Structure including copper plating layer or copper alloy plating layer

A structure including a copper plating layer or a copper alloy plating layer, wherein the copper plating layer or the copper alloy plating layer is a plating layer which is formed by:

• performing an electroplating process at a prescribed first cathode current density by using a copper or copper alloy electroplating bath;
• and then
• completing the electroplating process after the prescribed first cathode current density is changed to a second cathode current density which is lower than the prescribed first cathode current density,
• the prescribed first cathode current density is an average cathode current density in the electroplating process which is performed by combining a plurality of cathode current densities until the first cathode current density is changed to the second cathode current density,
• the average cathode current density is calculated in accordance with a formula (1):
• Average Cathode Current Density
• =[Cathode current density]n1×([Plating time]n1/Total plating time)+[Cathode current density]n2×([Plating time]n2/Total plating time) . . . . . . +[Cathode current density]n−1×([Plating time]n−1/Total plating time)+[Cathode current density]n×([Plating time]n/Total plating time) (1)
• in which the plurality of cathode current densities are n cathode current densities,
• [Cathode current density]n1 is a 1st cathode current density,
• [Cathode current density]n2 is a 2nd cathode current density, . . . . . .
• [Cathode current density]n−1 is an (n−1)th cathode current density,
• [Cathode current density]n is an nth cathode current density,
• [Plating time]n1 is a time of plating performed at [Cathode current density]n1,
• [Plating time]n2 is a time of plating performed at [Cathode current density]n2, . . . . . .
• [Plating time]n−1 is a time of plating performed at [Cathode current density]n−1, and
• [Plating time]n is a time of plating performed at [Cathode current density]n,
• the prescribed first cathode current density is greater than or equal to 5 A/dm2,
• a layer which is formed by changing the prescribed first cathode current density to the second cathode current density is a surface layer part of the copper plating layer or the copper alloy plating layer, and
• the surface layer part has a thickness of 0.05 μm to 15 μm,
• the structure further including a plating layer of metal or a metal alloy other than copper adjacently to the copper plating layer or the copper alloy plating layer, wherein:
• after a heat process for the structure at 180° C. for 300 hours, at a bonding interface between:
• the copper plating layer or the copper alloy plating layer;
• and the plating layer of metal or a metal alloy other than copper,
• no Kirkendall void is observed, or
• less than 5 Kirkendall voids each having a size smaller than 1 μm are observed, and no Kirkendall void having a size larger than or equal to 1 μm is observed.