JP2018024930A - Oxygen-free copper sheet, production method of oxygen-free copper sheet and ceramic circuit board - Google Patents

Abstract

Kind Code: A1 A technique is provided that can suppress cracking of a ceramic substrate and separation of an oxygen-free copper plate and a ceramic substrate from an interface even when the temperature of the ceramic wiring substrate is repeatedly raised and lowered. SOLUTION: It is formed into a flat plate by rolling, and when heated at a temperature of 200° C. for 30 minutes, the Vickers hardness is reduced to HV80 or less, and is heated at a temperature of 800° C. or more and 1080° C. or less for 5 minutes or more. It has the property that the 0.2% yield strength after heating is within 16 MPa. [Selection figure] None

Description

  The present invention relates to an oxygen-free copper plate, a method for producing an oxygen-free copper plate, and a ceramic wiring board.

  A ceramic wiring substrate may be used as a substrate for mounting a semiconductor element (see, for example, Patent Documents 1 and 2). The ceramic wiring substrate includes a ceramic substrate and an oxygen-free copper plate that is provided on the ceramic substrate and has a wiring pattern (copper wiring) that is removed by, for example, etching.

JP 2001-217362 A Japanese Patent Laid-Open No. 10-4156

  By repeating energization and de-energization of the semiconductor element mounted on the ceramic wiring board, the semiconductor element repeats heat generation and heat dissipation, and as a result, the ceramic wiring board also repeats temperature increase and decrease. Since the linear expansion coefficient of the ceramic substrate and the oxygen-free copper plate is different, when the ceramic wiring substrate repeatedly rises and falls, the difference between the thermal expansion of the ceramic substrate and the oxygen-free copper plate causes a difference between the ceramic substrate and the oxygen-free copper plate. Stress (thermal stress) is repeatedly generated at the interface (bonding interface). When such a thermal stress is generated, the oxygen-free copper plate is plastically deformed, thereby relaxing the influence of the thermal stress on the ceramic wiring board. However, when the ceramic wiring board repeats temperature rise and fall, the oxygen-free copper plate is gradually cured, and the oxygen-free copper plate becomes difficult to be plastically deformed. As a result, problems such as cracking of the ceramic substrate and separation of the oxygen-free copper plate and the ceramic substrate from the interface may occur.

  The present invention provides a technique capable of suppressing cracking of a ceramic substrate and separation of an oxygen-free copper plate and a ceramic substrate from an interface even when the ceramic wiring substrate is repeatedly heated and lowered. For the purpose.

According to one aspect of the invention,
It is formed into a flat plate shape by rolling,
By heating at 200 ° C. for 30 minutes, the Vickers hardness decreases to HV80 or less,
Provided is an oxygen-free copper plate having a characteristic that 0.2% proof stress after heating at 800 ° C. or higher and 1080 ° C. or lower for 5 minutes or longer is within 16 MPa or lower.

According to another aspect of the invention,
Oxygen concentration is 0.0010 mass% or less, phosphorus concentration is 0.0002 mass% or less, sulfur concentration is 0.0010 mass% or less, tin concentration is 0.0005 mass% or less, silver concentration Is 0.0010 mass% or less, and cold rolling with a workability of 40% or less at one time is performed on a rolled material formed of oxygen-free copper having a copper concentration of 99.99 mass% or more. , Having a cold rolling process that is performed a plurality of times so that the total processing degree is 90% or more,
The characteristic that Vickers hardness decreases to HV80 or less by heating at 200 ° C for 30 minutes, and 0.2% proof stress after heating at 800 ° C or more and 1080 ° C or less for 5 minutes or more is less than 16MPa. There is provided a method for producing an oxygen-free copper plate that forms an oxygen-free copper plate having the following.

According to yet another aspect of the invention,
A ceramic substrate;
A wiring pattern bonded on at least one main surface of the ceramic substrate;
The wiring pattern is
Heating at 200 ° C. for 30 minutes reduces the Vickers hardness to HV80 or lower, and 0.2% proof stress after heating at 800 ° C. or higher and 1080 ° C. or lower for 5 minutes or higher is 16 MPa or lower. A ceramic wiring board formed of an oxygen-free copper plate is provided.

  According to the present invention, even if the ceramic wiring board repeats temperature rising and cooling, a technique that can suppress the ceramic substrate from cracking or peeling of the oxygen-free copper plate and the ceramic substrate from the interface. Can be provided.

<One Embodiment of the Present Invention>
(1) Configuration of Ceramic Wiring Board First, the configuration of the ceramic wiring board according to one embodiment of the present invention will be described.

  The ceramic wiring board according to the present embodiment includes a ceramic substrate having a predetermined thickness (for example, 0.5 mm) and an oxygen-free copper plate provided on the ceramic substrate. The ceramic substrate and the oxygen-free copper plate are bonded (bonded) via a brazing material, for example. This bonding is performed by heat treatment in which a laminated body of a ceramic substrate, a brazing material, and an oxygen-free copper plate is heated in a furnace under predetermined conditions (for example, at a temperature of 800 ° C. or higher and 1080 ° C. or lower for 5 minutes or longer). A predetermined part of the oxygen-free copper plate bonded to the ceramic substrate is removed by, for example, etching, so that the oxygen-free copper plate becomes a wiring pattern (copper wiring).

