JP5817164B2 - Joining method, joining jig - Google Patents

Description

  The present invention relates to a joining method for simultaneously manufacturing a large number of structures having a structure in which flat plate materials having different thermal expansion coefficients are joined together, or a joining jig used in the joining method. Moreover, it is related with the circuit board manufactured using this joining method.

  In recent years, power semiconductor modules (for example, IGBT modules) capable of high voltage and large current operation have been used as inverters for electric vehicles. In such a semiconductor module, since the semiconductor chip becomes high temperature due to its own heat generation, a function of efficiently radiating the heat is required. For this reason, in this semiconductor module, as a circuit board on which a semiconductor chip is mounted, a metal circuit board is bonded to one surface of an insulating ceramic substrate having high mechanical strength and high thermal conductivity, and the other surface is bonded to the other surface. A structure in which a heat sink is joined is used. A metal circuit board and a heat sink are comprised with the metal which has copper which has high electroconductivity and heat conductivity as a main component.

  As a material constituting the ceramic substrate, silicon nitride ceramics and the like are widely used. Metal circuit boards and heat sinks are made of copper or copper alloys. For example, a brazing material is used for bonding between them. A semiconductor chip or the like is mounted on the metal circuit board, and the metal circuit board serves as a wiring in a circuit formed by the semiconductor chip in the semiconductor module. Therefore, the metal circuit board is appropriately patterned so as to constitute this wiring. On the other hand, since the heat dissipation plate is used for heat dissipation, it is preferable that the area of the heat dissipation plate is wide, and it is often a flat state that is not patterned.

  When manufacturing a circuit board having such a configuration, a metal circuit board, a ceramic board, and a heat sink, which are in a flat state before patterning, are laminated and bonded. In this case, first, after a brazing material is formed on both surfaces of the ceramic substrate by printing, a laminated structure of a metal circuit board / ceramic substrate / heat sink is formed. Thereafter, the brazing material is melted between them at a high temperature and then cooled, thereby joining. At this time, it is necessary that the bonding between them be made uniform and strong. In order to reduce the manufacturing cost, it is desirable to apply this bonding to a large number of laminated structures at the same time.

  A joining jig for performing such joining is described in Patent Documents 1 to 3, for example. In these joining jigs, a structure (laminated structure) in which a brazing material is sandwiched between two plate-like members arranged in parallel in the vertical direction is sandwiched between spacers. A plurality of layers are stacked to form a pressed body. A spring is connected to the upper side of the upper plate-like member so that a pressure is uniformly applied to the pressed body between the two plate-like members.

  For example, when a metal circuit board made of copper and a ceramic substrate made of silicon nitride ceramics are used, the brazing material for joining them is mainly composed of silver and an active material such as titanium. A brazing material to which a metal is added is preferably used. In this case, since a strong reaction layer is formed between the brazing material and copper or silicon nitride ceramics, a strong bond can be obtained. The temperature required for joining at this time is a high temperature of about 800 ° C., for example. In particular, since active metals such as titanium are easily oxidized, this joining is preferably performed in a vacuum (reduced pressure). For this reason, after said to-be-pressurized body is set to said joining jig, this joining jig is heated to said temperature in a vacuum. After cooling, the joining jig is taken out into the atmosphere, and the member to be pressed is taken out. As a result, a plurality of the laminated structures (metal circuit board / ceramic substrate / heat sink) are obtained with the spacers sandwiched between the metal circuit board, the ceramic substrate and the heat sink.

  In the above process, gas may be generated from the brazing material at a high temperature, and if this gas is not sufficiently removed, it becomes a void in the brazing material after bonding, which causes a decrease in bonding strength and the like. Therefore, it is necessary to form a gas escape path around the above-mentioned pressurized object. For this reason, the periphery of the side surface of the member to be pressed in the above-mentioned joining jig is not a flat wall, but is composed of a plurality of cylindrical columnar members extending in parallel in the vertical direction. That is, the above-mentioned pressurized body is surrounded and fixed by a large number of columnar members, and gas is released from between the columnar members, so that generation of voids is suppressed.

