Copper / ceramic joint body, and insulated circuit board

Abstract

To provide a copper / ceramic joint body exhibiting excellent jointing between a ceramic member and a copper member and excellent heat cycle reliability even when subjected to a severe heat cycle.SOLUTION: The copper / ceramic joint body formed by jointing a copper member made from copper or a copper alloy and a ceramic member, is characterized in that an active metal compound layer including one species or two or more species of active metal compounds selected from Ti, Zr, Nb and Hf, or a magnesium oxide layer is formed in the copper member side region of the ceramic member, a Mg solution layer is formed in the ceramic member side region of the copper member, and a transition metal layer including one species or two or more species of transition metal selected from V, Cr, Mn, Fe, Co, Ni, Mo, Ta, and W is formed between the Mg solution layer and the active metal compound layer or the magnesium oxide layer.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a copper / ceramic bonded body formed by bonding a copper member made of copper or a copper alloy to a ceramic member, and to an insulating circuit board formed by bonding a copper plate made of copper or a copper alloy to a surface of a ceramic substrate. [Background technology]

[0002] In power modules, LED modules and thermoelectric modules, power semiconductor elements, LED elements and thermoelectric elements are bonded to an insulating circuit board having an insulating layer on one side of which a circuit layer made of a conductive material is formed. For example, power semiconductor elements for controlling large amounts of power used to control wind power generation, electric vehicles, hybrid vehicles, and the like generate a large amount of heat during operation. Therefore, as a substrate for mounting these elements, an insulated circuit board has been widely used which includes a ceramic substrate, a circuit layer formed by bonding a metal plate with excellent electrical conductivity to one surface of the ceramic substrate, and a metal layer for heat dissipation formed by bonding a metal plate to the other surface of the ceramic substrate.

[0003] For example, Patent Document 1 proposes an insulating circuit board in which a circuit layer and a metal layer are formed by bonding copper plates to one side and the other side of a ceramic substrate. In Patent Document 1, copper plates are arranged on one side and the other side of a ceramic substrate with an Ag-Cu-Ti brazing material interposed therebetween, and the copper plates are bonded by heat treatment (so-called active metal brazing method). In this active metal brazing method, a brazing material containing Ti, which is an active metal, is used, so that the wettability between the molten brazing material and the ceramic substrate is improved, and the ceramic substrate and the copper substrate are bonded well. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 3211856 Summary of the Invention [Problem to be solved by the invention]

[0005] Recently, the temperature of heat generated by semiconductor elements mounted on insulating circuit boards has been increasing. Furthermore, semiconductor devices having semiconductor elements mounted on insulating circuit boards are used as high-temperature operating devices capable of high-speed switching. Therefore, the insulating circuit board is subjected to thermal stress under high temperature conditions in a short period of time, and is required to have higher thermal cycle reliability than ever before.

[0006] The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a copper / ceramic bonded body which has excellent bonding strength between a ceramic member and a copper member and excellent thermal cycle reliability even when subjected to severe thermal cycles, and an insulated circuit board made of this copper / ceramic bonded body. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, a copper / ceramic joined body according to a first aspect of the present invention is a copper / ceramic joined body obtained by joining a copper member made of copper or a copper alloy to a ceramic member, wherein an active metal compound layer containing one or more active metal compounds selected from Ti, Zr, Nb and Hf or a magnesium oxide layer is formed in a region of the ceramic member facing the copper member, an Mg solid solution layer is formed in a region of the copper member facing the ceramic member, and a transition metal layer containing one or more transition metals selected from V, Cr, Mn, Fe, Co, Ni, Mo, Ta and W is formed between the Mg solid solution layer and the active metal compound layer or the magnesium oxide layer.

[0008] In the copper / ceramic joined body of aspect 1 of the present invention, an active metal compound layer or a magnesium oxide layer is formed in a region of the ceramic member facing the copper member, an Mg solid solution layer is formed in a region of the copper member facing the ceramic member, and the transition metal layer is formed between the Mg solid solution layer and the active metal compound layer or the magnesium oxide layer. Here, the active metal compound layer or magnesium oxide layer, the Mg solid-solution layer, and the transition metal layer are highly compatible, and the transition metal layer is more compatible with copper than the active metal compound layer or magnesium oxide layer, so that an Mg solid-solution layer is formed in the region of the copper component facing the ceramic component, and the presence of the transition metal layer between the Mg solid-solution layer and the active metal compound layer or the magnesium oxide layer greatly improves the bonding reliability between the ceramic component and the copper component. Therefore, in the copper / ceramic joined body of aspect 1 of the present invention, even when a thermal cycle under high temperature conditions is applied in a short period, the ceramic member and the copper member do not peel off, and the copper / ceramic joined body has particularly excellent thermal cycle reliability.

