Composite substrate and manufacturing method thereof

Abstract

To provide a composite substrate with small warpage and high heat dissipation properties.SOLUTION: A composite substrate includes a metal substrate having a first surface and a second surface opposite to the first surface, a ceramic substrate, and a bonding member disposed on the first surface and bonding the metal substrate and the ceramic substrate, and the ceramic substrate has a plurality of compartments with grooves between adjacent compartments, and the bonding member is present in the grooves.SELECTED DRAWING: Figure 1A

Description

[Technical field]

[0001] The present disclosure relates to a composite substrate and a method for manufacturing the same. [Background technology]

[0002] In ceramic substrates, composite substrates are known in which a ceramic substrate is bonded to a metal substrate in order to enhance heat dissipation. In large-area composite substrates, stress is generated due to the difference in thermal expansion coefficient between the ceramic substrate and the metal substrate when they are bonded together, and the ceramic substrate may warp or crack. In order to suppress such stress, a method is known in which a weak portion is provided in advance in the substrate to induce cracking (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Utility Model Application Publication No. 62-103266 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of one aspect of the present disclosure is to provide a composite substrate with reduced warping and high heat dissipation properties, and a method for manufacturing the same. [Means for solving the problem]

[0005] A first aspect of the present disclosure is a composite substrate comprising a metal substrate having a first surface and a second surface opposite to the first surface, a ceramic substrate, and a joining member disposed on the first surface and joining the metal substrate and the ceramic substrate, the ceramic substrate having a plurality of compartments, a groove between adjacent compartments, and the joining member being present in the groove.

[0006] A second aspect of the present disclosure is a method for manufacturing a composite substrate, comprising: preparing a metal substrate having a first surface and a second surface opposite to the first surface, a ceramic substrate having a groove, and a bonding material; arranging the bonding material on the first surface; arranging the ceramic substrate on the bonding material so that the surface opposite to the surface having the groove or the surface having the groove faces the bonding material; and heating the bonding material to form a bonding member while pressing at least one of the ceramic substrate and the metal substrate toward the other, thereby bonding the ceramic substrate and the metal substrate, wherein in bonding the ceramic substrate and the metal substrate, the ceramic substrate is at least partially cracked along the groove, and the bonding member is placed in the cracked groove. Effect of the Invention

[0007] According to one aspect of the present disclosure, it is possible to provide a composite substrate with reduced warping and high heat dissipation properties, and a method for manufacturing the same. [Brief description of the drawings]

[0008] [Figure 1A] 1 is a schematic plan view showing a composite substrate according to a first embodiment. [Figure 1B] FIG. 1B is a schematic cross-sectional view showing a cross section taken along line IB-IB in FIG. 1A. [Figure 2A] 1 is a schematic cross-sectional view showing a prepared metal substrate in a manufacturing method for a composite substrate according to a first embodiment. [Figure 2B] 3 is a schematic cross-sectional view showing a state in which a bonding material is disposed on a metal substrate in the manufacturing method for the composite substrate according to the first embodiment. FIG. [Figure 2C] 3 is a schematic cross-sectional view showing a state in which a ceramic substrate is placed on a bonding material in the method for manufacturing a composite substrate in accordance with the first embodiment. FIG. [Figure 2D] 3 is a schematic cross-sectional view showing a state in which a ceramic substrate and a metal substrate are joined together in a manufacturing method for a composite substrate in accordance with the first embodiment. FIG. [Figure 3A]10 is a schematic cross-sectional view showing a state in which a ceramic substrate is placed on a bonding material in a manufacturing method for a composite substrate in accordance with a second embodiment. FIG. [Figure 3B] FIG. 4 is a schematic cross-sectional view showing a composite substrate according to a second embodiment. [Figure 4A] 11 is a schematic cross-sectional view showing a state in which a ceramic substrate is placed on a bonding material in a manufacturing method for a composite substrate in accordance with a third embodiment. FIG. [Figure 4B] FIG. 11 is a schematic cross-sectional view showing a composite substrate according to a third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment according to the present disclosure will be described with reference to the drawings. However, the embodiment described below is for embodying the technical idea according to the present disclosure, and the invention is not limited to the following unless otherwise specified. The contents described in one embodiment are applicable to other embodiments and modified examples. In addition, the drawings are schematic diagrams of the embodiments, and in order to clarify the description, the scale, interval, positional relationship, etc. of each member may be exaggerated, or some of the members may be omitted, or an end view showing only the cut surface may be used as a cross-sectional view. The directions shown in each figure indicate the relative positions between the components, and are not intended to indicate absolute positions. In addition, the same names and symbols indicate, in principle, the same or homogeneous members, and detailed descriptions are omitted as appropriate.

[0010] (First embodiment) A composite substrate 1a according to a first embodiment and a manufacturing method thereof will be described with reference to Figs. 1A, 1B, and 2A to 2D. Fig. 1A is a schematic plan view showing the composite substrate 1a. Fig. 1B is a schematic cross-sectional view showing a cross section taken along line IB-IB in Fig. 1A. Figs. 2A to 2D are schematic cross-sectional views for explaining a manufacturing method of the composite substrate 1a shown in Figs. 1A and 1B.