  In addition, since this joining jig is placed in a high-temperature vacuum, the components (two plate-like members, springs, columnar members, etc.) constituting it are all deformed or chemically reacted even at high temperatures, such as ceramics or carbon. It is made of a material that is difficult to produce. The joining jig is formed by combining and fixing these components.

  Here, there is a difference in thermal expansion coefficient between copper constituting the metal circuit board and silicon nitride ceramics constituting the ceramic substrate. For this reason, when it is cooled after being heated to a high temperature in a pressurized state, warpage is likely to occur in the member to be pressed (laminated structure) due to the difference in thermal expansion coefficient. In practice, the metal circuit board is often thicker than the heat sink, and in this case, warpage occurs toward the metal circuit board side. Due to this warpage, a portion where the distance between the metal circuit board or the heat radiating plate and the ceramic substrate becomes wide is generated. At this location, voids are generated in the brazing material, and the bonding strength is reduced. In the above-mentioned joining jig, the non-uniformity of the joining strength is reduced by uniformly pressing the two objects to be pressed over a wide area by the upper and lower plate-like members.

  In the laminated structure after bonding, the metal circuit board is thereafter patterned into a predetermined pattern. In order to reduce the cost, a large number of circuit boards are often obtained by separating and cutting a single laminated structure into a large number. In this case, the patterning of the heat sink corresponding to this and this cutting work are also performed.

  Using such a joining jig, a circuit board can be manufactured at low cost. The same applies to a structure other than the circuit board, in which materials having different thermal expansion coefficients need to be bonded in a high-temperature reduced pressure using a brazing material.

JP 2007-216260 A JP 2010-238899 A JP 2010-238900 A

  However, in the laminated structure after bonding obtained by the above manufacturing method, actually, a portion having a low bonding strength is generated at a portion corresponding to the peripheral portion of the pressed body. The reason is that the laminated structure hits the columnar member at the peripheral edge.

  At the time of high temperature bonding, the metal circuit board and the heat radiating board mainly composed of copper are thermally expanded and softened. For this reason, when these end portions hit the columnar member in this state and are cooled thereafter, they are largely deformed near the peripheral portion. On the other hand, silicon nitride ceramics has a smaller coefficient of thermal expansion than these, and hardly deforms. Therefore, the metal circuit board and the heat radiating plate are locally greatly deformed at the peripheral portion, and a portion where the distance from the ceramic substrate is increased is locally generated. The bonding strength at this location decreases as described above. For this reason, the circuit board including this portion becomes a defective product, or the reliability decreases. That is, it has been difficult to manufacture a highly reliable circuit board at a high yield or low cost.

  In this way, when manufacturing a circuit board having a configuration in which a ceramic substrate and a metal plate are bonded via a brazing material at a high temperature, a circuit board having a uniformly high bonding strength is reduced. It was difficult to get at cost.

  The present invention has been made in view of such problems, and an object thereof is to provide an invention that solves the above problems.

