WO2023149069A1

WO2023149069A1 - Clad plate and case using clad plate

Info

Publication number: WO2023149069A1
Application number: PCT/JP2022/044775
Authority: WO
Inventors: 紀智八木; 達也外木; 賢一加藤
Original assignee: 株式会社プロテリアル
Priority date: 2022-02-03
Filing date: 2022-12-05
Publication date: 2023-08-10
Also published as: JP2023113501A; JP7484949B2

Abstract

The present invention provides: a clad plate which is formed of a copper layer and a stainless steel layer, wherein the total content ratio of the constituent elements of the stainless steel layer within the copper layer after being held at 950°C for one minute has a specific distribution morphology, and the constituent elements of the stainless steel layer are not likely to be enriched in the surface of the copper layer even if exposed to high temperatures of 650°C to 950°C; and a case which uses this clad plate. The present invention provides: a clad plate which is obtained by bonding a copper layer that has a thickness of at least 10 µm to a stainless steel layer that has a thickness of at least 15 µm, with a diffusion bonding layer being interposed therebetween, wherein if the copper layer is separated and flattened after a heat treatment, in which the clad plate is held at 950°C for one minute, so as to obtain a copper piece, and the total content ratio of Ni, Cr, Fe and Mn is obtained by performing a GD-OES analysis from a randomly selected separation surface of the copper piece in the thickness direction, the total content ratio is 2% by mass or less at a depth of 5 µm from the separation surface of the copper piece; and a case which uses this clad plate.

Description

Clad plates and housings using clad plates

The present invention relates to a clad plate and a housing using the clad plate, for example, a clad plate suitable for forming a flat vapor chamber (housing) and a housing using the clad plate.

In recent years, electronic devices (for example, home computers, mobile computers, tablet computers, etc.) and communication devices (for example, tablet terminals, cell phones, etc.) equipped with semiconductor devices have become smaller, thinner, and lighter, and have advanced functions. Improvements and performance improvements are steadily progressing. For example, a CPU, which is a central processing unit in electronic equipment and communication equipment, is generating more heat due to rapid progress in higher operating speeds and higher densities. An excessive temperature rise inside the device due to this heat generation causes malfunction of the CPU, thermal runaway, and the like. Therefore, there is an urgent need to improve the heat absorption efficiency from a semiconductor device such as a CPU, which is a heat source, and to improve the heat exhaust efficiency to the outside of the equipment.

A vapor chamber has been proposed as an effective heat dissipation means for improving the heat absorption efficiency and exhaust heat efficiency of these electronic devices and communication devices. For example, the vapor chambers disclosed in Patent Literatures 1 and 2 are flat plate-like housings formed by joining an upper plate and a lower plate by welding, diffusion bonding, or the like. A working fluid such as water or methanol is sealed inside the flat plate-shaped housing under reduced pressure. The upper plate and the lower plate are clad plates composed of a copper layer such as C1020 with good thermal conductivity and a stainless steel layer such as SUS316L having suitable mechanical strength, and the copper layers face each other. . Therefore, a heat source such as a semiconductor device is placed on the surface of the stainless steel layer outside the housing, and the working fluid inside the housing is in contact with the surface of the copper layer, which has good thermal conductivity.

In a vapor chamber using such a clad plate, heat is absorbed from the heat source to the stainless steel layer, transferred from the stainless steel layer to the copper layer, and further from the copper layer to the working fluid such as water. The heat transferred to the working fluid such as water evaporates, the steam condenses in contact with the heat exhaust part, and the heat is exhausted from the heat exhaust part to the outside of the housing. In this way, the flat vapor chamber utilizes the cycle of evaporation and condensation of water, etc., efficiently absorbs heat from the heat source, and efficiently discharges it to the outside. It is highly expected as a heat dissipation means for improving thermal properties (heat absorption efficiency, heat exhaust efficiency, etc.).

JP 2016-188734 A JP 2021-143829 A

In the vapor chamber disclosed in Patent Document 1, a clad plate made of a copper layer and a stainless steel layer is used as an upper plate and a lower plate that constitute a flat plate-like housing. The upper plate and the lower plate of the housing are joined by joining means involving heating, such as welding and thermal diffusion joining. In this case, it is considered possible to perform brazing using phosphor-copper brazing, silver brazing, or the like. As in this vapor chamber, when joining means involving heating is used for a clad plate composed of a copper layer and a stainless steel layer, the clad plate is exposed to high temperatures.

For example, with welding methods such as laser welding, at least the copper layer of the clad plate, which has a lower melting point than stainless steel, melts. Therefore, considering the melting point of copper (1080° C. or higher), many parts of the clad plate may reach a high temperature range exceeding 900° C. due to heat conduction. Moreover, in thermal diffusion bonding, the temperature is maintained at a temperature at which a metal diffusion layer is formed between copper and stainless steel, for example, a temperature of 650° C. or more and 950° C. or less. Therefore, the entire clad plate is placed in a high temperature environment of 650° C. or higher. Further, in general brazing of stainless steel and copper, the brazing material is held at a melting temperature, for example, a temperature of 650° C. or higher and 850° C. or lower. Therefore, the entire clad plate is placed in a high temperature environment of 650° C. or higher.

When a clad plate composed of a copper layer and a stainless steel layer is exposed to the above-described high temperature, the constituent elements (eg, Si, Cr, Mn, Fe, Ni, Mo, etc.) of the stainless steel layer are bonded to the copper layer. It diffuses further into the copper layer from the surface (bonding layer). As a result, depending on the thickness of the copper layer, these diffusing elements may reach the surface of the copper layer opposite the stainless steel layer and concentrate at and near the surface of the copper layer. For example, in the case of the above vapor chamber, if the constituent elements of the stainless steel layer are concentrated on the surface of the copper layer, they react with the working fluid such as water in contact with the surface of the copper layer, and the reaction products evaporate and condense. may inhibit the cycle of As a result, the heat transfer characteristics (heat absorption efficiency, heat exhaust efficiency, etc.) of the vapor chamber are degraded, and the housing may be deformed.

An object of the present invention is to solve the above-mentioned problems by providing a clad plate comprising a copper layer and a stainless steel layer, wherein the constituent elements of the stainless steel layer are dissolved in the copper layer after being held at 950° C. for 1 minute. A clad plate in which the total content ratio exhibits a specific distribution form, and the constituent elements of the stainless steel layer are difficult to concentrate on the surface of the copper layer even when exposed to a high temperature of, for example, 650° C. or higher and 950° C. or lower, and the clad plate is provided. It is to provide a housing used.

