| 摘要 |
PROBLEM TO BE SOLVED: To provide a circuit board excellent in long-term reliability.SOLUTION: A substrate for mounting an electronic element of the present invention includes: an insulating base 11; and a metal plate 12 which is joined to a main surface of the insulating base 11 by a brazing filler metal 3 containing Cu and Ag and has a first metal part 121 containing Cu and a second metal part 122 having a thermal expansion coefficient smaller than that of the first metal part 121, which are laminated together. The brazing filler metal 3 covers at least part of a side surface of the first metal part 121. The first metal part 121 has an Ag mixed portion 121b in contact with the brazing filler metal 3. |
