Method for transporting laminated body, method for manufacturing bonded body using same, and method for manufacturing ceramic circuit board

Abstract

To provide a method for transporting a laminate that suppresses positional deviation of a metal plate during a transport process.SOLUTION: A method according to an embodiment that transports a laminate in which a brazing material layer and a metal plate are laminated on at least one surface of a ceramic substrate includes the steps of storing the laminate in a transport container, tilting the transport container, and transporting the transport container. In addition, the step of transporting the transport container is preferably performed in a tilted state. In addition, in the step of tilting the transport container, the angle at which the transport container is tilted is preferably within a range of 5° to 30°.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The embodiments described below generally relate to a method for transporting a laminate, a method for manufacturing a bonded body using the laminate, and a method for manufacturing a ceramic circuit board. [Background technology]

[0002] In recent years, semiconductor elements have become more and more sophisticated. As this advancement in performance continues, the amount of heat generated by semiconductor elements has also increased. Ceramic circuit boards are used as circuit boards on which semiconductor elements are mounted. Ceramic circuit boards with good TCT (thermal cycle test) characteristics have been developed. For example, in Japanese Patent No. 6789955 (Patent Document 1), the TCT characteristics are improved by controlling the size of the protruding portion of the bonding layer. Ceramic circuit boards are made by heat-bonding a laminate consisting of a ceramic substrate, a brazing filler layer, and a metal plate. To obtain a laminate consisting of a ceramic substrate, a brazing filler layer, and a metal plate, it is necessary to align and position the components. For example, Japanese Patent No. 6314567 (Patent Document 2) discloses a method in which a ceramic substrate is fixed with guide pins, and a brazing material layer and a metal plate are arranged. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6789955 [Patent Document 2] Patent No. 6314567 Summary of the Invention [Problem to be solved by the invention]

[0004] The method of Patent Document 2 allows for accurate alignment. However, in order to heat-bond the laminate, it is necessary to transport it to a heat-bonding device. This has led to problems such as the metal plates becoming misaligned during the transport process after the laminate is produced. The embodiment is intended to provide a method for transporting a laminate that suppresses positional displacement of metal plates during the transport process. [Means for solving the problem]

[0005] The method for transporting a laminate according to the embodiment is a method for transporting a laminate in which a brazing material layer and a metal plate are laminated on at least one surface of a ceramic substrate, and is characterized by comprising the steps of storing the laminate in a transport container, tilting the transport container, and transporting the transport container. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a diagram showing an example of a laminate according to an embodiment. [Figure 2] 5A to 5C are diagrams illustrating an example of a transport process of a laminate according to an embodiment. [Figure 3] FIG. 10 is a diagram showing another example of a transport process of a laminate according to an embodiment. [Figure 4] FIG. 1 is a diagram showing an example of a bonded body according to an embodiment. [Figure 5] 1 is a diagram showing an example of a ceramic circuit substrate according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0007] The method for transporting a laminate according to an embodiment is a method for transporting a laminate in which a brazing material layer and a metal plate are stacked on at least one surface of a ceramic substrate, storing the laminate in a transport container; tilting the transport container; conveying the conveying container; It is characterized by having: An example of the laminate is shown in Figure 1. An example of a method for transporting the laminate is shown in Figures 2 and 3. In the figure, reference numeral 1 denotes a laminate, reference numeral 2 denotes a ceramic substrate, reference numeral 3 denotes a metal plate, reference numeral 4 denotes a brazing material layer, reference numeral 5 denotes a transport container, reference numeral 6 denotes a setter, and reference numeral 7 denotes a transport device. The laminate 1 has a brazing filler metal layer 4 and a metal plate 3 laminated on a ceramic substrate 2. FIG. 1 shows the brazing filler metal layer 4 and the metal plate 3 laminated on both sides of the ceramic substrate 2. The laminate 1 is not limited to this structure. For example, the brazing filler metal layer 4 and the metal plate 3 may be laminated on only one side of the ceramic substrate 2. Alternatively, the laminate 1 may have a multilayer structure in which the three-layer structure of ceramic substrate 2 / brazing filler metal layer 4 / metal plate 3 is repeated.