[0009] A copper / ceramic bonded body according to a second aspect of the present invention is characterized in that in the copper / ceramic bonded body according to the first aspect, the active metal compound layer has a structure in which a plurality of active metal compound particles are aggregated.

[0010] A copper / ceramic joined body according to a third aspect of the present invention is characterized in that in the copper / ceramic joined body according to the second aspect, a copper grain boundary phase is present between the active metal compound particles.

[0011] A copper / ceramic joined body according to a fourth aspect of the present invention is characterized in that in the copper / ceramic joined body according to the first aspect, the magnesium oxide layer has a structure in which a plurality of magnesium oxide particles are aggregated.

[0012] A copper / ceramic joined body according to a fifth aspect of the present invention is characterized in that in the copper / ceramic joined body according to the fourth aspect, a copper grain boundary phase is present between the magnesium oxide particles.

[0013] The insulating circuit board of the sixth aspect of the present invention is an insulating circuit board obtained by bonding a copper plate made of copper or a copper alloy to the surface of a ceramic substrate, and characterized in that an active metal compound layer containing one or more active metal compounds selected from Ti, Zr, Nb and Hf, or a magnesium oxide layer, is formed in a region of the ceramic substrate facing the copper plate, an Mg solid solution layer is formed in a region of the copper plate facing the ceramic substrate, and a transition metal layer containing one or more transition metals selected from V, Cr, Mn, Fe, Co, Ni, Mo, Ta and W is formed between the Mg solid solution layer and the active metal compound layer or the magnesium oxide layer.

[0014] In the insulating circuit board of aspect 6 of the present invention, an active metal compound layer or a magnesium oxide layer is formed in the region of the ceramic substrate facing the copper plate, and an Mg solid solution layer is formed in the region of the copper plate facing the ceramic substrate, and between the Mg solid solution layer and the active metal compound layer or the magnesium oxide layer, the bonding reliability between the ceramic substrate and the copper plate is greatly improved. Therefore, in the insulating circuit board of aspect 6 of the present invention, even when subjected to a thermal cycle under high temperature conditions in a short period, the ceramic substrate and the copper plate do not peel off, and the insulating circuit board has particularly excellent thermal cycle reliability.

[0015] An insulating circuit board according to a seventh aspect of the present invention is the insulating circuit board according to the sixth aspect, characterized in that the active metal compound layer has a structure in which a plurality of active metal compound particles are aggregated.

[0016] An insulating circuit board according to an eighth aspect of the present invention is the insulating circuit board according to the seventh aspect, characterized in that a copper grain boundary phase is present between the active metal compound particles.

[0017] An insulating circuit board according to a ninth aspect of the present invention is the insulating circuit board according to the sixth aspect, characterized in that the magnesium oxide layer has a structure in which a plurality of magnesium oxide particles are aggregated.

[0018] An insulating circuit board according to a tenth aspect of the present invention is the insulating circuit board according to the ninth aspect, characterized in that a copper grain boundary phase is present between the magnesium oxide particles. Effect of the Invention

[0019] According to the present invention, it is possible to provide a copper / ceramic bonded body which has excellent bonding strength between a ceramic member and a copper member and excellent thermal cycle reliability even when subjected to severe thermal cycles, and an insulated circuit board made of this copper / ceramic bonded body. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 is a schematic explanatory diagram of a power module using an insulating circuit board according to an embodiment of the present invention. [Diagram 2] 2 is an enlarged explanatory view of a bonding interface between a circuit layer and a metal layer of the insulating circuit board according to the first embodiment of the present invention and a ceramic substrate. FIG. [Diagram 3] FIG. 2 is a flow diagram of a method for producing an insulating circuit board according to a first embodiment of the present invention. [Figure 4] 1A to 1C are schematic explanatory diagrams of a method for producing an insulating circuit board according to a first embodiment of the present invention. [Diagram 5] FIG. 4 is a schematic explanatory diagram of an insulating circuit board according to a second embodiment of the present invention. [Figure 6] 5 is an enlarged explanatory view of a bonding interface between a circuit layer and a metal layer of an insulating circuit board according to a second embodiment of the present invention and a ceramic substrate. FIG. [Figure 7] FIG. 2 is an explanatory diagram of a surface cutting test in the examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0022] First Embodiment The copper / ceramic bonded body according to the first embodiment of the present invention is an insulating circuit board 10 formed by bonding a ceramic substrate 11 as a ceramic member made of ceramics to a copper plate 22 (circuit layer 12) and a copper plate 23 (metal layer 13) as copper members made of copper or a copper alloy. Fig. 1 shows a power module 1 including the insulating circuit board 10 of this embodiment.

