JP2019145740A - Heat radiation substrate - Google Patents

Abstract

To provide a heat radiation substrate which achieves excellent heat cycle resistance characteristics in a wide temperature range even when including a heat radiation copper plate having a relatively large thickness.SOLUTION: A heat radiation substrate 1 disposed in here includes: a ceramic substrate 2; a copper plate 6; and an intermediate layer 4 which integrally joins the ceramic substrate 2 to the copper plate 6. The intermediate layer 4 includes a lamination structure including a first intermediate layer 41 which is mainly composed of copper and does not include a glass component, a second intermediate layer 42 mainly composed of copper and including the glass component, and a third intermediate layer 43 mainly composed of silver from a side which contacts with the ceramic substrate 2.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a heat dissipating substrate suitable for dissipating heat generated in a base material and use thereof.

  Power semiconductor elements (so-called power devices) are indispensable for the efficient use of electric energy. There is also an increasing demand for semiconductor elements for illumination (so-called high power LED devices) used in power-saving, long-life, high-luminance, power LED lamps and the like. Along with such rapid progress of semiconductor technology, power devices are rapidly increasing in current and withstand voltage.

The power device can generate more heat as it controls more power. Also, power devices can be designed in the form of a power module that includes one or more devices in a single package, or in the form of an intelligent power module that includes a control circuit, drive circuit, protection circuit, etc. Yes. Therefore, silicon carbide (SiC), silicon nitride (Si ₃ N ₄ ), etc. with low power loss are used in place of conventional silicon substrates for devices that require a particularly large calorific value and high reliability. Replacement with an insulating substrate having high heat resistance is in progress. These SiC and / or Si ₃ N ₄ substrates are advantageous in that they can be operated at a higher temperature than the silicon substrate and can be switched at a high speed. In order to improve the heat dissipation of these insulating substrates, a heat dissipation sheet (heat dissipation mechanism) made of copper having high thermal conductivity is joined to the substrate surface opposite to the side on which the semiconductor element is mounted. A configuration in which the heat of the substrate is released to the outside through a heat dissipation mechanism is suitably employed. For example, Patent Documents 1 to 6 include conventional techniques for improving the heat dissipation of such an insulating substrate.

JP 2011-014924 A Japanese Patent Laid-Open No. 11-079872 JP 08-059375 A JP 2006-089290 A International Publication No. 2008/081758 Japanese Patent Laying-Open No. 2015-115521

  On the other hand, an inverter element or the like for driving a hybrid vehicle or a rail vehicle is assumed to be used in an environment exceeding 200 ° C. For this reason, power devices and power modules are required to have higher heat dissipation and heat resistance than before. For example, while the heat cycle resistance that has been conventionally required is approximately -20 ° C to 150 ° C, recently, for example, the heat cycle resistance in a wider and higher temperature range of, for example, -40 ° C to 250 ° C. It is being sought.

  For this reason, a thicker metal plate is used instead of a thin metal foil or metal thin plate as in the conventional metallized substrate for the heat dissipation mechanism that releases heat from the insulating substrate. Here, if the heat dissipation mechanism is a thin plate, thermal stress can be released by bending the metal thin plate to some extent. However, when a thick metal plate is used as the heat dissipation mechanism, the metal thick plate is difficult to bend, and thus a new problem has arisen in that the thermal stress at the bonding interface between the insulating substrate and the thick metal plate is increased. In particular, the above-described copper has a higher thermal expansion coefficient, so that the thermal stress is further increased. As a result, when the insulating substrate is exposed to a wide temperature change from the low temperature range to the high temperature range as described above, the insulating substrate and the heat sink are peeled off due to thermal stress, or the insulating substrate expands to the thick metal plate. There was a problem that it could not follow and was damaged. Therefore, there is a demand for an insulating substrate that can be prevented from being damaged due to thermal stress during high loads and can stably maintain a smooth heat dissipation over a long period of time.

  The present invention has been made in view of the circumstances as described above, and has heat cycle resistance characteristics over a wide temperature range even when a relatively thick (for example, 0.5 mm or more) heat dissipation copper plate is provided. It is an object to provide an excellent heat dissipation substrate.

  In order to solve the above problems, the present invention provides a heat dissipating substrate comprising a ceramic substrate, a copper plate, and an intermediate layer that integrally bonds the ceramic substrate and the copper plate. The intermediate layer includes, from the side in contact with the ceramic substrate, a first intermediate layer containing copper as a main component and not containing a glass component, a second intermediate layer containing copper as a main component and containing a glass component, and silver as a main component. And a third intermediate layer.

  In the above configuration, the first intermediate layer in contact with the ceramic substrate and the third intermediate layer in contact with the copper plate are each composed of layers mainly composed of copper and silver. Thus, it is possible to suitably ensure the adhesion of the intermediate layer to each of the ceramic substrate having a small thermal expansion coefficient and the copper plate having a large thermal expansion coefficient. And according to the said structure, the 2nd intermediate | middle layer containing the glass component which can relieve | moderate a thermal stress suitably and can provide a softness | flexibility can be provided between these 1st intermediate | middle layers and 3rd intermediate | middle layers. As a result, for example, a heat dissipating substrate in which separation from the ceramic substrate and the copper plate is suppressed even with respect to a heat cycle in a wider range of about −40 ° C. to 250 ° C. is realized.

  In the present specification, the “main component” refers to a component having the highest content among components constituting a target member (for example, each intermediate layer). Unless otherwise specified, the main component is typically 50% by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more, particularly preferably 80% by mass or more, for example 90% by mass or more. Means ingredients contained in proportions.

  In a preferred embodiment of the heat dissipation substrate disclosed herein, the copper plate has a thickness of 500 μm or more. Thereby, the heat dissipation board | substrate provided with higher heat dissipation is realizable.

  In a preferred aspect of the heat dissipation substrate disclosed herein, the thickness of the first intermediate layer is not less than 0.5 μm and not more than 10 μm. Thereby, even if the thickness of the 1st intermediate | middle layer which consists of copper is made thin or a ratio is decreased, the heat dissipation board excellent in heat dissipation is provided.

  In a preferred aspect of the heat dissipation substrate disclosed herein, the thickness of the second intermediate layer is 50 μm or more and 500 μm or less. Thereby, even if it is a case where a 1 mm thick copper plate is joined, for example, the heat dissipation board | substrate provided with the high heat cycle characteristic is realizable.

In a preferred aspect of the heat dissipation substrate disclosed herein, the second intermediate layer has a thermal expansion coefficient of 11 × 10 ⁻⁶ / K or more and 14 × 10 ⁻⁶ / K or less at 25 ° C. to 500 ° C. . Thereby, even if it is a case where a thick copper plate is joined, the thermal stress which generate | occur | produces in a heat dissipation board | substrate in a heat cycle environment can be absorbed suitably. As a result, the ceramic substrate can be suitably prevented from being damaged or peeled off from the copper plate.

  In this specification, “Coefficient of Thermal Expansion (CTE)” refers to a thermomechanical analysis (TMA) from room temperature (25 ° C.) to 500 ° C. unless otherwise specified. Means the average linear expansion coefficient measured in the temperature range up to, and means a value obtained by dividing the change in the length of the sample in the temperature range by the measured temperature difference. This thermal expansion coefficient can be measured according to the method for measuring the linear expansion coefficient of a metal material defined in JIS Z2285: 2003. Hereinafter, the “thermal expansion coefficient” may be simply expressed as “CTE”.

  In a preferred aspect of the heat dissipation substrate disclosed herein, the third intermediate layer has a thickness of 3 μm or more and 25 μm or less. Thereby, use of an expensive silver layer can be suppressed and a heat dissipation board provided with heat cycle tolerance over a wide temperature range can be provided.

  In a preferred aspect of the heat dissipation substrate disclosed herein, the third intermediate layer is a sintered layer formed by sintering silver nanoparticles having an average particle diameter of 20 nm or more and 60 nm or less. Thereby, the heat conductivity of an intermediate | middle layer can be improved suitably and the heat dissipation of a heat dissipation board | substrate can be improved.

In a preferred aspect of the heat dissipation substrate disclosed herein, the glass component is configured to have a softening point of 250 ° C. or higher and 450 ° C. or lower. With such a configuration, it is possible to enhance the effect of relaxing the thermal stress of the heat dissipation substrate.
Further, in the present specification, the “softening point” relating to the glass component is defined as a temperature at which almost no molding operation of the glass is possible at a temperature lower than this. In other words, it can be grasped as the temperature at which the glass begins to significantly soften and deform under its own weight. This softening point can be measured according to JIS R3103-1: 2001, and can be, for example, a temperature corresponding to a viscosity of about 10 ^7.6 dPa · s.

  In a preferred aspect of the heat dissipation substrate disclosed herein, the ceramic substrate is mainly composed of at least one ceramic selected from the group consisting of silicon carbide, silicon nitride, and aluminum nitride. The heat dissipation board | substrate of any one of these. With such a configuration, a heat dissipating substrate suitable for a power device capable of high withstand voltage, low loss, and high frequency / high temperature operation is provided.