[0011] The composite substrate 1a of the first embodiment according to the present disclosure comprises a metal substrate 2 having a first surface 21 and a second surface 22 opposite the first surface 21, a ceramic substrate 3, and a joining member 4 arranged on the first surface 21 and joining the metal substrate 2 and the ceramic substrate 3, the ceramic substrate 3 having a plurality of compartments 31 with grooves 32 between adjacent compartments 31, and the joining member 4 being present in the grooves 32.

[0012] The manufacturing method of the composite substrate 1a of the first embodiment according to the present disclosure includes (a) preparing a metal substrate 2 having a first surface 21 and a second surface 22 opposite to the first surface 21, a ceramic substrate 3 having a groove 32, and a bonding material 4a, (b) disposing the bonding material 4a on the first surface 21, (c) disposing the ceramic substrate 3 on the bonding material 4a so that the surface opposite to the surface having the groove 32 faces the bonding material 4a, and (d) heating the bonding material 4a to form a bonding member 4 while pressing at least one of the ceramic substrate 3 and the metal substrate 2 toward the other, and bonding the ceramic substrate 3 and the metal substrate 2 together, in which the ceramic substrate 3 is at least partially cracked along the groove 32, and the bonding material 4a is disposed in the cracked groove 32 and heated to form the bonding member 4. The manufacturing process will be described in detail below.

[0013] (a) Preparing a metal substrate 2, a ceramic substrate 3, and a bonding material 4a A metal substrate 2 having a first surface 21 and a second surface 22 opposite to the first surface 21, a ceramic substrate 3 having a groove 32, and a bonding material 4a are prepared (FIG. 2A). Note that the ceramic substrate 3 and the bonding material 4a are not shown in FIG. 2A.

[0014] The metal substrate 2 supports the ceramic substrate 3 in the composite substrate 1a. In addition, the metal substrate 2 has a higher thermal conductivity than the ceramic substrate 3, and therefore transfers the heat transferred to the ceramic substrate 3 to the metal substrate 2, thereby efficiently dissipating the heat to the outside.

[0015] The thickness of the metal substrate 2 is not particularly limited, but is preferably 200 μm to 2.0 mm, more preferably 300 μm to 1.5 mm. By making the thickness of the metal substrate 2 200 μm or more, the heat capacity of the metal substrate 2 is increased, and the heat dissipation property is further improved. By making the thickness of the metal substrate 2 2.0 mm or less, the thickness of the composite substrate 1a is reduced, which is advantageous for miniaturization and low height.

[0016] The material of the metal substrate 2 is not particularly limited as long as it has high thermal conductivity. The material of the metal substrate 2 may contain at least one of Cu and Al. The metal substrate 2 may be substantially made of Cu or Al.

[0017] The ceramic substrate 3 is an insulating member that serves as a base on which wiring and the like will later be arranged. The ceramic substrate 3 has a first surface 33 and a second surface 34 that is the opposite side to the first surface 33. The ceramic substrate 3 has a groove 32 on the first surface 33 side. The ceramic substrate 3 has a plurality of sections 31 divided by the grooves 32. The grooves 32 are bottomed grooves. The grooves 32 are arranged in a lattice pattern on the first surface side 33 side in a plan view. That is, one section 31 is rectangular in a plan view.

[0018] The thickness of the ceramic substrate 3 may be preferably 50 μm or more and 500 μm or less, for example, 100 μm or more and 400 μm or less, or 150 μm or more and 300 μm or less.

[0019] The length of one side of one section 31 may be preferably 30 mm or less, more preferably 25 mm or less, for example 20 mm or less. By setting the length of one side of one section 31 within the above range, it is possible to reduce stress when the composite substrate 1a is formed, for example, stress due to the difference in thermal expansion coefficient between the metal substrate 2 and the ceramic substrate 3, and to suppress warping of the composite substrate 1a. The length of one side of one section 31 may be preferably 3 mm or more, more preferably 5 mm or more. By setting the length of one side of one section 31 within the above range, the degree of freedom in arranging wiring and the like on the composite substrate 1a is improved.

[0020] The depth of the grooves 32 may be preferably 1 / 5 to 4 / 5, more preferably 2 / 5 to 3 / 5, of the thickness of the ceramic substrate 3. By making the depth of the grooves 32 1 / 5 or more of the thickness of the ceramic substrate 3, the ceramic substrate 3 is more likely to crack along the grooves 32 when attached to the metal substrate 2, making it easier to separate the individual sections 31 and thus easing the stress of the composite substrate 1a. By making the depth of the grooves 32 4 / 5 or less of the thickness of the ceramic substrate 3, the strength of the ceramic substrate 3 is ensured and it is easier to handle.

[0021] The depth of the groove 32 may preferably be 10 μm or more and 400 μm or less, for example, 20 μm or more and 300 μm or less, 30 μm or more and 240 μm or less, 40 μm or more and 240 μm or less, or 60 μm or more and 180 μm or less.

