Influence of microstructure inhomogeneity on the current density and temperature gradient in microscale line-type Sn58Bi solder joints under current stressing

Adopting an accurate micro-tensile method based on dynamic mechanical analyzer (DMA) instrument, the tensile strength of three kinds of copper-wire/solder/copper-wire sandwich structured microscale lead-free solder joints that underwent current stressing with a direct current density of 1.0×104 A/cm2 and loading time of 48 hours were investigated, and compared with those solder joints isothermal aged at 100 0C for 48 hours and as-reflowed condition. These three kinds of microscale columnar solder joints have different volumes, i.e., a same diameter of 300 μm but different heights of 100 μm, 200 μm and 300 μm. Experimental results show that both current stressing and isothermal aging degrades the tensile strength of microscale solder joints, and the solder joint with smaller volume obtains higher tensile strength under same test condition. In addition, current stressing induces obvious electromigration (EM) issue under high current density of 1.0×104 A/cm2, resulting in the decreasing of tensile strength and different fracture position, mode and surface morphology of microscale solder joints. The degree of strength degradation increases with the increasing of joint height when keep joint diameter constant, this is mainly due to that electromigration leads to voids form and grow at the interface of cathode, and solder joints with larger volume may contains more soldering defects as well.

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Three-dimensional simulation on current-density distribution in flip-chip solder joints under electric current stressing

Journal of Applied Physics ◽

10.1063/1.2000667 ◽

2005 ◽

Vol 98 (4) ◽

pp. 044509 ◽

Cited By ~ 43

Author(s):

T. L. Shao ◽

S. W. Liang ◽

T. C. Lin ◽

Chih Chen

Keyword(s):

Density Distribution ◽

Electric Current ◽

Current Density ◽

Flip Chip ◽

Solder Joints ◽

Three Dimensional ◽

Current Density Distribution ◽

Current Stressing ◽

Dimensional Simulation

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Electromigration Reliability With Respect to Cu Weight Contents of Sn–Ag–Cu Flip-Chip Solder Joints Under Comparatively Low Current Stressing

Journal of Electronic Packaging ◽

10.1115/1.2957325 ◽

2008 ◽

Vol 130 (4) ◽

Cited By ~ 3

Author(s):

Yi-Shao Lai ◽

Ying-Ta Chiu

Keyword(s):

Intermetallic Compound ◽

Ambient Temperature ◽

Current Density ◽

Flip Chip ◽

Solder Joints ◽

Average Current Density ◽

Current Stressing ◽

Weight Content ◽

Average Current ◽

Better Than

This work presents electromigration reliability and patterns of Sn–3Ag–0.5Cu and Sn–3Ag–1.5Cu∕Sn–3Ag–0.5Cu composite flip-chip solder joints with Ti∕Ni(V)∕Cu under bump metallurgy (UBM), bonded on Au∕Ni∕Cu substrate pads. The solder joints were subjected to an average current density of 5kA∕cm2 under an ambient temperature of 150°C. Under the situation when electron charges flow from the UBM toward the substrate, Sn diffuses from the Cu–Ni–Sn intermetallic compound developed around the UBM toward the UBM and eventually causes the Ni(V) layer to deform. Electromigration reliability of Sn–3Ag–1.5Cu∕Sn–3Ag–0.5Cu composite flip-chip solder joints was found to be better than that of Sn–3Ag–0.5Cu solder joints. According to the morphological observations on cross-sectioned solder joints, a failure mechanism is proposed as follows. Since the deformation of the Ni(V) layer as a result of Sn diffusion toward the UBM is considered as the dominant failure, a greater Cu weight content in the solder joints would trap more Sn in the Sn–Cu interfacial reaction and would therefore retard the diffusion of Sn toward the UBM and hence enhance the electromigration reliability.

