Method for manufacturing a conjugate

Abstract

To provide a manufacturing method of a bonded body by which copper members are solid-phase diffusion bonded and which can suppress deformation of copper members during bonding and after bonding.SOLUTION: A manufacturing method of a bonded body 10, which is formed by bonding a first copper member 20 of which at least a bonded surface is formed of copper or a copper alloy and a second copper member 30 of which at least a bonded surface is formed of copper or a copper alloy, includes a lamination process of laminating the first copper member and the second copper member, and a bonding process of pressurizing and heating the laminated first copper member and second copper member in a lamination direction and solid-phase diffusion bonding the first copper member and second copper member. In the bonding process, a pressurization load in the lamination direction is in a range of 5-25 MPa, and a bonding temperature is in a range of 300-500°C.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a joined body in which a first copper member having at least a joining surface made of copper or a copper alloy and a second copper member having at least a joining surface made of copper or a copper alloy are joined together.

Background Art

[0002] Copper members made of copper or copper alloys are widely used in electronic and electrical components, heat dissipation components, etc. because they are excellent in electrical conductivity, thermal conductivity, have high mechanical strength, and have a large deformation resistance. Here, for example, when forming electronic and electrical components or heat dissipation components having a complex shape, copper members may be joined together.

[0003] When joining copper members, if a joining material such as solder is used, a joining layer is formed at the joining interface, and this joining layer may become a thermal resistance or an electrical resistance, resulting in a decrease in electrical conductivity and thermal conductivity. Further, if the heat resistance of the joining layer is low, there is a possibility that it cannot be stably used in a high-temperature environment.

[0004] Therefore, there is a need for a technique for directly joining copper members without using a joining material. Therefore, in Non-Patent Document 1, a technique for joining copper members by solid-phase diffusion bonding has been proposed.

Prior Art Documents

Non-Patent Documents

[0005]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Here, in Non-Patent Document 1, the pressure load during joining is set to 2 to 4 MPa, and the joining temperature is set to 800°C. When joining under high temperature conditions such as 800°C, the copper member may soften and deform under the pressure load during joining. In addition, by holding under high temperature conditions, the crystal grains of the copper member may coarsen and the strength may decrease. For this reason, the deformation resistance of the copper member becomes small, and there is a possibility that the joined copper member may deform during use. Furthermore, when a part of the member to be joined has a low melting point metal or the like, the low melting point member may melt during joining, and there is a possibility that solid phase diffusion joining cannot be performed.

[0007] This invention has been made in view of the above-described circumstances, and an object thereof is to provide a method for manufacturing a joined body in which copper members are solid phase diffusion joined and deformation of the copper members can be suppressed during and after joining.

Means for Solving the Problems

[0008] In order to solve such problems and achieve the above object, the method for manufacturing a joined body of the present invention is a method for manufacturing a joined body in which a first copper member having at least a joining surface made of copper or a copper alloy and a second copper member having at least a joining surface made of copper or a copper alloy are joined, the method including a laminating step of laminating the first copper member and the second copper member, and the laminated first copper member and the second copper member are In a vacuum atmosphere, pressurized and heated in the lamination direction to solid phase diffusion join the first copper member and the second copper member. In the joining step, the pressure load in the lamination direction is in the range of 5 MPa or more and 25 MPa or less, and the joining temperature is in the range of 300°C or more and 500°C or less wherein the first copper member has a plate shape, the second copper member has a pin shape, the end face of the second copper member is solid-phase diffusion bonded to the plate surface of the first copper member, and the length of the second copper member having a pin shape is in the range of 0.5 mm or more and 50 mm or less. which is characterized by this.

