Study On The Process And Properties Of Copper-chromium Composite For Electronic Packaging By Laser Additive Manufacturing

Due to the unique two-phase "pseudo" alloy structure,the copper-chromium alloy has the advantages of both the Cu component and the Cr component,making it a very good breaking force,pressure resistance,fusion resistance and mechanical properties of the vacuum electrical contact.Great upgrades have been widely used in the medium voltage field.However,the high-pressure and ultra-high pressure fields have not yet achieved breakthroughs.The main reason is that the conventional infiltration preparation method is difficult to prepare copper-chromium contact materials with fine crystal grains,uniform structure and complicated shape,and even in the case of large breaking current.The anti-weld properties are not guaranteed and the arc ablation is severe.The emergence of dual-tube coaxial powder feeding laser additive manufacturing technology provides a good opportunity to solve the above problems.In this thesis,CuCr30 electric contact composite material is selected as the research object.The double-tube coaxial powder feeding technology is used to overcome the problem that it is difficult to uniformly mix powder due to the difference in density of Cu and Cr.The laser additive manufacturing technology is used to prepare a large formability.The dimensions of CuCr30 electrical contact samples were analyzed by metallographic,XRD,SEM,EDS and other analytical methods,and the electrical properties of the prepared samples were tested.The basic process parameters of laser additive manufacturing technology were obtained by the control variable method:laser spot diameter 3 mm,powder feeding rate 20 g/min,lap joint rate 30%,45#steel substrate thickness 15 mm,Z-axis lifting amount △ Z 2mm;the laser process parameters of the three sets of first layer printing test were determined by single pass test,multi-channel single layer test and cross test;then the two-layer test of the three sets of first layer test laser parameters was carried out,and finally determined.The laser power P=3800 W and the scanning speed v=600 mm/min are the laser process parameters of the double-layer printing test and the large-size CuCr30 contact material test.The CuCr30 sample prepared by the laser additive manufacturing technology has fine Cr dendrites uniformly dispersed on the Cu matrix.The density is 99.13%,the average grain size is 20～40 u m,the conductivity is 45.34%I ACS,the hardness is 94.4 HBW,the thermal conductivity is 145.94 W/(m·K),and the coefficient of linear expansion is 16.94 ppm/K.Practical application standards for copper-chromium contact materials with low Cr content.When the electrical contact test is performed,a phenomenon occurs in which the material is transferred from the cathode to the anode,and loss is generated at the same time,and as the current intensity increases,the amount of transfer increases,and the total loss increases.As the current intensity increases,the arcing energy increases and the material ablation becomes more severe.The surface of the contact will exhibit various morphological features such as pores,gaps,pits,and molten pool.