JP5743503B2 - Brazing material, circuit board using the same, and electronic device - Google Patents

Description

  The present invention relates to a brazing material used when a circuit member is bonded to one main surface of a ceramic substrate and a heat radiating member is bonded to the other main surface. The present invention also relates to a circuit board in which a circuit member and a heat radiating member are bonded to a ceramic substrate via a bonding layer made of this brazing material, and an electronic device in which an electronic component is mounted on the circuit member of the circuit board.

  In recent years, insulated gate bipolar transistor (IGBT) devices, intelligent power module (IPM) devices, metal oxide field effect transistor (MOSFET) devices, light emitting diode (LED) devices, freewheeling diode (FWD) devices An electronic device in which various electronic components such as a semiconductor element such as a giant transistor (GTR) element, a sublimation thermal printer head element, and a thermal ink jet printer head element are mounted on a circuit member of a circuit board is used.

  And as a circuit board provided with a circuit member for mounting electronic components, a copper plate is bonded to one main surface of the ceramic substrate as a circuit member, and a copper plate is bonded to the other main surface as a heat radiating member with good heat dissipation. Thus, a brazing material is used for joining the ceramic substrate, the circuit member and the heat radiating member.

  Therefore, the brazing material used when joining the circuit member and the heat radiating member to the ceramic substrate is required to have high bonding strength, and the circuit board in which the circuit member and the heat radiating member are joined using the brazing material has heat radiation characteristics. And high reliability that can withstand long-term use is demanded.

  As such a circuit board, for example, Patent Document 1 discloses a silver-copper brazing material layer containing carbon powder and at least one active metal selected from Ti, Zr, Hf, and Nb. A ceramic circuit board formed by bonding a metal circuit board to a ceramic board has been proposed. The silver-copper brazing material layer further contains at least one element selected from In, Zn, Cd and Sn, thereby lowering the melting point of the brazing material and lowering the bonding temperature of the metal circuit board. It is described that it can be made.

Patent Document 2 discloses a brazing material having good fluidity, high bonding strength, and good corrosion resistance, Zn20-40 wt%, Ag10-15 wt%, P0.005-0.07 wt%, Sn0.1- 1 wt%, Al 0.1-1 wt%, and additional components such as Fe, Pb, Cr, Co, Ni, Ti, Z
There has been proposed a copper-based brazing joint gold containing one or more of r, Hf, Sb, Bi, In, B, Mo, Si, Mg, and Be, with the balance being copper and inevitable impurities.

JP-A-9-283656 JP 63-93496 A

  In recent years, with the progress of high integration, the interval between a plurality of circuit members arranged on a ceramic substrate has been narrowed. Therefore, the brazing material used for joining a plurality of circuit members arranged on the ceramic substrate is unlikely to protrude from the respective joints of the plurality of circuit members, and there is little risk of short-circuiting when the brazing materials that have protruded contact each other. It has been demanded.

  Moreover, since the active metal contained in the brazing material is easily oxidized, there is a problem that the possibility that the bonding strength is reduced due to the oxidation must be reduced.

  The present invention has been devised to solve the above-described problems, and it is an object of the present invention to provide a brazing material capable of reducing unnecessary protrusion at the joint and reducing the joint strength due to oxidation of the active metal. is there. In addition, by using this brazing material, there is less risk of short circuit even when the interval between adjacent circuit members is narrow, and it is possible to cope with high integration, and the bonding strength between the circuit member and the heat dissipation member and the support substrate can be increased. The object is to provide a high circuit board. Furthermore, it aims at providing the electronic device which mounted the electronic component on the circuit member in this circuit board.

Brazing material of the present invention, along with containing 30.5 mass% or more of silver and 35 wt% to 50 wt% of copper as a main component, indium, at least one element A selected from zinc and tin 1 From 0.5 mass% to 9 mass% of a hydrogen compound of at least one element B selected from titanium, zirconium, hafnium and niobium, from molybdenum, osmium, rhenium and tungsten It comprises at least one element C selected from 0.5 mass% to 9 mass% .

