JP4544964B2 - Heat dissipation board - Google Patents

Description

The present invention aims to increase the heat radiation efficiency of semiconductor elements such as IGBT (insulated gate bipolar transistor) elements, substrates for sublimation thermal printer heads, surface heating heater support substrates, heater support substrates for thermal ink jet printer heads, etc. about the heat radiation substrate and the junction how used.

In recent years, as heat dissipation substrates such as power transistor module substrates and switching power supply module substrates, heat dissipation substrates in which a metal plate such as a copper plate, an aluminum plate, and various clad plates are joined on a ceramic substrate are widely used. Yes. Moreover, as this ceramic substrate, as shown in Patent Documents 1 to 3, it is an inexpensive and versatile alumina (Al ₂ O ₃ ) substrate, or aluminum nitride having electrical insulation and excellent thermal conductivity. An (AlN) substrate, a silicon nitride (Si ₃ N ₄ ) substrate, or the like is generally used.

  For example, as shown in FIG. 1, the heat dissipating board in which the circuit is composed of the above-described copper plate or the like has a circuit board 3 made of copper bonded to one surface of a ceramic substrate 2 and a copper plate 4 bonded to the other surface. Formed.

As a technique for bonding various metal plates to the surface of the ceramic substrate 2, a direct bonding method, a refractory metal metallization method, an active metal method, or the like is used. In the direct bonding method, for example, a copper plate or the like that is punched into a predetermined shape and formed on a ceramic substrate 2 is contacted and heated, and a eutectic liquid phase such as Cu—Cu ₂ O or Cu—O is applied to the bonding interface. The so-called direct copper bonding method (DBC method: DBC method) in which the wettability with the ceramic substrate 2 is enhanced by the liquid phase and then the ceramic phase and the copper plate are directly bonded by cooling and solidifying the liquid phase. Direct Bonding Copper method). The refractory metal metallization method is a method in which a refractory metal such as molybdenum (Mo) or tungsten (W) is baked on the surface of the ceramic substrate 2 to integrally form a metal circuit layer. The active metal method is a method in which a metal is formed on the ceramic substrate 2 through an Ag—Cu brazing material layer containing an active metal such as a group 4A element such as titanium (Ti), zirconium (Zr), hafnium (Hf). In this method, the plates are joined together. According to this active metal method, the brazing material layer can be increased in bonding strength with the circuit board 3 by the main components of copper (Cu) and silver (Ag), while titanium (Ti), zirconium (Zr), hafnium (Hf) The bonding strength of the brazing material layer to the ceramic substrate 2 is increased by the component.

  In addition, as a specific method for forming a circuit, there are known methods such as using a copper plate patterned in advance by pressing or etching, or patterning by etching, laser, or the like after bonding.

  All of these heat dissipation substrates obtained by the direct bonding method and the active metal method have a high bonding strength between the ceramic substrate and the metal circuit board and have a simple structure. The advantage that it can be shortened is obtained, and there is an advantage that it can be applied to a large current type or highly integrated semiconductor element.

  However, when mounting the semiconductor element by soldering or the like, a large warp occurs in the heat dissipation substrate due to a rapid temperature rise, and a gap is formed between the ceramic substrate 2 and the circuit substrate 3 or between the ceramic substrate 2 and the copper plate 4. There is a problem in that the heat dissipation characteristics deteriorate due to this gap.

In order to solve such a problem, in Patent Document 1, the average crystal grain size of copper forming the metal circuit board 3 and the copper board 4 is 400 μm or more, the average sub-grain boundary density is 20 mm / mm ² or less, substantially 14 A heat dissipation board having a thickness of ˜18 mm / mm ² has been proposed.

  Patent Document 2 proposes a heat dissipation substrate in which active metal is adsorbed and heat-treated on the surface of the ceramic substrate 2 and then metal plating and brazing are sequentially performed in order to prevent the above-described gaps. Here, as a specific adsorption method of the active metal, a method of immersing and adsorbing the ceramic substrate 2 in a solution in which the active metal is dissolved, or Sn functioning as a sensitivity imparting agent to make adsorption more reliable. A method is disclosed in which sensitivity is given to the surface of the ceramic substrate 2 in advance with a solution containing ions, and then substitution deposition is performed with palladium (Pd).

Further, in Patent Document 3, in order to improve the adhesion between the ceramic substrate 2 and the circuit board 3 and the copper plate 4, both the circuit board 3 and the copper plate 4 are divided into a plurality of parts, and the heat dissipation is arranged substantially symmetrically with the ceramic substrate 2 interposed therebetween. A substrate has been proposed.

In recent years, high output of semiconductor devices using the heat dissipation substrate as described above and high integration of semiconductor elements have rapidly progressed, and thermal stress that repeatedly acts on the heat dissipation substrate tends to increase. Sufficient joint strength and durability against stress are required.
Japanese Patent No. 3211856 JP 2000-226274 A JP 2002-343911 A

  However, in the above-described heat dissipation board, although the initial bonding strength is high by improving the type of the ceramic substrate and the bonding method of the metal circuit board or copper plate, as proposed in Patent Document 1, the metal circuit board 3 or the copper plate When the average crystal grain size of copper forming 4 is 400 μm or more, the yield stress of copper is reduced, and it cannot withstand the thermal stress that repeatedly acts on the heat dissipation board, and the joint end D of the metal circuit board 3 and the copper board 4 There is a problem that peeling occurs from the circuit, causing malfunction of the circuit.

