錫銀銲錫與不同厚度的銅鎳金屬層之冶金反應研究

Abstract

銅鎳被普遍的應用在Bumping產業之金屬層UBM Layer （Under Bump Metallization Layer）。本論文研究無鉛錫銀銲錫（Lead Free Solder）97.5wt%Sn-2.5wt%Ag凸塊，在不同的UBM電鍍銅層厚度（5/2/0μm-Cu）與固定電鍍鎳層厚度（3μm-Ni）及錫銀層間的冶金反應。並比較不同的UBM電鍍銅層厚度的樣品在高溫儲存及多次迴銲測試後之冶金反應及可靠度結果。 根據本文實驗的研究結果，可發現三種不同厚度條件的Cu/Ni層在多次迴銲和固態時效後之冶金反應，無論在高溫儲存、多次迴銲及部分可靠度測試下，其推力測試的破裂面均為在銲錫內部的延性破裂；且剪力強度皆可以達到業界規範的標準內。但需注意本論文提供的實驗項目仍有部分可靠度及電遷移性質未做分析。 另外，Cu/Ni為0/3μm的樣品，在高溫儲存下，其介金屬化合物Ni3Sn4在150℃之成長速率常數約為0.054μm/小時^1/2，估算其鎳的消耗速率常數為0.0152μm/小時^1/2；在多次迴銲下，其介金屬化合物Ni3Sn4之成長速率常數約為0.228μm/min^1/2，估算其鎳的消耗速率常數為0.081μm/min^1/2。

Cu/Ni has been generally used as an under-bump metallization (UBM) layer in the bumping industry. The purpose of this thesis was investigated in the Sn/Ag interface metallurgy reaction of 97.5wt%Sn-2.5wt%Ag lead-free solder bump between different electroplated Cu layer thickness (5/2/0μm-Cu) and fixed electroplated Ni layer thickness (3μm-Ni). Furthermore the metallurgy interaction and reliability test were also compared of samples with different electroplated Cu layer thickness at thermal aging and re-reflow tests. Experiment results showed that the fracture mode are all internal ductile fracture of Sn/Ag under re-reflow and solid-state aging condition for three kinds of different Cu/Ni thickness and the shear strength could also meet the criteria as well. Please notice that that some items of this experiment are still under reliability and electromigration test. In addition, for 0/3μm Cu/Ni sample, the growth rate constant of Ni3Sn4 is about 0.054μm/hr^1/2 at 150℃ and the consumption rate constant of Ni is about 0.0152μm/hr^1/2 under high temperature storage condition; the growth rate constant of Ni3Sn4 is about 0.228μm/min^1/2 and the consumption rate constant of Ni is about 0.081μm/min^1/2 under re-reflow condition.