The inventor made a prototype of a clad plate consisting of a copper layer (for example C1020) and a stainless steel layer (for example SUS316L), subjected to heat treatment at 950°C for 1 minute, and peeled off the copper layer from the clad material after the heat treatment. The stripped copper strip was flattened, and GD-OES analysis was performed in the thickness direction from a randomly selected stripped surface of the stripped copper strip after straightening. As a result, if the total content ratio of Cr, Mn, Fe and Ni in the inside of the copper piece after straightening (that is, the copper layer of the clad plate) has a specific distribution form, the copper piece after straightening The inventors have found that the constituent elements of the stainless steel layer are difficult to concentrate on the surface opposite to the peeled surface (that is, the surface of the copper layer of the clad plate), and have arrived at the present invention.

That is, the clad plate according to the present invention is a clad formed by bonding a copper layer having a thickness of at least 10 μm to a stainless steel layer having a thickness of at least 15 μm through a diffusion bonding layer in the thickness direction. A plate, the clad plate is heat-treated at 950° C. for 1 minute, the copper layer is peeled off from the clad plate after the heat treatment to form a copper piece, the copper piece is flattened, and the straightening is performed. GD-OES analysis was performed in the thickness direction from the peeled surface of the copper piece selected at random after that, and the total content ratio of Cr, Mn, Fe and Ni was determined. is 2% by mass or less.

In the clad plate according to the present invention, the copper layer has a thickness of at least 15 μm, the total content ratio at a position of 5 μm from the peeled surface of the copper piece is 2% by mass or less, and the The total content ratio may be 0.5% by mass or less.

In the clad plate according to the present invention, the copper layer has a thickness of at least 20 μm, the total content ratio at a position of 5 μm from the peeled surface of the copper piece is 2% by mass or less, and the The total content ratio may be 0.5% by mass or less, and the total content ratio at a position of 15 μm may be 0.2% by mass or less.

In the clad plate according to the present invention, the copper layer preferably contains 99.0% by mass or more of Cu.

In the clad plate according to the present invention, the stainless steel layer is preferably an austenitic stainless steel layer containing 15% by mass or less of Ni, 20% by mass or less of Cr, and 2% by mass or less of Mn.

A housing can be configured using the clad plate according to the present invention. That is, a housing using a clad plate according to the present invention has an upper plate made of any one of the clad plates described above and a lower plate made of any one of the clad plates described above, and the upper plate is made of copper A layer and the copper layer of the lower plate are diffusion-bonded in the thickness direction to form a defined space. A housing using a clad plate according to the present invention is suitable for a flat vapor chamber (housing) in which a working fluid such as water is sealed in the space inside the housing.

According to the present invention, a clad plate comprising a stainless steel layer and a copper layer, wherein the total content ratio of the constituent elements of the stainless steel layer inside the copper layer after being held at 950 ° C. for 1 minute has a specific distribution form and, for example, even when exposed to a high temperature of 650° C. or more and 850° C. or less, a clad plate in which constituent elements of a stainless steel layer are difficult to concentrate on the surface of a copper layer, and a housing using the clad plate. can be done.

It is a figure which shows typically the structural example of the clad board which concerns on this invention. It is a figure which shows an example of the enlarged image (photograph) of the cut surface when the clad plate which concerns on this invention is cut|disconnected in the thickness direction. FIG. 4 is a diagram schematically showing a structural example of a housing using the clad plate according to the present invention; FIG. 4 is a diagram schematically showing a structural example of a housing using the clad plate according to the present invention;

The clad plate according to the present invention will be described with reference to the drawings as appropriate, giving configuration examples of the clad plate and a housing using the clad plate. It should be noted that the clad plate and the housing using the clad plate according to the present invention are not limited to the configuration examples illustrated here, but are indicated by the scope of the claims, and the meaning and scope equivalent to the scope of the claims. should be construed to include all changes within. In addition, in the descriptions of the specification and the drawings, for the sake of simplicity, the clad plate and the case using the clad plate may be commonly referred to by common terms and reference numerals. Further, the total content ratio (numerical value) is expressed in % by mass unless otherwise specified.

Fig. 1 shows a configuration example of the clad plate according to the present invention. A clad plate 100 shown in FIG. 1 is formed by bonding a copper layer 101 to a stainless steel layer 102 via a diffusion bonding layer 103 in the thickness direction (Z direction).

The copper layer 101 of the clad plate 100 has a thickness of at least 10 μm. The thickness of the copper layer 101 may be a value calculated from the average thickness of the copper plate for forming the copper layer 101 and the workability during clad rolling described later, or may be obtained by peeling the copper layer 101. It may be an average value obtained by actually measuring the copper piece 101 (including the peeled surface 101a). The copper piece 101 and the peeling surface 101a of the copper piece 101 will be described later. Moreover, the copper layer 101 preferably contains 99.0% by mass or more of Cu. For example, when the clad plate 100 is used to form a vapor chamber (housing), the thickness of the copper layer 101, which is superior in thermal conductivity to that of the stainless steel layer 102, is 10 μm or more, so that appropriate heat transfer characteristics can be achieved. can be secured. In addition, the high-purity copper layer 101 containing 99.0% by mass or more of Cu can ensure higher heat transfer characteristics. Such a copper layer 101 can be composed of a copper plate made of copper or a copper alloy. Such a copper layer 101 contains, for example, 99.0% by mass or more of Cu, and contains less than 1% by mass of elements such as Fe other than Cu, such as C1020, C1100, C1201, C1220, C1441, C1510, C1921. and C2051. Such a copper layer 101 can be composed of, for example, a copper plate made of a copper alloy having components specified in JIS-H3100:2018, such as C5191 containing about 5% to 7% by mass of Sn.

The stainless steel layer 102 of the clad plate 100 has a thickness of at least 15 μm. The thickness of the stainless steel layer 102 is a value obtained from the average thickness of the stainless steel plate for forming the stainless steel layer 102 and the workability (%) during clad rolling, which will be described later. Also, the stainless steel layer 102 is preferably an austenitic stainless steel layer containing 15% by mass or less of Ni, 20% by mass or less of Cr, and 2% by mass or less of Mn. For example, when the clad plate 100 is used to form a vapor chamber (housing), the stainless steel layer 102, which has a mechanical strength superior to that of the copper layer 101, has a thickness of 15 μm or more, so that the above deformation can be prevented. The mechanical strength to be obtained can be secured. In addition, since it is an austenitic stainless steel layer having excellent corrosion resistance, etc., containing 15% by mass or less of Ni, 20% by mass or less of Cr, and 2% by mass or less of Mn, it has a mechanical strength that can withstand the deformation described above. Corrosion resistance and the like can be secured. Such a stainless steel layer 102 can be composed of, for example, a stainless steel plate such as SUS316L, SUS304, and SUS301 having the composition specified in JIS-G4305:2015. Further, for example, if the stainless steel layer 102 is made of SUS316L, it is possible to obtain a non-magnetic vapor chamber (housing).