[0023] This power module 1 includes an insulating circuit board 10 having a circuit layer 12 and a metal layer 13 arranged thereon, a semiconductor element 3 bonded to one surface of the circuit layer 12 (the upper surface in FIG. 1) via a bonding layer 2, and a heat sink 5 arranged on the other side of the metal layer 13 (the lower side in FIG. 1).

[0024] The semiconductor element 3 is made of a semiconductor material such as Si. The semiconductor element 3 and the circuit layer 12 are bonded to each other via a bonding layer 2. The bonding layer 2 is made of, for example, a Sn--Ag based, Sn--In based, or Sn--Ag--Cu based solder material.

[0025] The heat sink 5 is for dissipating heat from the insulating circuit board 10. The heat sink 5 is made of copper or a copper alloy, and in this embodiment, is made of phosphorus deoxidized copper. The heat sink 5 is provided with a flow path for a cooling fluid to flow. In this embodiment, the heat sink 5 and the metal layer 13 are joined by a solder layer 7 made of a solder material. The solder layer 7 is made of, for example, a Sn-Ag based, Sn-In based, or Sn-Ag-Cu based solder material.

[0026] As shown in FIG. 1, the insulating circuit board 10 of this embodiment includes a ceramic substrate 11, a circuit layer 12 disposed on one surface (the upper surface in FIG. 1) of the ceramic substrate 11, and a metal layer 13 disposed on the other surface (the lower surface in FIG. 1) of the ceramic substrate 11.

[0027] The ceramic substrate 11 is made of ceramics such as silicon nitride (Si3N4) and aluminum nitride (AlN) that have excellent insulating and heat dissipating properties. In this embodiment, the ceramic substrate 11 is made of aluminum nitride (AlN) that has particularly excellent heat dissipating properties. The thickness of the ceramic substrate 11 is set within a range of 0.2 mm to 1.5 mm, for example, and is set to 0.635 mm in this embodiment.

[0028] As shown in FIG. 4, the circuit layer 12 is formed by bonding a copper plate 22 made of copper or a copper alloy to one surface (the upper surface in FIG. 4) of a ceramic substrate 11. In this embodiment, the circuit layer 12 is formed by bonding a rolled sheet of oxygen-free copper to the ceramic substrate 11. The thickness of the copper plate 22 that becomes the circuit layer 12 is set within a range of 0.1 mm to 2.0 mm, and is set to 0.25 mm in this embodiment.

[0029] As shown in FIG. 4, the metal layer 13 is formed by joining a copper plate 23 made of copper or a copper alloy to the other surface (the lower surface in FIG. 4) of the ceramic substrate 11. In this embodiment, the metal layer 13 is formed by bonding a rolled sheet of oxygen-free copper to the ceramic substrate 11. The thickness of the copper plate 23 that becomes the metal layer 13 is set within a range of 0.1 mm to 2.0 mm, and is set to 0.25 mm in this embodiment.

[0030] FIG. 2 shows an enlarged view of the vicinity of the bonding interface between the ceramic substrate 11 and the circuit layer 12 (metal layer 13). An active metal compound layer 31 containing a compound of one or more active metals selected from Ti, Zr, Nb, and Hf is formed in a region of the ceramic substrate 11 on the circuit layer 12 (metal layer 13) side.

[0031] The active metal compound layer 31 is formed when an active metal (Ti, Zr, Nb, Hf) used in joining the ceramic substrate 11 and the copper plate 22 (copper plate 23) diffuses into the ceramic substrate 11 and reacts with the constituent elements of the ceramic substrate 11, and becomes part of the ceramic substrate 11. More specifically, when the ceramic substrate is made of silicon nitride (Si3N4) or aluminum nitride (AlN), the active metal compound layer 31 is a layer made of a nitride of these active metals. As shown in FIG. 2, the active metal compound layer 31 has a structure in which a plurality of active metal compound particles 32 are aggregated, and a copper grain boundary phase 33 is present between these active metal compound particles 32.

