Low-temperature Pb-free solders have been introduced into step soldering to eliminate thermal damage. Low-temperature solder development aims to reduce carbon dioxide emissions. The BiIn solder is considered a potential candidate because of its low melting point. The joint connections between the BiIn solder and substrate are interesting, yet critical subjects. BiIn solder is an environment friendly alternative to lead-bearing solders for electronic packaging. This study aimed to investigate the interfacial reactions. Bi48In/Cu and Bi33In/Cu were obtained after multiple reflows. The aging reactions between Bi48In and Cu were systematically analyzed. Phase identification of the intermetallic compounds formed at the interface was performed using bulk-type Cu11In9 and grooved Cu11In9 + In after aging. The groove Cu11In9 + In existing near the Cu substrate is attributed to the phase transformation during aging. Uneven Cu-In compound growth may lead to several problems, such as reduced joint strength. A modified solder or substrate, such as minor element addition or surface finishing, can improve the uneven Cu-In compound growth. The aforementioned methods will be studied further in the future. This study provides insights into the growth mechanism of the interfacial reactions between BiIn solders and Cu substrates.
關聯:
Journal of Materials Science: Materials in Electronics 36, 44