The diffusion bonding layer 103 of the clad plate 100 is composed of diffusion products including Cu contained in the copper layer 101 and Fe contained in the stainless steel layer 102 . The diffusion bonding layer 103 is observed in a high resolution backscattered electron image (BSE) imaging using a YAG laser, for example, of a cut surface of the clad plate 100 cut in the thickness direction (Z direction). be able to. FIG. 2 shows an example of a YAG-BSE image of the cut surface of the clad plate 100. As shown in FIG. In the YAG-BES image shown in FIG. 2, a thin layered region of fine crystal grains (1 μm or less) is observed on the side of the copper layer in contact with the stainless steel layer. This thin layered region is the diffusion bonding layer 103 resulting from the constituents of the stainless steel that have diffused from the stainless steel layer 102 toward the copper layer 101 due to heating. Such a diffusion bonding layer 103 is formed by rolling (clad rolling) a copper plate for forming the copper layer 101 and a stainless steel plate for forming the stainless steel layer 102 in the thickness direction (Z direction). Furthermore, by performing heat diffusion treatment (diffusion annealing) under appropriate temperature conditions (for example, the holding temperature is 650° C. or higher and 950° C. or lower and the holding time is 0.5 minutes or longer and 3 minutes or shorter), the stainless steel is It is formed by diffusion of constituent elements of the layer 102 toward the copper layer 101 side. When diffusion annealing is performed under appropriate temperature conditions, the thickness of the diffusion bonding layer 103, which appears to be a layered form of the clad plate 100, is sufficiently smaller than the thickness of the copper layer 101 and the thickness of the stainless steel layer 102. , for example, from 0.1 μm to 1 μm. The thickness of the diffusion bonding layer 103 is an average value obtained from thicknesses (length in the Z direction) measured at a plurality of randomly selected locations in a cross section of the clad plate 100 cut in the thickness direction (Z direction). is.

As described above, the clad plate 100 according to the present invention has the copper layer 101 having a thickness of at least 10 μm bonded to the stainless steel layer 102 via the moderately thick diffusion bonding layer 103 . Since the clad plate 100 in this state is bonded through the diffusion bonding layer 103 having an appropriate thickness, the components of the stainless steel layer 102 are not excessively diffused inside the copper layer 101 . Since this point has been confirmed, Table 2 will be shown and will be described later. When the clad plate 100 in this state is exposed to high temperature, diffusion of the components of the stainless steel layer 102 inside the copper layer 101 of the clad plate 100 after being exposed to the high temperature certainly progresses. However, in the clad plate 100 according to the present invention, the interface between the diffusion bonding layer 103 and the copper layer 101 inside the copper layer 101 having a thickness of at least 10 μm after the heat treatment at 950° C. for 1 minute The total content ratio of Cr, Mn, Fe and Ni is 2% by mass or less at a position 5 μm from the corresponding portion (exfoliation surface 101a) toward the Z1 side in the thickness direction (Z direction). Therefore, on the surface of the copper layer 101 having a thickness of at least 10 μm (the surface opposite to the peeled surface 101a) of the clad plate 100, the total content ratio is surely smaller than 2% by mass, for example 0.5% by mass. It becomes below.

The clad plate 100 exhibiting the characteristics for heat treatment as described above can be exposed to a high temperature of, for example, 650° C. or higher and 850° C. or lower. The total content ratio is small. Therefore, even if it is used, for example, in a vapor chamber (casing), reaction with a working fluid such as water in contact with the surface of the copper layer 101 can be suppressed.

The clad plate 100 according to the present invention corresponds to the interface between the diffusion bonding layer 103 and the copper layer 101 inside the copper layer 101 having a thickness of at least 15 μm after performing a heat treatment at 950° C. for 1 minute. The total content ratio is 2% by mass or less at a position 5 μm from the part (peeled surface 101a) toward the Z1 side in the thickness direction (Z direction), and the total content ratio is 0.5% by mass at a position 10 μm. It is below. Therefore, on the surface of the clad plate 100 of the copper layer 101 having a thickness of at least 15 μm (the surface opposite to the peeled surface 101a), the total content ratio is definitely smaller than 0.5% by mass, for example, 0.2%. % or less. Clad plate 100 exhibiting such characteristics for heat treatment has a sufficiently low total content of stainless steel constituents on the surface of copper layer 101 even when exposed to a high temperature of, for example, 650° C. or higher and 850° C. or lower. Therefore, even if it is used, for example, in a vapor chamber (casing), the reaction of working fluid such as water in contact with the surface of the copper layer 101 can be sufficiently suppressed.

The clad plate 100 according to the present invention corresponds to the interface between the diffusion bonding layer 103 and the copper layer 101 inside the copper layer 101 having a thickness of at least 20 μm after performing a heat treatment at 950° C. for 1 minute. The total content ratio is 2% by mass or less at a position 5 μm from the part (peeled surface 101a) toward the Z1 side in the thickness direction (Z direction), and the total content ratio is 0.5% by mass at a position 10 μm. or less, and the total content ratio is 0.2% by mass or less at a position of 15 μm. Therefore, on the surface of the copper layer 101 having a thickness of at least 20 μm of the clad plate 100 (the surface opposite to the peeled surface 101a), the above total content ratio is surely smaller than 0.2% by mass. Even if clad plate 100 that exhibits such heat treatment properties is exposed to a high temperature of, for example, 650° C. or more and 850° C. or less, the total content ratio of the stainless steel constituents on the surface of copper layer 101 is surely small. Therefore, even if it is used, for example, in a vapor chamber (casing), the reaction of working fluid such as water in contact with the surface of the copper layer 101 can be reliably suppressed.

Here, in the present invention, the portion corresponding to the interface between the diffusion bonding layer 103 and the copper layer 101 of the clad plate 100 is referred to as a peeling surface 101a. This peeled surface 101a is the same as the peeled surface 101a of the copper piece 101 which is the specimen of the GD-OES analysis described later. In addition, the total content ratio, that is, the total content ratio of Cr, Mn, Fe and Ni is obtained by depth profile analysis of GD-OES analysis (Glow discharge optical emission spectrometry).

The specimen for GD-OES analysis is a copper piece (hereinafter referred to as copper piece 101) by peeling off the copper layer 101 from the clad plate 100 after heat treatment at 950 ° C. for 1 minute, and this copper piece 101 is corrected flat. The subject is heat-treated at 950° C. for 1 minute. This holding temperature of 950° C. imitates the maximum temperature (950° C.) of the thermal diffusion bonding described above, which is presumed to be the maximum temperature to which the entire clad plate 100 is exposed. GD-OES analysis is performed in the thickness direction (Z1 side in the Z direction) from the randomly selected exfoliated surface 101a of the copper piece 101 after this straightening. Further, diffusion of the constituent elements of the stainless steel layer 102 into the copper layer 101 due to diffusion annealing progresses uniformly, and the compositional fluctuation of the total content ratio along the thickness direction (Z direction) inside the copper layer 101 is continuous. target. Therefore, the quantification of the analysis depth (μm) and the total content ratio (% by mass) in the GD-OES analysis is performed by analyzing a copper material whose composition is similar to that of the copper piece 101 and a stainless steel material whose composition is similar to that of the stainless steel layer 102. A calibration curve shall be created by using the calibration curve.

