Cu-Ti copper alloy sheet material, method for manufacturing the same, and vapor chamber

Abstract

The present invention provides a metal material suitable for vapor chamber housings, which exhibits high strength after being held at high temperatures (e.g., around 800°C) and achieves extremely high bonding strength at the diffusion bonding portion that exceeds that of pure copper. [Solution] A copper alloy sheet material having a chemical composition consisting of 2.00-5.00% by mass of Ti, and optionally containing Ag, Al, B, Be, Co, Cr, Fe, Hf, Mg, Mn, Mo, Nb, Ni, P, S, Si, Sn, Ta, V, Zn, Zr, and rare earth elements in a total of 4.00% or less, with the remainder being Cu and unavoidable impurities, a maximum height roughness Rz of the sheet surface in the direction perpendicular to the rolling direction of the sheet surface of 1.5 μm or less, and a developed area ratio Sdr of the sheet surface measured by a laser microscope of 0.10 or less.

Description

Technical Field

[0001] The present invention relates to a Cu-Ti-based copper alloy sheet having improved joint strength after diffusion bonding, a method for manufacturing the same, and a vapor chamber using the copper alloy sheet as a material.

Background Art

[0002] In electronic devices such as personal computers, tablet terminals, and smartphones, vapor chambers have attracted attention as cooling devices for efficiently discharging heat generated from processors such as CPUs. The casing of a vapor chamber is generally constructed by diffusion bonding or brazing the peripheral edges of an upper plate member and a bottom plate member made of a copper-based material so that a cavity is formed inside. As the copper-based material, a pure copper plate or a copper alloy plate is used. The pure copper plate is excellent in that the joint strength at the diffusion bonded portion is high, but has a disadvantage in that the strength of the material itself is greatly reduced by heating during diffusion bonding.

[0003] Patent Document 1 describes using a Cu-Ti-based copper alloy having a Ti content of 2.0 to 5.0% by mass as a material for the casing of a vapor chamber. The Cu-Ti-based copper alloy can achieve a high strength level among various copper-based materials and can maintain a higher strength than pure copper or other general copper alloys even after being held at a heating temperature during diffusion bonding (for example, about 800°C). According to Patent Document 1, in a test in which a test piece obtained by stacking three Cu-Ti-based copper alloy plates and performing diffusion bonding at 800°C is freely dropped 100 times from a height of 30 cm onto asphalt, no damage (peeling or gaps) occurs in the diffusion bonded portion, and a sound joint can be maintained.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

[0005] In recent years, with the increasing performance of electronic devices, the cooling devices they incorporate are required to be even more durable. In the case of vapor chamber housings, it is particularly important to achieve both high material strength and improved joint strength at the joints. According to the technology described in Patent Document 1, by using a Cu-Ti copper alloy, the strength of the material itself is maintained at a high level even after being held at the diffusion bonding temperature (for example, around 800°C). However, the joint strength at the diffusion bonding joint is not as good as that of pure copper, leaving room for improvement.

[0006] The present invention aims to provide a metal material suitable for vapor chamber housings that exhibits strength after being held at high temperatures (e.g., around 800°C) comparable to that of copper alloy plate materials for vapor chambers disclosed in Patent Document 1, and that achieves extremely high bonding strength exceeding that of pure copper materials at the diffusion bonding portion. [Means for solving the problem]

[0007] To achieve the above objectives, the following inventions are disclosed herein. [1]In mass%, Ti: 2.00~5.00%, Ag: 0~0.30%, Al: 0~3.00%, B: 0~0.30%, Be: 0~0.15%, Co: 0~1.00%, Cr: 0~1.00%, Fe: 0~1.00%, Hf: 0~1.00%, Mg :0~1.00%, Mn:0~1.50%, Mo:0~1.00%, Nb:0~0.50%, Ni:0~1.50%, P:0~0.20%, S:0~0.20%, Si:0~1.00%, Sn:0~1.50%, Ta:0~1.00%, V:0~1. A copper alloy sheet material having a chemical composition of 00%, Zn: 0-2.00%, Zr: 0-1.00%, total rare earth elements: 0-3.00%, with a total of Ag, Al, B, Be, Co, Cr, Fe, Hf, Mg, Mn, Mo, Nb, Ni, P, S, Si, Sn, Ta, V, Zn, Zr and rare earth elements of 4.00% or less, with the remainder being Cu and unavoidable impurities, a maximum height roughness Rz of the sheet surface in the direction perpendicular to rolling of 1.5 μm or less, and a sheet surface development area ratio Sdr measured by laser microscope of 0.10 or less. [2] In the elemental concentration profiles of Cu, Ti, O, and C measured by XPS (X-ray photoelectron spectroscopy), the surface region from the outermost surface to the SiO2 equivalent depth (nm) where the proportion of O in the four elements is 5.0 atomic% or less is called the oxygen-enriched layer, and the thickness of the oxygen-enriched layer is 100 nm or less, as described in [1] above. [3] The copper alloy sheet material described in [1] or [2] above, wherein the 0.2% yield strength in the rolling direction after being subjected to a heat treatment test in which the material is held at 800°C for 1 hour in a nitrogen atmosphere is 400 MPa or more. [4] A copper alloy sheet material as described in any of [1] to [3] above, with a thickness of 0.01 to 0.50 mm. [5] A copper alloy sheet material according to any of [1] to [4] above, wherein the Ti content in the chemical composition is 2.80 to 5.00%, and the developed area ratio Sdr is 0.08 or less. [6] A copper alloy sheet material according to any of [1] to [4] above, wherein the Ti content in the chemical composition is 2.80 to 5.00%, the maximum height roughness Rz is 1.1 μm or less, and the developed area ratio Sdr is 0.06 or less. [7] The copper alloy sheet according to any one of [1] to [6] above, which is for a vapor chamber housing.

[0008] [8] When manufacturing a copper alloy sheet by subjecting an intermediate product sheet to solution treatment, aging treatment, finish cold rolling, and finish heat treatment in this order, the finish cold rolling is performed using a work roll having a roll surface with a maximum height roughness Rz in the roll axis direction of 1.7 μm or less, under the condition that the rolling ratio is 5.0 to 20.0%, the finish heat treatment is performed under the condition of holding at 300 to 500 °C for 10 to 300 seconds, A method for manufacturing a copper alloy sheet according to any one of [1] to [7] above.

