JP2011105982A - Aluminum alloy and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aluminum alloy which has excellent rolling workability while having a low Young's modulus, to provide aluminum alloy foil obtained by rolling the aluminum alloy, to provide a ceramic wiring board in which the aluminum alloy foil is joined to at least either side of a ceramic substrate, to provide a mounting structure using the ceramic wiring board, and further, to provide a method for producing the aluminum alloy, a method for producing the aluminum alloy foil and a method for producing the ceramic wiring board. <P>SOLUTION: The aluminum alloy comprises an Al phase and an Al<SB>4</SB>Ca phase. The Al<SB>4</SB>Ca phase includes Al<SB>4</SB>Ca crystallized products, and the average value of the long side of the Al<SB>4</SB>Ca crystallized products is ≤50 μm. The method for producing the aluminum alloy includes: a melting step (A) of melting Al-Ca-containing metal; and a cooling step (B) of cooling the obtained melt, and, in the cooling step (B), when the melt has a temperature more than a liquidus, ultrasonic waves are applied to the melt to crystallize out Al4Ca crystallized products. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an aluminum alloy and a method for producing the same. In particular, the present invention relates to an aluminum alloy excellent in rolling workability and a method for producing the same. The aluminum alloy can be suitably used as a constituent member for wiring of a semiconductor module.

  A stress buffer material containing a metal having a reduced Young's modulus can give a large elastic displacement to a load stress, and is used in various applications. For example, when used as a spring material, the number of turns of the spring can be reduced, so that the spring can be reduced in size. In addition, due to its supple characteristics, when used in eyeglasses, the feeling of use can be improved. Furthermore, when used as a material for a golf club, the flight distance can be improved. In addition, it can be suitably used for products such as robots and artificial bone auxiliary materials.

  As stress buffer materials having such a low Young's modulus, for example, titanium alloys, Ni—Ti shape memory alloys, magnesium, and the like are known. However, since both the titanium-based alloy and the Ni—Ti shape memory alloy are based on titanium, they have a problem of high cost. Magnesium (pure metal) has a low Young's modulus on the order of 40 GPa, but has a problem that its strength, heat resistance, corrosion resistance, or durability is low and its use is limited.

  Thus, in recent years, a technique has been developed in which an aluminum alloy based on aluminum, which is a relatively low cost among metals, is used as a stress buffer material. For example, Patent Document 1 discloses a method for producing a low elastic modulus aluminum-based composite material in which pure aluminum or an aluminum alloy is used as a matrix and 5 to 80% by volume of a carbon component is composited as a reinforcing material. The low elastic modulus aluminum composite material manufactured by the manufacturing method is excellent in strength, thermal conductivity, vibration absorption performance, heat resistance, wear resistance, and the like.

JP 2005-272945 A

  However, the aluminum alloy described in Patent Document 1 has a problem that rolling workability is low and cracking occurs when it is rolled to a thickness of 1 mm or less, and it cannot be processed into a foil shape. . If the aluminum alloy can be processed into a foil shape, for example, it can be used for components such as wiring of semiconductor modules, metal seals, leaf spring materials, etc., so an aluminum alloy as a stress buffer material Can be greatly expanded.

  Then, an object of this invention is to provide the aluminum alloy excellent in rolling workability, having a low Young's modulus.

The present invention relates to an aluminum alloy containing an Al phase, and _Al 4 Ca phase, the _Al 4 Ca phase comprises _Al 4 Ca crystallizate, the average value of the long sides of the _Al 4 Ca crystallizate 50 μm or less.

According to the present invention, it becomes easy to move the Al ₄ Ca crystallized substance in the matrix with dislocations, so that the rolling workability of the aluminum alloy can be remarkably improved.

It is the figure which represented typically the structure | tissue of the aluminum alloy which concerns on one Embodiment of this invention. Of al 4 _Ca crystallizate is a diagram for explaining the long sides and short sides. It is a two-dimensional state diagram on the Al side of an Al-Ca alloy. It is a figure showing an example of the ultrasonic application apparatus suitably used with the manufacturing method of the aluminum alloy of this invention. It is the figure which represented typically the mounting structure which concerns on one Embodiment of this invention. 2 is an optical micrograph of a cross section of the aluminum alloy produced in Example 1. FIG. 2 is an optical micrograph of a cross section of the aluminum alloy foil produced in Example 1. FIG. 2 is an optical micrograph of a cross section of the aluminum alloy produced in Comparative Example 1. 5 is an optical micrograph of a cross section of the aluminum alloy produced in Comparative Example 2.