In addition, when the average sub-grain boundary density of copper is 14 to 18 mm / mm ² , warpage of the heat dissipation substrate can be reduced, but in this range, recrystallization occurs due to the heat treatment that the heat dissipation substrate is repeatedly subjected to. Along with this, there is a problem that copper is softened and mechanical properties of copper are lowered.

  Moreover, although it has been shown in the joining method proposed in Patent Document 2 that a heat dissipation substrate with high adhesion can be obtained by using palladium (Pd), ceramic using a solution in which palladium (Pd) is dissolved is used. Since it is adsorbed on the substrate, the yield of expensive palladium (Pd) is low, and there is a problem that it cannot be manufactured at low cost.

  In addition, in the method proposed in Patent Document 3, since both a metal circuit board and a copper board are produced, the manufacturing process is complicated and the manufacturing man-hour is increased, and the relative positioning accuracy and thickness accuracy of the metal circuit board and the copper plate are increased. There is also a problem that these precision adjustments are complicated.

The present invention has been made in order to solve the above-described problems, and has high bonding strength, high reliability, and no cracking or dielectric breakdown in addition to high heat dissipation characteristics and excellent heat cycle characteristics. and to provide an inexpensive high heat dissipation board.

The heat dissipation board of the present invention is a circuit board having a predetermined pattern mainly composed of copper on one surface of a ceramic substrate through a bonding layer mainly composed of copper, and copper or copper on the other surface of the ceramic substrate. in the heat radiation substrate by joining a metal substrate for heat dissipation composed mainly of alloys, an average crystal grain size of the copper or copper alloy constituting the metal substrate is 2 to 100 m, the average sub grain boundary density of 10 mm / mm ² or less.

Moreover, in which the Vickers hardness _{H Vc} and Vickers hardness _{H Vs} of the metal substrate of the binding layer and the above 1 GPa.

Further, the relationship between the Vickers hardness _HVc of the bonding layer and the Vickers hardness _HVs of the metal substrate satisfies | H _Vc −H _Vs | / H _Vc ≦ 0.85.

Furthermore, the average crystal grain size of copper constituting the bonding layer is 5 μm or less, and the average sub-grain boundary density is 10 mm / mm ² or less.

  Furthermore, the 0.2% proof stress of the metal substrate is set to 300 MPa or more.

Further, between the ceramic substrate and the bond layer, the second intermediate layer beauty Oyo first intermediate layer from the ceramic substrate side are sequentially formed, said first intermediate layer of molybdenum (Mo), rhodium (Rh) and at least any one of titanium (Ti) as a main component, a second intermediate layer above SL has Vickers hardness _{H Vi} is a principal component of nickel (Ni) or chromium (Cr) 0.7 GPa It is the above, It is characterized by the above.

  Still further, the ceramic substrate is characterized by comprising single crystal alumina or polycrystalline silicon nitride as a main component.

Furthermore, in the method for bonding a heat dissipation substrate of the present invention, a first intermediate layer mainly composed of at least one of molybdenum (Mo), rhodium (Rh) and titanium (Ti) is formed on a ceramic substrate. and, after forming the second intermediate layer mainly composed of at least any one of nickel (Ni) and chromium (Cr) to said first intermediate layer, forming a bond layer mainly composed of copper and, a metal substrate mainly composed of copper or a copper alloy thermocompression bonding in a hydrogen atmosphere above Symbol binding layer, cooled to lower than room temperature in crimped state, it is to抜圧raised to room temperature.

  Moreover, the said heating temperature shall be 380-400 degreeC, and cooling temperature shall be -60--40 degreeC.

Still further, in the heat dissipation substrate, the relationship between the thickness (T1) of the metal substrate and the thickness (T2) of the circuit substrate having a predetermined pattern satisfies | T1-T2 | /T1≦0.33.

In a heat dissipation substrate in which a metal substrate composed mainly of copper or a copper alloy is bonded to a ceramic substrate via a bonding layer composed mainly of copper, the average crystal grain size of copper or copper alloy constituting the metal substrate is 2 ～100Myuemu, the average sub grain boundary density with 10 mm / mm ² or less, it is possible to optimize the yield stress of the metal substrate, and is to improve the adhesion between the metal substrate and the bonding layer, the heat radiation substrate The generated warp can be reduced.

Further, the Vickers hardness H _Vc and the metal substrate Vickers hardness H _Vs of the binding layer by the above 1 GPa, brought into close contact with the high pressure and the metal substrate and the bonding layer.

Furthermore, the binding layer of Vickers hardness _{H Vc} and of the metal substrate a relationship Vickers hardness _{H Vs} | both _{/ H Vc} ≦ 0.8 in 5 to be, at the time of bonding with the bonding layer and the metal substrate | _H Vc _-H Vs Can be reduced, and a highly reliable heat dissipation substrate can be obtained.

Furthermore, by making the average crystal grain size of copper constituting the bonding layer 5 μm or less and the average sub-grain boundary density 10 mm / mm ² or less, the adhesion between the metal substrate and the ceramic substrate can be improved. , Warpage generated in the heat dissipation substrate can be reduced.