[0022] The grooves 32 can be formed by, for example, etching, blasting, or laser processing. Alternatively, the ceramic substrate 3 with the grooves 32 formed therein may be purchased.

[0023] From the viewpoint of heat dissipation, the material of the ceramic substrate 3 is preferably a ceramic with high thermal conductivity. For example, the material of the ceramic substrate 3 may be a nitride-based ceramic such as silicon nitride, aluminum nitride, or boron nitride, or an oxide-based ceramic such as aluminum oxide, silicon oxide, calcium oxide, or magnesium oxide. The ceramic substrate 3 is preferably a nitride-based ceramic.

[0024] (b) Placing the joining material 4a A bonding material 4a is placed on the first surface 21 of the metal substrate 2 (FIG. 2B). The bonding material 4a is sintered by heating to become a bonding member 4, which bonds the ceramic substrate 3 and the metal substrate 2 together.

[0025] For example, the bonding material 4a may be a first metal paste containing a metal powder, an active metal powder, and an organic binder. As described later, the first metal paste may be fired at a temperature of 780° C. or higher and 1100° C. or lower.

[0026] As an example, the first metal paste preferably contains, before sintering, 63% by mass to 85% by mass of metal powder, 1% by mass to 15% by mass of active metal powder, and 5% by mass to 15% by mass of an organic binder as a solvent. The first metal paste, which is the joining material 4a, becomes a metal body, which is a joining member 4, after firing. The surface of the metal powder may be covered with a coating metal member, and the coating metal member may be included in the metal body after firing. The active metal powder becomes a metal compound after firing. The first metal paste may contain an inorganic filler other than metal.

[0027] The median diameter of the metal powder is preferably 1 μm or more and 50 μm or less, more preferably 5 μm or more and 40 μm or less. When the metal powder is 1 μm or more, it is difficult to aggregate and is easy to handle. When the metal powder is 50 μm or less in size, the thickness of the joining member can be made thin. The metal powder is preferably in a state where it is dispersed in the first metal paste together with the active metal powder, the organic binder, and possibly the inorganic filler. When the first metal paste contains a metal powder that does not melt even when fired, the metal powder may be in a state where it is dispersed in the metal body after firing. In other words, when only metal powders having a melting point below or near the firing temperature are used in the metal powder, all the metal powders become metal bodies by firing, but when the metal powder contains a metal powder having a melting point higher than the firing temperature, some of the metal powders remain in the metal body. When a metal powder having a melting point equal to or lower than the firing temperature is heated to above its melting point, it melts and becomes liquid. However, when a metal powder having a melting point higher than the firing temperature is used, the metal powder itself does not melt and become liquid because it is heated at a temperature lower than the melting point of the metal powder. Since the metal powder is not melted and becomes liquid, significant flow is unlikely to occur in the first metal paste. Furthermore, by containing an inorganic filler that does not melt in the first metal paste, the volumetric shrinkage of the first metal paste is suppressed, and warping can be reduced. However, even if the metal powder is fired at a temperature lower than the melting point, a part of the surface of the metal powder may be softened due to reaction with the coated metal member, particle size, firing atmosphere, etc., and may be arranged in a state of contact or mixture with other metal powders. In this case, there may be an interface between the metal powder and the metal body, but there may be no interface. In this way, it is possible to make the metal powder and the metal body in a state without an interface, thereby lowering the electrical resistance value and increasing the electrical conductivity and thermal conductivity.

[0028] For example, all or at least a part of the metal powder preferably contains at least one selected from Ag, Al, Zn, Sn, and Ag-Cu alloys. In particular, Ag and Ag-Cu alloys are preferable. Since the melting point of Ag is 962°C and the melting point of Ag-Cu alloy is around 780°C, they can be fired at a relatively low temperature.

[0029] The metal powder may contain at least one selected from, for example, Cu, Cr, and Ni. The metal powder may also include an alloy mainly composed of Cu, Cr, and Ni. The metal powder is preferably Cu or a Cu alloy. This is because Cu, Cr, and Ni have high thermal conductivity. Cu, Cr, and Ni have high melting points, and when the firing temperature is below the melting points of these metals, these metals do not melt and are dispersed in the metal body, resulting in high thermal conductivity. In addition, at least one selected from Cu, Cr, and Ni may be coated with at least one coated metal member selected from Ag, Al, Zn, Sn, and Ag-Cu alloy. In other words, since the metal powder is coated with a coated metal member of a predetermined thickness, the metal powders do not come into contact with each other or are separated from each other more than necessary even after firing. In this way, the metal powder is appropriately dispersed, and thus the uneven distribution of heat in the through hole can be suppressed.