Hereinafter, preferred embodiments of the present invention will be described. The present embodiment relates to an aluminum alloy including an Al phase and an Al ₄ Ca phase. The aluminum alloy, _Al 4 comprises Ca phase of _Al 4 Ca crystallizate, the average value of the long sides of the _Al 4 Ca crystallized substances, characterized in that at 50μm or less.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. In addition, the dimensional ratios in the drawings are exaggerated for convenience of explanation, and may be different from the actual ratios.

<Aluminum alloy>
FIG. 1 is a diagram schematically showing the structure of an aluminum alloy according to an embodiment of the present invention. The structure as shown in FIG. 1 can be confirmed by observing the cross section of the aluminum alloy using an optical microscope. An aluminum alloy 1 in FIG. 1 includes an Al phase 2 and an Al ₄ Ca phase (3a, 3b) in which Al and Ca are combined. Among the Al ₄ Ca phases (3a, 3b), the Al ₄ Ca phase 3a is an Al ₄ Ca primary crystal that crystallizes first in the process of cooling the molten aluminum alloy (hereinafter referred to as “Al ₄ Ca crystals”). Also referred to as “product 3a”). As shown in FIG. 1, the Al ₄ Ca crystallized product 3 a has a needle-like form and is uniformly (randomly) dispersed in the aluminum alloy 1. When the molten aluminum alloy is further cooled after the Al ₄ Ca crystallized product 3a is crystallized, the Al component and the Ca component in the molten metal are solidified by a eutectic reaction, and the Al phase 2 and the Al ₄ Ca phase 3b The eutectic structure 4 containing is formed. The Al phase 2 and the Al ₄ Ca phase 3 b in the eutectic structure 4 exist in close mixing and function as a matrix of the aluminum alloy 1.

  The aluminum alloy of this embodiment is an ingot-like aluminum alloy that can be obtained by casting a molten aluminum alloy. Since the conventional aluminum alloy has a remarkably small elongation, it has been impossible to form into a foil of 1 mm or less by rolling. On the other hand, the present invention remarkably improves the elongation of the ingot-shaped aluminum alloy, and a desired shape such as a plate shape, a foil shape, a rod shape, or a linear shape by various forming processes such as forging and rolling. It can be formed into a shape. Hereinafter, the aluminum alloy of this embodiment will be described in detail.

[Al phase]
In the aluminum alloy of this embodiment, the Al phase functions as an alloy matrix. The Al phase has a role of improving the lightness, thermal conductivity, electrical conductivity, and ductility of the aluminum alloy.

[Al ₄ Ca phase]
The Al ₄ Ca phase is a component formed by combining an Al component and a Ca component contained in an aluminum alloy, and has a role of improving the strength of the alloy. The Al ₄ Ca phase exists as an Al ₄ Ca crystallized product (reference numeral 3a shown in FIG. 1), and also forms an alloy matrix in the form of a eutectic structure (reference numeral 3b shown in FIG. 1) intimately mixed with the Al phase. Can form. The Al ₄ Ca phase contained in the eutectic structure and the Al ₄ Ca crystallized product are common in that they contain the Al ₄ Ca component, but have different roles on the shape, formation process, and mechanical properties of the alloy. In this field, these are distinguished.

(Al ₄ Ca crystallized product)
The Al ₄ Ca crystallized product is an Al ₄ Ca primary crystal that crystallizes first in the process of cooling the molten aluminum alloy containing Al and Ca, and has a long side length of 5 μm or more. Say. The Al ₄ Ca crystallized matter improves the strength of the aluminum alloy and contributes to the ductility of the alloy. In the present specification, the “long side of the Al ₄ Ca crystallized product” means the rectangle when the outer extension of the Al ₄ Ca crystallized product is surrounded by a rectangle having the minimum area, as indicated by 11 in FIG. Means the long side of

