JP7724094B2 - Aluminum alloy rolled material and its manufacturing method - Google Patents

Description

This invention relates to a rolled aluminum alloy material suitable for use in metal base substrates that mount heating elements such as circuit boards and power modules, and to a method for manufacturing the same.

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

The standard construction of metal-based printed circuit boards used for such applications is to layer an insulating layer on top of metal, and then laminate copper foil, the conductor that makes up the circuit, on top of that.

In particular, demand has been increasing in recent years for aluminum-based printed circuit boards for lighting applications equipped with LED elements, as they can extend the lifespan of LEDs by dissipating heat generated by the LEDs.

Aluminum-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.

Copper or aluminum is used as the base metal. Of these, aluminum alloys are being investigated with the aim of reducing weight, but aluminum-based boards have issues such as board warping due to differences in the thermal expansion coefficient between them and the copper foil that makes up the circuit, which sandwiches the insulating layer, breaks in the copper foil in the circuit due to thermal cycling, and cracks in the solder joints that join the copper foil to the elements. Solving these issues has become increasingly important, particularly with the recent trend toward higher density packaging of electronic components, which has led to finer circuits, and an increase in high-heat components, resulting in the existence of areas that are subject to extreme thermal cycles.

For these applications, pure aluminum alloys such as JIS 1100, 1050, and 1070 have excellent thermal conductivity, but suffer from the issue of warping due to a large difference in thermal expansion coefficient with copper and low strength. On the other hand, Al-Mg alloys (5000 series alloys) such as JIS 5052, known as high-strength materials, have high strength but a large difference in thermal expansion coefficient with the copper foil that makes up the circuit, posing a disadvantage in terms of the possibility of cracks occurring in the solder joints mentioned above. Furthermore, their thermal conductivity is lower than that of pure aluminum, resulting in inferior heat dissipation characteristics. Attempts have also been made to reduce the difference in thermal expansion coefficient with copper foil by using Al-Si alloys (4000 series alloys), but these do not fully address the above issues, nor do they necessarily provide satisfactory drilling processability during printed wiring board manufacturing.

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

Patent Documents 2 and 3 disclose a double-sided clad material and printed wiring board that have a low thermal expansion coefficient and excellent processability. The core material contains 5 to 30% by mass of Si, with the remainder consisting of Al and impurities, and further contains up to 1% by mass of Fe, up to 1% by mass of Ni, up to 0.3% by mass of Cu, up to 0.1% by mass of P, up to 0.05% by mass of B, up to 0.2% by mass of Mn, and up to 0.2% by mass of Zn.

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

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 highly heat-resistant resin with a molding temperature in the range above 250°C.

Japanese Patent Application Publication No. 6-41667 Japanese Patent Application Laid-Open No. 2006-328530 Japanese Patent Application Laid-Open No. 2007-302939 Japanese Patent Application Laid-Open No. 2006-24906 JP 2015-88612 A

However, while Patent Document 1 selects an Al-Si alloy with a low thermal expansion coefficient and examines the size and dispersion of eutectic Si particles and primary Si particles, and improves the anodized film to improve surface adhesion with the insulating adhesive layer, it does not examine machinability in drilling and routering.

Patent Document 2 attempts to solve the surface adhesion issue posed by Patent Document 1 by using double-sided cladding. It uses a pure aluminum or Al-Mn aluminum alloy for the skin material, but the inclusion of a cladding process complicates the process and creates manufacturing cost disadvantages.

Like Patent Document 2, Patent Document 3 attempts to solve the problem of surface adhesion by double-sided cladding, using an Al-Mg-Si system for the aluminum alloy used as the skin material to increase surface hardness in addition to adhesion. However, the inclusion of a cladding process again complicates the process, resulting in disadvantages in terms of manufacturing costs.

Patent Document 4 examines in detail how to improve the properties of anodized films, aiming to achieve stable adhesion to resin insulating materials and improve adhesion. However, the aluminum substrate is Al-Mg (5000 series) or Al-Mg-Si (6000 series), and the issue of thermal expansion with copper foil remains unresolved.

Patent Document 5 discloses that by laminating a highly heat-resistant insulating layer with high-strength aluminum that has an annealing temperature higher than the heat resistance temperature of the insulating layer, a decrease in flatness due to softening of the aluminum is prevented, and heat resistance in high-temperature environments such as for power modules is ensured. However, this does not solve the issue of thermal expansion with copper foil.

