Copper / Ceramics Bonded Body and Insulated Circuit Board

Abstract

To provide a copper / ceramic joint body that can prevent a ceramic member from cracking even when subjected to a severe thermal cycle, offering superior thermal cycle reliability.SOLUTION: A copper / ceramic joint body 10 is obtained by joining a copper member 12 composed of copper or a copper alloy and a ceramic member 11. At a joint interface between the ceramic member 11 and the copper member 12, a Mg solid-solution layer 31 is formed in which Mg is dissolved in a matrix phase of Cu. In a region up to 15 μm from a joint face of the ceramic member 11 to the copper member 12 side, a deposition area ratio of MgO particles 33 deposited in the Mg solid-solution layer 31 is 15% or less.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] This invention relates to a copper / ceramics joined body in which a copper member made of copper or a copper alloy and a ceramics member are joined, and an insulating circuit board in which a copper plate made of copper or a copper alloy is joined to the surface of a ceramics substrate.

Background Art

[0002] In power modules, LED modules, and thermoelectric modules, a structure is adopted in which a power semiconductor element, an LED element, and a thermoelectric element are joined to an insulating circuit board in which a circuit layer made of a conductive material is formed on one surface of an insulating layer. For example, a power semiconductor element for high-power control used to control wind power generation, electric vehicles, hybrid vehicles, etc. generates a large amount of heat during operation. Therefore, as a substrate on which this is mounted, a ceramics substrate, a circuit layer formed by joining a metal plate with excellent conductivity to one surface of this ceramics substrate, and a heat dissipation metal layer formed by joining a metal plate to the other surface of the ceramics substrate are provided. Insulating circuit boards have been widely used conventionally.

[0003] For example, Patent Document 1 proposes an insulating circuit board in which a circuit layer and a metal layer are formed by joining copper plates to one surface and the other surface of a ceramics substrate. In this Patent Document 1, copper plates are arranged with an Ag-Cu-Ti-based brazing material interposed between one surface and the other surface of the ceramics substrate, and the copper plates are joined by performing a heat treatment (so-called active metal brazing method). In this active metal brazing method, since a brazing material containing Ti, which is an active metal, is used, the wettability between the molten brazing material and the ceramics substrate is improved, and the ceramics substrate and the copper plate are satisfactorily joined.

[0004] Also, Patent Document 2 proposes an insulating circuit board in which a ceramics substrate and a copper plate are joined using a Cu-Mg-Ti-based brazing material. In this Patent Document 2, it is configured to be joined by heating at 560 to 800°C in a nitrogen gas atmosphere. Mg in the Cu-Mg-Ti alloy sublimes and does not remain at the joining interface, and titanium nitride (TiN) is not substantially formed.

[0005] Furthermore, Patent Document 3 discloses an insulating circuit board in which a copper plate and a ceramic substrate are joined using Mg. In this Patent Document 3, even when terminals or the like are ultrasonically joined, it is possible to suppress the occurrence of cracks at the joining interface between the copper plate and the ceramic substrate.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0007] By the way, recently, the heat generation temperature of semiconductor elements mounted on insulating circuit boards has tended to increase, and insulating circuit boards are required to have a higher thermal cycle reliability that can withstand severe thermal cycles than in the past. Here, as disclosed in Patent Documents 1 and 2, when a copper plate and a ceramic substrate are joined using a joining material containing Ti, which is an active metal, Ti, which is an active metal, diffuses to the copper plate side, and an intermetallic compound containing Cu and Ti precipitates, making the vicinity of the joining interface hard. When a thermal cycle load is applied, cracks may occur in the ceramic member, and the thermal cycle reliability may decrease.

[0008] Also, as disclosed in Patent Document 3, when a ceramic substrate and a copper plate are joined using Mg, a Mg solid solution layer in which Mg is solid dissolved in the Cu matrix is formed at the joining interface between the ceramic substrate and the copper plate. Therefore, the vicinity of the joining surface of the copper plate becomes hard due to the solid solution hardening of Mg. Furthermore, by the reaction of oxygen and Mg present at the joining interface, Mg oxide may precipitate in the Mg solid solution layer, and this precipitation hardening may further harden the joining interface. Thus, even when a ceramic substrate and a copper plate are joined using Mg without using the active metal Ti, the joining interface may become hard, and there is a possibility that the thermal cycle reliability cannot be sufficiently improved.