  As the ceramic substrate, a ceramic sintered body mainly composed of aluminum nitride (AlN), silicon nitride (SiN), or the like can be used.

  As a brazing material, a metal such as silver (Ag), copper (Cu), tin (Sn), indium (In), titanium (Ti), molybdenum (Mo), or an alloy containing at least one of these metals. Can be used.

(2) Configuration of oxygen-free copper plate Hereinafter, the configuration of the oxygen-free copper plate according to one embodiment of the present invention will be described. The oxygen-free copper plate according to this embodiment can be suitably used for the above-described ceramic wiring board, for example.

  The oxygen-free copper plate according to the present embodiment has a characteristic of causing a decrease in Vickers hardness by heating and suppressing an increase in 0.2% proof stress after heating under a predetermined condition. Specifically, the oxygen-free copper plate according to the present embodiment has a characteristic that the Vickers hardness decreases to HV80 or less by heating at a temperature of 200 ° C for 30 minutes, and 5% at a temperature of 800 ° C to 1080 ° C. It has two characteristics, that is, 0.2% proof stress after heating for more than a minute falls within 16 MPa. The oxygen-free copper plate according to this embodiment has a Vickers hardness of HV125 or higher before being heated at a temperature of 200 ° C. for 30 minutes, and before being heated at a temperature of 800 ° C. or higher and 1080 ° C. or lower for 5 minutes or longer. The 0.2% proof stress is 400 MPa or more.

  The 0.2% proof stress is a stress that causes a permanent strain of 0.2% in the material (oxygen-free copper plate), and is a value that is used as a standard for a stress that does not cause a large plastic deformation. That is, it can be said that an oxygen-free copper plate having a high 0.2% yield strength is not easily plastically deformed, and an oxygen-free copper plate having a low 0.2% yield strength is easily plastically deformed (plastically deforms even at a low stress).

  The decrease in Vickers hardness of an oxygen-free copper plate due to heating is due to the phenomenon that atoms diffuse (move) in the oxygen-free copper plate to reduce lattice defects (recovery) and the number of lattice defects due to rearrangement of the diffused atoms. This occurs due to a phenomenon (recrystallization) that changes to a crystal structure (reduction of lattice defects). For this reason, for example, an oxygen-free copper plate whose Vickers hardness is reduced by heating at a low temperature of 200 ° C. can be said to be a copper plate that tends to cause recovery and recrystallization, and to reduce lattice defects.

When the temperature of the above-described ceramic wiring board provided with the oxygen-free copper plate is raised, the oxygen-free copper plate is plastically deformed by the stress generated by the thermal expansion difference between the oxygen-free copper plate and the ceramic substrate. In addition, the linear expansion coefficient of oxygen-free copper is 1.7 × 10 ⁻⁵ / K, and the linear expansion coefficient of ceramic is 0.3 to 0.8 × 10 ⁻⁵ / K. Hereinafter, in the present specification, the above-described stress generated when the temperature of the ceramic wiring board is raised is also referred to as “thermal stress”. In a ceramic wiring board, the oxygen-free copper plate is plastically deformed in this way, so that the influence of thermal stress on the ceramic wiring board is alleviated. As a result, the ceramic substrate breaks or the oxygen-free copper plate and the ceramic substrate peel off. To suppress. Hereinafter, in this specification, the effect of alleviating the influence of thermal stress in the ceramic wiring board due to plastic deformation of the oxygen-free copper plate is also referred to as “relaxation effect”.

  However, when the oxygen-free copper plate is plastically deformed, lattice defects are introduced into the oxygen-free copper plate. Thereby, an oxygen-free copper plate hardens | cures and the 0.2% yield strength of an oxygen-free copper plate rises. The 0.2% yield strength of the oxygen-free copper plate increases as the number of times that the oxygen-free copper plate undergoes plastic deformation increases. As described above, when the 0.2% proof stress of the oxygen-free copper plate is increased, the oxygen-free copper plate is difficult to be plastically deformed, so that the above-described relaxation effect is hardly obtained. As a result, when the ceramic wiring substrate repeats heating and cooling, the ceramic substrate may be broken or the oxygen-free copper plate and the ceramic substrate may be peeled off.

  As described above, the oxygen-free copper plate according to the present embodiment has a characteristic that the Vickers hardness is lowered to HV80 or less by heating at a temperature of 200 ° C. for 30 minutes. Thereby, since lattice defects introduced into the oxygen-free copper plate (in the material) when plastically deformed are reduced, even if the oxygen-free copper plate is plastically deformed, the 0.2% yield strength is hardly increased. When such an oxygen-free copper plate is used for the above-described ceramic wiring board, even if the ceramic wiring board is repeatedly heated and lowered, the oxygen-free copper plate will be plastically deformed for a long period of time, and the above-mentioned relaxation effect will be maintained for a long time. Can be obtained.

  It should be noted that an oxygen-free copper plate whose Vickers hardness does not decrease to HV80 or less even when heated at a temperature of 200 ° C. for 30 minutes (exceeding HV80) is sufficient to prevent lattice defects introduced when the oxygen-free copper plate is plastically deformed. Sometimes it cannot be reduced. For this reason, if the oxygen-free copper plate is plastically deformed, the 0.2% proof stress may increase, and the period during which the above-described relaxation effect is obtained may be shortened.