  The circuit board of the present invention is a circuit in which a circuit member containing copper is provided on the first main surface side of the insulating support substrate, and a heat radiating member is provided on the second main surface side facing the first main surface. A plurality of circuit members arranged side by side on the first main surface of the support substrate and bonded to the support substrate via a bonding layer made of a brazing material having the above-described configuration. It is a feature.

  The electronic device according to the present invention is characterized in that an electronic component is mounted on the circuit member in the circuit board having the above-described configuration.

  According to the brazing material of the present invention, it contains silver and copper as main components, and at least one element A selected from indium, zinc and tin, and at least one selected from titanium, zirconium, hafnium and niobium. By including the hydrogen compound of element B and at least one element C selected from molybdenum, osmium and tungsten, the flowability of the brazing material is good and the wettability with the member to be joined is good. As a result, voids generated between the members to be joined can be reduced, so that high joining strength can be obtained. In addition, since the element B is made of a hydrogen compound, the element B is less likely to be oxidized than the metal powder of the element B, so that the possibility that the bonding strength is lowered due to the oxidation can be reduced. Further, by including element C that has a high melting point and can prevent the viscosity from becoming too low, unnecessary protrusion at the joint can be reduced, so that the possibility of short circuit due to contact of the protruding brazing material can be reduced.

  Further, according to the circuit board of the present invention, the circuit member containing copper is provided on the first main surface side of the insulating support substrate, and the heat radiation member is provided on the second main surface side facing the first main surface. In the circuit board, a plurality of circuit members are arranged side by side on the first main surface of the support substrate, and are bonded to the support substrate via the bonding layer made of the brazing material of the present invention. Since there are few unnecessary protrusions and the possibility of short circuit between adjacent circuit members can be reduced, a circuit board capable of high integration can be obtained. In addition, since the gap generated between the support substrate, the circuit member, and the heat dissipation member is small and the bonding strength is high, a highly reliable circuit board can be obtained.

In addition, according to the electronic device of the present invention, since the electronic component is mounted on the circuit member of the circuit board of the present invention, the short circuit between the adjacent circuit members hardly occurs. can do.

An example of the circuit board of this embodiment is shown, (a) is a plan view, (b) is a sectional view taken along line A-A 'in (a), and (c) is a bottom view. The other example of the circuit board of this embodiment is shown, (a) is a top view, (b) is sectional drawing in the BB 'line | wire of (a), (c) is a bottom view. . The other example of the circuit board of this embodiment is shown, (a) is a top view, (b) is a sectional view in the CC 'line of (a), (c) is a bottom view. is there. The other example of the circuit board of this embodiment is shown, (a) is a top view, (b) is a sectional view in the DD 'line of (a), (c) is a bottom view. is there.

  Hereinafter, examples of the brazing material of the present embodiment, a circuit board using the same, and an electronic device will be described.

  1A and 1B show an example of a circuit board according to the present embodiment, in which FIG. 1A is a plan view, FIG. 1B is a cross-sectional view taken along line AA ′ in FIG. 1A, and FIG. It is.

  The circuit board 10 of the example shown in FIG. 1 has a circuit member 41 (41a, 41b) containing copper on the first main surface 21a of the insulating support substrate 21 and a heat dissipation member 42 on the second main surface 21b. The circuit board 10 and the circuit member 41 and the heat dissipating member 42 provided on the circuit board 10 are bonded to the support substrate 21 via bonding layers 31a, 31b, 32 made of brazing material.

  In the present embodiment, the brazing material used for joining the support substrate 21 to the circuit member 41 and the heat dissipation member 42 contains silver and copper as main components, and at least one selected from indium, zinc, and tin. Element A, a hydrogen compound of at least one element B selected from titanium, zirconium, hafnium and niobium, and at least one element C selected from molybdenum, osmium, rhenium and tungsten.

