Joined body manufacturing method and ceramic circuit substrate manufacturing method

Abstract

A joined body manufacturing method according to an embodiment of the present invention comprises a laminating step, a disposing step, and a joining step. The laminating step involves laminating a metal plate and a ceramic substrate via an active metal brazing material to thereby produce a laminate. The disposing step involves disposing, on a plane of the laminate, a weight having a heat capacity per 1 kg of 600 J / K or less and a thermal conductivity of 15W / m･K or more. The joining step involves joining, by heating in a continuous furnace, the laminate on which the weight is disposed to thereby manufacture a joined body.

Description

Method for manufacturing a bonded body and method for manufacturing a ceramic circuit board

[0001] The embodiments described later generally relate to methods for manufacturing bonded bodies and methods for manufacturing ceramic circuit boards.

[0002] In ceramic circuit boards, the ceramic substrate and the copper plate are joined via a brazing layer. The brazing layer uses an active metal brazing material containing Ag, Cu, Sn, Ti, etc. The joining method using active metal brazing material is called active metal joining. In active metal joining, the reaction between Ti in the brazing material and the ceramic substrate is promoted by heating and joining in a vacuum. For example, when a silicon nitride substrate is used as the ceramic substrate, the Ti contained in the active metal brazing material reacts with the silicon nitride when the brazing material melts, forming a dense and strong interfacial reaction layer for joining. To prevent oxidation of Ti at high temperatures, batch furnaces in high vacuum furnaces or continuous furnaces filled with an inert atmosphere are used. Conventionally, batch furnaces have been used for joining in a vacuum.

[0003] Batch furnaces require a vacuum, resulting in long processing times. On the other hand, continuous processing using a continuous furnace allows for high-speed heating and cooling, thus offering higher productivity compared to batch furnaces. However, to further improve the productivity of joining processes using a continuous furnace, it is necessary to rapidly heat and cool the laminates when joining them. For example, international publication number WO2022-244769 (Patent Document 1) discloses a method for manufacturing joined products with a good yield using a continuous furnace by specifying the average heating rate, the holding time of the joining temperature, and the cooling rate.

[0004] International Publication Number WO2022 / 244769

[0005] The method described in Patent Document 1 can improve productivity. However, the resulting joints would warp, which degraded the quality of the joints.

[0006] The problem that this invention aims to solve is to provide a manufacturing method that can produce high-quality joined products while maintaining high productivity in a joining process using a continuous furnace.

[0007] To solve the above problems, the method for manufacturing a joined body according to the embodiment comprises a lamination step, an arrangement step, and a joining step. The lamination step involves laminating a metal plate and a ceramic substrate via an activated metal brazing material to produce a laminate. The arrangement step involves placing weights having a heat capacity of 600 J / K or less per 1 kg and a thermal conductivity of 15 W / m·K or more on the plane of the laminate. The joining step involves heating and joining the laminate with the weights placed on it using a continuous furnace to produce a joined body.

[0008] A cross-sectional view showing an example of a laminate produced in the method for manufacturing a bonded body according to the embodiment. A partial cross-sectional view showing an example of a continuous furnace used in the method for manufacturing a bonded body according to the embodiment and a laminate. A plan view showing an example of the outer peripheral support area and the center of gravity support area of ​​a laminate in the method for manufacturing a bonded body according to the embodiment. A plan view showing an example of a weight (solid plate type) placed on the laminate in the method for manufacturing a bonded body according to the embodiment. A cross-sectional view showing an example of a ceramic circuit board manufactured in the method for manufacturing a ceramic circuit board according to the embodiment. Embodiment

[0009] The manufacturing methods for the bonded body and the ceramic circuit board of the embodiment will be described below with reference to the drawings.

[0010] Figure 1 shows a cross-sectional view of an example of a laminate produced in the manufacturing method of a joined body according to the embodiment. Figure 2 shows a partial cross-sectional view of an example of a continuous furnace and a laminate used in the manufacturing method of a joined body according to the embodiment. Reference numeral 1 indicates the laminate, reference numeral 2 indicates the metal plate, reference numeral 3 indicates the brazing layer, and reference numeral 4 indicates the ceramic substrate. Reference numeral 5 indicates the setter, reference numeral 6 indicates the weight, and reference numeral 10 indicates the continuous furnace. The brazing layer 3 is an activated metal brazing material. The laminate 1 includes a metal plate 2, a brazing layer 3, and a ceramic substrate 4.

[0011] The method for manufacturing a joined body according to this embodiment comprises a lamination step, an arrangement step, and a joining step. The lamination step involves laminating a metal plate 2 and a ceramic substrate 4 via a brazing material layer 3 to produce a laminate 1. The arrangement step involves placing a weight 6 having a heat capacity of 600 J / K or less per 1 kg and a thermal conductivity of 15 W / m·K or more on the plane of the laminate 1. The joining step involves heating and joining the laminate 1 on which the weight 6 is placed using a continuous furnace 10 to produce a joined body.

[0012] The laminate 1 has a metal plate 2 and a ceramic substrate 4 separated by a brazing layer 3. The laminate 1 has a laminated structure of three or more layers, consisting of the ceramic substrate 4, the brazing layer 3, and the metal plate 2. The laminate 1 may be a three-layer laminate, or, as shown in Figure 1, a five-layer structure in which metal plates 2 are joined to both sides of the ceramic substrate 4 via the brazing layer 3. The number of layers in the laminate 1 may also be increased as needed. Furthermore, the planar shape of the laminate 1 may be not only a square, but also a rectangle, parallelogram, or circle. The metal plate 2 may be a solid plate or have a patterned shape.

[0013] The laminate 1 is joined and heated by placing a weight 6 on the flat surface of the laminate 1. Placing the weight 6 on the flat surface of the laminate 1 applies an appropriate load to the joining surface. This ensures that the joining surface and the brazing material make reliable contact, leading to uniform brazing within the joining surface. In the joining process in a continuous furnace, it is not possible to load a large quantity of laminate 1 at once. Therefore, it is preferable to place the weight 6 on the flat surface of a single laminate 1 or a small quantity of laminate 1.

[0014] The weights 6 on the flat surface of the laminate 1 may be placed directly on the metal plate 2, or a setter 5 may be placed between them. Alternatively, as shown in Figure 2, a setter 5 may be placed between the belt conveyor 7 (frame) and the laminate 1. The material of the setter 5 is preferably alumina, boron nitride, silicon nitride, silicon carbide, or carbon. The setter 5 serves to prevent the laminate 1 and the weights 6 from sticking together and to prevent soiling.

[0015] Hereinafter, the laminate 1 that has been heat-bonded will be referred to as the bonded body. The weight 6 used in the manufacturing method of the bonded body according to this embodiment, which is placed on the plane of the laminate 1, has a heat capacity of 600 J / K or less per 1 kg and a thermal conductivity of 15 W / m·K or more. If the thermal conductivity of the weight 6 is less than 15 W / m·K, the transfer of heat to the laminate 1 (bonded body) during heating and cooling will be slow. Also, if the heat capacity of the weight 6 exceeds 600 J / K, the heat dissipation will be poor and the cooling rate will be slow.