  Further, as described above, the oxygen-free copper plate according to the present embodiment has a characteristic that the 0.2% proof stress after heating for 5 minutes or more at a temperature of 800 ° C. or higher and 1080 ° C. or lower falls within 16 MPa. That is, the oxygen-free copper plate according to the present embodiment has a characteristic that the 0.2% proof stress after performing the above-described heat treatment for forming a ceramic wiring board, for example, is 16 MPa or less.

  As a result, the oxygen-free copper plate is plastically deformed with a stress as low as the above-described thermal stress, for example. If the 0.2% proof stress after heating exceeds 16 MPa under the above-mentioned predetermined conditions, the oxygen-free copper plate may not be plastically deformed by a stress about the above-described thermal stress.

  Impurity components in oxygen-free copper affect the progress of the decrease in Vickers hardness due to heating and the increase in 0.2% yield strength after heating under the above-mentioned predetermined conditions. In particular, each impurity component of oxygen (O), phosphorus (P), sulfur (S), Sn, and Ag causes a decrease in Vickers hardness due to heating, and 0.2% yield strength after heating under the above-mentioned predetermined conditions. The inventor of the present application has confirmed that there is a great influence on the increase of the above. By setting the concentration (content) of these impurity components to a predetermined value or less, the above two characteristics are obtained.

  Specifically, the O concentration is, for example, 0.0010 mass% or less, preferably 0.0005 mass% or less, the P concentration is, for example, 0.0002 mass% or less, preferably 0.0001 mass% or less, and S The concentration is, for example, 0.0010 mass% or less, preferably 0.0005 mass% or less, the Sn concentration is, for example, 0.0005 mass% or less, preferably 0.0003 mass% or less, and the Ag concentration is, for example, 0.0010. The mass is not more than mass%, preferably not more than 0.0005 mass%, and the Cu concentration is, for example, 99.99 mass% or more. The oxygen-free copper plate is preferably made of oxygen-free copper having such a composition, for example.

  O concentration exceeds 0.0010 mass%, P concentration exceeds 0.0002 mass%, S concentration exceeds 0.0010 mass%, Sn concentration exceeds 0.0005 mass%, Ag concentration If it exceeds 0.0010% by mass, the oxygen-free copper plate may not have the above two characteristics.

  Further, when the concentration of the above-described impurity component exceeds a predetermined value, the Cu concentration may be less than 99.99% by mass, for example. For this reason, the oxygen-free copper plate may not have the above-mentioned two characteristics, or in the ceramic wiring board, there may be many places where the oxygen-free copper plate and the ceramic substrate are not bonded, that is, the bonding state may be poor. .

  As described above, in this embodiment, predetermined requirements are imposed on the O concentration, P concentration, S concentration, Sn concentration, Ag concentration, and Cu concentration in the oxygen-free copper plate. In addition, it described about the upper limit of the impurity component of O concentration, P concentration, S concentration, Sn concentration, and Ag concentration in an oxygen-free copper plate, and the minimum of Cu concentration. However, there is no particular limitation on the lower limit of the impurity component concentration and the upper limit of the Cu concentration. The concentration of the above-described impurity component is preferably zero, that is, it is preferable that the oxygen-free copper plate does not contain O, P, S, Sn, and Ag components, and the Cu concentration is 100% by mass, It is preferable that no impurity component is contained in the oxygen copper plate. However, since the above-mentioned impurity components may be inevitably mixed in the oxygen-free copper plate (oxygen-free copper) in the process of forming the oxygen-free copper plate, it is difficult to precisely control the concentration of these components. is there. For these reasons, the O concentration, P concentration, S concentration, Sn concentration, and Ag concentration in the oxygen-free copper plate are, for example, 0.0001% by mass or more, and the Cu concentration is, for example, 99.999% by mass or less. Is common.

  The oxygen-free copper plate is formed into a flat plate shape by rolling the oxygen-free copper ingot having the above composition. The oxygen-free copper plate may be formed to have a thickness of, for example, 100 μm or more, preferably 100 μm or more and 1 mm or less.

  If the thickness of the oxygen-free copper plate is less than 100 μm, heat dissipation may be insufficient. By setting the thickness of the oxygen-free copper plate to 100 μm or more, sufficient heat dissipation can be obtained, and the oxygen-free copper plate can be suitably used as a wiring material for the ceramic wiring board. The greater the thickness of the oxygen-free copper plate, the higher the heat dissipation.

  However, if the thickness of the oxygen-free copper plate is too large relative to the thickness of the ceramic substrate, the influence of the difference in thermal expansion due to the difference between the linear expansion coefficient of ceramic and the linear expansion coefficient of oxygen-free copper in the ceramic wiring board described above. May increase, and the generated thermal stress may increase. As a result, even if the oxygen-free copper plate has the above-mentioned two characteristics, if the ceramic wiring substrate repeats heating and cooling, the ceramic substrate may break or the ceramic substrate and the oxygen-free copper plate may peel off. There are things to do. This can be solved by setting the thickness of the oxygen-free copper plate to 1 mm or less, and the influence of the difference in thermal expansion between the ceramic substrate and the oxygen-free copper can be reduced in the ceramic wiring substrate.