  Furthermore, by setting the 0.2% proof stress of the metal substrate to 300 MPa or more, the deformation resistance performance is improved and the durability is increased against thermal stress that repeatedly acts on the metal substrate.

Further, between the ceramic substrate and the bond layer, the second intermediate layer beauty Oyo first intermediate layer from the ceramic substrate side are sequentially formed, said first intermediate layer of molybdenum (Mo), rhodium (Rh) and as a main component at least one kind of titanium (Ti), Vickers hardness _{H vi} with a second intermediate layer above SL is mainly composed of nickel (Ni) or chromium (Cr) is 0.7GPa From the above, damage to the intermediate layer during bonding can be prevented, and adhesion between the metal substrate and the ceramic substrate can be improved. Further, since the first intermediate layer has a Young's modulus that is intermediate between the Young's modulus of the ceramic substrate and the metal substrate, it is possible to reduce the residual stress generated after joining, and the second intermediate layer is made of nickel (Ni ) or by a main component chromium (Cr), a first intermediate layer on SL and also can increase the wettability with any of the metal substrate, thereby improving the reliability of the bonding. In addition, since the first intermediate layer is mainly composed of titanium (Ti), the first intermediate layer has good moisture resistance, and the second intermediate layer is mainly made of nickel (Ni) or chromium (Cr). with component, can increase the wettability with any upper Symbol first intermediate layer and the metal substrate, it is preferable be employed radiating substrate under high humidity environment.

Furthermore, since the ceramic substrate is mainly composed of single crystal alumina, it can be a heat dissipation substrate that has good durability and heat dissipation characteristics against repeated thermal stress and heat load. Further, the ceramic substrate, a polycrystalline silicon nitride by a main component, polycrystalline silicon nitride thermal conductivity, high both flexural strength is therefore suitable when the thickness of the heat dissipation substrate is restricted.

Furthermore, in the above-described heat dissipation substrate bonding method, a first intermediate layer mainly composed of at least one of molybdenum (Mo), rhodium (Rh), and titanium (Ti) is formed on the ceramic substrate. after forming the second intermediate layer mainly composed of at least any one of nickel (Ni) or chromium (Cr) to the first intermediate layer to form a binding layer composed mainly of copper, a metal substrate mainly composed of copper or a copper alloy thermocompression bonding in a hydrogen atmosphere above Symbol binding layer, cooled to lower than room temperature in crimped state, by抜圧raised to room temperature, the heat radiation substrate The generated warpage can be further reduced.

  In particular, when the heating temperature is 380 to 400 ° C. and the cooling temperature is −40 to −60 ° C., it is effective for securing the bonding strength and reducing the warpage.

Furthermore, by setting the relationship between the thickness (T1) of the metal substrate and the thickness (T2) of the circuit substrate having a predetermined pattern to be | T1-T2 | /T1≦0.33, the warpage generated in the heat dissipation substrate is remarkably reduced. It is done.

  Embodiments of the present invention will be described below.

The present invention relates to a heat dissipation substrate in which a metal substrate mainly composed of copper or a copper alloy is bonded to a ceramic substrate via an intermediate layer mainly composed of an active metal, and the copper or copper alloy (hereinafter referred to as “the metal substrate”). Unless otherwise specified, for convenience, copper or a copper alloy is simply referred to as copper.) The average crystal grain size is 2 to 100 μm and the average sub-grain boundary density is 10 mm / mm ² or less.

Such heat dissipation substrate, for example, as shown in FIG. 2, and joining the copper plate as a circuit board 3 on one surface of the ceramic substrate 2, used on the other surface as a heat dissipation substrate formed by bonding a copper plate 4 .

Here, the average crystal grain size of copper constituting the metal substrate is set to 2 to 100 μm. When the average crystal grain size exceeds 100 μm, the yield stress of copper is too low, and thermal stress acts repeatedly on the heat dissipation substrate. In such a case, it is difficult to withstand such a thermal stress, and peeling occurs from the joint end of the metal circuit board 3 or the copper board 4, causing malfunction of the circuit. If the average crystal grain size is less than 2 μm, the copper This is because the yield stress is too high, and a large warp generated in the heat dissipation substrate remains after the joining.

Since the yield stress can be optimized by setting the average crystal grain size to 2 to 100 μm, it is possible to reduce the warpage that occurs at the time of bonding, and to peel even if the thermal stress repeatedly acts on the heat dissipation substrate. And a highly reliable heat dissipation substrate .

  By the way, as a thing with a big defect of copper, there exists the grain boundary which exists between grains, and the subboundary which generate | occur | produced in the crystal grain by hot rolling or cold rolling. This subboundary is also called a sub-grain boundary in order to distinguish it from a normal grain boundary, and in order to improve mechanical properties, the sub-grain boundary must be reduced.

The reason why the average sub-grain boundary density is set to 10 mm / mm ² or less in the present invention is that when the average sub-grain boundary density exceeds 10 mm / mm ² , the mechanical properties such as hardness and yield stress of copper and copper alloy are lowered. It is.

