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.

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 in Solder Joints for High Temperature Flip-Chip Application

2011 ◽  
Vol 2011 (DPC) ◽  
pp. 002481-002506
Author(s):  
Mathias Nowottnick ◽  
Andreas Fix
Keyword(s):  
High Temperature ◽  
Current Density ◽  
Flip Chip ◽  
Solder Joints ◽  
Metallographic Analysis ◽  
Solder Alloys ◽  
Directed Movement ◽  
Cross Sectional ◽  
Current Densities ◽  
And Migration

The electromigration effects in chip metallization and wire bonds are well known and detailed investigated. Current density could be extremely high because of the small size of the cross sectional area of conductors. This can cause a migration of metal atoms toward the electrical field, so current densities up to 106 A/cm2 are possible. In comparison with chip structures are the usual solder joints of flip chips relatively thick. But the homologue temperature of solder alloys, typically based on tin, is also much higher than for gold or aluminum wires. For instance a SAC solder alloy is naturally preheated up to 0.6 homologue temperature, for high temperature application with 125 °C operating temperature even more than 0.8. This means, that atoms are very agile and a directed movement needs only lower field strength. Additionally is the specific resistance of solder alloys tenfold higher than for aluminum, copper or silver. So is the self-heating of solder joints not negligible. This contribution shows the test results of flip-chip assemblies, loaded with different current densities and stored at 125 °C ambient temperature. At the end of life of a significant number of test chips, a metallographic analysis shows the causing failure effects and weak spots of assemblies. Accompanying simulations help to explain the interaction between current density and migration effects.

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

Direct Measurement of Hot-spot Temperature in Flip-chip Solder Joints With Cu Columns Under Current Stressing using Infrared Microscopy

2010 ◽  
Vol 1249 ◽  
Author(s):  
Chih Chen ◽  
Yu Chun Liang ◽  
D. J. Yao
Keyword(s):  
Thin Layer ◽  
Flip Chip ◽  
Solder Bump ◽  
Hot Spot ◽  
Infrared Microscopy ◽  
Column Temperature ◽  
Current Stressing ◽  
Large Current ◽  
Spot Temperature ◽  
A Current

AbstractIn this study, the temperature map distribution in the Sn3.0Ag0.5Cu solder bump with Cu column under current stressing is directly examined using infrared microscopy. It is the radiance changes between the different materials of the surface that cause the unreasonable temperature map distribution. By coating a thin layer of black optical paint which is in order to eliminate the radiance changes, we got the corrected temperature map distribution. Under a current stress of 1.15 × 104 A/cm2 at 100℃C, the hot-spot temperature is 132.2℃ which surpasses the average Cu column temperature of 129.7℃C and the average solder bump temperature of 127.4 ℃. Thermomigration in solder may still occur under a large current stressing.

Influence of Duty Cycle on Composition and Microstructure of Siliconized Layer Using Pulse Electrodeposition

2010 ◽  
Vol 139-141 ◽  
pp. 666-669 ◽  
Author(s):  
Hai Li Yang ◽  
Yan Li ◽  
Yun Gang Li ◽  
Guo Zhang Tang ◽  
Ning He ◽  
...  
Keyword(s):  
Duty Cycle ◽  
Molten Salts ◽  
Layer Structure ◽  
Silicon Steel ◽  
Average Current Density ◽  
Cross Sectional ◽  
Columnar Grains ◽  
Average Current ◽  
Si Content ◽  
Equiaxed Grains

The siliconized layer was pulse electrodeposited on grain oriented low-silicon steel sheet substrate in KCl-NaCl-NaF-SiO2 molten salts and the influence of duty cycle on the composition and microstructure of the siliconized layer was investigated. The results showed that when the duty cycle was in the range of 10% to 50% at average current density 30mA/cm2, Si content of siliconized layers was similar and the thickness of the layer was did not change much with different duty cycle. Cross sectional observation revealed that the siliconized layers had a two-layer structure. The top layer composed of columnar grains and a transition layer with equiaxed grains was close to the substrate. The layer was unsmooth when the duty cycle was 10%. While the surface appeared smooth and dense and the grains were fine when the duty cycle were 20% and 30%. The layer became more porous as the duty cycle increased to 40% and 50%.

Effect of hourglass shape solder joints on underfill encapsulation process: numerical and experimental studies

2020 ◽  
Vol 32 (3) ◽  
pp. 147-156
Author(s):  
Muhammad Naqib Nashrudin ◽  
Zhong Li Gan ◽  
Aizat Abas ◽  
M.H.H. Ishak ◽  
M. Yusuf Tura Ali
Keyword(s):  
Solder Joint ◽  
Numerical Method ◽  
Flip Chip ◽  
Solder Joints ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Cross Sectional ◽  
Content Type ◽  
Filling Time ◽  
Encapsulation Process

Purpose In line with the recent development of flip-chip reliability and underfill process, this paper aims to comprehensively investigate the effect of different hourglass shape solder joint on underfill encapsulation process by mean of experimental and numerical method. Design/methodology/approach Lattice Boltzmann method (LBM) numerical was used for the three-dimensional simulation of underfill process. The effects of ball grid arrays (BGA) encapsulation process in terms of filling time of the fluid were investigated. Experiments were then carried out to validate the simulation results. Findings Hourglass shape solder joint has shown the shortest filling time for underfill process compared to truncated sphere. The underfill flow obtained from both simulation and experimental results are found to be in good agreement for the BGA model studied. The findings have also shown that the filling time of Hourglass 2 with parabolic shape gives faster filling time compared to the Hourglass 1 with hemisphere angle due to bigger cross-sectional area of void between the solder joints. Practical implications This paper provides reliable insights to the effect of hourglass shape BGA on the encapsulation process that will benefit future development of BGA packages. Originality/value LBM numerical method was implemented in this research to study the flow behaviour of an encapsulation process in term of filling time of hourglass shape BGA. To date, no research has been found to simulate the hourglass shape BGA using LBM.

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