[0008] First, the laminate 1 is prepared. Next, a step of storing the laminate in a transfer container is performed. The transfer container 5 in FIG. 2 is exemplified as having a U-shaped cross section. The transfer container 5 has at least a bottom surface on which the laminate 1 is placed and side surfaces for aligning the laminate 1. The top surface of the transfer container 5 can be used as a place to fix the laminate 1 to the transfer device 7. Fixing to the transfer device may be performed using a robot such as suction. The transfer device 7 may be fixed to the side or bottom surface of the transfer container 5. The side surfaces may also be provided on the sides of the transfer container 5. The laminate 1 may be pre-stacked or may be stacked inside the transfer container 5. Furthermore, multiple laminates 1 may be stored in a transport container 5. The multiple laminates may be arranged side by side or stacked. FIG. 2 illustrates an example of a stacked arrangement of multiple laminates 1. When multiple laminates 1 are stored in a storage container 5, it is preferable to place a setter 6 between the laminates 1. The setter 6 is one that does not deform at the temperature of the thermal bonding process. Examples of such a setter include a boron nitride plate or a carbon plate. The number of setters 6 to be placed is arbitrary. The setter 6 may be placed between individual laminates 1. Alternatively, a setter 6 may be placed for each of multiple laminates 1. It is also preferable to place the setter 6 between individual laminates 1. By placing the setter 6 between the laminates 1, it is possible to prevent the metal plates from burning together during the thermal bonding process.

[0009] Next, the transfer container is tilted. By tilting the transfer container 5, the stack 1 gathers on the side of the transfer container 5. In other words, the side of the transfer container 5 serves to align the stack 1. Furthermore, in the transfer container tilting step, the tilt angle of the transfer container is preferably within a range of 5° to 30°. The angle θ at which the transfer container is tilted is counted as 0° when the stack 1 is positioned horizontally. If the tilt angle θ of the transfer container is less than 5°, the tilt is small, which may result in inconsistencies in the alignment of the stack 1. If the angle θ exceeds 30°, further benefits may not be achieved. Furthermore, the surface of the metal plate 3 may be scratched during the alignment of the stack 1. For this reason, the tilt angle θ of the transfer container is preferably within a range of 5° to 30°, and more preferably within a range of 7° to 20°. The angle θ is the angle of tilt in one or both of the X-axis and Y-axis directions. For convenience, the X direction is the longitudinal direction of the laminate 1, and the Y axis direction is the direction of the short side of the laminate 1.

[0010] FIG. 4 shows an example of the laminate 1 after alignment. In the figure, reference numeral 2 denotes the ceramic substrate, and reference numeral 3 denotes the metal plate. This shows the state in which the metal plate 3 has been aligned by tilting the transport container. FIG. 4(a) shows the state in which one side of the ceramic substrate 2 is aligned with one side of the metal plate 3. FIG. 4(b) shows the state in which two sides of the ceramic substrate 2 are aligned with two sides of the metal plate 3. For example, if an angle θ is applied in either the X-axis direction or the Y-axis direction, the result will likely be as shown in FIG. 4(a). If an angle θ is applied in both the X-axis direction and the Y-axis direction, the result will likely be as shown in FIG. 4(b). It is preferable that the creepage distance of at least one side of the ceramic substrate and the metal plate be within the range of 0 mm to 0.5 mm by the process of tilting the transfer container. As described above, the creepage distance can be reduced by aligning one or two sides of the ceramic substrate 2 and the metal plate 3. Furthermore, considering the accuracy of alignment, it is preferable that the creepage distance be 0 mm. The creepage distance is calculated by rounding off to one decimal place. It is also preferable that the creepage distance exceeds 0.5 mm on at least one side of the ceramic substrate 2 and the metal plate 3. The creepage distance is 0 mm or more and 0.5 mm or less where one or two sides of the ceramic substrate 2 and the metal plate 3 are aligned. It is preferable that the creepage distance exceeds 0.5 mm on the sides that are not aligned.