In order to solve the above problems, the present invention has the following configurations.
The joining method of the present invention is a joining method in which a first member and a second member, each having a rectangular flat plate shape and having different thermal expansion coefficients, are joined at a high temperature, and the first member and the first member are joined together. A substantially rectangular body to be pressed in which a laminated structure in which two members are laminated along a laminating direction that is a normal direction of a surface in a flat plate shape is laminated in plural along the laminating direction via a flat spacer. A plurality of columnar members are arranged in a row substantially parallel to the three side surfaces of the member to be pressed parallel to the stacking direction, and are surrounded by the columnar members. in joining jig internal to at intervals comprises a configuration wherein the pressure body can accommodate, the columnar member and the object to be pressure body is vertical respectively constituting the two columns are not parallel to each other among the three rows In contact with a directional spacer and constitute another row A pressurized body installation step of installing the pressurized body inside the plurality of columnar members in a state where the columnar member and the pressurized body are not in contact with each other; Applying a pressure along the laminating direction and extracting the two vertical spacers from the joining jig, and heating and cooling the joining jig on which the pressurized body is installed. And a joining step for joining the first member and the second member.
In the bonding method of the present invention, in the pressed object preparation step, the first member and the second member are stacked with a brazing material interposed therebetween, and in the bonding step, the first member and the second member are stacked. The second member is joined by a brazing material.
In the bonding method of the present invention, the heating in the bonding step is performed in a reduced pressure atmosphere.
In the bonding method of the present invention, in the pressed object preparation step, two types of spacers having different thicknesses are provided as the spacers, and the two types of spacers are alternately arranged in the stacking direction. Features.
In the bonding method of the present invention, the first member is a ceramic substrate, and the second member is a metal plate mainly composed of copper.
In the bonding method of the present invention, the ceramic substrate is larger in plan view than the metal plate, and in the bonding preparation step, on the side surface parallel to the stacking direction of the pressed bodies on the side where the vertical spacer is not disposed. The ceramic substrate protrudes from the metal plate .
Each of the joining jigs of the present invention has a rectangular flat plate shape and is used to join the first member and the second member having different thermal expansion coefficients at a high temperature, and the first member and the first member A substantially rectangular body to be pressed is formed by laminating a plurality of laminated structures along the laminating direction in which the two members are laminated along the laminating direction, which is the normal direction of the surface in the flat plate shape , the plurality of columnar members in parallel the stacking direction and the three sides parallel substantially in the pressing body is arranged over three rows, the configuration in which the pressure body can be housed inside surrounded by the plurality of columnar members A joining jig having a configuration in which a pressure is applied along the stacking direction to the pressurized bodies in a state in which the pressurized bodies are accommodated in the interior. Each of two rows that are not parallel to each other and opposite each of the two rows The columnar members which are provided between the side surfaces of the pressurized bodies and which constitute the two rows in a state where the columnar members which constitute another row and the pressurized bodies are not in contact with each other. Two longitudinal directions configured to be able to be pulled out from between the columnar members constituting the two rows and the pressurized bodies in a state where both of the pressurized bodies are applied and the pressure is applied A spacer is provided.

  Since the present invention is configured as described above, it is uniformly high when bonding is performed at a high temperature when manufacturing a circuit board having a configuration in which a ceramic substrate and a metal plate are bonded via a brazing material. A circuit board having bonding strength can be obtained at low cost.

(A) The side view of the structure by which the to-be-pressurized body was installed in the joining jig | tool which concerns on embodiment of this invention, (b) The figure which shows the structure in the cross-sectional direction of a to-be-pressurized body. It is sectional drawing which shows the structure of a to-be-pressurized object periphery in detail when a to-be-pressurized body is installed in the joining jig | tool which concerns on embodiment of this invention. It is a figure which shows the condition of joining in a comparative example and an Example.

  The present invention will be described below with reference to specific embodiments. However, the present invention is not limited to these embodiments. In the joining method of the present invention, a plurality of types of materials having different thermal expansion coefficients are joined at a high temperature using a brazing material. In the following embodiment, an example will be described in which metal plates (metal circuit plates and heat radiating plates) are bonded to both surfaces of a ceramic substrate. When this bonding is performed, a brazing material is formed on both sides of the ceramic substrate by printing, and a laminated structure in which a metal circuit board / ceramic substrate / heat sink is laminated is formed. Thereafter, a large number of the laminated structures are laminated via spacers to form a pressed body. A pressure is applied to the object to be pressed in the above-described stacking direction at a high temperature. Thereby, the brazing material is melted, and a reaction layer is formed between the metal circuit board and the ceramic substrate and between the ceramic substrate and the heat sink. A structure in which the metal circuit board and the heat sink are firmly bonded to the ceramic substrate in a state where the brazing material is solidified after cooling is obtained.