As mentioned above, it is extremely difficult using conventional technology to obtain aluminum alloy sheets that have the thermal expansion difference with copper foil, heat dissipation properties, surface adhesion, and machinability that are issues with aluminum substrates.

In light of the above-mentioned technical background, the present invention aims to provide an aluminum alloy rolled material with a low thermal expansion coefficient and high thermal conductivity, and a method for manufacturing the same.

As a result of extensive research, the present inventors have discovered that by examining the composition and manufacturing process of rolled aluminum material, 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/router processing. This finding led to the present invention. That is, the present invention has the following configurations (1) to (10).
(1) A rolled aluminum alloy material having a chemical composition containing 13.5 to 17.4 mass% Si, 0.1 to 1.5 mass% Fe, 0.005 to 0.3 mass% Cu, 0.005 to 0.2 mass% Mn, 0.25 to 1.5 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 0.5≦(Si−12.5)/(Fe+2.2Mg)≦1.8, with the balance being Al and unavoidable impurities.
(2) The rolled aluminum alloy material according to (1) above, further comprising one or more of Na: 0.0005 to 0.04 mass % and Ca: 0.0005 to 0.04 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 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) The aluminum alloy rolled material according to any one of (1) to (4) above, further containing one or more of Pb: 0.01 to 0.6% by mass and Sn: 0.01 to 0.6% by mass, and one or more of Na: 0.0005 to 0.02% by mass and Ca: 0.0005 to 0.02% 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) The rolled aluminum alloy material according to any one of (1) to (5) above, characterized by containing 14.2 to 16.8% by mass of Si, 0.3 to 1.2% by mass of Fe, 0.01 to 0.25% by mass of Cu, 0.01 to 0.18% by mass of Mn, 0.3 to 1.3% by mass of Mg, 0.01 to 0.08% by mass of Zn, 0.03 to 0.15% by mass of Ti, 0.05 to 0.3% by mass of Ga, and 0.01 to 0.03% by mass of Sr.
(7) The rolled aluminum alloy material according to any one of (1) to (6) above, characterized in that, when observed by polishing a cross section of the plate thickness parallel to the rolling direction, the area occupancy of intermetallic compounds having a size of 20 μm or more in the long side direction and containing Si as a main component (Si composition ratio of 80% by mass or more) is 40% or less of the total area occupancy of intermetallic compounds having a size of 20 μm or more in the long side direction.
(8) 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 (7) above, performing a homogenization treatment at a temperature of 470°C to 540°C for 1 hour to 20 hours, then holding the ingot at a temperature of 450°C to 540°C for 0.5 hours to 10 hours, and then starting hot rolling; performing hot rolling with a rolling reduction of 95% to 99.5% through multiple rolling passes; and then cold rolling of 30% to 98.5%.
(9) A method for producing an aluminum alloy rolled material according to (8) 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.
(10) A method for producing an aluminum alloy rolled material according to (9) 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.

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 the compositional relationship between Si, Fe, and Mg.

The rolled aluminum alloy materials described in (2) and (3) above further suppress the coarsening of crystallized particles (intermetallic compounds) and improve hot workability.

The rolled aluminum alloy material described in (4) above can achieve an even lower thermal expansion coefficient while minimizing the decrease in thermal conductivity.

The rolled aluminum alloy material described in (5) above improves drilling workability.

The rolled aluminum alloy material described in (6) above can further combine a low thermal expansion coefficient with high thermal conductivity.

The rolled aluminum alloy material described in (7) above exhibits even better hot workability and improved drilling workability.

The method for manufacturing rolled aluminum alloy material described in (8) above makes it possible to produce rolled aluminum alloy material that has both a low thermal expansion coefficient and high thermal conductivity.

The method for manufacturing rolled aluminum alloy material described in (9) above can improve the mechanical properties of the rolled aluminum alloy material, particularly its elongation, and can also improve its thermal conductivity.

The method for manufacturing rolled aluminum alloy material described in (10) above can improve the mechanical properties of the rolled aluminum alloy material and eliminate residual strain, thereby suppressing the occurrence of warping.