The Al ₄ Ca crystallized product has a needle-like form as shown in FIG. In the aluminum alloy of this embodiment, the average value of the long side of the Al ₄ Ca crystallized product is 50 μm or less, preferably 30 μm or less, and more preferably 20 μm or less. When the long side of the Al ₄ Ca crystallized product exceeds 50 μm, it becomes difficult to move the Al ₄ Ca crystallized product with dislocations, so that the elongation of the aluminum alloy becomes small and the rolling processability may be reduced. . Therefore, a more preferred form, of the _Al 4 Ca crystallizate, the ratio of the number of _Al 4 Ca crystallizate long side is 10μm or _less, be more than 80% relative to the total number of _Al 4 Ca crystallizate More preferably, it is 90% or more, and particularly preferably 95% or more. The “average value of the long side of the Al ₄ Ca crystallized product” refers to the Al ₄ Ca crystallized product existing in the region of 0.1 mm × 0.1 mm when the cross section of the aluminum alloy is observed with an optical microscope. It is determined by dividing the total long side by the number of Al ₄ Ca crystals. “The ratio of the number of Al ₄ Ca crystallized substances having a long side of 10 μm or less among the Al ₄ Ca crystallized substances” is an area of 0.1 mm × 0.1 mm when the cross section of the aluminum alloy is observed with an optical microscope. to the total number of Al 4 _Ca crystallized substances present in the long side is determined by calculating the ratio of the number of Al 4 _Ca crystallizate is 10μm or less.

Moreover, in the aluminum alloy of this embodiment, the average aspect ratio of the Al ₄ Ca crystallized product is preferably 10 or less, and more preferably 5 or less. When the average aspect ratio is in such a range, the Al ₄ Ca crystallized product can easily move with dislocations in the forming process such as forging and rolling. Further, in the molding process, the Al ₄ Ca crystallized product is easily refined. Therefore, the elongation of the aluminum alloy is increased and the rolling processability is further improved. In the present specification, the “aspect ratio” means a value obtained by dividing the length of the long side of the Al ₄ Ca crystallized product by the length of the short side. The "short sides of the _Al 4 Ca crystallizate" means the maximum width of the vertical _Al 4 Ca crystallizate against _Al 4 Ca crystallized products of the long sides 11, as shown in 13 of FIG. “Average aspect ratio of Al ₄ Ca crystallized product” is the average of the aspect ratio of Al ₄ Ca crystallized product existing in a region of 0.1 mm × 0.1 mm when the cross section of the aluminum alloy is observed with an optical microscope. It is obtained by calculating the value.

The aluminum alloy of this embodiment is an Al-based alloy containing Al as a main component and contains Ca. The Ca content in the aluminum alloy is preferably 5 to 12 atomic%, more preferably 6 to 12 atomic%, and further preferably 6 to 9 atomic%. When the Ca content is 5 atomic% or more, the volume fraction of Al ₄ Ca crystallized material in the aluminum alloy is increased, and the Young's modulus can be sufficiently reduced. On the other hand, when the content of Ca is 12 atomic% or less, Al ₄ Ca crystallized substances are dispersed in a state of being separated from each other through the matrix, so that elongation is increased and excellent rolling workability is exhibited. Can do. In addition, the aluminum alloy of the present embodiment may contain an element other than Ca (hereinafter also referred to as “third element”) as long as the effects of the present invention are not significantly impaired. Examples of the third element include Group 2 elements such as Mg, Sr, and Ba, Group 4 to 11 elements (transition metal elements) such as Mn, Cu, Fe, Ti, Cr, and Zr, and Zr. Examples include Group 12 elements (zinc group elements), Group 14 elements such as Si, Group 15 elements such as P, and the like. These elements may contain only 1 type and may contain it in combination of 2 or more type. In addition, the aluminum alloy of this form can contain an unavoidable impurity other than this.

As described above, the aluminum alloy of this embodiment is excellent in elongation as compared with a conventional aluminum alloy because the Al ₄ Ca crystallized product has a predetermined shape. The elongation at break of the aluminum alloy of this embodiment is preferably 0.5% or more, more preferably 2% or more, at room temperature. By having such an elongation rate, excellent rolling processability can be exhibited, and a foil having a thickness of 1 mm or less can be easily produced. In addition, the value measured by the method used in the below-mentioned Example is employ | adopted for the elongation rate of the aluminum alloy in this specification.

<Method for producing aluminum alloy>
The aluminum alloy of the present embodiment described above can be manufactured by the following manufacturing method. That is, the aluminum alloy manufacturing method of this embodiment includes a melting step (A) for melting a metal containing Al and Ca, and a cooling step (B) for cooling the obtained melt. Then, in the cooling step (B), melt when having a temperature above the liquidus, it is characterized by crystallizing the Al 4 _Ca crystallized products to impart ultrasonic waves to the melt. Hereinafter, the preferable form of this manufacturing method is demonstrated.

