Electroplating Through SU-8 Pattern to Fabricate UV-LIGA's Soft Magnetic Ni-Fe Microstructure and Studies on it's Electrochemical Characteristic and Composition Gradient
George C. Tu
|關鍵字:||紫外光深刻微電鑄;SU-8厚膜光阻;旋轉環-圓盤電極;鎳鐵微構件;成份梯度;逆Hall-Petch效應;UV-LIGA;SU-8 Photoresist;rotating ring-disk electrode;Ni-Fe Microstructure;Composition Gradient;inverse Hall-Petch behavior|
利用旋轉環-圓盤電極(RRDE)結合C-V Test 研究鎳鐵合金的電化學特性。本實驗收集效率為0.4615。在實驗中鎳鐵不規則共沉積主要是受電極表面Ni(OH)+和Fe(OH)+濃度的影響。鎳沉積被較高表面濃度的Fe(OH)+所抑制，但在高pH值下，表面Fe(OH)+濃度卻無明顯的優勢。在添加劑方面，糖精比檸檬酸更能有效地降低析氫反應。
在鎳鐵微構件的成份梯度研究上，擴散-控制行為導致在較狹窄的凹膜中鐵沉積被抑制而降低鐵含量；在較寬的凹膜中則受對流行為控制。在大於1ASD的電鍍條件下，成份梯度結果顯示質傳效應使得擴散-控制行為更為明顯。在鎳鐵共沉積中，晶粒細緻效應使得晶粒隨著鐵含量升高而細化。當鐵含量達到41 wt.%，晶粒細化至12.18 nm。當晶粒細化至15 nm以下，逆Hall-Petch效應使得硬度呈現下降趨勢。在磁性量測上，保磁力為0.5Oe以下，而飽和感應則約為2500Gauss。|
UV-LIGA is one of MEMS to fabricate three-dimension microstructure of high aspect ratios. UV-exposure SU-8 pattern of high aspect ratio ~12 used to the electroplated mold was demonstrated. A sulphate-based Ni-Fe electrolyte was developed for electroplating through Su-8 pattern to form high aspect microstructure. Microstructure with a maximum height of 200 mm and aspect ratios of one to 12 were filled completely. A rotating ring-disk electrode (RRDE), combined with stripping voltammetry has been applied to a convenient, fast and inexpensive technique of electrochemical characterization of Ni-Fe alloy plating system. Experimental collection efficiency was determined about 0.4615 precisely. Ni-Fe codeposition depended on the formation of Ni(OH)+ and Fe(OH)+ on electrode surface. Ni deposition was suppressed in the presence of higher surface concentration of Fe(OH)+; However, surface concentration of Fe(OH)+ did not take advantage in high pH. Additive, sacchrain decreasing H2 evolution was more usable than citrate while Ni-Fe plating through pattern. Studied on composition distribution over the height of Ni-Fe showed that diffusion-limiting controlled lead a suppression of Fe deposition to decrease the iron content in narrow pattern and convection-controlled occurred in wild pattern. Composition gradient varied with current density also showed mass transport under a current density of about 1 ASD no significant enhancement. Codeposition iron had profound grain refining effect which increasing the iron content up to 41 wt.%, the grain size decreased to 12.18 nm. With decreasing grain size to 15 nm, the hardness of electroplating Ni-Fe alloy started following an inverse Hall-Petch behavior was observed leading to softening at the smallest gain sizes. The coercitivity was determined to be less than 0.5 Oe and the saturation magnetization was about 2500 Gauss.
|Appears in Collections:||Thesis|