  The average crystal grain size can be measured by an intercept method (code method) using, for example, a scanning electron microscope (SEM) photograph (hereinafter referred to as an SEM photograph) with a magnification of 20 to 3000 times. Specifically, the grain size of crystals on a straight line of a certain length is measured from several SEM photographs so that the number of samples is 10 or more, preferably 20 or more, and the average is calculated.

The average sub-grain boundary density is calculated from the SEM photograph using D = (ΣLi · ni) / S. However, D: the average sub grain boundary density ^{(mm / mm 2), Li} : the length of a sub-grain boundaries (mm), ni: the number of a sub-grain boundaries, S: a measurement area (mm ^2). The sub-grain boundaries are generated as linear defects (transitions) that divide the crystal grains during hot rolling of copper or by cold rolling.

In particular, the average crystal grain size 5 to 20 [mu] m, and more preferably an average sub grain boundary density of 5 mm / mm ² or less.

Further, the Vickers hardness _{H Vc} and the Vickers hardness _{H Vs} of the metal substrate of the bonding layer may be at least 1GPa suitable. This is because the metal substrate and the bonding layer can be brought into close contact with each other with a high applied pressure, and the heat dissipation substrate is difficult to be plastically deformed even if the heat load acting repeatedly is large.

In particular, more than 1.2 GPa and Vickers hardness _{H Vc} bonding layer, it is further preferable that the Vickers hardness _{H Vs} of the metal substrate and the above 1.2 GPa.

The Vickers hardness H _Vc and HV _Vs may be measured in accordance with JIS Z 2244-1998, and the test load used for the measurement depends on the thickness of the bonding layer, for example, 98.07 mN or 196 mN. In addition, even if the test load applied to the bonding layer and the test load applied to the metal substrate are changed, in JIS Z 2244-1998, Hv = 0.188909 F / d ² (F: test load (N), d: diagonal of the indentation) Vickers hardness is uniquely determined because of the average length (mm).

Furthermore, it is preferable that the relationship between the Vickers hardness _HVc of the bonding layer and the Vickers hardness _HVs of the metal substrate is | H _Vc −H _Vs | / H _Vc ≦ 0.85. Damage to both the layer and the metal substrate during bonding can be reduced, and a highly reliable heat dissipation substrate can be obtained.

In particular, H _Vc > H _Vs because both of the bonding surfaces can be easily adjusted at the time of bonding, and even if the bonding layer is thin, the lower limit of | H _Vc −H _Vs | / H _Vc Is more preferably 0.4.

Furthermore, it is preferable that the average crystal grain size of copper constituting the bonding layer is 5 μm or less and the average sub-grain boundary density is 10 mm / mm ² or less.

  Here, the average crystal grain size of copper constituting the bonding layer is set to 5 μm or less. When the average crystal grain size exceeds 5 μm, when the bonding layer is as thin as about several tens of μm, the number of copper particles in the thickness direction is small. This is because there is a high possibility that the particles will be shed in a chain in an environment that is susceptible to vibration. When such degranulation occurs, the function as the bonding layer is lost. By setting the average crystal grain size of copper constituting the bonding layer to 5 μm or less, the adhesion between the metal substrate and the intermediate layer can be improved, and the warpage generated in the ceramic composite can be reduced. The average crystal grain size is preferably 2 to 5 μm for the convenience of production.

In addition, the average sub-grain boundary density of the bonding layer is set to 10 mm / mm ² or less because when the average sub-grain boundary density exceeds 10 mm / mm ² , when integrated with the metal substrate by bonding, copper or copper alloy This is because the mechanical properties such as hardness and yield stress are affected. In order to maintain these mechanical properties, it is preferable that the average sub-grain boundary density of the bonding layer is 10 mm / mm ² or less.

About the measuring method of the average crystal grain size and average subgrain boundary density of the said coupling layer, what is necessary is just to use the same method as the method measured with the metal substrate.

  The 0.2% proof stress of the metal substrate is preferably 300 MPa or more.

The 0.2% proof stress, when a load is applied to the material, is defined as the load per unit area to give a permanent strain of 0.2%, an index indicating the deformation resistance in the metal substrate. Moreover, 0.2% yield strength is measured based on JISZ2241-1998. Was not less than 300MPa 0.2% yield strength of the metal substrate, to heat stress acting repeatedly heat a substrate-release, is because deformation resistance performance is improved, especially when a small thickness of the metal substrate It is valid. This 0.2% proof stress often substitutes for yield stress because it is difficult to measure yield stress with soft metals such as copper and copper alloys.

  In particular, the 0.2% proof stress of the metal substrate is preferably 400 MPa or more.

  Furthermore, when high heat dissipation characteristics are required, a metal substrate made of any one of oxygen-free copper, tough pitch copper, phosphorous deoxidized copper, and non-produced copper is used, which has an extremely high copper content of 99.96% or higher. In particular, among oxygen-free copper, it is preferable to use linear crystalline oxygen-free copper having a copper content of 99.995% or more or single-crystal high-purity oxygen-free copper.

Further, between the ceramic substrate and the bond layer, the second intermediate layer are sequentially formed beauty Oyo first intermediate layer from the ceramic substrate side, the first intermediate layer of molybdenum (Mo), rhodium ( Rh) and titanium as a main component at least one kind of (Ti), the second intermediate layer above Symbol nickel (Ni) or chromium (Cr) Vickers hardness _{H Vi} is higher 0.7GPa is a principal component of Is preferable.

