阅读说明：本技术 低热膨胀铝合金轧制材料及其制造方法 (Low thermal expansion aluminum alloy rolled material and method for producing same ) 是由 山之井智明 伊藤昌明 角和繁 谷口和章 于 2021-04-29 设计创作，主要内容包括：本发明的课题是提供一种热传导性良好且热膨胀系数低的铝合金轧制材料。该铝合金轧制材料,化学组成含有Si：8～14质量％、Fe：0.1～1质量％、Cu：0.01～0.3质量％、Ni：0.005～0.5质量％、Cr：0.001～0.2质量％、Ga：0.01～0.5质量％、Ti：0.01～0.15质量％,余量由Al和不可避免的杂质构成,热膨胀系数α为19≤α≤22×10～(-6)/K,导电率σ为55％IACS以上。(The invention provides an aluminum alloy rolled material with good heat conductivity and low thermal expansion coefficient. The aluminum alloy rolled material comprises the following chemical components: 8-14 mass%, Fe: 0.1 to 1 mass%, Cu: 0.01 to 0.3 mass%, Ni: 0.005-0.5 mass%, Cr: 0.001 to 0.2 mass%, Ga: 0.01 to 0.5 mass%, Ti: 0.01 to 0.15 mass%, the balance being Al and unavoidable impurities, and the coefficient of thermal expansion alpha being 19-22 x 10 ‑6 And a conductivity sigma of 55% IACS or more.)

1. A low thermal expansion aluminum alloy rolled material characterized in that,

the chemical composition contains Si: 8-14 mass%, Fe: 0.1 to 1 mass%, Cu: 0.01 to 0.3 mass%, Ni: 0.005-0.5 mass%, Cr: 0.001 to 0.2 mass%, Ga: 0.01 to 0.5 mass%, Ti: 0.01 to 0.15 mass%, the balance being Al and unavoidable impurities, and a coefficient of thermal expansion alpha of 19. ltoreq. alpha. ltoreq.22X 10^-6And a conductivity sigma of 55% IACS or more.

2. The rolled low thermal expansion aluminum alloy material according to claim 1,

mn is limited to 0.05 mass% or less, Mg is limited to 0.05 mass% or less, Zn is limited to 0.05 mass% or less, V is limited to 0.02 mass% or less, B is limited to 0.03 mass% or less, and Zr is limited to 0.02 mass% or less.

3. The low thermal expansion aluminum alloy rolled material according to claim 1 or 2,

contains Ni: 0.06-0.3 mass%, Cr: 0.024 to 0.12 mass%, Ga: 0.06 to 0.3 mass%, further contains Ca: 0.0002 to 0.04 mass% and Sr: 0.0002 to 0.04 mass% or more.

4. The low thermal expansion aluminum alloy rolled material according to any one of claims 1 to 3,

contains Ca: 0.001 to 0.03 mass% and Sr: 0.001-0.03 mass%, and P is limited to 0.001 mass% or less.

5. A method for producing a low thermal expansion aluminum alloy rolled material, comprising the steps of:

an aluminum alloy ingot having the same composition as the low thermal expansion aluminum alloy rolled material according to any one of claims 1 to 4 is homogenized at a temperature of 480 ℃ to 550 ℃ for 1 hour to 20 hours before or after the subsequent surface cutting, and then is held at a temperature of 460 ℃ to 540 ℃ for 10 minutes to 10 hours, and then hot rolling is started, and after hot rolling is performed in a plurality of reduction passes at a reduction ratio of 95% to 99.5%, cold rolling is performed at 30% to 98.5%.

6. The method for producing a low thermal expansion aluminum alloy rolled material according to claim 5,

the method comprises at least 1 heat treatment step of holding at 260-400 ℃ for 0.5-10 hours before or after any one pass from the start to the end of the cold rolling step.

7. The method for producing a low thermal expansion aluminum alloy rolled material according to claim 6,

after the step of cold rolling, the method comprises at least 1 heat treatment step of holding at 150-240 ℃ for 1-20 hours.

Technical Field

The present invention relates to a circuit board, and more particularly to a low thermal expansion aluminum alloy rolled material used for a metal base board on which a heat generating element such as a power module is mounted, and a method for producing the same.

Background

In recent years, with the dramatic progress of electronic components and electronic circuits which are required to increase the efficiency of various power supply circuits by the electrical mounting of automobiles, metal-base printed boards have been widely used for circuits on which semiconductor elements, particularly power semiconductors (power devices), Light Emitting Diodes (LEDs) serving as light sources for various lighting devices, headlights of automobiles, tail lamps, and the like are mounted.

