Aluminum alloy rolled material and its manufacturing method

Abstract

To provide a rolled aluminum alloy material with excellent thermal conductivity and a low coefficient of thermal expansion.SOLUTION: A rolled aluminum alloy material comprises Si: 13.5-17.4 mass%, Fe: 0.1-0.5 mass%, Cu: 0.005-0.3 mass%, Mn: 0.005-0.3 mass%, Mg: 0.001-0.24 mass%, Zn: 0.002-0.1 mass%, Ti: 0.01-0.2 mass%, Ga: 0.01-0.5 mass%, and Sr: 0.008-0.05 mass%, satisfying the condition of (Si-12.5) / (Fe+2.2Mg)≥1.9, with the balance being Al and unavoidable impurities.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a rolled aluminum alloy material suitable for use in metal base substrates on which heat generating elements such as circuit boards and power modules are mounted, and to a method for producing the same. [Background technology]

[0002] In recent years, with the rapid development of electronic components and circuits in response to the increasing electrification of automobiles and the need for high efficiency in various power supply circuits, metal-based printed circuit boards have come to be widely used in circuits that incorporate semiconductor elements, particularly power semiconductors (power devices), and light-emitting diodes (LEDs), which serve as light sources for various lighting fixtures and automobile headlamps and rear lamps.

[0003] The standard structure of metal-based printed circuit boards used for such purposes is to layer an insulating layer on top of metal, and then laminate copper foil, which is the conductor that makes up the circuit, on top of that.

[0004] In particular, in recent years, demand has been increasing for metal-based printed circuit boards for lighting applications that incorporate LED elements, as they can extend the lifespan of the LEDs by dissipating the heat generated by the LEDs.

[0005] Metal-based printed circuit boards are also known to offer benefits beyond LED-mounted lighting applications, such as stabilizing the performance of power semiconductor elements and protecting other electronic components from heat damage by reducing the board temperature.

[0006] Copper or aluminum is used as the base metal. Among these, aluminum alloys have been increasingly studied for the purpose of weight reduction. However, when aluminum is used as the base substrate, there are issues such as board warping due to the difference in thermal expansion coefficient between the aluminum and the copper foil that constitutes the circuit, which sandwiches the insulating layer, breakage of the copper foil in the circuit due to thermal cycling, and cracks occurring in the solder joints that join the copper foil and the element. In particular, solving these issues has become more important in recent years due to the increasing density of electronic components, which has led to more detailed circuits, and the existence of areas that are subject to extreme thermal cycles due to the increase in high-heat components.

[0007] For these applications, pure aluminum alloys such as JIS 1100, 1050, and 1070 offer excellent thermal conductivity, but their large difference in thermal expansion coefficient with copper and low strength can lead to warping. On the other hand, Al-Mg alloys (5000 series alloys) such as JIS 5052, known for their high strength, offer high strength but are disadvantageous in terms of the potential for cracking in solder joints due to their large difference in thermal expansion coefficient with the copper foil that makes up the circuit. Furthermore, their thermal conductivity is lower than that of pure aluminum, resulting in poor heat dissipation. While attempts have been made to reduce the difference in thermal expansion coefficient with copper foil using Al-Si alloys (4000 series alloys), these alloys do not fully address the above issues, nor do they necessarily offer satisfactory drill and router processability during printed circuit board manufacturing.

[0008] For example, Patent Document 1 discloses an Al-based printed wiring board characterized in that the Al-based alloy substrate contains 3 to 20% Si, and further contains one or more of 0.05 to 2.0% Fe, 0.05 to 2.0% Mg, 0.05 to 6.0% Cu, 0.05 to 2.0% Mn, 0.05 to 3.0% Ni, 0.05 to 0.3% Cr, 0.05 to 0.3% V, 0.05 to 0.3% Zr, and more than 1.0% but not more than 7.0% Zn, with the remainder being Al and impurities. The substrate contains eutectic Si particles with an average particle size of 5 μm or less or primary crystal Si particles with a maximum particle size of 15 μm or less dispersed in at least the surface layer, and an anodized film with a thickness of 5 μm or more is formed on both sides of the substrate.

[0009] Patent Documents 2 and 3 disclose a clad material and a printed wiring board having a low thermal expansion coefficient and excellent processability, the core material of which is a double-sided clad material containing 5 to 30 mass% Si, with the remainder being Al and impurities, and further containing 1 mass% or less Fe, 1 mass% or less Ni, 0.5 mass% or less Cu, 0.3 mass% or less Ti, 0.3 mass% or less Cr, 0.1 mass% or less P, 0.05 mass% or less B, 0.2 mass% or less Mn, 0.2 mass% or less Mg, and 0.2 mass% or less Zn.

[0010] Patent Document 4 discloses a printed wiring board for a printed circuit board that is anodized in a phosphoric acid electrolytic bath and uses an Al-Mg alloy (5052 alloy) or an Al-Mg-Si alloy, and a method for manufacturing the same.

