Copper circuit junction substrate and method of producing the same

A process for preparing a copper circuit-joined board comprising one joining unit or a laminate of two or more joining units joined to each other or one another, the joining units each comprising a ceramic substrate and a conductor layer, comprising copper as a main component, provided on the ceramic substrate through an interposing layer, said process comprising the steps of:

• (1) providing a ceramic substrate;
• (2) providing conductor materials, the length and width in the planar direction of the conductor materials each in its portion to be directly joined to the interposing layer being at least 0.05 mm shorter than those in the planar direction of the interposing layer, the conductor materials being in such a form that, after joining, at least a part of the end in the planar direction of the portion not to be joined directly to the interposing layer is extended from the end of the interposing layer in at least one of the joining units;
• (3) selecting the materials, for each lamination unit, as a conductor layer material, disposing a material for the interposing layer between the substrate and the conductor layer material to prepare a joining unit, and then providing the joining unit by one as a joining assembly or repeatedly laminating the joining unit twice or more on top of each other or one another to prepare a joining assembly;
• (4) heating the assembly in the temperature range of the melting point of the component(s) of the interposing layer to below the melting point of the conductor layer material to form a joined body;
• and (5) finishing the joined body.

A process for preparing a copper circuit-joined board comprising a laminate of two or more joining units joined to each other or one another, the joining units each comprising a ceramic substrate and a conductor layer, comprising copper as a main component, provided on the ceramic substrate through an interposing layer, said process comprising the steps of:

• (1) providing a ceramic substrate including the formation of a high-melting metallizing layer comprising a high-melting metal as a main component;
• (2) providing a conductor materials, the length and width in the planar direction of the conductor materials each in its portion to be directly joined to the interposing layer being at least 0.05 mm shorter than those in the planar direction of the interposing layer, the conductor materials each being in such a form that, after joining, the portion not to be joined directly to the interposing layer in the planar direction is not extended from the end of the interposing layer;
• (3) selecting the materials, for each lamination unit, as a conductor layer material, disposing a low-melting metal material to form a low-melting metallizing layer for the interposing layer between the substrate and the conductor layer material to prepare a joining unit, and then providing the joining units by repeatedly laminating the joining unit twice or more on top of each other or one another to prepare a joining assembly;
• (4) heating the assembly in the temperature range of the melting point of the component (s) of the interposing layer to below the melting point of the conductor layer material to form a joined body;
• and (5) finishing the joined body, wherein the interposing layer is constituted by the high-melting metallizing layer and the low-melting metallizing layer in that order from the substrate side, the low-melting metallizing layer having a melting point of 1,000° C. or below and comprising as a main component at least one member selected from the group consisting of nickel, iron and copper.