A ceramic substrate, compared with the case of forming the bonding layer containing copper as a main component directly, the intermediate layer is formed between the ceramic substrate binding layer, moreover by the intermediate layer has a two-layer structure, the thermal expansion it is possible to select the coefficients inclined manner, because it is possible to reduce the stress caused by the difference in thermal expansion between the ceramic substrate and the metal substrate. Further, by making the Vickers hardness H _{V i} of the second intermediate layer and above 0.7 GPa, when bonding the metal substrate, the deformation of the intermediate layer is prevented, damage not enter, the intermediate layer and the metal substrate Adhesion with is improved. More preferably, the Vickers hardness H _{V i} of the second intermediate layer is at least 0.8 GPa, that based on nickel (Ni) of the second intermediate layer, reducing the load on the environment Can do.

Incidentally, the Vickers hardness _{H V i} may be measured in compliance with JIS Z 2244-1998, test load used for the measurement depends on the thickness of the intermediate layer, for example a 98.07mN or 196MN.

The first intermediate layer is mainly composed of at least one of molybdenum (Mo), rhodium (Rh), and titanium (Ti). The first intermediate layer is mainly composed of molybdenum (Mo) in terms of wettability to the ceramic substrate, and manganese (Mn) is contained in an amount of 1 to 10% by mass with respect to molybdenum (Mo), or rhodium (Rh). ) Or titanium (Ti) is preferably used as a main component. The first intermediate layer is composed mainly of molybdenum (Mo), if it contains 1 to 10 wt% of manganese (Mn), preferably containing SiO ₂ trace, SiO ₂ is a ceramic substrate bonding strength It contributes to the improvement.

Further, since the first intermediate layer is mainly composed of molybdenum (Mo) or rhodium (Rh), the first intermediate layer has a Young's modulus intermediate between the Young's modulus of the ceramic substrate and the metal substrate. Residual stress generated later can be reduced, and further, with titanium (Ti) as a main component, the first intermediate layer has good moisture resistance, and the second intermediate layer is mainly made of Ni or Cr. By using it as a component, the wettability of both the first intermediate layer and the metal substrate can be improved, and it is preferable that the heat dissipation substrate is used in a high humidity environment. Further, the Vickers hardness of _{H V i} of the second intermediate layer to be at least 0.7GPa may be used means which will be described later.

  The ceramic substrate is preferably composed mainly of single crystal alumina or polycrystalline silicon nitride.

When alumina is the main component of the ceramic substrate, the thermal expansion coefficient of alumina is relatively close to the thermal expansion coefficient of the metal substrate, and the thermal conductivity is high among ceramics, so it is resistant to repeated thermal stresses. and it can be a good heat dissipation substrate both heat dissipation characteristics.

In particular, it is preferable to use a ceramic substrate using sapphire, which is a single crystal of alumina. When the ceramic substrate is thick, heat dissipation is good due to high thermal conductivity, and when the ceramic substrate is thin. However, the withstand voltage characteristics are not easily lowered, and dielectric breakdown does not occur. Further, when the main component of the ceramic substrate polycrystalline silicon nitride, polycrystalline silicon nitride thermal conductivity, high both flexural strength is therefore effective when the thickness of the heat dissipation substrate is restricted.

  Here, the main component means that at least 50% by mass or more of the material as the main component is included when the total mass of the ceramic substrate is 100%. In addition, when there is no thing which becomes 50 mass% or more with one component, it adds in order with the largest content, and the thing for which the sum total became 50 mass% or more for the first time is considered as a main component.

Furthermore, by setting the relationship between the thickness (T1) of the metal substrate and the thickness (T2) of the circuit substrate having a predetermined pattern to be | T1-T2 | /T1≦0.33, the warpage generated in the heat dissipation substrate is remarkably reduced. be able to.

When the above relationship is | T1-T2 | / T1> 0.33, there is no problem when the bonding area of the ceramic substrate is 400 mm ² or less. However, in the case of a large bonding area exceeding 400 mm ² , it occurs on the metal substrate side. This is because the balance between the residual stress and the residual stress generated on the substrate side on which the circuit is formed is poor, and a large warp may remain on the heat dissipation substrate . On the other hand, when | T1−T2 | /T1≦0.33, even if the bonding area of the ceramic substrate exceeds 400 mm ² , the balance between the residual stresses of the two can be controlled, and no large warpage occurs in the heat dissipation substrate. In particular, it is more preferable that | T1-T2 | / T1 <0.2.

Next, the manufacturing method of the thermal radiation board | substrate of this invention is demonstrated.

The heat dissipation substrate of the present invention has an outer dimension (30-60) mm × (10-30) mm × (0.13-0.4) mm mainly composed of any one of alumina, silicon nitride, aluminum nitride and the like. the ceramic substrate by electroless plating, after forming the bonding layer having a thickness of 10~20μm containing copper as a main component, in a hydrogen atmosphere a metal substrate mainly composed of copper, for example, thermocompression bonding binding layer at 200-420 ° C. Then, after cooling to a temperature lower than room temperature in the pressure-bonded state, it is obtained by raising the pressure to room temperature and releasing the pressure.