[0032] In this embodiment, Ti is used as the active metal used in bonding, and since the ceramic substrate 11 is made of silicon nitride (Si3N4), the active metal compound layer 31 is mainly made of titanium nitride (TiN). In this embodiment, the active metal compound layer 31 is formed by aggregating a plurality of titanium nitride particles (active metal compound particles 32) having an average particle size of 10 nm or more and 100 nm or less.

[0033] A transition metal layer 34 containing one or more transition metals selected from V, Cr, Mn, Fe, Co, Ni, Mo, Ta, and W is formed at the interface of the active metal compound layer 31 on the circuit layer 12 (metal layer 13) side. The transition metal layer 34 may be formed not only at the interface of the active metal compound layer 31 on the circuit layer 12 (metal layer 13) side, but also at the interface between the active metal compound particles 32 and the copper grain boundary phase 33. In other words, the transition metal layer 34 may be formed on the outer circumferential surface of the active metal compound particles 32 constituting the active metal compound layer 31.

[0034] In this embodiment, an Mg solid solution layer 36 is formed in the region of the circuit layer 12 (metal layer 13) on the ceramic substrate 11 side. This Mg solid solution layer 36 is formed by diffusing Mg contained in the bonding material used to bond the ceramic substrate 11 and the copper plate 22 (copper plate 23) toward the copper plate 22 (copper plate 23), and becomes part of the circuit layer 12 (metal layer 13).

[0035] Here, in the Mg solid solution layer 36, the Mg concentration is within the range of 0.05 atomic % to 6.9 atomic % with the total of Cu, Mg, active metals, and transition metals being 100 atomic %. The Mg solid solution layer 36 may contain an intermetallic compound (eg, Cu2Mg, CuMg2, etc.) with a Mg concentration in the range of 30 atomic % to 70 atomic %.

[0036] In this embodiment, the thickness of the active metal compound layer 31 is preferably within the range of 0.05 μm to 1.2 μm. In this embodiment, the thickness of the Mg solid solution layer 36 is preferably within a range of more than 0 μm and not more than 200 μm, and more preferably 50 μm or more and 120 μm or less. Furthermore, in this embodiment, the thickness of the transition metal layer 34 is preferably within the range of 1 nm to 15 nm.

[0037] A method for manufacturing the insulating circuit board 10 according to this embodiment will be described below with reference to FIGS.

[0038] (Joint material placement process S01) First, a ceramic substrate 11 is prepared, and as shown in FIG. 4, bonding materials 25 such as Mg, Cu, active metals (Ti, Zr, Nb, Hf), and transition metals (V, Cr, Mn, Fe, Co, Ni, Mo, Ta, W) are arranged between the copper plate 22 that will become the circuit layer 12 and the ceramic substrate 11, and between the copper plate 23 that will become the metal layer 13 and the ceramic substrate 11.

[0039] In the bonding material providing step S01, the amounts of Mg, Cu, active metal, and transition metal are preferably set as follows: If the ceramic substrate 11 and the copper plate 22 (copper plate 23) can be bonded, Cu does not need to be provided. Mg: 14.3 μmol / cm 2 More than 71.5μmol / cm 2 below Cu: 0 μmol / cm 2 More than 70.5μmol / cm 2 below Active metal: 0.8μmol / cm 2 More than 18.8μmol / cm 2 below Transition metal: 1.0μmol / cm 2 More than 15.0μmol / cm 2 below

[0040] (Lamination process S02) Next, the copper plate 22 and the ceramic substrate 11 are laminated with a bonding material 25 (Mg, Cu, active metal, transition metal) interposed therebetween, and the ceramic substrate 11 and the copper plate 23 are laminated with a bonding material 25 (Mg, Cu, active metal, transition metal) interposed therebetween.

[0041] (Joining process S03) Next, the stacked copper plate 22, bonding material 25 (Mg, Cu, active metal, transition metal), ceramic substrate 11, bonding material 25 (Mg, Cu, active metal, transition metal), and copper plate 23 are pressed in the stacking direction and placed in a vacuum furnace for heating to bond the copper plate 22, ceramic substrate 11, and copper plate 23 together. At this time, each element of the bonding material 25 diffuses to the copper plates 22, 23 side or the ceramic substrate 11 side, and an Mg solid solution layer 36 and an active metal compound layer 31 are formed, so that no bonding layer exists between the ceramic substrate 11 and the circuit layer 12 (metal layer 13).

[0042] Here, the heating temperature in the bonding process S03 is preferably within a range of 750°C or more and 950°C or less, and the sum of the temperature integral values ​​in the heating process from 740°C to the heating temperature and the holding process at the heating temperature is preferably within a range of 30°C·h or more and 500°C·h or less. The pressure load P in the joining step S03 is preferably set within a range of 0.098 MPa to 1.47 MPa.