[0011] Patent Document 5 discloses an aluminum alloy containing 0.05 to 1.0 wt % Mn, 3.5 to 5.6 wt % Mg, and 0.05 to 0.25 wt % Cr in an aluminum-based circuit board formed from a high heat-resistant resin having a molding temperature in a temperature range exceeding 250°C. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] Japanese Patent Application Publication No. 6-41667 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-328530 [Patent Document 3] Japanese Patent Application Laid-Open No. 2007-302939 [Patent Document 4] Japanese Patent Application Laid-Open No. 2006-24906 [Patent Document 5] Japanese Patent Application Laid-Open No. 2015-88612 Summary of the Invention [Problem to be solved by the invention]

[0013] However, in Patent Document 1, an Al-Si alloy with a low thermal expansion coefficient is selected, and the size and dispersion of eutectic Si particles and primary crystal Si particles are examined, and the anodized film is improved to improve surface adhesion with the insulating adhesive layer, but machinability in drilling and routering is not examined.

[0014] Patent Document 2 attempts to solve the problem of surface adhesion that is an issue in Patent Document 1 by using double-sided cladding, and uses pure aluminum or Al-Mn alloys as the aluminum alloy for the skin material, but the inclusion of a cladding process makes the process complicated and is disadvantageous in terms of manufacturing costs.

[0015] Like Patent Document 2, Patent Document 3 attempts to solve the problem of surface adhesion by double-sided cladding, and aims to increase the surface hardness in addition to adhesion by using an Al-Mg-Si system for the aluminum alloy that forms the skin material. However, as it also includes a cladding process, the process is complicated and it is disadvantageous in terms of manufacturing costs.

[0016] Patent Document 4 examines in detail how to improve the properties of anodized films, aiming to obtain stable adhesion to resin insulating materials and improve the adhesion. However, the aluminum substrate is an Al-Mg system (5000 system) or an Al-Mg-Si system (6000 system), and the problem of the difference in thermal expansion coefficient with copper foil remains unresolved.

[0017] Patent Document 5 discloses that a highly heat-resistant insulating layer is laminated with high-strength aluminum having an annealing temperature higher than its heat resistance temperature to prevent a decrease in flatness due to softening of the aluminum and to ensure heat resistance in high-temperature environments for applications such as power modules. However, this does not solve the problem of the difference in thermal expansion coefficient with copper foil.

[0018] As described above, it is extremely difficult with conventional technology to obtain an aluminum alloy plate that has the thermal expansion difference with copper foil, heat dissipation properties, surface adhesion, and machinability that are issues with aluminum-based substrates.

[0019] In view of the above-mentioned technical background, an object of the present invention is to provide a rolled aluminum alloy material having a low thermal expansion coefficient and high thermal conductivity, and a method for producing the same. [Means for solving the problem]

[0020] As a result of extensive research, the present inventors have discovered that by examining the composition of rolled aluminum material and the manufacturing process, it is possible to obtain an aluminum alloy rolled material that has excellent heat dissipation properties while reducing the possibility of board warping due to differences in thermal expansion coefficients with the copper foil that constitutes the circuit, breakage of the copper foil in the circuit due to thermal cycling, and cracks in the solder joints that join the copper foil to the elements, and that ensures machinability in drill and router processing. This finding led to the present invention. Specifically, the present invention has the following configurations (1) to (11). (1) A rolled aluminum alloy material having a chemical composition containing 13.5 to 17.4 mass% Si, 0.1 to 0.5 mass% Fe, 0.005 to 0.3 mass% Cu, 0.005 to 0.3 mass% Mn, 0.001 to 0.24 mass% Mg, 0.002 to 0.1 mass% Zn, 0.01 to 0.2 mass% Ti, 0.01 to 0.5 mass% Ga, and 0.008 to 0.05 mass% Sr, and further satisfying the condition (Si - 12.5) / (Fe + 2.2Mg) ≥ 1.9, with the remainder being Al and unavoidable impurities. (2) The rolled aluminum alloy material according to (1) above, further comprising at least one of Na: 0.0005 to 0.02 mass % and Ca: 0.0005 to 0.02 mass %. (3) The rolled aluminum alloy material according to (1) or (2) above, wherein the P content is further restricted to 0.005% by mass or less. (4) The rolled aluminum alloy material according to any one of (1) to (3) above, further comprising: 0.001 to 0.5 mass% Ni, 0.001 to 0.1 mass% Cr, 0.001 to 0.03 mass% V, 0.0002 to 0.02 mass% B, and 0.0002 to 0.03 mass% Zr. (5) The rolled aluminum alloy material according to any one of (1) to (4) above, further containing one or more of Pb: 0.01 to 0.3 mass% and Sn: 0.01 to 0.3 mass%, and one or more of Na: 0.0005 to 0.015 mass% and Ca: 0.0005 to 0.015 mass%, with P being restricted to 0.003 mass% or less, In being 0.004 mass% or less, Bi being 0.01 mass% or less, and Sb being 0.01 mass% or less. (6) The rolled aluminum alloy material according to any one of (1) to (5) above, characterized by containing 14.2 to 16.8 mass% Si, 0.12 to 0.4 mass% Fe, 0.01 to 0.25 mass% Cu, 0.06 to 0.25 mass% Mn, 0.06 to 0.2 mass% Mg, 0.01 to 0.08 mass% Zn, 0.03 to 0.15 mass% Ti, 0.05 to 0.3 mass% Ga, and 0.01 to 0.04 mass% Sr. (7) A rolled aluminum alloy material according to any one of (1) to (6) above, which satisfies the condition Mn / Fe≧0.2. (8) The rolled aluminum alloy material according to any one of (1) to (7) above, wherein, when a cross section of the plate thickness parallel to the rolling direction is polished and observed, second-phase particles having a size of 20 μm or more in the long side direction account for 20% or less of the observed area. (9) A method for producing an aluminum alloy rolled material, comprising the steps of: before or after subsequent facing of an aluminum alloy ingot having a composition specified in the aluminum alloy rolled material according to any one of (1) to (8) above, performing a homogenization treatment at a temperature of 470°C or higher and 540°C or lower for 1 hour or longer and 20 hours or shorter, holding the ingot at a temperature of 450°C or higher and 540°C or lower for 0.5 hours or longer and 10 hours or longer, and then starting hot rolling; performing hot rolling with a rolling reduction of 95% or higher and 99.5% or lower through multiple rolling passes; and then cold rolling of 30% or higher and 98.5% or lower. (10) A method for producing an aluminum alloy rolled material according to (9) above, characterized in that it comprises a heat treatment step of holding the material at 260°C or higher and 400°C or lower for 0.5 hours or longer and 10 hours or shorter at least once before or after any pass from the start to the end of the cold rolling step. (11) A method for producing a rolled aluminum alloy material according to (10) above, characterized in that it comprises, at least once after the cold rolling step, a heat treatment step of holding the material at 150°C or higher and 240°C or lower for 1 hour or longer and 20 hours or shorter. [Effects of the Invention]