  First, in the melting step (A), a metal containing Al and Ca is melted. The metal containing Al and Ca may be an alloy containing Al and Ca prepared in advance, or a metal composition in which pure Ca metal is added to Al pure metal so as to have a desired composition. Good. Also, the melting method is not particularly limited, and a conventionally known method can be appropriately employed. As an example, the metal containing Al and Ca is put in a crucible and heated to a temperature of 700 to 1000 ° C. in a melting furnace under atmospheric pressure or an inert gas atmosphere such as Ar. As the melting furnace, an electric furnace, a high-frequency melting furnace, or the like can be used.

Next, in the cooling step (B), the melt obtained in the melting step (A) is cooled. In this step, when the melt has a temperature equal to or higher than the liquidus, an ultrasonic wave is applied to the melt to precipitate an Al ₄ Ca crystallized product. Here, in order to describe the manufacturing method of this embodiment, a two-dimensional state diagram (FIG. 3) on the Al side of the Al—Ca alloy will be described. As shown in FIG. 3, a general Al—Ca alloy exists as a liquid melt in a liquid phase region (reference symbol L) above the liquidus line 1. When the melt is cooled and reaches the temperature of the liquidus 1, Al ₄ Ca crystallized material begins to precipitate. By Al 4 _Ca crystallizate is precipitated, so decreases Ca content in the melt, the Al 4 _Ca crystallizate precipitation starts, while the temperature of the melt is cooled to a eutectic point p Continues to crystallize Al ₄ Ca crystals. When the cooling further proceeds and the temperature of the melt becomes less than the eutectic point p, the Ca component remaining in the melt is solidified by the eutectic reaction and together with the Al phase as the Al ₄ Ca phase contained in the eutectic structure. Precipitate. For example, when a molten aluminum alloy having a Ca content of 7 atomic% is gradually cooled from 1000 ° C., the path indicated by the arrow in FIG. 3 is followed. In the stage (I) of the arrow, the aluminum alloy exists as a melt. In the stage (II), an Al ₄ Ca crystallized crystallizes in the melt, and in the stage (III) solidification of the eutectic structure occurs. .

In the manufacturing method of the present embodiment, ultrasonic waves are applied to the melt when the melt has a temperature equal to or higher than the liquidus. That is, normally, Al ₄ Ca crystallized material does not crystallize at a temperature higher than the liquidus, but by applying ultrasonic waves to the melt, energy is imparted to the core of the Al ₄ Ca crystallized material. (Self nuclei in which Al ₄ Ca crystallized crystals crystallized locally on the molten metal surface or horn surface, etc., or heterogeneous nuclei such as MgO and Al ₂ O ₃ mixed in a trace amount) Is formed. Thereby, many nuclei of Al ₄ Ca crystallized products can be produced rather than formed by ordinary cooling. As a result, Al 4 _Ca crystallizate one single crystal size is reduced, it is possible to produce an aluminum alloy containing a desired Al 4 _Ca crystallized substances as described above.

  The method for applying ultrasonic waves to the melt is not particularly limited. However, for example, it is preferable that the ultrasonic wave is directly applied to the melt using an ultrasonic horn as shown in FIG. Further, the conditions of ultrasonic waves to be applied can be appropriately set by those skilled in the art depending on the amount of the aluminum alloy and the temperature of the melt. Usually, it is applied in an air atmosphere or an inert atmosphere such as Ar at a frequency of 20 to 22 kHz, an output of 0.3 to 3 kW, and a total amplitude of about 20 μm.

The temperature of the melt when applying ultrasonic waves is essential to be a temperature equal to or higher than the liquidus, but is preferably in the temperature range of 0 to + 120 ° C. from the liquidus, more preferably the liquidus. The temperature range is from 0 to + 100 ° C., more preferably from 0 to + 70 ° C. from the liquidus, and particularly preferably from 0 to + 50 ° C. from the liquidus. By applying ultrasonic waves in such a temperature range, a large number of nuclei of Al ₄ Ca crystallized products can be crystallized.

  The number of times of applying ultrasonic waves is not particularly limited, but it is preferably irradiated continuously in the above temperature range. The application time is not particularly limited, but is preferably 1 to 90 seconds, and more preferably 1 to 30 seconds.

After the melt by applying ultrasonic crystallized the Al 4 _Ca crystallized products, and further cooling the melt comprising Al 4 _Ca crystallizate grown Al 4 _Ca of crystallized substance crystals, further By cooling, the remaining melt is solidified to form a eutectic structure. The cooling method is not particularly limited, but the cooling rate is preferably 1 ° C./second or more so that the nuclei of the crystallized Al ₄ Ca crystals are not melted again. As a more preferred form, a method is used in which the melt is poured into a mold immediately after application of ultrasonic waves and rapidly cooled. By rapidly cooling using such a method, a desired Al ₄ Ca crystallized shape can be created without dissolving the crystallized Al ₄ Ca crystallized nuclei again.