In addition, the main component in the brazing material to be the bonding layers 31a, 31b, and 32 is made of silver and copper. Here, the main component is 50% by mass or more in total among 100% by mass of all the components constituting the brazing material. The component which occupies.

  The element A, which is at least one selected from indium, zinc and tin, contained in the brazing material has a low melting point and is easy to melt, so that the flowability of the brazing material is improved. It is possible to reduce gaps (gaps that remain after the brazing material cannot follow) between the bonding layers 31a, 31b, and 32 and the support substrate 21, the circuit member 41, or the heat dissipation member 42. The presence or absence of this void can be confirmed by ultrasonic flaw detection.

Further, the hydrogen compound of element B which is at least one selected from titanium, zirconium, hafnium and niobium contained in the brazing material has good wettability with the support substrate 21, the circuit member 41 and the heat dissipation member 42. Combined with the effect of including the element A that the flowability is good and the voids can be reduced, the bonding strength between the support substrate 21, the circuit member 41, and the heat dissipation member 42 can be increased. And since the hydrogen compound of element B has the characteristic that it is harder to oxidize than the metal powder of element B, it is possible to reduce the possibility that the bonding strength is reduced by oxidation. The bonding strength can be confirmed by measuring the peel strength in accordance with JIS C 6481-1996. The hydrogen compound of element B is, for example, titanium hydride, zirconium hydride, hafnium hydride, or niobium hydride whose composition formulas are shown as TiH ₂ , ZrH ₂ , HfH ₂ , and NbH ₂ , respectively.

In addition, since the element C, which is at least one selected from molybdenum, osmium, rhenium and tungsten, contained in the brazing material has a high melting point and is difficult to melt, it suppresses the viscosity of the brazing material from becoming too low, so that the joint portion Thus, unnecessary protrusion of the bonding layers 31a and 31b can be reduced. In the present embodiment, the fact that the bonding layers 31a and 31b protrude beyond 0.2 mm from the side surfaces of the circuit members 41a and 41b is referred to as unnecessary protrusion. These bonding layers 31a, 31
The protruding length of b can be measured with an optical microscope.

  The brazing material contains silver and copper as main components, and includes the elements A, B and C having the above-described characteristics, so that the brazing material has good flowability, and the support substrate 21 and the circuit member. Since the wettability with 41 and the heat radiating member 42 is good, the gap generated between the support substrate 21 and the circuit member 41 and the heat radiating member 42 can be reduced, so that a high bonding strength can be obtained. Further, since the element B is made of a hydrogen compound, it is less likely to oxidize than the metal powder of the element B, so that the possibility that the bonding strength between the support substrate 21, the circuit member 41, and the heat radiating member 42 is lowered due to oxidation may be reduced. it can. Further, by including element C that has a high melting point and can prevent the viscosity from becoming too low, unnecessary protrusion at the joint can be reduced, so that the possibility of short circuit due to contact of the protruding brazing material can be reduced.

Moreover, as preferable content of the elements A, B, and C that can obtain the above-described characteristics, the content of the element A is 2% by mass or more and 22% by mass or less among 100% by mass of all the components constituting the brazing material. It is preferable that the content of the element B is 1% by mass or more and 8% by mass or less, and the content of the element C is 1% by mass or less and 8% by mass or less. And the remainder becomes silver and copper which are the main ingredients.

  The copper content in the brazing material is preferably 35% by mass or more and 50% by mass or less. When the copper content is in the above range, the flowability of the brazing material can be improved, and the support substrate 21, the circuit member 41, and the heat radiating member at a lower temperature than when silver and copper are used alone, respectively. 42 can be satisfactorily bonded to each other with few voids. In addition, what is necessary is just to obtain | require about the identification and content of each element which comprises a brazing material by a fluorescent X ray analysis method or ICP (Inductively Coupled Plasma) emission spectroscopy analysis method.