[0009] According to the method for manufacturing a joined body having this configuration, in the joining step of solid phase diffusion joining the first copper member and the second copper member, since the pressure load in the lamination direction is in the range of 5 MPa or more and 25 MPa or less, and the joining temperature is in the range of 300°C or more and 500°C or less, the first copper member and the second copper member can be directly joined by solid phase diffusion joining. Also, since the bonding temperature is in the range of 300°C or higher and 500°C or lower, it is possible to suppress softening of the first copper member and the second copper member, and to suppress deformation of the first copper member and the second copper member during bonding. Furthermore, coarsening of crystal grains in the first copper member and the second copper member can be suppressed, the deformation resistance of the first copper member and the second copper member after bonding can be maintained high, and deformation after bonding can be suppressed. In addition, the end face of the pin-shaped second copper member can be reliably joined to the plate surface of the plate-shaped first copper member, and a joined body having a structure in which the pin-shaped second copper member stands upright from the plate surface of the plate-shaped first copper member can be manufactured. A joined body having such a structure can be used as a heat sink having a pin fin structure.

[0010] Here, in the method for manufacturing the bonded body of the present invention, at least the bonding surfaces of the first copper member and at least the bonding surfaces of the second copper member may be made of oxygen-free copper. In this case, at least the bonding surfaces of the first copper member and at least the bonding surfaces of the second copper member are made of oxygen-free copper in which crystal grains are likely to coarsen. However, by setting the bonding temperature in the bonding process to be in the range of 300°C or higher and 500°C or lower, coarsening of crystal grains can be sufficiently suppressed, and the deformation resistance of the first copper member and the second copper member after bonding can be maintained high. Also, since oxygen-free copper is particularly excellent in electrical conductivity and thermal conductivity, it is possible to manufacture a bonding material that is particularly suitable as electronic and electrical components, heat dissipation components, etc.

Effects of the Invention

[0012] According to the present invention, it is possible to provide a method for manufacturing a bonded body in which copper members are solid-phase diffusion bonded and deformation of the copper members during and after bonding can be suppressed.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0014] Hereinafter, embodiments of the present invention will be described with reference to the drawings. It should be noted that each of the embodiments shown below is specifically described to better understand the gist of the invention, and unless otherwise specified, it does not limit the present invention. In addition, the drawings used in the following description may, for the sake of convenience, show an enlarged view of the main part to make the features of the present invention easier to understand, and the dimensional ratios of each component are not necessarily the same as the actual ones.

[0015] As shown in FIG. 1, the joined body in the present embodiment is a heat sink 10 having a pin-fin structure in which a copper plate 20 as a first copper member at least the joining surface of which is made of copper or a copper alloy and a pin member 30 as a second copper member at least the joining surface of which is made of copper or a copper alloy are joined together.

[0016] The copper plate 20 has a rectangular flat plate shape and its thickness is in the range of 0.2 mm or more and 10 mm or less. Further, the pin member 30 has a cylindrical shape, and the area of the end face (joining surface) is 0.5 mm 2 or more and 30 mm 2 or less, and its length is in the range of 0.5 mm or more and 50 mm or less.

[0017] In the present embodiment, the copper plate 20 and the pin member 30 are made of oxygen-free copper, and the plate surface of the copper plate 20 and the end face of the pin member 30 are joined by solid-phase diffusion bonding. In the present embodiment, as shown in FIG. 1, in the heat sink 10, the end faces of a plurality of pin members 30 are joined to the plate surface of the copper plate 20, and a structure is adopted in which a plurality of pin members 30 stand upright from the plate surface of the copper plate 20.

[0018] Next, a method for manufacturing the bonded body (heat sink 10) according to the present embodiment will be described with reference to FIGS. 2 and 3.

[0019] (Member preparation step S01) First, prepare the above-described copper plate 20 and pin members 30. Here, it is preferable to remove scratches and the like from the copper plate 20 and the pin members 30 in advance by polishing or the like and finish them to a smooth surface.

[0020] (Lamination step S02) Then, place the copper plate 20 on the carbon plate 41, and stack the pin members 30 so that the end faces (bonding surfaces) of the pin members 30 contact the plate surface (bonding surface) of the copper plate 20, and place the carbon plate 42 on the pin members 30. At this time, it is preferable to arrange the plurality of pin members 30 in a predetermined pattern using the positioning member 43.

