JPWO2019187767A1 - Insulating substrate and manufacturing method thereof - Google Patents

Abstract

The present invention provides an insulating substrate in which a ceramic substrate, a first copper plate material formed on one surface of the ceramic substrate, and a second copper plate material formed on the other surface of the ceramic substrate are joined. Regarding Each copper plate material has a total content of metal components selected from Al, Be, Cd, Mg, Pb, Ni, P, Sn and Cr of 0.1 to 2.0 ppm, and a copper content of 99.96 mass% or more. When the Euler angles (φ1, Φ, φ2) represent the crystal orientation distribution function obtained from the texture analysis by EBSD of the surface of each copper plate having the composition, φ1 = 75 ° ~ 90 °, Φ = 20 In the range of ° -40 °, φ2 = 35 °, the average value of azimuth density is 0.1 or more and less than 15.0, and φ1 = 20 ° -40 °, φ = 55 ° -75 °, φ2 = 20 ° The average value of the orientation density is 0.1 or more and less than 15.0, and the average crystal grain size of each copper plate material is 50 μm to 400 μm.

Description

  The present invention relates to an insulating substrate, particularly an insulating substrate for power devices and a method for manufacturing the insulating substrate.

  Generally, a power device uses a high voltage and a large current, so that deterioration of material properties due to heat generated by a semiconductor element is a problem. Therefore, in recent years, measures for insulation and heat dissipation have been taken by using an insulating substrate in which a ceramic substrate having excellent insulation and heat dissipation is joined to a copper plate.

  For joining the ceramic substrate and the copper plate, a joining method of joining via a silver-based brazing material or the like, a joining method of joining using a eutectic reaction of copper without using a brazing material, etc. are mainly used. There is. Aluminum nitride, alumina, silicon nitride or the like is used for the ceramic substrate, but the thermal expansion coefficient of these is different from the thermal expansion coefficient of the copper plate material forming the copper plate. Therefore, when the semiconductor element generates heat, a large strain tends to occur in the entire insulating substrate due to the difference in thermal expansion coefficient. In addition, since the copper plate material has a higher thermal expansion coefficient between the ceramic substrate and the copper plate material, when heat treatment is performed, tensile stress is applied to the ceramic substrate and compressive stress is applied to the copper plate. As a result, a high strain is applied to the entire insulating substrate, the insulating substrate is deformed due to thermal expansion, and a dimensional change occurs, and the ceramic substrate and the copper plate are easily separated. Therefore, there is a demand for an insulating substrate that is as deformable as possible even when heated.

  Further, in the high-purity copper used for the copper plate, crystal grains grow remarkably at a high temperature of 700 ° C. or more at the time of joining, it becomes difficult to homogenize the structure, and in addition, elongation and tensile strength also decrease. Therefore, there is a problem that the bondability is deteriorated and it becomes a starting point of grain boundary fracture when strain occurs. Therefore, by improving the tensile strength and elongation of the copper plate using high-purity copper that constitutes the insulating substrate and appropriately refining the crystal grains, the resistance to the load due to the deformation due to thermal expansion is increased, It is expected to prevent field destruction and further improve bondability.

  For example, Patent Document 1 discloses, as a pure copper plate used for a heat dissipation substrate, a pure copper plate made of pure copper having a purity of 99.90 mass% or more and having a specified ratio of X-ray diffraction strength. In the oxygen-free copper constituting the pure copper plate, the etching property of the pure copper plate is improved by defining the crystal grain size of 100 μm or less and the ratio of the X-ray diffraction intensity.

  Further, in Patent Document 2, as a copper alloy plate suitable for electronic components for heat dissipation, electronic components for large current, etc., a copper alloy plate having a tensile strength of 350 MPa or more and controlling the degree of integration of crystal orientation at a predetermined position. Is disclosed. By controlling the degree of integration of the crystal orientation at a predetermined position, the repetitive bending workability of the copper alloy plate is improved.

JP, 2014-189817, A Japanese Patent No. 5475914

  However, the pure copper plate disclosed in Patent Document 1 has excellent adhesion to other members because the surface is less likely to have irregularities due to etching, but the joining with other members at high temperatures is completely investigated. It has not been. Further, the copper alloy plate disclosed in Patent Document 2 has been studied for heat resistance, but only heat resistance by heat treatment at 200 ° C. for 30 minutes is considered. Furthermore, the copper alloy plate disclosed in Patent Document 2 has a tensile strength of 350 MPa or more, and does not correspond to the range of 150 to 330 MPa suitable as a copper plate material used for an insulating substrate. Further, in any of Patent Documents 1 and 2, there is no mention of a problem after the copper plate is bonded to the insulating substrate. Therefore, when the semiconductor element generates heat, problems of deformation of the insulating substrate and separation of the ceramic substrate and the copper plate caused by a difference in thermal expansion coefficient between the copper plate material and the ceramic substrate, and joining them at a high temperature of 700 ° C. or higher. The problems of non-uniformity of the structure due to the growth of crystal grains and deterioration of the bondability which have occurred at this time have not yet been solved.