<Aluminum alloy foil>
Since the aluminum alloy of this embodiment is excellent in elongation as described above, it can be rolled to a thickness of 1 mm or less, which has been impossible in the past. That is, according to the present invention, there is provided an aluminum alloy foil having a thickness of 30 to 80 μm formed by rolling the aluminum alloy. As for the thickness of aluminum alloy foil, although 30-800 micrometers is essential, Preferably it is 50-500 micrometers, More preferably, it is 100-200 micrometers.

Further, the aluminum alloy foil of the present embodiment, Al 4 _Ca crystallizate contained in the above-described aluminum alloy is divided by rolling, every one of Al 4 _Ca crystallizate divided material is cut through the matrix. According to one embodiment, as shown in FIG. 7 of Example 1 to be described later, 80% of the Al ₄ Ca crystallized product having an acicular shape in the aluminum alloy by rolling is 10 to 50 μm on the long side. The aspect ratio is divided to 15 or less. Furthermore, according to FIG. 7, the area ratio of the divided Al ₄ Ca crystallized material having a long side of 10 to 50 μm is in the range of 5 to 15% with respect to the total area of the structure of the aluminum alloy foil. . By having such a structure, it is difficult for the corrosion occurring on the surface to reach the deep part of the aluminum alloy foil, and excellent corrosion resistance can be exhibited.

The aluminum alloy foil of this embodiment has low elastic characteristics and wide elastic characteristics due to the characteristics of the Al ₄ Ca phase, and further has a characteristic that the coefficient of linear expansion is low. In particular, when the content of Ca in the aluminum alloy is 5 to 12 atomic%, the above characteristics can be more remarkable. Preferably, the Young's modulus of the aluminum alloy foil is 100 GPa or less, and the yield stress (0.2% yield strength) is as large as 70 MPa or more. Such an aluminum alloy foil can take the deformation in the elastic deformation region even if the total strain is 0.2% or more. Furthermore, the linear expansion coefficient is preferably 25 × 10 ⁻⁶ / ° C. or less. Furthermore, since it is excellent in electrical conductivity and thermal conductivity, it is suitable for components such as wiring of semiconductor modules, metal seals, leaf spring materials, and the like. In this specification, Young's modulus and linear expansion coefficient are values measured by the method used in the examples described later.

The aluminum alloy foil of this embodiment can be obtained by rolling the aluminum alloy described above. There is no restriction | limiting in particular in the method of rolling, Conventionally well-known methods, such as hot rolling or cold rolling, can be employ | adopted suitably. Moreover, you may include the process of forging an aluminum alloy before rolling. By passing through the forging process, voids contained in the structure of the aluminum alloy are reduced, and the strength of the alloy can be increased. Moreover, since the Al ₄ Ca crystallized substance contained in the aluminum alloy is divided by forging, rolling workability can be further improved.

<Ceramic wiring board>
Since the aluminum alloy foil of this embodiment is excellent in mechanical properties as described above, it can be suitably used as a constituent member such as a wiring of a semiconductor module. That is, according to the present invention, there is provided a ceramic wiring board having a ceramic substrate and the aluminum alloy foil bonded to at least one surface of the ceramic substrate. Hereinafter, each member of the ceramic wiring board of this embodiment will be described in detail.

[Ceramic substrate]
The ceramic used for the ceramic substrate is not particularly limited as long as it is an electrically insulating material. For example, silicon nitride (Si ₃ N ₄ ), aluminum nitride (AlN), aluminum oxide (Al ₂ O ₃ ), and mullite (3Al ₂ O ₃ · 2SiO ₂ ). Among these, aluminum nitride (AlN) is preferably included because it can be applied to a power module of an electric vehicle that can be used particularly in a high temperature environment.

[Joint material]
A joining member is a member used in order to join aluminum alloy foil to the surface of a ceramic substrate, for example, a metal nanoparticle and solder are mentioned.

  Specifically, the metal material used for the metal nanoparticles preferably includes at least one metal selected from the group consisting of gold, silver, and copper. Moreover, it is preferable that the material used for the solder includes at least one alloy selected from the group consisting of Au—Si, Au—Sn, Au—Ge, and Sn—Cu. By using these metal nanoparticles or solder, the ceramic substrate and the aluminum alloy foil can be joined at a temperature of 400 ° C. or lower.