[0011] For example, even if the creepage distance is set to 0.5 mm or less beforehand when placing the metal plate 3 on the ceramic substrate 2 and the brazing filler metal layer 4, the metal plate 3 may shift during transportation. For this reason, it is effective to align the metal plate 3 by tilting the transport container 5. To prevent the metal plate 3 from shifting during transportation, it is effective to transport the transport container 5 while tilted. Furthermore, the creepage distance can be controlled by tilting the transfer container 5. Therefore, even if the metal plates 3 are misaligned when the laminate 1 is produced, they can be aligned during the transfer process. In other words, even if the placement accuracy of the metal plates 3 is poor when the laminate 1 is produced, the creepage distance can be controlled during the transfer process. Furthermore, by tilting the transport container 5, the creepage distance of the metal plate 3 can be set within the range of 0 mm to 0.5 mm. As the metal plate 3 moves, the brazing filler metal layer 4 also moves. As will be described later, the active metal brazing filler metal is applied as a paste to form the brazing filler metal layer 4. Because the paste is viscous, it moves along with the metal plate 3 when it moves. Furthermore, the brazing filler metal layer may be applied widely in advance, taking into account the range over which the metal plate will move. Furthermore, it is preferable that the process of transporting the transport container 5 is mechanized. Mechanization refers to a process using a robot. By automating the process using a robot, it becomes easier to control the angle θ. After the conveying step, the conveyed laminate is subjected to a step of heat bonding. A bonded body can be obtained by performing the heat bonding step. Furthermore, by performing the heat bonding step, the brazing material layer 4 becomes the bonding layer 10. In the obtained bonded body, at least one side of the ceramic substrate and the metal plate has a creepage distance in the range of 0 mm to 0.5 mm.

[0012] Furthermore, the bonded structure according to the embodiment can be used for a ceramic circuit board. FIG. 5 shows an example of a ceramic circuit board. In the figure, reference numeral 2 denotes a ceramic substrate, reference numeral 8 denotes a circuit board, reference numeral 9 denotes a heat sink, reference numeral 10 denotes a bonding layer, and reference numeral 11 denotes a ceramic circuit board. In FIG. 5, the front metal plate is the circuit board 8, and the back metal plate is the heat sink 9. The ceramic circuit board according to the embodiment is not limited to this structure, and both sides may be provided with a circuit board 8. Furthermore, although FIG. 5 shows an example with two circuit boards 8, the number of circuit boards 8 can be increased as needed. Furthermore, by imparting a circuit shape to the metal plate 3, it becomes a circuit plate 8. The process of imparting the circuit shape is preferably an etching process. The etching process is a method of removing the metal plate using a chemical solution. In the etching process, resist is applied to the areas where the circuit shape is to be left. The resist application process is mechanized. The position where the resist is applied is detected according to the circuit shape. The edge of the ceramic substrate 2 or metal plate 3 is used to detect the position. The edge of the ceramic substrate 2 or metal plate 3 is detected by a detector. The detector may be a CCD camera or the like. Position detection can be performed based on a point on at least one side of the ceramic substrate and metal plate where the creepage distance is in the range of 0 mm to 0.5 mm. Position detection can also be performed using a point where the creepage distance exceeds 0.5 mm.

[0013] To make the creepage distance 0 mm, it is possible to make the length and width of the ceramic substrate 2 and the metal plate 3 the same. If the length and width are the same, misalignment may occur during transportation. Furthermore, the degree of misalignment is likely to vary from one plate to another, reducing the accuracy of position detection. If the accuracy of position detection decreases, the position of the resist coating will shift. Misalignment in the position of the resist coating will lead to misalignment of the circuit shape. By tilting the transport container, it is possible to create a location where the creepage distance is in the range of 0 mm to 0.5 mm. This allows the positions of the ceramic substrate 2 and the metal plate 3 to be constant. Furthermore, by transporting the transport container while tilting it, it is possible to prevent the metal plate from shifting during transport. From this point of view, it is preferable to have a location where the creepage distance is 0 mm. Furthermore, the presence of locations where the creepage distance is between 0 mm and 0.5 mm and locations where the creepage distance exceeds 0.5 mm improves position detection accuracy. For example, when using a CCD camera, position detection is performed using the difference in contrast. The presence of locations where the creepage distance exceeds 0.5 mm makes it easier to detect the edge of the ceramic substrate. In other words, misalignment of the metal plate is prevented at locations where the creepage distance is less than 0.5 mm, and the position detection accuracy of the edge of the ceramic substrate is improved at locations where the creepage distance exceeds 0.5 mm. This prevents misalignment of the resist application position. In other words, this is suitable for ceramic circuit boards that are coated with resist and then subjected to an etching process. Furthermore, an etching process may be used to impart an inclined shape to the side surfaces of the circuit board 8 and the heat sink 9. Furthermore, a bonding layer protrusion may be provided by causing the bonding layer to protrude from the end portions of the circuit board 8 and the heat sink 9.

