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The Densification and Property of Al-50%Si Alloy for Electronic Packaging

Author: YuLei
Tutor: SunJianFei
School: Harbin Institute of Technology
Course: Materials Engineering
Keywords: high-silicon aluminium alloy packaging material spray forming hotisostatic pressing (HIP) weldability
CLC: TG146.21
Type: Master's thesis
Year: 2013
Downloads: 52
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Abstract


Hypereutectic Al-Si alloys which are widely used in aviation and spaceindustry, modern electronic information technology and so on due to their lowerdensity, lower thermal expansion coefficient, excellent heat-conducting propertyand mechanical properties have considerable development prospect. Howevertraditional casting to form bulky silicon phase limit the development of itsapplication in daily. Using of spray forming technology for this kind of alloy,cansignificantly refine the primary Si phase, for achieving the goal of optimizationimprove the comprehensive performance.This paper treats Al-50%Si alloy made by spray forming equipment as theresearch object, and hot isostatic pressing technology is chosen as the alloy toeliminate internal porosity densification process. Analyzing the microstructureof spray forming high-silicon aluminum alloy, organize the property of thermalexpansion properties of thermal conductivity and mechanical properties. Usedfor aluminum silicon alloy electroplating method to improve the alloy surfacewettability, the influence law of process parameters on the coating analyzes thesolution temperature, current density and electroplating time etc. After platingalloy we start solderability test, to research alloy welding property.The research result shows: Compared with traditional casting, sprayforming alloy organization gets significant refinements, fine primary siliconphases are in particles or the skeletal diffuse distribution in aluminum substrate.According to formation mechanism the pore of deposited alloy can be dividedinto Involved in type porosity, Shrinkage porosity and pore gap type.In spray forming high silicon aluminum alloy deposition state for threedifferent hot isostatic pressing process, research and analysis the influence ofdifferent process on microstructure were studied.Finally the optimal alloydensification process is obtained, processing temperature for550℃, the pressureof126MPa, heat preservation for5hours, after the densification of densemicrostructure refinement, pore is basic be eliminated entirely, comprehensiveproperty is improved significantly.Through the study of alloy thermal expansion coefficient of the test dataanalysis, Alloy thermal expansion coefficient was11.6×10-6k-1between0250℃. Alloy thermal expansion coefficient and temperature was positivelyproportional relationship, and thermal expansion properties of the alloy andalloy composition of grain morphology and microscopic pore or internal stress state.For alloy thermal conductivity test, found that the thermal property of acertain range increased with the rise of temperature, it reaches156.8W/(m·k)as a maximum at50℃. The alloy phase morphology and distribution、densityand interfacial thermal resistance have different effects on the thermal properties.Three densification processes the mechanical properties of the alloy, thedensification degree of the best the highest mechanical properties, fracture oftensile strength of150MPa alloy had no obvious toughening, with transgranularfracture, crack source is basic in the early phase in primary silicon and siliconwith aluminium matrix of the junction.Decided to the property of the coating before leaching zinc platingprocessing, electroplating process parameters on the coating also has certaininfluence, electroplating, the optimal process parameters for: current density of1.0A/dm2, plating temperature is25℃and the electroplating time is10minbrazing time pressure, etc. Has A certain influence on the organization andproperty of the weld, when the pressure is bigger, the parent metal alloy wouldoccur to the weld area element diffusion.

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CLC: > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > Metallic materials > Non - ferrous metals and their alloys > Light non-ferrous metals and their alloys > Aluminum
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