镀钨金属化对超音速激光沉积金刚石/铜复合涂层导热性能影响

Thermal Conductivity of Diamond/Copper Composite Coatings Prepared by Supersonic Laser Deposition with W Metallization

针对电子封装材料散热需求,为了获得高导热界面材料,通过盐浴镀方法在金刚石表面镀W,并采用超音速激光沉积(SLD)技术在铜基板表面制备金刚石/铜复合涂层,研究镀W金刚石颗粒的表面形貌及成分,及其对金刚石/铜复合涂层微观结构、界面结合和导热性能的影响。研究结果表明,SLD制备的镀W金刚石/铜复合涂层中颗粒间结合良好,界面无明显缝隙,热导率达306.3 W·m^(-1)·K^(-1)。金刚石表面镀W改善了金刚石与铜的表面润湿性,促进了金刚石与铜颗粒之间的界面结合,使涂层具有良好的致密性,表现出优异的导热性能。

With rapid development of the microelectronic components and high-power electronic equipment,the heat flux density per unit area of chip is increasing.The key to ensure the stability of electronic devices is to dissipate the heat timely and efficiently.The routinely used electronic packaging materials in thermal management has been difficult to meet the requirements.As a new generation of thermal management materials,diamond/copper composites have great potential in field of electronic packaging.At present,most of the preparation methods of diamond/copper composites are carried out at high temperature,which makes diamond easy to graphitize and makes copper easy to oxidize.Supersonic laser deposition(SLD)technology has a relatively low heat input,which can effectively avoid oxidation,phase transformation,ablation and grain growth.In this research,in order to solve the heat dissipation problem,a W-coated diamond/copper composite coating with the high thermal conductivity was prepared through the salt bath plating method for plating W on the surface of diamond,then SLD technology was used to deposit this coating on copper substrate.The surface morphology and composition of W-coated diamond,and the influence of diamond metallization on microstructure,interfacial bonding and thermal conductivity of diamond/copper composite coatings prepared by SLD were studied.The optimal W plating parameters are obtained at1100℃for 60 min,and W coating was uniform and dense with a thickness of 1.28μm.In addition to diamond phase,W_(2)C,WC and W phases were also found in X-ray diffractometer(XRD)pattern,since W was the strong carbide-forming element.Through the salt bath W plating,the roughness of diamond surface increased with surface fluctuation of 10μm and steep peaks,which increased the contact area with the copper phase on SLD preparation of diamond/copper composite coatings.Scanning electron microscopy(SEM)was used to analyze the cross-section morphology of diamond/copper composite coatings.Broken plating diamonds were seen in coating with internal crack.The elements mutual permeation did not occur between diamond and copper,suggesting that no metallurgical reaction occurred on the interface.However,the diamond was intact after the diamond particles coated without gaps between the diamond and copper particles.Tungsten carbide coating was formed on surface of the diamond after metallization of W plating,namely WC and W_(2)C generated by the reaction of W and C to form a favorable combination between particles.The combination between particles changed from a single mechanical combination to coexistence of mechanical combination and metallurgical combination.Therefore,the metallized coating played two roles in the deposition process of SLD:firstly,it protected the particles and avoided the breakage and internal cracks during the high-speed impact of diamond on the matrix;the other was to improve the wettability of diamond and copper,reducing the gaps at the junction of diamond and copper and enhancing the interface bonding between diamond and copper.The interfacial structures of the composite coating were diamond-WC,W_(2)C and W-copper from diamond to copper.In order to compare the effect of W plating on thermal conductivity of the coatings,the copper coating,diamond/copper composite coating and W plating diamond/copper composite coating were prepared by SLD.The laser thermal conductivity meter was used to measure the thermal conductivity of the coatings.The results showed that the thermal diffusion coefficient of the copper coating was 57.9 m^(2)·s^(-1),and the thermal conductivity was 170.2 W·m^(-1)·K^(-1).After the addition of uncoated diamond,the thermal diffusion coefficient and thermal conductivity of the composite coating increased to 72.5 m^(2)·s^(-1)and 238.1 W·m^(-1)·K^(-1),which indicated that the high thermal conductivity diamond could improve the thermal conductivity of the composite.The thermal diffusion coefficient and thermal conductivity of W plating diamond/copper composite coating prepared by SLD were 80.4 m^(2)·s^(-1)and 306.3 W·m^(-1)·K^(-1),respectively.The results showed that W metallization could improve the interfacial bonding between diamond and copper,and increase greatly the thermal conductivity of diamond/copper composite coating.The surface roughness of diamond increased obviously,which had a positive effect on the subsequent preparation of W-coated diamond/copper composite coating by SLD.After the metallization of diamond plating W,diamond and copper layer closely combined in the composite coating without obvious gaps.W and Cu elements in the coating permeated each other,so that the bonding between particles changed from the single mechanical bonding to the coexistence of mechanical bonding and metallurgical bonding.The interface bonding between diamond and copper was improved by W plating on the surface of diamond.Then the gap and interfacial thermal resistance of composite reduced significantly,and the thermal conductivity of diamond/copper composite coating increased.All these factors resulted in increasing of the thermal conductivity of W-coated diamond/copper composite coating.The above research would be of guiding significance to the application of thermal management of advanced electronic packaging materials.