  In another aspect, the technology disclosed herein provides a method for manufacturing a heat dissipation substrate. In this manufacturing method, a first intermediate layer mainly comprising copper and not containing a glass component is provided on a ceramic substrate, and a copper paste containing copper powder, glass powder and a dispersion medium is provided on the first intermediate layer. Forming a copper paste layer by supplying, supplying a silver paste containing silver powder and a dispersion medium on the copper paste layer to provide a silver paste layer, and placing a copper plate on the silver paste layer Preparing an unsintered laminate, and firing the unsintered laminate in a temperature range of 500 ° C. to 700 ° C. to obtain a heat dissipation substrate. Thereby, said heat dissipation board | substrate can be provided simply. Moreover, paste baking and joining of a copper plate can be implemented simultaneously. Furthermore, it is possible to easily produce intermediate layers having various configurations by applying printing technology.

  According to the above-described technology disclosed herein, a heat radiating substrate having low resistivity and heat cycle resistance (heat resistance, thermal stress relaxation, bonding properties, etc.) in a wider temperature range and its manufacture A method is provided. According to such a technique, in the intermediate layer, the second intermediate layer and the third intermediate layer can be manufactured by, for example, paste printing. Therefore, the second intermediate layer and the third intermediate layer can be combined with various shapes. As a result, it is possible to realize more reliable bondability in a wide temperature range and relieve thermal stress due to a larger temperature change. Moreover, this intermediate | middle layer can be manufactured, adjusting thickness and a structure simply. Thereby, even if it is a case where a heat dissipation copper plate expand | swells or shrink | contracts greatly, generation | occurrence | production of the curvature and distortion of a ceramic substrate (insulating board | substrate) can be suppressed suitably.

It is a cross-sectional schematic diagram which shows the structure of the heat dissipation board | substrate which concerns on one Embodiment. It is a perspective view which shows typically the structure which used the 3rd intermediate | middle layer as the line pattern in the heat dissipation board | substrate which concerns on one Embodiment. It is a cross-sectional schematic diagram which shows the structural example of the power device using the heat dissipation board which concerns on one Embodiment. It is a cross-sectional schematic diagram which shows the structural example of the power device using the heat dissipation board | substrate which concerns on other embodiment.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings as appropriate. Note that matters other than the matters specifically mentioned in the present specification and necessary for the implementation of the present invention shall be implemented based on the contents disclosed in the present specification and common general technical knowledge in the field. Can do. Moreover, in the following drawings, the same code | symbol is attached | subjected and demonstrated to the member and site | part which show | plays the same effect | action, and the overlapping description may be abbreviate | omitted or simplified. The embodiments shown in the drawings are modeled as necessary to clearly explain the present invention, and do not necessarily accurately reflect the dimensional relationship (length, width, thickness, etc.) of the actual heat-dissipating substrate. It was n’t. Further, “X to Y” indicating a range means “X or more and Y or less” unless otherwise specified.

[Heat dissipation substrate]
The cross section which shows the structure of the thermal radiation board | substrate which concerns on one Embodiment was typically shown in FIG. The heat dissipating substrate 1 disclosed herein is configured by integrally bonding a ceramic substrate 2 and a copper plate 6 that promotes heat dissipation (heat generation and heat storage) of the ceramic substrate 2 by an intermediate layer 4. ing. The intermediate layer 4 includes a first intermediate layer 41, a second intermediate layer 42, and a third intermediate layer 43 from the side in contact with the ceramic substrate 2. With the intermediate layer 4, the ceramic substrate 2 and the copper plate 6 are integrally bonded, and the difference in thermal expansion behavior between the two is preferably alleviated.

As the ceramic substrate 2, substrates made of various ceramics can be used. Typically, a substrate made of an insulating ceramic can be considered. Such a ceramic is not particularly limited in detail composition, shape, dimensions, etc., for example, a carbide-based ceramic composed of a metal carbide, a nitride-based ceramic composed of a metal nitride, an oxide-based composed of a metal oxide. Ceramics and other ceramics made of metal borides, fluorides, hydroxides, carbonates, phosphates and the like can be mentioned. Specific examples of such ceramics include silicon nitride (Si ₃ N ₄ ), aluminum nitride (AlN), boron nitride (BN), gallium nitride (GaN), sialon (Si ₃ N ₄ —AlN—Al ₂ O ₃ solid solution; Sialon), nitride ceramics such as carbon nitride (CN _x ), titanium nitride (TiN), carbide ceramics such as silicon carbide (SiC), tungsten carbide (WC), boron carbide (B ₄ C), alumina (Al ₂ O ₃ ), alumina / zirconia (Al ₂ O ₃ —ZrO ₂ ), zirconia (ZrO ₂ ), cordierite (2MgO · 2Al ₂ O ₃ · 5SiO ₂ ), mullite (3Al ₂ O ₃ · 2SiO ₂ ), etc. Typical examples thereof include oxide ceramics. These ceramics are described together with representative compositions, but are not necessarily limited to those strictly having the above composition. For example, for the purpose of obtaining desired characteristics, it may be added or compounded with various other elements.

As such a ceramic, even if the CTE is particularly small, it can be suitably used as a ceramic that can significantly exhibit the effects of the present invention. From such a viewpoint, for example, a ceramic substrate 2 made of a nitride ceramic (typically silicon nitride or aluminum nitride) or silicon carbide can be suitably used.
In particular, silicon carbide has excellent physical properties such as an electric field strength of about 10 times, a maximum electron travel speed of about 2 times, and a thermal conductivity of about 3 times of silicon (Si). For example, it can be preferably used as a substrate for power device applications. In addition, silicon nitride has a particularly high strength compared to other ceramics (for example, about 700 to 830 MPa in bending strength), and thus can be a particularly preferable material for a substrate, for example, by reducing the thickness. Furthermore, aluminum nitride has a very high thermal conductivity (for example, 150 to 200 W / m · K) compared to other ceramic materials, and thus may be a preferable material for constituting a substrate. The size of these substrates is not particularly limited, and can be, for example, a dimension according to a desired standard.

  The thickness in particular of the ceramic substrate 2 is not restrict | limited, Typically, thickness can be 3 mm or less, for example. In addition, when the ceramic substrate 2 is an aluminum nitride substrate, the thickness can be 2.5 mm or less, for example, can be 2 mm or less, and can be 1.5 mm or less. The thickness of the aluminum nitride substrate can be 0.1 mm or more, can be 0.2 mm or more, and can be 0.4 mm or more (for example, 0.635 mm). On the other hand, when the ceramic substrate 2 is a silicon nitride substrate, the thickness can be, for example, 2 mm or less, can be 1.5 mm or less, and can be 1 mm or less. The thickness of the silicon nitride substrate can be 0.1 mm or more, can be 0.2 mm or more, and can be 0.3 mm or more, for example. For example, the thickness of the silicon nitride substrate may be 0.32 mm, 0.635 mm, or the like.

  As the copper plate 6, a film, a foil, a sheet, a plate-like body and the like mainly composed of copper (Cu) can be considered. Copper is known to have a thermal conductivity as a single metal of about 386 to 402 W / mK, which is the second highest after silver (Ag), and the higher the thermal conductivity, the more preferable the material for the heat dissipation member of the heat dissipation substrate. obtain. Here, the copper plate is not particularly limited as long as it contains copper as a main component (50% by mass or more). For example, it may be various copper and copper alloys defined in JIS H3100: 2012. The thermal conductivity of the copper plate is, for example, preferably 250 W / mK or more, more preferably 300 W / mK or more, further preferably 320 W / mK or more, particularly preferably 340 W / mK or more, and 360 W / mK or more (for example, 380 W / mK or more). ) Is even more preferable. Such thermal conductivity can be realized by, for example, oxygen-free copper, tough pitch copper, phosphorus deoxidized copper, phosphorus-containing tough pitch alternative copper (PTC), red brass, brass or the like.

  Moreover, according to the technique disclosed here, even when the copper plate 6 is thickened, the heat cycle resistance of the heat-radiating substrate 1 can be well maintained at a high level. Therefore, for example, the copper plate 6 having an average thickness of 0.5 mm or more (for example, exceeding 0.5 mm) can be suitably used from the viewpoint of realizing higher heat dissipation. For example, the copper plate 6 may have an average thickness of 0.6 mm or more, preferably 0.7 mm or more, more preferably 0.8 mm or more, particularly preferably 0.9 mm or more, and further preferably 1.0 mm or more. Thereby, the heat dissipation board | substrate with high heat dissipation is provided so far. Although the upper limit in particular of the average thickness of the copper plate 6 is not restrict | limited, For example, it can be set as about 3 mm or less.