The peeled surface 101a of the copper piece 101, which is the specimen of the GD-OES analysis, is formed by breaking and dividing the diffusion bonding layer 103 due to the peeling of the stainless steel layer 102. Therefore, on the surface of the copper piece 101 on the side (Z2 side) where the diffusion bonding layer 103 is broken and divided, the diffusion products forming the diffusion bonding layer 103 become residues, and the thickness of the diffusion bonding layer 103 increases. It exists in the form of a thin film with a thickness smaller than the height. This thin-film-like residue is also present on the surface (peeled surface 101a) after the copper piece 101 has been flattened, but its thickness is sufficiently small. At present, it is not easy to accurately measure the thickness of the thin film-like residue present on the peeled surface 101a of the copper piece 101 after flattening. Considering the destruction and division at the time of peeling and the compression at the time of flattening, the thickness of the thin-film residue present on the peeled surface 101a of the copper piece 101 after flattening varies greatly, but the thickness of the diffusion bonding layer 103 is large. It is considered to be sufficiently smaller than the thickness (for example, 0.1 μm or more and 1 μm or less as described above). Therefore, the thickness of the film-like residue present on the peeled surface 101a of the copper piece 101 after flattening is sufficiently smaller than the thickness of the copper layer 101 (copper piece 101), which is 10 μm or more.

In view of the above, in the present invention, the reference position of the analysis depth in GD-OES analysis (depth profile analysis) is the portion corresponding to the interface between the diffusion bonding layer 103 and the copper layer 101 of the clad plate 100, that is, A peeling surface 101a of a copper piece 101 to be tested is used. Then, in the depth profile of the GD-OES analysis, the quantitative value of the total content ratio at a depth of less than 0.5 μm from the reference position (peeled surface 101a) is taken into consideration of the risk including the influence of the residue, from the evaluation target. exclude. In addition, even if the thickness of the copper layer 101 is the measured value (average thickness) including the exfoliated surface 101a of the copper piece 101, there is no substantial problem.

As described above, the present invention deals with the total content ratio of Cr, Mn, Fe and Ni inside the copper layer 101 of the clad plate 100. Among the constituent elements of general-purpose stainless steel, Si, Cr, Mn, Fe, Ni, Mo, etc. are known to thermally diffuse inside the copper material (pure copper). In general, the diffusion of elements progresses from the side of high concentration (content ratio) to the side of low concentration, and the diffusion speed (moving distance per unit time) is generally proportional to the concentration gradient. Therefore, it is considered that the elements with a higher concentration in the stainless steel layer 102 of the clad plate 100 move (diffuse) more toward the inside of the copper layer 101 .

When the stainless steel layer 102 of the clad plate 100 is made of, for example, SUS301, SUS304, or SUS316L, the concentrations (content ratios) of Cr, Fe, and Ni are relatively high, and the concentrations (content ratios) of Mn and Si are relatively high. low. For example, when the upper limit (mass%) described in JIS-G4305: 2015 is shown, SUS301 has Si of 1%, Cr of 18%, Mn of 2%, Ni of 8%, and Mo is not described. . Similarly, SUS304 contains 1% Si, 20% Cr, 2% Mn, 10.5% Ni, and no regulation for Mo. Similarly, SUS316L contains 1% Si, 18% Cr, 2% Mn, 14% Ni, and 3% Mo. Therefore, the migration distance (diffusion distance) from the stainless steel layer 102 to the copper layer 101 is considered to be large for the base Fe and the higher concentrations of Cr and Ni, and smaller for the lower concentrations of Mo, Mn and Si. .

Therefore, a heat treatment was performed at 950° C. for 1 minute, and the diffusion distance to the copper layer 101 (copper piece 101) was confirmed by the GD-OES analysis. Although details will be described later, it was found that the Si and Mo content ratios were sufficiently smaller than the Cr, Mn, Fe and Ni content ratios at a position 5 μm from the peeled surface 101a of the copper piece 1010 . Moreover, it was found that each content ratio of Si and Mo was 1/20 or less of the content ratio of Mn, which was the smallest among Cr, Mn, Fe and Ni. Taking this result into consideration, the present invention evaluates the total content ratio of Cr, Mn, Fe and Ni according to the GD-OES analysis. This point will be described later in detail.

As described above, the clad plate 100 according to the present invention has a stainless steel layer 102 having a thickness of at least 15 μm, a copper layer 101 having a thickness of at least 10 μm, and a diffusion bonding layer 103 interposed therebetween. It is joined in the direction (Z direction). The clad plate 100 can be manufactured by a dissimilar metal rolling joining method in which a copper plate is laminated on a stainless steel plate in the thickness direction and then rolled. In the present invention, rolling for joining dissimilar metals is called clad rolling. The method of rolling and joining dissimilar metals applicable to the present invention includes, in addition to the clad rolling process, softening annealing and intermediate rolling before clad rolling, diffusion annealing and intermediate rolling after clad rolling, thickness, width, surface properties and Processes such as finish rolling to obtain various characteristics, skin pass rolling, softening annealing to improve press workability, strain relief annealing to suppress warpage by etching, surface treatment, and stripping. including. In the method of rolling and joining dissimilar metals applicable to the present invention, the several steps described above are selectively combined before and after the clad rolling step as required.

When the clad plate 100 is manufactured by the method of rolling and joining dissimilar metals as described above, the conditions in each step are intentionally set or adjusted with special consideration given to several key points. One of the main points is to make the hardness difference between the stainless steel plate for forming the stainless steel layer 102 and the hardness of the copper plate for forming the copper layer 101 as small as possible before the clad rolling process. . One of the main points is to appropriately set the degree of rolling processing of the copper sheet during clad rolling, and to make the crystal grain size of the copper layer 101 after clad rolling as small as possible. One of the main points is to appropriately set the holding conditions during diffusion annealing and form the diffusion bonding layer 103 with an appropriate thickness (for example, 0.1 μm or more and 1 μm or less as described above). Moreover, when further rolling the clad plate after diffusion annealing, it is preferable to reduce the degree of rolling work of the clad plate during further rolling as much as possible. The rolling workability is the ratio of the plate thickness after rolling to the plate thickness before rolling. In addition, the degree of rolling work of the clad plate 100 is the thickness of the copper layer 101 and the thickness of the stainless steel layer 102 that constitute the clad plate 100 with respect to the sum of the thickness of the stainless steel plate and the thickness of the copper plate that constitute the clad plate 100. is the ratio of the sum of

Next, FIG. 3 and FIG. 4 show configuration examples of a housing using the above clad plate according to the present invention.