[0021] The rolled aluminum alloy material described in (1) above has a low thermal expansion coefficient, high thermal conductivity, and excellent hot workability due to its chemical composition and satisfying the compositional relationship between Si, Fe, and Mg.

[0022] According to the rolled aluminum alloy material described in (2) and (3) above, it is possible to further suppress the coarsening of crystallized substances (second-phase particles) and obtain the effect of improving hot workability.

[0023] According to the rolled aluminum alloy material described in (4) above, it is possible to obtain a lower thermal expansion coefficient while suppressing the decrease in thermal conductivity.

[0024] The rolled aluminum alloy material described in (5) above has improved drill and router workability.

[0025] The rolled aluminum alloy material described in (6) above can further have both a low thermal expansion coefficient and high thermal conductivity.

[0026] According to the rolled aluminum alloy material described in (7) and (8) above, the hot workability and drilling workability are further improved.

[0027] According to the method for producing a rolled aluminum alloy material described in (9) above, it is possible to produce a rolled aluminum alloy material that has both a low thermal expansion coefficient and high thermal conductivity.

[0028] According to the method for producing a rolled aluminum alloy material described in (10) above, it is possible to improve the mechanical properties of the rolled aluminum alloy material and also improve the thermal conductivity thereof.

[0029] According to the method for producing a rolled aluminum alloy material described above in (11), the mechanical properties of the rolled aluminum alloy material, particularly the elongation, can be improved, and residual strain can be eliminated to suppress the occurrence of warpage. DETAILED DESCRIPTION OF THE INVENTION

[0030] The rolled aluminum alloy material of the present invention has a specified alloy chemical composition. [Chemical composition of rolled aluminum alloy material] (Si, Fe, Cu, Mn, Mg, Zn, Ti, Ga, Sr) Aluminum alloy rolled material contains the essential elements Si, Fe, Cu, Mn, Mg, Zn, Ti, Ga, and Sr. The purpose and content of each element are as follows. The remainder is Al and unavoidable impurities.

[0031] Silicon is an element necessary to lower the thermal expansion coefficient of aluminum alloys. The higher the Si content, the lower the thermal expansion coefficient. In the present invention, the Si content is set to 13.5 to 17.4 mass%. If the Si content is less than 13.5 mass%, the desired low thermal expansion coefficient cannot be obtained. On the other hand, if the Si content exceeds 17.4 mass%, an even lower thermal expansion coefficient can be obtained, but the amount of primary Si crystallized during melting and casting at a eutectic composition of Al-12.6 mass% Si or higher increases, reducing rollability during hot rolling and making drilling and routering difficult during substrate processing. A more preferable lower limit of the Si content is 14.2 mass% and an upper limit is 16.8 mass%, and an even more preferable lower limit is 14.5 mass% and an upper limit is 16.5 mass%. Fe is an element that is effective in lowering the thermal expansion coefficient of the alloy, and is also effective in improving strength and heat resistance. However, it is also known to form Al-Fe-Si intermetallic compounds, and if the content is particularly high, these become coarse crystals during melting and casting, reducing workability and promoting the occurrence of edge cracks during hot rolling and cold rolling. Therefore, the Fe content is set to 0.1 to 0.5 mass%. It is more preferably 0.12 to 0.4 mass%, and even more preferably 0.15 to 0.30 mass%.

[0032] Mg is an element that contributes to improving strength by dissolving in aluminum, but at the same time, it can also reduce thermal conductivity after product processing, potentially reducing heat dissipation. It is also well known that Mg forms Mg-Si intermetallic compounds with Si. High Mg content, in particular, results in coarse crystals during melting and casting, reducing workability and promoting edge cracking during hot and cold rolling. Therefore, the Mg content is limited to 0.001 to 0.24% by mass. It is more preferably 0.06 to 0.20% by mass, and even more preferably 0.08 to 0.18% by mass.

[0033] Cu is an element effective in improving strength and is expected to reduce the thermal expansion coefficient, but a high content reduces corrosion resistance. Furthermore, a large content significantly reduces workability during hot rolling and reduces thermal conductivity during product processing, adversely affecting heat dissipation. Therefore, the Cu content is limited to 0.005 to 0.3 mass%. A range of 0.01 to 0.25 mass% is more preferable, and a range of 0.05 to 0.18 mass% is even more preferable.

