JP7571982B2 - Ceramic-Metal Joint Parts - Google Patents

Description

The present invention relates to ceramic-metal joint parts.

When a semiconductor is attached to an insulating substrate, it is joined to a heat dissipating metal plate on the back side of the insulating substrate through a metal part, but a structure has been proposed in which the metal part is not fixed to the insulating substrate, thereby suppressing thermal stress (see, for example, Patent Document 1). Also, a method has been proposed in which a concave surface is provided on the side of the through hole when inserting a through conductor into the insulating plate, thereby alleviating thermal stress there (see, for example, Patent Document 2).

Patent Publication No. 5747805 JP 2013-115123 A

However, in a ceramic-metal joint component formed by joining a ceramic member and a metal member, if the metal member is locally heated in order to join it to another metal member, the thermal stress acting on the ceramic member may become excessive, which may cause cracks.

The present invention aims to provide a ceramic-metal bonded component that can reduce the thermal stress acting on the ceramic member when the metal member is locally heated or the temperature is increased.

According to the ceramic-metal bonding part of the present invention,
A plate-shaped metal member is joined to the ceramic member in a joining region excluding a designated region, which is a part of one main surface facing the ceramic member,
The other main surface of the metal member, which is opposite to the one main surface, is locally raised in the specified region.

In the ceramic-metal joint component having the above configuration,
It is preferable that the one main surface of the metal member is locally recessed in the specified region.

In the ceramic-metal joint component having the above configuration,
It is preferable that the designated region includes a part of the outer edge of the one main surface of the metal member.

In the ceramic-metal joint component having the above configuration,
It is preferable that the gap between a portion of the outer edge of the one main surface of the metal member and the ceramic member is sealed by a sealing member made of a different material extending along a portion of the outer edge of the one main surface of the metal member.

FIG. 1 is an exploded view of a ceramic-metal bonded part according to one embodiment of the present invention. 1 is a top view of a ceramic-metal bonded part according to one embodiment of the present invention; 3 is a cross-sectional view of the ceramic-metal joint part taken along line III-III in FIG. 2 . FIG. 4 is an explanatory diagram of the arrangement of a designated area (non-joint portion) in the first embodiment. FIG. 11 is an explanatory diagram of an arrangement of designated areas in the second embodiment. FIG. 13 is an explanatory diagram of an arrangement of designated areas in the third embodiment. FIG. 13 is an explanatory diagram of an arrangement of designated areas in the fourth embodiment. FIG. 13 is an explanatory diagram of an arrangement of designated areas in the fifth embodiment. FIG. 23 is an explanatory diagram of an arrangement of designated areas in the sixth embodiment. FIG. 23 is an explanatory diagram of an arrangement of designated areas in the seventh embodiment. FIG. 23 is an explanatory diagram of an arrangement of designated areas in the eighth embodiment. FIG. 23 is an explanatory diagram of an arrangement of designated areas in the ninth embodiment.

(composition)
The ceramic-metal bonded component according to one embodiment of the present invention shown in FIG. 1 includes a ceramic member 10, a first metal member 21, and a second metal member 22.

The ceramic member 10 is composed of a ZnO-based ceramic sintered body formed into a substantially rectangular plate shape with rounded corners. Silver paste 12 is provided or applied to the center of each of the upper surface (one of the main surfaces) and the lower surface (the other main surface) of the ceramic member 10.

The first metal member 21 is composed of a copper or copper alloy plate formed into a generally rectangular shape with rounded corners that is smaller than the ceramic member 10. The first metal member 21 is joined to the upper surface of the ceramic member 10 via a first solder layer 41 and silver paste 12.

2, the first metal member 21 has a flat raised portion 210 that is locally raised from the surrounding area in a substantially rectangular designated region. That is, as shown in FIG. 3, the upper surface (the other main surface) of the first metal member 21 opposite the lower surface (one main surface) that is the bonding surface to the ceramic member 10 locally rises upward in the designated region where the raised portion 210 is provided. Also, the lower surface of the first metal member 21 locally recesses upward in the designated region. As shown in FIG. 3, the raised portion 210 forms a gap C between the first metal member 21 and the first solder layer 41, so that the first metal member 21 and the ceramic member 10 are not locally bonded in the designated region where the raised portion 210 is provided.