  The thickness balance between the ceramic substrate 2 and the copper plate 6 is not particularly limited. In the technique disclosed herein, the intermediate layer 4 can moderate the difference in CTE between the ceramic substrate 2 and the copper plate 6 as described later. Therefore, the ratio of the thickness of the copper plate 6 to the ceramic substrate 2 can be, for example, about 0.5 or more and 10 or less. The ratio of the thickness of the copper plate 6 to the ceramic substrate 2 is preferably 1 or more, more preferably 2 or more, still more preferably 5 or more, and particularly preferably 7 or more (for example, about 7.8).

The CTE of the above silicon nitride is about 2.8 × 10 ⁻⁶ / K, the CTE of silicon carbide is about 3.7 × 10 ⁻⁶ / K, and the CTE of aluminum nitride is about 4.6 × 10 ⁻⁶ / K. Boron nitride CTE is about 1.4 × 10 ⁻⁶ / K, cordierite CTE is about 0.1 × 10 ⁻⁶ / K or less, and mullite CTE is about 5.0 × 10 ^−6. / K and can be a relatively small value. On the other hand, the copper plate, without being greatly affected by the composition, CTE can be a relatively high value of about 16.5 × ^{10 -6} /K~17.8×10 -6 / K approximately. Therefore, the difference in CTE between the copper plate and the ceramic substrate may be approximately ^{12 × 10 -6 / K~14 × 10} -6 / K approximately. Here, when the ceramic substrate and the copper plate are bonded together (joined), the difference in CTE is about 0.3 to 0.00 in the temperature range of, for example, −40 ° C. to 250 ° C. (temperature difference 290 ° C.). A strain of 4% (in other words thermal stress) can occur. This strain could be absorbed by warping deformation of the copper plate and / or the ceramic substrate when the copper plate was thin (for example, about 0.3 mm or less). However, when the thickness of the copper plate is increased (for example, 0.5 mm or more as described above), the copper plate is less likely to warp and deform and cannot be absorbed in the copper plate. As a result, conventionally, a shearing force acts on the ceramic substrate based on the thermal expansion of the copper plate, causing problems such as breakage of the ceramic substrate. Or the problem that a ceramic substrate and a copper plate peeled has arisen. For example, when the copper plate and the ceramic substrate are joined with a copper paste containing glass frit, the bondability between the copper paste and the ceramic substrate is good, but the bondability between the copper paste and the copper plate is sufficiently obtained. The ceramic substrate sometimes peeled off from the copper plate.

  Therefore, in the technique disclosed herein, as described above, the copper plate 6 and the ceramic substrate 2 are joined by the intermediate layer 4 including the first intermediate layer 41, the second intermediate layer 42, and the third intermediate layer 43. . The first intermediate layer 41 is mainly provided to improve the bonding property between the ceramic substrate 2 and the second intermediate layer 42. The second intermediate layer 42 is provided mainly for sufficiently relaxing the thermal stress generated between the copper plate 6 and the ceramic substrate 2. The third intermediate layer 43 is provided mainly for improving the bonding property between the copper plate 6 and the second intermediate layer 42 and maintaining high thermal conductivity in the intermediate layer 4.

  The first intermediate layer 41 includes copper as a main component and does not include a glass component. The first intermediate layer 41 plays a role of supporting the adhesion between the ceramic substrate 2 and the second intermediate layer 42. As will be described later, the second intermediate layer 42 includes a glass component, and this glass component generally has a function as an inorganic adhesive. However, when considering bonding with the ceramic substrate 2, for example, the first intermediate layer 41 that does not include a glass component and has a metal structure can achieve higher bonding. In addition, since both the first intermediate layer 41 and the second intermediate layer 42 are mainly made of copper, the bondability between the first intermediate layer 41 and the second intermediate layer 42 can be improved. As a result, the first intermediate layer 41 can more firmly integrate the ceramic substrate 2 with low bondability and the second intermediate layer 42 with low adhesive compatibility with the ceramic substrate 2. Copper as the main component of the first intermediate layer 41 may be copper (Cu) alone, or may be an alloy containing other arbitrary elements in Cu, for example. When copper is an alloy, it is not particularly limited as an alloy element that forms such an alloy with copper. For example, Al, Ag, As, Be, Co, Cr, Fe, Mn, Ni, P, Pb, S, Se , Sd, Sn, Si, Te, Zn, Zr and the like. From the viewpoint that the heat dissipating substrate preferably has high thermal conductivity, the copper in the first intermediate layer 41 is also preferably close to pure copper having high thermal conductivity. For example, in the first intermediate layer 41, Cu is preferably 90% by mass or more, more preferably 95% by mass or more, and particularly preferably 97% by mass or more. The first intermediate layer 41 is preferably formed on the surface of the ceramic substrate 2 with good adhesion. Accordingly, the first intermediate layer 41 is preferably a layer that is densely formed at the atomic level by, for example, a CVD method, a PVD method, or a plating method. From the viewpoint of ease of manufacture, the first intermediate layer 41 is particularly preferably a copper plating layer formed by, for example, a plating method.

  Since the first intermediate layer 41 is mainly made of copper, the CTE of the first intermediate layer 41 can be substantially equal to the CTE of copper. Therefore, in order to suppress the thermal stress based on the CTE difference with the ceramic substrate 2 having a small CTE, it is appropriate that the first intermediate layer 41 has an average thickness of 10 μm or less, preferably 5 μm or less, more preferably 3 μm or less. 2 μm or less is particularly preferable. Thereby, it can suppress that the thermal stress based on relatively large CTE of the 1st intermediate | middle layer 41 acts on the ceramic substrate 2, and even when it is a case where it is a case where it is exposed to a big temperature change, a heat cycle characteristic is It is suitably maintained. In addition, from the viewpoint of firmly bonding the ceramic substrate 2 and the second intermediate layer 42, the first intermediate layer 41 is appropriately set to have an average thickness of 0.01 μm or more, preferably 0.05 μm or more, More preferably, it is 0.1 μm or more, for example, 0.4 μm or more. Thereby, the ceramic substrate 2 and the 2nd intermediate | middle layer 42 can be joined more stably, and the thermal radiation board | substrate 1 with high thermal stability is realizable.

  On the other hand, the third intermediate layer 43 is mainly composed of silver. The third intermediate layer 43 does not contain a glass component. The third intermediate layer 43 also plays a role of supporting adhesion between the copper plate 6 and the second intermediate layer 42. In addition, since the 2nd intermediate | middle layer 42 contains a glass component, it tends to become low about the heat conductivity, and there exists a tendency for the heat dissipation as the intermediate | middle layer 4, and the heat dissipation board | substrate 1 whole to be inferior. . On the other hand, silver has the highest thermal conductivity among metals. Therefore, by providing the third intermediate layer 43 mainly composed of silver on the side in contact with the copper plate 6 of the intermediate layer 4, the thermal conductivity of the intermediate layer 4 is kept high. The silver as the main component of the third intermediate layer 43 may be silver (Ag) alone, or may be an alloy containing other arbitrary elements in Ag, for example. When silver is an alloy, it is not particularly limited as an alloying element that forms such an alloy with silver, and examples thereof include Cu, W, Re, Os, Ir, Pt, Au, In, Sn, Te, Zn, and Al. Illustrated. From the viewpoint that the heat dissipating substrate 1 preferably has high thermal conductivity, the silver in the third intermediate layer 43 is also preferably close to pure silver having high thermal conductivity. For example, in the third intermediate layer 43, Ag is preferably 90% by mass or more, more preferably 95% by mass or more, and particularly preferably 97% by mass or more.

Since the third intermediate layer 43 which is composed mainly of silver, generally it becomes equal to about ^{18 × 10 -6 / K~19 × 10} -6 / K approximately the CTE of even silver third intermediate layer 43, the copper plate It can be higher than the CTE of 6. Therefore, in order to suppress excessive thermal stress from acting on the second intermediate layer 42 close to the ceramic substrate 2 having a small CTE, the third intermediate layer 43 may have an average thickness of 30 μm or less, more preferably less than 30 μm. Is appropriate. The average thickness of the third intermediate layer 43 is preferably 25 μm or less, more preferably 20 μm or less, and particularly preferably 15 μm or less. Thereby, CTE as the intermediate | middle layer 4 whole can be stabilized, and generation | occurrence | production of an excessive thermal stress can be suppressed. In addition, from the viewpoint of firmly bonding the copper plate 6 and the second intermediate layer 42, the third intermediate layer 43 is appropriately set to have an average thickness of 0.01 μm or more, preferably 0.05 μm or more, and 0 More preferably, it is 1 μm or more, for example, 0.4 μm or more. Thereby, the copper plate 6 and the 2nd intermediate | middle layer 42 can be joined more stably, and the thermal radiation board | substrate 1 with high thermal stability is realizable.