[0034] Mn is an alloying element that is generally added to refine recrystallized grains. It also has the effect of agglomerating Al-Fe-Si acicular intermetallic compounds and improving toughness, but adding more than necessary can lead to a decrease in thermal conductivity. Therefore, the Mn content is set to 0.005 to 0.3 mass%, more preferably 0.06 to 0.25 mass%, and even more preferably 0.08 to 0.2 mass%.

[0035] Zn is known to be effective in improving strength when used together with Mg, but a high Zn content reduces the corrosion resistance of the alloy material and increases the thermal expansion coefficient of aluminum. Therefore, the Zn content is set to 0.002 to 0.1 mass%, preferably 0.01 to 0.08 mass%, and even more preferably 0.03 to 0.06 mass%.

[0036] Ti has the effect of refining crystal grains when casting an alloy. However, if it is contained in a large amount, many large crystals are formed, which reduces the workability and thermal conductivity of the product. Therefore, the Ti content is set to 0.01 to 0.2 mass%, more preferably 0.03 to 0.15 mass%, and even more preferably 0.06 to 0.12 mass%.

[0037] Ga is an element that easily segregates at grain boundaries and crystallized particle interfaces, making it effective for improving the drill and router machinability of hard-to-cut materials containing hard particles. However, excessive Ga content can cause surface cracking during hot rolling and cold rolling, significantly reducing machinability, and also reduces thermal conductivity after product processing, adversely affecting heat dissipation. Therefore, the Ga content is set to 0.01 to 0.5 mass%. A range of 0.05 to 0.3 mass% is more preferable, and a range of 0.08 to 0.25 mass% is even more preferable.

[0038] Sr is an element that is effective in refining eutectic Si particles. However, if it is contained in large amounts, it will induce the generation of porosity during melting and casting. Therefore, the Sr content is set to 0.008 to 0.05 mass%, more preferably 0.01 to 0.04 mass%, and even more preferably 0.015 to 0.03 mass%. (Na, Ca) Aluminum alloy rolled materials may optionally contain one or more of Na and Ca. These elements primarily affect the intermetallic compounds that crystallize from the molten aluminum alloy during casting. The significance of adding or controlling each element, and the content, are as follows:

[0039] Na is an element that is effective in refining eutectic Si particles. However, its effect is weaker than that of Sr, and it only has a supplementary effect. Furthermore, if added in large amounts, it induces the generation of porosity during melting and casting, just like Sr, so adding more than the necessary amount is not preferable. Therefore, in the present invention, the addition of Sr is prioritized, but the Na content may be up to 0.0005 to 0.02 mass%. A range of 0.0005 to 0.015 mass% is more preferable, and a range of 0.0005 to 0.01 mass% is even more preferable.

[0040] Ca is an element that is effective in refining eutectic Si particles. However, its effect is weaker than that of Sr, and it only has a supplementary effect. Furthermore, if added in large amounts, it induces the generation of porosity during melting and casting, just like Sr, so adding more than the necessary amount is not preferable. Therefore, in the present invention, the addition of Sr is prioritized, but the Ca content may be up to 0.0005 to 0.02 mass%. A range of 0.0005 to 0.015 mass% is more preferable, and a range of 0.0005 to 0.01 mass% is even more preferable. (P) In the case of rolled aluminum alloys, the P content is further restricted in the presence of the above-mentioned Sr and / or Na and / or Ca. P is well known as an element effective in refining primary silicon, but its coexistence with Sr and / or Na and / or Ca significantly reduces this effect. Therefore, the P content is limited to 0.005% by mass or less. It is more preferably 0.003% by mass or less, and even more preferably 0.002% by mass or less. (Ni) The rolled aluminum alloy material may further contain Ni, if necessary. Ni is an element effective in lowering the thermal expansion coefficient of the alloy and is also effective in improving strength. It also has the effect of improving heat resistance, but if the Ni content is too high, it forms an intermetallic compound with Al, which reduces workability and makes hot rolling and cold rolling difficult. Therefore, the Ni content is set to 0.001 to 0.5 mass%, preferably 0.02 to 0.35 mass%, and even more preferably 0.06 to 0.20 mass%. (Cr, V, B, Zr) The rolled aluminum alloy material may further contain Cr, V, B, and Zr as needed. These elements mainly affect the refinement of crystal grains and are effective in improving mechanical properties.

[0041] Cr is an element that is effective in improving strength and refining crystal grains. However, if it is contained in a large amount, workability during hot rolling decreases and thermal conductivity after product processing decreases, adversely affecting heat dissipation. Therefore, the Cr content is set to 0.001 to 0.1 mass%, more preferably 0.002 to 0.08 mass%, and even more preferably 0.004 to 0.05 mass%.

[0042] V is an element that is effective in improving strength and refining crystal grains. However, if it is contained in large amounts, workability during hot rolling decreases and thermal conductivity after product processing decreases significantly, adversely affecting heat dissipation. Therefore, the V content range is set to 0.001 to 0.03 mass%, more preferably 0.002 to 0.02 mass%, and even more preferably 0.004 to 0.01 mass%.

