| 摘要: | 共晶Sn58Bi銲料合金具有138oC的低熔點溫度，對於先進的電子構裝非常有吸引力。然而，合金的高硬度和脆性性質可能在處理過程中損壞設備並導致可靠性問題。在本研究中，引入了包含Sn0.3Ag0.7Cu（SAC0307）和SnBi的混合銲料形成SnBi/SAC0307之複合式銲料，使得相對延展性的SAC銲料可以用作緩衝層以吸收外部應力。試片以表面黏著技術(Surface Mount Technology，SMT)進行不同回流溫度封裝成印刷電路板 (Printed circuit board, PCB)。並採用Sn-56.8Bi-1Ag-0.2Cu銲料與SnBi/SAC0307 (Hybrid solder)複合式銲料比較其微結構及銲料之接點強度。對樣品進行75、100和125 ℃，5天、10天、20天之熱時效測試，觀察其界面反應及表面形貌，使用影像分析軟體計算出界面介金屬(Intermetallic Compounds, IMC)化合物的生長機制，並用動力學方式計算生成活化能。利用印刷電路板上不同規格的晶片元件(Chip component)進行推力測試以探討機械性質，並比較不同規格晶片元件之間推力強度差異。研究不同規格晶片元件的斷裂模式以及斷裂面之微觀結構並加以統計。經本實驗結果顯示，增加熱時效處理的溫度以及天數會使IMC的厚度線性增加。在推力測試中，SnBi銲料主要以脆性斷裂的機率較大；而SnBi/SAC0307複合式銲料於0603及0402規格的推力測試結果中以延性破壞為主，長時間的熱時效處理，混合銲料確實抑制了脆性斷裂，並且接點之機械性質有所提升。;The melting point of the eutectic Sn-58Bi solder at 138°C, is desirable for advanced electronic packaging; however, the high hardness and brittleness of this alloy can lead to the damage of devices during processes and cause a reliability issue. In this study, a hybrid solder containing Sn0.3Ag0.7Cu (SAC0307) and Sn-56.8Bi-1Ag-0.2Cu (SnBi) is introduced to improve the mechanical properties, and the SAC solder can be used as a buffer layer for absorbing external stress. Printed circuit boards (PCBs) are packaged with Sn56.8Bi1Ag0.2Cu and SnBi/SAC0307 (hybrid solder) by surface mount technology (SMT) under different reflow temperatures. Further, an aging test was conducted under 75°C, 100°C, and 125°C for 5, 10, and 20 days, respectively, and interface reactions and surface morphology are then investigated. Furthermore, an image analysis software is introduced to calculate the thickness of intermetallic compounds (IMC), and the activation formation energy can, therefore, be calculated by kinetics. The difference of the shear strength among varying sizes (0402, 0603, and 0805) of the chip component was compared by shear tests. The microstructure of different fracture modes and the fracture surface are observed, and the results are summarized. Results show that the thickness of the IMC increased linearly with the increase of aging time and temperature. Shear test results reveal that SnBi shows high possibility of brittle fracture, whereas the SnBi/SAC0307 hybrid solder represents a tendency of ductile fracture in the size of 0603 and 0402. To summarize, the hybrid solder indeed inhibits a brittle fracture, and the mechanical properties of joints is improved. |