[0016] Therefore, by setting the heat capacity of the weight 6 to 600 J / K or less per 1 kg and its thermal conductivity to 15 W / m·K or more, the thermal responsiveness of the laminate 1 and its associated weight 6 is improved, allowing the weight 6 and laminate 1 to heat up and cool down more quickly. A faster heating rate of the laminate 1 helps to reduce bonding defects. A faster cooling rate allows the bonded body 1 to be removed from the furnace when it is completely cooled, thereby reducing oxidation of the metal plate 2 and warping of the bonded body. In addition, this makes it possible to shorten the furnace length.

[0017] Therefore, the weight 6 has a heat capacity of 600 J / K or less per 1 kg and a thermal conductivity of 15 W / m·K or more. While there are no upper or lower limits, if the heat capacity is too small and the thermal conductivity is too high, the cooling rate of the substrate will become too large, causing significant residual stress due to the difference in thermal expansion coefficients, leading to crack formation and deformation of the joint. Therefore, it is preferable that the lower limit of the heat capacity per 1 kg be 120 J / K or more. The upper limit of the thermal conductivity is preferably 200 W / m·K or less. More preferably, the heat capacity per 1 kg of the weight 6 is 120 J / K or more and 400 J / K or less. The thermal conductivity of the weight 6 is preferably 50 W / m·K or more and 200 W / m·K or less. Examples of materials for the weight 6 that satisfy the above conditions include stainless steel, tungsten (W), molybdenum (Mo), or materials mainly composed of these. Preferably, it is more preferable to use tungsten or molybdenum.

[0018] The density of the weight 6 used in the manufacturing method of the assembled body according to this embodiment is 7.0 g / cm³. ３It is preferable that the above conditions are met. Furthermore, there is no upper limit to the density of the weight 6, but it is 19.0 g / cm³. ３ It is more preferable that the density of the weight 6 is 7.0 g / cm³. ３ 19.0g / cm or more ３ The following conditions can improve heat dissipation.

[0019] Since the weight 6 may deform or crack with repeated use, sufficient room temperature rigidity is required. For this reason, it is preferable that the Young's modulus of the weight 6 that can withstand handling at temperatures below 100°C is 50 GPa or higher, and that its 0.2% proof stress is 200 MPa or higher. The 0.2% proof stress is the stress at which the strain reaches 0.2%.

[0020] When laminate 1 is heat-bonded, the bonded body will experience not only uniaxial warping, such as warping along the long sides and diagonals of the plane, but also twisting, saddle-shaped warping, and localized irregularities on the plane. Warping (amount of warping) refers to the difference between the minimum height and the maximum height across the entire plane of the bonded body, including all of these.

[0021] It is preferable that the amount of warping along the long side of the bonded body and the amount of warping across the entire substrate are 2 mm or less. Furthermore, it is more preferable that the amount of warping is 1.5 mm or less and 1 mm or less, respectively. The bonded body described later may be made from a large substrate for multiple pieces. When a large substrate is divided to obtain multiple bonded bodies, it is preferable that the average amount of warping across the entire surface of each bonded body is within the range of 1.5 mm or less. Furthermore, it is preferable that the average amount of warping is 1 mm or less.

[0022] In the joining process using the continuous furnace 10, the placement of the weights 6 on the plane of the laminate 1 only needs to be done before the heating of the continuous furnace 10. Therefore, the weights 6 may be placed on the laminate 1 before heating and then transport may be started, or the weights 6 may be placed on the laminate 1 while it is being transported before heating.

[0023] The method for measuring the thermal conductivity of weight 6 shall conform to JIS H-7801 (2005) Laser flash method for metals. The method for testing the Young's modulus of weight 6 shall conform to JIS Z-2280 (1993). The density of weight 6 shall be measured using the Archimedes method with a material block of the same specifications as the one used to fabricate weight 6. The heat capacity of weight 6 shall be determined using a DSC curve.

[0024] A DSC curve is obtained by measuring the peaks of endothermic and exothermic reactions using a differential scanning calorimeter (DSC). A peak in the negative direction indicates an endothermic reaction, and a peak in the positive direction indicates an exothermic reaction. The method for measuring the DSC curve of weight 6 involves cutting a material block so that the sample weighs 100g, and using a DSC measuring device to linearly extrapolate the measured specific heat values ​​at 100°C, 200°C, 300°C, and 400°C to determine the specific heat of each material at room temperature. The heat capacity was calculated by multiplying the obtained specific heat by the weight of the weight (1 kg). The DSC measuring device used shall be a NETZSCH TGA-DSC simultaneous thermal analyzer STA449-F3-Jupiter or a device with equivalent performance.

[0025] The 0.2% yield strength is calculated by conducting a tensile test in accordance with JIS Z 2241 (2011), creating a strain curve, drawing a straight line parallel to the elastic region, and finding the intersection point of the straight line and the strain curve.

[0026] In the method for manufacturing a bonded body according to the embodiment, the pressing force (surface pressure) applied to the laminated body 1 by the weight 6 is preferably within the range of 10 Pa to 500 Pa per unit bonding area. Therefore, it is preferable to set the weight of the weight 6 according to the size of the laminated body 1 so that a surface pressure of 10 Pa to 500 Pa is applied to the laminated body 1.

[0027] If the surface pressure is less than 10 Pa, the load is too small, and the joint surface is prone to shifting due to vibration and lubrication of the brazing liquid phase during transport of the laminate 1 in the continuous furnace 10. On the other hand, if the surface pressure exceeds 500 Pa, the load is too large, causing the brazing liquid phase to seep out from the joint surface, potentially resulting in a poor joint or fusion with other components, making it impossible to recover the joint. Therefore, more preferably, the surface pressure is 30 Pa or more and 200 Pa or less.

[0028] Furthermore, in a plan view of the laminate 1 from the weight 6 side, it is preferable that the ratio of the area AW of the weight 6 to the area AS of the laminate 1, AW / AS, is within the range of 0.6 to 1.2 as shown in the following equation (1): 0.6 ≤ AW / AS ≤ 1.2 …(1) When the area AW of the weight 6 is larger than the area AS of the laminate 1, pressure is applied to the entire laminate 1, so an appropriate load can be applied to the entire joint surface. As a result, the joint area ratio increases, and the joint strength can be improved.

[0029] The external dimensions and placement position of the weight 6 on the plane of the laminate 1 will now be described. When viewing the laminate 1 from the weight 6 side, it is preferable that the weight 6 be positioned so as to cover the outer perimeter support area, which is the area including the outer perimeter of the laminate 1, and the center of gravity support area, which is the area including the center of gravity. Figure 3 shows an example of a plan view of the outer perimeter support area and the center of gravity support area on the plane of the laminate 1. Reference numeral 11 denotes the outer perimeter support area, and reference numeral 12 denotes the center of gravity support area. Figure 3(A) shows the rectangular outer perimeter support area 11 and center of gravity support area 12 when the plane of the laminate 1 is rectangular, in a plan view of the laminate 1 from the weight 6 side. As shown in Figure 3(A), the outer perimeter support area 11 is the area between the outer perimeter and a rectangular frame formed by connecting four points 10% inward from the outer perimeter by straight lines (shown as a diagonal pattern in Figure 3(A)). In this case, the outer perimeter support area 11 is the area formed between the outer perimeter and the rectangular frame. The center of gravity support area 12 is the area within the rectangular frame (shown as a diagonal pattern in Figure 3(A)) formed by connecting four points outside the center of gravity (center in the case of a rectangle) of the laminated body 1 with straight lines, each point being 20% ​​of the length of the diagonal. In this case, the center of gravity support area 12 is the area within the rectangular frame.

