低熱膨脹係數合金之MIM製程及封裝研究

摘要 目前低熱膨脹係數的合金如Fe-36%Ni、Fe-29%Ni-17%Co，主要是利用熔煉鑄造的方式來製作，製作完的工件須經二次機械加工來將多項零件予以組合，會導致成本升高、公差變大、量率降低的情形出現。近年來由於金屬粉末射出成形製程（(Metal Injection Molding , MIM）之急速開發，因此若能利用MIM來製作形狀複雜的低熱膨脹係數的工件應是較佳的作法。這些低熱膨脹係數合金一般會與玻璃進行接合，所以兩者的熱膨脹係數越接近越佳，以免在過冷或過熱的環境中產生缺陷，造成界面出現裂縫，使得金屬盒內之電子元件失效。 目前Kovar以MIM製作時可由混合粉及預合金粉兩種原始粉末得到，其中混合粉的成本較低且燒結密度較高；且無論在混合粉或是預合金粉方面，元素均勻性都不錯，沒有造成部份區域出現粉末聚集的現象。試片之製作過程也可避免碳含量之污染，而最後所得之CTE也與一般熔煉所得之結果相近，這證明了利用MIM來製作低熱膨脹係數工件是一個可靠度高的製程。另外也針對微調Ni-Co比例後，對於CTE的影響，發現Fe(54%)-Ni(28%~33%)-Co(13~17%)保有低熱膨脹係數的特性，Kovar與玻璃接合必須在Kovar表面預先形成一層薄氧化層來幫助Kovar與玻璃接合，形成氧化層後與玻璃在接合溫度為1115℃持溫15分鐘接合試片，可得到約160 MPa剪切強度。Abstract The low CTE alloys, such as Fe-36%Ni and Fe-29%Ni-17%Co, was usually made by melting and casting. These parts need secondary machining and lead to higher cost. Since the MIM (Metal Injection Molding) process is very well developed, it is very likely that the produce the low CTE alloys with complex shapes. MIM'ed Kovar made from prealloyed powders and mixed elemental powders in this study. The mixed elemental powder could attain higher density (95~96%). Both of prealloyed powders and mixed elemental powder produce uniform alloy distributions. The carbon pollution can be kept low and does not affect the CTE. The CTEs of Kovar are 4.8 mm/m℃ (for mixed powders) and 4.74 mm/m℃ (for prealloyed powders). The CTE of Invar is 1.49 mm/m℃ (for the mixed powders). They are all close to those by melting and casting. To find out the adequate range for the alloy composition, were changed and it was found that the {Fe(54%)-Ni(28~33%)-Co(13~17%)}. To have good metal to glass sealing, it need to pre-oxidize the alloy. After sealing at 1115 for 15 mins, a shear strength of 160 MPa was obtained. The sealing does not fail the temperature cycling until 300 cycles are reached.目錄 第一章 簡介 1 1-1 射出成型之簡介 1 1-2 粉末射出成型之合金 3 1-3 Low-Expansion Alloys 4 1-3-1 Kovar 6 1-3-2 Invar 9 1-4影響熱膨脹係數之因素 13 1-4-1成分的影響 13 1-4-2碳含量的影響 16 1-5粉末對密度的影響 17 1-6構裝之接合 18 1-6-1氧化與潤濕性 20 1-6-2 氧化處理 20 1-6-3金屬與玻璃之接合處理 24 1-7 研究動機 25 第二章 實驗 27 2-1 實驗流程 27 2-2原料 28 2-2-1基礎粉 28 2-3混煉 37 2-4射出成形 37 2-5脫脂 38 2-5-1溶劑脫脂 38 2-5-2熱脫脂 38 2-6 燒結 38 2-7 預氧化處理 38 2-8 接合處理 38 2-9 溫度循環 39 2-10性質測試 39 2-10-1黏度測試 39 2-10-2金相與成分分析 39 2-10-3 含碳量分析 40 2-10-4尺寸穩定性之評估 40 2-10-5熱膨脹儀 4