  The circuit board 10 of the example shown in FIG. 1 has circuit members 41a and 41b containing copper on the first main surface 21a of the insulating support substrate 21 and a second main surface 21b opposite to the first main surface 21a. In the circuit board 10 provided with the heat dissipating members 42, a plurality of circuit members 41a and 41b are arranged side by side on the first main surface 21a of the support substrate 21. It is characterized in that it is bonded to the support substrate 21 via bonding layers 31a and 31b made of a material.

  The circuit board 10 is adjacent to the circuit board 41a and 41b by bonding to the support substrate 21 via the bonding layers 31a and 31b made of the brazing material of the present embodiment. Since the possibility of a short circuit between the circuit members 41a and 41b can be reduced, the circuit board 10 that can cope with high integration can be obtained. In addition, since the gap generated between the support substrate 21 and the circuit members 41a and 41b is small and the bonding strength is high, the circuit substrate 10 can be made highly reliable.

The average crystal grain size of element C in the bonding layers 31 and 32 is preferably 3 μm or more and 10 μm or less. Since the element C in the bonding layers 31 and 32 has an average crystal grain size of 3 μm or more and 10 μm or less, unnecessary protrusion at the bonding portion can be further reduced, so that the possibility of short circuit between adjacent circuit members 41 can be further reduced. In addition, since the gap generated between the support substrate 21 and the circuit member 41 is sufficiently suppressed, higher bonding strength can be obtained.

The average crystal grain size of the element C in the bonding layers 31 and 32 may be obtained as follows. The temperature of the solution in which 50% by mass of hydrogen peroxide and dilute sulfuric acid were mixed was set to 40 ° C., the bonding layers 31 and 32 were immersed in this solution for 1 minute, etched, and then subjected to an electron needle microanalyzer ( Element C was identified using Electron Probe Micro Analysis, and JIS H 0501-1986 (I
The average crystal grain size of element C may be determined in accordance with the cutting method described in SO 2624-1973). In order that the average crystal grain size of the element C in the bonding layers 31 and 32 is 3 μm or more and 10 μm or less, the average grain size of the element C in the brazing material may be 3 μm or more and 10 μm or less.

In addition, it is preferable that the oxygen content is 2% by mass or less, out of 100% by mass of all components constituting the bonding layers 31 and 32. Since the oxygen content is within the above range, the oxidation of each element constituting the brazing material is suppressed, so that the possibility that the bonding strength between the circuit member 41 and the heat dissipation member 42 and the support substrate 21 is reduced can be reduced. . Note that the oxygen content in the bonding layers 31 and 32 may be obtained by an infrared absorption method. And in order to make oxygen content into 2 mass% or less among 100 mass% of all the components which comprise the joining layers 31 and 32, the element B which comprises the brazing material used as the joining layers 31 and 32 is made from a hydrogen compound. The atmosphere of the brazing material oxidation suppression and the heat treatment at the time of joining may be a vacuum atmosphere.

In addition, it is preferable that the carbon content is 0.05% by mass or less among 100% by mass of all the components constituting the bonding layers 31 and 32. When the carbon content of the bonding layers 31 and 32 is 0.05% by mass or less, the content of carbides that are formed by combining with the element B and carbon and easily start cracks is limited. Cracks are less likely to occur. Note that the carbon content in the bonding layers 31 and 32 may be obtained by an infrared absorption method. And in order to make carbon content 0.05 mass% or less among 100 mass% of all the components which comprise the joining layers 31 and 32, heat processing at the time of joining is performed at 800 degreeC or more and 900 degrees C or less in a vacuum atmosphere. Before heating in the range, heating may be performed in a range of 350 ° C. to 500 ° C. in a nitrogen atmosphere.

  Next, the support substrate 21 constituting the circuit board 10 has such a size that the circuit members 41a and 41b and the heat radiating member 42 can be joined to each other. In order to maintain the thickness, the thickness is preferably 0.13 mm or more and 0.64 mm or less.

  Further, it is preferable that the first main surface 21a and the second main surface 21b of the support substrate 21 have no pinhole-like defects having a diameter of 0.15 mm or more. If there is no pinhole-shaped defect having a diameter of 0.15 mm or more, moisture is hardly adsorbed on the first main surface 21a and the second main surface 21b of the support substrate 21, so that the circuit board 10 is used in a high humidity environment. it can.