  In view of the above circumstances, an object of the present invention is to provide an insulating substrate having a copper plate material having excellent heat resistance and finely crystallized grains, and a method for manufacturing the same.

[1] An insulating substrate in which a ceramic substrate, a first copper plate material formed on one surface of the ceramic substrate, and a second copper plate material formed on the other surface of the ceramic substrate are joined. There
The first and second copper sheet materials have a total content of metal components selected from Al, Be, Cd, Mg, Pb, Ni, P, Sn, and Cr of 0.1 to 2.0 ppm, and copper content. The composition has a composition of 99.96 mass% or more, and the crystal orientation distribution function obtained from the texture analysis by EBSD of the surfaces of the first and second copper sheet materials is Euler angles (φ1, φ, φ2). ), The average value of the orientation density in the range of φ1 = 75 ° to 90 °, φ = 20 ° to 40 °, φ2 = 35 ° is 0.1 or more and less than 15.0, and φ1 = 20 °. Has a rolling texture in which the average value of the orientation density in the range of -40 °, Φ = 55 ° to 75 °, and Φ2 = 20 ° is 1.0 or more and less than 15.0, and
An insulating substrate in which the average crystal grain size of the first and second copper plate materials is 50 μm or more and 400 μm or less.
[2] The insulating substrate according to [1], wherein the average crystal grain size of the first and second copper plate materials is more than 100 μm and 400 μm or less.
[3] The ceramic substrate is formed of a ceramic material containing at least one selected from the group consisting of aluminum nitride, silicon nitride, alumina, and a compound of alumina and zirconia as a main component. [1] Alternatively, the insulating substrate according to [2].
[4] The insulating substrate according to any one of [1] to [3], wherein the first and second copper sheet materials have a tensile strength of 210 MPa or more and 250 MPa or less.
[5] The insulating substrate according to any one of [1] to [4], wherein the first and second copper sheet materials have an elongation of 25% or more and less than 50%.
[6] The insulating substrate according to any one of [1] to [5], wherein the electrical conductivity of the first and second copper plate materials is 95% IACS or more.
[7] A method for manufacturing an insulating substrate according to any one of [1] to [6],
With respect to the first rolled material that is the material of the first copper sheet and the second rolled material that is the material of the second copper sheet, the heating rate is 10 ° C / sec to 50 ° C / sec, An annealing step of performing an annealing treatment under the conditions that the ultimate temperature is 250 ° C to 600 ° C, the holding time is 10 seconds to 3600 seconds, and the cooling rate is 10 ° C / second to 50 ° C / second;
A cold rolling step of performing, after the annealing step, cold rolling at a total working rate of the first rolled material and the second rolled material of 10 to 65%;
After the cold rolling step, the first rolled material is bonded to one surface of the ceramic substrate, and the second rolled material is bonded to the other surface of the ceramic substrate via a brazing material, A bonding step of forming an insulating substrate in which the first copper plate material and the second copper plate material are respectively bonded,
In the joining step, a first heat treatment is performed in which a temperature rising rate is 10 ° C./second to 100 ° C./second, an ultimate temperature is 400 ° C. to 600 ° C., and a holding time is 10 seconds to 300 seconds; Production of an insulating substrate composed of a second heat treatment in which a heat treatment is performed at a speed of 10 ° C./sec to 100 ° C./sec, an ultimate temperature of 750 ° C. to 850 ° C., and a holding time of 100 seconds to 7200 seconds. Method.

  According to the present invention, the ceramic substrate, the first copper plate material formed on one surface of the ceramic substrate, and the second copper plate material formed on the other surface of the ceramic substrate are joined together. In the insulating substrate, the first and second copper plates have a total content of metal components selected from Al, Be, Cd, Mg, Pb, Ni, P, Sn and Cr of 0.1 to 2.0 ppm. , The content of copper is 99.96 mass% or more, and the crystal orientation distribution function obtained from the texture analysis by EBSD of the surfaces of the first and second copper sheet materials is the Euler angle (φ1 , Φ, φ2), the average value of the orientation density in the range of φ1 = 75 ° to 90 °, φ = 20 ° to 40 °, φ2 = 35 ° is 0.1 or more and less than 15.0, φ1 = 20 ° -40 °, φ = 55 ° -75 °, φ2 = 20 ° By having a rolling texture having an average value of orientation density of 1.0 or more and less than 15.0 and having an average crystal grain size of the first and second copper sheet materials of 50 μm or more and 400 μm or less, An insulating substrate having excellent heat resistance can be obtained.

  Further, according to the present invention, since the first and second copper sheet materials have excellent heat resistance characteristics, the load stress of the entire insulating substrate is reduced and the resistance force to the load due to thermal expansion is increased. As a result, deformation of the insulating substrate caused by the difference in thermal expansion coefficient between the first and second copper plate materials and the ceramic substrate, and further separation of the ceramic substrate and the first and second copper plate materials, that is, bonding property The decrease can be suppressed.