[0043] As described above, the insulating circuit board 10 of this embodiment is manufactured by the bonding material providing step S01, the laminating step S02, and the bonding step S03.

[0044] (Heat sink bonding process S04) Next, heat sink 5 is bonded to the other surface side of metal layer 13 of insulating circuit board 10. Insulated circuit board 10 and heat sink 5 are laminated with a solder material interposed therebetween and loaded into a heating furnace, where insulating circuit board 10 and heat sink 5 are solder-joined via solder layer 7 .

[0045] (Semiconductor element bonding process S05) Next, the semiconductor element 3 is joined to one surface of the circuit layer 12 of the insulating circuit board 10 by soldering. Through the above-described steps, the power module 1 shown in FIG. 1 is manufactured.

[0046] According to the insulating circuit board 10 (copper / ceramic bonded body) of this embodiment configured as described above, an active metal compound layer 31 is formed in the region of the ceramic substrate 11 on the circuit layer 12 (metal layer 13) side, and a transition metal layer 34 is formed in the active metal compound layer 31 at the interface with the circuit layer 12 (metal layer 13), thereby significantly improving the bonding reliability between the ceramic substrate 11 and the circuit layer 12 (metal layer 13).

[0047] In addition, in the insulating circuit board 10 of this embodiment, an Mg solid solution layer 36 is formed in the region of the circuit layer 12 (metal layer 13) on the ceramic substrate 11 side, and when a transition metal layer 34 is formed between the Mg solid solution layer 36 and the active metal compound layer 31, the bonding reliability between the ceramic substrate 11 and the circuit layer 12 (metal layer 13) is significantly improved.

[0048] Second Embodiment The copper / ceramic bonded body according to the second embodiment of the present invention is an insulating circuit board 110 formed by bonding a ceramic substrate 111 as a ceramic member made of ceramic to a copper plate (circuit layer 112) and a copper plate (metal layer 113) as copper members made of copper or a copper alloy.

[0049] In this embodiment, the ceramic substrate 111 is made of aluminum oxide (Al2O3) which has excellent insulating properties and heat dissipation properties. The thickness of the ceramic substrate 111 is set, for example, within the range of 0.2 mm to 1.5 mm, and is set to 0.635 mm in this embodiment.

[0050] The circuit layer 112 is formed by bonding a copper plate made of copper or a copper alloy to one surface of the ceramic substrate 111 . In this embodiment, the circuit layer 112 is formed by bonding a rolled sheet of oxygen-free copper to the ceramic substrate 111 . The thickness of the copper plate that becomes the circuit layer 112 is set within the range of 0.1 mm to 2.0 mm, and in this embodiment, it is set to 0.25 mm.

[0051] The metal layer 113 is formed by bonding a copper plate made of copper or a copper alloy to the other surface of the ceramic substrate 111 . In this embodiment, the metal layer 113 is formed by bonding a rolled sheet of oxygen-free copper to the ceramic substrate 111 . The thickness of the copper plate that becomes the metal layer 113 is set within a range of 0.1 mm to 2.0 mm, and is set to 0.25 mm in this embodiment.

[0052] FIG. 6 shows an enlarged view of the vicinity of the bonding interface between the ceramic substrate 111 and the circuit layer 112 (metal layer 113). A magnesium oxide layer 131 is formed on the ceramic substrate 111 in a region on the circuit layer 112 (metal layer 13) side.

[0053] The magnesium oxide layer 131 is formed when Mg used to bond the ceramic substrate 111 and the copper plate diffuses into the ceramic substrate 111 and reacts with oxygen in the ceramic substrate 111, and becomes a part of the ceramic substrate 111. As shown in FIG. 7, the magnesium oxide layer 131 has a structure in which magnesium oxide particles 132 are aggregated, and copper grain boundary phases 133 are present between these magnesium oxide particles 132. In this embodiment, the magnesium oxide particles 132 constituting the magnesium oxide layer 131 preferably have an average particle size in the range of 10 nm to 100 nm. The magnesium oxide particles 132 are made of, for example, MgO or MgAl2O4.

[0054] Furthermore, a transition metal layer 134 containing one or more transition metals selected from V, Cr, Mn, Fe, Co, Ni, Mo, Ta, and W is formed at the interface of the magnesium oxide layer 131 on the circuit layer 12 (metal layer 13) side. The transition metal layer 134 may be formed not only at the interface of the magnesium oxide layer 131 on the circuit layer 112 (metal layer 113) side, but also at the interface between the magnesium oxide particles 132 and the copper grain boundary phase 133. In other words, the transition metal layer 134 may be formed on the outer circumferential surface of the magnesium oxide particles 132 constituting the magnesium oxide layer 131.

