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US-12628646-B2 - Copper/ceramic assembly and insulating circuit substrate

US12628646B2US 12628646 B2US12628646 B2US 12628646B2US-12628646-B2

Abstract

This copper/ceramic assembly includes: a copper member consisting of copper or a copper alloy; and a ceramic member consisting of silicon nitride, wherein the copper member and the ceramic member are bonded. At a bonded interface between the ceramic member and the copper member, an active metal nitride layer is formed on a side of the ceramic member. In a region extending by 10 μm from the active metal nitride layer toward a side of the copper member, an area rate of an active metal compound containing Si and an active metal is 10% or less. A ratio P A /P B of an area rate P A of the active metal compound in a peripheral part region of the copper member to an area rate P B of the active metal compound in a central part region of the copper member is in a range of 0.7 or more and 1.4 or less.

Inventors

  • Nobuyuki Terasaki

Assignees

  • MITSUBISHI MATERIALS CORPORATION

Dates

Publication Date
20260512
Application Date
20220715
Priority Date
20210716

Claims (8)

  1. 1 . A copper/ceramic assembly obtained by bonding a copper member consisting of copper or a copper alloy and a ceramic member consisting of silicon nitride, wherein at a bonded interface between the ceramic member and the copper member, an active metal nitride layer is formed on a side of the ceramic member, in a region extending by 10 μm from the active metal nitride layer toward a side of the copper member, an area rate of an active metal compound containing Si and an active metal is 10% or less, and a ratio P A /P B of an area rate P A of the active metal compound in a peripheral part region of the copper member to an area rate P B of the active metal compound in a central part region of the copper member is in a range of 0.7 or more and 1.4 or less.
  2. 2 . The copper/ceramic assembly according to claim 1 , wherein a thickness t 1 A of the active metal nitride layer formed in the peripheral part region of the copper member and a thickness t 1 B of the active metal nitride layer formed in the central part region of the copper member are in a range of 0.05 μm or more and 0.8 μm or less, and a thickness ratio t 1 A /t 1 B is in a range of 0.7 or more and 1.4 or less.
  3. 3 . The copper/ceramic assembly according to claim 1 , wherein at the bonded interface between the ceramic member and the copper member, an Ag—Cu alloy layer is formed on the side of the copper member, and a thickness t 2 A of the Ag—Cu alloy layer formed in the peripheral part region of the copper member and a thickness t 2 B of the Ag—Cu alloy layer formed in the central part region of the copper member are in a range of 1 μm or more and 30 μm or less, and a thickness ratio t 2 A /t 2 B is in a range of 0.7 or more and 1.4 or less.
  4. 4 . The copper/ceramic assembly according to claim 2 , wherein at the bonded interface between the ceramic member and the copper member, an Ag—Cu alloy layer is formed on the side of the copper member, and a thickness t 2 A of the Ag—Cu alloy layer formed in the peripheral part region of the copper member and a thickness t 2 B of the Ag—Cu alloy layer formed in the central part region of the copper member are in a range of 1 μm or more and 30 μm or less, and a thickness ratio t 2 A /t 2 B is in a range of 0.7 or more and 1.4 or less.
  5. 5 . An insulating circuit substrate obtained by bonding a copper sheet consisting of copper or a copper alloy to a surface of a ceramic substrate consisting of silicon nitride, wherein at a bonded interface between the ceramic substrate and the copper sheet, an active metal nitride layer is formed on a side of the ceramic substrate, in a region extending by 10 μm from the active metal nitride layer toward a side of the copper sheet, an area rate of an active metal compound containing Si and an active metal is 10% or less, and a ratio P A /P B of an area rate P A of the active metal compound in a peripheral part region of the copper sheet to an area rate P B of the active metal compound in a central part region of the copper sheet is in a range of 0.7 or more and 1.4 or less.
  6. 6 . The insulating circuit substrate according to claim 5 , wherein a thickness t 1 A of the active metal nitride layer formed in the peripheral part region of the copper sheet and a thickness t 1 B of the active metal nitride layer formed in the central part region of the copper sheet are in a range of 0.05 μm or more and 0.8 μm or less, and a thickness ratio t 1 A /t 1 B is in a range of 0.7 or more and 1.4 or less.
  7. 7 . The insulating circuit substrate according to claim 5 , wherein at the bonded interface between the ceramic substrate and the copper sheet, an Ag—Cu alloy layer is formed on the side of the copper sheet, and a thickness t 2 A of the Ag—Cu alloy layer formed in the peripheral part region of the copper sheet and a thickness t 2 B of the Ag—Cu alloy layer formed in the central part region of the copper sheet are in a range of 1 μm or more and 30 μm or less, and a thickness ratio t 2 A /t 2 B is in a range of 0.7 or more and 1.4 or less.
  8. 8 . The insulating circuit substrate according to claim 6 , wherein at the bonded interface between the ceramic substrate and the copper sheet, an Ag—Cu alloy layer is formed on the side of the copper sheet, and a thickness t 2 A of the Ag—Cu alloy layer formed in the peripheral part region of the copper sheet and a thickness t 2 B of the Ag—Cu alloy layer formed in the central part region of the copper sheet are in a range of 1 μm or more and 30 μm or less, and a thickness ratio t 2 A /t 2 B is in a range of 0.7 or more and 1.4 or less.