It is a crystal orientation distribution diagram which shows an example of the result of having measured the rolling texture of the surface of the copper plate material used for the insulating substrate of this invention by EBSD, and analyzing it by ODF. FIG. 1 (A) is a crystal orientation distribution diagram of φ2 = 20 °, and FIG. 1 (B) is a crystal orientation distribution diagram of φ2 = 35 °.

  Details of the insulating substrate of the present invention and embodiments will be described below. In addition, below, the numerical range represented using "-" means the range including the numerical values described before and after "-" as a lower limit and an upper limit.

<Insulating substrate>
In the insulating substrate of the present invention, a ceramic substrate, a first copper plate member formed on one surface of the ceramic substrate, and a second copper plate member formed on the other surface of the ceramic substrate are joined together. ing. That is, in the insulating substrate, the ceramic substrate is arranged between the first copper plate member and the second copper plate member, and the first copper plate member, the ceramic substrate, and the second copper plate member are respectively arranged in this order. It has a roll-bonded laminated structure. The first copper plate material and the ceramic substrate, and the ceramic substrate and the second copper plate material may have a layered structure in which they are bonded to each other. The first copper plate material and the ceramic substrate, and the ceramic substrate and the second copper plate material may be joined by, for example, a brazing material, an adhesive, solder, or the like, and it is particularly preferable that they are joined by a brazing material. . The thickness of the insulating substrate can be appropriately selected according to the usage situation, and is preferably 0.3 mm to 10.0 mm, more preferably 0.8 mm to 5.0 mm. In addition, unless otherwise specified, the first and second copper plate materials may be simply referred to as “copper plate materials” below for convenience.

[Ceramic substrate]
The ceramic substrate used for the insulating substrate of the present invention is not particularly limited as long as it is made of a ceramic material having a high insulating property. Such a ceramic substrate is preferably formed using, for example, a ceramic material containing, as a main component, at least one of aluminum nitride, silicon nitride, alumina, and a compound of alumina and zirconia. The thickness of the ceramic substrate is not particularly limited, but is preferably 0.05 mm to 2.0 mm, and more preferably 0.2 mm to 1.0 mm.

[Copper plate material]
Generally, a copper material means a material obtained by processing a copper material (before processing and having a predetermined composition) into a predetermined shape (for example, a plate, a strip, a foil, a bar, a wire, etc.). Among them, the “plate material” refers to a material having a specific thickness, stable in shape, and spreading in the surface direction, and broadly means to include a strip material. The "copper plate material" in the present invention means the "plate material" formed from copper having a predetermined composition.

[Copper sheet material composition]
The copper plate material used for the insulating substrate of the present invention has a copper content of 99.96 mass% or more, preferably 99.99 mass% or more. When the content of copper is less than 99.96 mass%, the thermal conductivity decreases, and desired heat dissipation cannot be obtained. Further, the copper plate material has a total content of metal components selected from Al, Be, Cd, Mg, Pb, Ni, P, Sn and Cr of 0.1 ppm to 2.0 ppm. The lower limit of the total content of these metal components is not particularly limited, but is 0.1 ppm in consideration of inevitable impurities. On the other hand, if the total content of these metal components exceeds 2.0 ppm, the desired orientation density cannot be obtained. Therefore, the effect of increasing the resistance force to the load due to the thermal expansion applied to the insulating substrate cannot be obtained, and the insulating substrate may be deformed or the ceramic substrate and the copper plate material may be separated from each other. Further, the copper plate material may contain inevitable impurities as the balance in addition to copper and a metal component selected from Al, Be, Cd, Mg, Pb, Ni, P, Sn and Cr. . The unavoidable impurities mean impurities at a content level that can be unavoidably included in the manufacturing process. The composition of the first copper plate material and the composition of the second copper plate material may be the same or different, but from the viewpoint of production efficiency, it is preferable that they are the same.

  The GDMS method can be used for the quantitative analysis of the metal components of the copper plate material. The GDMS method is an abbreviation for Glow Discharge Mass Spectrometry, in which a solid sample is used as a cathode, the sample surface is sputtered using glow discharge, and emitted neutral particles are ionized by colliding with Ar and electrons in plasma. This is a technique for analyzing the proportion of trace elements contained in metals by measuring the number of ions with a mass spectrometer.

[Rolling texture]
The copper plate used for the insulating substrate of the present invention has a crystal orientation distribution function (ODF) obtained from texture analysis by EBSD of the surface of the copper plate at Euler angles (φ1, Φ, φ2). When expressed, the average value of the orientation density in the range of φ1 = 75 ° to 90 °, φ = 20 ° to 40 °, φ2 = 35 ° is 0.1 or more and less than 15.0, and φ1 = 20 °. The rolling texture has an average value of the orientation density in the range of -40 °, Φ = 55 ° to 75 °, and Φ2 = 20 ° of 0.1 or more and less than 15.0. Regarding the Euler angles (φ1, φ, φ2), the rolling direction is the RD direction, the direction orthogonal to the RD direction (plate width direction) is the TD direction, and the direction perpendicular to the rolling surface (RD surface) is the ND direction. At this time, the azimuth rotation about the RD direction is represented by Φ, the azimuth rotation about the ND direction is represented by φ1, and the azimuth rotation about the TD direction is represented by φ2. The orientation density is a parameter used when quantitatively analyzing the existence ratio and the dispersion state of the crystal orientation in the texture, and performs the EBSD and the X-ray diffraction to obtain (100), (110), (112), etc. It is calculated by the crystal orientation distribution analysis method by the series expansion method based on the measurement data of three or more kinds of positive electrode diagrams. The distribution of orientation density in the RD plane is shown in the crystal orientation distribution chart in which φ2 obtained from the texture analysis by EBSD is fixed at a predetermined angle. The rolling texture of the first copper sheet material and the rolling texture of the second copper sheet material may be the same or different, but from the viewpoint of production efficiency, they are the same. preferable.

