| 摘要 |
PURPOSE: To prevent metal hardening by nickel and demoisturization damage to soldered joint by nickel oxide by providing a thin copper barrier layer between a metal layer and a nickel layer thick enough to prevent nickel from diffusing through metal. CONSTITUTION: Two terminal pads 16 on a circuit board 11 have, upwardly in turn, a plurality of layers including a titanium layer 21, a palladium or a palladium-titanium alloy layer 22, a copper layer 23, a nickel layer 24, a copper barrier layer 25, and a gold layer 26. The copper barrier layer 25 deposited on the nickel layer 24 is formed with thickness in the range of 200 to 1000 nm and provided with the gold layer 26 on the top of the copper barrier pattern by electroplating. A region of exposed nickel is oxidized to form a thin, heat- resistant nickel oxide layer after depositing the copper barrier and gold. The nickel oxide as a soldering barrier prevents solder from diffusing form a bump on a IC package through the gold boundary to the surface of the nickel. |