  FIG. 1 shows a configuration (a) viewed from a side surface when a bonding jig used in this bonding method is used, and a configuration in the vicinity of a cross section (A-A direction) perpendicular to the stacking direction of the objects to be pressed. It is a top view (b) shown. FIG. 2 is a cross-sectional view specifically showing a contact portion between the side surface of the pressed body 100 and the joining jig. The state shown in FIGS. 1 and 2 is a state at normal temperature before bonding is performed at a high temperature after heating.

  As shown in FIG. 2, the laminated structure 10 is configured by laminating metal plates (second member: metal circuit plate 12, heat radiating plate 13) above and below a ceramic substrate (first member) 11. The Although not shown in the drawing, a brazing material exists over the entire interface between the metal circuit board 12 and the ceramic substrate 11 and between the heat sink 13 and the ceramic substrate 11. This brazing material is formed in advance on the both surfaces of the ceramic substrate 11 in the same shape as the metal circuit board 12 and the heat radiating plate 13 by printing. The ceramic substrate 11, the metal circuit board 12, and the heat dissipation plate 13 are all rectangular flat plates. As shown in FIGS. 1B and 2, the ceramic substrate 11 usually has the metal circuit board 12, It is made larger than the radiator plate 13 in plan view. This is because the end of the ceramic substrate 11 is usually marked so that the operator can identify the marking even after joining.

  Here, as the ceramic substrate 11, for example, silicon nitride ceramics is used. Silicon nitride ceramics have high insulation, thermal conductivity, and mechanical strength. Its thermal expansion coefficient is about 3 ppm / ° C. Its thickness is about 0.32 mm.

  On the other hand, the metal plates (the metal circuit board 12 and the heat sink 13) are made of, for example, copper. The thermal expansion coefficient of copper is about 20 ppm / ° C., which is larger than that of the ceramic substrate 11. Unlike silicon nitride ceramics, copper has the property of softening at high temperatures. The thickness of the metal circuit board 12 and the heat sink 13 is, for example, about 0.5 mm, and is set as appropriate. However, the metal circuit board 12 is usually thicker in many cases.

  As the brazing material, a material mainly composed of silver and added with titanium or the like as an active metal is particularly preferably used. In this case, a reaction layer is easily formed on the surface of silicon nitride ceramics or the like at a high temperature, and particularly strong bonding is obtained after cooling. The bonding in this case is performed at about 800 ° C., for example.

  A large number of the laminated structures 10 are laminated with a spacer interposed therebetween to form a pressurized object 100 having a substantially rectangular shape (pressurized object preparation step). However, there are two types of spacers (thick first spacer 21 and thin second spacer 22) having different thicknesses. These spacers are made of high-density carbon having high mechanical strength. The thickness of the first spacer 21 is, for example, about 3 mm, and the thickness of the second spacer 22 is, for example, about 1 mm. Both spacers have a rectangular flat plate shape similar to the ceramic substrate 11 or the like. These spacers are in direct contact with the metal circuit board 12 or the heat sink 13. For this reason, these spacers are made larger than the metal circuit board 12 or the heat sink 13 in plan view. These spacers are provided to prevent the adjacent laminated structure 10 from being fixed after bonding. Immediately after the pressed body is formed, the brazing material is not yet melted, and therefore the ceramic substrate 11 and the metal circuit board 12, and the ceramic substrate 12 and the heat radiating plate 13 are not joined.

  As shown in FIG. 1A, in this joining jig, the pressed body 100 having this configuration is sandwiched between a bottom plate 50 and an upper plate 51. The upper end of the upper plate 51 is connected to the lower end of the spring 52, and the upper end of the spring 52 is fixed to the top plate 54 fixed via the bottom plate 50 and the columnar member 53. In order to apply pressure uniformly in the in-plane direction, it is preferable to provide a plurality of springs 52. In this case, it is preferable to connect to the outer side (peripheral side) of the upper plate 51.