  The EBSD method is an abbreviation for Electron BackScatter Diffraction, and is a crystal orientation analysis technique utilizing reflected electrons generated when a sample is irradiated with an electron beam in a scanning electron microscope (SEM). In the analysis by EBSD, the measurement area and the scan step may be determined according to the size of the crystal grain of the sample. For the analysis of the crystal grains after the measurement, for example, analysis software OIM Analysis (trade name) manufactured by TSL can be used. The information obtained in the analysis of crystal grains by EBSD includes information up to a depth of several tens nm where the electron beam penetrates the sample. It is preferable that the measurement location in the thickness direction is in the vicinity of a position 1/8 to 1/2 times the plate thickness from the sample surface.

  FIG. 1 is a crystal orientation distribution diagram showing an example of a result obtained by measuring a rolling texture of a surface of a copper plate material used for an insulating substrate of the present invention by EBSD and analyzing by ODF. FIG. 1 (A) is a crystal orientation distribution diagram of φ2 = 20 °, and FIG. 1 (B) is a crystal orientation distribution diagram of φ2 = 35 °. In the crystal orientation distribution diagram, assuming that the crystal orientation distribution is random and the orientation density is 1, the contour lines show how many times the orientation density is integrated. In FIG. 1, the white portion has a high azimuth density, the black portion has a low azimuth density, and the other portions have a higher azimuth density as they are closer to white. In the present invention, in FIG. 1A, the average value of the azimuth density in the region surrounded by the dotted line (φ1 = 20 ° to 40 °, Φ = 55 ° to 75 °, φ2 = 20 °) is less than 15. In FIG. 1 (B), the rolling texture in which the average value of the orientation density of the region surrounded by the dotted line (φ1 = 75 ° to 90 °, Φ = 20 ° to 40 °, φ2 = 35 °) is less than 15. have. FIG. 1A shows a crystal orientation distribution chart in which the average value of the former orientation density is 8, and FIG. 1B shows the average value of the latter orientation density of 4.

  In the present invention, the copper plate material used for the insulating substrate is in the range of φ1 = 75 ° to 90 °, φ = 20 ° to 40 °, φ2 = 35 ° in the crystal orientation distribution function obtained from the texture analysis by EBSD. The average value of the orientation density in 0.1 is less than 0.1 and less than 15.0, and the average value of the orientation density in the range of φ1 = 20 ° to 40 °, φ = 55 ° to 75 °, φ2 = 20 ° is 0. It has a rolling texture of 1 or more and less than 15.0. As described above, by appropriately controlling the orientation density, the copper plate material suppresses the growth of crystal grains during heat treatment at a high temperature (for example, 700 ° C. or higher) and exhibits an excellent heat resistance characteristic. When the average value of the orientation density in the range of φ1 = 75 ° to 90 °, φ = 20 ° to 40 °, φ2 = 35 ° is 15.0 or more, the crystal orientation control is not sufficient, and thus the high temperature (for example, 700 ° C.). In the above heat treatment, the growth of crystal grains cannot be suppressed, resulting in poor heat resistance. Therefore, the resistance against the load due to the thermal expansion applied to the insulating substrate may increase, and the insulating substrate may be deformed or the ceramic substrate and the copper plate material may be separated from each other. Also, when the average value of the orientation density in the range of φ1 = 20 ° to 40 °, Φ = 55 ° to 75 °, φ2 = 20 ° is 15.0 or more, similarly, the crystal orientation control is not sufficient, and therefore the heat resistance is high. Inferior in characteristics. Therefore, the resistance against the load due to the thermal expansion applied to the insulating substrate may increase, and the insulating substrate may be deformed or the ceramic substrate and the copper plate material may be separated from each other. In addition, the average value of the orientation density in the range of φ1 = 75 ° to 90 °, φ = 20 ° to 40 °, φ2 = 35 °, φ1 = 20 ° to 40 °, φ = 55 ° to 75 °, φ2 = 20. Each lower limit of 0.1 of the average value of the orientation density in the range of ° is defined as the minimum value of the orientation density that can be analyzed in the texture analysis by EBSD.

