以金屬銲料接合石墨紙與氮化鋁之研究

Abstract

對於陶瓷材料而言，與異質材料的接合是個具有挑戰性且具備開發潛力的研究領域。本研究選用氮化鋁作為基板，以活性金屬銲片與石墨紙進行接合研究並比較溫度、氣氛等接合參數對介面的影響，並鑑定了介面處產生之反應物。相對於過往多在真空下進行接合，對於陶瓷-金屬-石墨系統在氣氛下之活性金屬硬銲有更深入的研究且觀察了機械性質與傳導性質的改變。 氮化鋁本身具有高熱傳導值的特性，同時其反應性相當低而不易受到腐蝕影響。而石墨紙雖然受限其結構而在縱向之機械性質以及熱傳導性質較差，但在平面方向有相當優異的性質。因此藉由使用活性金屬銲片克服兩者表面活性差的缺點將之接合，以氮化鋁基板提供整體強度，而石墨紙在表面可作為熱的導體形成散熱的複合系統。 本研究成功以金屬銲片Ticusil在流動氣氛環境下成功接合氮化鋁以及石墨紙，結果顯示銲片中的鈦會在升溫後移動到界面處，與氮化鋁形成氮化鈦層以及具有接近立方堆積結構之鈦銅鋁的氮化物，其成分及結構與 (Ti, Cu, Al)6N之結構近似，以及與石墨紙形成以TiC為主之鈦的碳化物。而改變接合溫度、持溫時間以及接合氣氛等參數對於介面反應物的影響也在本研究中進行研究與討論，另外對於在氮氣、氬氣等氣氛中接合時產生反應物的機制的推測則是在高溫時氣氛中的氮、氧溶入產生的富鈦共晶液體，在降溫過程時在剩餘的共晶液體中達到飽和而析出成顆粒狀的散布區域。 同時對於成功接合的試片也進行了機械性質、熱與電傳導性質的測量與探討。其中機械性質以四點彎曲試驗觀察破壞行為，結果顯示此接合系統改善了原本單層陶瓷的脆性破壞行為，使其破壞趨緩，同時此系統也具有方向性，以氮化鋁基板承受壓應力之機械性質表現較佳。此外，此接合系統之界面也相當穩固，整體系統的破壞取決於受力超過基材的強度而使基材先行破裂，而後才是界面的分離，因此界面的強度較基材來的穩定。而傳導性質的量測結果則顯示在接合後，複合基板其熱傳導性相對於氮化鋁基材有些許提升。

Heterogeneous joining is a challenging and promising issue for ceramic materials. In the present study, aluminum nitride was chosen as ceramic substrate to join with graphite paper by active brazing alloys. The influence of joining parameters such as temperature, atmosphere was also studied. Instead of most studies focus on joining in vacuum, the joining of ceramic-filler-graphite system was conducted in flowing atmosphere. The corresponding properties were analyzed. Aluminum nitride is a ceramic material with high strength, high thermal conductivity, its low reactivity makes it stable against chemical corrosion. Meanwhile, graphite paper exhibits poor mechanical properties and thermal conductivity along the vertical direction, but excellent properties in planar direction due to its structure. At the same time, active brazing alloy was chosen to join both substrates to conquer the poor reactivity of both substrates. The aluminum nitride substrate can be used to enhance the integrity. After bonding, the graphite paper should exhibit great thermal conductivity. The result showed that the aluminum nitride and graphite paper can be successfully joined with Ticusil while in a flowing atmosphere. The titanium within Ticusil moves to interface to form reaction phases during the brazing process. The reaction phase at the AlN-Ticusil interface is mainly composed of titanium-copper-aluminum nitrides. The nitride exhibits nearly cubic structure, similar to (Ti, Cu, Al)6N. For the graphite-Ticusil interface, the reaction phase is mainly composed of TiC. A simple mechanism of this filler joining in atmosphere was also proposed. The reactive elements in flowing atmosphere would dissolve into Ti-rich eutectic liquid at the elevated temperature. The particle-shape products would then precipitate during cooling process when the remained eutectic liquid saturated after forming TiN layer. The fracture behavior, thermal conductivity and electrical conductivity of the joined specimen was also observed. The bending result showed that the fracture behavior changed from catastrophic to graceful after joining. Besides, the four-point bending strength for the graphite-Ticusil-AlN is anisotropic, similar to graphite paper. The performance would be better if the aluminum nitride side is under a compressive stress. Meanwhile, the failure of the specimen started from the rupture of the substrates instead of the separation at the interface. Also, the conductivity was increased after joining.