[0030] Figure 3(B) shows a plan view of the laminate 1 from the weight 6 side, illustrating the circular outer perimeter support area 11 and the center of gravity support area 12 when the plane of the laminate 1 is circular. As shown in Figure 3(B), the outer perimeter support area 11 is the area between the outer perimeter and a circular frame formed inward from the outer perimeter by 10% of the diameter (illustrated with a diagonal line pattern in Figure 3(B)). In this case, the outer perimeter support area 11 is the area formed between the outer perimeter and the circular frame. The center of gravity support area 12 is the area within a circular frame formed outward from the center of gravity (the center in the case of a circle) by 20% of the diameter (illustrated with a diagonal line pattern in Figure 3(B)). In this case, the center of gravity support area 12 is the area within the circular frame. Examples have been given for the cases where the plane of the laminate 1 is rectangular and circular, but it is not limited to these cases. For example, the plane of the laminate 1 may be a quadrilateral, parallelogram, regular hexagon, or any other shape. If the plan view of the laminate 1 is symmetrical, a centroid support and an outer edge support can be set.

[0031] This makes it possible to reduce not only the warping along the long side of the plane of the joint, but also the warping across the entire plane of the joint.

[0032] The outer peripheral support area 11 preferably includes the outer periphery of the plane of the laminate 1. The weight 6 is preferably placed on the laminate 1 so as to be on a common plane that covers both the outer peripheral support area 11 and the center of gravity support area 12.

[0033] The weight 6 is preferably made from a single component, but may also be made from a combination of two or more components. When the weight 6 is made from a combination of two or more components, it is preferable that all of the two or more components be made from the same material. If the weight 6 is made from a single component, the arrangement of the weight 6 is simplified, which improves the mass production efficiency of the laminate 1.

[0034] Figure 4 shows a plan view of an example of a weight placed on a laminate in a manufacturing method of a bonded body according to an embodiment. Figure 4 shows a solid plate-type weight 13 among the weights 6. Although Figure 4 shows an example of the shape of the weight 13, it is not limited to this.

[0035] It is preferable that the parallelism of the contact surface of the weight 6 with the laminate 1 be 0.05 mm or less. This is because it is possible to increase the contact area between the brazing material layer 3 and the joining member. As a result, uniform brazing can be performed within the joining surface. It is preferable to measure the parallelism of the contact surface before and after the heat treatment process of the laminate 1. It is preferable that the weight 6 is not distorted after the heat treatment. Therefore, it is preferable that the parallelism before and after the heat treatment be 0.05 mm or less.

[0036] The parallelism of the contact surface was measured using a three-dimensional measuring machine as specified in JIS B 7440. The shape was measured across the entire contact surface, and the difference between the maximum and minimum values ​​was defined as the parallelism. All five randomly selected weights 6 used must satisfy this value. A Keyence VR-5000 one-shot 3D shape measuring machine was used to measure the contact surface. Furthermore, when the weights 6 are placed directly on the laminate 1, the parallelism of the contact surface between the weights 6 and the laminate 1 may affect the warping and distortion of the joint. From this point of view, it is preferable that the parallelism of the contact surface between the weights 6 and the laminate 1 be 0.05 mm or less.

[0037] The continuous furnace 10 shown in Figure 2 heats and cools the stacked body 1 while transporting it in the direction of the arrow on a belt conveyor 7. The continuous furnace 10 is also equipped with an exhaust pipe 8 and an inlet pipe 9 for gas injection and exhaust. Atmospheric gas and cooling gas are introduced into the continuous furnace 10 from the inlet pipe 9. The exhaust pipe 8 is for exhausting the gas introduced from the inlet pipe 9. Preferably, the exhaust pipe 8 has an exhaust blower with an exhaust capacity equal to the total amount of gas injected from the inlet pipe 9. Furthermore, it is preferable that the exhaust blower is located between 200°C and 500°C.

[0038] The joining process using the continuous furnace 10 has three sub-processes: a heating process, a heating and joining process, and a cooling process. The joining process also has two zones: a heating zone consisting of the heating and joining processes, and a cooling zone for the cooling process. Figure 2 illustrates a continuous furnace 10 using a belt conveyor system, but the structure of the continuous furnace 10 is not limited to this.

[0039] The continuous furnace 10 preferably has a structure in which TH / TC, which is the ratio of the time TH that the laminate 1 stays in the heating zone to the time TC that it stays in the cooling zone, is connected such that 0.7 or more and 1.5 or less as shown in the following formula (2). 0.7 ≦ TH / TC ≦ 1.5 …(2) Particularly when the conveyance speed is constant, it is preferable to satisfy the formula (2).

[0040] According to the method for manufacturing a joined body according to the embodiment, it is possible to shorten the temperature increase time and the temperature decrease time in the joining process as compared with the conventional method while preventing warping of the entire plane of the joined body and oxidation of the metal plate. Therefore, the time for the cooling zone can be shortened. Further, TH / TC may be the ratio with respect to the furnace length (distance). Further, the conveyance path of the laminate 1, which is the object to be heated, may be linear or curved. The conveyance path may be flat, or may have a slope (uphill or downhill). The conveyance path of the laminate 1 in the continuous furnace 10 is preferably linear and flat.

[0041] In the method for manufacturing a joined body according to the embodiment, the conveyance speed of the laminate 1 is preferably 50 mm / min or more and 300 mm / min or less. The conveyance speed is the moving speed of the laminate 1 when the laminate 1 is conveyed so as to sequentially perform the joining process, that is, the temperature increase process, the heat joining process, and the temperature decrease process. If the conveyance speed is too fast, the way heat is transferred to the laminate 1 becomes non-uniform, which may lead to poor joining. If the conveyance speed is too slow, the mass productivity of the joined body may decrease. Therefore, the conveyance speed is preferably 50 mm / min or more and 300 mm / min or less. The conveyance speed may be constant or may change midway. Preferably, it is a constant conveyance speed. More preferably, the conveyance speed is 100 mm / min or more and 150 mm / min or less.

[0042] In the method for manufacturing a joined body according to the embodiment, the temperature of the weight 6 when the laminate 1 is inserted into and taken out of the continuous furnace 10, for example, the upper surface temperature of the weight 6 is preferably 100°C or less. This is because if the joined body is taken out of the furnace while it has not cooled sufficiently, oxidation of the metal plate surface is likely to occur, or warping of the joined body may occur due to the generation of thermal stress.

[0043] The upper surface temperature of the weight 6 can be measured by bringing the terminals of a contact thermometer into contact with the upper surface of the weight 6 when the assembled body and the weight 6 have completely exited the continuous furnace 10, and recording the value after standing for 5 seconds. A FUSO FS-300S or a contact thermometer with equivalent performance should be used.

[0044] Examples of ceramic substrates 4 include silicon nitride substrates, aluminum nitride substrates, aluminum oxide substrates, and argil substrates. An argil substrate is a substrate made by mixing aluminum oxide and zirconium oxide.

[0045] The short side of the planar surface of the ceramic substrate 4 laminated on the laminate 1 may be a large substrate of 90 mm or more. By placing the weight 6 on the laminate 1, even if the laminate 1 is equipped with a relatively large ceramic substrate 4 with a short side of planar surface of 90 mm or more, the warping of the bonded body can be reduced using the manufacturing method of the embodiment.