[0043] Zr is an element effective in improving strength and refining crystal grains. However, if it is contained in large amounts, workability during hot rolling decreases and thermal conductivity after product processing decreases significantly, adversely affecting heat dissipation. Therefore, the Zr content is set to 0.0002 to 0.03 mass%, more preferably 0.005 to 0.02 mass%, and even more preferably 0.008 to 0.015 mass%.

[0044] B has the effect of refining crystal grains when casting an alloy. However, if it is contained in a large amount, a large amount of hard crystallized material is formed, significantly reducing the machinability of the product. Therefore, the B content is set to 0.0002 to 0.02 mass%, more preferably 0.001 to 0.015 mass%, and even more preferably 0.002 to 0.01 mass%. (Pb, Sn) The rolled aluminum alloy material may further contain one or more of Pb and Sn, if necessary.

[0045] Pb and Sn have extremely low solid solubility limits in aluminum, tend to segregate at grain boundaries and crystallized particle interfaces, and have lower melting points than Al. These elements are effective in improving the drilling and routering properties of hard-to-cut materials containing hard particles. The above effect is common to both Pb and Sn, and can be achieved by adding at least one of them. Of course, two elements can also be added. However, adding too much of these elements can cause surface cracks and edge cracks at the widthwise edges of the sheet during hot rolling and cold rolling, reducing workability. Therefore, the Pb and Sn contents should be 0.01 to 0.3 mass%. A range of 0.03 to 0.2 mass% is preferable, with a range of 0.05 to 0.1 mass% being even more preferable. (Sb, Bi, In) In the rolled aluminum alloy material, Sb, Bi, and In are further restricted in addition to the above-mentioned Sr, Pb, and Sn.

[0046] Sb and Bi, when present together with Pb and Sn, are effective elements for improving the drilling and routering properties of hard-to-cut materials containing hard particles. However, they also inhibit the refinement effect of Sr. Therefore, in this invention, the refinement effect of Sr is prioritized, and the Sb and Bi contents are set to 0.01 mass% or less. 0.008 mass% or less is more preferable, and 0.005 mass% or less is even more preferable.

[0047] Indium (In) significantly reduces corrosion resistance, so a small amount is preferable. The content of In as an unavoidable impurity is preferably 0.004 mass% or less, more preferably 0.003 mass% or less, and even more preferably 0.002 mass% or less. (Si, Fe, Mg amounts and their ratios) In the rolled aluminum alloy material of the present invention, there is an optimum amount of Fe and Mg relative to the Si content. This is due to the interaction between the Al-Fe-Si and Mg-Si intermetallic compounds and the crystallization of the eutectic Si phase in the Al-Si alloy. As a result of extensive research, the inventors have found that these optimum values ​​have the relationship (Si - 12.5) / (Fe + 2.2Mg) ≥ 1.9 by mass. In other words, by setting the Si, Fe, and Mg contents within the above-mentioned ranges within the composition ranges of each element, it is possible to suppress surface cracks and edge cracks at the widthwise edges of the sheet during hot rolling and cold rolling. (Mn / Fe ratio) The aluminum alloy of the present invention forms an Al-Fe-Si intermetallic compound during melting and casting. This intermetallic compound is prone to acicular formation when the Fe content is high, which adversely affects the occurrence of surface cracks during hot rolling and cold rolling, as well as edge cracks at the widthwise edges of the sheet. After extensive research, the inventors discovered that the optimal threshold for the Mn / Fe ratio is Mn / Fe≧0.2. That is, by setting the Mn / Fe ratio to the above value in the Fe content of the present invention, the Al-Fe-Si intermetallic compound is agglomerated, further preventing a decrease in toughness due to this intermetallic compound. (crystal size and its area occupancy) In the aluminum alloy of the present invention, primary crystal Si and Al-Fe-Si intermetallic compounds crystallized as second-phase particles significantly impair hot rolling, cold rolling, and drilling workability during processing of metal base substrates when the size increases. Therefore, it is desirable that the area occupancy of second-phase particles with a size of 20 μm or more in the long side direction, as observed by polishing a thickness cross-section parallel to the rolling direction in the final rolled sheet, is 20% or less. This can be expected to further improve hot workability and drilling workability. An area occupancy of 15% or less is more preferable, and an area occupancy of 10% or less is even more preferable. (Method of manufacturing rolled aluminum alloy material) The above-mentioned rolled aluminum alloy material of the present invention, i.e., a rolled material having the desired thermal expansion coefficient α and thermal conductivity λ, can be obtained, for example, by carrying out a predetermined heat treatment and carrying out hot rolling and cold rolling under predetermined conditions in the process of producing a rolled material from an aluminum alloy ingot of a predetermined composition. Each of these processes will be described in detail below. (aluminum alloy ingot) The dissolved components are adjusted by a conventional method to obtain an aluminum alloy ingot (hereinafter referred to as a slab). (Homogenization process) The homogenization treatment is carried out to make the concentration of elements dissolved in the aluminum alloy slab uniform, but since eutectic melting occurs if the treatment temperature is too high, it is preferably carried out at 470°C to 540°C, and more preferably at 480°C to 520°C. The treatment time (holding time) is preferably 1 hour to 20 hours, and more preferably 2 hours to 15 hours.

[0048] Generally, when an aluminum alloy slab is rolled, facing is performed to remove an impurity layer near the rolled surface of the slab. The homogenization treatment described above may be performed either before or after facing. (heating process before hot rolling) The aluminum alloy slab is preheated before being subjected to hot rolling. The preheating is carried out by holding the aluminum alloy slab at 450°C to 540°C for 0.5 to 10 hours. More preferred conditions are 470°C to 520°C for 1 to 8 hours.

