铝合金表面阳极氧化处理及膜层的散热性能

Fabrication of Anodic Alumina Film on Aluminum Alloy Plate and Evaluation of Its Heat Diffusion Behavior

通过阳极氧化在铝合金表面制备氧化铝薄膜,可提高铝基板绝缘及散热性能,是一种理想的发光二级管(LED)封装基板。在平行对电板模式下,采用直流电源,分别在硫酸和草酸体系中在1A90铝板表面制备了均匀、有序、纳米级孔洞结构的氧化铝薄膜。通过扫描电镜观察氧化膜的形貌并测量膜厚,采用高压电源测试了氧化膜的击穿电压。通过定值电阻通电模拟了LED放热,测试了氧化膜铝基板的散热能力。研究了电流密度、电解液类型及浓度、电极间距对氧化膜表面形貌、电绝缘及散热性的影响。结果表明:硫酸和草酸溶液中,随电流密度增加,氧化膜孔洞逐渐变大,孔壁变薄,当电流密度过大时,氧化膜表面杂乱无章;随电流密度增加,膜厚先增后减,电解液浓度对氧化膜形貌影响较小;硫酸溶液中所得氧化膜更致密、更厚;采用0.8 mol/L硫酸溶液,电极间距为7.5cm,电流密度为5.3 A/dm2时,可制备厚24μm,孔径约25 nm的氧化膜,其击穿电压达2.46 kV,散热性能良好。

Anodic alumina films with uniform and ordered holes were prepared on 1A90 aluminum alloy plates in sulfuric acid solution and oxalic acid solution by using double parallel plate mode and direct current power source. The surface morphology and thickness of as-prepared alumina films were analyzed by means of scanning electron microscopy,and its break down voltage was measured with a high voltage power supply. Besides,a resistor was used to simulate LED,and the heat diffusion capacity of the aluminum substrate was tested. The effects of current density,type and concentration of the solution,and distance between the electrodes on the surface morphology as well as heat dissipating and electrical insulating properties of anodizing films were investigated. Results indicated that,with the increase of current density in sulfuric acid and oxalic acid,the hole size of the anodizing films tended to gradually rise and the hole wall thickness tended to decline. When the current density was too high,the surface of the anodizing films became disordered. Besides,with the increase of the current density,the thickness of the films tended to rise initially but declined later. Moreover,the concentration of the electrolyte had insignificant effect on the morphology of the anodic films,and the anodizing film obtained in sulfuric acid solution was more compact and thicker. Particularly,the anodizing film obtained in the sulfuric acid solution of 0. 8mol /L at an electrode distance of 7. 5 cm and current density of5. 3 A /dm2 had a thickness of 24 μm,hole size of about 25 nm and a break down voltage of 2. 46 kV as well as good heat diffusion behavior.