In-situ observation of material migration in flip-chip solder joints under current stressing

2006 ◽  
Vol 35 (10) ◽  
pp. 1781-1786 ◽  
Author(s):  
C. M. Tsai ◽  
Yi-Shao Lai ◽  
Y. L. Lin ◽  
C. W. Chang ◽  
C. R. Kao
Keyword(s):  
Flip Chip ◽  
Solder Joints ◽  
In Situ Observation ◽  
Current Stressing ◽  
Material Migration

scholarly journals The In-Situ Observation of Grain Rotation and Microstructure Evolution Induced by Electromigration in Sn-3.0Ag-0.5Cu Solder Joints

Materials ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 5497
Author(s):  
Xing Fu ◽  
Min Liu ◽  
KeXin Xu ◽  
Si Chen ◽  
YiJun Shi ◽  
...  
Keyword(s):  
Solder Joints ◽  
Flow Direction ◽  
Electron Flow ◽  
Critical Role ◽  
In Situ Observation ◽  
Fast Diffusion ◽  
Electron Backscattered Diffraction ◽  
Grain Rotation ◽  
Current Stressing

The in-situ observation of Sn-3.0Ag-0.5Cu solder joints under electromigration was conducted to investigate the microstructure and grain orientation evolution. It was observed that there was a grain rotation phenomenon during current stressing by in-situ electron backscattered diffraction (EBSD). The rotation angle was calculated, which indicated that the grain reorientation led to the decrease of the resistance of solder joints. On the other hand, the orientation of β-Sn played a critical role in determining the migration of Cu atoms in solder joints under current stressing migration. When the angle between the electron flow direction and the c-axis of Sn (defined as α) was close to 0°, massive Cu6Sn5 intermetallic compounds were observed in the solder bulk; however, when α was close to 90°, the migration of the intermetallic compound (IMC) was blocked but many Sn hillocks grew in the anode. Moreover, the low angle boundaries were the fast diffusion channel of Cu atoms while the high grain boundaries in the range of 55°–65° were not favorable to the fast diffusion of Cu atoms.

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

2008 ◽  
Vol 130 (4) ◽  
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.

Electromigration Reliability of 96.5Sn–3Ag–0.5Cu Flip-Chip Solder Joints With Au/Ni/Cu or Cu Substrate Pad Metallization

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Yi-Shao Lai ◽  
Ying-Ta Chiu ◽  
Chiu-Wen Lee
Keyword(s):  
Flip Chip ◽  
Solder Joints ◽  
Average Current Density ◽  
Cross Sectional ◽  
Cu Substrate ◽  
Cu Metallization ◽  
Substrate Side ◽  
Current Stressing ◽  
Average Current ◽  
A Current

Designed experiments were conducted in this paper to study the effect of Au/Ni/Cu or Cu substrate pad metallization on the electromigration reliability of 96.5Sn–3Ag–0.5Cu flip-chip solder joints with Ti/Ni(V)/Cu under bump metallurgy (UBM) under a current stressing condition with an average current density of around 5 kA/cm2 at an ambient temperature of 150°C. Cross-sectional observations on current-stressed solder joints indicate that although Cu metallization results in severe voiding compared with Au/Ni/Cu metallization on the substrate side of the solder joint, the dominant failure has been identified as UBM consumption, and test vehicles with Cu metallization exhibit better electromigration reliability than those with Au/Ni/Cu metallization. The stronger durability against current stressing for test vehicles with Cu metallization may attribute to the lower UBM consumption rate due to the continuous Cu diffusion toward UBM as a result of the concentration gradient. The consumption of UBM is faster for test vehicles with Au/Ni/Cu metallization because Cu diffusion from the substrate pad is retarded by the Ni barrier.

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