A housing 1A shown in FIG. 3 is a main part of an example of a flat plate-shaped vapor chamber. The housing 1A has an upper plate 10 and a lower plate 20. As shown in FIG. A top plate 10 has a copper layer 11 and a stainless steel layer 12 . Lower plate 20 has copper layer 21 and stainless steel layer 22 . The upper plate 10 and the lower plate 20 are arranged facing each other in the thickness direction (Z direction). The copper layer 11 of the upper plate 10 and the copper layer 21 of the lower plate 20 are joined by joining means involving heating, such as thermal diffusion joining. The joint structure of the upper plate 10 and the lower plate 20 defines a space 40 surrounded by the copper layer 11 and the copper layer 21 inside the housing 1A.

A working fluid such as water is injected into the space 40 inside the housing 1A. A space 40 inside the housing 1A is vacuum-sealed so that a working fluid such as water does not leak to the outside. A plurality of recesses 41 are formed in the space 40 inside the housing 1A by processing means such as etching. When configuring such a plurality of recesses, the structure is not limited to the configuration of the housing 1A having a plurality of recesses 41 on the surface of the copper layer 21 of the lower plate 20 . In the case of the housing 1A, such a plurality of recesses can be formed, for example, on the surface of the copper layer 11 of the upper plate 10, or can be formed on both the copper layer 11 of the upper plate 10 and the copper layer 21 of the lower plate 20. It can also be formed on the surface. Such multiple recesses 41 provide a larger surface area surrounding the space 40 . Therefore, the space 40 can be defined in which the copper layer 11 and the copper layer 21 with good thermal conductivity have a larger surface area. As a result, the contact area of the working fluid such as water (the surface area of the copper layer 11 and the copper layer 21) increases in the space 40 inside the housing 1A, so that the efficiency of heat absorption and heat dissipation of the vapor chamber can be improved. can.

The upper plate 10 constituting the housing 1A is formed using the clad plate according to the present invention. The upper plate 10 is formed by bonding a copper layer 12 to a stainless steel layer 12 via a diffusion bonding layer in the thickness direction (Z direction). The upper plate 10 may have a thickness of 25 μm or more and 500 μm or less, for example. The copper layer 11 of the upper plate 10 has a thickness of at least 10 μm, and may be, for example, between 10 μm and 400 μm. If the thickness of the copper layer 11 of the upper plate 11 is too small (less than 10 μm), the heat transfer characteristics of the housing 1A will be insufficient. becomes heavy. The stainless steel layer 12 of the top plate 10 has a thickness of at least 15 μm, and may be, for example, greater than or equal to 15 μm and less than or equal to 100 μm. If the thickness of the stainless steel layer 12 of the upper plate 11 is too small (less than 15 μm), the mechanical strength of the housing 1A will be insufficient, and if it is too large (for example, more than 100 μm), the heat source Insufficient heat absorption from

When the upper plate 10 having the above configuration is exposed to a high temperature of, for example, 650° C. to 850° C., the GD-OES analysis described above is performed at a position 5 μm from the boundary with the stainless steel layer 12 inside the copper layer 11. The total content ratio of Cr, Mn, Fe and Ni obtained in 1. above is 2% by mass or less. Therefore, on the surface of the copper layer 11 having a thickness of at least 10 μm of the upper plate 10, the total content ratio is certainly less than 2% by mass. In addition, in the portion where the thickness of the copper layer 11 is 15 μm or more, the total content ratio is 2% by mass or less at a position 5 μm from the boundary with the stainless steel layer 12, and at a position 10 μm from the boundary with the stainless steel layer 12. The above total content ratio becomes 0.5% by mass or less. Therefore, on the surface of the copper layer 11 having a thickness of at least 15 μm of the upper plate 10, the above total content ratio is surely smaller than 0.5 mass %. In addition, in the portion where the thickness of the copper layer 11 is 20 μm or more, the total content ratio is 2% by mass or less at a position 5 μm from the boundary with the stainless steel layer 12, and at a position 10 μm from the boundary with the stainless steel layer 12. , the total content ratio is 0.5% by mass or less, and the total content ratio is 0.2% by mass or less at a position 15 μm from the boundary with the stainless steel layer 12 . Therefore, on the surface of the copper layer 11 having a thickness of at least 20 μm of the upper plate 10, the total content ratio is surely smaller than 0.2% by mass. Therefore, the upper plate 10 having the structure described above can achieve the same effect as the clad plate according to the present invention. In addition, the boundary with the stainless steel layer 12 here intends the exfoliation surface 101a of the copper piece 100 described above.

A lower plate 20 that constitutes the housing 1A is formed using the clad plate according to the present invention. The lower plate 20 is formed by bonding a copper layer 22 to a stainless steel layer 22 via a diffusion bonding layer in the thickness direction (Z direction). The lower plate 20 may have a thickness of, for example, 25 μm or more and 500 μm or less. The copper layer 21 of the lower plate 20 has a thickness of at least 10 μm, and may be, for example, 10 μm or more and 400 μm or less. If the thickness of the copper layer 21 of the lower plate 20 is too small (less than 10 μm), the heat transfer characteristics of the housing 1A will be insufficient. becomes heavy. The stainless steel layer 22 of the lower plate 20 has a thickness of at least 15 μm, and may be, for example, greater than or equal to 15 μm and less than or equal to 100 μm. If the thickness of the stainless steel layer 22 of the lower plate 20 is too small (less than 15 μm), the mechanical strength of the housing 1A becomes insufficient, and if it is too large (for example, over 100 μm), the heat source Insufficient heat absorption from

Unlike the copper layer 11 of the upper plate 10, the copper layer 21 of the lower plate 20 constituting the housing 1A is formed with a plurality of recesses 41 by processing means such as etching. The copper layer 21 has a thickness of at least 10 μm before forming the recesses 41 . The portion indicated by the thickness Tc is substantially the same as the thickness of the copper layer 21 before forming the plurality of recesses 41, and is, for example, 20 μm or more and 400 μm or less. In the plurality of recesses 41 of the copper layer 21, for example, the portion indicated by the thickness Ta is thinner than the portion indicated by the thickness Tb and the portion indicated by the thickness Tc. The portion indicated by the thickness Ta is the portion where the thickness of the copper layer 21 is the smallest. The thickness Ta of the copper layer 21 has a thickness of at least 10 μm. The portion of copper layer 21 indicated by thickness Tb has a thickness of at least greater than 10 μm, for example 15 μm or more.