[0009] This invention has been made in view of the above-described circumstances, and an object thereof is to provide a copper / ceramic joined body excellent in thermal cycle reliability that can suppress the occurrence of cracks in a ceramic member even when a severe thermal cycle is applied, and an insulating circuit board including this copper / ceramic joined body.

Means for Solving the Problems

[0010] In order to solve the above-described problems, the copper / ceramic joined body of the present invention is a copper / ceramic joined body in which a copper member made of copper or a copper alloy and a ceramic member are joined, and a Mg solid solution layer in which Mg is solid dissolved in the Cu matrix is formed at the joining interface between the ceramic member and the copper member, and in a region from the joining surface of the ceramic member to the copper member side up to 15 μm, the area ratio of the MgO particles precipitated in the Mg solid solution layer is 15% or less. and the average value of the indentation hardness at a position 10 μm from the joint surface of the ceramic member toward the copper member side is within the range of 100 mgf / μm 2 or more and 180 mgf / μm 2 or less It is characterized by this.

[0011] According to the copper / ceramics joint of the present invention, on the joint interface between the ceramics member and the copper member, an Mg solid solution layer in which Mg is solid-solved in the Cu matrix phase is formed, and in the region up to 15 μm from the joint surface of the ceramics member toward the copper member side, the area ratio of MgO particles precipitated in the Mg solid solution layer is 15% or less. Therefore, it is possible to suppress the hardening of the joint interface due to precipitation hardening and suppress the occurrence of cracks in the ceramics member during thermal cycling loading. Therefore, a copper / ceramics joint with high joint strength and particularly excellent thermal cycle reliability can be obtained.

[0012] Also The average value of the indentation hardness at the position 10 μm from the joint surface of the ceramics member toward the copper member side is 100 mgf / μm 2 or more. Therefore, the copper near the joint interface is sufficiently melted to form a liquid phase, and the ceramics member and the copper member are firmly joined. On the other hand, the average value of the indentation hardness at the position 10 μm from the joint surface of the ceramics member toward the copper member side is 180 mgf / μm 2 or less. Therefore, the vicinity of the joint interface is not harder than necessary, and the occurrence of cracks during thermal cycling loading can be suppressed.

[0013] The indentation hardness H in the present invention is measured by measuring the load-displacement correlation when a test load of 5000 mgf is applied using a triangular pyramid diamond indenter called a Berkovich indenter with a flank angle of 114.8° or more and 115.1° or less, and is calculated from the following formula. hc = ht - 0.75 × P / S (ht: indentation depth, P: load, S: contact stiffness (= dP / dh|Pmax), hc: contact depth) Contact area A = 24.56 × hc 2 Indentation hardness H = P / A

[0014] The insulating circuit board of the present invention is an insulating circuit board in which a copper plate made of copper or a copper alloy is joined to the surface of a ceramic substrate, and a Mg solid solution layer in which Mg is solid-solved in the Cu matrix is formed at the joining interface between the ceramic substrate and the copper plate. In the region from the joining surface of the ceramic substrate to the copper plate side up to 15 μm, the area fraction of MgO particles precipitated in the Mg solid solution layer is 15% or less. and the average value of the indentation hardness at a position 10 μm from the joint surface of the ceramic substrate toward the copper plate side is within the range of 100 mgf / μm 2 or more and 180 mgf / μm 2 or less It is characterized by this.

[0015] According to the insulating circuit board of the present invention, a Mg solid solution layer in which Mg is solid-solved in the Cu matrix is formed at the joining interface between the ceramic substrate and the copper plate. In the region from the joining surface of the ceramic substrate to the copper plate side up to 15 μm, the area fraction of MgO particles precipitated in the Mg solid solution layer is set to 15% or less. Therefore, it is possible to suppress the hardening of the joining interface due to precipitation hardening, and it is possible to suppress the occurrence of cracks in the ceramic substrate during a thermal cycle load. Therefore, it is possible to obtain an insulating circuit board having high joining strength and particularly excellent thermal cycle reliability.