  The second intermediate layer 42 includes copper as a main component and a glass component. The glass component may have a CTE that is generally higher than the ceramic substrate 2 and lower than the copper plate 6. Thereby, for example, the CTE of the second intermediate layer 42 at room temperature can be adjusted between the ceramic substrate 2 and the copper plate 6. The glass component in the second intermediate layer 42 softens from a relatively low temperature during the heat cycle, wets and spreads on the surface of the copper component, and allows its displacement while bonding the copper component. The second intermediate layer 42 follows the deformation of the first intermediate layer 41 on the side bonded to the first intermediate layer 41, and the third intermediate layer 43 on the side bonded to the third intermediate layer 43. Can follow the deformation of At this time, the second intermediate layer 42 can maintain its layer form by allowing its own deformation without causing damage such as breakage or cutting of the layer. In other words, the glass component typically functions as a glass matrix (glass component) that arbitrarily connects the particulate copper component. Thereby, even if it is a case where it is a case where it exposes to a heat cycle with a wide temperature range, the heat dissipation board | substrate 1 with which peeling of the copper plate 6, the damage of the ceramic substrate 2, etc. were suppressed is implement | achieved.

  Here, typically, the glass component preferably has a softening point of 500 ° C. or less. When the softening point of the glass component is 500 ° C. or less, for example, as the environmental temperature becomes higher, the glass component gradually starts to soften, and the second intermediate layer 42 is made flexible while maintaining the bonding property of the copper component. be able to. The softening point of the glass component is preferably 450 ° C. or lower, more preferably 430 ° C. or lower, and particularly preferably 400 ° C. or lower. However, if the softening point of the glass component is too low, it is not preferable because crystals are precipitated in the glass component and are easily crystallized, or are easily affected by the heat cycle. From this viewpoint, the softening point of the glass component is preferably 250 ° C. or higher, more preferably 300 ° C. or higher, and particularly preferably 350 ° C. or higher.

The above glass component has a composition (hereinafter the same) when converted to an oxide, and preferably contains at least one of BaO and ZnO as a main glass component.
BaO is a network-modified oxide made of an alkaline earth metal and can contribute to the formation of glass in the presence of an appropriate amount of network-forming oxide. In the glass component disclosed here, BaO greatly contributes to lowering the softening point of the glass. Further, BaO preferably has an effect of suitably lowering the viscosity of the glass component during softening and melting, for example, to spread the glass component to every corner of the structure made of copper in the copper plate. BaO is known to be a component that increases the coefficient of thermal expansion in glass mainly composed of silicon (Si). However, in the glass component disclosed here, the thermal expansion coefficient of the glass can be greatly increased by using such BaO as a main component, and the thermal expansion coefficient of the second intermediate layer is set to the thermal expansion coefficient of the copper plate. It can be a characteristic configuration in that it can be suitably matched to.

  ZnO is an intermediate oxide that vitrifies together with other elements. In the glass component disclosed here, ZnO greatly contributes to lowering the softening point of the glass. Moreover, ZnO increases the stability of glass and widens the vitrification range. For example, ZnO has the effect of suppressing crystallization (devitrification) of glass components even when exposed to temperature changes up to about 250 ° C. or higher. Have.

When the glass component contains BaO and / or ZnO as the main glass component, the softening point of the glass layer can be sufficiently reduced. BaO and ZnO may contain only one or both of them. Although not particularly limited, the glass component preferably contains at least BaO, and when both the BaO and ZnO are contained, it is preferable that the glass component contains more BaO than ZnO. In addition, the sum total of BaO and ZnO can be 50 mol% as mentioned above in the oxide conversion composition of a glass component. Although not particularly limited, the total of BaO and ZnO is preferably 60 mol% or more, more preferably 65 mol% or more, and particularly preferably 70 mol% or more. The upper limit of the total amount of BaO and ZnO is not particularly limited as long as the glass component is a composition capable of forming glass, but can be 95 mol% or less as an approximate guide, and may be 90 mol% or less. It can be 85 mol% or less.
In addition, regarding a glass composition, a "main glass component" means a component with the highest ratio (content) among the glass structural components which comprise the said glass component in an oxide conversion composition. The main component means a substance that is typically contained in a proportion of 50 mol% or more, preferably 60 mol% or more, for example 70 mol% or more.

In order to realize a glass component having a low softening point, the following can be considered as components constituting glass components other than BaO and ZnO.
The glass component may be a network-forming oxide containing component such as _{SiO 2, B 2 O 3,} P 2 O 5, GeO 2, As 2 O 3. These components are preferable not only because they contribute to glass formation, but also because they can compensate for the effects of chemical stability and water resistance reduction caused by BaO and ZnO. Any 1 type may be sufficient as network formation oxide, and 2 or more types may be sufficient as it. However, from the viewpoint of the stability of the system, it is preferable that the network-forming oxide is any one kind. For example, the network-forming oxide is preferably SiO ₂ from the viewpoint of excellent chemical stability. The amount of the network-forming oxide contained in the glass component is preferably 3 mol% or more, more preferably 5 mol% or more, and particularly preferably 7 mol% or more. Since the excessive inclusion of the network-forming oxide prevents the melting point from being lowered, the network-forming oxide is preferably 30 mol% or less, more preferably 25 mol% or less, and particularly preferably 20 mol% or less. In particular, when the network forming oxide is SiO ₂ , the excessive SiO ₂ content is not preferable because the glass component is hardened and the thermal stress relaxation ability is reduced. From this viewpoint, SiO ₂ is preferably 30 mol% or less, more preferably 20 mol% or less, and particularly preferably 15 mol% or less.

Na ₂ O, K ₂ O and Li ₂ O are network modified oxides made of alkali metal oxides. In the glass component disclosed here, these alkali metal oxides have a function of penetrating into the three-dimensional glass network, lowering the melting point and softening point of the glass, and improving the fluidity of the glass. Therefore, it can contribute to softening the glass component from a lower temperature and imparting flexibility to the coolable copper plate. Moreover, there exists an effect which improves the adhesiveness of a copper component and a glass component, or reduces the insulation of a glass component. The amount of these alkali metal oxides contained in the glass component is preferably 2 mol% or more, more preferably 2.5 mol% or more, and particularly preferably 3 mol% or more. Since the excessive alkali metal oxide content leads to an increase in the chemical durability of the glass component and the thermal expansion coefficient, the alkali metal oxide is preferably 20 mol% or less, more preferably 15 mol% or less, and particularly preferably 13 mol% or less. preferable.

Ag ₂ O has a function of lowering the melting point and softening point of glass. Ag ₂ O does not have the effect of increasing the adhesiveness like the above alkali metal oxides, but lowers the softening point and melting point of the glass with a smaller amount than the alkali metal oxides, or increases the insulating properties of the glass components. It is preferable because an effect of lowering can be obtained. The content of Ag ₂ O is preferably 0.1 mol% or more, more preferably 0.5 mol% or more, and particularly preferably 1 mol% or more. Since containing excessive Ag ₂ O leads to an increase in thermal expansion coefficient, Ag ₂ O is preferably 10 mol% or less, more preferably 5 mol% or less, and particularly preferably 3 mol% or less.

Al ₂ O ₃ is an intermediate oxide that does not vitrify alone but vitrifies with other elements. Al ₂ O ₃ is known to form an aluminosilicate glass and the like by forming a glass network by sharing apex oxygen with an oxygen polyhedron of Si. In the technology disclosed herein, for example, Al ₂ O ₃ can be preferably included as a component that can form a stable glass network together with a network-forming oxide such as SiO ₂ . The content of Al ₂ O ₃ is preferably 0.1 mol% or more, more preferably 0.2 mol% or more, and particularly preferably 0.5 mol% or more. Further, in such a glass system, Al ₂ O ₃ is not preferable if the content exceeds 5 mol% because the softening property of the glass can be lowered. The content of Al ₂ O ₃ is preferably 4.5 mol% or less, and more preferably 4 mol% or less.

In addition, a glass component can contain the various glass structural component and additive component other than having illustrated above in the range which does not impair the objective of the technique disclosed here. For example, Mg, Ca, Sr, Rb, Sn, Ti, Fe, Co, Cs, Ga, In, Ni, S, Cu, Sr, Se, Mo, Y, La, Nd, Pr, Gd, Sm, Dy, One element selected from the group consisting of Eu, Ho, Yb, Lu, Ta, V, Fe, Hf, Cr, Cd, Sb, F, I, Mn, Pb, Bi, W, Te, Ce and Nb May be contained alone or in combination of two or more elements. However, the inclusion of unnecessary elements can impair the stability of the glass component. Therefore, in the technology disclosed herein, the components other than the BaO, ZnO, SiO ₂ , Na ₂ O, K ₂ O, Li ₂ O, Ag ₂ O, and Al ₂ O ₃ are 5 mol% or less in total, It is preferably 4 mol% or less, more preferably 3 mol% or less, particularly preferably 2 mol% or less, for example 1 mol% or less. Or it is good also as 0 mol% substantially except the component mixed unavoidable.