[0009] [9] A vapor chamber having a housing with a structure in which two or more members using the copper alloy sheet according to any one of [1] to [7] above are joined by diffusion bonding or brazing.

[0010] In this specification, "sheet material" means a sheet-like metal material. A thin sheet-like metal material may also be called "foil", and such "foil" is also included in the "sheet material" referred to here. A long sheet-like metal material wound in a coil shape is also included in the "sheet material". Also, in this specification, the thickness of the sheet-like metal material is called "plate thickness". "Plate surface" is the surfaces at both ends in the thickness direction of the plate, and may also be called "rolling surface". In this specification, the notation "n1~n2" indicating a numerical range means "n1 or more and n2 or less". Here, n1 and n2 are numerical values that satisfy n1 < n2.

[0011] The rolling ratio (%) in a certain rolling process is determined by the following formula (1). Rolling ratio (%) = 100 × (h0 - h1) / h0 … (1) h0: The plate thickness (mm) before being subjected to the first pass of rolling in that rolling process h1: The plate thickness (mm) when the final rolling pass in that rolling process is completed [Effects of the Invention]

[0012] According to the present invention, a copper alloy sheet has been realized that has a strength after being held at a high temperature (for example, about 800°C) equivalent to that of a copper alloy sheet for a vapor chamber disclosed in Patent Document 1, and has a very high joining strength exceeding that of a pure copper sheet at the diffusion joining portion. This material is extremely useful as a copper alloy sheet (copper alloy sheet for vapor chamber housing) for constructing the housing of a vapor chamber where the need for high durability is increasing.

Brief Description of the Drawings

[0013] [Figure 1] Fig. showing an example of the elemental concentration profile in the depth direction from the outermost surface of a Cu-Ti-based copper alloy sheet according to the present invention by XPS. [Figure 2] Fig. schematically showing the state where a test piece for measuring the joining strength of the diffusion joining portion is set in a tensile testing machine.

Embodiments for Carrying out the Invention

[0014] [Chemical Composition] Hereinafter, “%” regarding alloy components means “mass %” unless otherwise specified. Ti (titanium) brings about the formation of a modulated structure of Ti by spinodal decomposition and the formation of fine second-phase particles by precipitation, and is an element that contributes to the increase in strength of the Cu-Ti-based copper alloy of the present invention. It also contributes to the reduction of stress relaxation resistance improvement. In addition to these conventionally known effects, it has been confirmed that Ti has an effect of improving the joining strength at the diffusion joining portion when held at a high temperature of about 800°C.

[0015] According to the inventors' investigation, XPS analysis confirmed that when a Cu-Ti copper alloy sheet containing a predetermined amount of Ti is subjected to heat treatment by holding it at a high temperature in a non-oxidizing atmosphere (for example, 800°C for 1 hour), a Ti-enriched layer is formed near the material surface. It was also found that this Ti-enriched layer is formed at the bonding interface during diffusion bonding. It is presumed that the formation of such a Ti-enriched layer contributes to the improvement of the bonding strength of the diffusion bond. However, in order to achieve a bonding strength that is even higher than that of pure copper, further adjustment of the surface properties (maximum height roughness Rz and developed area ratio Sdr), as described later, is also important.

[0016] To fully exert these effects, a Ti content of 2.00% or more should be ensured. Excessive Ti content can reduce hot and cold workability, so the Ti content should be limited to 5.00% or less. A more preferable range for the Ti content is 2.80 to 5.00 mass%, and an even more preferable range is 3.00 to 4.85 mass%.

[0017] Ag (silver), Al (aluminum), B (boron), Be (beryllium), Co (cobalt), Cr (chromium), Fe (iron), Hf (hafnium), Mg (magnesium), Mn (manganese), Mo (molybdenum), Nb (niobium), Ni (nickel), P (phosphorus), S (sulfur), Si (silicon), Sn (tin), Ta (tantalum), V (vanadium), Zn (zinc), Zr (zirconium) and rare earth elements are optional elements. One or more of these can be contained as required. For example, Al is effective in suppressing the formation of coarse precipitates in Cu-Ti-based copper alloys and is also effective in reducing the density (specific gravity) of copper alloys. Ni, Co, Fe, Nb form intermetallic compounds with Ti and contribute to the improvement of strength. Also, since the intermetallic compounds of these elements suppress the coarsening of crystal grains, it becomes possible to perform solution treatment in a higher temperature range in the manufacture of copper alloy sheets, which is advantageous for sufficiently dissolving Ti. Ag, Mo, Sn, Ta have a solid solution strengthening effect and an effect of improving stress relaxation resistance. Be can form a CuBe precipitation phase and contribute to the improvement of strength and conductivity. Zn is effective in improving solderability and strength, and is also effective in improving castability. Mg has an effect of improving stress relaxation resistance and a desulfurization effect. Si can form a compound with Ti, contributes to pinning during recrystallization in the manufacture of copper alloy sheets, and can reduce the crystal grain size. Cr, Zr are effective in dispersion strengthening and suppressing the coarsening of crystal grains. Mn, V are likely to form high melting point compounds with S etc., and B, P have an effect of refining the cast structure, so they can each contribute to the improvement of hot workability. Hf has an effect of reducing the solid solubility limit of Ti, so it is effective in increasing the amount of precipitate formation during aging and improving conductivity.

[0018] The rare earth elements (REM) are Sc (scandium), Y (yttrium) in Group 3 of the periodic table, and lanthanoid series elements (excluding Pm (promethium)). The inclusion of rare earth elements is effective in refining crystal grains and dispersing precipitates. Mischmetal (a mixture of rare earth elements) may be used as a source of rare earth elements.

[0019] Ti and the remainder of the above optional elements can be Cu (copper) and inevitable impurities.

