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    Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/3987


    Title: Cu濃度對銲接時墊層消耗速率及界面反應的影響;Dissolution and Interfacial Reaction between Cu and Sn-Ag-Cu Solders
    Authors: 張智強;Chih-Chiang Chang
    Contributors: 化學工程與材料工程研究所
    Keywords: 無鉛銲料;界面反應;消耗速率;銅濃度;interface reaction;Lead-free Solder;Cu concentration;dissolution rate
    Date: 2007-06-27
    Issue Date: 2009-09-21 12:27:48 (UTC+8)
    Publisher: 國立中央大學圖書館
    Abstract: 由於SnAgCu 系列銲料有很多不同組成,而以何種組成為最理想,目 前並無定論,且現今在電子封裝中最常使用表面處理層為OSP/Cu 與 Au/Ni,其中由於OSP/Cu 表面處理層價格低廉。因此本研究將探討當銲錫 球與Cu 墊層相接時,SnAgCu 系列銲料中Cu 濃度所扮演的腳色。而且現 今電子產品發展走向輕薄短小的趨勢,使得IC 晶片邁向高I/O 數的趨勢, 因此銲點的縮小更是勢在必行,所以縮小銲點所造成的影響也很重要。因 此本研究之總目標是去深入了解不同體積與不同Cu 濃度之SnAgCu 銲錫球 與OSP/Cu 發生反應時每一階段的現象及其機制。 本研究之目的是在探討SnAgCu系銲料之Cu濃度與體積變化對銲接反 應與介金屬生長形態的影響。本實驗係以760、500 μm 兩種不同直徑的銲 錫球,來對開孔600 μm 的Cu 墊層進行銲接反應。其中SnAgCu 銲錫球的 Cu 濃度分別為0、0.3、0.5 及0.7 wt.%,並且所選用的廻銲頂溫是235℃。 廻銲時間設定為90 秒並且分別進行1~5 次的廻銲,在廻銲過後觀察其反應 結果的截面積與上視圖,並且以掃描式電子顯微鏡(Scanning Electron Microscope, SEM, HITACHI S-3000N)觀察界面的介金屬型態,並以電子微 探儀(Electron Probe Microprobeanalyzer, EPMA, JEOL JXA-8500F)進行各相 組成分析,並利用推球機(XYZTEC CONDOR-100)在不同迴銲條件下測試 其銲點的剪力強度。 而由反應結果的微結構圖與數據可以發現銲錫球所消耗的Cu 墊層厚度 與界面介金屬的生長厚度主要是受到不同Cu 濃度銲錫球、廻銲時間與銲料體積的影響。其中銲錫球中初始的Cu 濃度高低,主要會改變Cu 墊層與熔 融銲料間的濃度梯度,進而導致不同的溶解驅動力,而使Cu 墊層溶解速率 發生改變,而界面介金屬晶粒也隨之成長。不同的廻銲時間,會使得界面 介金屬厚度與晶粒大小明顯的有所變化,而最後利用質量平衡可以發現 到,無論初始銲錫球中Cu 濃度的高低,在不同次數的廻銲後銲錫球中Cu 濃度皆會因為達到溶解 平衡而維持在一定值。 另外已有研究指出,在 Cu3Sn/Cu 界面會產生一連續的Kirkendall’s Voids。而此一連續的Kirkendall’s Voids 會導致Solder/Cu 界面的脆化而使 銲點剪力強度的下降,本實驗室曾經發現到在SnAgCu 系銲料中添加微量 的Ni 成分在長時間的反應下,可以有效抑制Cu 端的Cu3Sn 生成。並由 SnCuNi 三元相圖可知微量Ni 成份的添加會使得Cu 在Sn 中的溶解極限快 速下降,因此在本研究中會另外進一步的探討當銲料中添加微量Ni 成份對 於Cu墊層消耗厚度和界面介金屬型態與厚度以及對迴銲後Cu濃度的影響。 此研究主要是利用組成Sn3Ag0.5Cu0.02Ni 直徑分別為300、400、600、 760μm 的銲錫球與開孔600μm 的Cu 基材相接後在235℃頂溫下經過1~5 次的迴銲後,觀察其界面反應結果與測試其銲點的剪力強度。 此研究發現微量的Ni 成份的添加其界面生成之介金屬為 (Cu1-xNix)6Sn5。並可以有效的的降低Cu 在Sn 中的溶解極限,而使得界面 介金屬形狀會由貝殼狀轉變成菱柱狀,且會促使大量的介金屬在界面析 出,並在界面的介金屬觀察到有些微孔隙的生成。有趣的Ni 的添加對於 Cu 墊層的消耗厚度並無太大影響。現今電子封裝業走向輕薄短小的趨勢, 因此銲點的縮小是可以預見的,而在本研究中當含Ni 銲點體積縮小時,其界面介金屬厚度會隨之下降,Cu6Sn5 中溶Ni 量也有下降的趨勢,而且介金 屬的形狀也由結晶顆粒較大的菱柱狀轉變為結晶顆粒較小的貝殼狀。亦即 添加Ni 成分的銲點體積的不同會影響界面生成物其生長型態的轉變,因此 當未來銲點持續縮小時,含Ni 銲點體積大小對於界面反應也會有所影響。 In electronic packing, the dissolution of thin film under-bump metallizations (UBMs) and surface finishes in molten lead-free solders is one of the most important processing concerns. Due to a higher melting temperatures and richer Sn content, molten lead-free solder such as SnAgCu tend to dissolve the UBMs and surface finishes at faster rates than the eutectic SnPb. The SnAgCu solder are a series of lead-free solders with broad compositions. The OSP/Cu surface finish is the most common and important for solder pad and bumps in industry now. One of the important reasons for using Cu in packaging assemblies is that it provides good electrical conductivity. Therefore, the overall objective is to study in depth the reaction between the SnAgCu solders with various Cu concentrations, solder ball volume and the OSP/Cu. In this study, solder balls of different concentrations Sn3AgxCu (x=0/0.3/0.5/0.7wt.%) and different diameters, 500 μm or 760 μm were employed to study the influence of solder volume as well as the Cu concentration. The solder pad had the OSP/Cu surface finish. The pad opening diameter was 600 μm. The solder balls were placed on pad, and then reflowed for 90–450 sec at peak reflow temperature of 235℃. The microstructureal analyses of samples were obtained using a SEM, and the composition of reaction product was identified by JEOL JXA-87600SX electron microprobe (EPMA). It was found that the Cu concentration and solder ball volume in the SnAgCu ternary solder has very strong effect on the Cu consumption thickness and compound formation in solder joints with the OSP/Cu surface finish. The different Cu concentration in the SnAgCu ternary solder changed the Cu concentration gradient and dissolution driving force between molten-solder and Cu pad. The interfacial IMC layers thickness and grain size increased with increasing number of reflow times. From mass balance of Cu, whatever initial Cu concentration in the SnAgCu ternary solder ball the Cu concentration will reach dissolution equilibrium to maintain constant at various reflow times. The results of this study suggested that a high Cu-content SnAgCu solder should be used to prevent the chip failed due to molten solder dissolved nearly all the Cu from the Cu pad.
    Appears in Collections:[化學工程與材料工程研究所] 博碩士論文

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