[0030] The active metal powder becomes at least partially or entirely a metal compound by firing. The metal compound may be disposed between the metal powders or in a layer at the interface with the ceramic substrate 3. The active metal powder is dispersed in the first metal paste, and the metal compound after firing is also dispersed in the metal body. For example, when titanium hydride (TiH2) is used as the active metal powder, the titanium hydride releases hydrogen by firing, while the titanium is oxidized or nitrided to become titanium oxide or titanium nitride. When the ceramic substrate 3 is a nitride-based ceramic, the active metal powder contained in the first metal paste reacts with the nitrogen in the ceramic substrate, and a reaction layer of titanium nitride is formed at the interface between the first metal paste and the ceramic substrate. When the ceramic substrate 3 is an oxide-based ceramic, the active metal powder contained in the first metal paste reacts with the oxygen in the ceramic substrate, and a reaction layer of titanium oxide is formed at the interface between the first metal paste and the ceramic substrate. In addition, the reactants of the metal compounds such as titanium nitride and titanium oxide are disposed so as to be continuous or disposed at the grain boundaries in the spaces between the metal powders. The metal compound is disposed in direct contact with the metal powder, surrounding the metal powder, or surrounding the inorganic filler, and improves the adhesive strength with the ceramic substrate.

[0031] The active metal powder is preferably one or more materials selected from, for example, TiH2, CeH2, ZrH2, LaH2, and MgH2. By firing this active metal powder, all or a part of the hydrogen is released, and it reacts with nitrogen, oxygen, carbon, etc. contained in the ceramic substrate, inorganic filler, etc., and changes to metal nitrides, metal oxides, metal carbides, etc. These changed substances are metal compounds. In particular, it is preferable to use TiH2 as the active metal powder, and by containing TiH2, it reacts with nitrogen contained in the ceramic substrate, etc., and forms a reaction layer such as TiN.

[0032] The inorganic filler is dispersed in the first metal paste to reduce the occurrence of cracks. Furthermore, by making the particle size of the inorganic filler uniform, the thickness of the ceramic substrate and the metal substrate can be made uniform. Examples of the inorganic filler include ceramic filler, metal filler, and glass filler. Specifically, the inorganic filler may be aluminum oxide, silicon oxide, or the like. The inorganic filler is contained in a content range that does not interfere with the effects of other contents.

[0033] The organic binder is a material contained in the first metal paste before firing. After firing, the organic binder evaporates and does not remain in the first metal paste. One example of the organic binder is a solvent that is generally used as a via material. or It may be made of a resin material.

[0034] As a different example of the bonding material 4a, a second metal paste may be used that contains an organic solvent having a boiling point of 200°C or more and 300°C or less and having reducing properties at a ratio of 5% to 20% of the weight of the metal particles. As described later, the second metal paste may be fired at a temperature of 150°C or more and 300°C or less. When the boiling point of the second metal paste is in the firing temperature range or a slightly lower temperature range, the organic solvent can be vaporized and removed during firing of the second metal paste. In addition, when the organic solvent has reducing properties, oxidation of the metal particles can be suppressed and sintering can be promoted. However, the boiling point of the organic solvent contained in the second metal paste may be in a temperature range slightly lower than the firing temperature. This is because the organic solvent may vaporize even at a temperature range lower than the firing temperature. This is due to the thickness and size of the second metal paste, the way heat is applied to the second metal paste during firing, and the like. Here, the boiling point of the organic solvent contained in the second metal paste, which is in a temperature range slightly lower than the firing temperature, means that the boiling point of the organic solvent may be in a temperature range that is lower than the firing temperature and the difference from the firing temperature is 80°C or less, or 50°C or less.

[0035] The second metal paste used as the bonding material 4a contains at least one type of metal powder, for example, Ag or Cu. By using the second metal paste as the bonding material 4a, the heating temperature for bonding the ceramic substrate 3 and the metal substrate 2 can be made relatively low, and the load on the ceramic substrate 3 and the metal substrate 2 can be reduced. For example, the stress due to the difference in the thermal expansion coefficient between the ceramic substrate 3 and the metal substrate 2 can be reduced, and thus the warping of the composite substrate 1a can be reduced.

[0036] The median diameter of the metal powder is preferably 0.1 μm or more and 20 μm or less, more preferably 0.5 μm or more and 10 μm or less, and even more preferably 1 μm or more and 5 μm or less. By making the median diameter of the metal powder 0.1 μm or more, aggregation can be suppressed. On the other hand, by making the median diameter of the metal powder 20 μm or less, the packing property can be improved. In addition, the shape of the metal powder is preferably spherical or elliptical from the viewpoint of fluidity, but it may be flat or acicular. This is because making the shape flat or acicular can increase contact between particles and increase thermal conductivity.

[0037] The second metal paste used as the bonding material 4a may further contain an organic resin binder. The viscosity of the bonding material 4a can be adjusted by the type and amount of the organic resin binder. As the organic resin binder, for example, a solvent generally used in metal pastes, or a resin material such as acrylic, epoxy, urethane, ethyl cellulose, silicone, phenol, polyimide, polyurethane, melamine, or urea can be used. The organic resin binder can be decomposed by heating, which will be described later, and evaporated and removed.