[0014] Various ceramic substrates can be used for the ceramic substrate 2. Examples of ceramic substrates include silicon nitride substrates, aluminum nitride substrates, alumina substrates, zirconia substrates, and alu-zirconia substrates. The alu-zirconia substrate is a sintered ceramic body made of a mixture of alumina and zirconia. The thickness of the ceramic substrate 2 is preferably in the range of 0.2 mm to 3 mm. The silicon nitride substrate preferably has a three-point bending strength of 600 MPa or more. It also preferably has a thermal conductivity of 80 W / m·K or more. By increasing the strength of the silicon nitride substrate, the substrate thickness can be reduced. Therefore, the silicon nitride substrate's three-point bending strength is preferably 600 MPa or more, and more preferably 700 MPa or more. The silicon nitride substrate can be made as thin as 2 mm or less, or even 0.40 mm or less. Furthermore, the three-point bending strength of an aluminum nitride substrate is approximately 300 to 450 MPa. On the other hand, the thermal conductivity of an aluminum nitride substrate is 160 W / m·K or more. Because the strength of an aluminum nitride substrate is low, the substrate thickness is preferably 0.60 mm or more. Aluminum oxide substrates have a three-point bending strength of around 300 to 450 MPa but are inexpensive, while aluminium substrates have a high three-point bending strength of around 550 MPa but a thermal conductivity of around 30 to 50 W / m·K. A silicon nitride substrate is preferable as the ceramic substrate 2. A silicon nitride substrate has high strength, so it will not be damaged by the impact when the transfer container 5 is tilted. The metal plate 3 may be a copper plate (including copper alloys) or an aluminum plate (including aluminum alloys). The copper plate may be an oxygen-free copper plate. Oxygen-free copper has a copper purity of 99.96 wt% or more as specified in JIS-H-3100.

[0015] The brazing filler metal is preferably an active metal brazing filler metal. The active metal brazing filler metal used to join copper plates contains titanium (Ti). Ti is an active metal. Ti reacts with the ceramic substrate to improve the joining strength. The Ti used in the active metal brazing filler metal can be titanium or titanium hydride (TiH2). The active metal brazing filler metal preferably contains one or more elements selected from Ag (silver), Cu (copper), Sn (tin), In (indium), and C (carbon). The active metal brazing filler metal preferably contains Ti, one or more elements selected from Cu or Ag, and one or more elements selected from Sn, In, or C. The components of the active metal brazing material include 1% to 15% by mass of Ti (titanium) or TiH2 (titanium hydride), 15% to 85% by mass of Cu (copper), and 0% to 70% by mass of Ag (silver), 1% to 50% by mass of one or two elements selected from Sn (tin) and In (indium), and 0.1% to 2% by mass of C (carbon). Furthermore, the active metal brazing filler metal used to join aluminum plates is preferably an Al-based brazing filler metal containing one or both of silicon (Si) and magnesium (Mg). Si or Mg serves as the active metal. As a component of the active metal brazing filler metal, the Si content is preferably in the range of 0.01% by mass to 20% by mass. The Mg content is preferably in the range of 0.01% by mass to 20% by mass. The thermal bonding method using an active metal brazing material is called the active metal bonding method. The active metal brazing material is mixed with a binder or a solvent to prepare an active metal brazing material paste. By making it into a paste, the brazing material layer 4 can also move in accordance with the movement of the metal plate 3 when the transport container 5 is tilted. Furthermore, if the movement range of the metal plate 3 is large, the brazing material paste may be applied widely in advance. An active metal brazing paste is applied to a ceramic substrate 2, and a metal plate 3 is placed thereon. This process produces a laminate 1. In the heat bonding process, the bonding temperature is preferably within a range of 600°C or higher and 980°C or lower. The method for transporting a laminate according to the embodiment can suppress misalignment between the ceramic substrate 2 and the metal plate 3 during transport, thereby improving the yield of the bonded body. Also, it can suppress variations in the circuit shape during the etching process.

[0016] (Example) (Examples 1 to 4, Comparative Example 1) A Ti-containing active metal brazing material was applied to both sides of a silicon nitride substrate (200 mm long x 160 mm wide x 0.32 mm thick), and a copper plate (195 mm long x 150 mm wide x 0.8 mm thick) was placed on top to create a laminate. A U-shaped cross section was used as the transport container. In other words, the transport container had a bottom, side, and top surface. The laminates and setters were stacked alternately in a transport container. The number of stacks is the number of laminates. For example, if the stacking arrangement is laminate / setter / laminate / setter, the number of stacks is two. The transport process was carried out as shown in Table 1. The transport process was mechanized.

