| 摘要 |
PROBLEM TO BE SOLVED: To improve the soldering strength by providing the soldering material in which copper, platinum, and gold of the prescribed quantity, and the conductor pattern is formed of a nickel layer containing phosphor of the prescribed quantity and a gold layer to cover the nickel layer. SOLUTION: The soldering material 12 has the composition consisting of, by weight, 0.1-20% copper, 0.01-20% platinum, 0.001-5% gold, and silicon, and the balance 10-70% lead and 30-90% tin. A copper foil is attached to the surface of an insulated substrate 7. The copper foil is etched to form a copper layer 30 of a pad 3. A nickel layer 31 having the composition consisting of, by weight, 3-12% phosphor and the balance nickel is formed on the surface of the copper layer 30. A gold layer 32 is formed on the nickel layer 31. Preferably, the thickness of the nickel layer is 0.1-30μm, and the thickness of the gold layer is 0.01-10μm. A copper ball 11 is covered with the soldering material 12 to form a solder ball 1, and the solder ball is placed on the pad 3. The solder ball 1 is heated and method to be joined with the pad 3, and the copper ball 11 is diffused in the soldering material 12.
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