[0046] The thickness of the ceramic substrate 4 is preferably 0.1 mm or more and 2 mm or less. If the thickness of the ceramic substrate 4 is less than 0.1 mm, the strength may be too low. If the thickness of the ceramic substrate 4 is greater than 2 mm, the ceramic substrate 4 may act as a thermal resistor, which may reduce the heat dissipation performance of the ceramic circuit board 16. For this reason, the thickness of the ceramic substrate 4 is preferably 0.1 mm or more and 2 mm or less, and more preferably 0.1 mm or more and 1 mm or less.

[0047] The silicon nitride substrate, as the ceramic substrate 4, preferably has a three-point bending strength of 500 MPa or more. Furthermore, the silicon nitride substrate preferably has a thermal conductivity of 60 W / m·K or more. By increasing the strength of the silicon nitride substrate, its thickness can be reduced. Therefore, the three-point bending strength of the silicon nitride substrate is preferably 500 MPa or more, and more preferably 650 MPa or more. The thickness of the silicon nitride substrate can be reduced to 0.40 mm or less, and more preferably 0.30 mm or less. However, the thickness of the silicon nitride substrate is not limited to 0.40 mm or less. The thickness of the ceramic substrate may be changed as needed.

[0048] The three-point bending strength of the aluminum nitride substrate as the ceramic substrate 4 is approximately 300 to 450 MPa. On the other hand, the thermal conductivity of the aluminum nitride substrate is 160 W / m·K or higher. Because the aluminum nitride substrate has low strength, a thickness of 0.60 mm or more is preferable. The aluminum oxide substrate as the ceramic substrate 4 has a three-point bending strength of approximately 300 to 450 MPa, but is inexpensive. The three-point bending strength of the argil substrate is high at approximately 550 MPa, but its thermal conductivity is approximately 30 to 50 W / m·K.

[0049] A silicon nitride substrate is preferred as the ceramic substrate 4. This is because silicon nitride substrates have high strength, allowing for excellent reliability even when thick copper plates are bonded to them.

[0050] Examples of metal plate 2 include copper plates, aluminum plates, iron alloy plates, and copper alloy plates. Furthermore, the copper plate is not limited to pure copper plates, but may also be a copper alloy plate. Examples of copper plates include those specified in JIS H 3100 (2018). JIS H 3100 (2018) corresponds to ISO 1337, etc. Among these, oxygen-free copper (copper purity of 99.96% by mass or higher) is preferred. Oxygen-free copper is a type of pure copper plate. The aluminum plate is not limited to pure aluminum plates, but may also be an aluminum alloy plate. Examples of aluminum plates include those specified in JIS H 4000 (2014). JIS H 4000 (2014) corresponds to ISO 209 (2007). Furthermore, metal plate 2 is preferably a copper plate because copper plates have a higher thermal conductivity than aluminum plates. Examples of iron alloy plates include stainless steel. Stainless steel is a type of iron alloy containing Cr. Stainless steel is designated as SUS according to JIS standards (Japanese Industrial Standards).

[0051] Furthermore, the thickness of the metal plate 2 is preferably 0.2 mm or more. By increasing the thickness of the metal plate 2, both heat dissipation and current conductivity can be improved. For this reason, the thickness of the metal plate 2 is preferably 0.2 mm or more, and more preferably 0.5 mm or more. There is no particular upper limit to the thickness of the metal plate 2, but it is preferably 10 mm or less. This is because if the metal plate 2 exceeds 10 mm, the burden of processing it into the desired shape may increase. Also, if the metal plate 2 is thicker than 3 mm, it may become difficult to perform the etching process described later. For this reason, if an etching process is performed, the thickness of the metal plate 2 is preferably 0.2 mm or more and 3 mm or less, and more preferably 0.5 mm or more and 2 mm or less. If an etching process is not performed, a metal plate (pattern plate) 2 processed into the desired shape is used.

[0052] The dimensions of the ceramic substrate 4 and the metal plate 2 may be the same or different. The dimensions of the ceramic substrate 4 and the metal plate 2 being the same means that the difference between the length of the ceramic substrate 4 and the length of the metal plate 2 is within ±2 mm.

[0053] Making the dimensions of the ceramic substrate 4 and the metal plate 2 the same improves the degree of freedom in pattern formation during the etching process. Furthermore, when the metal plate 2 is provided on both sides of the ceramic substrate 4, warping of the joint can be suppressed. Additionally, the degree of freedom in circuit pattern design during the etching process increases.

[0054] Furthermore, if the dimensions of the ceramic substrate 4 and the metal plate 2 are different, it is preferable to make the dimensions of the metal plate 2, which is joined to the front and back of the ceramic substrate 4, the same. This also helps to suppress the occurrence of warping of the joined body.

[0055] The bonded body may be used for multi-cavity production. Multi-cavity production is a method of dividing the bonded body into multiple parts to obtain smaller bonded bodies. For example, in the etching process following the bonding process, the bonded body, to which the circuit shape has been imprinted by etching, can be divided to obtain multiple ceramic circuit boards. With the bonding body manufacturing method according to the embodiment, even if the short side of the ceramic substrate is large, such as 90 mm or more, the amount of warping of the bonded body can be suppressed. Therefore, a bonded body suitable for multi-cavity production can be manufactured. Bonded bodies with a large amount of warping require straightening treatment, but with the bonding body manufacturing method according to the embodiment, the amount of warping of the bonded body can be reduced, making straightening treatment unnecessary.

[0056] An active metal brazing material is used for the brazing layer 3. The joining method using an active metal brazing material is called the active metal joining method. When the metal plate is a copper plate, the active metal is titanium (Ti). The brazing material preferably contains one or more components selected from Ag (silver), Cu (copper), Sn (tin), In (indium), and C (carbon) as components other than the active metal. Ag or Cu are components that form the base material of the brazing material. Sn or In have the effect of lowering the melting point of the brazing material. C has the effect of controlling the fluidity of the brazing material or controlling the structure of the joined layer by reacting with other components. Therefore, examples of components for the brazing material include Ag-Cu-Ti, Ag-Cu-Sn-Ti, Ag-Cu-Ti-C, Ag-Cu-Sn-Ti-C, Ag-Ti, Cu-Ti, Ag-Sn-Ti, Cu-Sn-Ti, Ag-Ti-C, Cu-Ti-C, Ag-Sn-Ti-C, and Cu-Sn-Ti-C. In may be used instead of Sn. Both Sn and In may be used. Low-melting-point metals such as Bi (bismuth), Sb (antimony), Ga (gallium), and Zn (zinc) may be used instead of Sn or In.

[0057] When the base material of the brazing material uses both Ag and Cu, the brazing material composition is 30% to 70% by mass of Ag, 10% to 45% by mass of Cu, and Ti (titanium) or TiH ２It is preferable to contain 1% to 15% by mass of titanium hydride. If Ag is not included, it is preferable to contain 35% to 85% by mass of Cu. With these brazing material compositions, the bonding temperature can be controlled to be between 550°C and 950°C, and the bonding temperature of brazing materials that do not contain Ag can be controlled to be between 700°C and 850°C. The brazing material composition may also contain 1% to 50% by mass of one or two of Sn (tin) or In (indium) as needed. Furthermore, the brazing material composition may also contain 0.1% to 2% by mass of C (carbon) as needed.