The above glass component is not necessarily limited to this, but for example, the following composition can be specifically exemplified as a preferred example.
(BaO + ZnO): 60 mol% or more and 95 mol% or less,
SiO ₂ : 1 mol% or more and 20 mol% or less,
Ag ₂ O: 0.5 mol% or more and 5 mol% or less,
R ₂ O: 1mol% or more 30 mol% or less, and Al ₂ O _3: 0mol% or more 5 mol% or less

The above (BaO + ZnO) means the sum of BaO and ZnO. R may be one or more elements selected from Group 1A in the Periodic Table of Elements, for example, specifically, lithium (Li), sodium (Na), potassium (K), Good. R ₂ O means the total of oxides of these 1A group elements. Moreover, a part of SiO ₂ can be replaced with B ₂ O ₃ , P ₂ O ₅ , GeO ₂ , As ₂ O ₃ .

  In the 2nd intermediate | middle layer 42, as long as copper as a main component is included, the ratio of copper and a glass component is not restrict | limited in particular. The thermal stress generated between the ceramic substrate 2 and the copper plate 6 when the second intermediate layer 42 is joined to the ceramic substrate 2 and a change in environmental temperature occurs due to the glass component being contained in a small amount. Can be relaxed. In order to make this effect clear, for example, when the total of copper and the glass component is 100% by mass, the glass component is preferably 10% by mass or more, and more preferably 12% by mass or more. More preferably, it is particularly preferably 15% by mass or more. In addition, the excessive glass component is not preferable because it leads to a decrease in the thermal conductivity of the second intermediate layer 42. From this viewpoint, the proportion of the glass component is preferably 30% by mass or less, more preferably 25% by mass or less, and particularly preferably 20% by mass or less.

In addition, since this glass component has a relatively small thermal expansion coefficient compared to copper, which is the main component of the second intermediate layer 42, the presence of this glass component also reduces the overall thermal expansion coefficient of the second intermediate layer 42. Can be done. Here, although the thermal expansion coefficient of the second intermediate layer 42 is not strictly limited, it is preferably 14 × 10 ⁻⁶ / K or less as a rough guide, and 12 × 10 ⁻⁶ / K or less. Is more preferable, and 10 × 10 ⁻⁶ / K or less is particularly preferable. The lower limit of the thermal expansion coefficient of the second intermediate layer 42 is not particularly limited, but can be, for example, 6 × 10 ⁻⁶ / K or more as an approximate guide.

  In the second intermediate layer 42, it is preferable that the copper (copper portion) and the glass component (glass component portion) are dispersed almost uniformly throughout the entire second intermediate layer 42. For example, the structure of the second intermediate layer 42 is preferably a composite composed of copper and a glass component. For example, it is preferable that copper is present in the second intermediate layer 42 as copper particles or as a result of sintering and integrating a plurality of copper particles. For example, the second intermediate layer 42 may have a composite structure by dispersing particulate copper in a matrix made of a glass component. Alternatively, the second intermediate layer 42 may have a composite structure in which a glass component occupies a porous portion (sponge shape) in which a plurality of particles are three-dimensionally bonded. In addition, a glass component can form (vitrify) a glass component in the state which contacted the copper component and the 1st intermediate | middle layer 41 and the 3rd intermediate | middle layer 43 in the normal temperature state. Thereby, for example, the relative density in the intermediate layer can be increased (for example, 95% or more). Note that the relative density here is a complement of the porosity.

  As the thickness of the second intermediate layer 42 increases, the thermal stress generated between the ceramic substrate 2 having a small CTE and the copper plate 6 having a large CTE can be sufficiently relaxed. From this point of view, it is appropriate that the second intermediate layer 42 has an average thickness of 1 μm or more, preferably 5 μm or more, more preferably 10 μm or more, for example, 50 μm or more. On the other hand, if the thickness of the second intermediate layer 42 is too thick, the thermal conductivity of the intermediate layer 4 is inferior, and the heat dissipation of the entire heat dissipation substrate 1 is impaired. From such a viewpoint, the second intermediate layer 42 is suitably 1000 μm or less, preferably 800 μm or less, more preferably 600 μm or less, and particularly preferably 500 μm or less. Thereby, the excessive fall of the heat dissipation of the heat dissipation board | substrate 1 can be suppressed.

In addition, it is preferable that the 1st intermediate | middle layer is solid-coated in the wide area | region of a board | substrate so that the required heat dissipation may be implement | achieved, for example. The first intermediate layer is preferably provided in a wide area of the substrate with, for example, a dimension sufficiently larger than the thickness (for example, 100 times to 10 × 10 ⁶ times the thickness). The form of the second intermediate layer and the third intermediate layer is not particularly limited. The second intermediate layer may be solid or may not be solid. And the 3rd intermediate layer is good to be formed in arbitrary patterns, for example so that desired conductivity may be realized. Examples of such patterns include stripes, wavy stripes, and lattices. When the third intermediate layer has a line pattern (see FIG. 2), the thickness is, for example, 0.1 μm to 10 μm (preferably 0.2 μm to 5 μm, for example, 0.3 μm to 3 μm). The degree is exemplified. For example, only the third intermediate layer, or the second intermediate layer and the third intermediate layer may be formed in an arbitrary pattern.

Although the above heat dissipation board | substrate 1 is not necessarily limited to this, For example, it can manufacture suitably by implementing the following processes (1)-(5).
(1) The process of providing the 1st intermediate layer 41 which has copper as a main body and does not contain a glass component on the ceramic substrate 2 (2) The copper paste which contains copper powder, glass powder, and a dispersion medium on the 1st intermediate layer (3) A step of supplying a silver paste containing silver powder and a dispersion medium to provide a silver paste layer on the copper paste layer (4) A step of forming a copper plate on the silver paste layer Step of arranging and preparing an unfired laminate (5) Step of firing the unfired laminate in a temperature range of 500 ° C. to 700 ° C. to obtain a heat-radiating substrate

1. Formation of the first intermediate layer First, the ceramic substrate 2 made of the ceramic described above is prepared. As such a substrate, for example, a commercially available one may be purchased, or manufactured and prepared. When manufacturing the board | substrate 2, the manufacturing method etc. are not restrict | limited. For example, ceramic powder having a desired composition, a firing aid, a solvent, and the like are blended at a predetermined ratio, and pulverized and mixed with a ball mill or the like to prepare a slurry for forming a substrate. Then, for example, the slurry is supplied in a layer form on a carrier sheet, dried appropriately, and then degreased and fired at a predetermined temperature in an electric furnace or the like, whereby a ceramic substrate 2 as a sintered body of ceramic powder is obtained. Can be obtained. The substrate 2 can be cut into a predetermined size before firing or after firing.

  Then, the first intermediate layer 41 is provided on the prepared ceramic substrate 2. The means for constructing the first intermediate layer 41 is not particularly limited. For example, the first intermediate layer 41 can be formed by a coating method, a plating method, a pasting method, or the like. For example, when the first intermediate layer 41 is constructed by coating, for example, a first intermediate layer forming paste containing copper or a copper alloy as a solid content and dispersed in a dispersion medium is prepared. The intermediate layer forming paste may be applied (supplied) to the surface of the ceramic substrate 2 to construct the precursor layer of the first intermediate layer 41. This precursor layer may be dried or fired before supplying the copper paste in the next step, or may be fired together with other paste layers in the firing step described later.

  Further, for example, in the case of constructing the first intermediate layer 41 by pasting, a first intermediate layer 41 made of a foil (including a sheet, a plate, etc.) of a desired form is prepared, and this is used for the ceramic substrate 2. Place on top. If necessary, the placed foil may be pressed and adhered to the ceramic substrate 2. Here, the thickness of the foil can be a desired thickness of the first intermediate layer 41. Therefore, the first intermediate layer 41 may have a so-called foil shape (including a plate shape and a sheet shape). Thereby, the 1st intermediate | middle layer 41 can be constructed | assembled simply.

  Furthermore, for example, when the first intermediate layer 41 is constructed by a plating method, the specific method of the plating method is not particularly limited, and either a wet plating method or a dry plating method can be employed. Examples of the wet plating method include an electroless plating method and an electroplating method. Examples of the dry plating method include a vacuum deposition method, a sputtering method, a CVD method, and a PVD method. For example, a wet plating method can be preferably employed, and an electroless plating method is more preferable. The specific plating conditions for each of the above methods can be appropriately set based on a conventional method so that the thickness of the first intermediate layer 41 falls within a desired range, for example.