Description

TECHNICAL FIELD The present invention relates to: a copper/ceramic assembly obtained by bonding a copper member consisting of copper or a copper alloy to a ceramic member; and an insulating circuit substrate obtained by bonding a copper sheet consisting of copper or a copper alloy to a surface of a ceramic substrate. The present application claims priority on Japanese Patent Application No. 2021-117950 filed on Jul. 16, 2021, the content of which is incorporated herein by reference. BACKGROUND ART A power module, an LED module, and a thermoelectric module have a structure in which a power semiconductor element, an LED element, and a thermoelectric element are bonded to an insulating circuit substrate, and in the insulating circuit substrate, a circuit layer consisting of a conductive material is formed on one surface of an insulating layer. For example, a power semiconductor element for high power control, which is used for controlling a wind power generation, an electric vehicle, a hybrid vehicle, or the like, generates a large amount of heat during operation, and thus, an insulating circuit substrate has been widely used in the related art as a substrate on which the power semiconductor element is mounted, and the insulating circuit substrate includes: a ceramic substrate; a circuit layer formed by bonding a metal sheet having excellent electrical conductivity to one surface of the ceramic substrate; and a metal layer for heat radiation, which is formed by bonding a metal sheet to the other surface of the ceramic substrate. For example, Patent Document 1 proposes an insulating circuit substrate in which a circuit layer and a metal layer are formed by bonding a copper sheet to each of one surface and the other surface of a ceramic substrate. In Patent Document 1, the copper sheet is disposed on each of the one surface and the other surface of the ceramic substrate with an Ag—Cu—Ti-based brazing material being interposed, and then a heating treatment is carried out to bond the copper sheet (so-called active metal brazing method). In addition, Patent Document 2 proposes a power module substrate in which a copper sheet consisting of copper or a copper alloy is bonded to a ceramic substrate consisting of silicon nitride by using a bonding material containing Ag and Ti. As described above, in a case of bonding a copper sheet to a ceramic substrate using a bonding material containing Ti, Ti which is an active metal reacts with the ceramic substrate; and thereby, the wettability of the bonding material is improved, and the bonding strength between the copper sheet and the ceramic substrate is improved. By the way, in recent years, there is a tendency that a heat generation temperature of a semiconductor element mounted on an insulating circuit substrate increases, and an insulating circuit substrate is required to have a thermal cycle reliability that can withstand a thermal cycle more severe than a thermal cycle in the related art. In a case of bonding a copper sheet to a ceramic substrate using a bonding material containing Ti, as described above, there is a risk that Ti which is an active metal diffuses to the copper sheet side, and an intermetallic compound containing Cu and Ti is precipitated; and thereby, a portion in a vicinity of the bonded interface becomes hard, breaking occurs in the ceramic member during loading of a thermal cycle, and the thermal cycle reliability deteriorates. CITATION LIST Patent Documents Patent Document 1 Japanese Patent No. 3211856 Patent Document 2 Japanese Unexamined Patent Application, First Publication No. 2018-008869 SUMMARY OF INVENTION Technical Problem The present invention has been made in consideration of the above-described circumstances, and an objective of the present invention is to provide a copper/ceramic assembly having an excellent thermal cycle reliability, which can suppress the occurrence of breaking in a ceramic member even in a case where a severe thermal cycle is loaded, and an insulating circuit substrate consisting of the copper/ceramic assembly. Solution to Problem As a result of diligent studies by the inventors of the present invention in order to solve the above-described problems, it was found that in a case where a ceramic member and a copper member are bonded using a bonding material containing an active metal, a liquid phase generated during the bonding is excluded from the central part of the copper member to the peripheral part, and a relatively large amount of the active metal is present in the peripheral part of the copper member; and thereby, the peripheral part region of the copper member tends to be hard as compared with the central part region at a bonded interface between the ceramic member and the copper member. In addition, the inventors of the present invention obtained a knowledge that during loading of a thermal cycle, stress concentrates on the hard peripheral part region of the copper member at the bonded interface, and thus the