(3) Method for Producing Oxygen-Free Copper Plate Next, the method for producing an oxygen-free copper plate according to the present embodiment will be described with reference to the melt casting method.

  The oxygen-free copper plate according to the present embodiment can be formed by sequentially performing an electrolytic purification process, a melt casting process, a hot rolling process, and a cold rolling process.

(Electrolytic purification process)
In the electrolytic refining step, electrolytic copper which is a raw material for dissolution in the melting and casting step is formed by electrolytically refining crude copper melted from copper ore. The electrolytic copper contains impurity components such as O, P, S, Sn, and Ag. Among these impurity components, the concentrations of Sn and Ag can be reduced in this step, and it is effective to reduce them in this step. For example, the concentration of Sn and Ag contained in electrolytic copper is repeated several times (n times (n is an integer of 2 or more)), such as electrolytic purification once again using electrolytic copper once formed by electrolytic purification. This can be reduced. Thus, Sn in the electrolytic copper to a concentration at which the Sn concentration of the finally formed oxygen-free copper plate can be 0.0005% by mass or less and the Ag concentration can be 0.0010% by mass or less, Reduce Ag concentration.

(Melting casting process)
The electrolytic copper whose Sn and Ag concentrations have been reduced to a predetermined value through the above-described electrolytic purification process is melted using, for example, a high-frequency melting furnace to produce a molten copper, and the molten copper is poured into a mold and cooled. Then, an ingot (an oxygen-free copper ingot) having a predetermined composition is cast. Among the impurity components contained in the electrolytic copper, the concentrations of O, P, and S can be reduced in the melt casting process.

  In order to reduce the concentration of O, P, and S in electrolytic copper, first, electrolytic copper is melted in an atmosphere in which oxygen exists (for example, in an atmospheric atmosphere) to form a molten copper, and then the molten copper It is preferable to coat the surface with charcoal, for example.

O can be taken in the molten metal by melting electrolytic copper in an atmosphere where oxygen is present to form a molten copper. Thereby, P and S contained in the electrolytic copper (that is, contained in the molten copper) and O in the molten metal are reacted (P and S are oxidized), and P is converted into, for example, dipentapentoxide. Phosphorus (P ₂ O ₅ ) gas can be used, and S can be removed from the molten metal using, for example, sulfur dioxide (SO ₂ ) gas. As a result, the P and S concentrations in the ingot can be reduced to a concentration at which the P concentration of the oxygen-free copper plate can be 0.0002 mass% or less and the S concentration can be 0.0005 mass% or less, for example. .

  In addition, by covering the surface of the molten copper with charcoal, carbon (C) contained in the charcoal and O in the molten metal can be reacted to remove O from the molten metal as CO gas. Thereby, O concentration in an ingot can be reduced to the density | concentration which can make O concentration of an oxygen-free copper plate into 0.0010 mass% or less, for example. In addition, from the viewpoint of reliably reducing the O concentration of the oxygen-free copper plate, it is preferable to remove the oxide on the surface of the molten metal before coating the surface of the molten metal with charcoal.

  As a result, an oxygen-free copper ingot in which the O concentration, the P concentration, the S concentration, the Sn concentration, and the Ag concentration are equal to or less than the above-described predetermined values and the Cu concentration is, for example, 99.99% by mass or more can be cast. .

(Hot rolling process)
In a state where the ingot is heated to a high temperature (for example, 750 ° C. or more and 950 ° C. or less), the ingot is hot-rolled to form a hot-rolled material having a predetermined thickness (for example, 10 mm). The hot-rolled material in this specification refers to an oxygen-free copper plate formed by performing a hot rolling process.

(Cold rolling process)
After the hot rolling process is completed, the hot rolled material is subjected to predetermined cold rolling a plurality of times to form a flat oxygen-free copper plate having a predetermined thickness (for example, 100 μm or more). In the cold rolling process, cold rolling is performed so that recrystallization does not occur in the material to be rolled. Specifically, cold rolling (rolling pass) in which the degree of work r at one time is 40% or less is performed a plurality of times so that the total degree of work R is 90% or more.

The working degree r of one cold rolling (one rolling pass) can be obtained from the following (Formula 1). In (Equation 1), t ₀ is the thickness of the material to be rolled before one cold rolling, and t is the thickness of the material to be rolled after one cold rolling.
(Formula 1)
Degree of processing r (%) = {(t ₀ −t) / t ₀ } × 100

  By setting the working degree r of one cold rolling to 40% or less, the amount of processing heat generated by performing cold rolling can be reduced. Accordingly, it is possible to suppress the material to be rolled from being heated to a temperature at which recrystallization or the like occurs due to processing heat while performing the cold rolling a plurality of times to form the oxygen-free copper plate.