[0020] The content of the above-mentioned arbitrary elements can be in the range of Ag: 0-0.30%, Al: 0-3.00%, B: 0-0.30%, Be: 0-0.15%, Co: 0-1.00%, Cr: 0-1.00%, Fe: 0-1.00%, Hf: 0-1.00%, Mg: 0-1.00%, Mn: 0-1.50%, Mo: 0-1.00%, Nb: 0-0.50%, Ni: 0-1.50%, P: 0-0.20%, S: 0-0.20%, Si: 0-1.00%, Sn: 0-1.50%, Ta: 0-1.00%, V: 0-1.00%, Zn: 0-2.00%, Zr: 0-1.00%, and the total of rare earth elements: 0-3.00%. These optional elements may be included in a total amount of 4.00% by mass or less. Regarding rare earth elements, for example, a range can be given in which one or more elements selected from La (lanthanum): 2.00% or less, Ce (cerium): 1.80% or less, Pr (praseodymium): 0.30% or less, Nd (neodymium): 0.80% or less, Sm (samarium): 2.50% or less, and Y (yttrium): 2.50% or less are included, and the total content of rare earth elements is 3.00% or less.

[0021] Furthermore, more preferable content ranges for the above-mentioned arbitrary elements include Ag: 0-0.20%, Al: 0-2.50%, B: 0-0.20%, Be: 0-0.10%, Co: 0-0.80%, Cr: 0-0.80%, Fe: 0-0.80%, Hf: 0-0.80%, Mg: 0-0.80%, Mn: 0-1.00%, Mo: 0-0.80%, Nb: 0-0.30%, Ni: 0-1.00%, P: 0-0.15%, S: 0-0.15%, Si: 0-0.80%, Sn: 0-1.00%, Ta: 0-0.80%, V: 0-0.80%, Zn: 0-1.50%, Zr: 0-0.80%, and a total of 0-2.50% for rare earth elements. In this case, it is preferable that the total content of these optional elements be 3.00% or less. A more preferable range for rare earth element content, taking into consideration economic efficiency and manufacturability, is, for example, a range in which one or more elements selected from La: 0.30% or less, Ce: 0.70% or less, Pr: 0.20% or less, Nd: 0.30% or less, Sm: 0.20% or less, and Y: 0.40% or less are included, and the total content of rare earth elements is 2.50% or less.

[0022] Furthermore, more preferable content ranges for the above-mentioned arbitrary elements include Ag: 0-0.10%, Al: 0-1.60%, B: 0-0.07%, Be: 0-0.04%, Co: 0-0.30%, Cr: 0-0.30%, Fe: 0-0.20%, Hf: 0-0.15%, Mg: 0-0.30%, Mn: 0-0.50%, Mo: 0-0.30%, Nb: 0-0.15%, Ni: 0-0.50%, P: 0-0.07%, S: 0-0.07%, Si: 0-0.30%, Sn: 0-0.50%, Ta: 0-0.20%, V: 0-0.30%, Zn: 0-0.70%, Zr: 0-0.40%, and a total of 0-1.00% for rare earth elements. In this case, it is preferable that the total content of these optional elements be 2.00% or less. A more preferable range for the content of rare earth elements, taking into consideration economic efficiency and manufacturability, is, for example, a range in which one or more elements selected from La: 0.18% or less, Ce: 0.35% or less, Pr: 0.10% or less, Nd: 0.15% or less, Sm: 0.10% or less, and Y: 0.20% or less are included, and the total content of rare earth elements is 1.00% or less.

[0023] Other elements may also be included as long as they do not hinder the objective of the present invention (achieving both high strength after high-temperature holding and a significant improvement in bonding strength at the diffusion joint). Specifically, the total content of elements other than Ti, Ag, Al, B, Be, Co, Cr, Fe, Hf, Mg, Mn, Mo, Nb, Ni, P, S, Si, Sn, Ta, V, Zn, Zr, rare earth elements, and Cu (hereinafter sometimes referred to as "non-specified elements") is preferably 0.50% or less, and may be controlled to 0.10% or less. The content of non-specified elements can be determined, for example, by quantifying substantially all elements that may be contained in the copper alloy sheet material using the following analytical method.

[0024] (Example of a method for quantifying alloying elements) Oxygen (O) and nitrogen (N) are quantified using an oxygen-nitrogen-hydrogen analyzer (e.g., LECO ONH-836), hydrogen (H) is quantified using a hydrogen analyzer (e.g., Horiba EMGA-921), carbon (C) and sulfur (S) are quantified using a carbon-sulfur analyzer (e.g., LECO CS844), elements from the 2nd to 6th periods (excluding C, N, O, group 17 elements, group 18 elements, technetium (Tc), polonium (Po), and promethium (Pm)) are quantified using ICP-MS (e.g., Agilent 7900), and fluorine (F), chlorine (Cl), and bromine (Br) are quantified using a combustion-ion chromatography apparatus (e.g., Thermo Scientific DIONEX ICS-1600).

[0025] The chemical composition of the copper alloy plate material according to the present invention can be specified as "consisting of Ti, the above arbitrary elements (including cases where the total is 0% by mass), the remainder being Cu and unavoidable impurities," or it can be specified as "consisting of Ti, the above arbitrary elements (including cases where the total is 0% by mass), the above non-specified elements (including cases where the total is 0%), and the remainder being Cu."

[0026] [Maximum height and roughness of the board surface Rz] To improve the diffusion bonding properties of metallic materials, it is generally considered effective to reduce the surface roughness of both metallic materials that form the bonding surface. As a result of various studies, in the case of the Cu-Ti copper alloy of the above composition, which is the subject of this invention, it is important that the maximum height roughness Rz in the direction perpendicular to the rolling direction on the plate surface (the direction perpendicular to the rolling direction on the plate surface) is 1.5 μm or less, and 1.1 μm or less is more effective in order to stably maintain a high bonding strength of the diffusion bonding part. Note that the maximum height roughness Rz is usually 0.2 μm or more. Here, the above Rz is the maximum height roughness specified in JIS B0601:2013. The maximum height roughness Rz in the direction perpendicular to the rolling direction on the plate surface can be controlled to a small value by strictly controlling the surface roughness of the work roll used in the final cold rolling process (finish cold rolling).