A standard structure of a metal-based printed circuit board used for such applications is to laminate an insulating layer on a metal and then bond a copper foil as a conductor constituting a circuit thereon.

In particular, in recent years, there has been an increasing demand for an aluminum substrate printed circuit board for lighting applications in which LED elements are mounted, which can extend the life by diffusing heat generated by light emission of LEDs.

In addition to the LED mounting substrate for illumination, it is also known that advantages such as stabilization of the performance of the power semiconductor element and protection from thermal damage of other electronic components due to a decrease in the temperature of the substrate can be obtained.

Copper or aluminum is used as the metal of the substrate. Among them, aluminum alloys have been studied for the purpose of weight reduction, but in the case of aluminum alloys, there are problems such as warpage of a substrate due to a difference in thermal expansion coefficient between the copper foil and a copper foil constituting a circuit with an insulating layer interposed therebetween, and cracks in a welded portion where the copper foil and an element are joined due to thermal cycles.

For such applications, pure aluminum alloys such as JIS1100, 1050, 1070 have excellent thermal conductivity, but have a large difference in thermal expansion coefficient from copper and a problem of low strength and warpage. On the other hand, Al — Mg-based alloys (5000-based alloys) such as JIS5052, which are known as high-strength materials, have high strength, but are disadvantageous in terms of the occurrence of cracks in the welded portion because of a large difference in thermal expansion coefficient with the copper foil constituting the circuit. Further, since the thermal conductivity is lower than that of pure aluminum, the heat dissipation characteristics are poor. Further, attempts have been made to reduce the difference in thermal expansion coefficient between the copper foil and the Al — Si alloy (4000 alloy), but the drilling workability in the production of printed wiring boards is not necessarily satisfied at present.

For example, patent document 1 discloses an Al-based printed wiring board comprising an Al-based alloy blank containing 3 to 20% of Si, 0.05 to 2.0% of Fe, 0.05 to 2.0% of Mg, 0.05 to 6.0% of Cu, 0.05 to 2.0% of Mn, 0.05 to 3.0% of Ni, 0.05 to 0.3% of Cr, 0.05 to 0.3% of V, 0.05 to 0.3% of Zr, and one or more of Zn exceeding 1.0% and 7.0% or less, wherein eutectic Si particles having an average particle size of 5 μm or less or primary crystal Si particles having a maximum particle size of 15 μm or less are dispersed in at least a surface layer of the blank, and anodic oxide films having a thickness of 5 μm or more are formed on both surfaces of the blank, and the remainder is composed of Al and impurities.

Patent documents 2 and 3 disclose, as a core material of a double-sided coating material, a double-sided coating material containing Si: 5-30 mass%, the balance consisting of Al and impurities, and further comprising Fe: 1 mass% or less, Ni: 1 mass% or less, Cu: 0.3 mass% or less, P: 0.1 mass% or less, B: 0.05 mass% or less, Mn: 0.2 mass% or less, Zn: a coating material and a printed wiring board, wherein the coating material has a low coefficient of thermal expansion of 0.2 mass% or less and is excellent in processability.

Patent document 4 discloses a printed wiring board using an Al — Mg (5052 alloy) or an Al — Mg — Si alloy for a printed wiring board anodized in a phosphoric acid electrolytic bath, and a method for producing the printed wiring board.

Patent document 5 discloses that an aluminum-based circuit board formed of a high heat-resistant resin having a molding temperature in a temperature range exceeding 250 ℃ contains Mn: 0.05 to 1.0 wt%, Mg: 3.5 to 5.6 wt%, Cr: 0.05 to 0.25 wt% of an aluminum alloy.

Prior art documents

Patent document 1: japanese laid-open patent publication No. 6-41667

Patent document 2: japanese patent laid-open publication No. 2006-328530

Patent document 3: japanese laid-open patent publication No. 2007-302939

Patent document 4: japanese patent laid-open No. 2006-24906

Patent document 5: japanese laid-open patent publication No. 2015-88612

Disclosure of Invention

However, in patent document 1, an Al — Si alloy having a low thermal expansion coefficient is selected, sizes and dispersions of eutectic Si particles and primary Si particles are investigated, and an anodic oxide film is improved to improve surface adhesion to an insulating adhesive layer, but machinability for drilling/milling is not investigated.