The total processing degree R is obtained from the following (Formula 2). In (Expression 2), T ₀ is the thickness of the hot-rolled material, and T is the rolled material (that is, oxygen-free) after cold rolling is performed a predetermined number of times (after the cold rolling process is completed). Copper plate).
(Formula 2)
Total processing rate R (%) = {(T ₀ −T) / T ₀ } × 100

  By increasing the total working degree R, the amount of strain introduced into the oxygen-free copper plate increases, and a large amount of strain can be accumulated in the oxygen-free copper plate. As a result, the 0.2% yield strength of the oxygen-free copper plate is unlikely to increase due to the heat treatment under a predetermined condition (for example, at a temperature of 800 ° C. or higher and 1080 ° C. or lower for 5 minutes or more) that is performed to bond the ceramic substrate and the oxygen-free copper plate. Become. Specifically, by setting the total workability R to 90% or more, the 0.2% yield strength of the oxygen-free copper plate after heating (heat treatment) under a predetermined condition can be kept to 16 MPa or less.

  In the cold rolling step, it is preferable to perform cold rolling continuously a plurality of times without sandwiching annealing. That is, it is preferable to accumulate strain in the material to be rolled without performing any annealing for recovering the workability of the material to be rolled which is lowered by rolling. Thereby, the raise of the 0.2% yield strength of the oxygen-free copper plate after heating on predetermined conditions can be suppressed reliably.

(4) Effects According to the Present Embodiment According to the present embodiment, one or more effects described below are exhibited.

(A) By having the property that the Vickers hardness decreases to HV80 or less by heating at 200 ° C. for 30 minutes, even if the oxygen-free copper plate is plastically deformed, the 0.2% yield strength is unlikely to increase. The oxygen-free copper plate becomes plastically deformed for a long time. Thereby, the above-mentioned relaxation effect can be obtained for a long time. For this reason, the ceramic wiring board can prevent the ceramic board from cracking or peeling of the oxygen-free copper plate and the ceramic board for a long time even if the temperature rise and fall are repeated, and the reliability of the ceramic wiring board is improved. Can be maintained for a long time. Moreover, the fall of Vickers hardness can also be advanced at the low temperature of 200 degreeC.

  In addition, in the conventional general oxygen-free copper plate, the Vickers hardness after heating for 30 minutes at a temperature of 200 ° C. is HV100 or less, but not HV80 or less, and the conventional general oxygen-free copper plate In order to reduce the Vickers hardness after heating to HV80 or less, the present inventor has confirmed that it is necessary to heat at a temperature of 220 ° C. or higher for 30 minutes.

(B) Moreover, since it has the characteristic that the 0.2% proof stress after heating for 5 minutes or more under the temperature of 800 degreeC or more and 1080 degrees C or less is settled in 16 MPa or less, it is stress lower than the conventional oxygen-free copper plate (for example, The oxygen-free copper plate undergoes plastic deformation at a stress as low as the thermal stress described above. Thereby, the above-mentioned relaxation effect can be obtained with certainty, and the reliability of the ceramic wiring board can be reliably maintained.

  In addition, the conventional general oxygen-free copper plate has a 0.2% yield strength of 20 to 30 MPa after heating for 5 minutes at a temperature of 800 ° C. or higher and 1080 ° C. or lower. On the other hand, in the oxygen-free copper plate according to the present embodiment, an increase in 0.2% proof stress after heating is suppressed as compared with the conventional oxygen-free copper plate.

(C) O concentration, P concentration, S concentration, Sn concentration, and Ag concentration in the oxygen-free copper plate are set to the above-described predetermined ranges, respectively, and the Cu concentration is set to 99.99% by mass or more. The copper plate having the above-mentioned two characteristics can be obtained.

(D) Since the predetermined heat dissipation can be ensured by setting the thickness of the oxygen-free copper plate to 100 μm or more, a large-current semiconductor element (for example, a large-current switching semiconductor element) is provided on the ceramic wiring board having the oxygen-free copper plate. ) Can be installed.

(E) In the cold rolling process, cold rolling in which the degree of work r at one time is 40% or less is performed a plurality of times so that the total degree of work R is 90% or more. It is possible to form an oxygen-free copper plate that can suppress an increase in 2% yield strength. That is, it is possible to form an oxygen-free copper plate having a characteristic that the 0.2% proof stress after heating for 5 minutes at a temperature of 800 ° C. or higher and 1080 ° C. or lower is within 16 MPa.

(F) The oxygen-free copper plate according to the present embodiment is particularly effective when used for a ceramic wiring board on which a high-current semiconductor element is mounted. Since a larger current flows through the semiconductor element for large current than other semiconductor elements, the ceramic wiring board on which the semiconductor element for large current is mounted is likely to have a higher temperature. In such a ceramic wiring substrate, the stress generated at the interface between the oxygen-free copper plate and the ceramic substrate is further increased by repeating the temperature increase and the temperature decrease. The ceramic wiring board formed using the oxygen-free copper plate according to the present embodiment suppresses the occurrence of cracks in the ceramic substrate and separation of the oxygen-free copper plate and the ceramic substrate even when such a large stress occurs. The reliability of the ceramic wiring board can be improved.

<Other Embodiments of the Present Invention>
As mentioned above, although one Embodiment of this invention was described concretely, this invention is not limited to the above-mentioned embodiment, In the range which does not deviate from the summary, it can change suitably.

