Study On The Low Temperature Bonding Mechanism Of Sapphire And SiCp/Al Based On Ultrasonicaly Metallizing Tin Based Solder

In recent years,aviation/aerospace vehicles have undertaken combat missions in modern information warfare,in which military optoelectronic equipments are an indispensable component for their role.The optical window composed of optical window lens and metal lens holder is the key component which ensures the military photoelectric device work effectivly.Sapphire has good light transmittance,excellent thermal and mechanical properties,which is the best optical window lens material.With high strength,good toughness,excellent wear resistance and fatigue resistance,silicon carbide particle reinforced aluminum matrix composite material is consider as a new generation of light weight structural material,which can be applied to the metal specular seat of optical windows.The bonding technology between the optical lens and the metal specular seat is a key problem in the manufacture of light windows.In view of the high temperature of the bonding,the difficulty of wetting,and the large residual stress of the joint,this article uses ultrasonic assisted metallizing tin based solder method to realize the brazing of sapphire and SiCp/Al on the low temperatureIn this study,Sn-Cu-Al solder layers were firstly deposited on the surface of sapphire and aluminum silicon carbide composite materials by ultrasonic assisted metallizing tin based solder at 300?.Then the sapphire-aluminum silicon carbide joint can be formed by brazing the metalized sapphire glass and aluminum silicon carbide composite material at 250?.Studies have shown that at the interface of sapphire/Tin-based solder and SiCp/Al/Tin-based solder,ultrasound promotes the reaction of Al and O to form amorphous Al₂O₃.The study found that with the extension of ultrasonic soldering time,the strength of the joint formed by secondary brazing increased first and then decreased.The maximum joint strength of 22MPa was obtained at an ultrasonic time of 30s.Moreover,the joint fracture basically occurred at the sapphire/Tin-based solder interface,indicating that the sapphire/Tin-based solder interface bonding force is weaker than that of the SiCp/Al/Tin-based solder interface.Aiming at the problem that the interface of the sapphire/Tin-based solder is weaker than that of the aluminum silicon carbide/Tin-based solder,the interface bonding characteristics of the sapphire/Tin-based solder are calculated and analyzed based on the first principles.Sapphire/Tin-based solder rely on the covalent interaction between Sn-O to achieve interface bonding,and the interface separation work is 1.11J/m².There is a strong O-Al covalent interaction at the?-Al₂O₃/amorphous Al₂O₃ interface,and the interface separation work is 1.85J/m².The O-O anti-bonding interaction exists inside the Al₂O₃ amorphous layer that formed at the sapphire/Tin-based solder interface,thus the bonding of the Tin-based solder and the sapphire substrate is weakening that makes the?-Sn/amorphous Al₂O₃ interface separation work is only 0.68J/m².Therefore,the interface bonding of sapphire/Tin-based solder in the joint is weaker than that of aluminum silicon carbide/Sn-based solder,and the actual joint fracture occurs the interface between the Tin-based solder and the Al₂O₃ amorphous layer.