As a preferred embodiment of the production method disclosed herein, copper plating by an electroless plating method will be described. In this method, first, a plating solution containing copper and, if necessary, another metal element as a salt is prepared according to the composition of copper or copper alloy constituting the first intermediate layer 41. This copper plating layer is preferably substantially composed of a copper component (for example, 95% by mass or more of the entire copper plating layer). As a plating solution, for example, a commercially available electroless copper plating solution (for example, a copper sulfate solution) can be used. The plating solution is typically a copper salt (such as CuSO ₄ ), a reducing agent (such as HCHO), a pH adjuster (such as NaOH), a complexing agent (such as EDTA or Rochelle salt), and an accelerator. , Stabilizers (bipyridyl, polyethylene glycol, etc.) additives can be included. Then, the ceramic substrate 2 that is the object of plating is immersed in the plating solution, and the plating solution is agitated to be acclimated. In order to form the first intermediate layer 41 as a high-quality film, the surface activation treatment (conditioning, pre-dip, catalyzing, activation, etc.) is performed by immersing the ceramic substrate 2 in palladium chloride or the like in advance. It is preferable to carry out a pretreatment of What is necessary is just to set suitably the plating conditions (Cu concentration in a plating bath, temperature, immersion time, pH, etc.) in electroless plating so that desired plating thickness is implement | achieved suitably. For example, the ceramic substrate 2 is immersed in a plating bath having a predetermined concentration heated to about 30 ° C. to 90 ° C. for about several minutes to about 1 hour. After the plating treatment, the ceramic substrate 2 provided with the first intermediate layer 41 can be obtained by appropriately washing and drying.

2. Formation of copper paste layer On the 1st intermediate | middle layer 41 (it may be a precursor layer), the copper paste containing copper powder, glass powder, and a dispersion medium is supplied, and a copper paste layer is formed. Here, since the composition of the copper powder and the glass powder is the same as the copper component and the glass component of the second intermediate layer 42 described above, repeated description is omitted.
The copper powder is not particularly limited, but typically, for example, one having an average particle diameter of 10 μm or less can be used, preferably 7 μm or less, and more preferably 5 μm or less. The average particle size is preferably 1 μm or more, preferably 1.5 μm or more, particularly preferably 2 μm or more.
As the glass powder, those having an average particle diameter of 5 μm or less can be suitably used, preferably 3 μm or less, and more preferably 2.5 μm or less. The average particle size of the glass frit is preferably 0.5 μm or more, preferably 1 μm or more, and particularly preferably 1.5 μm or more.
The average particle diameter of the copper powder and the glass powder in the present specification is an integrated 50% particle diameter (D ₅₀ ) in a volume-based particle size distribution measured by a particle size distribution measuring apparatus based on a laser diffraction / scattering method. The average particle diameter employs a value measured using a laser diffraction / scattering particle size distribution measuring apparatus (LA-920, manufactured by Horiba, Ltd.).

Next, a copper paste can be prepared by mixing the copper powder and glass powder prepared above together with a dispersion medium. For mixing, various known emulsifiers, dispersers, mixers, kneaders, stirrers and the like can be used. For example, a three roll mill can be preferably used.
Examples of the dispersion medium include water, lower alkyl alcohols such as methyl alcohol, ethyl alcohol, butyl alcohol and propyl alcohol; alkyl ketones such as acetone and methyl ethyl ketone; ethers such as tetrahydrofuran, dioxane and diglyme; ethylene glycol and diethylene glycol. Glycol ethers such as diethylformamide, dimethylacetamide, N-methyl-2-pyrrolidone, and amides such as dimethylimidazolidinone can be preferably used. These may be used alone or in combination of two or more. A mixed solution of water and a lower alcohol is preferable.

  Although not always necessary, an organic binder may be added to the copper paste. Examples of such organic binders include those based on acrylic resins, epoxy resins, phenol resins, alkyd resins, cellulose polymers, polyvinyl alcohol, polyvinyl butyral, and the like. In the technique disclosed here, it is particularly preferable to use a binder made of a cellulose-based polymer or the like. Preferable examples of such a cellulose polymer include cellulose or a derivative thereof. Specific examples include hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, carboxymethyl cellulose, carboxyethyl cellulose, carboxyethyl methyl cellulose, cellulose, ethyl cellulose, methyl cellulose, ethyl hydroxyethyl cellulose, and salts thereof.

  And a copper paste layer can be shape | molded by employ | adopting an appropriate method and supplying said copper paste on the 1st intermediate | middle layer 41 in a layer form. Here, various supply methods such as a comma coater method, a slit reverse method, a die coater method, a gravure printing method, a doctor blade method, a spray coating method, a screen printing method, and a metal mask printing method are adopted for supplying the copper paste. be able to. The copper paste may be repeatedly supplied, for example, so that the second intermediate layer 42 having a desired thickness can be obtained by firing described later. Thereby, for example, a copper paste layer can be formed in an arbitrary pattern on the entire surface of the first intermediate layer 41 or a part thereof.

3. Formation of a silver paste layer On the copper paste layer formed above, a silver paste containing silver powder and a dispersion medium is supplied to form a silver paste layer. Here, since the composition of the silver powder is the same as that of the above-described silver component, repeated description is omitted.
Although silver powder is not specifically limited, For example, typically what is called nanopowder whose average particle diameter is 100 nm or less can be used conveniently. By using such nanopowder, the third intermediate layer 43 as a dense sintered film can be obtained. The average particle size of the silver powder is preferably 80 nm or less, more preferably 70 nm or less, and particularly preferably 60 nm or less. On the other hand, if the average particle size of the silver powder is too small, the sintering of the silver powder is likely to proceed, and this is not preferable in terms of handling properties. From this viewpoint, the average particle size is preferably 10 nm or more, more preferably 15 nm or more, and particularly preferably 20 nm or more.
The average particle diameter of the copper powder and the glass powder in the present specification is defined as an arithmetic average value of equivalent circle diameters of 100 or more particles based on observation with an electron microscope.

  The silver paste can be prepared in the same manner as the above copper paste by using the above silver powder. The silver paste layer can be formed in the same manner as the copper paste layer. The silver paste may be repeatedly supplied, for example, so that the third intermediate layer 43 having a desired thickness can be obtained by baking described later. Thereby, for example, the silver paste layer can be formed in an arbitrary pattern on the entire surface of the copper paste layer or a part thereof.

4). Preparation of unfired laminate A copper laminate 6 is arranged on the silver paste layer formed as described above to prepare an unfired laminate. Since the copper plate 6 is also as described above, repeated description is omitted. The prepared copper paste layer, silver paste layer, and unfired laminate may be dried (removal of the dispersion medium) at an appropriate time, and may be subjected to heat treatment for removing the binder as necessary. Good. Removal of the dispersion medium may be natural drying, or means such as air drying, heat drying, vacuum drying, and freeze drying may be used. The heat treatment for removing the binder may be, for example, about 120 ° C. or higher and 240 ° C. or lower (typically 150 ° C. or higher and 200 ° C. or lower) depending on the binder to be used.

5. Firing Next, the prepared unfired laminate is fired in a temperature range of 500 ° C. or higher and 700 ° C. or lower. Thereby, the heat dissipation board | substrate disclosed here can be obtained. The firing atmosphere can be selected according to the type of substrate, heating temperature, etc., and can be an air atmosphere, air atmosphere, oxidizing atmosphere, inert gas atmosphere (nitrogen gas, helium gas, argon gas, etc.), reducing atmosphere, or a mixture thereof. It can be appropriately selected from the atmosphere and the like. For example, it may be an atmospheric atmosphere.
In addition, although the example which bakes a copper paste layer and a silver paste layer simultaneously was shown in this example, these layers are not limited to baking simultaneously. For example, after forming the copper paste layer, the copper paste layer is baked to form the second intermediate layer 42, and then the silver paste layer is formed on the second intermediate layer 42. You may make it form the 3rd intermediate | middle layer 43 by mounting and baking a copper plate.

  In addition, said copper paste and silver paste do not need to contain components other than the binder used as needed, and components other than the material which comprises the 2nd intermediate | middle layer 42 and the 3rd intermediate | middle layer 43, respectively. . However, the content of various components in addition to these materials is allowed without departing from the object of the present application. Such components include additives added for the purpose of improving the properties and supplyability (for example, printability) of the copper paste and / or silver paste, and the second intermediate layer 42 and the third intermediate layer 43 as a fired product. Additives added for the purpose of improving the characteristics can be considered. Examples include surfactants, dispersants, fillers (organic fillers, inorganic fillers), viscosity modifiers, antifoaming agents, plasticizers, stabilizers, antioxidants, preservatives, and the like. One of these additives (compounds) may be contained alone, or two or more thereof may be contained in combination. However, it is not preferable to contain a component that inhibits the firing of the materials constituting the second intermediate layer 42 and the third intermediate layer 43, and an additive in an amount that inhibits these components. From this point of view, for example, an inappropriate silver powder protective agent or inorganic filler is not preferable. When the additive is included, the total content of these components is preferably about 5% by mass or less, more preferably 3% by mass or less, and particularly preferably 1% by mass or less based on the total silver paste.

  As described above, the heat dissipating substrate 1 disclosed herein does not require, for example, a fixing member, and the ceramic substrate 2 and the copper plate 6 for heat dissipation are stably integrated. Thereby, it is not necessary for the user to fix the copper plate 6 to the ceramic substrate 2 on site, and the heat dissipating substrate 1 can be easily used.