  In the above-described embodiment, the molten metal is generated using the high-frequency melting furnace, but the present invention is not limited to this. For example, various melting furnaces that can melt a raw material by heating to produce a molten metal can be used.

  In the above-described embodiment, the case where the oxygen-free copper plate is used for the wiring material of the ceramic wiring board has been described, but the present invention is not limited to this.

  Next, examples of the present invention will be described, but the present invention is not limited thereto.

<Production of sample>
As shown below, oxygen-free copper plates of Samples 1 to 14 were prepared.

(Sample 1)
In Sample 1, high-purity electrolytic copper whose Sn and Ag concentrations have been reduced to a predetermined value through a predetermined electrolytic purification process is put into a crucible (graphite crucible) included in a high-frequency melting furnace, and the high-frequency melting furnace is used. The inside of the crucible was heated in an air atmosphere to dissolve electrolytic copper, and a molten copper (oxygen-free copper) was melted. At this time, P and S contained in the electrolytic copper react with O taken into the molten metal by melting in the atmospheric air, and P and S are respectively reacted with P ₂ O ₅ gas and SO. _Two gases were used and removed from the molten metal. Thereafter, the surface of the molten metal was covered with charcoal, C contained in the charcoal was reacted with O in the molten metal, and O was removed from the molten metal as CO gas. The molten metal was poured into a mold and cooled to cast an oxygen-free copper ingot having a predetermined shape. The Cu concentration (Cu purity) of this ingot was 99.996% by mass.

  The obtained ingot was hot rolled under predetermined conditions to form a hot rolled material having a thickness of 10 mm (hot rolling step). With respect to the obtained hot-rolled material, cold rolling in which the degree of work r at one time is 35% or less (that is, the maximum degree of one-pass work is 35%) is set to a total work degree R without sandwiching annealing. An oxygen-free copper plate having a thickness of 0.8 mm was formed continuously for a plurality of times so as to be 92% (cold rolling step). This oxygen-free copper plate was designated as Sample 1.

(Samples 2-12)
In each of Samples 2 to 12, P, S, Sn, and P in the oxygen-free copper melt were prepared so that the composition of the ingot cast in the casting process, that is, the composition of the oxygen-free copper plate was as shown in Table 1 below. A small amount of a predetermined element of Ag was added to form an ingot. Otherwise, an oxygen-free copper plate was formed in the same manner as Sample 1 described above. These were designated as Samples 2 to 12, respectively.

(Samples 13 and 14)
Sample 13 was subjected to at least one cold rolling in which the working degree r exceeded 40% in the cold rolling performed a plurality of times in the cold rolling step. Specifically, the maximum degree of one-pass cold rolling in the cold rolling process was 44%. In Sample 14, a hot rolled material having a thickness of 7 mm was formed in the hot rolling process. In the cold rolling process, the total workability R was set to less than 90%. Specifically, in the cold rolling step, cold rolling with a maximum workability of 35% was performed a plurality of times so that the total workability R was 88.6%. Otherwise, an oxygen-free copper plate was formed in the same manner as Sample 1 described above. These were designated as Samples 13 and 14, respectively.

<Creation of ceramic wiring board>
Next, using the samples 1 to 14, a ceramic wiring board was prepared.

  First, a ceramic sintered body having a thickness of 0.5 mm mainly composed of AlN was prepared as a ceramic substrate. This ceramic substrate was heat-treated under conditions of 800 ° C. or higher and 900 ° C. or lower, and a cleaning process was performed to remove organic substances adhering to the surface of the ceramic substrate. Thereafter, a paste-like brazing material was applied to one surface of the ceramic substrate by a screen printing method so as to have a thickness of 0.03 mm. The brazing material used was 70% by mass of Ag, 28% by mass of Cu, and 2% by mass of Ti. Then, the oxygen-free copper plates of Samples 1 to 14 are respectively arranged on the brazing material, and the laminate of each sample (oxygen-free copper plate), the ceramic substrate and the brazing material is heated to 850 ° C. in a vacuum and held for 5 minutes. Then, each sample and the ceramic substrate were bonded together via a brazing material to prepare a ceramic wiring substrate.

  In Table 1, the values of P concentration, S concentration, Sn concentration, and Ag concentration are values obtained by measuring the P concentration, S concentration, Sn concentration, and Ag concentration in the ingot by plasma emission spectroscopy (ICP-AES), respectively. It is. In Table 1, the value of the O concentration is a value measured by a method of measuring CO generated when a test piece collected from an ingot is melted in a crucible by an infrared absorption method.

  In Table 1, “total working degree after hot rolling (%)” means the total working degree of rolling performed after the hot rolling process is completed, that is, cold rolling performed in the cold rolling process.

  In Table 1, “Vickers hardness (HV) after heating at 200 ° C. for 30 minutes” is obtained by heating test pieces for measuring Vickers hardness taken from samples 1 to 14 at a temperature of 200 ° C. for 30 minutes, respectively. , Based on a micro Vickers hardness test method based on JIS Z2244, a value measured as a test load of 0.98 N.

  In Table 1, “0.2% proof stress (MPa) after heating at 800 ° C. × 5 minutes” is 5% of test pieces for measuring 0.2% proof stress collected from samples 1 to 14 at a temperature of 800 ° C. It is a value measured by performing a tensile test based on the offset method shown in JIS Z2241 (i.e., 0.2% yield strength) after heating for a minute.