Here, the thermocompression bonding in the hydrogen atmosphere is to prevent the metal substrate and the bonding layer from being oxidized and the occurrence of unbonded portions, and after cooling to a temperature lower than room temperature in the crimped state, to raise to抜圧is lowered to lower than room temperature, the metal substrate and bonding layer temporarily surrender deform but, raising from a low temperature to normal temperature, deformation decreases. As a result, because it reduces the residual stress and warpage generated in the radiating substrate immediately after heat and pressure. In addition, in this invention, normal temperature shall refer to the temperature 15 grade prescribed | regulated to JISZ8703-1983, and shall refer to 20 +/- 15 degreeC.

In particular, the heating temperature is preferably 380 to 400 ° C. and the cooling temperature is −60 to −40 ° C. If the heating temperature is less than 380 ° C., an unreacted portion is generated at the interface between the metal substrate and the bonding layer. In some cases, if the temperature exceeds 400 ° C., residual stress tends to occur in the heat dissipation substrate . In addition, if the cooling temperature is less than −60 ° C., the manufacturing cost is increased. If the cooling temperature is higher than −40 ° C., the generated warp cannot be sufficiently reduced when the bonding area is large.

Here, in order to set the average crystal grain size of copper constituting the metal substrate to 2 to 100 μm, the crystal grains grow by heating, so the average crystal grain size of copper before bonding is set to 2 to 80 μm, for example. However, since the average crystal grain size after joining is easily changed by setting conditions in heating, pressure bonding, cooling, etc., it may be set as appropriate according to these conditions. In order to set the average sub-grain boundary density to 10 mm / mm ² , a metal substrate having an average sub-grain boundary density of 10 mm / mm ² or less is used in advance, or the cooling rate after thermocompression bonding is as high as possible, 120 ° C./min. This can be achieved by cooling the above or by adopting both.

In addition, the hardness of the metal substrate can be controlled by conditions such as the annealing temperature and time in the process of converting the copper ingot to the copper plate, the processing rate during rolling, and the subsequent aging treatment, etc. As a result, a metal substrate having a desired hardness can be obtained. Also, the hardness varies greatly depending on the heating temperature when bonding the metal substrate, to the Vickers hardness H _Vs of the metal substrate more than 1GPa, the heating temperature during joining may be above 380 ° C..

The binding layer is also the heating temperature at the time of bonding can be Vickers hardness H _Vc or more 1GPa by more than 380 ° C..

Furthermore, the binding layer of Vickers hardness _{H Vc} and the metal substrate Vickers hardness _{H Vs} of the relationship | _H Vc _-H Vs | To a _{/ H Vc} ≦ 0.85 is the Vickers hardness _{H Vc} of the binding layer, the binding When the thickness of the layer is about several tens of μm, it is not a little influenced by the hardness of the ceramic substrate, so it is possible by selecting the material of the ceramic substrate and adjusting the thickness of the bonding layer.

Further, in order to reduce the average crystal grain size of copper constituting the bonding layer to 5 μm or less, since the crystal grains grow by heating, the average crystal grain size of copper before bonding is set to 2 to 3 μm, for example. However, as with the metal substrate, the average crystal grain size after bonding is easily changed depending on the condition setting in heating, pressure bonding, cooling, etc., and may be set as appropriate according to these conditions. In order to set the average sub-grain boundary density to 10 mm / mm ² , the cooling rate after the thermocompression bonding may be as high as possible, and the cooling may be performed at 120 ° C./min or more.

Further, in the 0.2% yield strength of the metal substrate 300 M Pa or more, the average crystal grain size on which a 2 to 100 m, in advance iron (Fe), nickel (Ni), tin (Sn), zinc At least one of (Zn), phosphorus (P), chromium (Cr), and titanium (Ti) is included, and the total is 0.08 to 1.0 mass%.

  When an intermediate layer is formed between the ceramic substrate and the bonding layer, first, a paste containing molybdenum (Mo) powder as a main component and 1 to 10% by mass of Mn powder is applied, and a hydrogen atmosphere Alternatively, the first intermediate layer is formed by heat treatment at 1300 to 1700 ° C. in a mixed atmosphere of hydrogen and nitrogen. Further, when the first intermediate layer is rhodium (Rh), it may be formed by plating, and when it is titanium (Ti), it may be formed by sputtering.

Next, a second intermediate layer made of Ni or Cr is formed on the first intermediate layer by electroless plating, and then the bonding layers are sequentially formed. Here, the first intermediate layer, each thickness of the second intermediate layer 5 to 15 [mu] m, be a 1～3Myu m is suitable.

  Here, in order to make the hardness of the second intermediate layer 0.7 GPa or more, when nickel (Ni) is a main component, Ni—Co, Ni—P, Ni—Co—P, Ni—B, After an alloy film such as Ni-BP is formed by electroless plating, it is obtained by heat treatment at 280 to 330 ° C. for 30 minutes to 2 hours. In particular, in an environment where non-magnetism is required, any of non-magnetic Ni—P, Ni—B, and Ni—B—P is preferable. Also, when Cr is the main component, after forming the second intermediate layer by electroless plating, it can be heat treated at 280 to 330 ° C. for 30 minutes to 2 hours, so that the hardness can be 0.7 GPa or more. .