When the lower plate 20 having the above structure is exposed to a high temperature of, for example, 650° C. to 850° C., the copper layer 21 inside the portion having a thickness of at least 10 μm (for example, the portion indicated by the thickness Ta) , the total content ratio of Cr, Mn, Fe and Ni determined by the GD-OES analysis is 2% by mass or less at a position 5 μm from the boundary with the stainless steel layer 22 . Therefore, on the surface of the copper layer 21 having a thickness of at least 10 μm of the lower plate 20, the total content ratio is certainly less than 2% by mass. In addition, the copper layer 21 has a total content of 2% by mass at a position 5 μm from the boundary with the stainless steel layer 22 in a portion having a thickness of at least 15 μm (for example, a portion indicated by the thickness Tb). The total content ratio becomes 0.5% by mass or less at the position of 10 μm. Therefore, on the surface of the copper layer 21 having a thickness of at least 15 μm of the lower plate 20, the total content ratio is certainly smaller than 0.5% by mass. In addition, the copper layer 21 has a total content of 2% by mass at a position 5 μm from the boundary with the stainless steel layer 22 inside a portion having a thickness of at least 20 μm (for example, a portion indicated by thickness Tc). At the position of 10 μm, the total content ratio is 0.5% by mass or less, and at the position of 15 μm, the total content ratio is 0.2% by mass or less. Therefore, on the surface of the copper layer 21 having a thickness of at least 20 μm of the lower plate 20, the total content ratio is surely smaller than 0.2% by mass. Therefore, the lower plate 20 having the structure described above can achieve the same effect as the clad plate according to the present invention. In addition, the boundary with the stainless steel layer 22 here intends the exfoliation surface 101a of the copper piece 100 described above.

A housing 1B shown in FIG. 4 is also an essential part of an example of a flat plate-shaped vapor chamber. The housing 1B has an upper plate 10 having the same configuration as that of the housing 1A and a lower plate 30 having a different configuration from that of the housing 1A. A top plate 10 has a copper layer 11 and a stainless steel layer 12 . Lower plate 30 has a copper layer 31 and a stainless steel layer 32 . The upper plate 10 and the lower plate 30 are arranged facing each other in the thickness direction (Z direction). The copper layer 11 of the upper plate 10 and the copper layer 31 of the lower plate 30 are joined by joining means involving heating, such as thermal diffusion joining. The joint structure of the upper plate 10 and the lower plate 30 defines a space 40 surrounded by the copper layer 11 and the copper layer 31 inside the housing 1B.

A working fluid such as water is injected into the space 40 inside the housing 1B. A space 40 inside the housing 1B is vacuum-sealed so that a working fluid such as water does not leak to the outside. A plurality of recesses 41 are formed in the space 40 inside the housing 1B by working means such as press molding. When configuring such a plurality of recesses, the structure is not limited to the configuration of the housing 1B having the plurality of recesses 41 on the surface of the copper layer 31 of the lower plate 30 . In the case of the housing 1B, such a plurality of recesses can be formed, for example, on the surface of the copper layer 11 of the upper plate 10, or can be formed on both the copper layer 11 of the upper plate 10 and the copper layer 31 of the lower plate 30. It can also be formed on the surface. Such multiple recesses 41 provide a larger surface area surrounding the space 40 . Therefore, the space 40 can be defined in which the copper layer 11 and the copper layer 31 with good thermal conductivity have a larger surface area. As a result, the contact area (the surface area of the copper layer 11 and the copper layer 31) of the working fluid such as water increases in the space 40 inside the housing 1B, so that the efficiency of heat absorption and exhaustion of the vapor chamber can be improved. can.

The upper plate 10 that constitutes the housing 1B is formed using the clad plate according to the present invention. The upper plate 10 of the housing 1B can also produce the same effect as the clad plate according to the present invention. The description of the upper plate 10, the copper layer 11 and the stainless steel layer 12 of the housing 1B is omitted here since the above-described housing 1A is referred to.

A lower plate 30 that constitutes the housing 1B is formed using the clad plate according to the present invention. The lower plate 30 is formed by bonding a copper layer 32 to a stainless steel layer 32 via a diffusion bonding layer in the thickness direction (Z direction). The lower plate 30 may have a thickness of, for example, 25 μm or more and 500 μm or less. The copper layer 31 of the lower plate 30 has a thickness of at least 10 μm, and may be, for example, 10 μm or more and 400 μm or less. If the thickness of the copper layer 31 of the lower plate 30 is too small (less than 10 μm), the heat transfer characteristics of the housing 1B are insufficient. becomes heavy. The stainless steel layer 32 of the lower plate 30 has a thickness of at least 15 μm, and may be, for example, greater than or equal to 15 μm and less than or equal to 100 μm. If the thickness of the stainless steel layer 32 of the lower plate 30 is too small (less than 15 μm), the mechanical strength of the housing 1B is insufficient, and if it is too large (for example, over 100 μm), the heat source Insufficient heat absorption from

Unlike the copper layer 11 of the upper plate 10, the copper layer 31 of the lower plate 30 constituting the housing 1B is formed with a plurality of recesses 41 by processing means such as press molding. The copper layer 21 has a thickness of at least 10 μm before forming the recesses 41 . The portion indicated by the thickness Tf is substantially the same as the thickness of the copper layer 31 before forming the plurality of recesses 41, and is, for example, 20 μm or more and 400 μm or less. Note that the portion indicated by the thickness Tf of the copper layer 31 and the portion indicated by the thickness Td and the portion indicated by the thickness Te in the plurality of recesses 41 formed by processing means such as press molding have approximately the same thickness. You can think that it will be The portion denoted by thickness Td and the portion denoted by thickness Te of copper layer 31 have a thickness of at least 10 μm, optionally at least 15 μm, and optionally a thickness of at least 15 μm. thickness of at least 20 μm.

When the lower plate 30 having the above configuration is exposed to a high temperature of, for example, 650° C. to 850° C., if the copper layer 31 has a thickness of at least 10 μm, the stainless steel layer 32 and the At a position 5 μm from the boundary of , the total content ratio of Cr, Mn, Fe and Ni obtained by the GD-OES analysis is 2% by mass or less. Therefore, on the surface of the copper layer 31 having a thickness of at least 10 μm of the lower plate 30, the total content ratio is certainly less than 2% by mass. In addition, when the copper layer 31 has a thickness of at least 15 μm, the total content ratio is 2% by mass or less at a position 5 μm from the boundary with the stainless steel layer 32 inside the copper layer 31, and the thickness is 10 μm. The total content ratio is 0.5% by mass or less at the position. Therefore, on the surface of the copper layer 31 having a thickness of at least 15 μm of the lower plate 30, the total content ratio is surely smaller than 0.5% by mass. In addition, when the copper layer 31 has a thickness of at least 20 μm, the total content ratio is 2% by mass or less at a position 5 μm from the boundary with the stainless steel layer 32 inside the copper layer 31, and the thickness is 10 μm. At the position of 15 μm, the total content ratio is 0.5% by mass or less, and at the position of 15 μm, the total content ratio is 0.2% by mass or less. Therefore, on the surface of the copper layer 31 having a thickness of at least 20 μm of the lower plate 30, the total content ratio is certainly smaller than 0.2% by mass. Therefore, the lower plate 30 having the structure described above can achieve the same effect as the clad plate according to the present invention. In addition, the boundary with the stainless steel layer 32 here intends the exfoliation surface 101a of the copper piece 100 described above.