[0049] Since the treatment conditions of the homogenization treatment step and the treatment conditions of the pre-hot rolling heating step partially overlap, a single treatment can be carried out under the overlapping conditions, and this treatment can serve as both the homogenization treatment and the pre-hot rolling heating. (Hot rolling process) The aluminum alloy slab that has been heated before hot rolling is hot rolled in multiple passes. Hot rolling generally homogenizes the ingot structure and disperses the crystallized particles that crystallized as second-phase particles during casting. This process is also necessary to produce a plate material with a uniform thickness that can be cold rolled in a relatively short time. The total reduction rate of the hot rolling is preferably 95% to 99.5%, and more preferably 96% to 99.5%.

[0050] The hot rolling is composed of rough hot rolling and finish hot rolling, and after rough hot rolling consisting of a plurality of passes is performed using a rough hot rolling mill, finish hot rolling is performed using a finish hot rolling mill different from the rough hot rolling mill. In the present invention, if the final pass in the rough hot rolling mill is the final pass of the hot rolling, the finish hot rolling can be omitted.

[0051] When cold rolling, which will be described later, is performed on a coil, the aluminum alloy rolled material after finish hot rolling may be wound on a winding device to form a hot-rolled coil. When finish hot rolling is omitted and the final pass of rough hot rolling is used as the final pass of hot rolling, the aluminum alloy rolled material after rough hot rolling may be wound on a winding device to form a hot-rolled coil.

[0052] In hot rough rolling, by controlling the target thickness configuration for each pass of hot rough rolling and the temperature by controlling the amount of coolant, the roll rotation speed, and cooling between passes, it is possible to obtain an aluminum alloy rolled material that has a predetermined sheet crown and is free from cracks at the end of the rolling width (hereinafter referred to as edge cracks) and rolling surface defects that are relatively likely to occur in difficult-to-process materials.

[0053] The inter-pass cooling of the rough hot rolling may be carried out sequentially on the rolled portions while rolling the aluminum alloy rolled material, or may be carried out after rolling the entire aluminum alloy rolled material. The cooling method is not limited, and may be water cooling, air cooling, or the use of a coolant.

[0054] In the present invention, when finish rolling is not performed after the final pass of rough hot rolling, the surface temperature of the aluminum alloy rolled material immediately after the final pass of hot rolling is defined as the hot rolling end temperature, and when finish rolling is performed after the final pass of rough hot rolling, the surface temperature of the aluminum alloy rolled material immediately before finish rolling is defined as the hot rolling end temperature.

[0055] The hot rolling end temperature is preferably 280°C or higher. By setting the hot rolling end temperature to 280°C or higher, edge cracks due to a temperature drop during rolling can be suppressed. When coiling is performed after hot rolling to perform the subsequent cold rolling on the coil, if the temperature is too low, edge cracks at the widthwise ends of the sheet are likely to develop depending on the coiling tension. Therefore, when coiling is performed without finish hot rolling, the surface temperature of the aluminum alloy sheet at the end of the final pass of rough hot rolling is preferably 280°C or higher as described above. However, when hot finish rolling is performed after rough hot rolling, the surface temperature of the aluminum alloy sheet after hot finish rolling is preferably 260°C or higher to prevent edge cracks at the widthwise ends of the sheet. (Cold rolling process) After hot rolling, the rolled aluminum alloy material is subjected to multiple passes of cold rolling until a predetermined thickness is obtained. Cold rolling generally improves strength through work hardening. The total reduction rate of cold rolling is preferably 30% or more to obtain a predetermined strength. The total reduction rate of the cold-rolled aluminum alloy material is more preferably 40% or more, and particularly preferably 50% or more. The upper limit of the total reduction rate is set to 98.5% or less, taking into account the reduction in elongation due to work hardening.

[0056] The method may also include a step of trimming edge cracks at the widthwise ends of the sheet before or between passes of the cold rolling step, and then proceeding with further cold rolling to prevent sheet breakage. (Heat treatment during or after the cold rolling process) It is preferable to subject the rolled material to heat treatment during and / or after the cold rolling step.

[0057] The heat treatment performed during the cold rolling process, i.e., intermediate heat treatment, is preferably performed at 260°C to 400°C for 0.5 to 10 hours, which improves mechanical properties, particularly elongation, and electrical conductivity. The intermediate heat treatment is performed before or after any pass, and may be performed for multiple passes. The heat treatment temperature is particularly preferably 280°C to 380°C, with 300°C to 370°C being even more preferred. The heat treatment time is particularly preferably 2 to 9 hours, with 3 to 8 hours being even more preferred.

[0058] The heat treatment after cold rolling, i.e., the final heat treatment, is preferably performed at 150°C to 240°C for 1 to 20 hours. The cold rolling may leave residual strain in the rolled material, causing warping of the sheet material, but the heat treatment can eliminate the residual strain. The heat treatment temperature is particularly preferably 160°C to 220°C, and the heat treatment time is particularly preferably 5 to 18 hours. Furthermore, this heat treatment is even more effective when the rolled material is placed on a flat plate and sandwiched between flat plates with weights placed on top to perform straightening (pressure annealing).