The second metal member 22 is composed of a copper or copper alloy plate formed into a generally rectangular plate shape with rounded corners that is smaller than the ceramic member 10. The second metal member 22 is provided with a long and narrow rectangular plate-shaped extension portion 222 that extends outward from one of its corners. The second metal member 22 is joined to the underside of the ceramic member 10 over the entire rectangular plate portion via the second solder layer 42 and the silver paste 12.

(effect)
According to the ceramic-metal bonded component having the above-mentioned configuration, the protuberance 210 is formed in a localized region of the first metal member 21. From the viewpoint of reducing the stress acting on the ceramic member 10 and the probability of fracture, an appropriate locally heated region (designated region), i.e., the non-bonded portion between the first metal member 21 and the ceramic member 10, can be easily visually identified by an operator.

The raised portion 210 formed in the specified region of the first metal member 21 forms a non-bonded portion (or a gap C between the first metal member 21 and the first solder layer 41). A non-bonded portion (or a gap C between the first metal member 21 and the first solder layer 41) between the first metal member 21 and the ceramic member 10 is formed in a local region. This reduces the stress acting on the ceramic member 10 when the first metal member 21 is locally heated in the specified region, thereby reducing the probability of fracture.

(Performance evaluation by simulation)
In order to evaluate the performance of the ceramic-metal bonded parts according to the present invention, simulation calculations were carried out. The configurations of the ceramic-metal bonded parts of the examples and comparative examples to be evaluated were defined as follows.

Example 1
In the ceramic-metal joint component of Example 1 shown in FIG. 4A, the first metal member 21 and the second metal member 22 are each made of a copper plate having a substantially square shape with rounded corners, with a side length of 30 mm and a thickness of 0.45 mm. The ceramic member 10 is made of a ZnO sintered body formed into a substantially square shape with rounded corners, with a side length of 34 mm and a thickness of 2 mm. The first metal member 21 and the second metal member 22 are joined to the ceramic member 10 via a first solder layer 41 and a second solder layer 42 having a thickness of 1 mm, respectively, so that the centers of the first metal member 21 and the second metal member 22 and the ceramic member 10 are aligned (see FIGS. 1 to 3).

A flat raised portion 210 is formed in a substantially square designated area with a side length of 6 mm, centered at a point 10 mm away from the center of one of the main surfaces along the vertical center line of one of the main surfaces of the first metal member 21. The designated area is defined so that each side of the square defining the designated area is parallel to each side of the square defining one of the main surfaces of the first metal member 21. In the first metal member 21, the raised portion 210 (or its flat upper end portion) is raised by 0.33 mm from the area other than the raised portion 210. In other words, the gap C between the first metal member 21 and the first solder layer 41 in the designated area where the raised portion 210 is formed is designed to be 0.33 mm. The gap C (see FIG. 3) between the first metal member 21 and the first solder layer 41 formed by the raised portion 210 is sealed by the edge of the surrounding first solder layer 41.

Example 2
In the ceramic-metal bonded component of Example 2 shown in Figure 4B, a raised portion 210 is formed in a substantially square designated region with a side length of 10 mm, centered at a point 10 mm away from the center of one of the main surfaces along the vertical center line of one of the main surfaces of the first metal member 21. In this case, one side (top side) of the designated region overlaps one side (top side) of the first metal member 21, and the gap C (see Figure 3) between the first metal member 21 and the first solder layer 41 formed by the raised portion 210 is opened to the external space via a part of the edge of the first metal member 21. In other respects, the configuration of the ceramic-metal bonded component of Example 2 is substantially the same as the configuration of the ceramic-metal bonded component of Example 1.

Example 3
In the ceramic-metal bonding component of Example 3 shown in FIG. 4C, a raised portion 210 is formed in a substantially rectangular designated area having a long side (upper side and lower side) length of 16 mm and a short side (right side and left side) length of 13 mm, centered at a point 8.5 mm away from the center of one of the main surfaces along the vertical center line of one of the main surfaces of the first metal member 21. The designated area is defined so that each side of the rectangle defining the designated area is parallel to each side of the square defining one of the main surfaces of the first metal member 21. In this case, the long side (upper side) of the designated area overlaps one side (upper side) of the first metal member 21, and the gap C (see FIG. 3) between the first metal member 21 and the first solder layer 41 formed by the raised portion 210 is opened to the external space through a part of the edge of the first metal member 21. In other respects, the configuration of the ceramic-metal bonding component of Example 3 is substantially the same as the configuration of the ceramic-metal bonding component of Example 1.