[0016] Also The average value of the indentation hardness at the position 10 μm from the joining surface of the ceramic substrate to the copper plate side is 100 mgf / μm 2 or more. Therefore, the copper near the joining interface is sufficiently melted to form a liquid phase, and the ceramic substrate and the copper plate are firmly joined. On the other hand, the average value of the indentation hardness at the position 10 μm from the joining surface of the ceramic substrate to the copper plate side is suppressed to 180 mgf / μm 2 or less. Therefore, the vicinity of the joining interface is not harder than necessary, and the occurrence of cracks during a thermal cycle load can be suppressed.

Effect of the Invention

[0017] According to the present invention, even when a severe thermal cycle is applied, it is possible to suppress the occurrence of cracks in the ceramic member, and to provide a copper / ceramic joint excellent in thermal cycle reliability and an insulating circuit board composed of this copper / ceramic joint.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0019] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The copper / ceramic joint according to this embodiment is an insulating circuit board 10 in which a ceramic substrate 11 as a ceramic member made of ceramics and 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 are joined. FIG. 1 shows a power module 1 including the insulating circuit board 10 according to this embodiment.

[0020] This power module 1 includes an insulating circuit board 10 in which a circuit layer 12 and a metal layer 13 are disposed, a semiconductor element 3 joined via a bonding layer 2 to one surface (the upper surface in FIG. 1) of the circuit layer 12, and a heat sink 5 disposed on the other side (the lower side in FIG. 1) of the metal layer 13.

[0021] The semiconductor element 3 is made of a semiconductor material such as Si. The semiconductor element 3 and the circuit layer 12 are joined via the joining layer 2. The joining layer 2 is made of, for example, a solder material of the Sn-Ag system, Sn-In system, or Sn-Ag-Cu system.

[0022] The heat sink 5 is for dissipating the heat from the aforementioned insulating circuit board 10. The heat sink 5 is made of copper or a copper alloy, and in this embodiment, it is made of phosphor-deoxidized copper. A flow path for a cooling fluid is provided in the heat sink 5. 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 solder material of the Sn-Ag system, Sn-In system, or Sn-Ag-Cu system.

[0023] And the insulating circuit board 10 of this embodiment includes, as shown in FIG. 1, 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.

[0024] The ceramic substrate 11 is made of ceramics such as silicon nitride (Si3N4), aluminum nitride (AlN), and alumina (Al2O3) that are excellent in insulation and heat dissipation. In this embodiment, the ceramic substrate 11 is made of aluminum nitride (AlN) with particularly excellent heat dissipation. Also, the thickness of the ceramic substrate 11 is set, for example, within the range of 0.2 mm or more and 1.5 mm or less, and in this embodiment, it is set to 0.635 mm.

[0025] As shown in FIG. 4, the circuit layer 12 is formed by joining a copper plate 22 made of copper or a copper alloy to one surface (the upper surface in FIG. 4) of the ceramic substrate 11. In this embodiment, the circuit layer 12 is formed by bonding a rolled plate of oxygen-free copper to the ceramic substrate 11. Note that the thickness of the copper plate 22 that becomes the circuit layer 12 is set within the range of 0.1 mm or more and 2.0 mm or less, and in this embodiment, it is set to 0.6 mm.

[0026] As shown in FIG. 4, the metal layer 13 is formed by bonding 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 plate of oxygen-free copper to the ceramic substrate 11. Note that the thickness of the copper plate 23 that becomes the metal layer 13 is set within the range of 0.1 mm or more and 2.0 mm or less, and in this embodiment, it is set to 0.6 mm.

[0027] Here, at the bonding interface between the ceramic substrate 11 and the circuit layer 12 (metal layer 13), as shown in FIG. 2, an Mg solid solution layer 31 in which Mg is solid-solved in the Cu matrix phase is formed. The Mg solid solution layer 31 is a region where, using an EPMA apparatus (JXA-8539F manufactured by JEOL Ltd.), the region (vertical 400 μm × horizontal 600 μm) including the bonding interface is observed at a magnification of 200 times and an acceleration voltage of 15 kV at the bonding interface between the circuit layer 12 (metal layer 13) and the ceramic substrate 11, and the Mg concentration is 0.01 atomic % or more and 6.9 atomic % or less with Cu concentration + Mg concentration = 100 atomic %.