  Since the ceramic wiring board of this embodiment uses the aluminum alloy foil having a small linear expansion coefficient as the wiring metal as described above, it is possible to reduce the thermal stress due to the difference in linear expansion coefficient between the wiring board and the ceramic substrate. Further, since it has a low elastic characteristic and a wide elastic region, plastic deformation can be suppressed even if the total strain is 0.2% or more due to thermal stress. Therefore, even if the low-temperature to high-temperature thermal cycle is repeated, it is possible to effectively prevent peeling of the wiring metal from the ceramic substrate.

<Manufacturing method of ceramic wiring board>
The ceramic wiring board of this embodiment can be manufactured by joining the ceramic substrate and the above-described aluminum alloy foil. The temperature at the time of joining becomes like this. Preferably it is 400 degrees C or less, More preferably, it is 350 degrees C or less. By bonding at such a temperature, it is possible to prevent the ceramic substrate from being damaged by a thermal shock during bonding. In addition, joining at 400 degrees C or less is attained by using joining members, such as the above-mentioned metal nanoparticle or solder.

<Mounting structure>
A semiconductor chip can be mounted on the surface of the aluminum alloy foil of the ceramic wiring board of this embodiment to form a mounting structure. FIG. 5 is a diagram schematically showing a mounting structure according to an embodiment of the present invention. In the mounting structure 20 of FIG. 5, a 12 × 12 mm aluminum alloy foil 32 is bonded to one surface of a 15 × 15 mm ceramic substrate 31 made of AlN via a bonding member 33. Furthermore, a 5 × 5 mm semiconductor chip 34 made of SiC is bonded to the surface of one aluminum alloy foil 32.

  As the semiconductor material of the semiconductor chip, SiC (silicon carbide), GaAs, Si, or the like can be used. Among these, it is preferable to use SiC because a high voltage and a high current can flow and heat resistance is excellent.

  Such a mounting structure can be suitably used for controlling an electric vehicle such as an electric vehicle (EV) or a hybrid electric vehicle (HEV) because the wiring metal can be prevented from peeling off from the ceramic substrate even in a high temperature environment. sell.

  The effect of this invention is demonstrated using a following example and a comparative example. However, the technical scope of the present invention is not limited only to the following examples.

<Manufacture of aluminum alloy and aluminum alloy foil>
[Example 1]
(casting)
An Al—Ca alloy (liquidus temperature: 650 ° C.) having a Ca content of 7 atomic% (10 mass%) was melted in a crucible. The obtained melt was cooled to 700 ° C. and irradiated with ultrasonic waves (frequency 21.8 kHz, output 2.4 kW, amplitude 20 μm) in an air atmosphere at a temperature range of 700 to 650 ° C. Thereafter, an aluminum alloy melt at 650 ° C. was cast into a 70 mm × 70 mm × 15 mm book mold and cooled to prepare an aluminum alloy having a thickness of 15 mm.

An optical micrograph of a cross section of the obtained aluminum alloy is shown in FIG. According to FIG. 6, it was confirmed that acicular crystals having an average value of 50 μm on the long side were precipitated in the structure of the obtained aluminum alloy. As a result of EDX analysis, the acicular crystals were confirmed to be Al ₄ Ca. By applying ultrasonic waves immediately above the liquidus line of the alloy (temperature range of 650 ° C. [+50 to 0 ° C.]), a large number of Al ₄ Ca crystallized seeds are formed. Thereby, even when the Al ₄ Ca crystallized substance was completely grown, it was considered that the average value of the long side could be 50 μm or less.

(Hot forging)
The 15 mm thick aluminum alloy ingot obtained in the casting process was hot forged at a material temperature of 400 ° C., a mold temperature of 150 ° C., and a workability of 70% to a thickness of 4.5 mm.

(Cold rolling)
An aluminum alloy foil was produced by rolling the aluminum alloy after hot forging to a thickness of 50 μm with a cold rolling mill. Reduction per time was 0.1 mm.

An optical micrograph of a cross section of the obtained aluminum alloy foil is shown in FIG. According to FIG. 7, Al 4 _Ca crystallizate is crushed by forging and rolling, it was confirmed that became fine Al 4 _Ca crystallizate.

<Measurement of elastic modulus and elongation at break>
Specimen shape: JIS14B-3 specimen (however, the total length is 50 mm), a stress-strain diagram was obtained with an Instron digital material testing machine Model 5581, and the elastic modulus and elongation were measured. Evaluation was performed at a test speed of 0.2 mm / min, a test temperature of 23 ° C., and each n = 2.