[Average grain size]
The average crystal grain size of the copper plate material used for the insulating substrate of the present invention is 50 μm or more and 400 μm or less, preferably more than 100 μm and 400 μm or less. If the average crystal grain size is less than 50 μm, the crystal orientation cannot be sufficiently controlled, and the heat resistance will be poor. On the other hand, when the average crystal grain size exceeds 400 μm, sufficient tensile strength and elongation cannot be obtained, and the resistance to the load due to thermal expansion applied to the insulating substrate increases, resulting in deformation of the insulating substrate and between the ceramic substrate and the copper plate material. Peeling may occur. Further, at the interface between the copper plate material and the ceramic substrate, defects (voids) are likely to occur at locations where the crystal grain boundaries of the copper plate material contact the interface. When the average crystal grain size is 100 μm or less, the crystal grain boundaries of the copper plate material that comes into contact with the ceramic substrate may remarkably increase and the bonding strength may decrease. Therefore, the average crystal grain size is preferably larger than 100 nm. The average crystal grain size can be measured by EBSD analysis on the RD surface of the copper plate material, and for example, the average grain size of all crystal grains in the measurement range can be defined as the average crystal grain size. The average crystal grain size of the first copper plate material and the average crystal grain size of the second copper plate material may be the same or different, but from the viewpoint of production efficiency, they are the same. Is preferred.

[Thickness]
The thickness (plate thickness) of the first copper plate material and the second copper plate material is not particularly limited, but is preferably 0.05 mm to 7.0 mm, and 0.1 mm to 4.0 mm. Is more preferable. The thickness of the first copper plate material and the thickness of the second copper plate material may be the same or different, but when the volume of each copper plate material is greatly different in the bonding heat treatment and the heat cycle test. The plate warp may occur due to the difference in the amount of thermal expansion. Therefore, it is desirable to appropriately combine the plate thicknesses according to the circuit design of the insulating substrate.

[Characteristic]
(Tensile strength)
The tensile strength of the copper plate material is preferably 210 MPa or more and 250 MPa or less. If the tensile strength is less than 210 MPa, the strength required in recent years is not sufficient. On the other hand, when the tensile strength exceeds 250 MPa, elongation and workability tend to be reduced.

(Stretch)
The elongation of the copper plate material is preferably 25% or more and less than 50%. When the elongation is less than 25%, the insulating substrate may be deformed, the ceramic substrate and the copper plate material may be separated from each other, or the like due to the load stress applied to the insulating substrate due to thermal expansion. On the other hand, if the elongation exceeds 50%, the strength tends to be insufficient.

  The electrical conductivity of the copper plate material is preferably 95% IACS or more. When the electric conductivity is less than 95%, the thermal conductivity is lowered, and as a result, excellent heat dissipation characteristics tend not to be obtained.

  Next, an example of the method of manufacturing the insulating substrate of the present invention will be described.

[Insulating substrate manufacturing method]
The method for manufacturing an insulating substrate of the present invention includes an annealing step [step A], a cold rolling step [step B], and a joining step [step C]. By performing the processing in these steps in this order, the insulating substrate of the present invention in which the first copper plate material, the ceramic substrate, and the second copper plate material are joined can be obtained.

  First, in the annealing step [step A], a material to be rolled manufactured from a copper material having the above-described composition, that is, a material to be a first copper sheet material, which is a first material to be rolled, and a material to be a second copper sheet material. For the second material to be rolled, the temperature rising rate is 10 ° C / sec to 50 ° C / sec, the reached temperature is 250 ° C to 600 ° C, the holding time is 10 sec to 3600 sec, and the cooling rate is 10 ° C / sec. Annealing is performed under the condition of -50 ° C / sec. In the annealing step [step A], if the annealing condition is out of the above-specified range, coarsening of the average crystal grain size of the obtained copper plate material and insufficient control of the crystal orientation are caused, and as a result, the heat resistance of the insulating substrate is increased. It tends to be inferior. For example, when the reached temperature is too high or the temperature rising rate is too slow, the crystal orientation cannot be sufficiently controlled, and the orientation in the range of φ1 = 75 ° to 90 °, φ = 20 ° to 40 °, φ2 = 35 ° The average value of the density tends to be remarkably high. Further, if the reached temperature is too low, the strain is not relaxed in the annealing process, and the strain before the joining heat treatment also increases together with the subsequent cold rolling. Therefore, even if the rolling texture is within the specified range, recrystallization may be promoted and the crystal grains may become coarse.

  In the cold rolling step [step B], after the annealing step ([step A]), the first rolled material that is the material of the first copper plate material and the second rolled material that is the material of the second copper plate material. Cold rolling is performed at a total working rate of 10 to 65% with the rolled material. In the cold rolling step [Step B], if the cold rolling conditions are out of the range specified above, coarsening of the average crystal grain size of the obtained copper sheet material and insufficient control of the crystal orientation are caused, resulting in heat resistance of the insulating substrate. Tend to be inferior. For example, when the total processing rate is extremely high, the crystal orientation cannot be sufficiently controlled, and the average value of the orientation density in the range of φ1 = 20 ° to 40 °, φ = 55 ° to 75 °, φ2 = 20 ° is extremely high. Tends to become. On the other hand, if the total processing rate is too low, the crystal grain growth may not be suppressed and the crystal grains may become coarse.