[0021] (Bonding step S03) Next, load the stacked copper plate 20 and pin members 30 together with the carbon plates 41 and 42 into a vacuum furnace, apply pressure and heat in the stacking direction under a vacuum atmosphere, and perform solid-phase diffusion bonding between the copper plate 20 and the pin members 30. At this time, the applied pressure load in the stacking direction is in the range of 5 MPa or more and 25 MPa or less, the bonding temperature is in the range of 300°C or more and 500°C or less. Also, it is preferable that the holding time at the bonding temperature is in the range of 10 min or more, and it is preferable that the degree of vacuum is 0.0001 Pa or less.

[0022] Here, by setting the bonding temperature to 300°C or more, it becomes possible to perform solid-phase diffusion bonding between the copper plate 20 and the pin members 30. On the other hand, by setting the bonding temperature to 500°C or less, deformation of the copper plate 20 and the pin members 30 can be suppressed, and coarsening of crystals in the copper plate 20 and the pin members 30 can be suppressed.

[0023] In order to ensure solid-phase diffusion bonding between the copper plate 20 and the pin member 30, it is more preferable that the bonding temperature be 350°C or higher, and more preferably 400°C or higher. Further, in order to further suppress deformation of the copper plate 20 and the pin member 30 and coarsening of crystal grains, it is more preferable that the bonding temperature be 480°C or lower.

[0024] Also, by setting the pressing load to 5 MPa or more, it becomes possible to perform solid-phase diffusion bonding between the copper plate 20 and the pin member 30. On the other hand, by setting the pressing load to 25 MPa or less, deformation of the copper plate 20 and the pin member 30 can be suppressed.

[0025] In order to ensure solid-phase diffusion bonding between the copper plate 20 and the pin member 30, it is more preferable that the pressing load be 8 MPa or more, and more preferably 10 MPa or more. Further, in order to further suppress deformation of the copper plate 20 and the pin member 30, it is more preferable that the pressing load be 20 MPa or less.

[0026] In addition, it is more preferable that the holding time at the bonding temperature be 30 min or more, and more preferably 60 min or more.

[0027] Through the above steps, the copper plate 20 and the pin member 30 are solid-phase diffusion bonded, and the heat sink 10 having a structure in which a plurality of pin members 30 stand upright from the plate surface of the copper plate 20 can be manufactured.

[0028] According to the manufacturing method of the bonded body (heat sink 10) of the present embodiment configured as described above, in the bonding step S03 of solid-phase diffusion bonding between the copper plate 20 as the first copper member and the pin member 30 as the second copper member, the pressing load in the stacking direction is in the range of 5 MPa or more and 25 MPa or less, and the bonding temperature is in the range of 300°C or more and 500°C or less. Therefore, the copper plate 20 and the pin member 30 can be directly bonded by solid-phase diffusion bonding, and the heat sink 10 having a pin fin structure can be manufactured.

[0029] Also, in the bonding step S03, since the bonding temperature is set to 500°C or lower, softening of the copper plate 20 and the pin member 30 can be suppressed, and deformation of the copper plate 20 and the pin member 30 during bonding can be suppressed. Furthermore, coarsening of crystal grains in the copper plate 20 and the pin member 30 can be suppressed, the deformation resistance of the copper plate 20 and the pin member 30 after bonding can be maintained high, and deformation of the heat sink 10 formed after bonding can be suppressed.

[0030] Also, in the present embodiment, the copper plate 20 and the pin member 30 are made of oxygen-free copper in which crystal grains are likely to coarsen. However, since the bonding temperature in the bonding step S03 is set to 500°C or lower, coarsening of crystal grains can be sufficiently suppressed, and the deformation resistance of the copper plate 20 and the pin member 30 after bonding can be maintained high. Furthermore, since oxygen-free copper is particularly excellent in heat conductivity, a heat sink 10 having excellent heat dissipation characteristics can be formed.