[0027] [Ratio of unfolded surface area of ​​the board (Sdr)] In the Cu-Ti copper alloy sheet material of the above composition, which is the subject of the present invention, specifying only the maximum height roughness Rz is insufficient to significantly improve the bonding strength of the diffusion bond, and further surface smoothness is required. According to the inventors' research, by satisfying the above-mentioned Rz specification and exhibiting surface properties in which the unfolded area ratio Sdr of the sheet surface measured by a laser microscope is 0.10 or less, a very high bonding strength exceeding that of pure copper material can be obtained in the diffusion bond. The unfolded area ratio Sdr is an index that represents the proportion of the field of view (projected area) to which the actual surface area, including surface irregularities of the material surface appearing in a field of view is larger when the material surface is observed in a certain field of view. This unfolded area ratio Sdr is a surface parameter specified in ISO 25178 and can be measured using a confocal laser microscope. Specifically, the measurement method shown in the examples described later can be employed. The unfolded area ratio Sdr is more preferably 0.10 or less, and it is also possible to adjust it to 0.05 or less. To control the unfolded area ratio Sdr to a small value, it is effective to strictly control the surface roughness of the work rolls used in the final cold rolling process (finish cold rolling) as described above, and to keep the rolling rate in that rolling process low. However, if the rolling rate is too low, it becomes difficult to keep the maximum height roughness Rz within the specified range, so the unfolded area ratio Sdr should usually be adjusted to a range of 0.01 or higher.

[0028] [Thickness of the oxygen-enriched layer on the board surface] In Cu-Ti copper alloy sheet materials, a region with a higher oxygen concentration than the interior exists near the surface after the final heat treatment process (finishing heat treatment) which is usually performed in a non-oxidizing atmosphere. In this specification, the surface region from the outermost surface to the SiO2 equivalent depth (nm) where the proportion of O in the four elements is 5.0 atomic% or less in the elemental concentration profile in the depth direction for Cu, Ti, O, and C measured by XPS (X-ray photoelectron spectroscopy) is referred to as the "oxygen-enriched layer".

[0029] Figure 1 shows an example of the elemental concentration profile in the depth direction from the outermost surface, obtained by XPS, for a Cu-Ti copper alloy plate material according to the present invention. The scale on the horizontal axis represents the SiO2 equivalent depth (nm) from the outermost surface. In this example, the SiO2 equivalent depth at which the proportion of O in the total 100 atomic percent of the four elements Cu, Ti, O, and C ultimately becomes 5.0 atomic percent or less (i.e., never exceeds 5.0 atomic percent) is 3.2 nm. Therefore, the thickness of the oxygen-enriched layer determined from this elemental concentration profile is 3.2 nm.

[0030] According to the inventors' studies, it was found that the thinness of the oxygen-enriched layer is also advantageous for improving the bonding strength at the diffusion joint. Specifically, the thickness of the oxygen-enriched layer is preferably 100 nm or less, more preferably 50 nm or less, and it is also possible to obtain one with a thickness of 10 nm or less. In the final heat treatment process (finishing heat treatment) performed in a non-oxidizing atmosphere, when comparing cases with the same atmosphere, the thickness of the oxygen-enriched layer is affected by the temperature and holding time in the heat treatment, but shortening the holding time as much as possible is particularly effective in reducing the thickness of the oxygen-enriched layer. The thickness of the oxygen-enriched layer is usually 1 nm or more.

[0031] [0.2% yield strength after high-temperature holding] When assembling the housing of a vapor chamber, it is common practice to diffuse-bond or braze the upper plate member and the bottom plate member, which are housing components, so that their peripheral edges are in close contact, in order to form a cavity through which the working fluid circulates. During this bonding process, the housing components are heated and held at a high temperature (for example, around 800°C in the case of diffusion bonding). Therefore, it is important for the metal material used for the housing components not to suffer a significant decrease in strength due to softening when held at high temperatures in order to construct a highly durable vapor chamber. According to the inventors' research, in order to adequately meet the demands of high-performance processors mounted in electronic devices, it is desirable to use a copper alloy sheet material that exhibits softening resistance such that the 0.2% yield strength in the rolling direction after being subjected to a heat treatment test in which it is held at 800°C in a nitrogen atmosphere for one hour is 400 MPa or more. The Cu-Ti copper alloy sheet material of the present invention, which contains the above-mentioned predetermined amount of Ti, can adequately satisfy the above-mentioned softening resistance requirement and can also achieve excellent softening resistance such as a 0.2% yield strength of 600 MPa or more, or even 720 MPa or more, after the above-mentioned high-temperature holding. There is no particular upper limit to the 0.2% yield strength after the above-mentioned high-temperature holding, but it is usually in the range of 800 MPa or less.

[0032] [Efficiency after high-temperature holding] In recent years, with the miniaturization and weight reduction of mobile devices, there has been an increasing demand for thinner vapor chambers used in mobile devices. To thin a vapor chamber, it is effective to reduce the thickness of the top and bottom plates that make up the vapor chamber housing. However, in this case, the contribution of the housing to thermal resistance becomes smaller, so the importance of increasing the thermal conductivity (electrical conductivity) of the plate material used for the housing is relatively lower compared to maintaining strength after high-temperature holding. According to the inventors' studies, for copper alloy plate material used for the housing of a thin vapor chamber, if the electrical conductivity after a heat treatment test in which it is held at 800°C in a nitrogen atmosphere for 1 hour is, for example, 10.0%IACS or higher, it can be judged that it has a level of thermal conductivity that is not problematic in practice. The electrical conductivity of the copper alloy plate material of the present invention is usually 20.0%IACS or lower.