  As shown in FIG. 1B, three columnar members 53 are provided in three rows and three rows in a form surrounding three sides of a cross section (rectangle) perpendicular to the stacking direction of the pressed body 100. The columnar member 53 is a cylindrical member whose central axis is the vertical direction (stacking direction of the pressurized object 100). The object to be pressurized 100 is accommodated inside the region surrounded by the plurality of columnar members 53. At this time, the pressurized object 100 is configured to be accommodated in the region surrounded by the plurality of columnar members 53 at intervals from the columnar members 53 constituting each row. That is, in FIG. 1B, the rectangle inscribed in the region formed by the columnar member 53 is a rectangle corresponding to the pressed body 100 having a substantially rectangular shape (in the case of FIG. 1B, the spacers 21 and 22). Larger than the rectangle corresponding to.

  Since this joining jig is heated to a high temperature in a state where the member to be pressed 100 is set, the material constituting it is composed of a material having high mechanical strength that does not cause deformation or chemical reaction at high temperature. The For this reason, the bottom plate 50, the upper plate 51, the columnar member 53, and the top plate 54 are made of, for example, inexpensive low density carbon. The spring 52 is made of ceramics, for example.

  Here, as shown in FIG. 1B, the plate-like longitudinal spacer 31 is in contact with these sides (side surfaces) of the pressed body 100 at the upper side and the left side of the pressed body 100. , 32 are provided. With this configuration, the three columnar members 53 and the pressurized object 100 are fixed by contacting with each other via the vertical spacer 31 on the upper side. Further, the vertical spacer is not used on the lower side and the right side of the pressed body 100, and the right side of the pressed body 100 is not in contact with the columnar member 53. Note that the columnar member 53 does not exist on the lower side. For this reason, it is easy to set the pressurized body 100 in this way in the direction indicated by the arrow from the lower side shown in FIG.

  With this configuration, in the configuration in the cross-sectional direction of the pressed body 100 shown in FIG. 1B, the ceramic substrate 11, the metal circuit plate 12, and the heat radiating plate 13 on the upper side (upper side surface) and the left side (left side surface). The spacers (the first spacer 21 and the second spacer 22) are arranged so that the respective sides are aligned (pressurized object installing step). Since the sizes of the ceramic substrate 11, the metal circuit board 12, the heat radiating plate 13, and the spacer are different as described above, the positions of these sides on the lower side and the right side of the pressed body 100 shown in FIG. Are not complete.

  In this state, if the load of the spring 52 is adjusted by adjusting the compression amount of the spring 52, for example, a uniform pressure can be applied in the vertical direction (stacking direction) of the pressed body 100. Thereby, this pressure can be applied to each laminated structure 10 laminated.

  After the pressure is applied to the pressurized object 100 as described above, the vertical spacers 31 and 32 are extracted (joining preparation step). That is, the vertical spacer 31 is extracted in the horizontal direction in FIG. 1B without interfering with the columnar member 53, and the vertical spacer 32 is similarly extracted in the vertical direction in FIG. 1B. As a result, any side surface of the pressed body 100 shown in FIG. 1B is not in direct contact with the columnar member 53. The distance between the side surface of the member to be pressed 100 and the columnar member 53 adjacent thereto is such that they contact the columnar member 53 even when the metal circuit board 12 and the heat radiating plate 13 are thermally expanded during heating. It is set to not.

  In this state, the entire structure of FIG. 1 (other than the vertical spacers 31 and 32) is heated to 800 ° C., which is the bonding temperature of the brazing material. At this time, in order to suppress oxidation of titanium contained in the brazing material, it is more preferable that the atmosphere is in a vacuum (in a reduced pressure atmosphere). In this case, in the above-described configuration, there is nothing that is in direct contact with the periphery of the laminated structure 100, and there is a space between the columnar members 53. Therefore, this gas is easily released. In other words, the release of the gas from the brazing material at a high temperature is particularly easily performed in the above configuration.