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Abnormal Shear Performance of Microscale Ball Grid Array Structure Cu/Sn–3.0Ag–0.5Cu/Cu Solder Joints with Increasing Current Density

Crystals ◽

10.3390/cryst12010085 ◽

2022 ◽

Vol 12 (1) ◽

pp. 85

Author(s):

Bo Wang ◽

Wangyun Li ◽

Kailin Pan

Keyword(s):

Shear Strength ◽

Critical Current Density ◽

Joule Heating ◽

Current Density ◽

Solder Joints ◽

Solder Matrix ◽

Ball Grid Array ◽

Current Stressing ◽

Shear Performance ◽

Array Structure

The shear performance and fracture behavior of microscale ball grid array structure Cu/Sn–3.0Ag–0.5Cu/Cu solder joints with increasing electric current density (from 1.0 × 103 to 6.0 × 103 A/cm2) at various test temperatures (25 °C, 55 °C, 85 °C, 115 °C, 145 °C, and 175 °C) were investigated systematically. Shear strength increases initially, then decreases with increasing current density at a test temperature of no more than 85 °C; the enhancement effect of current stressing on shear strength decreases and finally diminishes with increasing test temperatures. These changes are mainly due to the counteraction of the athermal effect of current stressing and Joule heating. After decoupling and quantifying the contribution of the athermal effect to the shear strength of solder joints, the results show that the influence of the athermal effect presents a transition from an enhancement state to a deterioration state with increasing current density, and the critical current density for the transition decreases with increasing test temperatures. Joule heating is always in a deterioration state on the shear strength of solder joints, which gradually becomes the dominant factor with increasing test temperatures and current density. In addition, the fracture location changes from the solder matrix to the interface between the solder matrix and the intermetallic compound (IMC) layer (the solder/IMC layer interface) with increasing current density, showing a ductile-to-brittle transition. The interfacial fracture is triggered by current crowding at the groove of the IMC layer and driven by mismatch strain at the solder/IMC layer interface, and the critical current density for the occurrence of interfacial fracture decreases with increasing test temperatures.

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Phase field study of the combined effects of electromigration and thermomigration on phase segregation and physical properties of Sn58Bi solder joints under electric current stressing coupled with temperature gradient

2018 19th International Conference on Electronic Packaging Technology (ICEPT) ◽

10.1109/icept.2018.8480529 ◽

2018 ◽

Author(s):

Shui-Bao Liang ◽

Chang-Bo Ke ◽

Cheng Wei ◽

Min-Bo Zhou ◽

Xin-Ping Zhang

Keyword(s):

Temperature Gradient ◽

Physical Properties ◽

Field Study ◽

Electric Current ◽

Phase Field ◽

Solder Joints ◽

Phase Segregation ◽

Combined Effects ◽

Current Stressing

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Thermal Gradient in Solder Joints Under Electrical Current Stressing

Advances in Electronic Packaging, Parts A, B, and C ◽

10.1115/ipack2005-73356 ◽

2005 ◽

Author(s):

Da-Jeng Yao ◽

Chung-Yi Hsu ◽

Chih Chen ◽

Sheng-Hsiang Chiu

Keyword(s):

Current Density ◽

Thermal Gradient ◽

Solder Joints ◽

High Current Density ◽

Thermal Characteristic ◽

Electrical Current ◽

Measured Temperature ◽

Applied Current ◽

Finite Element Software ◽

Current Stressing

Thermal gradient phenomena in SnAg3.5 solder joints under high current density operating were both acquired from whole device simulation and observed from experiments. A series of structural solder bump models were created and simulated by finite element software under different current density. The thermal gradient and temperature increasing were investigated under current stressing of 103 A/cm2 to 104 A/cm2 at 70°C by infrared microscopy. The magnitude of the thermal gradient is increased by increasing the applied current. The measured temperature increase due to Joule heating is as high as 55.9°C, and the thermal gradient reached 333°C/cm when stressed by 104 A/cm2, yet only 8.3°C temperature increased and the thermal gradient reached 83°C/cm when stressed by 103 A/cm2. The temperature increasing in this model is 53.1°C and thermal gradient in the solder is 168°C/cm under 104 A/cm2 current stressing, yet only 10.4°C temperature increased and thermal gradient decreased to 35°C/cm under 103 A/cm2. After verification, only less than 0.5% error is achieved between simulation results and experiment results. It proves this built model can be used to project thermal characteristic of different module designs.

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