[0031] As described above, the embodiments of the present invention have been described. However, the present invention is not limited to this, and can be appropriately modified without departing from the technical idea of the invention. For example, in the present embodiment, the copper plate (first copper member) and the pin member (second copper member) are solid-phase diffusion bonded to manufacture a heat sink (bonded body) having a pin fin structure. However, the present invention is not limited to this, and at least a first copper member in which at least the bonding surface is made of copper or a copper alloy, and at least a second copper member in which at least the bonding surface is made of copper or a copper alloy, may be used as long as a bonded body obtained by solid-phase diffusion bonding is manufactured.

[0032] For example, as shown in FIG. 4, a heat sink-equipped insulating circuit board 110 may be manufactured that includes an insulating circuit board 120 in which a circuit layer 122 is formed on one surface (the upper surface in FIG. 4) of a ceramic substrate 121 and a metal layer 123 is formed on the other surface (the lower surface in FIG. 4) of the ceramic substrate 121, and a heat sink 130 in which copper layers 132 are formed on both surfaces of a Cu-Mo plate 131.

[0033] In the insulated circuit board 110 with a heat sink shown in FIG. 4, the metal layer 123 of the insulated circuit board 120 is made of copper or a copper alloy, and the metal layer 123 and the copper layer 132 of the heat sink 130 are solid-phase diffusion bonded. That is, the insulated circuit board 120 is used as the first copper member, and the heat sink 130 is used as the second copper member. Even in this case, by performing the lamination step S02 and the bonding step S03 shown in the embodiment, the insulated circuit board 120 and the heat sink 130 can be solid-phase diffusion bonded, and the insulated circuit board 110 with a heat sink, which is a bonded body, can be manufactured.

[0034] Further, as shown in FIG. 5, an insulated circuit board 210 including an insulated circuit board 220 in which a circuit layer 222 is formed on one surface (the upper surface in FIG. 5) of a ceramic substrate 221 and a metal layer 223 is formed on the other surface (the lower surface in FIG. 5) of the ceramic substrate 221, and a heat sink 230 made of copper or a copper alloy may be manufactured. Here, in the insulated circuit board 220 shown in FIG. 5, the circuit layer 222 and the metal layer 223 have a structure in which aluminum layers 222A and 223A and copper layers 222B and 223B are laminated, and the copper layers 222B and 223B are disposed on the outermost layer.

[0035] In the insulated circuit board 210 with a heat sink shown in FIG. 5, the copper layer 223B of the metal layer 223 of the insulated circuit board 220 and the heat sink 230 are solid-phase diffusion bonded. That is, the insulated circuit board 220 is used as the first copper member, and the heat sink 230 is used as the second copper member. Even in this case, by performing the lamination step S02 and the bonding step S03 shown in the embodiment, the insulated circuit board 220 and the heat sink 230 can be solid-phase diffusion bonded, and the insulated circuit board 210 with a heat sink, which is a bonded body, can be manufactured. Further, since the bonding temperature in the bonding step S03 is 500° C. or lower, melting of the aluminum layers 222A and 223A during solid-phase bonding can be suppressed.

Example

[0036] An experimental study was conducted to verify the effectiveness of the present invention.

[0037] First, as shown in Table 1, a first copper plate (15 mm × 15 mm, thickness 0.8 mm) and a second copper plate (35 mm × 35 mm, thickness 5 mm) were prepared. With the bonding surfaces of the first and second copper plates polished in advance to a smooth surface, the first and second copper plates were laminated. The laminated first and second copper plates were placed in a vacuum furnace and were pressed and heated under the conditions shown in Table 1 in an atmosphere with a vacuum degree of 0.0001 Pa to solid-phase diffusion bond the first and second copper plates.

[0038] For the bonded body obtained as described above, the presence or absence of deformation of the bonded body, the bonding rate after thermal cycling load, and the Vickers hardness of the bonded body were evaluated as follows. The evaluation results are shown in Table 1.

[0039] (Presence or absence of deformation of the bonded body) When the total thickness after bonding (the sum of the thicknesses of the first and second copper plates) was 99% or less of that before bonding, it was evaluated as having deformation.