  Thereafter, after the reaction of the brazing material has sufficiently progressed, the above structure is taken out and cooled to join each laminated structure 10 (metal circuit board 12 / ceramics substrate 11 / heat sink 13) (joining) Process). Then, the to-be-pressurized body 100 is divided at the first spacer 21 and the second spacer 22 to obtain individual laminated structures 10. Thereafter, the metal circuit board 12 in each laminated structure 10 is selectively etched and patterned, and then cut and separated into a small circuit board.

  In the above process, the ceramic substrate 11, the metal circuit board 12, and the heat sink 13 are thermally expanded particularly at high temperatures. Under the present circumstances, as above-mentioned, it is especially the metal circuit board 12 and the heat sink 13 that thermal expansion is large. Furthermore, the copper which comprises these at the temperature which reaches | attains during joining (temperature of about 250 degreeC or more) softens. For this reason, at this high temperature, the thermally expanded metal circuit board 12 and the heat radiating plate 13 may come into contact with the structure around the pressed body 100. In this case, the metal circuit board 12 and the heat radiating plate 13 are deformed because they are softened, and the joining is performed through the brazing material in the deformed form. For this reason, in the peripheral part of the to-be-pressed body 100, the location where the space | interval between the ceramic substrate 11, the metal circuit board 12, and the heat sink 13 is locally large is formed. In these places, voids are easily formed in the brazing material.

  In the above-described configuration, the vertical spacers 31 and 32 are used as shown in FIG. 1 at the stage of mounting the member 100 to be pressed to the joining jig at room temperature, and these are extracted before heating. Thus, the occurrence of the above problem is suppressed by increasing the distance between the side surface of the pressed body 100 and the surrounding structure (the columnar member 53). That is, it is possible to suppress the formation of voids in the peripheral portion and to increase the bonding strength uniformly.

  Further, in the state of FIG. 1B, the upper side and the left side of the ceramic substrate 11, the metal circuit board 12, and the heat radiating plate 13 are in contact with the vertical spacers 31 and 32, respectively, so that they are aligned. On the other hand, in the lower side and the right side, the ceramic substrate 11 is configured to protrude from the metal circuit board 12 and the heat sink 13. As described above, this state is obtained at normal temperature. However, if the vertical spacers 31 and 32 are extracted after pressurization at normal temperature, it is clear that this state is maintained even after that. Therefore, as long as the metal circuit board 12 and the heat radiating plate 13 do not contact the columnar member 53 at a high temperature, this state is maintained thereafter. For this reason, even after being cooled after being exposed to a high temperature, the state in which the ceramic substrate 11 protrudes from the metal circuit board 12 and the heat sink 13 is maintained on the lower side and the right side. For this reason, if marking etc. are given to the surface of the ceramic substrate 11 in this protruding part, an operator can confirm this easily before and after joining.

  At this time, in the above-described joining jig, compared to the conventional joining jigs described in Patent Documents 1 to 3, only the vertical spacers 31 and 32 are added. As a result, the above-described effects are exhibited. That is, a circuit board having a uniform high bonding strength can be obtained at low cost using the above-described bonding jig. As a result, a highly reliable circuit board can be easily manufactured at a high yield and at a low cost.

  In the above-mentioned joining jig, the plurality of columnar members 53 are arranged in three rows along the left side, the upper side, and the right side of the pressed body 100 in FIG. In the pressed body installation step, the vertical spacers 31 and 32 are arranged between the columnar members 53 in the row along the left side and the left side of the pressed body 100, and the columnar members 53 in the row along the upper side. Each was provided so as to be in contact with the columnar member 53 and the pressed body 100 between the upper surface of the pressed body 100. However, the same applies to a configuration in which the vertical spacer is provided on the right side surface and the upper side surface. That is, the vertical spacers may be provided in two rows that are not parallel to each other among the three rows in which the columnar members 53 are provided. Thereby, the columnar members 53 constituting the two rows and the pressurized object 100 are in contact with each other through the vertical spacers, and the columnar members 53 constituting the other row and the pressurized object 100 are not in contact with each other. Can produce. At this time, it is easy to arrange the arrangement of the plurality of columnar members 53 so that the vertical spacers can be pulled out after applying pressure to the pressurized object 100.