[0058] Furthermore, when the metal plate 2 is an aluminum plate, the active metal is silicon (Si). The brazing material components other than Si are aluminum. In other words, the active metal brazing material used when joining aluminum plates is an Al-Si brazing material. The Al-Si brazing material preferably contains Si in the range of 0.1% by mass or more and 30% by mass or less. In addition, it may also contain magnesium in the range of 0.01% by mass or more and 10% by mass or less in addition to Al and Si. The melting point of the brazing material is preferably 520°C or more and 700°C or less.

[0059] The composition ratio of the brazing material is calculated by considering the total amount of the raw materials to be mixed as 100% by mass. For example, if it is composed of three types of materials, Ag, Cu, and Ti, then Ag + Cu + Ti = 100% by mass. Also, Ag, Cu, TiH ２ When composed of four types of In, Ag + Cu + TiH ２ +In = 100 mass%. Also, when composed of five types of elements: Ag, Cu, Ti, Sn, and C, Ag + Cu + Ti + Sn + C = 100 mass%. Also, when composed of two types of elements: Al and Si, Al + Si = 100 mass%.

[0060] The melting point of the brazing material is preferably lower than the joining temperature. Furthermore, the melting point of the brazing material is preferably 850°C or lower. By lowering the melting point of the brazing material, the metal plate and ceramic substrate can be joined even if the heating and cooling rates are increased. A faster heating rate means a faster temperature rise from room temperature to the joining temperature. By lowering the melting point of the brazing material, the brazing material can be melted during the temperature rise process. This allows the joining process to begin during the heating step.

[0061] The lower limit of the melting point of the brazing material is not particularly limited, but it is preferably 520°C or higher. If the melting point is too low, the TCT characteristics may deteriorate. The mounting temperature using lead-free solder and Ag / Cu sintered bonding used for mounting semiconductors, heat sinks, and wiring is 250°C to 350°C. Ag / Cu sintered bonding is a sintered bonding method using one or two types of powder of Ag or Cu. In recent years, with the improvement of semiconductor device performance, the junction temperature has risen to about 170°C. It is thought that if performance is further improved, the junction temperature will reach 250°C. If the melting point of the brazing material is low, the brazing layer may melt at the junction temperature. For this reason, the melting point of the brazing material is preferably in the range of 520°C to 850°C. More preferably, it is between 680°C and 850°C.

[0062] The melting point of the brazing material can be determined by examining the DSC curve. The DSC curve measurement shall be performed using a temperature profile consisting of the heating and cooling processes of the joining process. According to the temperature profile, the heating process involves raising the temperature from room temperature to 500°C at a heating rate of 20°C / min, then raising it to 845°C at a heating rate of 20°C / min, and holding it at 845°C for 30 minutes. The cooling process involves lowering the temperature from 845°C to room temperature at a cooling rate of 20°C / min. The measurement shall be performed by dropping an appropriate amount of brazing material into an alumina container and using an Ar (argon) flow. It is necessary to prevent the brazing material from reacting with the atmosphere by measuring in an Ar atmosphere.

[0063] In the heating process of the DSC curve, the detection temperature of the largest endothermic peak within the temperature range of 520 °C or higher and 900 °C or lower is defined as the melting point. That the melting point of the brazing material is 850 °C or lower indicates that the largest endothermic peak is within the range of 520 °C or higher and 850 °C or lower. Also, for those with a melting point exceeding 850 °C, the largest endothermic peak is detected above 850 °C and up to 900 °C. Even if there is a peak in the negative direction below 520 °C, it is not necessary to count it as an endothermic peak. The endothermic reaction is caused by melting, decomposition, etc. of the active metal brazing material. For example, when titanium hydride (TiH ２ ) is used as the active metal, a peak in the negative direction is detected around 500 °C. This peak is the peak when TiH ２ decomposes into Ti and H.

[0064] Also, to lower the melting point of the brazing material, it is preferable to add one or two kinds selected from Sn or In to the brazing material. Among the components contained in the brazing material, it is also effective to make the particle size of Sn or In the largest. For example, in a brazing material composed of Cu, Sn, and Ti, the particle size of Sn is made the largest. Also, in a brazing material composed of Ag, Cu, Sn, TiH ２ , and C, the particle size of Sn is made the largest.

[0065] The average particle size of the materials constituting the brazing material is preferably within the range of 0.5 μm or more and 15 μm or less. Controlling the particle size of Sn powder or In powder within this range is effective. Among the materials constituting the brazing material 3, the melting points of Sn powder or In powder are low. Due to the presence of other materials around the material with a low melting point, the melting reaction can occur smoothly even when the heating rate is increased. A brazing material composition that does not contain Ag (mass ratio Ag / Cu = 0) is also effective. "Does not contain Ag" means that the content ratio of Ag is 0.01 mass% or less (including zero). Also, the possibility of short-circuiting when a voltage is applied to the substrate in a high-temperature and high-humidity environment is reduced by the absence of Ag. In other words, Ag ion migration can be suppressed.

[0066] After mixing the individual material powders constituting the active metal brazing material, an active metal brazing paste is prepared. By adding a solvent, binder, etc., to the mixed powder, a brazing paste is obtained. By using a paste, the application area and thickness of the brazing material can be adjusted. The thickness of the active metal brazing layer is preferably within the range of 10 μm to 60 μm. The paste is applied so that the thickness of the brazing layer after heat bonding falls within the above range. Alternatively, the active metal brazing material may be obtained by laminating rolled alloy foils or by supplying it using a film deposition apparatus.

[0067] A brazing material 3 is applied as a paste onto the ceramic substrate 4, and a copper plate is placed on top as the metal plate 2. Alternatively, brazing paste may be applied to the copper plate 4, and the ceramic substrate 4 may be placed on top. Alternatively, brazing paste may be applied to both sides of the ceramic substrate 4, and copper plates may be placed on both sides as the metal plate 2. After the laminate is fabricated, the manufacturing method using the continuous furnace 10 described above is applied.

[0068] Figure 5 is a cross-sectional view showing an example of a ceramic circuit board manufactured by a method for manufacturing a ceramic circuit board according to an embodiment of the present invention. The ceramic circuit board is manufactured by processing a bonded body. In Figure 5, reference numeral 14 denotes a circuit section, reference numeral 15 denotes a heat sink, and reference numeral 16 denotes a ceramic circuit board. The circuit section 14 is a metal plate 2 to which a circuit structure has been added. The heat sink 15 is made by processing the back side of the metal plate 2 which does not have a circuit structure. In the example shown in Figure 5, two circuit sections 14 are provided, but the structure of the ceramic circuit board 16 is not limited to this example. The number and shape of the circuit sections 14 are arbitrary. In addition, the metal plate 2 (shown in Figure 1) that is bonded to the front and back sides of the ceramic substrate 4 may be processed into a circuit section 14. Also, a sloping structure may be provided on the side surfaces of the circuit section 14 and the heat sink 15. A brazing layer overhang portion may be provided where the brazing layer 3 protrudes from the end of the circuit section 14 or the heat sink 15.