[0059] The above-described method for producing a rolled aluminum alloy material may be performed on a coil or a single sheet. Furthermore, the rolled aluminum alloy material may be cut in any step after the cold rolling step, and the steps after cutting may be performed on a single sheet, or slit into strips depending on the application. Furthermore, other steps may be added as long as they do not impair the desired properties of the rolled material. For example, the rolled aluminum alloy material after cold rolling may be washed as needed. [Example]

[0060] The present invention will be described below with reference to examples. The scope of the present invention is not limited to the examples described herein, and appropriate modifications can be made within the scope of the present invention, and all such modifications are included in the technical scope of the present invention.

[0061] First, an aluminum alloy slab having the chemical composition shown in Table 1 was cast, and the rolled surface of the obtained slab was subjected to facing processing to obtain a thickness of 250 mm, a width of 1050 mm, and a length of 1600 mm. Next, a homogenization treatment shown in Table 2 was performed in a heating furnace, and then the temperature was lowered in the same furnace, and after reaching the pre-hot rolling heating temperature shown in Table 2, the slab was held and hot rolled under the conditions shown in Table 2 to obtain a hot-rolled sheet having a hot-rolling temperature and thickness shown in Table 2. The alloy sheet after finish hot rolling was subjected to an intermediate heat treatment, cold rolling, and final heat treatment shown in Table 2 to obtain an aluminum alloy sheet having a predetermined thickness.

[0062] The rolling workability during hot rolling was evaluated by the following method. [Cracked Ear] When the sheet was wound into a coil after hot rolling, the length of the edge cracks at both ends of the sheet width was recorded from the top surface of the rolled sheet. Cracks with a maximum length of 5 mm or less were marked "○", those between 5 mm and 8 mm were marked "△", and those exceeding 8 mm were marked "×". [Area occupancy rate of second phase particles] The area occupancy of second-phase particles in the obtained alloy sheets was determined by first cutting the thickness cross section of the sheet after final heat treatment parallel to the rolling direction, fixing it in a mounting resin, and then emery-polishing and buffing it using a rotary polisher to prepare the test material. Next, five 250 × 200 μm fields were selected using a scanning electron microscope (SEM) to take composition images (COMPO images). In the COMPO image, the second-phase particles have a different contrast from the aluminum matrix, making them distinguishable by binarization. The area occupancy of second-phase particles with a longest side of 20 μm or greater in this field was calculated, and a marking of 10% or less was given: "◎," "greater than 10% but less than 20% was given: "○," and "greater than 20% was given: "×."

[0063] The tensile strength, elongation, electrical conductivity and thermal expansion coefficient of the obtained alloy sheets were evaluated by the following methods. [Tensile strength, elongation] Tensile strength (σB) and elongation (δ) were measured at room temperature by a conventional method using JIS No. 5 test pieces specified in JIS Z 2201, samples taken parallel to the rolling direction. Tensile strength of 140 MPa or more was rated as "Good", and elongation of 10% or more was rated as "Good". [Thermal Conductivity] The thermal conductivity of the obtained alloy plate was measured by a laser flash method under the following conditions. Measurement method: Laser flash method (pulse laser) ·Measurement temperature: 25℃ Sample shape: 1.5 x 10 mm diameter Atmosphere: Vacuum Thermal conductivity of 175 W / m K or more was marked "○", and that of less than 175 W / m K was marked "×". [Coefficient of thermal expansion] The linear expansion coefficient of the obtained alloy plate was measured by thermomechanical analysis (TMA) under the following conditions. Measurement method: TMA method (differential expansion method) Measurement temperature pattern: 20 to 100°C (reference temperature 20°C, heating rate: 5°C / min) Sample size: 1.5 x 3 x 18 mm Atmosphere: He gas Reference sample: Quartz The linear expansion coefficient (ΔL / L0) at each temperature was calculated from the linear expansion amount (ΔL) from 20 to 100°C (in 20°C intervals), the temperature change from 20°C (ΔT), and the length at room temperature (L0), and these were averaged to obtain the thermal expansion coefficient. The thermal expansion coefficient was 19.5 x 10 -6 / K or less is marked as "○", 19.5 × 10 -6 Those exceeding / K were marked "X".

[0064] The warpage rate was measured as an evaluation method for the warpage of the printed wiring board. The warpage rate measurement method is as follows. [Warpage rate] The evaluation of the warpage rate was carried out in accordance with the method specified in 5.22 Warpage rate and twist rate (static method) of JIS C 6481 Test Method for Copper-Clad Laminates for Printed Wiring Boards.

[0065] The test materials are Aluminum base: 1.5mm thick / Insulation layer: 100μm / Copper foil: 70μm, fully attached Cutting dimensions: 100 x 200 mm The printed wiring board was heated and held at 220°C for 120 seconds at the actual temperature of the aluminum base material side, and then cooled with a fan. The maximum height h1 of the long side at room temperature was measured, and the difference between this and the maximum height h0 measured before heating: H = h1 - h0. The difference was divided by the long side length of 200 mm to obtain the warpage rate: W = H / 200 x 100 (%). W of 1.0% or less was marked as "Good", and W of more than 1.0% was marked as "Poor".

