Abnormal phase segregation induced by void formation in Cu/Sn-58Bi/Cu solder joint during current stressing

2012 ◽  
Author(s):  
Hongwen He ◽  
Guangchen Xu ◽  
Fu Guo
Keyword(s):  
Solder Joint ◽  
Void Formation ◽  
Phase Segregation ◽  
Current Stressing

A study on the effects of electrical and thermal stresses on void formation and migration lifetime of Sn3.0Ag0.5Cu solder joints

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Yanruoyue Li ◽  
Guicui Fu ◽  
Bo Wan ◽  
Zhaoxi Wu ◽  
Xiaojun Yan ◽  
...  
Keyword(s):  
Solder Joint ◽  
Thermal Stresses ◽  
Solder Joints ◽  
Void Formation ◽  
Model Parameters ◽  
Time To Failure ◽  
Current Crowding ◽  
Theoretical Derivation ◽  
Content Type ◽  
And Migration

Purpose The purpose of this study is to investigate the effect of electrical and thermal stresses on the void formation of the Sn3.0Ag0.5Cu (SAC305) lead-free ball grid array (BGA) solder joints and to propose a modified mean-time-to-failure (MTTF) equation when joints are subjected to coupling stress. Design/methodology/approach The samples of the BGA package were subjected to a migration test at different currents and temperatures. Voltage variation was recorded for analysis. Scanning electron microscope and electron back-scattered diffraction were applied to achieve the micromorphological observations. Additionally, the experimental and simulation results were combined to fit the modified model parameters. Findings Voids appeared at the corner of the cathode. The resistance of the daisy chain increased. Two stages of resistance variation were confirmed. The crystal lattice orientation rotated and became consistent and ordered. Electrical and thermal stresses had an impact on the void formation. As the current density and temperature increased, the void increased. The lifetime of the solder joint decreased as the electrical and thermal stresses increased. A modified MTTF model was proposed and its parameters were confirmed by theoretical derivation and test data fitting. Originality/value This study focuses on the effects of coupling stress on the void formation of the SAC305 BGA solder joint. The microstructure and macroscopic performance were studied to identify the effects of different stresses with the use of a variety of analytical methods. The modified MTTF model was constructed for application to SAC305 BGA solder joints. It was found suitable for larger current densities and larger influences of Joule heating and for the welding ball structure with current crowding.

Effects of Fe on the Kirkendall Void Formation of Sn-3.5Ag-xFe/Cu Solder Joints

2010 ◽  
Vol 2010 (1) ◽  
pp. 000294-000297 ◽  
Author(s):  
S. H. Kim ◽  
Jin Yu
Keyword(s):  
Solder Joint ◽  
Solder Joints ◽  
Void Formation ◽  
Kirkendall Void ◽  
Fe Content ◽  
Kirkendall Voids

Ternary Sn-3.5Ag-xFe solders with varying amount of Fe; 0.1, 0.5, 1.0, and 2.0 wt. % were reacted with Cu UBM which was electroplated using SPS additive and characteristics of Kirkendall void formation at the solder joints were investigated. Results indicate that the propensity to form Kirkendall voids at the solder joint decreased with the Fe content. It showed that Fe dissolved in the Cu UBM and reduced the segregation of S atoms to the Cu3Sn/Cu interface, which suppressed the nucleation of Kirkendall voids at the interface.

Effects of electromigration on the growth of intermetallic compounds in Cu/SnBi/Cu solder joints

2008 ◽  
Vol 23 (10) ◽  
pp. 2591-2596 ◽  
Author(s):  
X. Gu ◽  
D. Yang ◽  
Y.C. Chan ◽  
B.Y. Wu
Keyword(s):  
Activation Energy ◽  
Solder Joint ◽  
Intermetallic Compounds ◽  
Direct Current ◽  
Solder Joints ◽  
Cathode Side ◽  
Anode Side ◽  
Kinetics Parameters ◽  
Ambient Temperatures ◽  
Current Stressing

In this study, the effects of electromigration (EM) on the growth of Cu–Sn intermetallic compounds (IMCs) in Cu/SnBi/Cu solder joints under 5 × 103 A/cm2 direct current stressing at 308, 328, and 348 K were investigated. For each Cu/SnBi/Cu solder joint under current stressing, the IMCs at the cathode side grew faster than that at the anode side. The growth of these IMCs at the anode side and the cathode side were enhanced by electric current. The growth of these IMCs at the cathode followed a parabolic growth law. The kinetics parameters of the growth of the IMCs were calculated from the thickness data of the IMCs at the cathode side at different ambient temperatures. The calculated intrinsic diffusivity (D0) of the Cu–Sn IMCs was 9.91 × 10−5 m2/s, and the activation energy of the growth of the total Cu–Sn IMC layer was 89.2 kJ/mol (0.92 eV).