[0069] The temperature profile of the continuous furnace 10 is described below. The joining process of the manufacturing method using the continuous furnace 10 consists of three sub-processes: a heating process, a heating and joining process, and a cooling process. Each of these processes may be divided into multiple processing zones within the continuous furnace 10. For example, in the heating process, one process may be divided into multiple processing zones, such as a room temperature zone, a zone from room temperature to 150°C, a zone from 150°C to 400°C, a zone from 400°C to 600°C, and a zone from 600°C to hold at the joining temperature.

[0070] Furthermore, partitions or the like may be provided at the boundaries between zones, excluding entrance / exit curtain gases and transport paths. It is effective to set the heating temperature of each zone according to the average heating rate of the laminate 1 in the heating process and the bonding temperature of the laminate 1 in the heating bonding process. For example, the heating temperature can be controlled by adjusting the temperature of the heaters provided in each zone. In addition, temperature control for cooling (for example, temperature control by a cooling mechanism) can be performed in the cooling process.

[0071] In the method for manufacturing a bonded body according to the embodiment, the heating step in the bonding process is a step of heating the laminated body 1 on which the weights 6 are placed to the bonding temperature. The heating step is preferably in the range of 200°C or higher. The average heating rate of the laminated body 1 on which the weights 6 are placed during the heating step is 15°C / min or higher. The average heating rate is the average value of the heating rate of the laminated body 1 on which the weights 6 are placed from 200°C to the bonding temperature. By making the average heating rate fast, at 15°C / min or higher, it is possible to shorten the heating time. The heating rate may be constant or may change during the process. By making the average heating rate of the laminated body 1 on which the weights 6 are placed at 15°C / min or higher from 200°C to the bonding temperature, the time of the heating step can be shortened. In addition, by performing the process in an inert atmosphere, the vacuuming step becomes unnecessary. This also shortens the time.

[0072] If the average heating rate of the laminate 1 is less than 15°C / min, the time-saving effect will be insufficient. Furthermore, if the heating rate while transporting the laminate 1 with the weights 6 is slow, the transport distance will increase. A longer transport distance leads to a larger device. Therefore, an average heating rate of 15°C / min or higher is effective.

[0073] The upper limit of the average heating rate of the laminate 1 is not particularly limited, but it is preferably 100°C / min or less. If the average heating rate exceeds 100°C / min, variations may occur in the heat transferred to the laminate 1. Therefore, the average heating rate is preferably within the range of 15°C / min to 100°C / min, and more preferably within the range of 20°C / min to 70°C / min. The average heating rate is even more preferably within the range of 30°C / min to 70°C / min.

[0074] In the method for manufacturing a bonded body according to the embodiment, a heating step, a heating bonding step, and a cooling step are performed in the bonding step, and the average heating rate of the laminated body 1, the holding time of the bonding temperature, and the average cooling rate are calculated from the temperature profile of the laminated body 1 on which the weight 6 is placed. Measuring the upper surface temperature of the weight 6 placed on the laminated body 1 (bonded body) is effectively done using a thermocouple.

[0075] In the method for manufacturing a bonded body according to the embodiment, the heating bonding step, which constitutes the bonding process, is a step of heating bonding the laminated body 1 on which the weights 6 are arranged. The heating step and the heating bonding step, which constitute the bonding process, are carried out in an inert atmosphere, which is one or two selected from a nitrogen atmosphere or an argon atmosphere. The heating bonding step is within the range of 550°C to 950°C. If the bonding temperature is below 550°C, the bonding performance decreases. If the bonding temperature exceeds 950°C, warping occurs in the bonded body. For this reason, the bonding temperature is preferably within the range of 550°C to 950°C. Furthermore, it is more preferably 700°C to 950°C.

[0076] The time for holding the laminate 1 with the weights 6 at the bonding temperature is preferably 3 minutes or more. The continuous furnace 10 heats and bonds the laminate 1 with the weights 6 while transporting it. In other words, it is preferable that the laminate 1 with the weights 6, held at the bonding temperature, is transported through the furnace for 3 minutes or more. There is no particular upper limit to the time for holding the bonding temperature, but 60 minutes or less is preferable. If the time for holding the bonding temperature is long, the transport distance will increase, which may lead to the continuous furnace becoming larger. Also, warping of the bonded body may occur. For this reason, the time for holding the bonding temperature is preferably 3 minutes or more and 60 minutes or less, and more preferably 5 minutes or more and 30 minutes or less.

[0077] In the method for manufacturing a bonded body according to the embodiment, the cooling step constituting the bonding step is a step of cooling the laminated body 1 in which the weights 6 are placed to 100°C or less from the bonding temperature. Preferably, the average cooling rate of the laminated body 1 in which the weights 6 are placed during the cooling step is 15°C / min or more. With the method for manufacturing a bonded body using the weights 6 according to the embodiment, the time can be shortened compared to conventional methods by setting the average cooling rate of the cooling step to 15°C / min or more. Preferably, the cooling step is also carried out in an inert atmosphere. Preferably, the inert atmosphere is a nitrogen atmosphere.

[0078] If the average cooling rate of the laminate 1 on which the weight 6 is placed is less than 15°C / min, the time-saving effect will be insufficient. Also, if the cooling rate of the laminate 1 on which the weight 6 is placed is slow, the transport distance will increase. A longer transport distance leads to the need for larger equipment. Therefore, it is effective for the average cooling rate of the laminate 1 to be 15°C / min or higher. There is no particular upper limit to the average cooling rate, but it is preferably 100°C / min or less. If the average cooling rate exceeds 100°C / min, thermal stress will occur due to the cooling of the weight 6 and the laminate 1 being too fast, and the reliability of the ceramic circuit board 16 using this joint will decrease. In addition, variations in joint quality, or defects such as joint strength and warping of the joint may occur. For this reason, the average cooling rate is preferably within the range of 15°C / min to 100°C / min, and more preferably within the range of 20°C / min to 70°C / min. Furthermore, it is even more preferable for the average cooling rate to be within the range of 30°C / min to 70°C / min.

[0079] In the method for manufacturing a bonded body according to the embodiment, the difference D between the average heating rate and the average cooling rate of the laminate 1 is preferably 20°C / min or less. The difference D between the average heating rate and the average cooling rate is expressed by the following formula (3): D = |Average heating rate - Average cooling rate| ≤ 20°C / min …(3) When the brazing material layer is heated, a dissolution reaction and a solidification reaction occur. These reactions occur in the heating process and the cooling process. By reducing the difference D between the average heating rate and the average cooling rate, the stress caused by the reaction can be homogenized. This makes it possible to suppress defects such as warping. The heating rate from room temperature to 100°C is arbitrary. Similarly, the cooling rate from 100°C to room temperature is also arbitrary.

[0080] Furthermore, the continuous furnace 10 is not a sealed space. For example, the pressure inside the continuous furnace 10 is atmospheric pressure. The heating step, heating and bonding step, and cooling step that constitute the bonding process are preferably performed in an inert atmosphere. The inert atmosphere is one or two selected from a nitrogen atmosphere or an argon atmosphere. Nitrogen is cheaper than argon. For this reason, the inert atmosphere is preferably a nitrogen atmosphere. The nitrogen content in the nitrogen atmosphere is preferably in the range of 90% by volume or more and 100% by volume or less. If the nitrogen content in the nitrogen atmosphere is less than 90% by volume, it may adversely affect the bonding performance. For example, if the oxygen gas content increases, the brazing material layer may oxidize, which may adversely affect the bonding performance. For this reason, the nitrogen content in the nitrogen atmosphere is preferably in the range of 90% by volume or more and 100% by volume or less, and more preferably in the range of 98% by volume or more and 100% by volume or less. The purity of the nitrogen gas supplied to the continuous furnace is considered to be the nitrogen content in the nitrogen atmosphere.