Patent document 2 is an invention for solving the surface adhesion problem in patent document 1 by double-sided coating, and although pure aluminum or Al — Mn aluminum alloy is used as the aluminum alloy to be the skin material, the coating process is involved, and therefore the process becomes complicated, which is disadvantageous in terms of manufacturing cost.

Patent document 3 is an invention for solving the problem of surface adhesion by double-sided coating as in patent document 2, and the use of Al — Mg — Si based aluminum alloy as the skin material is intended to improve the surface hardness in addition to the adhesion, but still includes a coating step, which complicates the steps and is disadvantageous in terms of manufacturing cost.

Patent document 4 aims to improve the characteristics of the anodic oxide film in order to obtain stable adhesion to a resin insulating material and to improve the adhesion, but the aluminum base material is Al — Mg or Al — Mg — Si, and the problem caused by thermal expansion with the copper foil is not solved.

Patent document 5 discloses a technique of preventing a reduction in flatness due to softening of aluminum and securing heat resistance in a high temperature environment for use in a power module or the like by laminating an insulating layer having high heat resistance and high strength aluminum having an annealing temperature equal to or higher than the heat resistance temperature thereof, but does not solve the problem due to thermal expansion with a copper foil.

As described above, it is very difficult to obtain an aluminum alloy sheet having poor thermal expansion with a copper foil, heat dissipation properties, surface adhesion, and machinability, which are problems of aluminum substrates.

In view of the above-described technical background, an object of the present invention is to provide a low thermal expansion aluminum alloy rolled material having high electrical conductivity and high strength, and a method for producing the same.

As a result of intensive studies to solve the above problems, the present inventors have found that an aluminum alloy rolled material can be obtained which suppresses warpage of a substrate due to a difference in thermal expansion coefficient with a copper foil constituting a circuit and cracks in a welded portion where the copper foil is joined to an element due to heat cycle, ensures machinability for drilling/milling, and has excellent heat dissipation properties by studying the composition and production process of the aluminum rolled material. That is, the present invention relates to the following.

(1) A low thermal expansion aluminum alloy rolled material characterized by a chemical composition containing Si: 8-14 mass%, Fe: 0.1 to 1 mass%, Cu: 0.01 to 0.3 mass%, Ni: 0.005-0.5 mass%, Cr: 0.001 to 0.2 mass%, Ga: 0.01 to 0.5 mass%, Ti: 0.01 to 0.15 mass%, the balance being Al and unavoidable impurities, and a coefficient of thermal expansion alpha of 19. ltoreq. alpha. ltoreq.22X 10^-6And a conductivity sigma of 55% IACS or more.

(2) The low thermal expansion aluminum alloy rolled material according to the above (1), wherein Mn is limited to 0.05 mass% or less, Mg is limited to 0.05 mass% or less, Zn is limited to 0.05 mass% or less, V is limited to 0.02 mass% or less, B is limited to 0.03 mass% or less, and Zr is limited to 0.02 mass% or less.

(3) The rolled aluminum alloy material with low thermal expansion according to the item (1) or (2), which contains Ni: 0.06-0.3 mass%, Cr: 0.024 to 0.12 mass%, Ga: 0.06 to 0.3 mass%, further contains Ca: 0.0002 to 0.04 mass% and Sr: 0.0002 to 0.04 mass% or more.

(4) The low-thermal-expansion aluminum alloy rolled material according to any one of the above (1) to (3), which contains Ca: 0.001 to 0.03 mass% and Sr: 0.001-0.03 mass%, and P is limited to 0.001 mass% or less.

(5) A method for producing a low thermal expansion aluminum alloy rolled material, comprising the steps of: an aluminum alloy ingot having the same composition as the low thermal expansion aluminum alloy rolled material according to any one of (1) to (4) above is homogenized at a temperature of 480 ℃ to 550 ℃ inclusive and for a time of 1 hour to 20 hours inclusive before or after the subsequent surface cutting, and then held at a temperature of 460 ℃ to 540 ℃ for 10 minutes to 10 hours inclusive, and then hot rolling is started, and after hot rolling is performed by a plurality of reduction passes at a reduction ratio of 95% to 99.5%, cold rolling is performed at 30% to 98.5%.

(6) The method for producing a low thermal expansion aluminum alloy rolled material according to the above (5), characterized by comprising at least 1 heat treatment step of holding at 260 ℃ to 400 ℃ for 0.5 hours to 10 hours before and after any one of the steps from the start to the end of the step of performing the cold rolling.

