鈷系表面處理鍍層於腐蝕環境之研究;Investigation of Co-based Layers in Corrosive Environment

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Title:	鈷系表面處理鍍層於腐蝕環境之研究;Investigation of Co-based Layers in Corrosive Environment
Authors:	林思維;Lin, Si-Wei
Contributors:	化學工程與材料工程學系
Keywords:	腐蝕;腐蝕機制;電化學;無電鍍鈷;表面處理層;Corrosion;Corrosion mechanism;Electrochemistry;Electroless Cobalt;Surface finish
Date:	2022-09-26
Issue Date:	2022-10-04 11:01:40 (UTC+8)
Publisher:	國立中央大學
Abstract:	5G通訊技術的發展提升了生活的便利性，若要維持訊號的穩定，則需架設更多基地台。為了提供基地台電子元件良好的可靠度，元件基板上會鍍製金屬鍍層保護元件，但常見的商用鍍層，如有機保焊層(OSP)、浸錫(ImSn)、浸銀(ImAg)、無電鍍鎳金(ENIG)與無電鍍鎳鈀金(ENEPIG)等鍍層於腐蝕環境中皆會被腐蝕而導致元件失效。本研究以鈷金屬作為新式表面鍍層，研究鈷(Co)、鈷鈀(Co/Pd)及鈷鈀金鍍層(Co/Pd/Au)於腐蝕環境下的腐蝕行為及腐蝕產物的組成，並藉由失效測試以及電化學量測結果探討鍍層之腐蝕機制。為避免測試結果受到其他氣體的影響，本研究使用二氧化硫(SO2)作為腐蝕氣體進行實驗。因目前常見的腐蝕測試規範皆是以濃度為ppb等級的腐蝕氣體進行測試，為了觀察鍍層在嚴苛環境下的抗腐蝕能力，本研究將腐蝕氣體濃度提升至ppm等級。本研究將實驗溫度設定為80 C、相對溼度為100% RH且反應時間固定為240小時以加速實驗進行。經過15 ppm 及150 ppm SO2的腐蝕測試後會有少許的腐蝕物生成於鍍層表面，透過分析可以得知腐蝕物皆為鈷化合物。為了解析鍍層的腐蝕反應的機制，分別將試片放入1.68M硫酸(H2SO4)水溶液進行電化學測試以及1500 ppm SO2腐蝕環境進行失效測試。由測試結果可知，僅鈷鍍層會被消耗並生成腐蝕物，由此證實鈀及金鍍層的添加雖然可以提升鈷鍍層的抗腐蝕能力，但腐蝕溶液仍會通過鈀及金鍍層並與鈷鍍層反應。由實驗結果可以推斷鈷系鍍層在嚴苛的環境中仍具有良好的抗腐蝕能力，可以做為犧牲層有效地保護銅基板，可以做為新式表面鍍層之材料選擇以應用於提高電子元件之可靠度。;The development of 5th generation mobile networks (5G) has improved the convenience of life. Hence, it is necessary to set more cells to maintain signal stability. To provide good reliability for cells, coating layers are added on printed circuit boards to protect electronic devices. However, common surface finishes such as organic solderability preservative (OSP), immersion tin (ImSn), immersion silver (ImAg), electroless nickel immersion gold (ENIG), or electroless nickel electroless palladium immersion gold (ENEPIG), cannot effectively prevent Cu substrate corrosion. It is necessary to develop new surface finishes to protect the substrate in electronic devices. This study proposes a single layer Co, multilayer Co/Pd, and Co/Pd/Au as new surface finishes to investigate the ability of corrosion resistance. The test only uses SO2 as corrosive gas to avoid interference from other gas. Furthermore, corrosive gas concentration in the common corrosion test standard is often used in the parts per billion level. To observe the corrosion resistance of the coating layer in harsh environment, corrosive gases concentration is increased to the parts per million (ppm) level. The test parameters are set at 80 C and 100% RH and react for 240 h. After the corrosion test, the slight corrosion products are grown on the coating layer surface, and the components of the corrosion products are cobalt oxide. To analyze the mechanism of the corrosion reaction in the coating layer, samples are placed in 1.68 M H2SO4 solution for electrochemistry test and 1500 ppm SO2 for failure test. The test results show that all the Co layer was exhausted to form corrosion products. It indicates that the addition of Pd and Au layers can improve the corrosion resistance of the Co layer, but the corrosive solution can pass through the Pd and Au layers to react with the Co layer. Nonetheless, no Cu signal can be detected from the corrosion products. Based on the study results, the Co-based layer can be used as a sacrificial layer to protect the substrate in the harsh environment. The Co-based layer can be used as a new surface finishing material to improve the reliability of electronic devices.
Appears in Collections:	[National Central University Department of Chemical & Materials Engineering] Electronic Thesis & Dissertation

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