Next, it will be explained that the total content ratio of Cr, Mn, Fe and Ni was used to evaluate the clad plate according to the present invention.

A clad plate is actually produced and evaluated. Specifically, first, a copper plate made of C1020 (99.96% by mass or more) and SUS316L (in mass%, C is 0.015%, Mn is 1.65%, Si is 0.47%, P is 0.025% S, 0.001% S, 16.5% Cr, 12.1% Ni, 2.1% Mo, and the balance being Fe and unavoidable impurities). Then, the copper plate and the stainless steel plate are tempered so that the difference in hardness between them is as small as possible.

Here, among the austenitic stainless steels (see JIS-G4305:2015) considered preferable for composing the clad plate according to the present invention, SUS301, SUS304 and SUS316L are commonly used. be. Of these, SUS316L is considered to be a suitable stainless steel for confirming the effects of the present invention because all of the above Si, Cr, Mn, Fe, Ni and Mo are specified. Note that Mo is not defined in SUS301 and SUS304.

Then, the copper plate and the stainless steel plate are roll-joined by clad rolling at a workability of about 60%. Then, diffusion annealing (nitrogen gas atmosphere, heating time of 1 minute, cooling time of 1 minute, air cooling) is performed at a temperature of 850° C. for 1 minute, and the copper layer is bonded to the stainless steel layer via the diffusion bonding layer. A bonded clad plate is produced. The clad plate has a thickness of 100 μm. The thickness of the copper layer of the clad plate is 75 μm. The thickness of the stainless steel layer of the clad plate is 25 μm. The thickness of the diffusion bonding layer of the clad plate is much thinner than the thickness of the copper layer and the thickness of the stainless steel layer, and is in the range of 0.1 μm or more and 1 μm or less.

Next, assuming that this clad plate is used for the upper plate 1 and lower plate 20 of the housing 1A (or the upper plate 10 and lower plate 30 of the housing 1B), the clad plate is heated at 650°C. Heat treatment is performed at a temperature of 950° C. to 950° C. for 1 minute. This heat treatment is applied to the upper plate 10 using the clad plate of the housing 1A and the lower plate 20 using the clad plate (or the upper plate 10 using the clad plate and the lower plate 30 using the clad plate of the housing 1B). This simulates the high-temperature environment that is exposed when joining by a joining means that involves heating.

Next, using the clad plate before and after the above heat treatment, a copper piece to be the specimen for GD-OES analysis is produced. A copper piece to be tested is prepared by stripping a copper layer from a clad plate and correcting the stripped copper layer to make it flat. The copper strip has a release surface (see strip surface 101a of copper strip 101 described above) containing residue of the diffusion bonding layer. The reference position for the analysis depth of the GD-OES analysis is the peeled surface of the copper piece. Then, GD-OES analysis (depth profile) is performed in the thickness direction of the copper piece from the peeled surface side. GD-OES analysis (depth profile) quantified Si, Cr, Mn, Ni and Mo, which are the main constituent elements of SUS316L, in addition to Cu, which is the main element of C1020, and Fe, which is the main element of SUS316L. Then, the distribution of each element inside the copper piece is confirmed.

Table 1 shows an example of the results of GD-OES analysis of a copper piece when the clad plate was heat-treated at the highest holding temperature of 950°C. Note that the numerical value for an analysis depth of 1 μm is not subject to evaluation, but is shown as a reference value. Also, the reason why Cu is the largest in the analysis depth is that it is inside the copper piece made of C1020.

In Table 1, when compared at an analysis depth of 5 μm, the content ratio of Si (0.005%) and Mo (0.004%) is Cr (0.288%), Mn (0.114%) , the content ratio of Fe (0.893%) and Ni (0.173%). In addition, the total content ratio (1.478%) that is the sum of the content ratios of the six elements excluding Cu shown in Table 1 and the total content ratio (1.478%) that is the sum of the content ratios of the four elements excluding Si and Mo shown in Table 1. 469%) is also sufficiently small (0.009%). This tendency is the same at positions with analysis depths of 10 μm and 15 μm.

As a result of heat-treating this clad plate at the highest holding temperature of 950 ° C., the content ratio of Si and Mo inside the copper piece is sufficiently small compared to the content ratio of Cr, Mn, Fe and Ni. It is confirmed that From this, even if the total content ratio of Cr, Mn, Fe and Ni is used to evaluate the total content ratio of the constituent elements of the stainless steel layer inside the copper piece by GD-OES analysis, there is a substantial problem. It is thought that there is no Therefore, the total content ratio of Cr, Mn, Fe and Ni is used for evaluation of the clad plate according to the present invention.

Next, the adoption of the heat treatment at a holding temperature of 950°C (holding time of 1 minute) for the evaluation of the clad plate according to the present invention will be explained.

Table 2 shows the results of the GD-OES analysis of the copper pieces, which are distinguished by the heat treatment conditions, for the case where the clad plate was heat treated for 1 minute at a temperature of 650 ° C. to 950 ° C. and where the heat treatment was not performed. It is an example of the result. The total content ratio shown in Table 2 is the sum of the content ratios of Cr, Mn, Fe and Ni. In addition, the numerical value shown in the 950 ° C. section is the content ratio of Cr, Mn, Fe and Ni when heat treatment is performed at the holding temperature of 950 ° C. shown in Table 1, and the content ratio when Si and Mo are excluded. It is converted. Moreover, "0.000" means less than 0.0005% by mass. "RT" means that the clad plate was not heat-treated. In addition, "RT contrast" is a value obtained by dividing the total content ratio of holding temperature by the total content ratio of RT for the same analysis depth. For example, for an analysis depth of 5 μm, the value obtained by dividing the total content ratio of 1.469% at a holding temperature of 950° C. by the total content ratio of RT of 0.064% (compared to RT) is 47.9.

In Table 2, comparing the RT ratio values without heat treatment (RT) and with heat treatment (holding temperature from 650 ° C to 950 ° C), it can be seen that the total content ratio definitely increases when heat treatment is performed. . Comparing the total content ratio at an analysis depth of 5 μm, for example, the total content ratio (0.140%) at a holding temperature of 650° C. is about 2.2 times (0.064%) at RT. RT contrast value). For example, the total content ratio (1.469%) at a holding temperature of 950° C. is about 22.8 times (RT relative value) higher than the total RT content ratio (0.064%). Moreover, when the holding temperature of the heat treatment is compared, it can be seen that the higher the holding temperature, the higher the total content ratio. For example, when comparing at an analysis depth of 5 μm, the total content tends to increase as the holding temperature increases, from 0.140% at a holding temperature of 650°C to 1.469% at 950°C. As a result, it is confirmed that the total content ratio is the largest when the holding temperature of the heat treatment is 950° C. (holding time of 1 minute).