[0081] Furthermore, if the heating process, heating bonding process, and cooling process that constitute the bonding process are divided into multiple processing zones, the purity (volume %) of the nitrogen gas provided in each processing zone is considered to be the proportion of nitrogen in the nitrogen atmosphere. In addition, the dew point of the nitrogen gas is preferably within the range of -50°C to 0°C. The dew point can be determined by measuring the dew point of the nitrogen gas supplied into the continuous furnace 10. The dew point is the temperature at which water vapor in a gas condenses. By setting the dew point of the nitrogen gas within the aforementioned range, the generation of water vapor in the continuous furnace 10 can be suppressed. Since the presence of water vapor in the atmosphere inside the continuous furnace 10 affects bonding performance, controlling the dew point of the nitrogen gas is effective.

[0082] In the method for manufacturing a joined body according to the embodiment, it is preferable to introduce the inert atmosphere from an inlet pipe 9 located in the forward direction of the conveying direction of the laminate 1 (in the direction of the arrow shown in Figure 2). When the laminate 1 is heated, gas may be released from the brazing layer. Examples of gases include oxygen gas, hydrocarbon gas, carbon dioxide gas, and carbon monoxide gas. If the gas released from the brazing layer accumulates, the surface of the metal plate 2 may discolor. Therefore, it is preferable to provide an exhaust pipe 8 at the rear in the conveying direction of the laminate 1 to prevent the gas released from the brazing layer from accumulating. This makes it possible to suppress the gas released from the brazing layer from coming into contact with the laminate 1. Also, when the processing zones of the joining process are separated, an inlet pipe 9 and an exhaust pipe 8 may be provided for each processing zone, or the inlet pipe 9 and exhaust pipe 8 may straddle the processing zones.

[0083] Furthermore, it is preferable that the conveyance of the laminate 1 within the continuous furnace 10 be by a belt conveyor system. A belt conveyor system makes it easier to control the conveyance speed of the laminate 1. When conveying the laminate 1, the laminate 1 may be placed directly on the belt conveyor 7. Alternatively, the laminate 1 may be placed on a conveyor tray, and the conveyor tray may be placed on the belt conveyor 7. A mesh belt may be used for the conveyor belt. When using a conveyor tray, the laminate 1 may be conveyed within the continuous furnace 10 using a walking beam system.

[0084] By placing one weight 6 for each stacked stack 1 in the planar direction, a greater effect can be obtained than by placing one weight 6 for each of multiple stacked stacks 1 stacked in the height direction. Therefore, it is preferable to place one weight 6 for each stacked stack 1 in the planar direction. In addition, in the method for manufacturing the joined body according to the embodiment, the weight 6 may be placed on the uppermost stacked stack 1 among the multiple stacked stacks 1. Although the manufacturing method using a continuous furnace 10 has been described, in the method for manufacturing the joined body according to the embodiment, the weight 6 may also be used during heat joining in a batch furnace.

[0085] The following describes the examples. (Examples 1-5, Comparative Examples 1-5) Silicon nitride was used for the ceramic substrate 4 in the examples and comparative examples. A large silicon nitride substrate with a thermal conductivity of 90 W / m·K, a three-point bending strength of 600 MPa, and dimensions of 180 mm (length) x 140 mm (width) was used. A copper plate (for example, an oxygen-free copper rolled plate) measuring 178 mm (length) x 138 mm (width) was prepared for the metal plate 2. The copper plate on the front side where the circuit is formed was designated as the first copper plate, and the copper plate on the back side, which is the heat sink side where the circuit is not formed, was designated as the second copper plate. The thicknesses of the ceramic substrate 4, the first copper plate, and the second copper plate are shown in Table 1. The first and second copper plates were solid copper plates.

[0086]

[0087] Next, three types of activated metal brazing materials were prepared as shown in Table 2. The activated metal brazing materials are activated metal brazing materials containing Ti. The average particle size of the materials constituting the brazing material was between 0.5 μm and 15 μm.

[0088]

[0089] Brazing material 1 was used in Examples 3 and 4 and Comparative Example 5, brazing material 2 was used in Examples 1 and 2 and Comparative Examples 1 and 2, and brazing material 3 was used in Example 5 and Comparative Examples 3 and 4. The activated metal brazing material was supplied by coating it onto a silicon nitride substrate using a screen printing method. After coating, the silicon nitride substrate was dried in a drying oven to remove the solvent component of the brazing material paste. A first copper plate and a second copper plate were laminated on the front and back surfaces of the silicon nitride substrate, respectively.

[0090] A setter was placed between the first copper plate and weight 6. The setter used was 180 mm long x 140 mm wide x 0.5 mm thick. The density of weight 6 was measured by the Archimedes method. The measurement method was as described above. Next, the thermal conductivity of weight 6 was measured by the laser flash method. The measurement method was as described above.

[0091] Next, the joining process of the laminate 1 was carried out in a mesh belt type continuous furnace 10. A mesh belt type continuous furnace 10 is one in which the belt used in the belt conveyor 7 is made of mesh. The heating process, the heating joining process, and the cooling process that constitute the joining process were all carried out in a nitrogen atmosphere. Nitrogen gas was flowed into the continuous furnace 10 at a rate of 100 L / min and controlled to a composition of 100% nitrogen gas. Nitrogen gas was supplied from the inlet pipe 9 and discharged from the exhaust pipe 8. The inlet pipe 9 was located in front of the laminate 1 in the direction of travel, and the exhaust pipe 8 was located behind it in the direction of travel.

[0092] The ratio TH / TC, which is the time TH that the laminate 1 spends in the heating zone to the time TC that it spends in the cooling zone, was set to 1.0 so as to satisfy formula (2) above. In Examples 1-3 and Comparative Example 1-3, the transport speed of the laminate 1 was kept constant at 150 mm / min, and in Examples 4 and 5 and Comparative Examples 4 and 5, the transport speed of the laminate 1 was kept constant at 100 mm / min. The average heating rate of the laminate 1 was set to 50°C / min, and the temperature was set so that the heating and bonding temperature was maintained at 800°C or higher for 20 minutes. The average cooling rate of the laminate 1 was set to 40°C / min.

[0093] Furthermore, the weights 6 were placed on the surface of the laminate 1 before the laminate 1 was transported. One weight 6 was used as one set for each laminate 1, and 10 sets were fed in succession. The feeding interval was set so that there was a 30 mm gap between the rear end of the previously fed laminate 1 and the front end of the next laminate 1 to be fed in the transport direction.

[0094] Table 3 shows the materials of the weight 6 examined, along with their respective densities at room temperature, heat capacity per kg, thermal conductivity, and pressing force (surface pressure) per unit area. The measurement methods for each were as described above.

[0095]

[0096] Table 4 shows the shape, thickness, and AW / AS of the weight 6, and indicates the presence or absence of the weight 6 in the outer periphery support area and the center of gravity support area. Solid plates were used in Examples 1, 3, and 4 and Comparative Examples 1 and 2. Figure 4 shows a schematic diagram of the solid plate. The dimensions of the solid plate were the same as the laminate, 180 mm in length and 140 mm in width. For Example 5, a solid plate with dimensions of 198 mm in length and 154 mm in width was used.