Radiating substrate as described above, as shown in FIG. 1 (a) ~ (e) , on the ceramic substrate 2, suitably used as a heat radiation substrate by forming a circuit in a predetermined pattern containing copper as a main component Can do. The heat dissipation substrate is formed by sequentially forming the first intermediate layer 5a, the second intermediate layer 6a, and the bonding layer 7a on the surface of the ceramic substrate 2 from the ceramic substrate 2 side, and joining the circuit substrate 3, while the ceramic substrate The first intermediate layer 5b, the second intermediate layer 6b, and the bonding layer 7b may be sequentially formed from the ceramic substrate 2 side, and the copper plate 4 having an excellent heat dissipation function may be joined to the back surface of the substrate 2 as well.

As described above, since the heat dissipation substrate of the present invention has good heat dissipation characteristics as described above, semiconductor elements such as IGBT (insulated gate bipolar transistor) elements and sublimation thermal printer heads are used without departing from the gist of the present invention. The present invention can also be applied to a substrate, a surface heating heater supporting substrate, a heater supporting substrate of a thermal ink jet printer head, and the like.

  Examples of the present invention will be specifically described below, but the present invention is not limited to these examples.

Example 1
A first intermediate layer, a second intermediate layer, and a bonding layer made of copper were sequentially formed on both surfaces of a ceramic substrate having a length of 30 mm and a width of 10 mm. The materials of the first intermediate layer and the second intermediate layer, other characteristics, and the characteristics of the bonding layer were as shown in Table 1.

Next, a substrate (hereinafter referred to as a circuit substrate) in which a metal substrate mainly composed of copper is formed on the back side of the ceramic substrate and a circuit having a predetermined pattern composed mainly of copper is formed on the front side of the ceramic substrate (hereinafter referred to as a circuit substrate). In an atmosphere, heat-pressed at 390 ° C., cooled to −50 ° C. in the pressure-bonded state, and then joined by depressurizing by raising to room temperature to obtain a heat dissipation substrate. The thickness (T1) of the metal substrate and the thickness (T2) of the circuit substrate are 1.5 mm and 0.98 mm, respectively, and the average crystal grain size, average sub-grain boundary density, 0.2% proof stress, Vickers hardness of the metal substrate. Table 1 shows _HVs , circuit board thickness (T2), heating temperature, and cooling temperature.

Regarding the warpage of the heat dissipation board, the longitudinal direction of the heat dissipation board is attached to the surface roughness meter with a spherical stylus, measured on the chart paper, drawn the baseline on the chart paper, and measured the concave and convex amounts from the baseline And the amount of warpage.

About the measurement of 0.2% yield strength, since it cannot measure with a heat sink, it prepared and measured the metal substrate for 0.2% yield strength measurement separately from the metal substrate for joining. Specifically, after giving the same thermal history as the heat history given to make the heat radiation substrate on Symbol metal substrate, JIS Z
It measured based on 2241-1998.

Further, the heat dissipation substrate 30 minute hold at -40 ° C., then after 3 minute hold at 125 ° C., - up to 40 ° C. performs a heat cycle test as one cycle the cycle of cooling, metal substrate, or released from binding layer The number of cycles in which substrate peeling (including partial ones) occurred was confirmed by ultrasonic flaw detection.

  Note that the probe used in the ultrasonic flaw detection method has a focal depth of 25 mm, and the frequency of the ultrasonic wave oscillated from the pulse transmitter to the heat dissipation substrate via the probe is 10 MHz. In addition, the heat dissipation substrate was immersed in water in advance, and ultrasonic waves were incident from the metal substrate side and then the circuit board side to detect the reflected wave generated from the joint, and a reflected image was created at a magnification of 1.5.

When this reflected image is blurred or a white portion is generated, it indicates that peeling has occurred, and Table 1 shows the number of cycles in which peeling has been confirmed. In Table 1, what was entered as ≧ 3000 is a sample in which peeling was not confirmed even after 3000 cycles.

As can be seen from Tables 1 and 2, Sample No. No. 21 has a large warp because the average crystal grain size of the metal substrate is less than 2 μm. Sample No. No. 22 has an average crystal grain size exceeding 100 μm, and sample No. 22 outside the scope of the present invention. No. 23 has an average sub-grain boundary density of more than 10 mm / mm ² , and thus has a low 0.2% proof stress, and either the metal substrate or the circuit board is peeled from the bonding layer at the beginning of the heat cycle test.

On the other hand, sample no. Nos. 1 to 20 have a small warpage and did not peel even after exceeding 1000 cycles, so that they can be said to be heat radiation substrates with good heat radiation characteristics and high reliability. In particular, the sample Vickers hardness _{H Vc} Oyo beauty metal substrate Vickers hardness _{H Vs} bonding layer is not less than 1 GPa No. 7,8, relationship between the Vickers hardness _{H Vc} and the metal substrate Vickers hardness _{H Vs} bonding layer is | _H Vc _-H Vs | samples meet _{/ H Vc} ≦ 0.85 No. Sample No. 9-12, the average crystal grain size of copper constituting the bonding layer was 5 μm or less , and the average sub-grain boundary density was 10 mm / mm ² or less. Sample Nos. 4 to 6 and 0.2% proof stress of the metal substrate of 300 MPa or more. 17 and 18, Oyo between the beauty ceramic substrate and bond layer, a second intermediate layer are sequentially formed beauty Oyo first intermediate layer from the ceramic substrate side, the upper Symbol second intermediate layer the Vickers hardness H _Vi is 0.7GPa
Sample No. as described above. 2 and 3, the warp is small, because the peeling did not occur even at 3000 cycles, high reliability, it can be said that good heat dissipation substrate of the heat radiation characteristics.

