采用硬质阳极氧化工艺制备LED封装用铝基板绝缘层,通过实验分析了制备铝基板过程中氧化时间、草酸浓度、硫酸浓度和电流密度等因素对其氧化膜厚度、击穿电压的影响,得到了制备低热阻铝基板的最佳工艺参数:电流密度3A/dm2,草酸浓度为10g/L,H2SO4浓度150g/L,氧化时间45min。利用原子力显微镜(AFM)观察热冲击后裂纹萌生的情况,结果表明铝基板有微小裂纹,但仍满足绝缘要求,通过对氧化铝膜热阻的测试发现,铝基板与氧化膜的复合热阻在1~3℃/W之间。结果表明用阳极氧化法制备的铝氧化膜满足LED基板对散热及绝缘性的要求。
Insulation layer of aluminum substrate for LED encapsulation was made by hard anodizing technology.The impact of oxidation time,concentration of oxalic acid,sulfuric acid and current density on thickness and breakdown voltage was studied.Then optimum parameters of low thermal resistance aluminium substrate were obtained:current density was 3A/dm2,concentration of oxalic acid was 10g/L,concentration of sulfuric acid was 150g/L,oxidation time was 45min.AFM was used to observe crack initiation after thermal shock.The result shows that aluminum plate has small cracks which does not affect the insulation performance.By testing thermal resistance,we find that the composite thermal resistance of Al and oxide film was 1-3℃/ W.The result shows that the oxide film prepared by anodic oxidation technology meet the requirements of LED substrate.
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