flip chip). This is due to the extremely small size of the individual joints, and the difficulty in gripping them and applying controlled loadings (tension, compression, or shear). In the current work, we have explored aging phenomena in actual solder joints by nano-mechanical testing of single SAC305 lead free solder joints extracted from PBGA assemblies. Using nanoindentation techniques, the stress-strain and creep behavior of the SAC solder materials have been explored at the joint scale for various aging conditions. Mechanical properties characterized as a function of aging include the elastic modulus, hardness, and yield stress. Using a constant force at max indentation, the creep response of the aged and non-aged solder joint materials has also been measured as a function of the applied stress level. With these approaches, aging effects in solder joints were quantified and correlated to the magnitudes of those observed in testing of miniature bulk specimens. Our results show that the aging induced degradations of the mechanical properties (modulus, hardness) of single grain SAC305 joints were similar to those seen previously by testing of larger “bulk” solder specimens. However, due to the single grain nature of the joints considered in this study, the degradations of the creep responses were significantly less in the solder joints relative to those in larger uniaxial tensile specimens. The magnitude of aging effects in multi-grain lead free solder joints remains to be quantified. Due to the variety of crystal orientations realized during solidification, it was important to identify the grain structure and crystal orientations in the tested joints. Polarized light microscopy and Electron Back Scattered Diffraction (EBSD) techniques have been utilized for this purpose. The test results show that the elastic, plastic, and creep properties of the solder joints and their sensitivities to aging are highly dependent on the crystal orientation. In addition, an approach has been developed to predict tensile creep strain rates for low stress levels using nanoindentation creep data measured at very high compressive stress levels.

Nanoindentation Measurements of the Mechanical Properties of Individual Phases Within Lead Free Solder Joints Subjected to Isothermal Aging

2018 ◽  
Author(s):  
Abdullah Fahim ◽  
Sudan Ahmed ◽  
Jeffrey C. Suhling ◽  
Pradeep Lall
Keyword(s):  
Mechanical Properties ◽  
Isothermal Aging ◽  
Solder Joints ◽  
Bulk Solder ◽  
Lead Free ◽  
Nanoindentation Test ◽  
Lead Free Solder ◽  
Free Solder ◽  
The Individual ◽  
Sac Solder

Exposure of lead free solder joints to high temperature isothermal aging conditions leads to microstructure evolution, which mainly includes coarsening of the intermetallic (IMC) phases. In our previous work, it was found that the coarsening of IMCs led to degradation of the overall mechanical properties of the SAC solder composite consisting of β-Sn matrix and IMC particles. However, it is not known whether the isothermal aging changes properties of the individual β-Sn and IMC phases, which could also be affecting to the overall degradation of properties. In this study, the aging induced variations of the mechanical properties of the β-Sn phase, and of Sn-Cu IMC particles in SAC solder joints have been explored using nanoindentation. SAC solder joints extracted from SuperBGA (SBGA) packages were aged for different time intervals (0, 1, 5, 10 days) at T = 125 °C. Nanoindentation test samples were prepared by cross sectioning the solder joints, and then molding them in epoxy and polishing them to prepare the joint surfaces for nanoindentation. Multiple β-Sn grains were identified in joints using optical polarized microscopy and IMCs were also observed. Individual β-Sn grains and IMC particles were then indented at room temperature to measure their mechanical properties (elastic modulus and hardness) and time dependent creep deformations. Properties measured at different aging time were then compared to explore aging induced degradations of the individual phases. The properties of the individual phases did not show significant degradation. Thus, IMC coarsening is the primary reason for the degradation of bulk solder joint properties, and changes of the properties of the individual phases making up the lead free solder material are negligible.

Nanoindentation Characterization of Lead-free Solders and Intermetallic Compounds under Thermal Aging

2010 ◽  
Vol 2010 (1) ◽  
pp. 000314-000318
Author(s):  
Tong Jiang ◽  
Fubin Song ◽  
Chaoran Yang ◽  
S. W. Ricky Lee
Keyword(s):  
Mechanical Properties ◽  
Thermal Aging ◽  
Solder Joints ◽  
Lead Free ◽  
Small Range ◽  
Lead Free Solder ◽  
Solder Alloys ◽  
Aging Test ◽  
Free Solder ◽  
Lead Free Solders

The enforcement of environmental legislation is pushing electronic products to take lead-free solder alloys as the substitute of traditional lead-tin solder alloys. Applications of such alloys require a better understanding of their mechanical behaviors. The mechanical properties of the lead-free solders and IMC layers are affected by the thermal aging. The lead-free solder joints on the pads subject to thermal aging test lead to IMC growth and cause corresponding reliability concerns. In this paper, the mechanical properties of the lead-free solders and IMCs were characterized by nanoindentation. Both the Sn-rich phase and Ag3Sn + β-Sn phase in the lead-free solder joint exhibit strain rate depended and aging soften effect. When lead-free solder joints were subject to thermal aging, Young's modulus of the (Cu, Ni)6Sn5 IMC and Cu6Sn5 IMC changed in very small range. While the hardness value decreased with the increasing of the thermal aging time.