[0038] The method of arranging the bonding material 4a is not particularly limited. For example, when the bonding material 4a is a first metal paste or a second metal paste, the first metal paste or the second metal paste can be applied and arranged on the first surface 21 of the metal substrate 2 so as to be in close contact with the first surface 21. The bonding material 4a arranged on the first surface 21 of the metal substrate 2 becomes the bonding member 4 by a subsequent heating process.

[0039] The thickness of the layer of the bonding material 4a on the first surface 21 of the metal substrate 2 is preferably 5 μm or more and 250 μm or less, more preferably 10 μm or more and 200 μm or less, and further preferably 20 μm or more and 100 μm or less.

[0040] (c) Arranging the ceramic substrate 3 The ceramic substrate 3 is placed on the bonding material 4a so that the surface opposite to the surface having the grooves 32 faces the bonding material 4a (FIG. 2C). The method of placing the ceramic substrate 3 is not particularly limited.

[0041] (d) Bonding the ceramic substrate 3 and the metal substrate 2 While pressing at least one of the ceramic substrate 3 and the metal substrate 2 toward the other, the bonding material 4a is heated to form the bonding member 4, thereby bonding the ceramic substrate 3 and the metal substrate 2 (FIG. 2D). In this way, the composite substrate 1a according to the first embodiment is obtained.

[0042] The ceramic substrate 3 and the metal substrate 2 may be joined by, for example, pressing the ceramic substrate 3 toward the metal substrate 2, or pressing the metal substrate 2 toward the ceramic substrate 3. As a result, the ceramic substrate 3 is cracked along the grooves 32. In the first embodiment, the ceramic substrate 3 is cracked along all the grooves 32, but this is not limited thereto, and it is sufficient that at least a part of the ceramic substrate 3 is cracked. For example, the ceramic substrate 3 may be cracked in preferably 30% or more of the grooves 32, more preferably 50% or more, even more preferably 70% or more, even more preferably 90% or more, and particularly preferably 95% or more. The ceramic substrate 3 is divided into sections 31 by cracking along the grooves 32. The ceramic substrate 3 is divided into sections 31, which can reduce stress due to the difference in thermal expansion coefficient between the ceramic substrate 3 and the metal substrate 2, and can thus reduce warping of the composite substrate 1a. Furthermore, the ceramic substrate 3 is cracked along the grooves 32, and the bonding material 4a enters the grooves 32. The division of the ceramic substrate 3 does not necessarily have to occur only by the above-mentioned pressing force, but may also occur due to thermal expansion caused by heating as described below.

[0043] The magnitude of the pressure is preferably 0.01 MPa or more and 10 MPa or less, more preferably 0.05 MPa or more and 5 MPa or less. By applying the pressure in this range, it becomes easy to split the ceramic substrate 3 along the grooves 32.

[0044] The pressing method is not particularly limited, but a method capable of pressing the entire ceramic substrate 3 or metal substrate 2 is preferable. For example, a method of pressing the entire ceramic substrate 3 or metal substrate 2 using a plate, or a method of pressing the entire ceramic substrate 3 or metal substrate 2 in one direction or two perpendicular directions using a roller can be mentioned. Pressing the entire substrate makes it easier to crack the entire groove 32 of the ceramic substrate 3. In pressing, pressing is preferably performed via a cushioning material. The cushioning material is preferably disposed between the ceramic substrate 3 and a pressing device, such as a plate. Pressing via a cushioning material can prevent the ceramic substrate 3 from cracking in unintended portions, i.e., portions other than the groove 32.

[0045] The heating temperature in the above heating is appropriately selected depending on the bonding material 4a used. For example, when the bonding material 4a is the second metal paste, the heating temperature is, for example, 150°C to 300°C, preferably 180°C to 280°C. When the bonding material 4a is the first metal paste, the heating temperature is, for example, 780°C to 1100°C, preferably 800°C to 1050°C. The bonding material 4a becomes the bonding member 4 by heating. For example, when the bonding material 4a is the first metal paste, the bonding material 4a is sintered to become the bonding member 4. The metal substrate 2 and the ceramic substrate 3 are bonded by the bonding member 4.

[0046] As described above, when the ceramic substrate 3 and the metal substrate 2 are bonded together, the ceramic substrate 3 is at least partially cracked along the grooves 32. The bonding material 4a enters the broken grooves 32 and becomes the bonding members 4 when heated. In this manner, the ceramic substrate 3 is cracked along the grooves 32, resulting in the ceramic substrate 3 being divided into sections 31 by the grooves 32. The bonding members 4 are disposed in the grooves 32.

[0047] Since the ceramic substrate 3 is divided into sections 31, the effect of stress due to the difference in thermal expansion coefficient between the ceramic substrate 3 and the metal substrate 2 is reduced, and warping of the composite substrate 1a is reduced. The amount of warping of the composite substrate 1a is preferably 300 μm or less, more preferably 200 μm or less, and even more preferably 100 μm or less. The amount of warping means the maximum distance in the thickness direction (i.e., the lamination direction) from a straight line connecting both ends of the upper surface of the composite substrate 1a (in the first embodiment, the first surface 33 of the ceramic substrate 3) to the upper surface located between the both ends. The amount of warping can be measured, for example, by a laser microscope or a contact-type step measuring instrument. For example, a VR-5200 manufactured by Keyence can be used. A contact-type step measuring instrument (Alpha-Step D-500 manufactured by KLA-Tenchore) may also be used.

