- 學位論文
改質銀漿之抗腐蝕研究
A study on anti-sulfurization of modified silver paste
摘要
銀主要用於電子產品中，因為銀非常不容易氧化，且具有非常高的導電性，但容易與大氣中的硫化物產生Ag2S和Ag2SO4，從而影響銀的外觀與物理性質。本研究在銀漿中摻雜不同元素使銀具抗腐蝕性，此銀漿稱改質銀漿，摻雜元素選擇Cr與W其含量為(2.5、5、7.5、10 wt.%)，將最佳抗硫化特性之二元改質銀漿再摻雜第三種元素，選以Sn與Zn含量為 (0.5、1.5與3 wt.%)，探討改質銀漿之相結構、顯微結構以及抗腐蝕性。 實驗結果顯示，Ag-W改質銀漿與Ag-Cr改質銀漿在燒結溫度為800 °C時，有較緻密的結構。從XRD分析結果顯示，經摻雜W與Cr改質銀漿均產生二次相，分別為α-Ag2WO4與AgCrO2。在顯微結構部分，可發現Ag-W改質銀漿晶粒較大，且緻密性較高，原因為在燒結過程中形成α-Ag2WO4低溫相，此相有助於銀顆粒重新排列，達到幫助燒結效果。而Ag-Cr改質銀漿在燒結過程中形成AgCrO2，反而不易燒結，導致內部孔洞較多，在內部孔洞較多的情況下會導致腐蝕速率加快。由於兩種改質銀漿皆在晶界處產生二次相，抵擋S元素的侵蝕，使電位差向正的方向移動，提升抗腐蝕能力。隨後與市面上Ag-Pd漿進行比較，發現二元改質銀漿腐蝕電位均高於Ag-Pd漿，但腐蝕速率較快，原因為二元改質銀漿表面鈍化層失效後內部Ag會迅速地被腐蝕，而Ag-Pd漿形成固溶體使S不易與Ag產生反應，故腐蝕速率較慢。 選用2.5 %W-Ag為二元改質銀漿最佳比例，再摻雜第三元素Sn或Zn，在燒結溫度為800 °C時，發現有較緻密的結構，由XRD分析結果顯示Ag-W-Sn改質銀漿在燒結過程中形成SnO2，而不易燒結成型，進而抑制燒結使晶粒變小，如此可有效的降低腐蝕速率。而Ag-W-Zn改質銀漿在燒結時形成ZnWO4，導致晶粒變小，內部孔洞較多，造成電阻率提高，且腐蝕後造成孔蝕現象，顯示第三元素Zn的摻雜無助於增強抗腐蝕性。
並列摘要
Silver is mostly used in the electronics industry because it is not easily oxidized in the environment and has exceptional conductivity. However, silver easily interacts with sulfides in the atmosphere to form Ag2S, Ag2SO4, which influences on the physical properties and silver appearance. This study intends to use doping elements within the silver paste to reduce the corrosion. The addition content of doped element (W and Cr) is 2.5, 5, 7.5, 10 wt.%, respectively. According to the anti-sulfurization results of Ag-X ( Cr, W) paste, the Ag-2.5%W paste has a better performance. Therefore, a third element (Sn, Zn) is added in the Ag-2.5%W paste. Experimental results showed that Ag-W and Ag-Cr modified silver paste have a denser structure when sintered at 800 °C. The XRD analysis showed that the secondary phase was existed when W or Cr added in silver paste, the secondary phase was α-Ag2WO4 and AgCrO2, respectively. In addition, it is found that the microstructure of Ag-W modified paste has larger grains. It could be due to the formation of α-Ag2WO4 phase. Furthermore, AgCrO2 phase was observed in Ag-Cr modified paste sintered at >600C; however, many pores were found after sintering. As a result, increasing internal pores will lead the corrosion rate. Since both modified silver pastes produce secondary phases at the grain boundaries, they resist the erosion of the S element, and improve the corrosion. Commercial Ag-Pd paste was used as comparison. It was found that the corrosion potential of the binary modified silver paste was higher than commercial Ag-Pd paste; however, the corrosion rate of Ag-W and Ag-Cr were faster than Ag-Pd. The Ag-Pd forms a solid solution to make S difficult to react with Ag, so the corrosion rate is slower. The addition of Ag-2.5%W as the binary modified silver paste and addition a third element such as Sn or Zn was carried out. It found denser structure when Ag-2.5%W-X modified paste sintered at 800 °C. The XRD analysis showed that Ag-W-Sn modified paste have SnO2 phase after sintering, which the grain size is inhibited to be smaller. However, it can effectively reduce the corrosion rate. The ZnWO4 phase was formed in Ag-W-Zn modified paste after sintering, which leads to smaller grain size and more internal pores, resulting in increased resistivity and pitting after corrosion. This shows that the third element, Zn doping is not more effective corrosion resistance.