[0040] (Bonding rate after thermal cycling load) Using a thermal shock tester TSB-51 manufactured by ESPEC Corporation, a thermal cycle of -40°C × 10 minutes ←→ 150°C × 10 minutes was performed on the bonded body in a liquid phase (fluorinate) for 3000 cycles. Then, the bonding rate of the bonded body after the thermal cycle test was evaluated using an ultrasonic flaw detector (FineSAT200 manufactured by Hitachi Power Solutions Co., Ltd.) and calculated from the following formula. Here, the initial bonding area was defined as the area to be bonded before bonding. Since peeling is indicated by the white part within the bonded part in the binarized image of the ultrasonic flaw detection image, the area of this white part was defined as the peeled area. (Bonding rate) = {(Initial bonding area) - (Unbonded part area)} / (Initial bonding area) × 100

[0041] (Vickers hardness) The Vickers hardness of the surface of the second copper plate was measured. The measurement was carried out using a diamond indenter with a regular square pyramid and by the method specified in JIS Z 2244 using a semi-Vickers hardness tester (HSV-30 manufactured by Shimadzu Corporation).

[0042]

Table 1

[0043] In Comparative Example 1, the bonding temperature in the bonding process was 200 °C, and the bonding rate after the thermal cycle load was 0%. In Comparative Example 2, the bonding temperature in the bonding process was 800 °C, and deformation of the bonded body was observed. Also, the Vickers hardness was 29.5 HV, and the bonded body (the first copper plate and the second copper plate) was softened.

[0044] In Comparative Example 3, the pressing load in the bonding process was 1 MPa, and the bonding rate after the thermal cycle load was 0%. In Comparative Example 4, the pressing load in the bonding process was 50 MPa, and deformation of the bonded body was observed.

[0045] On the other hand, in Invention Examples 1 to 7, the bonding temperature in the bonding process was in the range of 300 °C or more and 500 °C or less, and the pressing load was in the range of 5 MPa or more and 25 MPa or less. There was no deformation of the bonded body, the bonding rate after the thermal cycle load was 98% or more, and the first copper plate and the second copper plate could be firmly solid-phase diffusion bonded. Also, the Vickers hardness was 41.0 HV or more, and softening of the bonded body (the first copper plate and the second copper plate) was suppressed.

[0046] As a result of the above confirmation experiments, it was confirmed that according to the invention examples, it is possible to provide a method for manufacturing a bonded body in which copper members are solid-phase diffusion bonded and deformation of the copper members is suppressed during and after bonding.

Explanation of Reference Signs

[0047] 10 Heat sink (joint) 20 Copper plate (first copper member) 30 Pin member (second copper member) 110 Insulated circuit board with heat sink (joint) 120 Insulated circuit board (first copper member) 130 Heat sink (second copper member) 210 Insulated circuit board with heat sink (joint) 220 Insulated circuit board (first copper member) 230 Heat sink (second copper member)

Claims

1. A method for manufacturing a joined body in which a first copper member having at least a joint surface made of copper or a copper alloy and a second copper member having at least a joint surface made of copper or a copper alloy are joined, comprising: a laminating step of laminating the first copper member and the second copper member; a joining step of pressurizing and heating the laminated first copper member and second copper member in a vacuum atmosphere in the lamination direction to perform solid-phase diffusion joining between the first copper member and the second copper member; and in the joining step, the pressing load in the lamination direction is in the range of 5 MPa or more and 25 MPa or less, and the joining temperature is in the range of 300°C or more and 500°C or less; the first copper member has a plate shape, the second copper member has a pin shape, and the end surface of the second copper member is solid-phase diffusion joined to the plate surface of the first copper member, and the length of the second copper member having a pin shape is in the range of 0.5 mm or more and 50 mm or less. A method for manufacturing a joined body, characterized by the above.

2. The method for manufacturing a joined body according to claim 1, wherein at least the joint surface of the first copper member and at least the joint surface of the second copper member are made of oxygen-free copper.

Images