FIG. 3 is a cross-sectional view illustrating the configuration of the power module 10 for controlling the driving force of the railway vehicle. A power device 30 is mounted on the heat dissipating substrate 1 disclosed herein. Specifically, the power device 30 is, for example, an IGBT (Insulated Gate Bipolar Transistor). Two or more power devices 30 are mounted on the heat dissipation substrate 1. The heat dissipating substrate 1 includes, for example, a ceramic substrate 2 made of flat silicon nitride (Si ₃ N ₄ ), and the thickness of the ceramic substrate 2 is about 200 μm. A copper foil is provided on the surface (upper surface in the figure) of the ceramic substrate 2, and a circuit pattern 22 is formed by etching. Here, the copper foil is directly provided on the ceramic substrate 2, and this substrate 2 is a so-called DBC (Direct Bonded Copper) substrate. A copper plate 6 is bonded to the back surface (lower surface in the figure) of the ceramic substrate 2 with an intermediate layer 4 interposed therebetween. The thickness of the copper plate 6 in this example is about 1000 μm. On the circuit pattern 22, the power device 30 is joined by solder 32. Further, a cooler 50 is connected to the copper plate 6 via a thermally conductive grease 34.

  Such a power module 10 can be used in a temperature environment of, for example, room temperature (for example, a range of about −10 ° C. to 30 ° C.) to about 300 ° C. For example, when exposed to an environment where the temperature changes drastically from −40 ° C. to 250 ° C., thermal stress based on the difference in thermal expansion coefficient may be generated between the ceramic substrate 2 and the copper plate 6. However, the intermediate layer 4 can be softened gradually in a temperature range of 200 ° C. or more close to the softening point of the glass component contained therein while firmly bonding to the ceramic substrate 2 and the copper plate 6. Thereby, the thermal stress generated between the ceramic substrate 2 and the copper plate 6 is absorbed or relaxed by the glass component. Therefore, even when the thickness of the copper plate 6 is sufficiently thick and warp deformation or the like does not occur, the thermal stress generated between the ceramic substrate 2 and the ceramic substrate 2 is relieved by the presence of the glass component contained in the intermediate layer 4. Thereby, peeling of the copper plate 6 from the ceramic substrate 2 and breakage of the ceramic substrate 2 are suppressed. Further, the heat generated from the power device 30 is transmitted from the ceramic substrate 2 to the copper plate 6 through the intermediate layer 4, and can be effectively dissipated from the back side of the heat dissipation substrate 1. As a result, the power module 10 excellent in cycle heat dissipation is provided. In other words, the power module 10 having excellent heat dissipation and high reliability with respect to temperature change is provided.

(Embodiment 2)
FIG. 4 is a cross-sectional view illustrating the configuration of the power module 10 used in the power generation system using wind power or sunlight. The power module 10 includes a terminal case 52 including a lid 54. The power device 30 is mounted on the ceramic substrate 2 of the heat dissipation substrate 1. The power device 30 is, for example, an IGBT. In the cross-sectional view, one power device 30 is mounted on one heat dissipating substrate 1. The ceramic substrate 2 is a flat silicon carbide (SiC) substrate, for example, and has a thickness of about 100 μm. A copper foil is provided on the surface of the ceramic substrate 2, and a circuit pattern 22 is formed by etching. The power device 30 is electrically connected to the circuit pattern 22 by an aluminum wire 36. A copper plate 6 is bonded to the entire back surface of the ceramic substrate 2 via the intermediate layer 4. The thickness of the copper plate 6 in this example is about 1500 μm. The copper plate 6 has a larger area than the ceramic substrate 2. In other words, the ceramic substrate 2 is disposed on the copper plate 6 via the intermediate layer 4.

The power device 30 is housed in a terminal case 52 having a lid 54. Specifically, the terminal case 52 is placed on the copper plate 6 of the heat dissipation board 1 on which the power device 30 is mounted, and the heat dissipation board 1 and the terminal case 52 are fixed by a fixing member 58 having a fixing function. Has been. Examples of the fixing member 58 include fastening members such as screws, bolts, caulking, and rivets, and fitting members such as hooks and coupling pins.
The terminal case 52 and the lid 54 are each provided with a terminal 38. Each terminal 38 is electrically connected to the circuit pattern 22 on the substrate 20. The space inside the terminal case 52 that houses the power device 30 is filled with a silicone gel 56. Although not specifically shown, an electric / electronic circuit necessary for control can be accommodated in the terminal case 52 and integrated. Thereby, the power module 10 excellent in heat dissipation is provided.

  As described above, the heat dissipating substrate 1 disclosed herein can be suitably used as an insulating substrate with a heat dissipating plate of a power device. That is, the heat dissipation substrate 1 can be widely used as a TIM (Thermal Interface Material) in power devices, power modules, intelligent power modules, and the like. Moreover, this heat dissipation board | substrate 1 can be used suitably in order to prevent the damage | damage of the board | substrate in a power device with a large emitted-heat amount and a high thermal stress at the time of high load. Therefore, it can be suitably used as a TIM for devices for driving vehicles such as railway vehicles and automobiles and for operating substations that require high reliability. Specifically, for example, it can be used as a TIM of a rated element of 1200 V or more (for example, about 20 kV) for power control applications.

  Several examples relating to the present invention will be described below, but the present invention is not intended to be limited to the specific examples.

(Examples 1 to 13)
A copper layer was provided on the surface of a commercially available silicon nitride substrate (manufactured by Toshiba Materials Corp., TSN-90 plane, dimensions: 3.5 cm × 3.5 cm × (thickness 0.32 mm)) by an electroless plating method. For plating, an electroless copper plating solution manufactured by Okuno Pharmaceutical Co., Ltd. is used, and the plating time is adjusted so that the thickness of the copper layer of each example is in the range of about 0.5 μm to 10 μm as shown in Table 1. By adjusting, it was set as the 1st intermediate | middle layer.

  Next, a copper paste was printed in an island pattern in which squares of 10 mm square were arranged on the plated copper layer by metal mask printing, and dried. The copper paste is prepared by mixing copper powder having an average particle diameter of about 1 μm and glass frit having a softening point of about 400 ° C. in a mass ratio of 9: 1, and using ethyl cellulose (EC) as a binder and a solvent as a solvent. It was prepared by blending butyl diglycol acetate (BDGAC) with a solid content concentration of 75% and kneading with a three-roll mill. The copper paste was adjusted to have a thickness of about 100 μm to 500 μm as shown in Table 1 by repeatedly performing printing and drying as necessary. The composition of the glass frit used for the preparation of the copper paste is shown in Table 2 below.

  On the printed copper pattern, the silver paste was printed on the island pattern by metal mask printing using the same plate as described above. The silver paste was prepared by blending silver nanoparticles having an average particle diameter of 20 nm to 60 nm, EC, and BDGAC so that the solid concentration was 80%, and kneading with a three roll mill. Moreover, the silver paste was adjusted to have a thickness of about 3 μm to 20 μm as shown in Table 1 by repeatedly printing and drying as necessary.

  And on the printed silver pattern, after mounting the copper plate of thickness 0.5mm-1.0mm with the combination shown in Table 1, the copper plate was crimped | bonded to the silver pattern. The laminate thus prepared was degreased by heating to 200 ° C. to 400 ° C. in an air atmosphere, and then baked at 500 ° C. to 700 ° C. for 1 hour in a nitrogen atmosphere. Thus, Examples 1 to 13 in which the layers were laminated and integrated in the order of the silicon nitride substrate, the first intermediate layer (copper plating layer), the second intermediate layer (copper paste layer), the third intermediate layer (silver layer), and the copper plate. A heat dissipation substrate was obtained.

  For reference, a commercially available silicon nitride heat-dissipating substrate (Toshiba Materials Co., Ltd., silicon nitride active metal copper circuit (AMC) substrate, TSN-90, dimensions: 3.5 cm × 3.5 cm × (thickness)) 0.32 mm)) was prepared. This AMC substrate is obtained by bonding a copper plate having a thickness of 0.8 mm to the surface of the silicon nitride substrate (plane) through a Ni plating layer, a copper layer, and a solder layer.

[Heat cycle resistance of heat dissipation board]
The heat cycle test was implemented with respect to the heat-radiating board obtained after baking. The heat cycle was cooled to −40 ° C. at a rate of about −10 ° C./min, held at −40 ° C. for 60 minutes, then heated to 250 ° C. at a rate of 10 ° C./min, and 60 ° C. at 60 ° C. Holding for 1 minute was defined as 1 cycle, and this cycle was performed 1000 cycles. Then, it was visually observed whether cracks or peeling occurred between the heat dissipation substrate and the insulating substrate after the heat cycle test. The results are shown in the column of “Heat cycle resistance” in Table 1. In addition, "(circle)" in the said column shows that peeling and crack were not recognized by the whole heat radiating board | substrate including the paste layer and silver layer after a heat cycle test. “X” indicates that peeling or cracking was observed in the paste layer and the silver layer after the heat cycle test.