  In the joining step [step C], after the cold rolling step ([step B]), the first rolled material, which is the material of the first copper plate material, is attached to one surface of the ceramic substrate and the other surface of the ceramic substrate. And a second material to be rolled, which is a material of the second copper plate material, are joined to each other via a brazing material such as Ag-Cu-Ti system, and the first copper plate material and the second copper plate material are respectively joined. A bonded insulating substrate is formed. The joining step [step C] is a first heat treatment in which a heat treatment is performed under the conditions of a temperature rising rate of 10 ° C./second to 100 ° C./second, an ultimate temperature of 400 ° C. to 600 ° C., and a holding time of 10 seconds to 300 seconds. And a second heat treatment for performing heat treatment under conditions of a temperature rising rate of 10 ° C./sec to 100 ° C./sec, an ultimate temperature of 750 ° C. to 850 ° C., and a holding time of 100 seconds to 7200 seconds. In the joining step [step C], if the joining conditions are out of the above-specified range, coarsening or excessive miniaturization of the average crystal grain size of the obtained copper sheet material and insufficient control of the crystal orientation are caused, resulting in insulation. The heat resistance of the substrate tends to be poor. For example, when the temperature rising rate of the first heat treatment and the second heat treatment is too fast, the crystal orientation cannot be sufficiently controlled, and φ1 = 75 ° to 90 °, Φ = 20 ° to 40 °, and φ2 = 35 °. The average value of the orientation density in the range tends to be extremely high. On the other hand, if the temperature reached by the first heat treatment is too low, the strain due to cold rolling is not relaxed even if the rolling texture is within the specified range. Therefore, in the second heat treatment, recrystallization is promoted by strain, and the crystal grains may be coarsened. Further, if the temperature reached by the second heat treatment is too high, the crystal grain growth may not be suppressed and the crystal grains may become coarse. On the other hand, when the temperature reached by the second heat treatment is too low, the interface between the copper plate material and the ceramic substrate is not activated, and it becomes difficult to satisfactorily bond them.

[Method of manufacturing rolled material]
In the method for manufacturing an insulating substrate of the present invention, the first rolled material and the second rolled material used in the annealing step [step A] may be rolled materials manufactured from the copper raw material having the above-described composition. However, it is not particularly limited. Such a material to be rolled can be manufactured, for example, through the following steps. Hereinafter, an example of a method for manufacturing a rolled material that can be used in the insulating substrate annealing step [step A] of the present invention will be described.

  The copper plate material before being joined to the ceramic substrate that constitutes the insulating substrate of the present invention, that is, the first rolled material that becomes the first copper plate material and the second rolled material that becomes the second copper plate material (hereinafter , The first rolled material and the second rolled material are also simply referred to as “rolled material”.), For example, a melting / casting step [step 1], a homogenizing heat treatment step [step 2 ], Hot rolling step [step 3], cooling step [step 4], chamfering step [step 5], first cold rolling step [step 6], first annealing step [step 7], second cold step A process including a rolling process [process 8], a second annealing process [process 9], a finish rolling process [process 10], a final annealing process [process 11], and a surface oxide film removing process [process 12] is sequentially performed. .

  First, in the melting / casting step [step 1], a copper material is melted and cast to obtain an ingot. The copper material has a total content of metal components selected from Al, Be, Cd, Mg, Pb, Ni, P, Sn and Cr of 0.1 to 2.0 ppm, and a copper content of 99.96 mass% or more. Has a composition that is In the homogenizing heat treatment step [Step 2], the obtained ingot is subjected to homogenizing heat treatment at a holding temperature of 700 to 1000 ° C. and a holding time of 10 minutes to 20 hours. In the hot rolling step [Step 3], hot rolling is performed so that the total processing rate is 10 to 90%. In the cooling step [step 4], rapid cooling is performed at a cooling rate of 10 ° C./second or more. In the chamfering step [step 5], both sides of the cooled material are chamfered by about 1.0 mm. As a result, the oxide film on the surface of the obtained plate material is removed.

  In the first cold rolling step [Step 6], cold rolling is performed a plurality of times so that the total processing rate is 75% or more.

  In the first annealing step [step 7], the temperature rising rate is 1 to 100 ° C / sec, the ultimate temperature is 100 to 500 ° C, the holding time is 1 to 900 seconds, and the cooling rate is 1 to 50 ° C / sec. Heat treatment is performed under the conditions.

  In the second cold rolling step [Step 8], cold rolling is performed so that the total working rate is 60 to 95%.

  In the second annealing step [step 9], the temperature rising rate is 10 to 100 ° C / sec, the ultimate temperature is 200 to 550 ° C, the holding time is 10 to 3600 seconds, and the cooling rate is 10 to 100 ° C / second. Heat treatment is performed under the conditions.

