本研究係探討95Pb5Sn銲錫合金薄帶試片以及95Pb5Sn與63Sn37Pb的覆晶複合銲錫接點，於通電過程電遷移所導致之微觀組織變化與再結晶行為。95Pb5Sn銲錫合金薄帶試片，於室溫下施加6×10^3A/cm^2，利用臨場同步輻射XRD分析討論鉛與錫繞射峰的消長變化； 95Pb5Sn與63Sn37Pb的覆晶複合銲錫接點試片，施加2.1，3.3，4.2，4.6以及5.0×10^4A/cm^2，5種不同的電流密度，利用SEM及EDX即時連續觀察方法分析討論錫鉛接點微結構和成分變化。
95Pb5Sn銲錫薄帶的鉛的繞射峰，最強的是(222)，其次依序是(311)， (200)，(220)和(111)等結晶面，通電過程，結晶面逐漸消失，剩下(111)和(200)繞射峰，並且鉛(111) 和(200)的位置都有稍微向低角度偏移2θ 0.1度，更長時間通電，則鉛的結晶面完全消失。而錫原有的繞射峰(211)以及(321)於通電過程完全消失。停止通電後，逐漸出現鉛(200) 、(220) 和(111)繞射峰，以及錫(211)繞射峰。
覆晶複合銲錫接點於通電過程，於SEM之觀察，出現富錫相完全消失(溶解)之現象，此行為對應著一臨界電流密度，低於此臨界電流密度，富錫相並不溶解。此溶解行為依電流密度變化，具有兩個活化能Q1=38kJ/mol(當電流密度大於4.2×10^4A/cm^2)以及Q2=159kJ/mol(當電流密度小於4.2×10^4A/cm^2)。施加4.2×10^4A/cm^2電流密度，錫在鉛的濃度為7.00wt%，幾乎為熱平衡濃度的2倍。
富錫相與鉛晶格長時間受到電子撞擊時，鉛晶格膨脹，富錫相則發生溶解行為，固溶至富鉛基地相。停止通電後，鉛晶格恢復，80分鐘到120分鐘之間，富錫相再度析出。富錫相於電流停止之後，再結晶析出為奈米纖維組織。本研究嘗試解析上述電流造成之變化，研提電流造成第二相溶解與過飽和(錫溶於鉛)之原因，以及基地富鉛相與第二相(富錫相)再結晶機制。

This study investigated the effect of electromigration on the microstructure variation and recrystallization behavior of 95Pb5Sn solder strip and flip chip 95Pb5Sn/63Sn37Pb composite solder bump. The solder strip was stressed with 6 × 10^3A/cm^2 electrical current under ambient condition at room temperature. The evolution of the XRD diffraction peaks were investigated with in situ synchrotron XRD; The 95Pb5Sn/63Sn37Pb composite solder bump was stressed with various current densities of 3.3, 4.2, 4.6, and 5.0 × 10^4A/cm^2. The microstructure variation and the composition of the solder joint were investigated with in situ SEM and EDX analysis.
The XRD diffraction peak for Pb of the 95Pb5Sn solder strip was dominated by (222) facet and followed sequentially by (311), (200), (220), and (111). The diffraction peaks diminish gradually upon current stressing. The (200) and (111) disappear last and exhibit slight peak shift, 0.1 degree of 2θ, to the lower angle before they eventually vanish. Sn of the as prepared solder strip exhibits (211) and (321) peaks which disappear completely upon current stressing. The Pb (200), (220), (111) and Sn (211) facets gradually show up after current stops.
The in situ SEM observation of the flip chip composite solder joint shows that the Sn secondary phase gradually disappears (dissolves) upon current stressing. There exists a critical current density below which the Sn does not diminish. The dissolution behavior exhibit two stages, with respect to current density, of which the corresponding activation energies are Q1 = 38kJ/mol (at current densities above 4.2×10^4A/cm^2) and Q2=159kJ/mol (at current densities below 4.2×10^4A/cm^2). The concentration of Sn reaches 7.00 wt% at 4.2×10^4A/cm^2, which is twice as that of the thermal equilibrium solubility.
The above mentioned experimental results indicate that the Pb crystal relaxed upon current stressing, which gives rise to the dissolution of Sn in the Pb matrix. The Pb crystal lattice recovered when current stops and induces the precipitates of the Sn secondary phase. The recrytallization of the Sn-rich phase forms nanorod in the matrix. This study attempted to analyze the behavior of the microstructure variation of the solder upon current stressing. The mechanisms of the dissolution of the secondary phase, the supersaturation of the Sn-in-Pb, and the recrystallization of the primary Pb matrix and secondary Sn phase were proposed after the analysis.

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