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)
The rolled aluminum alloy material contains the essential elements Si, Fe, Cu, Mn, Mg, Zn, Ti, Ga, and Sr. The significance and content of each element are as follows. The balance is Al and unavoidable impurities.

Si 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 achieved. On the other hand, if the Si content exceeds 17.4 mass%, an even lower thermal expansion coefficient can be achieved, but the amount of primary Si crystallized during melting and casting at eutectic compositions above Al-12.6 mass% Si increases, reducing rollability during hot rolling and making drilling and routing difficult during substrate processing. Furthermore, the Si content is preferably 14.2 to 16.8 mass%, and even more preferably 14.5 to 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 should be 0.1 to 1.5 mass%. 0.3 to 1.2 mass% is more preferable, and 0.5 to 0.9 mass% is even more preferable.

Mg is an element that contributes to improving strength by dissolving in aluminum, but at the same time, it can also reduce thermal conductivity and reduce heat dissipation during product processing. It is also well known to form Mg-Si intermetallic compounds with Si, and if the Mg content is particularly high, these will become coarse crystals during melting and casting, reducing workability and promoting the occurrence of edge cracks during hot rolling and cold rolling. Therefore, the Mg content should be 0.25 to 1.5 mass%. It is more preferable that it be 0.3 to 1.3 mass% or less, and even more preferable that it be 0.4 to 0.8 mass%.

Cu is an element that is 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 range is set to 0.005 to 0.3 mass%. A range of 0.01 to 0.25 mass% is more preferable, with a range of 0.08 to 0.18 mass% being even more preferable.

Mn is an alloying element that is generally added to refine recrystallized grains, but adding more than necessary can result in a decrease in thermal conductivity. Therefore, the Mn content should be 0.005 to 0.2 mass%. It is more preferable that it be 0.01 to 0.18 mass%, and even more preferable that it be 0.03 to 0.18 mass%.

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

Ti has the effect of refining crystal grains when the alloy is cast into slabs. However, if it is contained in large amounts, many large crystals will be formed, reducing the workability and thermal conductivity of the product. Therefore, the Ti content should be 0.01 to 0.2 mass% or less. 0.03 to 0.15 mass% is more preferable, and 0.06 to 0.12 mass% is even more preferable.

Ga is an element that tends to segregate at grain boundaries and crystallized particle interfaces, making it effective for improving the drill and router machinability of difficult-to-cut materials containing hard particles. However, if it is contained in large amounts, it can cause surface cracks during hot rolling and cold rolling, significantly reducing machinability, and it can also reduce thermal conductivity after product processing, adversely affecting heat dissipation. Therefore, the Ga content should be 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 0.2 mass% is even more preferable.

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 0.03 mass%, and even more preferably 0.015 to 0.025 mass%.
(Na, Ca)
The rolled aluminum alloy material may further contain one or more of Na and Ca, if necessary. These elements mainly affect the intermetallic compounds that crystallize from the molten aluminum alloy during casting. The significance of adding or controlling each element, and the content thereof, are as follows:

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 quantities, it can induce porosity during melting and casting, just like Sr, so adding more than necessary is not recommended. Therefore, in this invention, the addition of Sr is prioritized, and the Na content can be up to 0.0005 to 0.04 mass%. 0.0005 to 0.02 mass% is more preferable, and 0.0005 to 0.01 mass% is even more preferable.

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 desirable. Therefore, in the present invention, the addition of Sr is prioritized, and the Ca content can be up to 0.0005 to 0.04 mass%. 0.0005 to 0.02 mass% is more preferable, and 0.0005 to 0.01 mass% is even more preferable.
(P)
In the aluminum alloy rolled material, the P content is further restricted in addition to the above-mentioned Sr, Na, and Ca. P is well known as an element effective in refining primary crystal Si, but its coexistence with Sr, Na, and Ca significantly reduces this effect. Therefore, the P content is limited to 0.005% by mass or less. It is further 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, reducing workability and making hot rolling and cold rolling difficult. Therefore, the Ni content is set to 0.001 to 0.5 mass%. It is more preferably 0.02 to 0.35 mass%, and even more preferably 0.06 to 0.25 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.

Cr 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, adversely affecting heat dissipation. Therefore, the Cr content is set to 0.001 to 0.1 mass%. 0.002 to 0.08 mass% is more preferable, and 0.004 to 0.06 mass% is even more preferable.

