| The development of modern microelectronics technology has entered the era of integrated system chips and modular chips.Three-dimensional packaging has greatly reduced the volume by realizing modularization of stacked chips in three-dimensional space.At the same time,the load on the solder joint which is the key part of the mechanical and electrical connection is getting heavier.In order to improve the reliability of solder joints,the preparation of composite solder by adding micro-nano par-ticles to the solder matrix is one of the effective methods currently used.In this paper,Sn-x Al(x=0.1,0.2,0.3,0.4,0.5wt.%)composite solder was prepared by mechanical mixing method.First,the physical properties and soldering performance of the composite solder were compared by comparing the differ-ent amount of micro-nano Al additions influence,chose the optimal addition amount,and then took Cu/Sn-x Al/Cu solder joints as the research object,systematically discussed the influence of micro-nano Al which is strengthening phase on the interfacial microstructure and mechanical properties under dif-ferent bonding times,and finally the microstructure growth and mechanical properties of solder joints during aging and thermal cycling were studied.The results of this study are as follows:The effect of different amount of micro-nano Al additions on solder was studied.The results are as follows:the addition of micro-nano Al particles has a small effect on the melting point of Sn-based composite solders,and the wettability of the composite solder increases first and then decreases with the increase of the amount of micro-nano Al.When the amount of micro-nano Al particles is 0.3wt.%,the solder spreading area is the largest.The growth thickness of Cu6Sn5 intermetallic compound at the interface of Sn-x Al/Cu solder joints decreases with the increase of the addition amount,and then in-creases.The thickness of Cu6Sn5of Cu/Sn-0.3Al/Cu solder joints is the smallest,which is 1.84?m.Micro-nano Al strengthening phase can effectively improve the shear strength of solder joints.When the addition amount is 0.3wt.%,the shear strength of solder joint is significantly increased by 45.6%.Observing the fracture structure,it can be found that when the micro-nano Al addition amount is0.3wt.%,the number of dimples was the largest and the dimples were the deepest.The effect of the optimal amount of micro-nano Al addition on Cu/Sn-x Al/Cu solder joints was stud-ied.The result is that the grain size of Cu6Sn5 is large,and the micro-nano Al particles tend to be ad-sorbed at the grain boundaries of intermetallic compounds to refine the crystal particle size,blocking the interdiffusion of atoms,reducing the growth thickness of Cu6Sn5 phase and Cu3Sn phase interme-tallic compounds at the interface,part of micro-nano Al participates in the reaction to form Sn-Al-Cu compounds,improves the shear strength of the solder joint,and when the bonding time is 30 min,the shear strength of the solder joint was increased by 25.7%.The fracture mode of the solder joint is mixed fracture,and there are cleavage fracture characteristics similar to"steps"and"island-like"crystalline fracture surfaces in the fracture topography.The results of research on the growth and mechanical properties of solder joints during aging and thermal cycling are as follows:During isothermal aging,the growth rates of Cu3Sn phase compounds for Sn solder joints and Sn-0.3Al solder joints were 8.94×10-2 and 8.34×10-2,when the aging time is500h,the shear strength of the solder joints decreased by 35.6%and 27.4%,respectively,and the solder joint fracture mode was mixed fracture.During thermal cycling,the growth thickness of Cu3Sn of both the Sn solder joint and the Sn-0.3Al solder joint increased.The growth thickness were 5.07?m and 4.28?m,respectively.The Sn-0.3Al solder joint had higher shear strength and a slower decline rate.Accord-ing to the fracture microstructure,there were small dimples with a tissue composition of Cu3Sn and the main fracture mode was mixed fracture. |
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