  Further, the support substrate 21 is preferably made of ceramics mainly composed of silicon nitride or aluminum nitride. This ceramic may be either a sintered body or a single crystal.

In addition, the main component here means the component which occupies 50 mass% or more among 100 mass% of all the components which comprise ceramics. For the identification of the main component, an X-ray diffraction method is used, and the content of the main component may be determined by a fluorescent X-ray analysis method or an ICP emission spectroscopic analysis method. As for a specific method for determining the content of the main component, when the main component of the support substrate 21 is silicon nitride, the content of silicon is determined by fluorescent X-ray analysis or ICP emission spectroscopic analysis, and converted to nitride. Then, the content of silicon nitride can be obtained. Further, when the main component of the support substrate 21 is aluminum nitride, the aluminum content can be obtained by calculating the aluminum content by the same method as described above and converting it to a nitride.

When the support substrate 21 is made of ceramics mainly composed of silicon nitride, 40 W /
It has a thermal conductivity of (m · K) or more, a three-point bending strength of 500 MPa or more, a dynamic elastic modulus of 300 GPa or more, a Vickers hardness (Hv) of 13 GPa or more, and a fracture toughness (K _1
C ) has an excellent mechanical property of 5 MPam ^1/2 or more, and therefore, when the circuit board 10 is constructed, particularly, the creep resistance and durability against heat cycle are improved and the reliability is excellent. The circuit board 10 can be used over a long period of time.

  Here, regarding the mechanical characteristics, the circuit board 10 is subjected to processing such as etching, and the circuit board 41, the heat radiating member 42, and the support layers 21 and 32 are removed, and the support board 21 is used. First, the three-point bending strength may be measured according to JIS R 1601-2008 (ISO 14704: 2000 (MOD)). When the thickness of the support substrate 21 is thin and the thickness of the test piece cut out from the support substrate 21 cannot be 3 mm, the thickness of the support substrate 21 is evaluated as it is as the thickness of the test piece. It is preferable to satisfy the numerical value.

  The dynamic modulus of elasticity may be measured in accordance with the ultrasonic pulse method specified in JIS R 1602-1995. When the thickness of the support substrate 21 is thin and the thickness of the test piece cut out from the support substrate 21 cannot be 4 mm, the thickness of the support substrate 21 is evaluated as it is as the thickness of the test piece. It is preferable to satisfy the numerical value.

Vickers hardness (Hv) and fracture toughness (K _1C ) conform to the indenter press-in method (IF method) defined in JIS R 1610-2003 (ISO 14705: 2000 (MOD)) and JIS R 1607-1995, respectively. To measure. The thickness of the support substrate 21 is thin, and the thickness of the test piece cut out from the support substrate 21 is JIS R 1610-2003 (ISO 14705).
: 2000 (MOD)), JIS R 1607-1995 0.5m specified by the indenter press-fitting method (IF method)
When m cannot be 3 mm, it is preferable that the thickness of the support substrate 21 is evaluated as it is as the thickness of the test piece, and the result satisfies the above numerical value.

  However, when the thickness of the support substrate 21 is so thin that the above-mentioned numerical value cannot be satisfied by evaluating the thickness as it is, each mechanical characteristic value may be obtained by a calculation formula from the test piece dimensions and the obtained measurement values. .

  In order to obtain the above mechanical characteristics, it is preferable to contain at least 80% by mass of silicon nitride as a main component, and other additive components include erbium oxide, magnesium oxide, silicon oxide, molybdenum oxide and Aluminum oxide or the like may be included.

Further, when the support substrate 21 is made of ceramics whose main component is aluminum nitride, the heat conductivity is 150 W / (m · K) or more, so that the heat dissipation characteristics of the circuit board 10 can be enhanced.

