| 摘要 |
PROBLEM TO BE SOLVED: To reduce thermal stress imposed on a solder fillet so as to decrease or prevent a crack that occurs and develops in solder to lead to a through fracture. SOLUTION: Lands 12 are formed on the surface of a circuit board 11, and a chip part 13 is bonded on the lands 12 with solder 14. The two lands 12 are so formed as to make a distance between their tips equal to that between the internal ends of the two electrodes 15 of the chip part 13. The slope 18 of the solder fillet 17 is composed of a first part 18a close to the slope 15a of the chip part 13 and a second part 18b close to the land 12. The first part 18a close to the slope 15a forms an angle ofθ1 with the surface of the land 12, whereinθ1 is set at 50°or smaller. The second part 18b makes an angle ofθ2 with the surface of the land 12, and it is preferable thatθ2 is set at 30°or smaller. COPYRIGHT: (C)2004,JPO&NCIPI
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