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

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

B has the effect of refining crystal grains when the alloy is cast into slabs. However, if it is contained in large amounts, many hard crystallized products are formed, significantly reducing the machinability of the product. Therefore, the B content is set to 0.0002 to 0.02 mass%. 0.001 to 0.015 mass% is more preferable, and 0.002 to 0.01 mass% is even more preferable.
(Pb, Sn)
The rolled aluminum alloy material may further contain at least one of Pb and Sn, if necessary.

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 large amounts can cause surface cracks during hot rolling and cold rolling, reducing workability. Therefore, the Pb and Sn contents should be 0.01 to 0.6 mass%. A range of 0.05 to 0.2 mass% is preferable, with a range of 0.03 to 0.15 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.

Sb and Bi, when present together with Pb and Sn, are effective elements in improving the drilling and routering properties of difficult-to-cut materials containing hard particles. However, they also inhibit the refinement effect of Sr. Therefore, in this invention, the refinement effect of adding 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.

In content as an inevitable 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 rolled aluminum alloys, 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, in mass%, have the relationship 0.5≦(Si−12.5)/(Fe+2.2Mg)≦1.8. In other words, by setting the Si, Fe, and Mg contents within the above-mentioned ranges within the composition ranges of each element, each element can be further refined.
(intermetallic compound)
In rolled aluminum alloys, if there are a large number of large-sized intermetallic compounds containing Si as the main component, hot workability and drillability are impaired. Therefore, when a cross section of the plate thickness parallel to the rolling direction is polished and observed, it is desirable that the area occupancy of intermetallic compounds having a size of 20 μm or more in the long side direction and containing Si as the main component (composition ratio of 80% by mass or more) is 40% or less of the total intermetallic compounds having a size of 20 μm or more in the long side direction. This can be expected to further improve hot workability and drillability. An area occupancy of 35% or less is more preferable, and 30% or less is even more preferable.
(Method for 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.
(Homogenization treatment process)
The homogenization treatment is carried out to make the concentrations of elements dissolved in the aluminum alloy ingot uniform, but since eutectic melting occurs if the treatment temperature is too high, the homogenization treatment 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.

Generally, when an aluminum alloy ingot is rolled, facing is performed to remove an impurity layer near the surface of the ingot. The homogenization treatment described above may be performed either before or after facing.
(Preheating step)
The aluminum alloy ingot is preheated before being subjected to rolling by holding the aluminum alloy ingot at 450°C to 540°C for 0.5 to 10 hours. More preferably, the preheating conditions are 470°C to 520°C for 1 to 8 hours.

Since the processing conditions for the homogenization treatment and the processing conditions for the preheating partially overlap, a single heat treatment can be carried out under the overlapping conditions, and this heat treatment can serve as both the homogenization treatment and the preheating.
(Hot rolling process)
The preheated aluminum alloy ingot is hot rolled in multiple passes at a reduction ratio of 95% to 99.5%.

Hot rolling consists of rough hot rolling and finish hot rolling. After rough hot rolling consisting of multiple 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. Note that in the present invention, if the final pass in the rough hot rolling mill is the final pass of hot rolling, finish hot rolling can be omitted.

If the cold rolling described below is performed on a coil, the aluminum alloy rolled material after finish hot rolling can be wound on a winding device to form a hot-rolled coil. If 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 can be wound on a winding device to form a hot-rolled coil.

In hot rough rolling, by controlling the target thickness for each pass of hot rough rolling and the temperature through the amount of coolant, roll rotation speed, and cooling between passes, it is possible to obtain aluminum alloy rolled material with the specified sheet crown and free of rolled edge cracks (hereinafter referred to as "edge cracks") and rolled surface defects that are relatively common in difficult-to-process materials.

Cooling between passes in the rough hot rolling may be performed sequentially on the rolled portions while the aluminum alloy rolled material is being rolled, or may be performed after the entire aluminum alloy rolled material has been rolled. The cooling method is not limited, and may be water cooling, air cooling, or the use of a coolant.

In the present invention, if 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 the hot rolling end temperature.If 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 the hot rolling end temperature.