[0028] And in the insulating circuit board 10 of this embodiment, as shown in FIG. 2, MgO particles 33 are precipitated inside the Mg solid solution layer 31, and in the region E from the bonding surface of the ceramic substrate 11 to the circuit layer 12 (metal layer 13) side up to 15 μm, the area ratio of the precipitated surface of the MgO particles 33 precipitated in the Mg solid solution layer 31 is 15% or less. The area ratio of the precipitated surface of the MgO particles 33 may be 0%. Note that although a thin MgO layer may be formed on the surface of the ceramic substrate 11, since this MgO layer is not precipitated on the Mg solid solution layer 31, it is not included in the above-described deposition area ratio of the MgO particles 33.

[0029] Also, in the present embodiment, as shown in FIG. 2, the average value of the indentation hardness at the position X 10 μm from the bonding surface of the ceramic substrate 11 toward the circuit layer 12 (metal layer 13) side is 100 mgf / μm 2 or more and 180 mgf / μm 2 It is preferably within the following range.

[0030] Hereinafter, a method for manufacturing the insulating circuit board 10 according to the present embodiment will be described with reference to FIGS. 3 and 4.

[0031] (Mg Arrangement Step S01) First, a ceramic substrate 11 is prepared, and as shown in FIG. 4, Mg is 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, respectively. In the present embodiment, Mg foils 25 are disposed 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. Here, in the Mg arrangement step S01, the amount of Mg to be arranged is 0.34 mg / cm 2 or more and 4.35 mg / cm 2 or less. Note that the amount of Mg to be arranged is preferably 0.52 mg / cm 2 or more, and more preferably 0.69 mg / cm 2 or more. On the other hand, the amount of Mg to be arranged is preferably 3.48 mg / cm 2 or less, and more preferably 2.61 mg / cm 2 or less.

[0032] (Lamination Step S02) Next, the copper plate 22 and the ceramic substrate 11 are laminated via the Mg foil 25, and the ceramic substrate 11 and the copper plate 23 are laminated via the Mg foil 25.

[0033] (Bonding step S03) Next, the laminated copper plate 22, Mg foil 25, ceramic substrate 11, Mg foil 25, and copper plate 23 are pressed in the lamination direction, loaded into a vacuum furnace and heated to bond the copper plate 22, the ceramic substrate 11, and the copper plate 23.

[0034] Here, the holding temperature in the bonding step S03 is preferably in the range of 700°C or higher and 850°C or lower. And the temperature integral value S in the temperature rising process from 670°C to the holding temperature and the holding process at the heating temperature is preferably in the range of 30°C·h or higher and 500°C·h or lower. Also, the pressing load P in the bonding step S03 is preferably in the range of 0.09 MPa or higher and 1.96 MPa or lower.

[0035] And the product P×S of the pressing load P and the temperature integral value S is preferably in the range of 30°C·h·MPa or higher and 650°C·h·MPa or lower. By setting the product P×S of the pressing load P and the temperature integral value S within the above range, the discharge state of the liquid phase generated during bonding is adjusted, oxygen-containing substances contained in the liquid phase can be discharged from the interface, and the area ratio of the precipitated MgO particles 33 in the Mg solid solution layer 31 can be controlled.

[0036] Furthermore, the dew point in the furnace atmosphere in the bonding step S03 is preferably -61°C or lower. By setting the dew point in the furnace atmosphere to -61°C or lower, the area ratio of the precipitated MgO particles 33 in the Mg solid solution layer 31 can be controlled. Also, the cooling rate during cooling is preferably in the range of 2°C / min or higher and 20°C / min or lower. Here, the cooling rate is the average value of the cooling rates from the holding temperature to 670°C.

[0037] As described above, the insulating circuit board 10 of the present embodiment is manufactured by the Mg arrangement step S01, the lamination step S02, and the bonding step S03.