  When the elongation percentage of the aluminum alloy was measured by this method, it was 15%.

<Corrosion resistance test>
A constant temperature and high humidity test was conducted on a 100 μm thick foil. The test environment was a temperature of 85 ° C. and a humidity of 85% RH for 100 hours.

From the results of the corrosion resistance test, corrosion occurred only on the surface of the test piece and did not reach the inside of the test piece. This is because the Al 4 _Ca exposed on the surface is separated is Al 4 _Ca crystallized substances together be corroded, the progress of corrosion was believed to be due to being suppressed.

<Measurement of linear expansion coefficient>
The linear expansion coefficient of the aluminum alloy foil was determined by measurement with a thermomechanical analyzer (Thermal Mechanical Analysis; TMASINT thermomechanical analyzer TMA-120C). The temperature increase / decrease rate was 5 ° C./min, and an average linear expansion coefficient of 23 to 300 ° C. was obtained. The atmosphere was reflux N ₂ (200 ml / min), and the static load was 98 mN (100 gf).

[Comparative Example 1]
(casting)
An aluminum alloy was produced in the same manner as in Example 1 except that the molten aluminum alloy was cast into a book mold at 750 ° C. without being irradiated with ultrasonic waves and cooled.

An optical micrograph of a cross section of the obtained aluminum alloy is shown in FIG. According to FIG. 8, the average value of the long side of the Al ₄ Ca crystallized material in the structure of the aluminum alloy cast without irradiating ultrasonic waves was 50 μm or more.

(Hot forging and cold rolling)
Although cold rolling was attempted after hot forging in the same manner as in Example 1, it was not possible to process the foil because of its extremely low rollability.

<Measurement of elongation>
An attempt was made to measure the elongation of the aluminum alloy using the same method as in Example 1, but the material was brittle and could not be subjected to the test.

[Comparative Example 2]
Aluminum alloy powder (average particle size: 50 μm) having a Ca content of 9 atomic% was prepared by an atomizing method using pure metals of Al and Ca having a purity of 99.9% or more. After filling this aluminum alloy powder into a cylindrical container having a diameter of 50 mm, a deaeration treatment was performed at 300 to 400 ° C., and an aluminum alloy was produced by extrusion forming at 400 ° C. into a rod shape having a diameter of 10 mm.

An optical micrograph of a cross section of the obtained aluminum alloy is shown in FIG. As shown in FIG. 9, an aluminum alloy produced by an atomization method has a form in which Al 4 _Ca particles having a particle size of less than 5μm are dispersed in the Al matrix, Al 4 _Ca grains are in contact with each other It was.

(Hot rolling)
Although the hot rolling was tried with respect to the obtained aluminum alloy, an ear crack generate | occur | produced with thickness 1mm, and foil was not able to be obtained.

<Measurement of elongation>
Using the same method as in Example 1, the elongation of the aluminum alloy was measured and found to be 0.2%.

<Corrosion resistance test>
When a corrosion resistance test was conducted on an aluminum alloy foil having a thickness of 1 mm using the same method as in Example 1, the networked Al ₄ Ca particles propagated and corrosion progressed to the depth of the test piece. confirmed.

<Production of mounting structure>
[Example 2]
On one surface of a ceramic substrate (15 × 15 mm, thickness 635 μm) made of AlN (linear expansion coefficient: 4.5 × 10 ⁻⁶ / ° C., Young's modulus: 300 GPa), the aluminum alloy foil prepared in Example 1 ( 12 × 12 mm, thickness 400 μm, linear expansion coefficient: 24.1 × 10 ⁻⁶ / ° C., Young's modulus: 41.4 GPa). A mounting structure (FIG. 4) was produced by bonding a SiC chip (5 × 5 mm, thickness 300 μm) to the surface of the bonded aluminum alloy foil in the same manner as described above. Silver nanoparticles were used for the bonding of the ceramic substrate and the aluminum alloy foil and the bonding of the aluminum alloy foil and the SiC chip under the conditions of a bonding temperature of 350 ° C., a pressure of 5 MPa, and a holding time of 30 minutes.

[Comparative Example 3]
Cu foil (linear expansion coefficient: 17.0 × 10 ⁻⁶ / ° C., Young's modulus: 120 GPa) was used as the wiring metal. For joining, an aluminum brazing material (aluminum 88 mass%, silicon 12 mass%) added with 3 mass% of hydrogenated titanium and tungsten is used. The bonding temperature is 600 ° C., the applied pressure is 2 MPa, the holding time. The test was performed for 30 minutes. Other than this, a mounting structure was fabricated in the same manner as in Example 2.