  In the finish rolling step [step 10], cold rolling is performed so that the total working rate is 10 to 60%. In the final annealing step [Step 11], heat treatment is performed under the condition that the ultimate temperature is 125 to 400 ° C. In the surface oxide film removing step [Step 12], pickling and polishing are performed for the purpose of removing the oxide film and cleaning the surface of the obtained plate material. The processing rate R (%) in the rolling step is defined by the following formula. In this way, the material to be rolled, which is a raw material for the copper plate material, can be manufactured.

R = (t ₀ −t) / t ₀ × 100
In the formula, t ₀ is the plate thickness before rolling, and t is the plate thickness after rolling.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited thereto.

(Examples 1 to 11 and Comparative Examples 1 to 17)
First, two 1.0 mm-thick materials to be rolled (test materials) having predetermined composition as shown in Table 1 were prepared, and each of them was made into a first material to be rolled and a second material to be rolled. It was made of wood. Further, a 0.5 mm-thick ceramic substrate formed by using silicon nitride as the ceramic material was used.

  Next, each of the rolled materials produced as described above to be a copper plate material was annealed under the conditions shown in Table 2 [Step A]. After the annealing treatment, cold rolling was performed on each of the obtained rolled materials at the total working rate shown in Table 2 (that is, the working rate of the first rolled material and the second rolled material as a whole). [Step B]. After the cold rolling, for each of the obtained rolled materials, a first rolled material corresponding to the first copper plate material was formed on one surface of the ceramic substrate, and a second copper plate material was formed on the other surface of the ceramic substrate. Corresponding second materials to be rolled were respectively joined through Ag-Cu-Ti based brazing materials to produce an insulating substrate in which the first copper plate material and the second copper plate material were respectively joined [step C]. In [Step C], the heat treatment was performed under the conditions of the first heat treatment and the second heat treatment shown in Table 2. Through the above steps, an insulating substrate as a sample was manufactured.

<Measurement method and evaluation method>
[Quantitative analysis of copper plate materials]
The GDMS method was used for the quantitative analysis of each produced copper plate material. In each example and each comparative example, VG-9000 manufactured by VG Scientific was used for analysis. Table 1 shows the content (ppm) of Al, Be, Cd, Mg, Pb, Ni, P, Sn and Cr and the content of Cu (mass%) contained in each copper plate material. In addition, each copper plate material may contain unavoidable impurities. The blank part in Table 1 means that the corresponding metal component was 0 ppm. Moreover, when the measured value by the GDMS method was less than 0.1 ppm, the content of the metal component was set to 0 ppm.

<Orientation density of copper plate material>
The EBSD method was used for the orientation density analysis of the rolling texture of each copper plate material peeled from each insulating substrate as a sample. In the EBSD measurement of each example and each comparative example, a measurement sample surface containing 200 or more crystal grains was measured. The measurement area of the measurement sample surface and the scan step were determined according to the size of the crystal grains of the test material. To analyze the crystal grains after the measurement, analysis software OIM Analysis (trade name) manufactured by TSL was used. The information obtained in the analysis of crystal grains by the EBSD method includes information up to a depth of several tens nm where the electron beam penetrates into the test material. The measurement location in the plate thickness direction was near the position ⅛ to ½ times the plate thickness t from the surface of the test material.

[Average grain size of copper plate]
The average crystal grain size of each copper plate material peeled from each insulating substrate as a sample was measured by EBSD measurement on the rolled surface on a measurement sample surface containing 200 or more crystal grains. In the analysis of the measurement results, the average crystal grain size was calculated from all the crystal grains in the measurement range. The analysis software OIM Analysis (trade name) manufactured by TSL was used for the analysis of the crystal grain size. The information obtained in the crystal grain analysis by EBSD includes information up to a depth of several tens of nm in which the electron beam penetrates the test material. The measurement location in the plate thickness direction was near the position ⅛ to ½ times the plate thickness t from the surface of the test material. When the average crystal grain size was in the range of 50 μm or more and 400 μm or less, it was evaluated that the crystal grains were finely refined.

[Electrical conductivity of copper plate (EC)]
The electrical conductivity of each copper plate material peeled from each insulating substrate as a sample was measured using a sigma tester (IACS% measurement using eddy current). The case where the electrical conductivity of each copper plate material was 95% IACS or more was evaluated as “good”, and the case of less than 95% IACS was evaluated as “poor”.

[Tensile strength of copper plate]
The copper plate material was peeled from each insulating substrate as a sample, and the cut-out test piece was measured according to JIS Z2241 and the average value was shown. The case where the tensile strength of the copper plate material was 210 MPa or more was evaluated as “good”, and the case of less than 210 MPa was evaluated as “poor”.

[Elongation of copper plate material]
The tensile strength was measured according to JIS Z2241 and the average value was shown. The case where the elongation of the copper plate material was 25% or more was evaluated as "good", and the case of less than 25% was evaluated as "poor".

[Heat resistance of insulating substrate]
A heat cycle test was performed in which each insulating substrate sample was subjected to 1200 cycles under the conditions of -40 ° C to 250 ° C (1 cycle: -40 ° C: 30 minutes / 250 ° C: 30 minutes). After the heat cycle test, it was visually observed whether cracks were generated in the ceramic substrate. The case where the crack did not occur was evaluated as “◯”, and the case where the crack occurred was evaluated as “x”.