[0066] The drilling properties of the printed wiring board were evaluated by measuring the hole position accuracy and judging the drill breakage. The drilling conditions were as follows: Drill bit: φ0.25mm carbide drill Rotational speed: 125,000 rpm Feed speed: 2.5m / min Number of drill bits: 1000 hits (n=2) [Hole position accuracy] To evaluate the hole position accuracy, three printed wiring boards were stacked, and after 1000 hits (drilling), the error distance from the center of the bottom board hole was measured. A maximum value of 40 μm or less was marked "○", a value between 40 μm and 60 μm was marked "△", and a value exceeding 60 μm was marked "×". [Drill breakage] Drill breakage was evaluated by checking whether or not the drill broke when the drilling test was performed under the above conditions, with n=2 tests in which the drill did not break up to 1000 hits being marked "○", those that broke at least once being marked "△", and those that broke both times being marked "×". For test materials in which the drill broke within 1000 hits, the hole position accuracy was evaluated based on the data up to that point.

[0067] The evaluation results for edge cracking after hot rolling, the tensile strength and electrical conductivity of the aluminum substrate after final processing, and warpage, hole position accuracy, and drill breakage of the printed wiring board are shown in Table 3. From Table 3, it was confirmed that the rolled aluminum alloy materials described in the examples satisfy the chemical composition, tensile strength, elongation, and electrical conductivity specified in the present application.

[0068] [Table 1]

[0069] [Table 2]

[0070] [Table 3] [Industrial Applicability]

[0071] The rolled aluminum alloy material according to the present invention has excellent thermal conductivity and, when used in a wiring board, has a small difference in thermal expansion coefficient from that of copper foil, which reduces warping of the board caused by heat generation from the element, and cracks in the solder joints joining the copper foil and the element caused by thermal cycling, and is useful in that it can ensure sufficient machinability for drilling and router processing.

Claims

1. 1. An aluminum alloy rolled material characterized in that it has a chemical composition containing 13.5 to 17.4 mass% Si, 0.1 to 0.5 mass% Fe, 0.005 to 0.3 mass% Cu, 0.005 to 0.3 mass% Mn, 0.001 to 0.24 mass% Mg, 0.002 to 0.1 mass% Zn, 0.01 to 0.2 mass% Ti, 0.01 to 0.5 mass% Ga, and 0.008 to 0.05 mass% Sr, and further satisfies the condition (Si - 12.5) / (Fe + 2.2Mg) ≥ 1.9, with the balance being Al and unavoidable impurities.

2. 2. The rolled aluminum alloy material according to claim 1, further comprising one or more of Na: 0.0005 to 0.02 mass % and Ca: 0.0005 to 0.02 mass %.

3. 3. The rolled aluminum alloy material according to claim 1, wherein the P content is further restricted to 0.005% by mass or less.

4. 4. The aluminum alloy rolled material according to claim 1, further containing Ni: 0.001 to 0.5% by mass, Cr: 0.001 to 0.1% by mass, V: 0.001 to 0.03% by mass, B: 0.0002 to 0.02% by mass, and Zr: 0.0002 to 0.03% by mass.

5. 5. The aluminum alloy rolled material according to claim 1, further containing one or more of Pb: 0.01 to 0.3% by mass and Sn: 0.01 to 0.3% by mass, and one or more of Na: 0.0005 to 0.015% by mass and Ca: 0.0005 to 0.015% by mass, and is regulated to P: 0.003% by mass or less, In: 0.004% by mass or less, Bi: 0.01% by mass or less, and Sb: 0.01% by mass or less.

6. 6. The aluminum alloy rolled material according to claim 1, characterized in that it contains 14.2 to 16.8 mass% of Si, 0.12 to 0.4 mass% of Fe, 0.01 to 0.25 mass% of Cu, 0.06 to 0.25 mass% of Mn, 0.06 to 0.25 mass% of Mg, 0.01 to 0.08 mass% of Zn, 0.03 to 0.15 mass% of Ti, 0.05 to 0.3 mass% of Ga, and 0.01 to 0.04 mass% of Sr.

7. 7. The rolled aluminum alloy material according to claim 1, wherein the condition Mn / Fe≧0.2 is satisfied.

8. 8. The rolled aluminum alloy material according to claim 1, wherein second-phase particles having a size of 20 μm or more in the long side direction are observed by polishing a cross section of the plate thickness parallel to the rolling direction, and the second-phase particles have an observation area of ​​20% or less.

9. 9. A method for producing an aluminum alloy rolled material, comprising the steps of: performing a homogenization treatment at a temperature of 470°C or higher and 540°C or lower for 1 hour or longer and 20 hours or shorter before or after subsequent facing on an aluminum alloy ingot having a composition specified in the aluminum alloy rolled material according to any one of claims 1 to 8; holding the ingot at a temperature of 450°C or higher and 540°C or lower for 0.5 hours or longer and 10 hours; starting hot rolling; performing hot rolling with a reduction rate of 95% or higher and 99.5% or lower through multiple reduction passes; and then performing cold rolling with a reduction rate of 30% or higher and 98.5% or lower.

10. 10. The method for producing an aluminum alloy rolled material according to claim 9, further comprising a heat treatment step of holding the material at 260°C or higher and 400°C or lower for 0.5 hours or higher and 10 hours or lower, at least once between any pass and the next pass, from the start to the end of the cold rolling step.

11. 11. The method for producing a rolled aluminum alloy material according to claim 10, further comprising, at least once after the cold rolling step, a heat treatment step of holding the material at 150°C or higher and 240°C or lower for 1 hour or higher and 20 hours or lower.

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