  In Table 1, “bonded state” is an evaluation of the bonded state between each sample (oxygen-free copper plate) and the ceramic substrate in each ceramic wiring board formed using the oxygen-free copper plates of Samples 1-14. Specifically, for each ceramic wiring board described above, the unbonded ratio of the bonding interface between each sample and the ceramic substrate was determined using an ultrasonic microscope (Fine SAT III manufactured by Hitachi Power Solutions). The unbonded rate is the ratio of the area of the unbonded portion to the area of the bonding interface. Evaluation of a sample having an unbonded rate of less than 10% was “◯”, and evaluation of a sample having an unbonded rate of 10% or more was set to “x”.

  In Table 1, “cracking / peeling evaluation” means that after performing a heat cycle test on each ceramic wiring board formed using samples 1 to 14, cracks (cracks) have not occurred in the ceramic board. It is evaluated whether there is a portion where the oxygen-free copper plate is peeled off from the ceramic substrate. The heat cycle test was performed by alternately charging each ceramic wiring board into a liquid bath of a cryogen mixed with ethanol of -65 ° C and dry ice and a liquid bath of a 150 ° C oil bath. In the heat cycle test, each ceramic wiring board was put in a cryogen bath for 5 minutes and then put in an oil bath bath for 5 minutes. This cycle was repeated 500 times. If the ceramic substrate is not cracked and the oxygen-free copper plate is not peeled off from the ceramic substrate, the sample is evaluated as “◯”, and the ceramic substrate is cracked or the oxygen-free copper plate is a ceramic substrate. The evaluation of the sample having a part that peeled off from the sample was “x”.

  In Table 1, “total evaluation” is a comprehensive evaluation of the above-described evaluation of the bonding state and evaluation of cracking / peeling. For the ceramic wiring board formed using each sample, if the evaluation of the bonding state is “◯” and the evaluation of cracking / peeling is also “◯”, the overall evaluation is “◎”. When either or both of the bonding state and crack / peel evaluation were “x”, the overall evaluation was “x”.

<Evaluation results>
From samples 1-6, Vickers hardness decreases to HV80 or less by heating at 200 ° C for 30 minutes, and 0.2% proof stress after heating at 800 ° C or more and 1080 ° C or less for 5 minutes or more. An oxygen-free copper plate that has a characteristic that can be kept below 16 MPa, the ceramic substrate is cracked or the ceramic substrate and the oxygen-free copper plate (bonding interface) are peeled off even if the temperature is raised and lowered repeatedly. It was confirmed that can be suppressed.

  Further, from Samples 1 to 6, O concentration is 0.0010 mass% or less, P concentration is 0.0002 mass% or less, S concentration is 0.0010 mass% or less, Sn concentration is 0.0005 mass% or less, Ag concentration The oxygen-free copper plate having a Cu content of 0.0010% by mass or less and a Cu concentration of 99.99% by mass or more has a Vickers hardness of HV80 or less when heated at a temperature of 200 ° C. for 30 minutes. It was confirmed that the 0.2% proof stress after heating for 5 minutes or more at a temperature of ℃ or less was within 16 MPa or less.

  Further, from samples 1 to 6, in the cold rolling process, cold rolling with a single workability r (maximum one-pass workability) of 40% or less is performed so that the total workability R becomes 90% or more. By performing multiple times, the Vickers hardness after heating at 200 ° C. for 30 minutes decreases to HV80 or less, and the 0.2% proof stress after heating at 800 ° C. to 1080 ° C for 5 minutes or more is 16 MPa or less. It was confirmed that an oxygen-free copper plate having the characteristics to fit could be formed.

  From Samples 7 to 12, the P concentration exceeds 0.0002 mass%, the S concentration exceeds 0.0010 mass%, the Sn concentration exceeds 0.0005 mass%, or the Ag concentration is 0.0010 mass%. Vickers after heating at 200 ° C. for 30 minutes if the oxygen-free copper plate has an oxygen concentration exceeding 0.0010 mass%, an impurity concentration is high, and a Cu concentration is less than 99.99%. It was confirmed that the hardness may exceed HV80, or the 0.2% proof stress after heating at 800 ° C. for 5 minutes may exceed 16 MPa.

  From samples 13 and 14, in the cold rolling process, when cold rolling with a single workability r exceeding 40% is performed, or when the total workability R becomes less than 90%, heating is performed at 200 ° C. for 30 minutes. It was confirmed that the Vickers hardness after heating exceeded HV80, and the 0.2% proof stress after heating at 800 ° C. for 5 minutes may exceed 16 MPa.

  From samples 7 to 13, using an oxygen-free copper plate whose Vickers hardness after heating at 200 ° C. for 30 minutes exceeds HV80 or 0.2% proof stress after heating at 800 ° C. for 5 minutes exceeds 16 MPa. It was confirmed that the formed ceramic wiring board sometimes cracks the ceramic substrate and peels the ceramic substrate and the oxygen-free copper plate when the temperature is raised and lowered repeatedly.