[Joint strength]
About the heat dissipation board | substrate after a heat cycle test, the adhesiveness of an insulating board | substrate and a copper plate was evaluated. The bondability was evaluated by peeling the insulating substrate and the copper plate by a die shear method using a bond strength tester (manufactured by Daisy Japan Co., Ltd., universal bond tester 4000). In other words, the insulating substrate part of the heat-dissipating substrate is fixed to a testing machine, a shear force is applied to the copper plate in the horizontal direction to the joint surface with a shear tool, and the shear force when the joint part peels or breaks at room temperature. Was measured. Such a test is performed in accordance with US MIL-STD-883 Integrated Circuit Test Method Mtd. It carried out according to 20044.7. The results are shown in the column “Joint strength” in Table 1.

[Measurement of thermal expansion coefficient]
The thermal expansion coefficients of the glass frit of each example prepared above, the sintered body of the copper paste, the sintered body of the silver paste, the silicon nitride substrate, and the copper plate were examined and listed in Table 1 below. The sintered body of copper paste and silver paste was cut from a 4 mm x 4 mm x 20 mm square column with a diamond cutter from the sintered body obtained by sintering each paste in bulk, and the thermal expansion coefficient was measured. did. For other materials, a 4 mm × 4 mm × 20 mm prism was cut out to obtain a test piece for measuring the thermal expansion coefficient. The thermal expansion coefficient of each sample is a test piece in a temperature range of room temperature (25 ° C.) to 500 ° C. using a thermomechanical analyzer (manufactured by Rigaku Corporation, TMA8310), with a temperature rising rate of 10 ° C./min. Was obtained by calculating the average linear expansion coefficient from the result of measuring the length of the film by the differential expansion method. The measurement of the thermal expansion coefficient was performed according to the method for measuring the linear expansion coefficient of a metal material specified in JIS Z2285: 2003. The results are shown in the “CTE” column of Table 1.

(Evaluation)
The thermal expansion coefficient of the silicon nitride substrate used as the insulating substrate from room temperature (25 ° C.) to 500 ° C. is approximately 2.6 × 10 ⁻⁶ / K. Moreover, the thermal expansion coefficient of the copper plate used as the heat sink is 16.5 × 10 ⁻⁶ / K. The difference in thermal expansion coefficient between these plate-like bodies is about 14 × 10 ⁻⁶ / K.
From the comparison of Examples 1 to 3 and 5, it was confirmed that the heat dissipating substrate of Example 3 not including the second intermediate layer formed using the copper paste was peeled from the copper plate and the insulating substrate by the heat cycle test. That is, as the intermediate layer, the first intermediate layer and the third intermediate layer are not sufficient, and a structure capable of withstanding a heat cycle in a temperature range from 5 ° C. to 500 ° C. is realized by further including the second intermediate layer. I understood that I can do it.

  Further, as shown in Example 1, the heat dissipation substrate of Example 1 in which the thickness of the third intermediate layer formed using the silver paste is not sufficient ensures sufficient bonding between the second intermediate layer and the copper plate. It was not possible, and it turned out that a board | substrate peels by the heat cycle in the temperature range from 25 degreeC to 500 degreeC. It has been found that the thickness of the third intermediate layer is preferably about 3 μm or more. In addition, as shown in Example 4, when the thickness of the third intermediate layer is 3 μm or more, for example, 5 μm, a bonding structure that achieves both bonding strength and heat cycle characteristics even if the thickness of the copper plate is 0.8 mm. It turns out that it is realized.

From the comparison of Examples 5 to 7, it was found that the thickness of the third intermediate layer can be increased to, for example, about 30 μm, but the bonding strength and heat cycle characteristics tend to be slightly reduced. It has been found that even if the thickness of the third intermediate layer is excessively increased, the bonding strength and heat cycle characteristics are not improved, and for example, about 30 μm or less, preferably about 25 μm or less is sufficient.
From the above, even with a copper plating layer (first intermediate layer) that enhances bonding properties and a silver layer (third intermediate layer) with good conductivity, even if the thickness of the silver layer is sufficiently thick as 0.8 μm. It was confirmed that it was not sufficient to join a copper plate having a thickness of 0.5 mm in an environment where the temperature change was severe. On the other hand, it was found that by providing the copper paste layer (second intermediate layer), a copper plate having a thickness of 0.5 mm can be suitably joined even if the thickness of the silver layer is reduced to 3 μm, for example.

  Moreover, from Examples 8 and 9, it was confirmed that sufficient bonding strength was obtained even when the thickness of the copper plating layer (first intermediate layer) was as thin as 0.5 μm. However, as can be seen from the comparison between Examples 10 and 12, when joining a thick copper plate with a thickness of 1.0 mm, both the joining strength and the heat cycle properties are obtained when the thickness of the silver layer (third intermediate layer) is 30 μm or more. It was confirmed that it was significantly reduced. On the other hand, as shown in Examples 11 and 12, when the thickness of the silver layer (third intermediate layer) is suppressed to, for example, 10 μm, the thickness of the copper paste layer (second intermediate layer) is 300 μm or more, for example, 500 μm. By setting it as the above, even if it was a case where a copper plate with a thickness of 1.0 mm was joined, it was confirmed that sufficient heat cycle characteristics can be provided.

  In addition, as above-mentioned, it has confirmed that the heat cycle characteristic of a heat-radiating board | substrate was fully improved by presence of a copper paste layer. This copper paste layer contains glass frit containing BaO or ZnO as a main component (for example, 80 mol% or more in total). It is considered that the glass component derived from this glass frit bonds Cu particles in the copper paste to each other and realizes strong bonding between the copper layer (first intermediate layer) and the silver layer (third intermediate layer). Get it. Further, the glass frit starts to soften near its softening point and can be deformed to sufficiently relax the expansion and contraction of copper in the copper plate. As a result, even when a thermal cycle in the temperature range of 25 ° C. to 500 ° C. is applied, the thermal stress between the copper plate and the insulating substrate is suitably relaxed, and peeling and cracking of the insulating substrate are suppressed. I understood.

  As mentioned above, although this invention was demonstrated in detail, the said embodiment is only an illustration and what changed and modified the above-mentioned specific example is included in the invention disclosed here.

DESCRIPTION OF SYMBOLS 1 Heat dissipation board 2 Ceramic substrate 4 Intermediate layer 41 1st intermediate layer 42 2nd intermediate layer 43 3rd intermediate layer 6 Copper plate 10 Power module 30 Power device

Claims (10)

A ceramic substrate, a copper plate, and an intermediate layer that integrally bonds the ceramic substrate and the copper plate,
From the side in contact with the ceramic substrate, the intermediate layer,
A first intermediate layer mainly composed of copper and not containing a glass component;
A second intermediate layer mainly composed of copper and containing a glass component;
A third intermediate layer mainly composed of silver;
A heat dissipating substrate comprising a laminated structure including:   The heat-radiating substrate according to claim 1, wherein the copper plate has a thickness of 500 μm or more.   The heat dissipation substrate according to claim 1 or 2, wherein the first intermediate layer has a thickness of 0.5 µm or more and 10 µm or less.   The heat dissipation substrate according to any one of claims 1 to 3, wherein the thickness of the second intermediate layer is 50 µm or more and 500 µm or less. The heat dissipation according to any one of claims 1 to 4, wherein the second intermediate layer has a thermal expansion coefficient of 11 x ^10-6 / K or more and 14 x ^10-6 / K or less at 25C to 500C. Substrate.   The heat dissipation substrate according to claim 1, wherein the third intermediate layer has a thickness of 3 μm or more and 25 μm or less.   The heat dissipation substrate according to any one of claims 1 to 6, wherein the third intermediate layer is a sintered layer formed by sintering silver nanoparticles having an average particle diameter of 20 nm to 60 nm.   The heat dissipation substrate according to any one of claims 1 to 7, wherein the glass component is configured to have a softening point of 250 ° C or higher and 450 ° C or lower.   The heat dissipation substrate according to any one of claims 1 to 9, wherein the ceramic substrate is mainly composed of at least one ceramic selected from the group consisting of silicon carbide, silicon nitride, and aluminum nitride. Providing a first intermediate layer mainly composed of copper and not containing a glass component on a ceramic substrate;
Supplying a copper paste containing copper powder, glass powder, and a dispersion medium on the first intermediate layer to form a copper paste layer;
Supplying a silver paste containing silver powder and a dispersion medium on the copper paste layer to provide a silver paste layer;
Arranging a copper plate on the silver paste layer to prepare an unfired laminate, and
Firing the green laminate in a temperature range of 500 ° C. or higher and 700 ° C. or lower to obtain a heat-radiating substrate;
A method for manufacturing a heat dissipating substrate.

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