[0033] [Thickness of the titanium-enriched layer on the plate surface after high-temperature holding] As described above, in Cu-Ti copper alloy sheet materials, when held at high temperatures in a non-oxidizing atmosphere, a phenomenon of Ti concentration is observed near the surface of the sheet material. In this specification, when a sheet material sample of Cu-Ti copper alloy sheet material (after the finishing heat treatment described later) is subjected to heat treatment by holding it at 800°C in a nitrogen atmosphere for 1 hour, and the elemental concentration profiles in the depth direction for Cu, Ti, O, C, and N are measured by XPS (X-ray photoelectron spectroscopy), the surface region from the outermost surface to the SiO2 equivalent depth (nm) where the proportion of Ti in the total 100% of the five elements becomes 9.0 atomic% or less (i.e., does not exceed 9.0 atomic%) is referred to as the "titanium-enriched layer." It is presumed that the property of forming this type of titanium-enriched layer contributes to improving the bonding strength of the diffusion bond. It is preferable that this titanium-enriched layer has a property of being 50 nm or more, and more preferable that it has a property of being 100 nm or more. This titanium-enriched layer is usually 300 nm or less. The property of sufficiently forming a titanium-enriched layer can be obtained by setting the Ti content in the copper alloy to 2.00 to 5.00 mass%.

[0034] [Bond strength of diffusion joint] As described above, the Cu-Ti copper alloy sheet material according to the present invention can be used as a material for assembling the housing of a vapor chamber, and when diffusion bonding is performed, for example, by heating to about 800°C, it does not cause a significant decrease in strength due to high-temperature softening. In addition, when diffusion bonding is performed using the Cu-Ti copper alloy sheet material, a diffusion bond with very high bonding strength can be formed. Specifically, the copper alloy sheet material according to the present invention has the property that the bonding strength of the diffusion bond obtained by the method described in the examples below is 75 MPa or more, and it is also possible to achieve a bonding strength of 90 MPa or more, or even 120 MPa or more. The higher the bonding strength, the better, but it is usually 250 MPa or less. From the viewpoint of achieving particularly high bonding strength, Cu-Ti copper alloy sheet materials that satisfy the conditions of having a Ti content of 2.80 mass% or more and an unfolded area ratio Sdr of 0.08 or less are more preferred, and Cu-Ti copper alloy sheet materials that satisfy the conditions of having a Ti content of 2.80 mass% or more, a maximum height roughness Rz of 1.1 μm or less and an unfolded area ratio Sdr of 0.06 or less are even more preferred. In these cases, a Ti content of 3.00 mass% or more is more effective.

[0035] [Manufacturing method] The copper alloy sheet material described above can be manufactured, for example, by the following manufacturing process. Melting and casting → Hot working → Rough cold rolling → Solution treatment → Aging treatment → Finish cold rolling → Finish heat treatment Although not mentioned in the above process, surface machining is performed as needed after hot working, and pickling, polishing, or further degreasing is performed as needed after each heat treatment. The following describes each of the above processes.

[0036] [Melting and Casting] Cast slabs with the chemical composition specified in this invention can be produced using a crucible furnace or the like. To prevent oxidation of Ti, it is preferable to carry out the process in an inert gas atmosphere or a vacuum melting furnace.

[0037] [Hot working, cold rolling] The slab heating before hot working can be carried out, for example, by holding it at 900-1000°C for 0.5-5 hours. The method of hot working is not particularly limited. Typically, hot rolling or hot forging is used. In the case of hot rolling, the total hot rolling ratio should be, for example, 60-99%. After the hot working is completed, it is preferable to rapidly cool it by water cooling or the like. Next, cold rolling is performed. Cold rolling at this stage is referred to as "rough cold rolling" in this specification. The rolling ratio in rough cold rolling can be, for example, 50-99%. In this way, an intermediate product sheet material for solution treatment can be obtained.

[0038] [Solution treatment] The above-mentioned intermediate product sheet material is subjected to solution treatment. Conventional methods can be used for the solution treatment. For example, the intermediate product sheet material can be held at 800 to 1050°C for 10 to 1000 seconds.

[0039] [Statute of limitations treatment] After solution treatment, the material is subjected to aging treatment. The aging treatment can be carried out by holding the material at 400-600°C, preferably 400-500°C, for 1-24 hours. This causes fine precipitates to form, increasing the strength of the copper alloy sheet material.

[0040] [Finishing cold rolling] After aging treatment, finish cold rolling is performed with a rolling ratio of 5.0 to 20.0%, preferably 10.0 to 15.0%, for the purpose of adjusting the final plate thickness and surface smoothness of the plate surface. The final plate thickness can be adjusted in a range of, for example, 0.01 to 0.50 mm, depending on the application. In this finish cold rolling, it is important to use work rolls with strictly controlled surface roughness. Specifically, work rolls are used that have a roll surface with a maximum height roughness Rz (JIS B0601:2013) in the roll axis direction of 1.7 μm or less, more preferably 1.2 μm or less. Since extreme smoothing of the work roll surface leads to increased costs, it is usually sufficient to adjust the Rz of the work roll surface to a range of 0.20 μm or more. If the Rz of the work roll surface is too large, it becomes difficult to stably adjust the maximum height roughness Rz in the direction perpendicular to the rolling of the plate surface to the predetermined range mentioned above. Furthermore, if the rolling rate is too low, the shape of the highly smooth work roll surface cannot be sufficiently transferred to the material's sheet metal surface, making it difficult to stably adjust the Rz of the sheet metal surface within a predetermined range. On the other hand, if the rolling rate is too high, the unfolded area ratio Sdr of the material's sheet metal surface becomes high. Therefore, from the viewpoint of sufficiently increasing the bonding strength of the diffusion joint, controlling the surface properties of the work roll and the rolling rate are extremely important in finish cold rolling. In particular, in order to control the unfolded area ratio Sdr of the resulting sheet metal to a low value such as 0.08 or less and improve the post-joint strength of the diffusion joint, it is effective to control the upper limit of the rolling rate to a range of 15.0% or less. Furthermore, when aiming to further improve the post-joint strength of the diffusion joint by controlling the unfolded area ratio Sdr of the resulting sheet metal to an even lower value such as 0.06 or less and controlling the maximum height roughness Rz to a low value such as 1.1 μm or less, it is more effective to apply a work roll in which the maximum height roughness Rz in the roll axis direction is controlled to 1.2 μm or less.