  In addition, it was confirmed from Sample 12 that when the Cu concentration was less than 99.99% by mass, there were many places where the oxygen-free copper plate and the ceramic substrate were not joined in the ceramic wiring substrate.

<Preferred embodiment>
Hereinafter, preferred embodiments of the present invention will be additionally described.

[Appendix 1]
According to one aspect of the invention,
It is formed into a flat plate shape by rolling,
By heating at 200 ° C. for 30 minutes, the Vickers hardness decreases to HV80 or less,
Provided is an oxygen-free copper plate having a characteristic that 0.2% proof stress after heating at 800 ° C. or higher and 1080 ° C. or lower for 5 minutes or longer is within 16 MPa or lower.

[Appendix 2]
The oxygen-free copper plate of Appendix 1, preferably,
The Vickers hardness before heating for 30 minutes at a temperature of 200 ° C. is HV125 or more.

[Appendix 3]
An oxygen-free copper plate according to appendix 1 or 2,
The 0.2% yield strength before heating for 5 minutes or more at a temperature of 800 ° C. or more and 1080 ° C. or less is 400 MPa or more.

[Appendix 4]
An oxygen-free copper plate according to any one of appendices 1 to 3,
Oxygen concentration is 0.0010 mass% or less, phosphorus concentration is 0.0002 mass% or less, sulfur concentration is 0.0010 mass% or less, tin concentration is 0.0005 mass% or less, silver concentration Is 0.0010 mass% or less, and the copper concentration is 99.99 mass% or more.

[Appendix 5]
An oxygen-free copper plate according to any one of appendices 1 to 4, preferably,
The thickness is 100 μm or more.

[Appendix 6]
Appendix 5 An oxygen-free copper plate, preferably,
The thickness is 1 mm or less.

[Appendix 7]
According to another aspect of the invention,
Oxygen concentration is 0.0010 mass% or less, phosphorus concentration is 0.0002 mass% or less, sulfur concentration is 0.0010 mass% or less, tin concentration is 0.0005 mass% or less, silver concentration Is 0.0010 mass% or less, and cold rolling with a workability of 40% or less at one time is performed on a rolled material formed of oxygen-free copper having a copper concentration of 99.99 mass% or more. , Having a cold rolling process that is performed a plurality of times so that the total processing degree is 90% or more,
The characteristic that Vickers hardness decreases to HV80 or less by heating at 200 ° C for 30 minutes, and 0.2% proof stress after heating at 800 ° C or more and 1080 ° C or less for 5 minutes or more is less than 16MPa. There is provided a method for producing an oxygen-free copper plate that forms an oxygen-free copper plate having the following.

[Appendix 8]
The method for producing an oxygen-free copper plate according to appendix 7, preferably,
In the cold rolling process,
Strain is accumulated in the material to be rolled without annealing.

[Appendix 9]
According to yet another aspect of the invention,
A ceramic substrate;
A wiring pattern bonded on at least one main surface of the ceramic substrate;
The wiring pattern is
Heating at 200 ° C. for 30 minutes reduces the Vickers hardness to HV80 or lower, and 0.2% proof stress after heating at 800 ° C. or higher and 1080 ° C. or lower for 5 minutes or higher is 16 MPa or lower. A ceramic wiring board formed of an oxygen-free copper plate is provided.

Claims (5)

It is formed into a flat plate shape by rolling,
By heating at 200 ° C. for 30 minutes, the Vickers hardness decreases to HV80 or less,
An oxygen-free copper plate having a characteristic that 0.2% proof stress after heating at 800 ° C. or higher and 1080 ° C. or lower for 5 minutes or longer is within 16 MPa. Oxygen concentration is 0.0010 mass% or less, phosphorus concentration is 0.0002 mass% or less, sulfur concentration is 0.0010 mass% or less, tin concentration is 0.0005 mass% or less, silver concentration The oxygen-free copper plate according to claim 1, wherein 0.0010 mass% or less and the copper concentration is 99.99 mass% or more. The oxygen-free copper plate according to claim 1 or 2, wherein the thickness is 100 µm or more. Oxygen concentration is 0.0010 mass% or less, phosphorus concentration is 0.0002 mass% or less, sulfur concentration is 0.0010 mass% or less, tin concentration is 0.0005 mass% or less, silver concentration Is 0.0010 mass% or less, and cold rolling with a workability of 40% or less at one time is performed on a rolled material formed of oxygen-free copper having a copper concentration of 99.99 mass% or more. , Having a cold rolling process that is performed a plurality of times so that the total processing degree is 90% or more,
The characteristic that Vickers hardness decreases to HV80 or less by heating at 200 ° C for 30 minutes, and 0.2% proof stress after heating at 800 ° C or more and 1080 ° C or less for 5 minutes or more is less than 16MPa. The manufacturing method of the oxygen-free copper plate which forms the oxygen-free copper plate which has this. A ceramic substrate;
A wiring pattern bonded on at least one main surface of the ceramic substrate;
The wiring pattern is
Heating at 200 ° C. for 30 minutes reduces the Vickers hardness to HV80 or lower, and 0.2% proof stress after heating at 800 ° C. or higher and 1080 ° C. or lower for 5 minutes or higher is 16 MPa or lower. Ceramic wiring board made of oxygen-free copper plate.