[0038] (Heat sink bonding step S04) Next, the heat sink 5 is bonded to the other surface side of the metal layer 13 of the insulating circuit board 10. The insulating circuit board 10 and the heat sink 5 are laminated via a solder material and loaded into a heating furnace, and the insulating circuit board 10 and the heat sink 5 are soldered together via the solder layer 7.

[0039] (Semiconductor element bonding step S05) Next, the semiconductor element 3 is bonded to one surface of the circuit layer 12 of the insulating circuit board 10 by soldering. By the above-described steps, the power module 1 shown in FIG. 1 is manufactured.

[0040] According to the insulating circuit board 10 (copper / ceramics bonded body) of the present embodiment configured as described above, an Mg solid solution layer 31 in which Mg is solid-solved in the Cu matrix phase is formed at the bonding interface between the ceramics substrate 11 and the circuit layer 12 (metal layer 13). In the region E from the bonding surface of the ceramics substrate 11 to the circuit layer 12 (metal layer 13) side up to 15 μm, the area ratio of the MgO particles 33 precipitated in the Mg solid solution layer 31 is 15% or less. Therefore, it is possible to suppress the hardening of the bonding interface due to precipitation hardening, and it is possible to suppress the occurrence of cracks in the ceramics substrate 11 during the thermal cycle load. Therefore, it is possible to obtain an insulating circuit board 10 having high bonding strength and particularly excellent thermal cycle reliability.

[0041] In order to further improve the thermal cycle reliability, it is preferable that the area ratio of the MgO particles 33 precipitated in the Mg solid solution layer 31 in the region E from the bonding surface of the ceramics substrate 11 to the circuit layer 12 (metal layer 13) side up to 15 μm is 12% or less, and more preferably 8% or less.

[0042] Further, in the insulating circuit board 10 of the present embodiment, when the average value of the indentation hardness at the position X 10 μm from the bonding surface of the ceramic substrate 11 toward the circuit layer 12 (metal layer 13) side is 100 mgf / μm 2 or more and 180 mgf / μm 2 or less, the ceramic substrate 11 and the circuit layer 12 (metal layer 13) are surely and firmly joined by Mg, and further suppression of hardening of the bonding interface is achieved. Therefore, an insulating circuit board 10 with high bonding strength and particularly excellent thermal cycle reliability can be obtained.

[0043] In addition, in order to further improve the thermal cycle reliability, it is preferable that the average value of the indentation hardness at the position X 10 μm from the bonding surface of the ceramic substrate 11 toward the circuit layer 12 (metal layer 13) side is 170 mgf / μm 2 or less, and more preferably 160 mgf / μm 2 or less. On the other hand, in order to more surely join the ceramic substrate 11 and the circuit layer 12 (metal layer 13), it is preferable that the average value of the indentation hardness at the position X 10 μm from the bonding surface of the ceramic substrate 11 toward the circuit layer 12 (metal layer 13) side is 115 mgf / μm 2 or more, and more preferably 125 mgf / μm 2 or more.

[0044] As described above, the embodiments of the present invention have been described, but the present invention is not limited thereto, and can be appropriately changed without departing from the technical idea of the invention. For example, in the present embodiment, the description has been made assuming that a semiconductor element is mounted on the insulating circuit board to form a power module, but the present invention is not limited thereto. For example, an LED element may be mounted on the circuit layer of the insulating circuit board to form an LED module, or a thermoelectric element may be mounted on the circuit layer of the insulating circuit board to form a thermoelectric module.

[0045] In addition, in the insulating circuit board of the present embodiment, although the ceramic substrate is described by taking the one made of aluminum nitride (AlN) as an example, the present invention is not limited to this, and other ceramic substrates such as alumina (Al2O3) and silicon nitride (Si3N4) may be used.