[0017] [Table 1]

[0018] As can be seen from the table, in Examples 1 to 4, locations where the creepage distance was 0 mm or more and 0.5 mm or less were formed. In Example 1, since the plate was tilted only in the X-axis direction, there was only one side where the creepage distance was 0 mm or more and 0.5 mm or less. In Examples 2 to 4, since the plate was tilted in both the X-axis and Y-axis directions, there were two sides where the creepage distance was 0 mm or more and 0.5 mm or less. In Comparative Example 1, the plate was not transported while tilted, so no locations where the creepage distance was 0 mm or more and 0.5 mm or less were formed. Furthermore, in Comparative Example 1, there was variation in the creepage distance. This is because the metal plate was misaligned during transport.

[0019] Next, the laminate was heated and bonded to form a laminate, and then a resist coating step and an etching step were carried out to form a ceramic circuit board. In the resist application process, the position was detected using a CCD camera and the resist was applied. The position detection using the CCD camera was performed based on the point where the creepage distance exceeded 0.5 mm. Products that were within a range of 0 mm to 0.3 mm from the intended resist application position were deemed to be good products. Products in which even one location where the resist was misaligned by 0.4 mm or more were observed were deemed to be defective products. Products with a good product rate of 99% to 100% were rated as ◎, products with a good product rate of 95% to 99% were rated as 〇, and products with a good product rate of less than 95% were rated as ×. The results are shown in Table 2.

[0020] [Table 2]

[0021] In the example, the deviation of the resist application position was reduced. Therefore, the deviation of the circuit shape after the etching process was also suppressed. In contrast, in the comparative example 1, the deviation of the resist application position was large, causing variations in the circuit shape after etching. The method for manufacturing a ceramic circuit board according to the embodiment can produce a circuit board with reduced variation in circuit shape at a high yield.

[0022] Although several embodiments of the present invention have been described above, these embodiments are presented by way of example only and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, modifications, etc. can be made without departing from the spirit of the invention. Modifications of these embodiments are included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as set forth in the claims. Furthermore, the above-described embodiments can be implemented in combination with each other. [Explanation of symbols]

[0023] 1...Laminate 2...Ceramic substrate 3...Metal plate 4...Brazing layer 5...Transport container 6...Setter 7...Transportation device 8...Circuit board 9…Heat sink 10...Joining layer 11...Ceramic circuit board

Claims

1. A method for transporting a laminate in which a brazing material layer and a metal plate are laminated on at least one surface of a ceramic substrate, the method comprising: storing the laminate in a transport container; tilting the transport container so that the creepage distance between at least one side of the ceramic substrate and the metal plate is within a range of 0 mm to 0.5 mm, and the creepage distance between at least one side of the ceramic substrate 2 and the metal plate 3 is greater than 0.5 mm; a step of transporting the transport container in a tilted state; A method for transporting a laminate, comprising:

2. 2. The method for transporting laminates according to claim 1, wherein the step of storing the laminates in a transport container stores a plurality of laminates in the transport container via a setter.

3. 3. The method for transporting a laminate according to claim 1, wherein in the step of tilting the transport container, the angle at which the transport container is tilted is within a range of 5 degrees to 30 degrees.

4. 3. The method for transporting a laminate according to claim 1, wherein the step of tilting the transport container causes the creepage distance of at least one side of the ceramic substrate and the metal plate to be 0 mm.

5. 4. The method for transporting a laminate according to claim 3, wherein the step of tilting the transport container causes the creepage distance of at least one side of the ceramic substrate and the metal plate to be 0 mm.

6. 3. The method for transporting a laminate according to claim 1, wherein the ceramic substrate is a silicon nitride substrate, the metal plate is a copper plate, and the brazing material layer is an active metal brazing material.

7. 3. A method for producing a bonded body, comprising a step of heat-bonding a laminate transported by the laminate transport method according to claim 1.

8. 7. A method for producing a bonded body, comprising the step of heat-bonding a laminate transported by the laminate transport method according to claim 6.

9. 8. A method for producing a ceramic circuit board, comprising the steps of: applying a resist to the metal plate of the bonded body obtained by the method for producing a bonded body according to claim 7; and etching the metal plate.

10. 9. A method for producing a ceramic circuit board, comprising the steps of: applying a resist to the metal plate of the bonded body obtained by the method for producing a bonded body according to claim 8; and etching the metal plate.

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