| 摘要 |
PROBLEM TO BE SOLVED: To provide a wiring substrate which can have the electrode of a semiconductor element tightly connected to a solder connection pad for semiconductor element connection through a solder bump and a solder connection pad for external connection tightly connected to the wiring conductor of an external electric circuit substrate through a solder ball, and thereby has excellent reliability of mounting of the semiconductor element on the wiring substrate and excellent reliability of mounting of the wiring substrate on the external electric circuit substrate. SOLUTION: The wiring substrate is constituted by covering surfaces of solder connection pads 3 and 4 made of copper with an electroless tin plating layer 6 containing silver to a thickness of 1.5 to 2.0 μm, and the electroless tin plating layer 6 has a silver segregation layer of 1.0 to 5.0 mass% in content of silver formed on its surface. It is preferable that the content of the silver on the surface of the tin plating layer 6 is smaller than that of the silver in the inside of the surface of the tin plating layer 6. COPYRIGHT: (C)2010,JPO&INPIT
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