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 end 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 end 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. If cold rolling is performed on the rolled aluminum alloy material that has been age-hardened by the heat treatment after hot rolling, the strength can be expected to be improved through work hardening. The total reduction in cold rolling is preferably 30% or more to obtain a predetermined strength. The total reduction in cold rolling of the rolled aluminum alloy material is more preferably 40% or more, and particularly preferably 50% or more. The upper limit of the total reduction is set to 98.5% or less, taking into account the decrease in elongation due to work hardening.

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.

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, as well as electrical conductivity. The heat treatment may be 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 1 to 9 hours, with 2 to 8 hours being even more preferred.

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. While the cold rolling may leave residual strain in the rolled material, causing warping of the sheet, the heat treatment can eliminate this residual strain. A particularly preferred temperature for heat treatment is 160°C to 220°C, with a particularly preferred heat treatment time of 5 to 20 hours. Furthermore, this heat treatment is even more effective when the rolled material is placed on a flat plate and then clamped between two flat plates with weights placed on top to perform pressure annealing.

The manufacturing method for the rolled aluminum alloy material described above 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 it may be 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 may be washed as needed after cold rolling.

The present invention will be described below using examples. It should be noted that the scope of the present invention is not limited to the examples described here, and modifications may be made as appropriate within the scope of the present invention, and all such modifications are within the technical scope of the present invention.

First, an aluminum alloy slab having the chemical composition shown in Table 1 was cast, and the rolled surface of the resulting slab was subjected to facing to a thickness of 300 mm, width of 950 mm, and length of 1500 mm. Next, the homogenization treatment shown in Table 2 was carried out in a heating furnace, after which the temperature was lowered in the same furnace and held at the pre-hot rolling heating temperature shown in Table 2. Hot rolling was carried out under the conditions shown in Table 2, resulting in a hot-rolled sheet having the hot-rolling temperature and thickness shown in Table 2. The alloy sheet after finish hot rolling was subjected to intermediate heat treatment, cold rolling, and final heat treatment shown in Table 2 to obtain an aluminum alloy sheet of the specified thickness.

The rolling workability during hot rolling was evaluated by the following method.
[Cracked ear]
When the coil was wound after hot rolling, the length of the edge cracks at both ends of the plate width was recorded from the top surface of the rolled plate, and cracks that occurred at the end of the plate width with a maximum value of 8 mm or less were marked "○", those with a maximum value of more than 8 mm but not exceeding 15 mm were marked "△", and those with a maximum value of more than 15 mm were marked "×".
[Area Occupancy Ratio of Si-Based Intermetallic Compounds]
The area occupancy of the intermetallic compounds in the obtained alloy plate was measured by first cutting the plate thickness cross section after the final heat treatment parallel to the rolling direction, fixing it with an embedding resin, and then emery-polishing and buffing it using a rotary polisher to prepare a test material. Next, five 250 × 200 μm fields were selected using an electron probe microanalyzer (EPMA), and composition analysis was performed on intermetallic compounds (crystallized particles) within the field of view with the longest side of 20 μm or more. After separating them into those with Si as the main component (composition ratio of 80 mass% or more) and those without, the area occupancy of particles with Si as the main component was calculated using a binarization process, and those with 40% or less were marked "○" and those with more than 40% were marked "×".

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 in a direction parallel to the rolling direction.
Tensile strength of 150 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 mmφ
Atmosphere: Vacuum. Thermal conductivity of 188 W/m·K or more was rated as "◯", and that of less than 188 W/m·K was rated as "X".
[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, temperature rise rate: 5°C/min)
・Sample size: 1.5 x 3 x 18 mm
Atmosphere: He gas Reference sample: Quartz The linear expansion coefficient at each temperature was calculated from the amount of linear expansion (ΔL) from 20 to 100°C (in 20°C intervals), the temperature change (ΔT) from 20°C, and the length at room temperature (L ₀ ) (ΔL/L ₀ ), and these were averaged to determine the thermal expansion coefficient. Samples with a thermal expansion coefficient of 19.6×10 ^-6 /K or less were marked "Good", and those exceeding 19.6×10 ^-6 /K were marked "Poor".

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 according to 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.

The test materials are
Aluminum base: 1.5 mm thick / Insulating layer: 100 μm / Copper foil: 70 μm, fully attached Cutting dimensions: 100 × 200 mm
The printed wiring board was heated and held at 220°C for 120 seconds at the actual temperature of the aluminum substrate 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) was divided by the long side length (200 mm) to obtain the warpage rate: W = H/200 x 100 (%). W of 1.0% or less was marked as "○", and W of more than 1.0% was marked as "×".