Effects of Shear Cycling on the Mechanical Properties of SAC and SAC+X Lead Free Solder Joints

2019 ◽  
Author(s):  
Mohd Aminul Hoque ◽  
Md Mahmudur Chowdhury ◽  
Sa’d Hamasha ◽  
Jeffrey C. Suhling ◽  
Pradeep Lall
Keyword(s):  
Mechanical Properties ◽  
Solder Joints ◽  
Coefficient Of Thermal Expansion ◽  
Real Life ◽  
Material Behavior ◽  
Lead Free ◽  
Lead Free Solder ◽  
Cyclic Shear ◽  
Mechanical Cycling ◽  
Free Solder

Abstract Solder joint reliability is a chief concern in electronic assemblies. Electronic packages consist of various materials, each having their own Coefficient of Thermal Expansion (CTE). When assembled packages experience high temperature gradients and thermal cycles, a mismatch in the CTE values brings about cyclic shear strains in the solder joints, which can ultimately lead to failure. Thus, it is important to understand the effects of shear cycling on the damage accumulated in solder joints. Previous studies conducted on the effect of mechanical cycling on the material behavior of lead free solders have been performed on bulk samples subjected to tension and compression. Our goal in this study was to determine the evolution of the mechanical properties of doped lead free solder joints when subjected to mechanical shear cycling. Experiments conducted on actual solder joints would help us gain a better understanding on the real life effects of shear cycling. The test specimens consisted of a 3 × 3 array of nine solder joints of approximately 0.75 mm diameter. With the aid of specially designed test fixtures, the specimens were gripped and then subjected to mechanical cycling in the shear using an Instron Micromechanical tester. Testing was performed on both SAC305 and SACX (SAC+Bi) solder joints. The joints were cycled for certain durations, and a nanoindentation system was used to measure the evolution of the mechanical properties (elastic modulus, hardness, creep rate) as a function of the number of shear cycles.

Effects of Thermal Cycling on the Mechanical and Microstructural Evolution of SAC305 Lead-Free Solder

2019 ◽  
Author(s):  
S. M. Kamrul Hasan ◽  
Abdullah Fahim ◽  
Jeffrey C. Suhling ◽  
Sa’d Hamasha ◽  
Pradeep Lall
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
High Temperature ◽  
Thermal Cycling ◽  
Microstructural Evolution ◽  
Lead Free ◽  
Lead Free Solder ◽  
Temperature Extreme ◽  
Aging Effects ◽  
Free Solder

Abstract Lead free electronic assemblies are often subjected to thermal cycling during qualification testing or during actual use. The dwell periods at the high temperature extreme during thermal cycling cause thermal aging phenomena in the solder material, including microstructural evolution and material property degradation. In addition, lead free solders can also experience aging effects during the ramp periods between the low and high temperature extremes of the cycling. In this study, the mechanical behavior evolution occurring in SAC305 lead free solder subjected to various thermal cycling exposures has been investigated. Uniaxial test specimens were prepared by reflowing solder in rectangular cross-section glass tubes with a controlled temperature profile. After reflow solidification, the samples were placed into the environmental chamber and thermally cycled from −40 C to +125 C under a stress-free condition (no load). Several thermal cycling profiles were examined including: (1) 90 minute cycles with 15 minutes ramps and 30 minutes dwells, (2) air-to-air thermal shock exposures with 30 minutes dwells and near instantaneous ramps, (3) 30 minute cycles with 15 minutes ramps and no dwells (saw tooth profile), (4) 150 minute cycles with 45 minutes ramps and 30 minutes dwells, and (5) no cycling (simple aging at the high temperature extreme). For each profile, 10–15 samples were cycled for various durations of cycling (e.g. 48, 96, and 240 cycles), which were equivalent to various aging times at the high temperature extreme of T = 125 C. After cycling, the stress-strain curves and mechanical properties including effective elastic modulus and Ultimate Tensile Strength (UTS) of all the cycled samples were measured. For each cycling profile, the evolutions of the mechanical properties were characterized as a function of the cycling duration, as well as the net aging time at the high temperature extreme. Comparison of the results of various thermal cycling profiles showed that the detrimental effects of aging are accelerated in a thermal cycling environment. Furthermore, microstructure evolution during thermal cycling has also been investigated to validate the observed mechanical properties degradation. The test results revealed that the mechanical properties degradation of SAC305 are higher in thermal cycling compared to simple equivalent aging. For example, the elastic modulus and UTS of SAC305 reduced by 41%, and 38%, respectively after 5 days aging whereas these properties reduced by 69%, and 51%, respectively after 5 days equivalent aging using thermal cycling profile #4 (240 cycles).

