Investigation of soldering process and interfacial microstructure evolution for the formation of full Cu₃Sn joints in electronic packaging

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• 作者：Peng Yao ; ^{kaka3778@126.com} ; Xiaoyan Li ; Xiaobo Liang ; Bo Yu
• 关键词：Electronic packaging ; Full Cu3Sn joints ; Soldering temperature ; Soldering pressure ; Soldering time ; Interfacial microstructure evolution
• 刊名：Materials Science in Semiconductor Processing
• 出版年：2017
• 出版时间：February 2017
• 年：2017
• 卷：58
• 期：Complete
• 页码：39-50
• 全文大小：1756 K
• 卷排序：58

文摘

Within electronic products, solder joints with common interfacial structure of Cu/IMCs/Sn-based solders/IMCs/Cu cannot be used under high temperature for relatively low melting points of Sn-based solders (200–300 °C). However, there is a trend for solder joints to service under high temperature because of the objective for achieving multi-functionality of electronic products.With the purpose of ensuring that solder joints can service under high temperature, full Cu3Sn solder joints with the interfacial structure of Cu/Cu3Sn/Cu can be a substitute due to the high melting point of Cu3Sn (676 °C). In this investigation, soldering process parameters were optimized systematically in order to obtain such joints. Further, interfacial microstructure evolution during soldering was analyzed. The soldering temperature of 260 °C, the soldering pressure of 1 N and the soldering time of 5 h were found to be the optimal parameter combination. During soldering of 260 °C and 1 N, the Cu6Sn5 precipitated first in a planar shape at Cu-Sn interfaces, which was followed by the appearance of planar Cu3Sn between Cu and Cu6Sn5. Then, the Cu6Sn5 at opposite sides continued to grow with a transition from a planar shape to a scallop-like shape until residual Sn was consumed totally. Meanwhile, the Cu3Sn grew with a round-trip shift from a planar shape to a wave-like shape until the full Cu3Sn solder joint was eventually formed at 5 h. The detailed reasons for the shape transformation in both Cu6Sn5 and Cu3Sn during soldering were given. Afterwards, a microstructure evolution model for Cu-Sn-Cu sandwich structure during soldering was proposed. Besides, it was found that no void appeared in the interfacial region during the entire soldering process, and a discuss about what led to the formation of void-free joints was conducted.