[0041] [Finishing heat treatment] The material, after finishing cold rolling, is subjected to a finishing heat treatment held at 300-500°C for 10-300 seconds, more preferably at 400-470°C for 30-200 seconds. This reduces the strain energy of the crystal lattice introduced by finishing cold rolling, thereby improving workability. This finishing heat treatment is performed in a non-oxidizing atmosphere, and in the production of Cu-Ti copper alloy sheets, it can normally be performed in a continuous annealing furnace or a batch-type annealing furnace. Even when heat treatment is performed in a non-oxidizing atmosphere, it is difficult to completely avoid the intrusion of oxygen into the region near the outermost surface of the sheet, but normally this type of oxygen intrusion does not cause problems in terms of material properties. However, according to the inventors' studies, in applications for diffusion bonding, it is preferable to minimize the intrusion of oxygen near the outermost surface, that is, to control the thickness of the oxygen-enriched layer so that it does not become too thick, from the viewpoint of improving the bonding strength at the diffusion bonding portion. Therefore, the finishing heat treatment is performed using a continuous annealing furnace with a short heating and holding time of 300 seconds or less, or 200 seconds or less.

[0042] [Vapor chamber] As described above, the copper alloy sheet material of the present invention exhibits significantly higher material strength compared to pure copper after exposure to high temperatures (for example, around 800°C for diffusion bonding) during diffusion bonding or brazing. Furthermore, regarding the bonding strength of the diffusion bond, which was an area where improvement was desired in conventional Cu-Ti copper alloys, a very high bonding strength exceeding that of pure copper is achieved. Therefore, a vapor chamber having a housing structure in which two or more members made of copper alloy sheet material according to the present invention are joined by diffusion bonding or brazing exhibits superior durability compared to conventional vapor chambers using pure copper sheets or known Cu-Ti copper alloy sheet materials. [Examples]

[0043] Except for Comparative Example No. 48, copper alloys with the chemical compositions shown in Tables 1 to 4 were melted, the resulting slabs were heated, hot-rolled to the plate thicknesses shown in Tables 1 to 4, and then water-cooled. After hot-rolling, the oxide layer on the surface was removed by mechanical polishing (surface grinding), and then rough cold-rolling was performed under the conditions in Tables 1 to 4 to obtain intermediate product plates for solution treatment. However, in Comparative Example No. 46, homogenization annealing was performed before rough cold-rolling, and in Comparative Example No. 50, intermediate annealing and intermediate cold-rolling were performed after rough cold-rolling. Except for Comparative Example No. 48, elemental analysis was performed on analytical samples taken from cast slabs using the method described in "Examples of Methods for Quantifying Alloy Elements" above. In all examples, the total content of elements other than Ti, Ag, Al, B, Be, Co, Cr, Fe, Hf, Mg, Mn, Mo, Nb, Ni, P, S, Si, Sn, Ta, V, Zn, Zr, rare earth elements, and Cu was 0.10% or less.

[0044] Except for Comparative Example No. 48, the above intermediate product sheet materials were subjected to solution treatment, aging treatment, finish cold rolling, and finish heat treatment in the order shown in Tables 1 to 4 to obtain test materials for the various evaluations described later. However, in Comparative Example No. 42, cracks occurred in the material during hot rolling, so the process was stopped. Also, in Comparative Example No. 46, intermediate cold rolling and a second solution treatment were performed before the aging treatment. In Tables 1 to 4, a "-" (hyphen) indicates that the process was not performed. The finish heat treatment was performed under a nitrogen atmosphere. The thickness of the test material is shown in the "Final Thickness" column. For Comparative Example No. 48, a commercially available pure copper (C1020) sheet material (thickness 0.30 mm) was prepared and used as the test material. For the work rolls used in finish cold rolling, the surface roughness of the rolls parallel to the roll axis was measured using a SURFCOM 1400G manufactured by Tokyo Seimitsu Co., Ltd. before use. The table shows the maximum height roughness Rz (JIS B0601:2013) obtained from this measurement. The following investigations were conducted on each test specimen.

[0045] (XPS measurement) Samples cut from each test material were heat-treated by holding them at 800°C in a nitrogen atmosphere for 1 hour, followed by air cooling. These heat-treated samples are referred to as "high-temperature held samples." Elemental analysis was performed in the depth direction from the plate surface using XPS for both the test material sample (after finishing heat treatment) and the sample after the aforementioned high-temperature holding. The XPS instrument used was a PHI5000 VersaProbeIII manufactured by ULVAC-PHI, Inc. The analysis area was φ100 μm, acceleration voltage: 15 kV, pass energy: 140 eV, X-ray source: monochromatic AlKα, X-ray source output: 25 W, and analysis angle: 45°. For determining atomic concentrations, spectra were used for Cu (2p orbital), Ti (2p orbital), O (1s orbital), C (1s orbital), and N (1s orbital). The mole fractions of Cu, Ti, O, C, and N were calculated using the instrument's built-in computer. The Shirley method was used for background processing. Surface sputtering for depth direction analysis was performed using an argon ion gun with the ion species Ar + The experiment was conducted under the following conditions: acceleration voltage: 2kV, emission current: 7mA, sputtering rate: 5nm / min (SiO2 equivalent). For the test material samples (in the state after finishing heat treatment), the thickness of the oxygen-enriched layer was defined as the SiO2 equivalent depth (nm) at which the proportion of O in the four elements Cu, Ti, O, and C was 5.0 atomic percent or less. For samples held at high temperatures, the thickness of the titanium-enriched layer was defined as the SiO2 equivalent depth (nm) at which the proportion of Ti among the five elements Cu, Ti, O, C, and N was 9.0 atomic percent or less. Furthermore, in the state where Ti has not diffused to the surface (sample before high-temperature holding), the percentage of Ti is often less than 4.0 atomic percent.

[0046] (Rz in the direction perpendicular to the rolling of the plate surface) The maximum height roughness Rz in the direction perpendicular to the rolling direction (TD) of the plate surface of the test material was measured using a contact-type surface roughness meter (SURFCOM 1400G, manufactured by Tokyo Seimitsu Co., Ltd.) in accordance with JIS B0601:2013. Measurements were performed with n=5 repetitions, and the arithmetic mean was adopted as the Rz value of the test material.

