| 摘要 |
PROBLEM TO BE SOLVED: To increase adhesion and prevent pads for external connection from becoming brittle by allowing the pads for external connection to have a smaller content of Sn than Sn-containing solder for connection and covering the pads for external connection with solder layers of a higher melting point. SOLUTION: Pads 11 for external connection formed on a flip chip circuit board 10 are covered with solder layers 12. The solder layers 12 are made of solder including a smaller amount of Sn than solder balls 13 for external connection (Sn-containing solder for connection) and having a high melting point. The solder balls 13 for connection include 59-65wt.% of Sn and the solder constituting the solder layers 12 contains 1-19wt.% of Sn. By this method, the solder layers 12 have an excellent adhesion with the pads 11 for external connection and with the Sn containing solder for connection and connection interfaces between the Sn-containing solder for connection and the pads 11 for external connection are prevented from becoming brittle. |
