Soldering Process
Soldering is the major micro-joining process for assembling printed circuit boards of electronic products and is an important method of joining two metals without melting of base metals. In light of the remarkable progress in recent years in electronic pr
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Soldering Process Hiroshi Nishikawa
Abstract Soldering is the major micro-joining process for assembling printed circuit boards of electronic products and is an important method of joining two metals without melting of base metals. In light of the remarkable progress in recent years in electronic products, the micro-joining process represented in soldering to incorporate devices and components into such products has become an essential technology. It can be truly said that soldering and electronics assembly technology have progressed with electronic products. In this chapter, the status of development and research of soldering and cutting edge joining process substituting for soldering are explained. In particular, in the first half, we will discuss development in Japan concerning lead-free solder, and the second half will look into research on materials with the potential to replace high-lead-containing solder for high-temperature applications. Keywords Lead-free solder (NPB)
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High-temperature bonding Nanoporous bonding
History and Definition of Soldering
12.1.1 Sn-Pb Solder Soldering has an extremely long history, and it has been indispensable as a process to join both similar and dissimilar metals. Lead-based solder seems to date to 3800 B.C., when it was used for artistic purposes to produce ornaments. This process has been developed through repeated trial and error over many years. In addition, understanding of the phenomena and characteristic related to soldering, such as wetting, diffusion, and dissolution, has been deepened to develop and establish this process. H. Nishikawa (&) Joining and Welding Research Institute, Osaka University, Ibaraki, Japan e-mail: [email protected] © Springer Nature Singapore Pte Ltd. 2019 Y. Setsuhara et al. (eds.), Novel Structured Metallic and Inorganic Materials, https://doi.org/10.1007/978-981-13-7611-5_12
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H. Nishikawa
Solder is defined in the Japanese Industrial Standards (JIS) as a “filler metal with a liquidus temperature of less than 450 °C”. It is also referred to as “soft solder”. A typical example of soldering is a joining for a printed circuit board (PCB) with high density in electronics products. The number of joints on one board for the products exceeds several thousand points. One major advantage of the soldering is that it can join thousands of parts collectively. Another advantage is that the soldering can be conducted under the melting point of base metals. For a long time, the most widely used solder was the Sn-Pb eutectic alloy, which has a melting point of 183 °C. To be able to form a metallic bond with Cu at such a low temperature is the key reason why the Sn-Pb eutectic solder has been used worldwide for so long. The advantages of soldering are listed below. • Enables a simultaneous joining of multiple points. • Enables the formation of interconnection without melting or significant damage to the base metal. • Enables interconnection of dissimilar materials. • Enables interconnection with superior electric and thermal propert
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