| 摘要 |
PROBLEM TO BE SOLVED: To lessen the quantity of the deposition of Au of the bonding pad in the solder joint part and to prevent the deterioration of the joining strength of the solder joint part by setting the thickness of an Au layer in such a manner that the Au content in the solder joint part between a bonding pad having the Au layer on its surface and a bump attains a specific value or below in a state of joining the bonding and the bump. SOLUTION: The bonding pad 12 has a Cu layer 12a, Ni layer 12b and the Au layer 12c on the surface of a base film 11a constituting a flexible substrate 11. A wiring material 13 has the copper bump 13c laminated with a solder layer 13b. When the solder layer 13d is pressed to the bonding pad 12 and the wiring material 13 and the flexible substrate 11 are heated, the solder layer 13d melts and forms the solder joint part. When the thickness of the Au layer 12c is below 0.7μm, the content of the Au in the solder joint part is confined to <=9 wt.%. As a result, the deposition of the compound of Au and Sn in the solder joint part is suppressed and the joining strength of the solder joint part may be enhanced.
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