  In the pressed body 100, spacers (first spacer 21 and second spacer 22) are disposed between the laminated structures 10. As described above, these spacers are used to prevent adhesion between adjacent laminated structures 10 and to facilitate separation after joining with a brazing material. On the other hand, the warpage of the laminated structure 10 (circuit board) after joining due to the difference in thermal expansion coefficients of the ceramic substrate 11, the metal circuit board 12, and the heat sink 13 can be reduced by using a thick and highly rigid spacer. it is obvious.

  On the other hand, the maximum height of the pressed body 100 is usually limited by the configuration of the joining jig. When the spacer is thick, the number of laminated structures 10 that can be joined simultaneously is reduced. That is, it is preferable that the spacer is thin from the viewpoint of reducing the manufacturing cost of the circuit board.

  For this reason, as shown in FIG. 2, the thick first spacers 21 and the thin second spacers 22 are preferably arranged alternately. In this case, since the first spacer 21 and the second spacer 22 are arranged on both upper and lower sides of any stacked structure 10, the pressure applied to each stacked structure 10 can be made uniform. it can. 2, an upper plate 51 is disposed above the uppermost laminated structure 10, and a bottom plate 50 is disposed below the lowermost laminated structure 10. Therefore, the first spacer 21 and the second spacer are arranged. Any of 22 may be arranged. Or it can also be set as the structure which does not distribute these spacers in the uppermost part and the lowest part in the to-be-pressurized body 10. FIG.

  In the above example, the case where the metal circuit board and the heat radiating plate are joined to the ceramic substrate with the brazing material has been described. Is clearly effective as well. For this reason, for example, the above-described configuration is effective even when a DBC (Direct Bonding Copper) that does not use brazing material is used. Further, for example, the same applies to a configuration using only a metal circuit board and no heat sink. Furthermore, in the above example, the case where the metal circuit board (metal plate) and the ceramic substrate are joined is described. However, it is effective when joining two kinds of rectangular flat plate members having different thermal expansion coefficients at a high temperature. It is also clear that there is.

(Example)
The circuit board (Example) that was actually bonded using the above-mentioned two vertical spacers, and the pressed member to be contacted and fixed to the columnar member without using the vertical spacer, and bonded The state of bonding in the circuit board (comparative example) was examined. Here, a 0.5 mm thick metal circuit board and a 0.5 mm thick heat sink were joined to a 0.32 mm thick ceramic substrate (silicon nitride ceramics) with an Ag—Cu—Ti brazing material. The joining at this time was performed in a reduced pressure atmosphere of about 0.01 Pa at about 800 ° C. when the brazing material was melted. The number of laminated structures laminated was 25, the first spacer was 3 mm thick, the second spacer was 1 mm thick, and these were used alternately. The pressure applied at the time of joining was about 9 kgf. The thickness of the two longitudinal spacers used in the examples was 3 mm.

  FIG. 3 is a result of the ultrasonic flaw detection apparatus showing the bonding state in the vicinity of the peripheral edge during bonding on the circuit boards of Comparative Example (a) and Example (b). In the figure, the left side shows the metal circuit board side, and the right side shows the heat sink side. Although the patterns are different between the example and the comparative example, since this patterning is performed after bonding, the difference in patterning is irrelevant to the bonding state. In FIG. 3, the upper side and the left side in the result on the metal circuit board side, and the upper side and the right side in the result on the heat sink side correspond to the peripheral edge at the time of joining.