[Comparative Example 4]
Al foil (linear expansion coefficient: 23.89 × 10 ⁻⁶ / ° C., Young's modulus: 68.2 GPa) was used as the wiring metal. Other than this, a mounting structure was fabricated in the same manner as in Comparative Example 3.

<Thermal cycle test>
The mounting structures produced in Example 2 and Comparative Examples 3 and 4 were subjected to a thermal cycle test. In the thermal cycle test, one cycle was held at 200 ° C. for 15 minutes after being held at room temperature (23 ° C.) for 15 minutes in a nitrogen atmosphere. After 100 cycles, the mounting structure was cut along the broken line in FIG. 5, and the interface between the ceramic substrate and the wiring metal was observed to determine whether peeling occurred. The results are shown in Table 1.

  According to Table 1, in Example 2 using an aluminum alloy foil as the wiring metal, it was shown that the wiring metal did not peel from the ceramic substrate even when the thermal cycle was repeated, and had excellent durability characteristics.

  On the other hand, in Comparative Example 3 using Cu foil as the wiring metal and Comparative Example 4 using Al foil, the wiring metal was peeled from the ceramic substrate by the thermal cycle. The peeling in Comparative Example 3 was considered to be caused by a large difference in linear expansion coefficient between AlN and Cu, and a large stress generated at the interface between the ceramic substrate and the wiring metal due to the high elastic modulus of Cu. Further, the peeling in Comparative Example 4 is due to the fact that a large stress is generated due to the large difference in thermal expansion coefficient between AlN and Al, and that Al is permanently deformed due to the narrow elastic region of Al, resulting in large deformation of Al. It was considered a thing.

1 Aluminum alloy,
2 Al phase,
3a Al ₄ Ca crystallized product,
3b Al ₄ Ca phase contained in the eutectic structure,
4 eutectic structure,
11 Long side,
13 Short side,
21 vibrator,
22 horn,
23 Melt,
24 crucible,
25 heater,
26 Electric furnace,
27 thermocouple,
30 mounting structure,
31 Ceramic substrate,
32 Wiring metal,
33 joining members,
34 Semiconductor chip,
l Liquidus line,
p eutectic point,
L Liquid phase region.

Claims (10)

An Al—Ca alloy containing an Al phase and an Al ₄ Ca phase,
The Al ₄ Ca phase contains Al ₄ Ca crystals,
The _Al 4 Ca average value of the long sides of the crystallizate is 50μm or less, an aluminum alloy. The Al 4 _Ca average aspect ratio of crystallizate is 10 or less, an aluminum alloy of claim 1.   The aluminum alloy according to claim 1 or 2, wherein the elongation is 0.5% or more.   The aluminum alloy according to any one of claims 1 to 3, wherein the content of Ca is 5 to 12 atomic%.   The aluminum alloy foil which rolls the aluminum alloy of any one of Claims 1-4, and is 30-800 micrometers in thickness. A ceramic substrate;
A ceramic wiring board having the aluminum alloy foil according to claim 5 bonded to at least one surface of the ceramic board.   A mounting structure using the ceramic wiring board according to claim 6. A melting step (A) for melting a metal containing Al and Ca, and a cooling step (B) for cooling the obtained melt,
In the cooling step (B), when the melt has a temperature equal to or higher than the liquidus, an aluminum alloy manufacturing method is provided in which an ultrasonic wave is applied to the melt to crystallize an Al ₄ Ca crystallized product. A melting step (A) for melting a metal containing Al and Ca,
A cooling step (B) for cooling the obtained melt, and a rolling step (C) for rolling the aluminum alloy obtained in the cooling step (B),
In the cooling step (B), when the melt has a temperature equal to or higher than the liquidus, a method for producing an aluminum alloy foil, wherein an Al ₄ Ca crystallized product is crystallized by applying ultrasonic waves to the melt. . A melting step (A) for melting a metal containing Al and Ca,
A cooling step (B) for cooling the obtained melt,
Rolling step (C) for rolling the aluminum alloy obtained in the cooling step (B), and joining for joining the aluminum alloy foil obtained in the rolling step (C) and the ceramic substrate at a temperature of 400 ° C. or lower. Including step (D),
In the cooling step (B), when the melt has a temperature equal to or higher than the liquidus, a method for producing a ceramic wiring substrate, wherein an ultrasonic wave is applied to the melt to crystallize an Al ₄ Ca crystallized product. .