[0047] (Sdr - ratio of the unfolded surface area of ​​the board) The unfolded area ratio (Sdr) specified in ISO 25178 was measured on the plate surface of the test material using a laser microscope (Keyence Corporation, Laser Microscope VX-X3000 series) by the following method. The sample cut from the test material was set so that the rolling direction was lateral to the microscope field of view. The laser microscope objective lens magnification was 50x, the scan mode was focus variation, the measurement size was 1024 × 768, the measurement quality was standard, and the pitch was 0.16 μm. Furthermore, the Sdr calculation was performed using the filtering and calculation conditions shown below. S filter: None F-operation: Plane tilt correction L filter: None Area to be calculated: 270 μm × 200 μm Measurements are taken for five randomly selected, non-overlapping fields of view, and the arithmetic mean of the Sdr values ​​obtained for each field of view is adopted as the Sdr value of the board surface of the test material.

[0048] (Bond strength of the diffusion joint) Two plate samples, approximately 25 mm wide and with their longitudinal direction oriented in the rolling direction, were cut from the test material and placed on top of each other. A 3.0 mm x 2.5 mm (area 7.5 mm) area was placed in the center of the overlapping portion. 2 To form the joint, a carbon sheet was sandwiched in the areas other than the central part, and diffusion bonding was performed. Diffusion bonding was carried out by hot pressing in a nitrogen atmosphere, with a bonding area of ​​7.5 mm². 2 The test was conducted under the following conditions: joining load of 10kN, joining temperature of 800°C, and joining time of 1 hour. To apply shear force to the diffusion joint, one end of the plate sample was restrained in the upper chuck of a tensile testing machine (Shimadzu Corporation, AG-X), and the other end of the plate sample was restrained in the lower chuck. A tensile test was performed at room temperature at a tensile speed of 1.0 mm / min, and the load at which the joint fractured was measured over the initial area of ​​the joint (7.5 mm²). 2The fracture stress per unit area (MPa), determined by dividing by ), was defined as the joint strength. This test was repeated n=5 times, and the arithmetic mean of the five joint strength values ​​was adopted as the joint strength value of the test material. Since the joint strength under similar conditions using a pure copper plate sample, which is considered to have good diffusion bonding properties, is 72 MPa (see Comparative Example No. 48), a joint strength of 75 MPa or higher was judged as acceptable.

[0049] Figure 2 schematically shows a test specimen set on a tensile testing machine to measure the joint strength of a diffusion joint. The left figure is a front view, and the right figure is a side view. The diffusion joint 2 is located in the overlapping portion of plate samples 1a and 1b. The end of plate sample 1a is restrained in the upper chuck 3a of the tensile testing machine, and the end of plate sample 1b is restrained in the lower chuck 3b, and a tensile load is applied in the direction of the arrows shown in the figure. The ends of plate samples 1a and 1b that are not held in the chucks are bent to the opposite side from the mating plate sample in a manner that does not apply stress to the diffusion joint so as not to interfere with the chucks or other fixtures. In the figure, the thickness of plate samples 1a and 1b is exaggerated.

[0050] (Drop test of diffusion bonding test specimen) For reference, a drop test of diffusion bonding test specimens was conducted according to the method described in paragraph 0057 of Patent Document 1 to evaluate the diffusion bonding properties. Specifically, the following was performed. Two 15mm x 15mm plates cut from the test material were stacked and fixed in a jig. They were then placed in a tubular furnace under a stress of 0.9 MPa, held at 800°C in a nitrogen atmosphere for 1 hour, and then air-cooled to obtain a test specimen in which the two plates were integrated by diffusion bonding. The obtained test specimens were subjected to a drop test in which they were freely dropped 100 times from a height of 30 cm onto asphalt at an unspecified angle. If delamination occurred at the joint between the plates during the drop test, the drop test was stopped at that point. After the drop test, the end faces of the test specimens were observed with an optical microscope to check whether gaps had formed at the joints between adjacent plates. This test was performed with n=3 specimens. As a result, specimens in which no delamination occurred and no gaps were formed at the joints between the plates were evaluated as ○ (diffusion bonding; good), and all other cases were evaluated as × (diffusion bonding; poor).

[0051] (0.2% yield strength after high-temperature holding) Samples cut from each test material were heat-treated by holding them at 800°C in a nitrogen atmosphere for 1 hour, followed by air cooling, to obtain "high-temperature held samples." Tensile test specimens (JIS No. 5) were taken from the high-temperature held samples in the direction parallel to the rolling process, and tensile tests were performed in accordance with JIS Z2241 for n=3 tests to measure the 0.2% yield strength. The average value of n=3 was taken as the performance value for the test material. The results are shown in Tables 1 to 4.

[0052] (Electrical conductivity after high-temperature holding) Samples cut from each test material were heat-treated by holding them at 800°C in a nitrogen atmosphere for 1 hour, followed by air cooling, to obtain "high-temperature held samples." The conductivity of the high-temperature held samples was measured using an eddy current conductivity meter (SigmaCheck, manufactured by Nippon Matec Co., Ltd.) with the probe frequency set to 480 kHz. Calibration before measurement was performed using standard test pieces of copper (100.62% IACS) and cupronickel (8.644% IACS). Conductivity measurements were performed for n=3 tests, and the average value of n=3 was taken as the performance value for the test material in question.

[0053] [Table 1]

[0054] [Table 2]

[0055] [Table 3]

[0056] [Table 4]

[0057] In the copper alloy sheets of the examples in which the chemical composition and manufacturing conditions of the sheets were controlled to the appropriate range described above, a high 0.2% yield strength of 400 MPa or more was maintained after high-temperature holding. Furthermore, all of the sheets obtained in the examples had sufficiently small maximum surface height roughness Rz and unfolded area ratio Sdr, resulting in very high bonding strength at the diffusion bond. These sheets had a sufficiently small thickness of the oxygen-enriched layer on the surface and possessed the property of sufficiently forming a titanium-enriched layer after high-temperature holding.