(7) The method for producing a low thermal expansion aluminum alloy rolled material according to the above (6), characterized by comprising at least 1 heat treatment step of holding at 150 ℃ to 240 ℃ for 1 hour to 20 hours after the step of cold rolling.

According to the invention described in the above (1), the chemical composition is made to contain Si: 8-14 mass%, Fe: 0.1 to 1 mass%, Cu: 0.01 to 0.3 mass%, Ni: 0.005-0.5 mass%, Cr: 0.001 to 0.2 mass%, Ga: 0.01 to 0.5 mass%, Ti: 0.01 to 0.15 mass%, the balance being Al and unavoidable impurities, and satisfying a thermal expansion coefficient alpha of 19. ltoreq. alpha. ltoreq.22X 10^-6The electric conductivity sigma is 55% IACS or more, and a low thermal expansion aluminum alloy rolled material can be produced.

According to the invention described in the above (2), Mn is limited to 0.05 mass% or less, Mg is limited to 0.05 mass% or less, Zn is limited to 0.05 mass% or less, V is limited to 0.02 mass% or less, B is limited to 0.03 mass% or less, and Zr is limited to 0.02 mass% or less, and thus a low thermal expansion aluminum alloy rolled material can be produced.

According to the invention described in the above (3), by containing Ni: 0.06-0.3 mass%, Cr: 0.024 to 0.12 mass%, Ga: 0.06 to 0.3 mass%, further contains Ca: 0.0002 to 0.04 mass% and Sr: 0.0002 to 0.04% by mass or more, and can be used for producing a low thermal expansion aluminum alloy rolled material.

According to the invention described in the above (4), by containing Ca: 0.001 to 0.03 mass% and Sr: 0.001 to 0.03 mass%, and P is limited to 0.001 mass% or less, and a low thermal expansion aluminum alloy rolled material can be produced.

According to the invention described in the above (5), the low thermal expansion aluminum alloy rolled material can be produced by subjecting an aluminum alloy ingot having the same composition as the low thermal expansion aluminum alloy rolled material described in any one of the above (1) to (4) to a homogenization treatment and cooling in this state at a temperature of 480 ℃ to 550 ℃ inclusive and for a time of 1 hour to 20 hours inclusive before or after the subsequent surface cutting, holding the homogenized aluminum alloy ingot at a temperature of 460 ℃ to 540 ℃ inclusive for 5 minutes to 10 hours inclusive, then starting hot rolling, subjecting the hot rolled material to hot rolling at a reduction of 95% to 99.5% inclusive in a plurality of reduction passes, and then subjecting the hot rolled material to a cold rolling step of 30% to 98.5% inclusive.

According to the invention described in the above (6), by including at least 1 heat treatment step of holding at 260 to 400 ℃ for 0.5 to 10 hours before and after any one pass from the start to the end of the step of performing cold rolling, a more excellent low-thermal expansion aluminum alloy rolled material can be produced.

According to the invention described in the above (7), after the step of performing cold rolling, the aluminum alloy rolled material can be produced to have a more excellent low thermal expansion by including at least 1 heat treatment step of holding at 150 ℃ to 240 ℃ for 1 hour to 20 hours.

Detailed Description

The present inventors have found that, in a method for producing an aluminum alloy rolled material by sequentially performing hot rolling and cold rolling, a low thermal expansion aluminum alloy rolled material having high electric conductivity and high strength can be obtained by controlling the surface temperature of the alloy material during hot rolling and performing at least one heat treatment during a period from the end of hot rolling to the end of cold rolling, and have completed the invention of the present application.

The aluminum alloy rolled material of the present application will be described in detail below.

The reason why the purpose of addition and the content of each element in the aluminum alloy composition of the present application are limited is as follows.

(Si content)

Si is an element necessary for lowering the thermal expansion coefficient of the aluminum alloy. The higher the Si content, the lower the thermal expansion coefficient. In the present invention, the Si content is 8 to 14 mass%. When the Si content is less than 8 mass%, a desired low thermal expansion coefficient cannot be obtained. On the other hand, if the Si content exceeds 14 mass%, although a lower thermal expansion coefficient can be obtained, melting at or above the eutectic point of Al-12.6 mass% Si increases the amount of primary crystal Si crystallized during casting, and rolling property during hot rolling decreases, and drilling/milling workability during substrate processing is adversely affected. The Si content is preferably 9 mass% or more and 13 mass% or less, and more preferably 10 mass% or more and 12 mass% or less.