[0055] In this embodiment, an Mg solid solution layer 136 is formed in a region of the circuit layer 112 (metal layer 113) on the ceramic substrate 111 side. This Mg solid solution layer 136 is formed when Mg contained in the bonding material used to bond the ceramic substrate 111 and the copper plate diffuses into the copper plate, and becomes part of the circuit layer 112 (metal layer 113).

[0056] Here, in the Mg solid solution layer 136, the Mg concentration is within the range of 0.05 atomic % to 6.9 atomic % with the total of Cu, Mg, active metals, and transition metals being 100 atomic %. The Mg solid solution layer 136 may contain an intermetallic compound (eg, Cu2Mg, CuMg2, etc.) with a Mg concentration in the range of 30 atomic % to 70 atomic %.

[0057] In this embodiment, the thickness of the magnesium oxide layer 131 is preferably within the range of 0.05 μm to 1.2 μm. In this embodiment, the thickness of the Mg solid solution layer 136 is preferably within a range of more than 0 μm and not more than 200 μm, and more preferably 50 μm or more and 120 μm or less. Furthermore, in this embodiment, the thickness of the transition metal layer 134 is preferably within the range of 1 nm to 15 nm.

[0058] As in the first embodiment, the insulating circuit board 110 of the second embodiment is manufactured by the manufacturing method shown in FIGS. 3 and 4, i.e., the bonding material providing step S01, the laminating step S02, and the bonding step S03.

[0059] According to the insulating circuit board 110 (copper / ceramic bonded body) of this embodiment configured as described above, a magnesium oxide layer 131 is formed in the region of the ceramic substrate 111 on the circuit layer 112 (metal layer 113) side, and a transition metal layer 134 is formed in the magnesium oxide layer 131 at the interface with the circuit layer 112 (metal layer 113), thereby significantly improving the bonding reliability between the ceramic substrate 111 and the circuit layer 112 (metal layer 113).

[0060] In addition, in the insulating circuit board 110 of this embodiment, an Mg solid solution layer 136 is formed in the region of the circuit layer 112 (metal layer 113) on the ceramic substrate 111 side, and when a transition metal layer 134 is formed between the Mg solid solution layer 136 and the magnesium oxide layer 131, the bonding reliability between the ceramic substrate 111 and the circuit layer 112 (metal layer 113) is significantly improved.

[0061] Although the embodiment of the present invention has been described above, the present invention is not limited to this, and can be modified as appropriate without departing from the technical concept of the invention. For example, in the present embodiment, a power module is configured by mounting a semiconductor element on an insulating circuit board, but the present invention is not limited to this. For example, an LED module may be configured by mounting an LED element on a circuit layer of an insulating circuit board, or a thermoelectric module may be configured by mounting a thermoelectric element on a circuit layer of an insulating circuit board.

[0062] In addition, in the insulating circuit board of this embodiment, the ceramic substrate is described as being made of aluminum nitride (AlN) or alumina (Al2O3), but the present invention is not limited to this and other ceramic substrates such as silicon nitride (Si3N4) may also be used.

[0063] Furthermore, in this embodiment, the circuit layer is described as being formed by bonding a rolled sheet of oxygen-free copper to a ceramic substrate, but this is not limited to this, and the circuit layer may be formed by bonding copper pieces punched out of a copper plate to a ceramic substrate in a state in which the copper pieces are arranged in a circuit pattern. EXAMPLES

[0064] The results of experiments carried out to confirm the effects of the present invention will be described below.

[0065] First, we prepared ceramic substrates (40 mm×40 mm) shown in Tables 1 to 3. The thicknesses were 0.635 mm for AlN and Al2O3, and 0.32 mm for Si3N4. In addition, a copper plate made of oxygen-free copper and measuring 37 mm×37 mm with a thickness of 0.25 mm was prepared as the copper plate to be the circuit layer and the metal layer. Then, each element shown in Table 1 was disposed as a bonding material between the ceramic substrate and the copper plate to obtain a copper plate / ceramic substrate / copper plate laminate. Next, the copper plate and the ceramic substrate were bonded under the conditions shown in Tables 4 to 6 to obtain insulated circuit substrates (copper / ceramic bonded bodies) of Invention Examples 1 to 8, 11 to 14, and 21 to 24 and Comparative Examples 1, 11, and 21.