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 Rotation speed: 125,000 rpm
Feed speed: 2.5 m/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 50 μm or less was evaluated as "○", a value between 50 μm and 80 μm or less was evaluated as "△", and a value exceeding 80 μm was evaluated as "×".
[Drill breakage]
The drill breakage resistance was evaluated based on whether or not the drill broke when the drilling test was carried out under the above conditions, and a drill that did not break up to 1000 hits in n = 2 tests was marked as "○", and a drill that broke at least once was marked as "×". For test materials in which the drill broke up to 1000 hits, the hole position accuracy was evaluated based on the data up to that point.

Table 3 shows the evaluation results for edge cracking after hot rolling, the tensile strength and electrical conductivity of the aluminum base material after final processing, and warpage, hole position accuracy, and drill breakage of the printed wiring board. Table 3 confirms that the aluminum alloy rolled material described in the examples satisfies the chemical composition, tensile strength, elongation, and electrical conductivity specified in this application.

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. This makes it possible to reduce warping of the board caused by heat generation and cracks in the solder joints joining the copper foil and elements caused by thermal cycling, and also ensures sufficient machinability for drilling and routering, making it useful.

Claims (7)

a chemical composition containing 13.5 to 17.4 mass% Si, 0.1 to 1.5 mass% Fe, 0.005 to 0.3 mass% Cu, 0.005 to 0.2 mass% Mn, 0.25 to 1.5 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 0.5≦(Si−12.5)/(Fe+2.2Mg)≦1.8, with the balance being Al and unavoidable impurities;
1. An aluminum alloy rolled material characterized in that, when observed by polishing a cross section of the plate thickness parallel to the rolling direction, the area occupancy of intermetallic compounds having a size of 20 μm or more in the long side direction and containing Si as a main component (composition ratio of 80 mass% or more) is 40% or less of the total intermetallic compounds having a size of 20 μm or more in the long side direction . The aluminum alloy rolled material according to claim 1, further comprising one or more of Na: 0.0005 to 0.04 mass% and Ca: 0.0005 to 0.04 mass%. The rolled aluminum alloy material according to claim 1 or claim 2, further comprising a P content restricted to 0.005 mass% or less. The aluminum alloy rolled material according to any one of claims 1 to 3 further contains Ni: 0.001 to 0.5 mass%, Cr: 0.001 to 0.1 mass%, V: 0.001 to 0.03 mass%, B: 0.0002 to 0.02 mass%, and Zr: 0.0002 to 0.03 mass%. The aluminum alloy rolled material according to any one of claims 1 to 4, further containing one or more of Pb: 0.01 to 0.6 mass% and Sn: 0.01 to 0.6 mass%, and one or more of Na: 0.0005 to 0.02 mass% and Ca: 0.0005 to 0.02 mass%, with the contents of P: 0.003 mass% or less, In: 0.004 mass% or less, Bi: 0.01 mass% or less, and Sb: 0.01 mass% or less. The aluminum alloy rolled material according to any one of claims 1 to 4, characterized in that it contains 14.2 to 16.8 mass% Si, 0.3 to 1.2 mass% Fe, 0.01 to 0.25 mass% Cu, 0.01 to 0.18 mass% Mn, 0.3 to 1.3 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 0.03 mass% Sr. A method for producing a rolled aluminum alloy material according to any one of claims 1 to 6 ,
The method includes a step 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 of the aluminum alloy ingot, then holding the aluminum alloy ingot at a temperature of 450°C or higher and 540°C or lower for 0.5 hours or longer and 10 hours, and then starting hot rolling, performing hot rolling with a reduction rate of 95% or higher and 99.5% or lower through multiple rolling passes, and then performing cold rolling with a reduction rate of 30% or higher and 98.5% or lower;
A heat treatment step is carried out at least once between the start and end of the cold rolling step, between any pass and the next pass, by holding the temperature at 260°C or higher and 400°C or lower for 0.5 hours or higher and 10 hours or lower, and further
A method for producing an aluminum alloy rolled material, comprising carrying out at least one heat treatment step at 150°C or higher and 240°C or lower for 1 hour or longer and 20 hours or shorter after completing a cold rolling step .