[0046] Furthermore, in the present embodiment, although the circuit layer is described as being formed by bonding a rolled plate of oxygen-free copper to a ceramic substrate, the present invention is not limited to this, and a circuit layer may be formed by bonding copper pieces punched from a copper plate to a ceramic substrate in a state where they are arranged in a circuit pattern. In addition, in the present embodiment, although the Mg foil is described as being disposed between the ceramic substrate and the copper plate, the present invention is not limited to this, and it is sufficient that a bonding material is disposed between the ceramic substrate and the copper plate. Mg may be disposed on the bonding surface of the ceramic substrate, or Mg may be disposed on the bonding surface of the copper plate. Further, Mg may be disposed by sputtering or vapor deposition on the ceramic substrate and / or the copper plate. A clad material of the copper plate and the Mg foil may also be used. Note that Mg can also be disposed between the ceramic substrate and the copper plate using a paste containing Mg powder and / or MgH2 powder.

Examples

[0047] The results of the confirmation experiments conducted to confirm the effects of the present invention will be described below.

[0048] First, ceramic substrates (40 mm × 40 mm) described in Table 1 were prepared. The thicknesses were 0.635 mm for AlN and Al2O3, and 0.32 mm for Si3N4. In addition, as the copper plate to be the circuit layer and the metal layer, a 37 mm × 37 mm copper plate made of oxygen-free copper and having the thickness shown in Table 1 was prepared.

[0049] Then, the copper plate and the ceramic substrate were bonded under the conditions shown in Table 1 to obtain the insulating circuit boards (copper / ceramic joints) of Invention Examples 1 to 9 and Comparative Example 1. Here, during bonding, the exhaust of the furnace gas and the introduction of dry air were repeated to obtain the dew point shown in Table 1. The dew point was measured using an MBW973L manufactured by Technica Measuring Co., Ltd.

[0050] For the obtained insulating circuit board (copper / ceramics joint), the area ratio of MgO particles in the Mg solid solution layer, the indentation hardness, and the thermal cycle reliability (crack of the ceramics substrate, bonding rate after thermal cycle loading) were evaluated as follows.

[0051] (Area ratio of MgO particles in the Mg solid solution layer) The cross-section of the bonding interface between the circuit layer, metal layer, and ceramics substrate was observed, and five elemental maps were obtained for a 200 μm × 15 μm region in the Mg solid solution layer by EPMA for each of five fields of view. Regions where Mg and O coexisted and the O concentration was 35 atomic% or more and 65 atomic% or less with Mg concentration + O concentration = 100 atomic% were defined as precipitated MgO particles, and the area ratio was calculated, and the average value of five fields of view, a total of 10 locations, was obtained.

[0052] (Indentation hardness) The obtained insulating circuit board (copper / ceramics joint) was cut in the stacking direction, and at the bonding interface between the ceramics substrate and the circuit layer and metal layer, the indentation hardness at position X, which was 10 μm from the bonding surface of the ceramics substrate toward the circuit layer and metal layer side, was measured at five locations in each of five fields of view, for a total of 50 locations, and the average value was obtained.

[0053] (Thermal cycle reliability) For the above-mentioned insulating circuit board, a thermal shock tester (TSA-72ES manufactured by Espec Corporation) was used to apply a thermal cycle in the gas phase, and the presence or absence of cracks in the ceramics was determined by SAT inspection. The conditions of the thermal cycle were set as follows according to the material of the ceramics substrate. In the case of AlN and Al2O3: -40°C × 15 min ←→ 150°C × 15 min up to 1000 cycles, with SAT inspection every 100 cycles. For Si3N4: -40°C × 15 min ←→ 150°C × 15 min up to 3000 cycles, SAT inspection every 200 cycles.

[0054] (Bonding rate) The bonding rate before the thermal cycling load and the bonding rate after the thermal cycling load were evaluated as follows. When cracks were confirmed in the ceramic substrate, the bonding rate at that time was evaluated. Regarding the insulating circuit board, the bonding rate at the interface between the ceramic substrate and the copper plate (circuit layer and metal layer) was evaluated using an ultrasonic flaw detector (FineSAT FSP8V manufactured by Hitachi Power Solutions Co., Ltd.), and the bonding rate was calculated from the following formula.

[0055] Here, the initial bonding area was defined as the area to be bonded before bonding, that is, the area of the circuit layer and the metal layer (37 mm × 37 mm) in this example. (Bonding rate) = {(Initial bonding area) - (Peeled area)} / (Initial bonding area) In the binarized image of the ultrasonic flaw detection image, peeling is indicated by the white part within the joint, so the area of this white part was taken as the peeled area.