[0066] The bonding interface of the obtained insulating circuit board (copper / ceramic bonded body) was observed. The obtained insulating circuit board (copper / ceramic bonded body) was subjected to 500 thermal cycles in a liquid bath under the conditions of -40℃×5min←→150℃×5min. Then, the surface was machined.

[0067] (Observation of active metal compound layer) Observation samples were taken from the obtained insulating circuit board (copper / ceramic bonded body), and the cross section of the bonded interface between the copper plate and the ceramic substrate was observed using a scanning electron microscope (GeminiSEM 500 manufactured by Carl Zeiss AG) at an acceleration voltage of 7 kV and a magnification of 30,000 times in a range of 3 μm in height × 4 μm in width. A region in which active metal and nitrogen (N) coexist was present, and the total of the active metal and nitrogen (N) in that region was taken as 100 atomic %, and the region in which the concentration of the active metal was 20 atomic % or more was judged to be an active metal compound layer, and the area of ​​that region was measured. The active metal compound layer is a part of the ceramic member. The thickness of the active metal compound layer was calculated by dividing the measured area by the width of the measurement field of view. Measurements were performed in five fields of view, and the average values ​​are shown in Tables 4 to 6.

[0068] (Observation of magnesium oxide layer) Observation samples were taken from the obtained insulating circuit board (copper / ceramic bonded body), and the cross section of the bonded interface between the copper plate and the ceramic substrate was observed using a scanning electron microscope (GeminiSEM 500 manufactured by Carl Zeiss AG) at an acceleration voltage of 7 kV and a magnification of 30,000 times in a range of 3 μm in height × 4 μm in width. A region where magnesium (Mg) and oxygen (O) coexist was present, and the sum of magnesium (Mg) and oxygen (O) in that region was taken as 100 atomic %, and the region where the magnesium (Mg) concentration was 40 atomic % or more was judged to be a magnesium oxide layer, and the area of ​​that region was measured. The magnesium oxide layer is a part of the ceramic member. The thickness of the active metal compound layer was calculated by dividing the measured area by the width of the measurement field of view. Measurements were performed in five fields of view, and the average values ​​are shown in Tables 4 to 6.

[0069] (Observation of Mg solid solution layer) Observation samples were taken from the obtained insulating circuit board (copper / ceramic bonded body), and the cross section of the bonded interface between the copper plate and the ceramic substrate was analyzed by line analysis in a range of 200 μm long from the interface between the copper member and the active metal compound layer toward the copper member using an EPMA device (JXA-8530F manufactured by JEOL Ltd.) at an accelerating voltage of 15 kV. The total of active metals, transition metals, Mg, and Cu was taken as 100 atomic %, and the region with a Mg concentration of 0.05 atomic % or more and 6.9 atomic % or less was determined to be the Mg solid solution layer, and the measured length was taken as the thickness of the Mg solid solution layer. The Mg solid solution layer was a part of the copper member. Measurements were performed in five fields of view, and the average values ​​are shown in Tables 4 to 6.

[0070] (Observation of transition metal layer) Observation samples were taken from the obtained insulating circuit board (copper / ceramic bonded body), and the cross section of the bonded interface between the copper plate and the ceramic substrate was observed using a scanning transmission electron microscope (Titan G2 ChemiSTEM manufactured by Thermo Fisher Scientific) at an acceleration voltage of 200 kV and a magnification of 640,000 times, in a range of 50 nm in height x 20 nm in width. The total of Cu, Mg, ceramic constituent elements, active metals, and transition metals was taken as 100 atomic %, and the region with a transition metal concentration 1 atomic % or more higher than that in the active metal compound layer (particle) was determined to be the transition metal layer, and the area of ​​the region was measured. The thickness of the transition metal layer was calculated by dividing the measured area by the width of the measurement field of view. Measurements were performed in five fields of view, and the average values ​​are shown in Tables 4 to 6. Here, the ceramic constituent elements are Al, Si, N, and O.

[0071] (Surface cutting test) The obtained insulating circuit board (copper / ceramic bonded body) was subjected to 500 thermal cycles in a liquid bath under the conditions of -40℃×5 min←→150℃×5 min. A surface cutting test was performed on the insulated circuit board (copper / ceramic bonded body) that had been subjected to thermal cycling to evaluate the bonding strength between the copper plate and the ceramic substrate. In the surface cutting test, first, the copper plate was cut to a thickness of 30 μm. As shown in Figure 7, a cutting blade with a blade width of 0.3 mm was used to cut the copper plate at a horizontal cutting speed of 2 μm / sec and a vertical cutting speed of 0.1 μm / sec ((1) cutting stage). When the cutting blade reached the interface between the copper plate and the ceramic substrate, the blade was moved only in the horizontal direction ((2) peeling stage). The horizontal load was measured when the horizontal load became constant during the peeling stage. The strength of the bonding interface was calculated by dividing the measured load by the blade width. The evaluation results are shown in Tables 4 to 6.

