Effect of three-dimensional current and temperature distributions on void formation and propagation in flip-chip solder joints during electromigration

2006 ◽  
Vol 89 (2) ◽  
pp. 022117 ◽  
Author(s):  
S. W. Liang ◽  
Y. W. Chang ◽  
T. L. Shao ◽  
Chih Chen ◽  
K. N. Tu
Keyword(s):  
Flip Chip ◽  
Solder Joints ◽  
Three Dimensional ◽  
Void Formation ◽  
Temperature Distributions

Study of void formation due to electromigration in flip-chip solder joints using Kelvin bump probes

2006 ◽  
Vol 89 (3) ◽  
pp. 032103 ◽  
Author(s):  
Y. W. Chang ◽  
S. W. Liang ◽  
Chih Chen
Keyword(s):  
Flip Chip ◽  
Solder Joints ◽  
Void Formation

Experimental Study of Void Formation in High-Lead Solder Joints of Flip-Chip Assemblies

2004 ◽  
Vol 127 (2) ◽  
pp. 120-126 ◽  
Author(s):  
Daijiao Wang ◽  
Ronald L. Panton
Keyword(s):  
Flip Chip ◽  
Solder Joints ◽  
Numerical Study ◽  
Void Formation ◽  
Middle Layer ◽  
Molten Solder ◽  
Previous Theory ◽  
Solder Interconnects ◽  
Heating Profiles ◽  
High Lead

Understanding the formation of voids in solder joints is important for predicting the long-term reliability of solder interconnects. This paper reports experimental research on the formation of void bubbles within molten solder bumps in flip-chip connections. For flip-chip-soldered electronic components, which have small solder volume, voids can be more detrimental to reliability. A previous theory based on thermocapillary flow reveals that the direction of heating influences void formation. Using different heating profiles, 480 solder joints of flip-chip assemblies were processed. A high-lead 90Pb∕8Sn∕2Ag solder was employed in the experiments. The solder samples were microsectioned to determine the actual size or diameter of the voids. A database on sizes and locations of voids was then constructed. More defective bumps, 80%, and higher void volume were found when the solder was melted from top (flip-chip side) to bottom (test board side). The observation on cases with melting direction from bottom to top had 40% defective bumps. The results show that a single big void is near the solder bump center with a few small voids near the edge. This supports the numerical study based on the thermocapillary theory. When the melting direction was reversed, many small voids appear near the edge. Big and middle-size voids tend to stay in the middle and outer regions from top towards middle layer of the bump. This experimental finding does not completely agree with the interpretation on the formation of voids by thermocapillary theory, however, the results do show that heat flux direction plays significant role in the formation and distribution of void bubbles in molten solder.

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.

A Procedure for Automated Shape and Life Prediction in Flip-Chip and BGA Solder Joints

1996 ◽  
Vol 118 (3) ◽  
pp. 127-133 ◽  
Author(s):  
G. Subbarayan
Keyword(s):  
Finite Element ◽  
Solder Joint ◽  
Life Prediction ◽  
Flip Chip ◽  
Solder Joints ◽  
Three Dimensional ◽  
Reliability Estimation ◽  
Element Mesh ◽  
Shape Prediction ◽  
Dimensional Finite Element

In this paper, a three-dimensional shape prediction model and a finite element solution procedure for flip-chip and BGA solder joints are developed. The developed system is capable of calculating the solder joint geometry and the fatigue life automatically without any intervention from the user. The automation achieved will enable fast reliability estimation and improved accuracy, since the two-dimensional finite element mesh used for solder shape prediction is used to generate the three-dimensional finite element mesh for stress analysis. The implementation of the procedure is verified using the solution for a flip-chip joint from literature, and the capability of the code is demonstrated on a hypothetical three-dimensional solder joint with square pads that are rotated with respect to each other, and offset from each other. The system developed in the study represents the first instance of an integrated, automated finite element procedure for both shape and fatigue life prediction in general three-dimensional solder joints. The automation achieved in the system enables fast reliability estimation in a design environment, and the optimal design of flip-chip and BGA solder joint configurations for maximum life.

The Nature of Centroidal Locus in Misaligned Flip-Chip Solder Joints

1997 ◽  
Vol 119 (3) ◽  
pp. 156-162
Author(s):  
G. Subbarayan ◽  
A. Deshpande
Keyword(s):  
Solder Joint ◽  
Cross Sections ◽  
Flip Chip ◽  
Solder Joints ◽  
Three Dimensional ◽  
Diameter Ratio ◽  
Straight Line ◽  
Dimensional Models ◽  
The Cross ◽  
Three Dimensional Models

The self-alignment mechanism of molten flip-chip solder joints is being increasingly used in passive alignment of optoelectronic devices. For these applications, three-dimensional models of misaligned solder joints are necessary to understand the effect of solder joint design parameters on self alignment. To reduce the complexity of fully three-dimensional models, intuitively reasonable assumptions are often made in their theoretical development. Two such assumptions for misaligned flip-chip solder joints with circular pads are that the locus of centroids is a straight line and that the cross sections are circular in shape. In the present paper, the limits of validity of these two assumptions are explored. In general, if either the top and bottom pad radii are identical, or if there is no misalignment between the pads, then the centroidal locus is a straight line and the cross sections are circular. The extent of deviation from straight line centroidal locus or circular cross section depends on the ratio of the top and bottom pad radii and on the extent of misalignment between the pads. For a misalignment equal to 20 percent of the solder joint height and a joint with 90 percent pad diameter ratio, the deviation from straight line locus is 7 percent and the deviation from circularity is less than 1 percent. However, as the pad ratio is decreased to 50 percent, and as the misalignment is increased to 100 percent, the deviation in centroidal locus increases to 43 percent and the deviation from circularity increases to 33 percent. Thus, straight line locus and circular cross sections are reasonable assumptions for flip-chip solder joints provided the pad diameter ratio and misalignment are small.

Numerical Simulations of Electromigration and Stressmigration Driven Void Evolution in Solder Interconnects

2012 ◽  
Vol 134 (2) ◽  
Author(s):  
Subramanya Sadasiva ◽  
Ganesh Subbarayan ◽  
Lei Jiang ◽  
Daniel Pantuso
Keyword(s):  
Finite Element ◽  
Flip Chip ◽  
Solder Joints ◽  
High Current Density ◽  
Equations Of Motion ◽  
Void Formation ◽  
Phase Field Model ◽  
Bulk Diffusion ◽  
Stress Fields ◽  
Void Evolution

Understanding the effect of high current density on void formation and growth and relating the size of the void to the resulting electrical/mechanical failure is a critical need at the present time to ensure reliable functioning of flip-chip packages. In general, toward this end, the modeling and simulation of geometrical evolution of current induced voids have been relatively few. Simulations considering the coupled effects of mass transport through mechanisms of surface and bulk diffusion under the influence of electrical, thermal, and stress fields in solder joints leading to eventual electromigration failure do not appear to be common. In this study, we develop a phase field model for the evolution of voids under electrical, thermal, and stress fields in a flip-chip solder interconnect. We derive the equations of motion for the void accounting for energetic contributions from the active factors of surface energy, stress, and electric potential, considering both surface diffusion and transfer of the material through the bulk of the material. We describe the implementation of this model using a finite element code written in the PYTHON language, coupled with a commercial finite element solver from which we obtain the electrical, thermal, and stress fields driving the void motion. We demonstrate the implemented methodology through simulations of void evolution in flip-chip solder joints under the effects of mechanical/electrical fields and surface/bulk diffusion.

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