Example 4
In the ceramic-metal bonding component of Example 4 shown in FIG. 4D, a raised portion 210 is formed in a substantially rectangular designated area having a long side (upper side and lower side) length of 10 mm and a short side (right side and left side) length of 5 mm, centered at a point 12.5 mm away from the center of one of the main surfaces along the vertical center line of one of the main surfaces of the first metal member 21. In this case, the long side (upper side) of the designated area overlaps with one side (upper side) of the first metal member 21, and the gap C (see FIG. 3) between the first metal member 21 and the first solder layer 41 formed by the raised portion 210 is opened to the external space through a part of the edge of the first metal member 21. In other respects, the configuration of the ceramic-metal bonding component of Example 4 is substantially the same as the configuration of the ceramic-metal bonding component of Example 1.

Example 5
4E, a raised portion 210 is formed in a substantially square designated region with a side length of 10 mm and centered at a point 5 mm away from the center of one of the main surfaces along the vertical center line of one of the main surfaces of the first metal member 21. In other respects, the configuration of the ceramic-metal bonded component of Example 5 is substantially similar to the configuration of the ceramic-metal bonded component of Example 1.

Example 6
4F, a raised portion 210 is formed in a substantially square designated region with a side length of 10 mm and centered at a point 8 mm away from the center of one of the main surfaces along the vertical center line of one of the main surfaces of the first metal member 21. In other respects, the configuration of the ceramic-metal bonded component of Example 6 is substantially similar to the configuration of the ceramic-metal bonded component of Example 1.

(Example 7)
4G, in addition to the raised portion 210 similar to that of Example 1, a sub-raised portion 212 is formed in a further designated region of a substantially square shape with a side length of 8 mm and centered at a point 5 mm away from the center of one of the main surfaces along the vertical center line of one of the main surfaces of the first metal member 21. The raised portion 210 and the sub-raised portion 212 are arranged spaced apart from each other on one of the main surfaces of the first metal member 21. In other respects, the configuration of the ceramic-metal bonded component of Example 7 is substantially similar to the configuration of the ceramic-metal bonded component of Example 1.

(Example 8)
In the ceramic-metal bonding component of Example 8 shown in FIG. 5A, the first metal member 21 and the second metal member 22 are each composed of a substantially circular copper plate having a diameter of 27 mm and a thickness of 0.5 mm.

A flat raised portion 210 is formed in a generally sector-shaped designated area having an inner diameter of 13 mm, an outer diameter of 24 mm, and a central angle of 30°, based on the center of one of the main surfaces of the first metal member 21. The sector defining the designated area is arranged so as to have mirror symmetry based on the vertical center line of one of the main surfaces of the first metal member 21. In other respects, the configuration of the ceramic-metal bonded part of Example 8 is substantially the same as the configuration of the ceramic-metal bonded part of Example 1.

(Example 9)
In the ceramic-metal bonding component of Example 8 shown in FIG. 5B, the first metal member 21 and the second metal member 22 are each composed of a substantially circular copper plate having a diameter of 27 mm and a thickness of 0.5 mm.

A flat raised portion 210 is formed in a designated area of a roughly sector shape with a central angle of 60° based on the center of one of the main surfaces of the first metal member 21. In other respects, the configuration of the ceramic-metal bonded part of Example 9 is substantially the same as the configuration of the ceramic-metal bonded part of Example 8.

(Comparative Example 1)
In the ceramic-metal bonded component of Comparative Example 1, a substantially flat first metal member 21 having no protruding portion 210 is entirely bonded to a ceramic member 10 via a first solder layer 41. In other respects, the configuration of the ceramic-metal bonded component of Comparative Example 1 is substantially similar to the configuration of the ceramic-metal bonded component of Example 1.

(Comparative Example 2)
In the ceramic-metal bonded component of Comparative Example 2, a substantially flat first metal member 21 having no protruding portion 210 is entirely bonded to the ceramic member 10 via a first solder layer 41. In other respects, the configuration of the ceramic-metal bonded component of Comparative Example 2 is substantially similar to the configuration of the ceramic-metal bonded component of Example 8.

(Simulation calculation method)
The simulation was carried out using Calculix, an open FEM software that uses the basic parts of Abaqus. Calculix is used for thermal conduction analysis.

To define the elements in the mesh model for analysis, the 2 mm thick ceramic member 10 was defined as consisting of four layers, each of which was 0.5 mm thick, the first metal member 21 and the second metal member 22, each of which was 0.45 mm thick, each of which was made up of two layers, each of which was 0.225 mm thick, and the first solder layer 41 and the second solder layer 42, each of which was 1 mm thick, each of which was made up of three layers, each of which was 0.033 mm thick. In other words, it was defined that 14 layers of elements were stacked in the thickness direction of the ceramic-metal joint component. As a result, a mesh model with approximately 5,500 elements and approximately 7,000 nodes was defined.