Performance of 96.5Sn–3Ag–0.5Cu/fullerene composite solder under isothermal ageing and high-current stressing

2020 ◽  
Vol 33 (1) ◽  
pp. 35-46 ◽  
Author(s):  
Guang Chen ◽  
Xinzhan Cui ◽  
Yaofeng Wu ◽  
Wei Li ◽  
Fengshun Wu
Keyword(s):  
Solder Joint ◽  
Composite Solder ◽  
Solder Joints ◽  
Experimental Results ◽  
High Current ◽  
Sac305 Solder ◽  
Content Type ◽  
Interfacial Imcs ◽  
Current Stressing ◽  
Isothermal Ageing

Purpose The purpose of this paper is to investigate the effect of fullerene (FNS) reinforcements on the microstructure and mechanical properties of 96.5Sn3Ag0.5Cu (SAC305) lead-free solder joints under isothermal ageing and electrical-migration (EM) stressing. Design/methodology/approach In this paper, SAC305 solder alloy doped with 0.1 Wt.% FNS was prepared via the powder metallurgy method. A sandwich-like sample and a U-shaped sample were designed and prepared to conduct an isothermal ageing test and an EM test. The isothermal ageing test was implemented under vacuum atmosphere at 150°C, whereas the EM experiment was carried out with a current density of 1.5 × 104 A/cm2. The microstructural and mechanical evolutions of both plain and composite solder joints after thermal ageing and EM stressing were comparatively studied. Findings A growth of Ag3Sn intermetallic compounds (IMCs) in solder matrix and Cu-Sn interfacial IMCs in composite solder joints was notably suppressed under isothermal ageing condition, whereas the hardness and shear strength of composite solder joints significantly outperformed those of non-reinforced solder joints throughout the ageing period. The EM experimental results showed that for the SAC305 solder, the interfacial IMCs formulated a protrusion at the anode after 360 h of EM stressing, whereas the surface of the composite solder joint was relatively smooth. During the stressing period, the interfacial IMC on the anode side of the plain SAC305 solder showed a continuous increasing trend, whereas the IMC at the cathode presented a decreasing trend for its thickness as the stressing time increased; after 360 h of stressing, some cracks and voids had formed on the cathode side. For the SAC305/FNS composite solder, a continuous increase in the thickness of the interfacial IMC was found on both the anode and cathode sides; the growth rate of the interfacial IMC at the anode was higher than that at the cathode. The nanoindentation results showed that the hardness of the SAC305 solder joint presented a gradient distribution after EM stressing, whereas the hardness data showed a relatively homogeneous distribution in the SAC305/FNS solder joint. Originality/value The experimental results showed that the FNS reinforcement could effectively mitigate the failure risk in solder joints under isothermal ageing and high-current stressing. Specifically, the FNS particles in solder joints can work as a barrier to suppress the diffusion and migration of Sn and Cu atoms. In addition, the nanoidentation results also indicated that the addition of the FNS reinforcement was very helpful in maintaining the mechanical stability of the solder joint. These findings have provided a theoretical and experimental basis for the practical application of this novel composite solder with high-current densities.

Lead-Free Solder/Gold Metallization Interdiffusion in Electronic Interconnects – Challenges and their Control

2008 ◽  
Author(s):  
Nausha Asrar
Keyword(s):  
Solder Joint ◽  
Coefficient Of Thermal Expansion ◽  
Void Formation ◽  
Lead Free ◽  
Gold Content ◽  
Lead Free Solder ◽  
Whisker Formation ◽  
Tin Whisker ◽  
Free Solder ◽  
Gold Metallization

Abstract While considerable amount of researches and investigations have been made on lead-free solder joint reliability, limited number of literatures are available on the effect of gold content on lead-free solder joint performance. The challenges of lead-free solder/gold metallization interdiffusion during high temperature application/test are: gold embrittlement, intermetallics growth, void formation, and tin-whisker formation. Tin whiskers causing system failures in earth and space-based applications have been reported. This paper illustrates a few case histories of such challenges. The results confirmed that the synergistic effects of void formation, intermetallic compounds formation due to the thick gold plating, and coefficient of thermal expansion mismatch between organic and ceramic substrates resulted in brittle fracture of the solder joint. The tin whisker formation was attributed to the compressive stress in the tin solder material, which was caused by diffusion of the end-cap metallization, formation of intermetallics, and thermal cycling of the soldered components.

Electro-migration behavior of Pb-free Flip Chip Bumps

2006 ◽  
Vol 3 (1) ◽  
pp. 32-36 ◽  
Author(s):  
Riet Labie ◽  
Tomas Webers ◽  
Bart Swinnen ◽  
Eric Beyne
Keyword(s):  
Solder Joint ◽  
Flip Chip ◽  
Void Formation ◽  
Test Structure ◽  
Strong Impact ◽  
Migration Behavior ◽  
Resistance Change ◽  
Solder Material ◽  
Free Solder ◽  
The Stability

Most reliability studies, carried out for characterising new Pb-free solder material, put main focus on the thermal-mechanical behaviour of the solder joints. However, it is seen that electro-migration has a big impact on the intermetallic formation between the pad finish (UBM) and the solder material. Electro-migration therefore has a strong impact on the stability and reliability of the joint. A special test structure for flip chip electro-migration has been developed and applied to a CuNiAu – Sn – CuNiAu solder joint. This novel test structure not only monitors the resistance change of the whole bump stack but also allows separating resistance changes at each side (anodic and cathodic) of the bump. It is noticed that at the cathodic UBM, which is the UBM where the electrons enter the solder joint, the UBM consumption is significantly faster than at the anodic side or at a thermal reference bump. It also results in void formation at the cathode which leads to an accelerated failure.

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