Li Yu-Ju, Yen Yee-Wen, Chen Chih-Ming
Department of Chemical Engineering, National Chung Hsing University, 145 Xingda Rd., South Dist., Taichung 402202, Taiwan.
Department of Materials Science and Engineering, National Taiwan University of Science and Technology, 43 Keelung Rd., Sec.4, Da'an Dist., Taipei 106335, Taiwan.
Materials (Basel). 2024 May 4;17(9):2149. doi: 10.3390/ma17092149.
Sn-3Ag-0.5Cu (SAC305)- and Sn-9Zn-based alloys (Sn-Zn-X, X = Al, In) are lead-free solders used in the fabrication of solder joints with Cu metallization. Electroplating is a facile technology used to fabricate Cu metallization. However, the addition of functional additive molecules in the plating solution may result in impurity residues in the Cu electroplated layer, causing damage to the solder joints. This study investigates the impurity effect on solder joints constructed by joining various solder alloys to the Cu electroplated layers. Functional additives are formulated to fabricate high-impurity and low-impurity Cu electroplated samples. The as-joined solder joint samples are thermally aged at 120 °C and 170 °C to explore the interfacial reactions between solder alloys and Cu. The results show that the impurity effect on the interfacial reactions between SAC305 and Cu is significant. Voids are massively formed at the SAC305/Cu interface incorporated with a high impurity content, and the CuSn intermetallic compound (IMC) grows at a faster rate. In contrast, the growth of the CuZn IMC formed in the SnZn-based solder joints is not significantly influenced by the impurity content in the Cu electroplated layers. Voids are not observed in the SnZn-based solder joints regardless of the impurity content, indicative of an insignificant impurity effect. The discrepancy of the impurity effect is rationalized by the differences in the IMC formation and associated atomic interdiffusion in the SAC305- and SnZn-based solder joints.
Sn-3Ag-0.5Cu（SAC305）和Sn-9Zn基合金（Sn-Zn-X，X = Al、In）是用于制造具有铜金属化层焊点的无铅焊料。电镀是一种用于制造铜金属化层的简便技术。然而，在电镀溶液中添加功能性添加剂分子可能会导致铜电镀层中残留杂质，从而对焊点造成损害。本研究调查了杂质对通过将各种焊料合金与铜电镀层连接而构建的焊点的影响。配制功能性添加剂以制造高杂质和低杂质的铜电镀样品。将连接后的焊点样品在120°C和170°C下进行热老化，以探索焊料合金与铜之间的界面反应。结果表明，杂质对SAC305与铜之间的界面反应影响显著。在杂质含量高的SAC305/铜界面大量形成空洞，并且CuSn金属间化合物（IMC）生长速度更快。相比之下，在SnZn基焊点中形成的CuZn IMC的生长不受铜电镀层中杂质含量的显著影响。无论杂质含量如何，在SnZn基焊点中均未观察到空洞，这表明杂质影响不显著。通过SAC305基和SnZn基焊点中IMC形成及相关原子相互扩散的差异，解释了杂质影响的差异。