(Example 2)
A first intermediate layer, a second intermediate layer, and a bonding layer made of copper are formed on both sides of a ceramic substrate (length 30 mm, width 15 mm) larger than the ceramic substrate used in Example 1 and made of an alumina single crystal. Sequentially formed. The first intermediate layer is molybdenum (Mo), the second intermediate layer is nickel (Ni) containing a small amount of phosphorus (P), its hardness H _vc is 0.7 GPa, the average crystal grain size of the bonding layer, the average sub grain boundary density, the Vickers hardness _{H Vc} respectively 5 [mu] ^m, 12 mm / mm 2, was 0.8 GPa.

  Next, a metal substrate containing copper as a main component on the back side of the ceramic substrate, and a circuit substrate containing copper as a main component on the front side of the ceramic substrate are thermocompression bonded in a hydrogen atmosphere, and the temperature is lower than normal temperature in the pressed state. After cooling to room temperature, bonding was performed by raising the pressure to room temperature and releasing pressure to obtain a heat dissipation substrate.

In addition, the average crystal grain size, average sub-grain boundary density, 0.2% proof stress, Vickers hardness H _Vs , and thickness (T1) of the metal substrate are 40 μm, 10 mm / mm ² , 250 MPa, 0.8 GPa, 1.5 mm, The thickness (T2), heating temperature, and cooling temperature of the circuit board were as shown in Table 2.

The same method as in Example 1 was used for confirming the warpage of the heat dissipation substrate, 0.2% proof stress, and peeling of the metal substrate or circuit substrate.

The results are shown in Table 3.

  As can be seen from Table 3, the sample No. 1 was bonded with the heating temperature set at 380 to 400 ° C. and the cooling temperature set at −60 to −40 ° C. Nos. 25, 27 to 32, and 34 have small warpage, and peeling does not occur even after 3000 cycles or more.

  In addition, the sample No. 1 in which the relationship between the thickness (T1) of the metal substrate and the thickness (T2) of the circuit substrate satisfies | T1-T2 | /T1≦0.33. Nos. 29 to 31 have a smaller warp of 50 μm or less and are found to be favorable.

(A), (b), (c), (d), and (e) are the top view, AA sectional drawing, rear view, B part enlarged view, and C part enlarged view of the thermal radiation board | substrate of this invention , respectively.

1: heat dissipation substrate 2: ceramic substrate 3: circuit substrate 4: copper plates 5a, 5b: first intermediate layers 6a, 6b: second intermediate layers 7a, 7b: coupling layers

Claims (8)

Through a bonding layer mainly composed of copper, a circuit board having a predetermined pattern mainly composed of copper on one surface of the ceramic substrate, and heat radiation mainly composed of copper or a copper alloy on the other surface of the ceramic substrate. In the heat dissipation board to which the metal substrate is bonded, the average crystal grain size of copper or copper alloy constituting the metal substrate is 2 to 100 μm, and the average sub-grain boundary density is 10 mm / mm ² or less. Heat dissipation board. 2. The heat dissipation substrate according to claim 1, wherein the bonding layer has a Vickers hardness _HVc and the metal substrate has a Vickers hardness _HVs of 1 GPa or more. 3. The heat dissipation according to claim 1, wherein the relationship between the Vickers hardness _HVc of the bonding layer and the Vickers hardness _HVs of the metal substrate satisfies | H _Vc −H _Vs | / H _Vc ≦ 0.85. substrate. The heat dissipation substrate according to claim 1, wherein an average crystal grain size of copper constituting the bonding layer is 5 μm or less and an average sub-grain boundary density is 10 mm / mm ² or less. .   The heat dissipation substrate according to any one of claims 1 to 4, wherein the metal substrate has a 0.2% yield strength of 300 MPa or more. A first intermediate layer and a second intermediate layer are sequentially formed from the ceramic substrate side between the ceramic substrate and the bonding layer, and the first intermediate layer includes molybdenum (Mo), rhodium (Rh) and The main component is at least one of titanium (Ti), the second intermediate layer is mainly composed of nickel (Ni) or chromium (Cr), and has a Vickers hardness H _Vi of 0.7 GPa or more. The heat dissipation substrate according to claim 1, wherein the heat dissipation substrate is a heat dissipation substrate.   The heat dissipation substrate according to any one of claims 1 to 6, wherein the ceramic substrate is mainly composed of single crystal alumina or polycrystalline silicon nitride.   The heat dissipation according to any one of claims 1 to 7, wherein the relationship between the thickness (T1) of the metal substrate and the thickness (T2) of the circuit substrate satisfies | T1-T2 | /T1≦0.33. substrate.

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