[0072] [Table 1]

[0073] [Table 2]

[0074] [Table 3]

[0075] [Table 4]

[0076] [Table 5]

[0077] [Table 6]

[0078] Comparing Examples 1 to 8 of the present invention, in which the ceramic substrate is made of AlN, with Comparative Example 1, it is confirmed that in Examples 1 to 8 of the present invention, in which a transition metal layer is formed, the strength of the bonding interface is improved compared to Comparative Example 1, in which no transition metal layer is formed. Comparing Examples 11 to 18 of the present invention, in which the ceramic substrate is made of Si3N4, with Comparative Example 11, it is confirmed that in Examples 11 to 18 of the present invention, in which a transition metal layer is formed, the strength of the bonding interface is improved compared to Comparative Example 11, in which no transition metal layer is formed. Comparing Inventive Examples 21 to 24 and Comparative Example 21, in which the ceramic substrate is made of Al2O3, it is confirmed that in Inventive Examples 21 to 24 in which a transition metal layer is formed, the strength of the bonding interface is improved compared to Comparative Example 21 in which no transition metal layer is formed.

[0079] From the results of the above confirmatory experiments, it was confirmed that the present invention can provide an insulated circuit board (copper / ceramic bonded body) that has excellent bonding properties between the ceramic members and the copper members and has excellent thermal cycle reliability, even when subjected to severe thermal cycles. [Explanation of symbols]

[0080] 10,110 Insulated circuit board (copper / ceramic joint) 11,111 Ceramic substrate (ceramic component) 12,112 Circuit layer (copper material) 13,113 Metal layer (copper material) 31 Active metal compound layer 34,134 transition metal layer 36,136 Mg solid solution layer 131 Magnesium oxide layer

Claims

1. A copper / ceramic bonded body obtained by bonding a copper member made of copper or a copper alloy to a ceramic member, an active metal compound layer containing a compound of one or more active metals selected from Ti, Zr, Nb, and Hf, or a magnesium oxide layer is formed in a region of the ceramic member facing the copper member; a Mg solid solution layer is formed in a region of the copper member facing the ceramic member, a transition metal layer containing one or more transition metals selected from V, Cr, Mn, Fe, Co, Ni, Mo, Ta and W is formed between the Mg solid solution layer and the active metal compound layer or the magnesium oxide layer.

2. 2. The copper / ceramic bonded body according to claim 1, wherein the active metal compound layer has a structure in which a plurality of active metal compound particles are aggregated.

3. 3. The copper / ceramic bonded body according to claim 2, wherein a copper grain boundary phase is present between the active metal compound particles.

4. 2. The copper / ceramic bonded body according to claim 1, wherein the magnesium oxide layer has a structure in which a plurality of magnesium oxide particles are aggregated.

5. 5. The copper / ceramic bonded body according to claim 4, wherein a copper grain boundary phase is present between the magnesium oxide particles.

6. An insulating circuit board having a ceramic substrate and a copper plate made of copper or a copper alloy bonded to the surface thereof, an active metal compound layer containing a compound of one or more active metals selected from Ti, Zr, Nb, and Hf, or a magnesium oxide layer is formed in a region of the ceramic substrate facing the copper plate; a Mg solid solution layer is formed in a region of the copper plate facing the ceramic substrate, An insulating circuit board, characterized in that a transition metal layer containing one or more transition metals selected from V, Cr, Mn, Fe, Co, Ni, Mo, Ta and W is formed between the Mg solid solution layer and the active metal compound layer or the magnesium oxide layer.

7. 7. The insulating circuit board according to claim 6, wherein the active metal compound layer has a structure in which a plurality of active metal compound particles are aggregated.

8. 8. The insulating circuit board according to claim 7, wherein a copper grain boundary phase is present between the active metal compound particles.

9. 7. The insulating circuit board according to claim 6, wherein the magnesium oxide layer has a structure in which a plurality of magnesium oxide particles are aggregated.

10. 10. The insulating circuit board according to claim 9, wherein a copper grain boundary phase is present between the magnesium oxide particles.

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