Influencing Factors of Fatigue Life of Nano-Silver Paste in Chip Interconnection
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https://doi.org/10.1007/s11664-020-08501-3 Ó 2020 The Minerals, Metals & Materials Society
Influencing Factors of Fatigue Life of Nano-Silver Paste in Chip Interconnection HUI YANG
1,2
1.—School of Mechanical and Electrical Engineering, Central Changsha 410083, Hunan, China. 2.—e-mail: [email protected]
South
University,
The finite element software ANSYS was used to simulate the solder joints in the flip chip, and the stress and strain distribution results of the solder joints are displayed. During the simulation process, the final results of the simulation were not the same when the solder joints of different sizes were used. The simulation results under thermal cycling load show that the area where the maximum stress and strain occur is mostly distributed in the contact area between the solder joint and the copper pillar and at the solder joint. During the entire thermal cycling load process, the area where the maximum change in stress and strain occurs is always at the solder joint, and when the temperature changes, the temperature at the solder joint changes significantly. From the comprehensive analysis, the relevant empirical correction calculation equation is used to calculate and predict the thermal fatigue life of the solder joint. We found that when the diameter of the solder joint is constant, the increase in the height of the weld point will increase its thermal fatigue life; when the height of the weld point is constant, the increase in the diameter of the weld point increases its thermal fatigue life. The effect of height is greater than the effect of diameter. Key words: Nano-silver paste, fatigue life, simulation, temperature cycle, solder joint
INTRODUCTION Nano-silver paste is a promising electronic material for chip interconnection. Compared with traditional alloy solder, it has the following advantages. 1.
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Metal silver has a very high thermal conductivity (410 W/m K). Some studies have shown that the thermal conductivity of nano-silver paste can reach 229 W/m K. The heat dissipation performance is good, and it can meet the needs of modern electronic packaging. When the nanometer size is reached, the particles have a higher surface energy, which causes the melting point of the nano-silver to drop. The nano-particles in the liquid phase are sintered together by capillary force to form a sintered
(Received July 2, 2020; accepted September 19, 2020)
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material with a melting point similar to that of the bulk material. Nano-silver joints can be sintered at low temperatures and serve at high temperatures. This property is very suitable for multi-level packaging.1–3 The joint sintered with nano-silver paste consists of a single structure. After continuous aging experiments, the shear strength is basically unchanged. Nano-silver particles can effectively pin dislocations and limit crack growth, extending solder joint fatigue life.4
Some scholars have good research in plastic deformation. A similar, comprehensive study was done by Radchenko5 and Tippabhotla6 for interfacial plastic-fractu
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