[0056] [Table 1]

[0057] [Table 2]

[0058] First, compare Invention Examples 1-3 using AlN as the ceramic substrate with Comparative Example 1. In Comparative Example 1, the precipitation area ratio of MgO particles precipitated in the Mg solid solution layer in the region from the bonding surface of the ceramic substrate to the copper plate side up to 15 μm was 22.4%, and the number of crack occurrences in the thermal cycling test was 200 times. On the other hand, in Invention Examples 1-3, the area ratio of the MgO particles precipitated in the Mg solid solution layer in the region from the bonding surface of the ceramic substrate to the copper plate side up to 15 μm is 15% or less. In the thermal cycle test, the number of crack occurrences exceeded 700 to 1000 times, and it was excellent in thermal cycle reliability.

[0059] Next, Invention Examples 4-6 using Si3N4 as the ceramic substrate are compared with Comparative Example 2. In Comparative Example 2, the area ratio of the MgO particles precipitated in the Mg solid solution layer in the region from the bonding surface of the ceramic substrate to the copper plate side up to 15 μm is 19.2%. In the thermal cycle test, the number of crack occurrences was 1600 times. On the other hand, in Invention Examples 4-6, the area ratio of the MgO particles precipitated in the Mg solid solution layer in the region from the bonding surface of the ceramic substrate to the copper plate side up to 15 μm is 15% or less. In the thermal cycle test, the number of crack occurrences exceeded 2600 to 3000 times, and it was excellent in thermal cycle reliability.

[0060] Next, Invention Examples 7 and 8 using Al2O3 as the ceramic substrate are compared with Comparative Example 3. In Comparative Example 3, the area ratio of the MgO particles precipitated in the Mg solid solution layer in the region from the bonding surface of the ceramic substrate to the copper plate side up to 15 μm is 24.8%. In the thermal cycle test, the number of crack occurrences was 200 times. On the other hand, in Invention Examples 7 and 8, the area ratio of the MgO particles precipitated in the Mg solid solution layer in the region from the bonding surface of the ceramic substrate to the copper plate side up to 15 μm is 15% or less. In the thermal cycle test, the number of crack occurrences was 900 to 1000 times, and it was excellent in thermal cycle reliability.

[0061] From the results of the above confirmation experiments, according to the invention examples, even when a severe thermal cycle is applied, the occurrence of cracks in the ceramic member can be suppressed, and it was confirmed that an insulating circuit board (copper / ceramic joint) excellent in thermal cycle reliability can be provided.

Explanation of Reference Numerals

[0062] 10 Insulated circuit board (copper / ceramics joint) 11 Ceramic substrate (ceramics member) 12 Circuit layer (copper member) 13 Metal layer (copper member) 31 Mg solid solution layer 33 MgO particles

Claims

1. A copper / ceramics joined body in which a copper member made of copper or a copper alloy and a ceramics member are joined, on the joining interface between the ceramics member and the copper member, a Mg solid solution layer in which Mg is solid-solved in a Cu matrix is formed, in a region from the joining surface of the ceramics member to the copper member side up to 15 μm, the area ratio of MgO particles precipitated in the Mg solid solution layer is 15% or less, and the average value of the indentation hardness at a position 10 μm from the joining surface of the ceramics member to the copper member side is in the range of 100 mgf / μm2 or more and 180 mgf / μm2 or less. A copper / ceramics joined body characterized by this.

2. An insulating circuit board in which a copper plate made of copper or a copper alloy is joined to the surface of a ceramics substrate, on the joining interface between the ceramics substrate and the copper plate, a Mg solid solution layer in which Mg is solid-solved in a Cu matrix is formed, in a region from the joining surface of the ceramics substrate to the copper plate side up to 15 μm, the area ratio of MgO particles precipitated in the Mg solid solution layer is 15% or less, and the average value of the indentation hardness at a position 10 μm from the joining surface of the ceramics substrate to the copper plate side is in the range of 100 mgf / μm2 or more and 180 mgf / μm2 or less. An insulating circuit board characterized by this.

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