低铯含量KF-CsF-AlF_3铝钎剂的物相结构与熔化特性的关系

Relationship between phase structure and melting characteristics of low cesium KF-CsF-AlF_3 aluminum flux

采用差示扫描量热法(DSC)对湿法合成的低铯含量KF-CsF-AlF3铝钎剂样品进行了熔化特性测定,归纳总结了该钎剂的熔化特性随成分的变化规律.利用XRD,SEM和EDS分析技术,研究了典型样品的物相结构和微观形貌.结果表明,低铯含量钎剂主要由棒状K2AlF5和絮状Cs2KAl3F12机械混合物组成,致使微观上局部成分偏离三元共晶成分点E4或E5.因此在加热过程中难以发生三元共晶反应,而是在温度505℃附近发生K2AlF5固态相转变反应.在温度525℃附近发生Cs2KAl3F12相的熔化反应,这是造成实际湿法合成的钎剂样品熔化温度与理论相图差异较大、特别是液相线升高的根本原因.

The melting curves of low cesium KF-CsF-AlF3 flux samples prepared by wetting synthesis method were measured with differential scanning calorimetry(DSC),and the effect of the flux compositions on the melting characteristics was analyzed and summarized.The phase structure and morphology of typical flux samples were analyzed by X-ray diffraction(XRD),scanning electron microscope(SEM) and energy spectrum analysis(EDS),respectively.The results indicated that the wetting synthesized flux was mixture of rod-shaped K2AlF5 and flocculent Cs2KAl3F12.Because the localized compositions deflected from the eutectic point E4 or E5,it was difficult for the ternary eutectic reaction to occur during the melting process.However,the decompose of K2AlF5 at 505 ℃ and melting of Cs2KAl3F12 at 525 ℃ occurred,which led to the large difference between the melting temperature of flux samples prepared by wetting synthesis method and that from the theoretical ternary phase diagram,and especially the increase of the liquidus.