[0048] Furthermore, in the composite substrate 1a, by arranging the bonding members 4 in the grooves 32, the contact area between the ceramic substrate 3 and the bonding members 4 is increased, improving the thermal conductivity between the ceramic substrate 3 and the bonding members 4, and improving the heat dissipation effect.

[0049] In the composite substrate 1a, the bonding material is heated while at least one of the ceramic substrate 3 and the metal substrate 2 is pressed toward the other, so that the air contained in the bonding material 4a or the gas generated by heating is pushed out to the outside, reducing the porosity in the resulting bonding member 4. In particular, since the ceramic substrate 3 is cracked at the grooves 32 in this process, the grooves 32 also function as exhaust portions for the gas, thereby further reducing the porosity in the bonding member 4.

[0050] The porosity of the bonding members 4 below the sections 31 of the ceramic substrate 3 is preferably 1% or less, and more preferably 0.5% or less. By reducing the porosity of the bonding members 4, the thermal conductivity of the bonding members 4 is improved, and the heat dissipation effect of the composite substrate 1a is improved.

[0051] The thickness of the bonding members 4 is preferably 5 μm or more and 200 μm or less, more preferably 5 μm or more and 200 μm or less. By increasing the thickness of the bonding members 4, the bonding property of the bonding members 4 is improved. Furthermore, by decreasing the thickness of the bonding members 4, the heat conduction from the ceramic substrate 3 to the metal substrate 2 can be performed more efficiently. That is, by setting the thickness of the bonding members 4 in the above range, both the bonding property and the thermal conductivity can be achieved.

[0052] The standard deviation of the thickness of the bonding members 4 between the sections 31 of the ceramic substrate 3 is preferably 10 μm or less, and more preferably 5 μm or less. By setting the standard deviation of the thickness of the bonding members 4 within the above range, the variation in thickness of the composite substrate 1a is reduced, and the reliability is improved.

[0053] The bonding members 4 in the grooves 32 of the ceramic substrate 3 are present so as to fill preferably 20% or more, more preferably 50% or more, even more preferably 70% or more, even more preferably 80% or more, and particularly preferably 90% or more of the thickness of the ceramic substrate 3, but may be 100%. By setting the filling amount of the bonding members 4 in the grooves 32 to the above range, the contact area between the bonding members 4 and the ceramic substrate 3 is increased, and the heat dissipation effect of the composite substrate 1a is improved. The bonding members 4 are present at 100% of the thickness of the ceramic substrate 3, meaning that the bonding members 4 are completely filled in both the broken grooves and the grooves that were originally formed, and the surfaces of the bonding members 4 and the ceramic substrate 3 are flush. When the surfaces of the bonding members 4 and the ceramic substrate 3 are flush, it is preferable to press the ceramic substrate 3 so that a flat object comes into contact with the surface of the ceramic substrate 3. Alternatively, it is preferable to polish or grind the surface of the ceramic substrate 3 after the metal substrate 2 and the ceramic substrate 3 are bonded.

[0054] The porosity, thickness, and standard deviation of the thickness in the bonding member 4 can be obtained by cutting the composite substrate 1a in the thickness direction and observing the cross section with a scanning electron microscope (SEM) or the like. The cut portion is typically a portion passing through the center of the section 31 in a plan view. For example, when the section 31 is rectangular, the section is cut at a portion connecting the midpoints of the two opposing sides in a plan view. The porosity can be calculated by calculating the ratio of the void portion in the bonding member 4 under the section 31. Alternatively, it can be calculated from the area of ​​the void occurrence portion in X-ray observation or ultrasonic microscope observation from the substrate surface layer. For example, it can be measured by X-ray CT. The thickness is the thickness of the thickest part under the section 31 in the above cross section. The standard deviation of the thickness can be calculated by measuring the thickness under each section 31 observed in the above cross section and calculating the standard deviation of the thickness.

[0055] Second embodiment A composite substrate 1b according to a second embodiment and a manufacturing method thereof will be described with reference to Fig. 3A and Fig. 3B. Fig. 3A corresponds to Fig. 2C according to the first embodiment. Fig. 3B is a schematic cross-sectional view showing a cross section of the composite substrate 1b according to the second embodiment.

[0056] The manufacturing method of the composite substrate 1b differs from the manufacturing method of the composite substrate 1a according to the first embodiment in that, in (c) disposing the ceramic substrate 3 on the bonding material 4a, the ceramic substrate 3 is disposed on the bonding material 4a so that the surface having the grooves 32 faces the bonding material 4a. That is, in the manufacturing method of the composite substrate 1b, the ceramic substrate 3 is disposed so that the second surface 34 faces the bonding material 4a.

