隨著高功率LED的快速發展，大量的焦耳熱會產生在高功率LED發光層。如果產生的熱無法有效的被消散至環境中，接面溫度會大幅上升，接面溫度的上升會大幅降低LED元件發光效率和生命週期，因此，高功率LED的熱管理變得相當重要。在高功率LED的熱管理中，由於目前固晶所使用的銀膠散熱相當差，因此，LED固晶於散熱基板的材料選用受到很多人的關注。 在這篇論文中，我們利用熱蒸鍍機將Ni/Cu金屬化層鍍在LED背面，並將Sn/Bi/Zn/Bi/Sn焊料層鍍在金屬化層上當作固晶材料。第一部分我們討論不同Sn鍍率對於Sn簇大小的影響。我們認為在高Sn鍍率下，Sn簇表層溫度較高，可以形成更多的液態Sn，表層液態Sn的形成有利於Sn簇間進行合併，並形成更大的Sn簇，最後我們藉由控制不同Sn鍍率形成不同形貌的Sn簇，並且建構Sn簇的成長機制。第二部分我們討論Bi鍍在不同形貌的Sn簇上，鍍Bi的過程中，Sn-Bi共晶相的生成使Sn簇變平整，另外，Bi相對於Sn有較低的表面能，會讓Bi在鍍Bi的過程中於表面析出，此外，由於Sn-Bi共晶相在大的Sn簇上有較高的機率進行合併，大的Bi簇會形成在大的Sn簇上。在鍍完Bi/Zn/Bi於Sn簇上，較大的Bi簇會形成在較大的Sn簇上，且在高Sn鍍率下，Bi簇的平均大小會大於低Sn鍍率的Bi簇。然而，在鍍完最後的Sn層後，Bi由於較低的表面能而於表面析出，然而，較平整的Sn-Bi-Zn共晶層卻會形成在高Sn鍍率的表面上，由於高Sn鍍率下將會形成更多的Sn-Bi-Zn共晶相於表面上，且共晶相會有較好的濕潤性。相反的，由於共晶相的合併，較粗糙的Sn-Bi-Zn共晶層會形成於低Sn鍍率的表面。第三部分我們討論不同表面形貌的Sn-Bi-Zn共晶層對於濕潤性的影響，在較平滑的焊料表面下，會有較小的接觸高度，於兩平行板間的接觸高度愈小會使得濕潤性上升，此外，會有較少的空氣被包覆在Cu金屬層和基板Ag表面之間，接合完後會有較少的孔洞於界面形成，並且會有較高的接合強度。 ;With the rapid development of high-power light emitting diodes (LEDs), the power applied on LED devices has increased much more than expected. If the heat generated in high-power LED cannot be dissipated efficiently, the lifetime of the device will rapidly decrease. Therefore, thermal management of packages is a critical issue for high-power LEDs. Among the thermal issues for LED packages, their die-attachment onto thermal substrates has attracted a great deal of attention. In this thesis, Sn/Bi/Zn/Bi/Sn solder layers are deposited on the LED/Ni/Cu surface as a die-attached material. In discussion part I, the size of bottom Sn clusters will increase with the Sn deposition rate. The liquid surface layer formed by the high surface temperature will facilitate the coalescence of Sn clusters. Then, different size of Sn clusters could be deposited by controlling the deposition rate of Sn. In discussion part II, Bi was deposited on the surface of Sn clusters. The large Bi clusters would be formed on the large Sn clusters due to coalescence of eutectic droplets. After the deposition of Bi/Zn/Bi on Sn surface, the large Bi clusters would be formed on the surface of high Sn deposition rate. However, a smooth Sn-Bi-Zn eutectic layer was formed on the surface of high Sn deposition rate after the deposition of Sn capping layer due to the formation of large amount of liquid phase and better wettability. On the contrary, a rough surface would be formed by the coalescence of eutectic droplets in the low Sn deposition rate. In discussion part III, the smooth surface with smaller contact height between Cu metallization layer and Ag substrate surface would have higher wetting force on the two plates. Therefore, less of air would be trapped at the bonding interface after the die-bonding process. The die strength of smooth Sn/Bi/Zn/Bi/Sn surface would be higher due to the less formation of void at the bonding interface.
