The effect of storage time and nickel layer on electroplated Cu/Sn interfacial reaction

電子封裝製程，常以銲料連接各電子元件，鉛金屬已被證實神經毒性，傷害生殖系統和胚胎發展，考量環境保護等議題，近來已逐漸被無鉛銲料取代，錫為無鉛銲料之主要元素，錫與銅界面反應形成介金屬化合物IMC(intermetallic compound)，其結構影響銲點的可靠性，前人研究，有些電鍍銅添加劑會影響IMC結構，在IMC層形成孔洞與雜質。本研究著重在探討電鍍銅貯存時間及鎳層對IMC的影響。 以電鍍銅為基材，PC電鍍銅配方有添加劑PEG 200 ppm、Cl- 60 ppm，電鍍銅與錫迴銲於260℃ 30s，其介金屬層生成孔洞之層狀結構，為了解電鍍銅放置後，貯存時間是否影響介金屬結構的孔洞與雜質，進行貯存時間實驗，貯存條件為25~30℃，濕度60%~70%。由實驗結果，貯存時間0~720h對IMC厚度影響不大，而150℃、200℃熱處理，貯存時間對銲點雜質差異不大。 鎳層可作為銅與錫的阻障層，鎳與錫形成介金屬Ni3Sn4，避免銅錫介金屬過度生成，PC配方電鍍銅再電鍍上一層鎳，觀察銅/鎳/錫界面結構。由實驗結果，阻障層鎳可避免銅錫快速擴散，當熱處理時間增加，鎳逐漸擴散進入錫銲料，阻障層越來越薄，消耗完後，銅錫進行界面反應，生成介金屬(Ni,Cu)6Sn5、(Ni,Cu)3Sn，介金屬層厚度增加，並觀察到些許孔洞。Solder used in packaging comprehensively connects to electronic components. Lead solder poisoning and toxic is proved. The Restriction of Hazardous Substances Directive (RoHS) adopted in 2003, and lead is also restricted substance. Products contain lead solder should be replaced to lead-free solder. Tin is the major element in lead-free solder, and tin reacting with copper forms intermetallic compound (IMC). That may affect mechanical properties of joints. In recent years, some research revealed that electroplating additives affect microstructures of IMC. In this study, the effect on storage time and nickel layer on electroplated Cu/Sn interfacial reaction is discussed. The substrate is copper, and electroplated with additives (PEG、Cl-). It jointed with pure tin at 260℃ for 30s.After heat aging in 200℃, forming several ribbon-like structures in IMC layer. To examine the effect on storage time, the electroplated Cu stores at room temperature(25~30℃, relative humidity 60%~70%) for 0 h to 720 h, then heat aging in 150℃ or 200℃. Heat aging in 150℃ or 200℃, differences between storage time and the impurity are not characteristic. Nickel layer acts as a barrier between the Cu and Sn. Ni reacting with Cu forms IMC(Ni3Sn4), avoids the excess IMC layers forming . In this study, nickel electroplated on the PC substrate .After heat aging in 150℃, nickel layer is consuming and Ni3Sn4 layer becomes thicker. (Ni,Cu)6Sn5 and (Ni,Cu)3Sn will form after consumption of Ni layer, and voids appear on Cu/(Ni,Cu)3Sn.致謝 i 中文摘要 ii Abstractiii 目錄 iv 表目錄 v 圖目錄 vi 1 前言 1 2 文獻回顧 2 2.1 無鉛銲料 2 2.2 電鍍銅與添加劑 2 2.3 銅/錫系統擴散反應 12 2.4 鎳/錫系統擴散反應 14 3 實驗方法 17 3.1 電鍍銅基材製備 17 3.2 電鍍鎳基材製備 18 3.3 有機保焊劑 19 3.4 錫/電鍍銅及錫/鎳液/固界面反應 19 3.5 錫/電鍍銅及錫/鎳熱處理 19 3.6 金相分析 19 4 結果與討論 20 4.1 PC電鍍銅貯存時間與不同熱處理時間 20 4.2 PC電鍍銅/鎳/錫反應不同熱處理時間 33 5 結論 41 6 參考文獻 4