| Electronic packaging materials refer to the matrix materials used to carry electronic devices and their interconnections and play the role of heat dissipation,mechanical support,sealing,environmental protection,signal transmission,and shielding.Al-Si composite for electronic packaging combines the excellent properties of Al and Si which has the advantages of high thermal conductivity,low expansion,low density,and easy coating.It meets the requirements of mechanical,thermophysical and technological properties of packaging materials for electronic packaging.At present,the research on Al-Si electronic packaging materials abroad has gradually been applied to commercial production.However,the research on Al-Si electronic packaging materials in China started fairly late and lagged in technology which has some shortcomings in the preparation process of Al-Si alloy.Therefore,the purpose of this thesis is to explore the effects of pressing mold temperature,material composition,sintering temperature and sintering time on the structure and properties of materials by studying powder hot pressing and vacuum sintering process and then to prepare Al-Si electronic packaging materials with excellent properties.The effect of preheating temperature of powder molding mold on the structure and properties of the materials was studied.The powder was preheated to 300? and the mold was preheated to 300?,350?,and 400?,respectively.The billet was pressed under900MPa and sintered in vacuum at 900? for 2h.The results showed that:the powder was formed well without significant cracks at 350?.The microstructure and properties of the sintered materials were good,the thermal conductivity reached 115W/m·K and the average thermal expansion coefficient was 10.8×10-6/K at room temperature to 150?.The relative density reached 98.8%and the Brinell hardness reached 123.7HBW.The effect of material composition on the structure and properties was studied.The powder ingots with Al-50wt.%Si,Al-60wt.%Si and Al-70wt.%Si was sintered in vacuum at 900? for 2 hours.The results showed that the thermal expansion coefficient of the compound material was mainly affected by Si content which decreased with the increase of Si content and the thermal conductivity increased first then decreased.When the content of Si was 60%,the relative density of the materials reached the highest 99.8%,and the compound material had a high thermal conductivity?128 W/m·K?and a low coefficient of thermal expansion(9.97×10-6/K)at the same time,meanwhile,the materials had sufficient hardness.The effects of sintering temperature and sintering time on the structure and properties of materials were studied.The Al-60wt.%Si material was treated at different sintering temperature and time,and the sintered material was studied and analyzed subsequently.The results showed that the microstructure and properties of the material were the best when the sintering temperature is 850? and the sintering time is 2h.The thermal conductivity and thermal expansion coefficient were 131.4 W/m·K and 10.02×10-6/K respectively,and the relative density was 99.9%.The proper increase of temperature and delay of sintering time could effectively improve the wettability of materials and promote the filling of holes in the material by liquid Al.Reducing the total number of interfaces in the material and ensuring the formation of the Al matrix interconnected network structure promoted the increase of thermal conductivity and the thermal expansion coefficient of the material,but generally speaking,the relative content of Si phase and voids had greater influence to the thermal expansion coefficient. |
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