(Fe content)

Fe is an element that lowers the thermal expansion coefficient of the alloy, and if it is small, it is expected to have an effect of refining crystal grains, and is effective for improving strength, and also has an effect of improving heat resistance. Therefore, the Fe content is set to 0.1 to 1 mass%. More preferably 0.2 to 0.8 mass%, and still more preferably 0.3 to 0.6 mass%.

(Cu content)

Cu is an element effective for improving strength, but if it is contained in a large amount, corrosion resistance is lowered. Further, if it is contained in a large amount, workability at the time of hot rolling is lowered, and heat conductivity at the time of product working is lowered, which adversely affects heat dissipation. Therefore, the Cu content is set to 0.01 to 0.3 mass%. More preferably 0.05% by mass or more and 0.25% by mass or less, and particularly preferably 0.1% by mass or more and 0.2% by mass or less.

(Ni content)

Ni is an element that lowers the coefficient of thermal expansion of the alloy, and if it is small, it is effective for improving the strength and also has an effect of improving the heat resistance, but if it is contained in a large amount, the workability is lowered, and hot rolling and cold rolling become difficult, so the Ni content is 0.005 to 0.5 mass%. More preferably 0.03 mass% or more and 0.4 mass% or less, and still more preferably 0.06 mass% or more and 0.3 mass% or less.

(Cr content)

Cr is an element effective for improving strength and refining crystal grains. However, if the amount is large, the workability at the time of hot rolling is lowered, and the thermal conductivity after product processing is remarkably lowered, which adversely affects the heat dissipation. Therefore, the content of Cr is set to 0.001 to 0.2 mass%. More preferably 0.012% by mass or more and 0.16% by mass or less, and particularly preferably 0.024% by mass or more and 0.12% by mass or less.

(Ga content)

Ga is an element that is likely to segregate at grain boundaries and crystal boundaries, and is an element effective for improving the drilling/milling workability of a difficult-to-cut material containing hard particles. However, if it is contained in a large amount, surface cracks occur in hot rolling and cold rolling to significantly reduce workability, and thermal conductivity after product working is reduced to adversely affect heat dissipation. Therefore, the content of Ga is set to 0.01 to 0.5 mass%. More preferably 0.03 mass% or more and 0.4 mass% or less, and still more preferably 0.06 mass% or more and 0.3 mass% or less.

(Ti content)

Ti has the effect of refining the grains when the alloy is cast into a slab. However, if the amount of the metal oxide is large, large-sized crystals are formed in a large amount, and the processability and thermal conductivity of the product are deteriorated. Therefore, the Ti content is set to 0.01 to 0.15 mass% or less. More preferably 0.03 mass% or more and 0.12 mass% or less, and particularly preferably 0.06 mass% or more and 0.1 mass% or less.

(Ca content)

Ca as an optional additive element is an element effective for refining eutectic Si particles. However, if it is contained in a large amount, ductility is reduced. Therefore, the content of Ca is 0.0002 to 0.04 mass%. More preferably 0.001 to 0.03 mass%, and particularly preferably 0.01 to 0.02 mass%.

(Sr content)

Sr, which is an optional additive element, is an element effective for the refinement of eutectic Si particles. However, if it is contained in a large amount, ductility is reduced. Therefore, the Sr content is 0.0002 to 0.04 mass%. More preferably 0.001 to 0.03 mass%, and particularly preferably 0.01 to 0.02 mass%.

(P content)

P as an optional additive element is effective for refining primary crystal Si, but if it coexists with Ca or Sr, the effect is significantly reduced. Therefore, in the present invention, the content of P in the case of the eutectic Si particles is 0.001 mass% or less, with priority given to the refinement of the eutectic Si particles.

(Mn content)

Mn is an alloy element that is generally added to refine the recrystallized grains, but if more than necessary, it causes a decrease in thermal conductivity. Therefore, the Mn content is preferably 0.05 mass% or less. More preferably 0.03 mass% or less, and particularly preferably 0.01 mass% or less.

(Mg content)

Mg is an element that contributes to strength improvement by solid-dissolving in aluminum. However, in the present invention, the heat conductivity during product processing is reduced, which causes adverse effects on heat dissipation. Therefore, the Mg content is preferably 0.05 mass% or less. More preferably 0.03 mass% or less, and particularly preferably 0.01 mass% or less.

(Zn content)

The amount of Zn is preferably as small as possible because the corrosion resistance of the alloy material is lowered when the Zn content is increased. Therefore, the Zn content is preferably 0.05 mass% or less. More preferably 0.03 mass% or less, and particularly preferably 0.01 mass% or less.