  Table 3 shows the results of the orientation density, average crystal grain size, electrical conductivity, tensile strength, elongation of the copper plate material and the heat resistance characteristics of the insulating substrate.

  As shown in Tables 1 to 3, in Examples 1 to 11, the manufacturing conditions of the insulating substrate, the component composition of the copper plate material forming the insulating substrate, the orientation density, and the average crystal grain size are all within appropriate ranges. Therefore, an insulating substrate having excellent heat resistance was obtained. In particular, in Examples 1 to 5 and 7 to 11, the electrical conductivity, tensile strength, and elongation of the copper plate material provided in the insulating substrate were all good. Although not shown in Table 2, in Example 5, since the average crystal grain size was smaller than 100 μm, it was observed that the bonding strength tended to be lower than in other Examples.

  On the other hand, in Comparative Examples 1 to 17, since one or both of the manufacturing conditions of the insulating substrate and the component composition of the copper plate material forming the insulating substrate are out of the appropriate range, both or one of the orientation density and the average crystal grain size is It was out of the proper range, and further, in the heat cycle test of the insulating substrate, the occurrence of cracks was observed in all cases.

  As described above, the insulating substrate of the present invention formed by using the copper plate material in which the component composition, the orientation density and the average crystal grain size are strictly controlled exhibits excellent heat resistance, so that the load stress of the entire insulating substrate is And the resistance to the load due to thermal expansion is increased. As a result, the deformation of the insulating substrate caused by the difference in thermal expansion coefficient between the copper plate material and the ceramic substrate can be suppressed, and further, the separation between the ceramic substrate and the copper plate material, that is, the deterioration of the bondability can be suppressed.

Claims (7)

An insulating substrate in which a ceramic substrate, a first copper plate material formed on one surface of the ceramic substrate, and a second copper plate material formed on the other surface of the ceramic substrate are joined together,
The first and second copper sheet materials have a total content of metal components selected from Al, Be, Cd, Mg, Pb, Ni, P, Sn, and Cr of 0.1 to 2.0 ppm, and copper content. The composition has a composition of 99.96 mass% or more, and the crystal orientation distribution function obtained from the texture analysis by EBSD of the surfaces of the first and second copper sheet materials is Euler angles (φ1, φ, φ2). ), The average value of the orientation density in the range of φ1 = 75 ° to 90 °, φ = 20 ° to 40 °, φ2 = 35 ° is 0.1 or more and less than 15.0, and φ1 = 20 °. Has a rolling texture in which the average value of the orientation density in the range of -40 °, Φ = 55 ° to 75 °, and Φ2 = 20 ° is 0.1 or more and less than 15.0, and
An insulating substrate, wherein the first and second copper plate materials have an average crystal grain size of 50 μm or more and 400 μm or less.   The insulating substrate according to claim 1, wherein the average crystal grain size of the first and second copper plate materials is more than 100 μm and 400 μm or less.   The insulating substrate according to claim 1, wherein the ceramic substrate is formed using a ceramic material containing at least one of aluminum nitride, silicon nitride, alumina, and a compound of alumina and zirconia as a main component.   The insulating substrate according to any one of claims 1 to 3, wherein the tensile strength of the first and second copper plate materials is 210 MPa or more and 250 MPa or less.   The insulating substrate according to any one of claims 1 to 4, wherein the first and second copper sheet materials have an elongation of 25% or more and less than 50%.   The insulating substrate according to claim 1, wherein the first and second copper plate materials have a conductivity of 95% IACS or more. A method for manufacturing an insulating substrate according to any one of claims 1 to 6, comprising:
With respect to the first rolled material that is the material of the first copper sheet and the second rolled material that is the material of the second copper sheet, the heating rate is 10 ° C / sec to 50 ° C / sec, An annealing step of performing an annealing treatment under the conditions of an ultimate temperature of 250 ° C to 600 ° C, a holding time of 10 seconds to 3600 seconds, and a cooling rate of 10 ° C / second to 50 ° C / second;
A cold rolling step of performing, after the annealing step, cold rolling at a total working rate of the first rolled material and the second rolled material of 10 to 65%;
After the cold rolling step, the first rolled material is bonded to one surface of the ceramic substrate, the second rolled material is bonded to the other surface of the ceramic substrate through a brazing material, A bonding step of forming an insulating substrate in which the first copper plate material and the second copper plate material are respectively bonded,
In the joining step, a first heat treatment is performed in which a heat-up rate is 10 ° C./sec to 100 ° C./sec, an ultimate temperature is 400 ° C. to 600 ° C., and a holding time is 10 seconds to 300 seconds; A second heat treatment, which is a heat treatment under the conditions of a speed of 10 ° C./sec to 100 ° C./sec, an ultimate temperature of 750 ° C. to 850 ° C., and a holding time of 100 seconds to 7200 seconds, and manufacturing an insulating substrate. Method.

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