As a result of heat-treating this clad plate at a holding temperature of 650° C. to 950° C. (holding time of 1 minute), the total content ratio of Cr, Mn, Fe and Ni in the copper piece was the highest. It is confirmed that the heat treatment at the high temperature holding temperature of 950° C. is the largest. From this, Cr, Mn, Fe and Ni when performing heat treatment at a holding temperature of 950 ° C. (holding time of 1 minute) for evaluating the total content ratio of the constituent elements of the stainless steel layer inside the copper piece by GD-OES analysis. It is considered that there is no substantial problem even if the total content ratio obtained by summing the content ratios is used. Therefore, the total content ratio of Cr, Mn, Fe and Ni when heat treatment is performed at a holding temperature of 950° C. (holding time of 1 minute) is used for evaluation of the clad plate according to the present invention.

As can be seen from the 5 μm and 10 μm analysis depth results shown in Table 2, the total 5 μm analysis depth position of the copper layer after the clad plate was exposed to high temperatures (see 650° C. to 950° C.) It is confirmed that the content ratio is definitely higher than the total content ratio at the analysis depth of 5 μm of the copper layer before exposure to high temperature (RT). On the other hand, the total content at an analytical depth of 10 μm of a copper layer having a thickness of at least 10 μm after exposure to high temperatures can be significantly smaller than the total content at an analytical depth of 5 μm. It is confirmed. From this result, although the total content ratio of the surface of the copper layer after the clad plate is exposed to high temperature is surely larger than the total content ratio of the surface of the copper layer before being exposed to high temperature (RT), It can be said that the total content of the surface of the copper layer with a thickness of at least 10 μm after exposure is definitely less than 5% by weight, for example 0.5% by weight or less. Therefore, even if the clad plate having a copper layer having a thickness of at least 10 μm according to the present invention is used, for example, in a vapor chamber (casing), it will not react with a working fluid such as water in contact with the surface of the copper layer. Reaction can be reliably suppressed.

Also, as can be seen from the results of analysis depth 10 μm and analysis depth 15 μm shown in Table 2, the position of the analysis depth 10 μm of the copper layer after the clad plate was exposed to high temperature (see 650° C. to 950° C.) It is confirmed that the total content of is definitely greater than the total content at the analysis depth of 10 μm of the copper layer before exposure to high temperature (RT). On the other hand, the total content at an analytical depth of 15 μm of a copper layer having a thickness of at least 15 μm after exposure to high temperature can be significantly smaller than the total content at an analytical depth of 10 μm. It is confirmed. From this result, although the total content ratio of the surface of the copper layer after the clad plate is exposed to high temperature is surely larger than the total content ratio of the surface of the copper layer before being exposed to high temperature (RT), It can be said that the total content of the surface of the copper layer having a thickness of at least 15 μm after exposure is less than 0.5% by weight, for example 0.2% by weight or less. Therefore, even if the clad plate having a copper layer having a thickness of at least 15 μm according to the present invention is used in, for example, a vapor chamber (casing), it will not react with a working fluid such as water in contact with the surface of the copper layer. Reaction can be reliably suppressed.

Further, as can be seen from the results of the analysis depth of 15 μm shown in Table 2, the total content ratio of the copper layer at the analysis depth of 15 μm after the clad plate is exposed to high temperature (see 650° C. to 950° C.) is , is definitely greater than the total content at the analysis depth of 15 μm of the copper layer before exposure to high temperature (RT). On the other hand, the total content ratio at the analysis depth of 10 μm of the copper layer after exposure to high temperature is sufficiently smaller than the total content ratio at the analysis depth of 5 μm. It is confirmed that the total content ratio is sufficiently smaller than the total content ratio at the analysis depth of 10 μm. From this result, it can be said that the total content on the surface of the copper layer having a thickness of at least 20 μm after the high temperature exposure of the clad plate is smaller than the total content at the analysis depth of 15 μm. Therefore, even if the clad plate having a copper layer having a thickness of at least 20 μm according to the present invention is used, for example, in a vapor chamber (housing), the reaction of a working fluid such as water in contact with the surface of the copper layer can be reliably suppressed.

1A. housing, 1B. housing, 10 . top plate, 11 . copper layer, 12. stainless steel layer, 20. lower plate, 21 . copper layer, 22 . stainless steel layer;30. lower plate, 31 . copper layer, 32 . stainless steel layer, 40. space, 41 . recess, 100 . clad plate, 101a. release surface, 101 . copper layer (copper strip), 102 . stainless steel layer, 103. Diffusion bonding layer

Claims

A clad plate comprising a stainless steel layer having a thickness of at least 15 μm and a copper layer having a thickness of at least 10 μm bonded in the thickness direction via a diffusion bonding layer,
The clad plate is heat-treated at 950 ° C. for 1 minute, the copper layer is peeled off from the clad plate after the heat treatment to form a copper piece, the copper piece is flattened, and the copper piece after the straightening is flattened. When GD-OES analysis was performed in the thickness direction from a randomly selected exfoliated surface to determine the total content ratio of Cr, Mn, Fe and Ni,
The clad plate, wherein the total content ratio at a position 5 μm from the peeled surface of the copper piece is 2% by mass or less.
the copper layer has a thickness of at least 15 μm;
The clad plate according to claim 1, wherein the total content ratio at a position 5 µm from the peeled surface of the copper piece is 2% by mass or less, and the total content ratio at a position 10 µm from the peeled surface is 0.5% by mass or less. .
the copper layer has a thickness of at least 20 μm;
The total content ratio at a position 5 μm from the peeled surface of the copper piece is 2% by mass or less, the total content ratio at a position 10 μm is 0.5% by mass or less, and the total content ratio at a position 15 μm 3. The clad plate according to claim 2, wherein the is 0.2% by mass or less.
The clad plate according to any one of claims 1 to 3, wherein the copper layer contains 99.0% by mass or more of Cu.
4. The stainless steel layer according to any one of claims 1 to 3, wherein the stainless steel layer is an austenitic stainless steel layer containing up to 15% by weight Ni, up to 20% by weight Cr and up to 2% by weight Mn. clad plate.
an upper plate comprising the clad plate according to any one of claims 1 to 3;
and a lower plate made of the clad plate according to any one of claims 1 to 3,
A housing comprising a space defined by diffusion bonding of the copper layer of the upper plate and the copper layer of the lower plate in a thickness direction.