(B content)

B has an effect of refining the crystal structure of the ingot. However, if the amount is large, a large amount of hard crystals are formed, and the machinability of the product is significantly reduced. Therefore, the content of B is preferably 0.03 mass% or less.

(V content)

V is likely to segregate in grain boundaries, and if the V content is increased, ductility is lowered, so that a smaller amount is better. Therefore, the V content is 0.02 mass% or less.

(Zr content)

Zr is likely to segregate in grain boundaries, and if the Zr content is increased, the ductility is lowered, so that the smaller the Zr content, the better. Therefore, the Zr content is preferably 0.02 mass% or less.

Next, a treatment process for obtaining the aluminum alloy rolled material specified in the present application will be described.

And adjusting the melting components by a conventional method to obtain the aluminum alloy ingot. The obtained alloy ingot is preferably subjected to a homogenization treatment as a step before heating before hot rolling.

The homogenization treatment is performed to make the concentration of the elements dissolved in the aluminum alloy ingot uniform, but if the temperature is too high, eutectic melting occurs, and therefore, the homogenization treatment is preferably performed at 480 ℃ to 550 ℃, and particularly preferably at 490 ℃ to 540 ℃. The time is preferably 1 hour or more and 20 hours or less, and particularly preferably 2 hours or more and 15 hours or less.

The aluminum alloy ingot is homogenized and then heated before hot rolling. The preferable temperature range of heating before hot rolling is 460 ℃ to 540 ℃. The time is preferably 10 minutes to 10 hours. More preferred ranges are a temperature of 480 ℃ or higher and 530 ℃ or lower, and a time of 1 hour or higher and 8 hours or lower. Further, the homogenization treatment and the heating before hot rolling may be performed at the same temperature within the preferable temperature range of both the homogenization treatment and the heating before hot rolling.

After casting and before heating before hot rolling, the ingot is preferably subjected to surface cutting in order to remove impurity layers near the surface of the ingot. The surface cutting may be performed after casting and before the homogenization treatment, or may be performed after the homogenization treatment and before heating before hot rolling.

The aluminum alloy ingot heated before hot rolling is hot rolled. The hot rolling is composed of rough hot rolling and finish hot rolling, and after the rough hot rolling composed of a plurality of passes is performed by using a rough hot rolling mill, finish hot rolling is performed by using a finish hot rolling mill different from the rough hot rolling mill. In the present application, when the final pass in the roughing mill is set as the final pass of the hot rolling, the finish hot rolling may be omitted. The total reduction rate of hot rolling is preferably 95% or more and 99.5% or less.

When cold rolling is performed on a coil, the aluminum alloy rolled material after finish hot rolling may be coiled by a coiler to form a hot rolled coil. When the final pass of the hot rough rolling is set as the final pass of the hot rolling without the finish hot rolling, the aluminum alloy rolled material may be coiled by a coiler after the hot rough rolling to form a hot rolled coil.

In rough hot rolling, an aluminum alloy rolled material having a predetermined sheet crown and free from rolling end cracks (hereinafter referred to as edge cracks) and rolling surface defects which are relatively likely to occur in a difficult-to-work material can be obtained by temperature control based on a target sheet thickness structure (hereinafter referred to as a pass schedule) of each pass of rough hot rolling, a cooling medium amount, a roll rotation speed, inter-pass cooling, and the like.

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

In the present application, when the finish rolling is not performed after the final pass of the rough rolling, the surface temperature of the aluminum alloy rolled material immediately after the final pass of the finish rolling is set as the hot rolling completion temperature, and when the finish rolling is performed after the final pass of the rough rolling, the surface temperature of the aluminum alloy rolled material before the finish rolling is set as the hot rolling completion temperature.

The hot rolling completion temperature is preferably 280 ℃ or higher. By setting the hot rolling completion temperature to 280 ℃ or higher, edge cracking caused by a temperature decrease during rolling can be suppressed.

When a coil is wound after hot rolling in order to perform cold rolling as a subsequent step on the coil, if the temperature is too low, edge cracking at the wide end of the sheet tends to progress due to the coil tension.

Therefore, when the finish hot rolling is not performed in the case of coiling into a coil shape, as described above, the surface temperature of the aluminum alloy sheet after the final pass of the rough hot rolling is preferably 280 ℃ or higher, but when the finish hot rolling is performed after the rough hot rolling, the surface temperature of the aluminum alloy sheet after the finish hot rolling is preferably 250 ℃ or higher in order to prevent edge cracking of the sheet width end.