Table 1 summarizes the material properties used in the simulation. The work-hardening characteristics of the first solder layer 41 and the second solder layer 42 are represented by characteristic curves in which the stress changes linearly from 40.3 MPa to 40.6 MPa as the plastic strain changes from 0 to 0.3.

In the black circle regions ● shown in Figures 4A to 4G and Figures 5A to 5B, the maximum thermal stress acting on the ceramic member 10 was calculated when the first metal member 21 was locally heated with a heat quantity of 32.15 W and the temperature of the extension portion 222 was heated until it reached 65°C. In the stress analysis, the reference temperature at which the stress is 0 was defined as 300 K (27°C).

The probability of the maximum thermal stress obtained from the simulation exceeding the Weibull distribution (probability distribution of the limit value for the external stress of the test piece) of the fracture strength obtained from a three-point bending test of a test piece (width 4 mm × thickness 2 mm × length 30 mm) much smaller than the actual product was evaluated as the fracture probability of the ceramic member 10.

(A) The probability distribution of the fracture strength obtained from the test piece depends on the volume of the test piece sample, and the size of the element to be determined is larger than that. Therefore, correction is required when calculating the fracture probability using the concept of "effective volume". (B) Even if the maximum value of thermal stress obtained from a simulation is small, if the proportion of elements with high thermal stress based on the calculation results of the thermal stress distribution increases, the probability of exceeding the stress strength of the entire element increases, and the fracture probability increases. Conversely, even if the maximum value of thermal stress distribution obtained from a computational simulation is large, if the proportion of elements with high thermal stress based on the calculation results of the thermal stress distribution is small, the probability of exceeding the stress strength of the entire element decreases, and the fracture probability decreases. The calculation results are summarized in Table 2.

From Table 2, the following points can be seen. The larger the area of the non-bonded portion (designated region) of the first metal member 21 and the ceramic member 10, the lower the maximum thermal stress acting on the ceramic member 10 tends to be. The location where the maximum thermal stress occurs varies from directly below the locally heated portion to directly below the end of the non-bonded portion or slightly inside. The location where the maximum thermal stress itself occurs is not limited to the ceramic member 10, but may be the first metal member 21. If the non-bonded portion (or the gap C between the first metal member 21 and the first solder layer 41) is open to the outside space, the thermal stress acting on the ceramic member 10 when the first metal member 21 is locally heated in the non-bonded portion tends to be lower. Example 6, in which the non-bonded portion or the gap C is not open to the outside, has a lower maximum thermal stress than Comparative Example 1, in which there is no non-bonded portion, but has a higher maximum thermal stress than Example 3, in which the non-bonded portion is open to the outside. Even if the maximum thermal stress is small, the probability of destruction may increase if the effective volume is large.

Other Embodiments of the Invention
As in Example 2, when the gap C (see FIG. 3) between the first metal member 21 and the first solder layer 41 formed by the raised portion 210 is open to the external space via a part of the edge of the first metal member 21, the open part may be blocked by a different material (e.g., synthetic resin). This can prevent a foreign object from entering the gap C.

In addition, because the sealing with the different material is performed locally, it is possible to easily allow the worker to visually identify the appropriate local heating area (designated area), i.e., the non-jointed portion between the first metal member 21 and the ceramic member 10, from the viewpoint of reducing the stress acting on the ceramic member 10 and the probability of fracture.

10: Ceramic member 21: First metal member (metal member)
22 Second metal member 41 First solder layer 42 Second solder layer 210 Protuberance 212 Sub-protuberance 222 Extension C Gap.

Claims (2)

A plate-shaped metal member is joined to the ceramic member in a joining region excluding a designated region, which is a part of one main surface facing the ceramic member,
the other main surface of the metal member opposite to the one main surface is locally raised in the designated region ,
the designated area includes a part of an outer edge of the one main surface of the metal member,
A gap between a part of an outer edge of the one main surface of the metal member and the ceramic member is sealed by a sealing member made of a different material and extending along the part of the outer edge of the one main surface of the metal member.
Ceramic-metal bonding parts. The ceramic-metal joint component according to claim 1,
A ceramic-metal joint component, wherein the one main surface of the metal member is locally recessed in the specified region.

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