Isothermal Aging Effects on the Mechanical Shock Performance of Lead-Free Solder Joints

2011 ◽  
Vol 1 (5) ◽  
pp. 714-721 ◽  
Author(s):  
Hongtao Ma ◽  
Tae-Kyu Lee ◽  
Dong Hyun Kim ◽  
H G Park ◽  
Sang Ha Kim ◽  
...  
Keyword(s):  
Isothermal Aging ◽  
Solder Joints ◽  
Lead Free ◽  
Lead Free Solder ◽  
Mechanical Shock ◽  
Aging Effects ◽  
Free Solder

Formation and Mechanical Properties of Intermetallic Compounds in Sn-Cu High-Temperature Lead-Free Solder Joints

2010 ◽  
Vol 654-656 ◽  
pp. 2450-2454 ◽  
Author(s):  
De Kui Mu ◽  
Hideaki Tsukamoto ◽  
Han Huang ◽  
Kazuhiro Nogita
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Intermetallic Compounds ◽  
Solder Joints ◽  
Nickel Content ◽  
Lead Free ◽  
Lead Free Solder ◽  
Nickel Addition ◽  
Free Solder ◽  
Lead Free Solders

High-temperature lead-free solders are important materials for electrical and electronic devices due to increasing legislative requirements that aim at reducing the use of traditional lead-based solders. For the successful use of lead-free solders, a comprehensive understanding of the formation and mechanical properties of Intermetallic Compounds (IMCs) that form in the vicinity of the solder-substrate interface is essential. In this work, the effect of nickel addition on the formation and mechanical properties of Cu6Sn5 IMCs in Sn-Cu high-temperature lead-free solder joints was investigated using Scanning Electron Microscopy (SEM) and nanoindentation. It was found that the nickel addition increased the elastic modulus and hardness of the (Cu, Ni)6Sn5. The relationship between the nickel content and the mechanical properties of the IMCs was also established.

Effects of Recycled-Aluminum Additions on the Mechanical Properties of Sn-0.7Cu/Cu-Substrate Lead-Free Solder Joints

2013 ◽  
Vol 795 ◽  
pp. 446-450 ◽  
Author(s):  
Mohd Arif Anuar Mohd Salleh ◽  
Flora Somidin ◽  
Mohd Mustafa Al Bakri Abdullah ◽  
N.Z. Noriman ◽  
Ramani Mayappan ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Solder Joints ◽  
Lead Free ◽  
Lead Free Solder ◽  
Powder Metallurgy Technique ◽  
Cu Substrate ◽  
Base Matrix ◽  
Free Solder ◽  
Al Additions ◽  
Scanning Electron

Varying amount of recycled-Aluminum (0, 3.0, 3.5 and 4.0 wt.% re-Al) particulates produced from aluminium beverage cans were successfully reincorporated into Sn-0.7Cu base matrix solder material via powder metallurgy technique. This paper focuses on the mechanical properties aspect of the new solder when joint on Cu-substrate. The hardness of the composite solders sintered bulks was enhanced with the increasing re-Al additions. Moreover, the composite solders have shown enhancement of shear stress strength at the solder joints. Fracture surface of the failure samples were analyzed using scanning electron microscope (SEM) which have indicated all samples failed under ductile fracture mechanism. However, with the refining dimples formation shown on the fractograph, this report suggests the increasing re-Al reinforcement has optimized the solder joints ductility strength.

Isothermal Aging Effects on the Thermal reliability Performance of Lead-Free Solder Joints

2012 ◽  
Vol 2012 (1) ◽  
pp. 000801-000808 ◽  
Author(s):  
Jiawei Zhang ◽  
Zhou Hai ◽  
Sivasubramanian Thirugnanasambandam ◽  
John L. Evans ◽  
M. J. Bozack
Keyword(s):  
Elevated Temperature ◽  
Isothermal Aging ◽  
Elevated Temperatures ◽  
Solder Joints ◽  
Bulk Solder ◽  
Lead Free ◽  
Aging Effects ◽  
Thermal Reliability ◽  
Free Solder ◽  
The Impact

Electronics assemblies containing solder joints are often exposed to elevated temperatures for prolonged periods of time. The time-at-temperature stress impacts the overall package reliability of the assembled circuitry due to evolving materials, microstructural, and mechanical properties. It is especially important to understand the impact of isothermal aging on the long term behavior of lead (Pb)-free solder joints which operate in harsh environments. In this study, we have explored the effects of elevated temperature isothermal aging on the reliability of Sn-Ag-Cu (SAC) assemblies on board level packages. As the isothermal aging temperature increases, the Weybull characteristic lifetime for SAC 105 and 305 solder joints is drastically reduced compared to Sn-37Pb.In parallel mechanical studies on bulk solder specimens, the creep rate for SAC105, 305 rapidly increases with aging. A full test matrix with varying aging temperatures and solder alloys was considered. Package sizes ranged from 19mm, 0.8mm pitch ball grid arrays (BGAs) to 5mm, 0.4mm pitch μBGAs. The test structures were built on three different board finishes (ImSn, ImAg and SnPb). Storage condition temperatures were 25°C, 55°C, 85°C and 125°C with aging over time periods of 0, 6, and 12 months. Subsequently, the specimens were thermally cycled from −40°C to 125°C with 15 min dwell times at the high temperature. It was found that the thermal performance of lead-free fine-pitch packages significantly degrades up to 55–60% after aging at elevated temperature. The dominant failure mode can be associated with the growth of Cu6Sn5 intermetallic compounds (IMC) during the aging, particularly on the pad side.

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