After the hot rolling is completed, in order to obtain a predetermined strength, it is preferable to perform the cold rolling until an aluminum alloy rolled material having a predetermined thickness is obtained with a total rolling reduction of 30% or more. The total rolling reduction of the aluminum alloy rolled material obtained by cold rolling 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 in consideration of the reduction in elongation due to work hardening.

After the completion of hot rolling, the aluminum alloy rolled material is subjected to heat treatment before or after cold rolling or between the passes thereof, whereby mechanical properties, particularly elongation, can be improved and electrical conductivity can be improved. In order to obtain the above-described effects in the present invention, it is preferable to perform the heat treatment at a temperature of 260 ℃ or more and less than 400 ℃ at least 1 time. The temperature of the heat treatment is more preferably 280 ℃ to 380 ℃, and particularly preferably 300 ℃ to 370 ℃.

After the hot rolling, the time for heat treatment of the aluminum alloy rolled material before and after the cold rolling or between the cold rolling passes is preferably 0.5 hours or more and 10 hours or less. More preferably 1 hour or more and 9 hours or less, and particularly preferably 2 hours or more and 8 hours or less.

And preparing the aluminum alloy rolling material with a preset thickness by the cold rolling after the heat treatment. By performing cold rolling, the strength is generally increased in work hardening. When the aluminum alloy rolled material age-hardened by the heat treatment is subjected to cold rolling after the hot rolling is completed, the strength improvement effect by work hardening can be expected.

Before or between cold rolling passes, a step of preventing sheet breakage by trimming edge cracks at the wide end of the sheet and further cold rolling may be included.

After the cold rolling step is completed, residual strain may remain in the rolled material, and the sheet material may be warped. In this case, it is effective to perform the heat treatment step of holding at 150 ℃ to 240 ℃ for 1 hour to 20 hours at least once. In this heat treatment, it is more effective to provide a rolled material on a flat plate and to perform straightening (pressure annealing) by sandwiching the rolled material between flat plates with weights placed from above.

Further, the aluminum alloy rolled material after the cold rolling may be cleaned as necessary.

The aluminum alloy rolled material of the present invention may be produced from a coil or a single sheet. The aluminum alloy rolled material may be cut in any step after the cold rolling, and the step after the cutting may be performed as a single sheet, or may be slit into strips according to the application.

According to the above production method, a low thermal expansion aluminum alloy rolled material having high electrical conductivity and excellent thermal conductivity can be obtained.

The aluminum alloy rolled material of the present invention has a thermal expansion coefficient (symbol α) of 19. ltoreq. α. ltoreq.22X 10^-6The conductivity (symbol σ) is defined as σ ≧ 55% IACS. The conductivity σ is more preferably 56% IACS or more, and particularly preferably 57% IACS or more. By satisfying the thermal expansion coefficient and the electrical conductivity specified in the present invention, an aluminum alloy rolled material can be obtained which suppresses warpage of a substrate due to a difference in thermal expansion coefficient between the copper foil and the substrate when used for a circuit board, cracks in a welded portion where the copper foil and an element are joined due to heat cycle, and the like, and which ensures machinability for drilling/milling processing and is excellent in heat dissipation.

Examples

The present invention will be described below with reference to examples. The present invention is not limited to the embodiments described herein, and can be implemented with appropriate modifications within the scope conforming to the spirit of the present invention, and all of them are also included in the technical scope of the present invention.

First, an aluminum alloy slab having a chemical composition of table 1 was subjected to surface cutting. Next, the alloy slab after the surface cutting was subjected to the homogenization treatment shown in table 2 in the heating furnace, then the temperature was lowered in the same furnace, and the alloy slab was held at the pre-hot-rolling heating temperature shown in table 2, and then hot-rolled under the conditions shown in table 2, thereby obtaining a hot-rolled sheet having the hot-rolling completion temperature and the sheet thickness shown in table 2. The alloy sheet after finish hot rolling was subjected to intermediate heat treatment, cold rolling, and final heat treatment as shown in table 2 to obtain an aluminum alloy sheet having a predetermined sheet thickness.

TABLE 2

Manufacturing process

The rolling workability during hot rolling was evaluated by the following method.