  In the comparative example (a), there is an area that appears white at the peripheral edge. This region is a region where the bonding strength is low due to the presence of voids in the brazing material. As described above, this region is generated because the metal circuit board or the heat radiating plate thermally expands and comes into contact with the columnar member.

  On the other hand, in Example (b), the area | region which looks white at the peripheral part does not exist, and uniform joining strength is acquired.

10 Laminated structure 11 Ceramic substrate (first member)
12 Metal circuit board (metal plate; second member)
13 Heat sink (metal plate: second member)
21 First spacer (spacer)
22 Second spacer (spacer)
31, 32 Vertical spacer 50 Bottom plate 51 Top plate 52 Spring 53 Columnar member 54 Top plate 100 Pressurized object

Claims (7)

Both of them are rectangular flat plates and are joining methods for joining the first member and the second member having different thermal expansion coefficients at a high temperature,
A stacked structure in which the first member and the second member are stacked along the stacking direction, which is the normal direction of the surface in the flat plate shape, is stacked in multiple layers along the stacking direction via a flat spacer. A pressurized body preparation step of forming a pressurized body of a substantially rectangular body;
A plurality of columnar members are arranged in a row substantially parallel to three side surfaces parallel to the stacking direction of the pressed body, and the object to be pressed is spaced from the inside surrounded by the columnar members. In the joining jig having a configuration capable of accommodating the pressure body, the columnar members constituting the two rows out of the three rows that are not parallel to each other and the pressed body are in contact with each other via a vertical spacer, and the other 1 A pressurized body installation step of installing the pressurized body in an interior surrounded by the plurality of columnar members in a state where the pressurized body and the columnar member constituting the row are not in contact with each other;
A preparatory step of applying pressure along the stacking direction to the object to be pressurized and extracting the two vertical spacers from the joining jig;
A joining step of joining the first member and the second member by cooling after heating the joining jig on which the pressurized body is installed;
The joining method characterized by comprising. In the pressed object preparation step, the first member and the second member are laminated with a brazing material interposed therebetween,
The joining method according to claim 1, wherein in the joining step, the first member and the second member are joined by a brazing material.   The joining method according to claim 1 or 2, wherein the heating in the joining step is performed in a reduced-pressure atmosphere. In the pressurized object preparation step,
As the spacer, two types of spacers having different thicknesses are provided,
The joining method according to any one of claims 1 to 3, wherein the two types of spacers are alternately arranged in the stacking direction.   The joining method according to any one of claims 1 to 4, wherein the first member is a ceramic substrate, and the second member is a metal plate mainly composed of copper. . The ceramic substrate is larger in plan view than the metal plate,
In the joining preparation step,
6. The ceramic substrate is configured to protrude from the metal plate on a side surface parallel to the stacking direction of the pressed body on the side where the vertical spacer is not disposed. Joining method. Each is a rectangular flat plate and is used to join the first member and the second member having different thermal expansion coefficients at a high temperature, and the first member and the second member are in a flat plate shape. the pressure body formed by stacking a plurality in configured substantially rectangular body normal direction in which stacked along a stacking direction a stacked structure along the stacking direction of the plane, the stack in the target pressure body A plurality of columnar members are arranged in three rows substantially parallel to three side surfaces parallel to the direction, and the pressurized body can be accommodated in the interior surrounded by the plurality of columnar members, A joining jig comprising a configuration in which pressure is applied along the stacking direction with respect to the pressurized body in a state in which the pressurized body is accommodated,
The columnar members that are provided between each of the two rows out of the three rows that are not parallel to each other and the side surface of the pressed body that faces each of the two rows, and the column member that forms the other row The columnar members that are in contact with both of the columnar members that constitute each of the two rows in a state where they are not in contact with the pressure bodies and the pressed bodies, and that each of the two rows are configured in a state where the pressure is applied. A joining jig comprising two longitudinal spacers configured to be able to be pulled out from between a member and the pressed body.