[0057] In the manufacturing method of the composite substrate 1b according to the second embodiment, the ceramic substrate 3 is placed on the bonding material 4a so that the surface having the grooves 32 faces the bonding material 4a, so that the bonding material 4a can easily enter the grooves 32 and the bonding members 4 can be easily placed in the grooves 32. In addition, the second surface 34 of the ceramic substrate 3 that does not have the grooves 32 becomes the surface of the composite substrate 1b, so that unevenness on the surface of the ceramic substrate 3 can be reduced or eliminated.

[0058] In the composite substrate 1b, the bonding members 4 in the grooves 32 of the ceramic substrate 3 preferably occupy 90% or more, more preferably 95% or more, and even more preferably 100% of the thickness of the ceramic substrate 3. The bonding members 4 occupy 100% of the thickness of the ceramic substrate 3 means that the bonding members 4 are completely filled in the cracked grooves, and the surfaces of the bonding members 4 and the ceramic substrate 3 are flush with each other. When the surfaces of the bonding members 4 and the ceramic substrate 3 are flush with each other, it is preferable to press the ceramic substrate 3 so that a flat object comes into contact with the surface of the ceramic substrate 3. Alternatively, it is preferable to polish or grind the surface of the ceramic substrate 3 after bonding the metal substrate 2 and the ceramic substrate 3.

[0059] Third embodiment A composite substrate 1c according to a third embodiment and a manufacturing method thereof will be described with reference to Fig. 4A and Fig. 4B. Fig. 4A corresponds to Fig. 2C according to the first embodiment. Fig. 4B is a schematic cross-sectional view showing a cross section of the composite substrate 1c according to the third embodiment.

[0060] The composite substrate 1c according to the third embodiment differs from the composite substrate 1a according to the first embodiment in that it has a ceramic substrate 3a and another ceramic substrate 3b on both sides, the first surface 21 and the second surface 22, of the metal substrate 2, respectively.

[0061] The manufacturing method of the composite substrate 1c differs from that of the composite substrate 1a according to the first embodiment in that (b) in arranging the bonding material 4a, bonding material 4a1 is arranged on the first surface 21 of the metal substrate 2 and bonding material 4a2 is arranged on the second surface 22, and (c) in arranging the ceramic substrates, ceramic substrate 3a is arranged on bonding material 4a1 and ceramic substrate 3b is arranged on bonding material 4a2.

[0062] In the illustrated example, the ceramic substrates 3a and 3b are arranged so that the surface opposite to the surface having the groove 32 faces the bonding material 4a1 or 4a2, but as in the second embodiment, the surface having the groove 32 may be arranged so that it faces the bonding material 4a1 or 4a2.

[0063] Embodiments of the present disclosure include the following: [Section 1] a metal substrate having a first surface and a second surface opposite to the first surface; A ceramic substrate; a bonding member disposed on the first surface and bonding the metal substrate and the ceramic substrate together; The ceramic substrate has a plurality of sections, and a groove is provided between adjacent sections; A composite substrate, wherein the joining member is present in the groove. [Section 2] Item 2. The composite substrate according to item 1, wherein the grooves are arranged in a lattice pattern in a plan view. [Section 3] 3. The composite substrate according to item 2, wherein the sections of the ceramic substrate are rectangular with one side measuring 30 mm or less in plan view. [Section 4] 4. The composite substrate according to any one of items 1 to 3, wherein the ceramic substrate has a thickness of 50 μm or more and 500 μm or less. [Section 5] Item 5. The composite substrate according to any one of items 1 to 4, wherein the metal substrate has a thickness of 200 μm or more and 2.0 mm or less. [Section 6] 6. The composite substrate according to any one of items 1 to 5, wherein the bonding member has a thickness of 5 μm or more and 200 μm or less. [Section 7] 7. The composite substrate according to any one of items 1 to 6, wherein the standard deviation of the thickness of the bonding member between a plurality of sections of the ceramic substrate is 5 μm or less. [Section 8] 8. The composite substrate according to any one of items 1 to 7, wherein the bonding members below the sections of the ceramic substrate have a porosity of 1% or less. [Section 9] Item 9. The composite substrate according to any one of items 1 to 8, wherein the amount of warping is 300 μm or less. [Section 10] Item 10. The composite substrate according to any one of items 1 to 9, wherein the ceramic substrate is a nitride-based ceramic substrate. [Section 11] Item 11. The composite substrate according to any one of items 1 to 10, wherein the metal substrate contains at least one of Cu and Al. [Section 12] Item 12. The composite substrate according to any one of items 1 to 11, wherein the bonding members contain at least one of Ag and Cu. [Section 13] Item 13. The composite substrate according to any one of items 1 to 12, further comprising a bonding member and a ceramic substrate disposed on the second surface of the metal substrate. [Section 14] providing a metal substrate having a first surface and a second surface opposite to the first surface, a ceramic substrate having a groove, and a bonding material; disposing the bonding material on the first surface; placing the ceramic substrate on the bonding material such that a surface opposite to a surface having the groove or a surface having the groove faces the bonding material; heating the bonding material to form a bonding member while pressing at least one of the ceramic substrate and the metal substrate toward the other, thereby bonding the ceramic substrate and the metal substrate; Including, In bonding the ceramic substrate and the metal substrate, the ceramic substrate is at least partially cracked along the groove, and the bonding member is disposed in the cracked groove. A method for manufacturing a composite substrate. [Section 15] Item 15. The manufacturing method according to item 14, wherein the heating temperature in bonding the ceramic substrate and the metal substrate is 780° C. or more and 1100° C. or less. [Section 16] Item 15. The manufacturing method according to item 14, wherein the heating temperature in joining the ceramic substrate and the metal substrate is 150° C. or more and 300° C. or less. [Section 17] Item 17. The method according to any one of items 14 to 16, wherein in bonding the ceramic substrate and the metal substrate, the pressure applied is 0.1 MPa or more and 10 MPa or less. [Section 18] Item 18. The method according to any one of items 14 to 17, wherein the ceramic substrate and the metal substrate are pressed together via a cushioning material. [Section 19] Item 19. The method according to any one of items 14 to 18, wherein in the preparing, the ceramic substrate has a thickness of 50 μm or more and 500 μm or less, and the groove has a depth of 1 / 5 or more and 4 / 5 or less of the thickness of the ceramic substrate. [Explanation of symbols]

