Au80Sn20 alloy is a widely used solder for laser diode packaging. In this paper, the thermal resistance of GaN-based blue laser diodes packaged in TO56 cans were measured by the forward voltage method. The microstructures of Au80Sn20 solder were then investigated to understand the reason for the difference in thermal resistance. It was found that the microstructure with a higher content of Au-rich phase in the center of the solder and a lower content of (Au,Ni)Sn phase at the interface of the solder/heat sink resulted in lower thermal resistance. This is attributed to the lower thermal resistance of Au-rich phase and higher thermal resistance of (Au,Ni)Sn phase.

中文翻译：

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Au80Sn20焊料微观结构对TO56封装GaN基激光二极管热阻的影响

Au80Sn20合金是一种广泛用于激光二极管封装的焊料。本文采用正向电压法测量封装在TO56罐中的GaN基蓝色激光二极管的热阻。然后研究 Au80Sn20 焊料的微观结构以了解热阻差异的原因。结果表明，焊料中心富Au相含量较高而焊料/散热器界面处(Au,Ni)Sn相含量较低的微观结构导致较低的热阻。这归因于富金相的较低热阻和 (Au,Ni) Sn 相较高的热阻。