[ edge crack ]

When coiling a coil after hot rolling, the length of edge cracks at both ends of the width of the sheet from the end faces was recorded from the upper surface of the rolled sheet, and the maximum value of cracks occurring at the ends of the width of the sheet was 8mm or less and was indicated as "o", the maximum value of cracks exceeding 8mm and 15mm or less and was indicated as "Δ", and the maximum value of cracks exceeding 15mm was indicated as "x".

The tensile strength, elongation, electrical conductivity, and thermal expansion coefficient of the obtained alloy sheet were evaluated by the following methods.

[ tensile Strength, elongation ]

The tensile strength (σ B) and the elongation (δ) were measured by a conventional method at normal temperature using a test piece of JIS5 specified in JISZ2201, a sample taken in a direction parallel to the rolling direction.

Sigma B.gtoreq.120 MPa and delta.gtoreq.6% are described as ". smallcircle".

[ conductivity ]

To anneal the internationally adopted standard soft copper (volume resistivity 1.7241X 10)^-2μ Ω m) was set as 100% IACS, and the electric conductivity of the obtained alloy sheet was determined.

[ coefficient of thermal expansion ]

The linear expansion coefficient of the obtained alloy sheet was measured by a thermomechanical analysis (TMA) method. The measurement conditions are as follows.

The measurement method: TMA method (differential expansion mode)

Measurement temperature mode: 20 to 100 ℃ (reference temperature 20 ℃, heating speed 5 ℃/min)

Sample shape: 1X 3X 18mm

Atmosphere: in He gas

Reference sample: quartz crystal

The linear expansion (Delta L) of 20-100 deg.C (20 deg.C interval), the temperature change (Delta T) of 20 deg.C, and the length (L) at room temperature₀) The linear expansion coefficient (Delta L/L) at each temperature was determined₀) These are averaged as the thermal expansion coefficient.

As a method for evaluating the warpage of the printed wiring board, the warpage rate was measured. The warpage rate was measured as follows.

[ warping degree ]

For the evaluation of warpage, "5.4 warpage and distortion (drape method)" of JIS C copper-clad laminate test method was performed. The test materials were:

aluminum substrate: 1.5mm thick/insulating layer: 100 μm/copper foil: 70 μm front attachment

Cut size: 100 x 200mm

Heating at 220 deg.C for 120 s with a temperature meter for the aluminum substrate side of the printed circuit board, cooling with a fan, and measuring the maximum height h of the long side at room temperature₁Will be at a predetermined maximum height h before heating₀The difference of (a): h ═ H₁-h₀Divided by the length of the long side: the value obtained at 200mm was taken as the warpage: w ═ H/200 × 100 (%), with W of 1.0% or less being indicated by "o", and W exceeding 1.0% being indicated by "x".

As a method for evaluating the hole-opening property of a printed wiring board, measurement of hole position accuracy and determination of drill breakage were carried out. The drilling conditions were as follows.

A drill bit: phi 0.25mm superhard drill bit

Rotation speed: 125,000rpm

Feed speed: 2.5m/min

The number of drills: 1000 times (n is 2)

[ hole position accuracy ]

For the evaluation of the hole position accuracy, 3 printed wiring boards were stacked and drilled 1000 times, and then the error interval from the center of the lowermost board hole was measured, and the maximum value of 50 μm or less was indicated as "o", the maximum value of more than 50 μm and 80 μm or less was indicated as "Δ", and the maximum value of more than 80 μm was indicated as "x".

[ breaking properties of drill ]

When the drill was drilled under the above conditions, the drill was evaluated for the drill breakage, and the test with n being 2 was evaluated for the fact that no bending was performed until 1000 drilling times as indicated by "o" and any bending was performed once as indicated by "x". Further, for the test material with the broken drill before 1000 times of drilling, the hole position accuracy was evaluated using the data up to that point.

The results of evaluation of edge crack after hot rolling, tensile strength and electric 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 aluminum alloy rolled material described in the examples satisfies the chemical composition, tensile strength, elongation and electric conductivity specified in the present application.

TABLE 3

Evaluation results

Industrial applicability

In the aluminum alloy rolled material according to the present invention, since the aluminum alloy sheet having excellent electrical conductivity exhibits excellent thermal conductivity because of good correlation between thermal conductivity and electrical conductivity, and since the difference between the thermal expansion coefficient of the aluminum alloy sheet and that of the copper foil is small when used for a wiring board, it is useful to suppress warpage of the board due to heat generation, cracks in a welded portion where the copper foil is joined to an element due to heat cycle, and the like, and to ensure sufficient machinability for drilling/milling.