[0064] 1a... Composite substrate (first embodiment), 1b... Composite substrate (second embodiment) 1c... composite substrate (third embodiment), 2... metal substrate, 3... ceramic substrate 4... bonding member, 4a... bonding material, 21... first surface of metal substrate, 22... second surface of metal substrate 31: compartment; 32: groove; 33: first surface of ceramic substrate; 34: second surface of ceramic substrate

Claims

1. a metal substrate having a first surface and a second surface opposite to the first surface; A ceramic substrate; a bonding member disposed on the first surface and bonding the metal substrate and the ceramic substrate together; The ceramic substrate has a plurality of sections, and a groove is provided between adjacent sections; A composite substrate, wherein the joining member is present in the groove.

2. The composite substrate according to claim 1 , wherein the grooves are arranged in a lattice pattern in a plan view.

3. The composite substrate according to claim 2 , wherein the sections of the ceramic substrate are rectangular in shape with each side measuring 30 mm or less in plan view.

4. 2. The composite substrate according to claim 1, wherein the ceramic substrate has a thickness of 50 μm or more and 500 μm or less.

5. 2. The composite substrate according to claim 1, wherein the metal substrate has a thickness of 200 μm or more and 2.0 mm or less.

6. The composite substrate according to claim 1 , wherein the thickness of the bonding member is not less than 5 μm and not more than 200 μm.

7. The composite substrate according to claim 1 , wherein a standard deviation of the thickness of the bonding member among the plurality of sections of the ceramic substrate is 5 μm or less.

8. The composite substrate according to claim 1 , wherein the porosity of the bonding member under the section of the ceramic substrate is 1% or less.

9. 2. The composite substrate according to claim 1, wherein the amount of warping is 300 μm or less.

10. The composite substrate according to claim 1 , wherein the ceramic substrate is a nitride-based ceramic substrate.

11. The composite substrate according to claim 1 , wherein the metal substrate comprises at least one of Cu and Al.

12. The composite substrate according to claim 1 , wherein the bonding member contains at least one of Ag and Cu.

13. The composite substrate according to claim 1 , further comprising a bonding member and a ceramic substrate disposed on the second surface of the metal substrate.

14. Providing a metal substrate having a first surface and a second surface opposite the first surface, a ceramic substrate having a groove, and a bonding material; disposing the bonding material on the first surface; placing the ceramic substrate on the bonding material such that a surface opposite to a surface having the groove or a surface having the groove faces the bonding material; heating the bonding material to form a bonding member while pressing at least one of the ceramic substrate and the metal substrate toward the other, thereby bonding the ceramic substrate and the metal substrate; Including, In bonding the ceramic substrate and the metal substrate, the ceramic substrate is at least partially cracked along the groove, and the bonding member is disposed in the cracked groove. A method for manufacturing a composite substrate.

15. The method according to claim 14 , wherein the heating temperature in bonding the ceramic substrate and the metal substrate is 780° C. or more and 1100° C. or less.

16. The method according to claim 14, wherein the heating temperature in bonding the ceramic substrate and the metal substrate is 150° C. or more and 300° C. or less.

17. The method according to claim 14 , wherein the magnitude of the pressure applied when bonding the ceramic substrate and the metal substrate is not less than 0.1 MPa and not more than 10 MPa.

18. The method according to claim 14 , wherein the ceramic substrate and the metal substrate are pressed together via a cushioning material in joining the ceramic substrate and the metal substrate.

19. The method according to claim 14, wherein in the preparing, the ceramic substrate has a thickness of 50 μm or more and 500 μm or less, and the depth of the groove is ⅕ or more and ⅓ or less of the thickness of the ceramic substrate.

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