[0097] In Example 2, a framed cross-beam shaped weight was used. The external dimensions of the framed cross-beam were 180 mm in length, 140 mm in width, and 6.3 mm in thickness. The intersection of the cross beam was made to coincide with the center of the planes of the laminate 1 and the weight 6, and the cross-section of the beam was made to have a width of 50 mm and a height equal to the thickness.

[0098] Comparative Example 3 used a small solid plate as a weight. The dimensions of the small solid plate were 147 mm in length, 118 mm in width, and 7 mm in thickness. When being placed in the bonding process, the laminated body 1 and the weight 6 were laminated so that their planar centers aligned. Comparative Example 4 used a frame-shaped weight 6. The outer dimensions were the same as the laminated body 1, 180 mm in length and 140 mm in width, and the inner dimensions were 134 mm in length and 94 mm in width. In addition, no weight 6 was placed in the laminated body related to Comparative Example 5.

[0099]

[0100] Table 5 shows the removal temperature of the weight 6 surface for the examples and comparative examples, the amount of warping of the long side of the joint's plane and the total warping of the upper surface of the joint, the average amount of warping of each joint after the joint was divided, and the percentage of sound joint area of ​​the joint. The removal temperature of the weight 6 was measured using a contact thermometer (FUSO FS-300S) at the position where the joint and weight 6 had completely emerged from the continuous furnace 10. The measurement method was as described above.

[0101] The amount of warping of the joint was obtained by separating the joint from the weight 6 and setter, allowing the joint to cool sufficiently, and then measuring the long side of the joint's plane and the maximum point across the entire plane of the joint using a laser displacement meter (Keyence VR-5000 one-shot 3D shape measuring machine). If voids are present in the brazing material layer 3, the portion containing the voids will not be joined. Therefore, the sound joint area was calculated as the ratio of the area where no voids were detected to the design joint area by analyzing the joint image with an ultrasonic flaw detection device (Hitachi FineSAT_V).

[0102]

[0103] Examples 1-5 show that the extraction temperature is below 100°C, and consequently, both the warp of the long side of the planar surface of the joint and the warp of the entire planar surface of the joint are small. Furthermore, even when the joint is divided, the difference in warp between the divided joints is small, and the warp is small even when viewed locally.

[0104] On the other hand, in Comparative Examples 1 and 2, because materials with high heat capacity or low thermal conductivity were used for the weight 6, the thermal response of the laminate 1 (joint) and weight 6 in the furnace was poor, and the temperature reached in the heating zone was somewhat low, resulting in many joint defects and a high removal temperature of over 100°C. Consequently, Comparative Examples 1 and 2 tended to have large amounts of warping along the long side of the joint and across the entire surface of the joint. Furthermore, when the joint was divided, the difference in warping between the divided joints tended to be large.

[0105] In Comparative Examples 3 and 4, although the removal temperature dropped to a similar level to Examples 1 and 2 because the same stainless steel was used as the weight as in Examples 1 and 2, the contact area of ​​the weight 6 was insufficient and inadequate for restraining the laminate 1. As a result, the amount of warping was large, especially the amount of warping across the entire joint and the amount of warping when it was divided. In Comparative Example 5, since no weight 6 was placed, there was no surface pressure at all. As a result, there was nothing to restrain the laminate 1, and the amount of warping was large. Furthermore, even when the joint was divided, the difference in the amount of warping between the divided joints was large.

[0106] According to the method for manufacturing a bonded body in the embodiment, by placing the weight 6 on the laminate 1 during the bonding process using the continuous furnace 10, a high-quality bonded body can be manufactured with reduced warping across the entire planar surface of the bonded body while maintaining high productivity. Furthermore, according to the method for manufacturing a ceramic circuit board 16 in the embodiment, by using a high-quality bonded body, the ceramic circuit board 16 can be manufactured with a good yield.

[0107] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents.

Claims

1. A method for manufacturing a bonded body, comprising: a lamination step of stacking a metal plate and a ceramic substrate via an activated metal brazing material to produce a laminate; a placement step of placing weights having a heat capacity of 600 J / K or less per 1 kg and a thermal conductivity of 15 W / m·K or more on the plane of the laminated body; and a joining step of heating and joining the laminated body on which the weights are placed using a continuous furnace to produce a bonded body.

2. The method for manufacturing a bonded body according to claim 1, wherein the pressing force applied to the laminated body by the weight is within the range of 10 Pa or more and 500 Pa or less per unit area.

3. A method for manufacturing a bonded body according to any one of claims 1 to 2, wherein, in a plan view of the laminated body from the weight side, the ratio AW / AS of the area of ​​the weight to the area AS of the laminated body is in the range of 0.6 or more and 1.2 or less.

4. The method for manufacturing a joined body according to any one of claims 1 to 3, wherein, in a plan view of the laminated body from the weight side, the weight is arranged to cover an outer peripheral support area which includes the outer periphery of the laminated body and a center of gravity support area which includes the center of gravity of the laminated body.

5. The method for manufacturing a bonded body according to claim 4, wherein the laminate is rectangular in plan view of the laminate from the weight side, the outer peripheral support area is the area between the outer peripheral and a rectangular frame formed by connecting four points inward from the outer peripheral by a length of 10% of the length of each diagonal with straight lines, and the center of gravity support area is the area within a rectangular frame formed by connecting four points outward from the center of the laminate by a length of 20% of the length of each diagonal with straight lines.

6. A method for manufacturing a joint according to any one of claims 1 to 5, wherein the weight is composed of a single member.

7. The method for manufacturing a joined body according to any one of claims 1 to 6, wherein the continuous furnace comprises a heating zone on the side where the laminate is introduced, which includes a heating step and a heating bonding step, and a cooling zone on the side where the joined body is removed after bonding, and the ratio TH / TC of the time TH during which the laminate stays in the heating zone to the time TC during which it stays in the cooling zone is 0.7 or more and 1.5 or less.

8. The method for manufacturing a bonded body according to any one of claims 1 to 7, wherein the conveying speed of the laminate is 50 mm / min or more and 300 mm / min or less.

9. The method for manufacturing a bonded body according to any one of claims 1 to 8, wherein the temperature of the upper surface of the weight when the laminated body is introduced into and removed from the continuous furnace is 100°C or less.

10. The density of the weight is 7.0 g / cm³. ３ The method for manufacturing a joined body according to any one of claims 1 to 9.

11. A method for manufacturing a bonded body according to any one of claims 1 to 10, wherein the plane of the ceramic substrate is rectangular and the shorter side of the plane of the ceramic substrate is 90 mm or more.

12. A method for manufacturing a bonded body according to any one of claims 1 to 11, wherein the metal plate is a copper plate, the ceramic substrate is a silicon nitride substrate, and the active metal brazing material contains Ti.

13. A method for manufacturing a bond according to any one of claims 1 to 12, wherein the active metal brazing material does not contain Ag.

14. A method for manufacturing a ceramic circuit board, comprising: an arrangement step and a bonding step according to any one of claims 1 to 13; and an etching step of etching the bonded body manufactured by the bonding step.

15. The method for manufacturing a ceramic circuit board according to any one of claims 1 to 13, wherein the metal plate of the laminate produced in the lamination step is made of copper having a pre-defined pattern shape.

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