[0058] In contrast, comparative example No. 41 had too little Ti content, resulting in a low strength level (0.2% yield strength) after high-temperature holding. Furthermore, it lacked the ability to sufficiently form a titanium-enriched layer after high-temperature holding; although it received a passing grade in the drop test, the bonding strength of the diffusion bond was low. In No. 42, the Ti content was too high, causing cracks in the material during hot rolling, and preventing further processing. In samples No. 43 and 44, a standard work roll was used during the finishing cold rolling process, where the Rz value in the roll axis direction was not strictly controlled to a small value. As a result, it was not possible to obtain sheet metal with a sufficiently small Rz value on the sheet surface. Although the drop test received a positive rating, the bonding strength of the diffusion joint was low. In No. 45, the rolling ratio during the finishing cold rolling was too high, so the Sdr ratio of the sheet material could not be sufficiently reduced. As a result, although the drop test received a "○" rating, the bonding strength of the diffusion joint was low. Case No. 46 is an example of applying a known manufacturing process that includes multiple solution treatments. In this case, a work roll controlled to Rz as defined in the present invention was used in the finish cold rolling, but the rolling rate was too high, so the unfolded area ratio Sdr of the sheet material could not be sufficiently reduced, and although the drop test was rated as ○, the bonding strength of the diffusion joint was low. In this example, the finish heat treatment was carried out under the condition of heating and holding for 3 hours in a batch-type annealing furnace, so a fairly thick oxygen-enriched layer was formed on the resulting sheet material. In No. 46, the bonding strength of the diffusion joint was further reduced compared to No. 45, so it is considered preferable to reduce the thickness of the oxygen-enriched layer to improve the bonding strength at the diffusion joint.

[0059] Examples No. 47 and 49 are cases where a copper alloy without Ti (Corson-type copper alloy) was used. In this case, the strength level (0.2% yield strength) after high-temperature holding was low, and the diffusion bonding properties were evaluated as "fail" in the drop test, resulting in considerably low bonding strength. Case No. 48 is an example using commercially available pure copper material (C1020). Pure copper is considered to have good diffusion bonding properties among copper-based materials, and a bonding strength of 72 MPa was obtained in the diffusion bonded section of this example. However, the strength level (0.2% yield strength) after high-temperature holding was significantly lower than that of other examples (Cu-Ti copper alloys and Corson copper alloys). Case No. 49 is an example of applying a known manufacturing process that includes intermediate annealing and intermediate cold rolling between rough cold rolling and solution treatment. In the finish cold rolling, a normal work roll was used, where the Rz in the roll axis direction was not strictly controlled to a small value. In this case, it was not possible to obtain a plate material with a sufficiently small Rz on the plate surface, and although the drop test received a "○" rating, the bonding strength of the diffusion joint was low. [Explanation of Symbols]

[0060] 1a, 1b Plate material samples 2 Diffusion junction 3a Top zipper 3b Lower zipper

Claims

1. In mass%, Ti: 2.00 to 5.00%, Ag: 0 to 0.30%, Al: 0 to 3.00%, B: 0 to 0.30%, Be: 0 to 0.15%, Co: 0 to 1.00%, Cr: 0 to 1.00%, Fe: 0 to 1.00%, Hf: 0 to 1.00%, Mg: 0 ~1.00%, Mn: 0-1.50%, Mo: 0-1.00%, Nb: 0-0.50%, Ni: 0-1.50%, P: 0-0.20%, S: 0-0.20%, Si: 0-1.00%, Sn: 0-1.50%, Ta: 0-1.00%, V: 0-1.0 A copper alloy sheet material having a chemical composition of 0%, Zn: 0-2.00%, Zr: 0-1.00%, total rare earth elements: 0-3.00%, with a total of Ag, Al, B, Be, Co, Cr, Fe, Hf, Mg, Mn, Mo, Nb, Ni, P, S, Si, Sn, Ta, V, Zn, Zr and rare earth elements of 4.00% or less, with the remainder being Cu and unavoidable impurities, a maximum height roughness Rz of the sheet surface in the direction perpendicular to rolling of the sheet surface of 1.5 μm or less, and a sheet surface development area ratio Sdr measured by a laser microscope of 0.10 or less.

2. In the elemental concentration profiles of Cu, Ti, O, and C measured by XPS (X-ray photoelectron spectroscopy), the proportion of O in the four elements from the outermost surface is 5.0 atomic percent or less. ２ The copper alloy plate material according to claim 1, wherein when the surface region up to the equivalent depth (nm) is called the oxygen-enriched layer, the thickness of the oxygen-enriched layer is 100 nm or less.

3. The copper alloy sheet material according to claim 1, wherein the 0.2% yield strength in the rolling direction after being subjected to a heat treatment test in which it is held at 800°C for 1 hour in a nitrogen atmosphere is 400 MPa or more.

4. The copper alloy plate material according to claim 1, wherein the plate thickness is 0.01 to 0.50 mm.

5. The copper alloy sheet material according to claim 1, wherein the Ti content in the chemical composition is 2.80 to 5.00%, and the developed area ratio Sdr is 0.08 or less.

6. The copper alloy sheet material according to claim 1, wherein the Ti content in the chemical composition is 2.80 to 5.00%, the maximum height roughness Rz is 1.1 μm or less, and the developed area ratio Sdr is 0.06 or less.

7. A copper alloy plate material according to claim 1, for use in a vapor chamber housing.

8. When manufacturing copper alloy sheets by subjecting intermediate product sheets to solution treatment, aging treatment, finish cold rolling, and finish heat treatment in the order described above, The aforementioned finish cold rolling is performed using a work roll having a roll surface with a maximum height roughness Rz in the roll axis direction of 1.7 μm or less, under conditions of a rolling rate of 5.0 to 20.0%. The aforementioned finishing heat treatment is performed under conditions of holding the temperature at 300 to 500°C for 10 to 300 seconds. A method for manufacturing a copper alloy sheet material according to claim 1.

9. A vapor chamber having a housing structure in which two or more members made of copper alloy plate material according to any one of claims 1 to 7 are joined by diffusion bonding or brazing.

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