The electrical characteristics of the support substrate 21 are such that the volume resistivity is 10 ¹² Ω · m or more at room temperature and 300 ° C.
Is preferably 10 ¹⁰ Ω · m or more. Since the support substrate 21 has these electrical characteristics, when the electronic component mounted on the circuit member 41 provided on the first main surface 21a of the support substrate 21 operates, the heat dissipation member 42 from the circuit member 41 side. Since current leakage to the side can be suppressed, power loss is not generated, and malfunction of the electronic device can be reduced.

  In the circuit board 10, it is preferable that the element B is chemically bonded to a metal element in the vicinity of the first main surface 21 a of the support substrate 21, and the metal in the vicinity of the element B and the first main surface 21 a of the support substrate 21 is used. Since the chemical bond with the element has a high covalent bond, the bonding strength between the circuit member 41 and the support substrate 21 can be increased.

Here, the vicinity of the first main surface 21 a of the support substrate 21 is 20 μm from the surface of the main surface 21 a of the support substrate 21.
The depth range up to. For example, when the element B is titanium and the support substrate 21 is made of ceramics whose main component is silicon nitride, the chemically bonded compounds are TiSi _x (where x is 1 or more and 3 or less) and Ti. ₅ Si ₃ or the like. The state in which the element B is chemically bonded to the metal element in the vicinity of the first main surface 21a of the support substrate 21 can be identified using an X-ray diffraction method.

The circuit members 41a and 41b constituting the circuit board 10 are the circuit members 41a in the circuit board 10.
The shape of the circuit members 41a and 41b is determined depending on the shape of the electronic components (not shown) mounted on the terminals 41b, and can correspond to the amount of heat generated by the electronic components and the magnitude of the current flowing through the circuit members 41a and 41b. Required. The thickness that can meet this requirement is, for example, 0.2 mm or more and 0.6 mm or less.

  The heat dissipating member 42 constituting the circuit board 10 has a function of releasing heat from the generated electronic components, the thickness of the support board 21 is 0.13 mm or more and 0.64 mm or less, and the circuit members 41a and 41b The thickness of the heat dissipation member 42 is, for example, not less than 0.2 mm and not more than 0.6 mm. Further, the thickness of the bonding layers 31a, 31b, and 32 is, for example, not less than 10 μm and not more than 20 μm.

Further, it is preferable that the circuit member 41 and the heat radiating member 42 constituting the circuit board 10 are mainly composed of copper which is a metal having high thermal conductivity. The main component here is a component that occupies 50% by mass or more, and preferably 80% by mass or more, out of 100% by mass of the total components constituting the circuit member 41 and the heat radiating member 42, respectively.

Copper with the circuit member 41 as its main component has low electrical resistance and high thermal conductivity, so copper with excellent circuit characteristics (characteristics that suppress heat generation of electronic components and reduce power loss) and heat dissipation characteristics It is preferable that the content is at least one selected from oxygen-free copper, tough pitch copper, and phosphorous deoxidized copper. In particular, among oxygen-free copper, it is preferable to use any of linear crystalline oxygen-free copper, single-crystal high-purity oxygen-free copper, and vacuum-dissolved copper having a copper content of 99.995% by mass or more.

  The circuit board 10 provided with the circuit member 41 having a high copper content in this way has a low yield stress and is likely to be plastically deformed at a high temperature. Therefore, the circuit member 41 is less likely to be peeled off from the support substrate 21 and more reliable. It becomes the circuit board 10 with high property. Further, the circuit board 10 provided with the heat dissipating member 42 having a high copper content has higher heat dissipating characteristics. The content of each component constituting the circuit member 41 and the heat radiating member 42 can be determined by fluorescent X-ray analysis or ICP emission spectroscopic analysis.

Further, it is desirable that each volume resistivity of the circuit member 41 and the heat radiating member 42 is 5 × 10 ⁻⁸ Ω · m or less, particularly 3 × 10 ⁻⁸ Ω · m or less.

  2 to 4 show other examples of the circuit board of the present embodiment, (a) is a plan view, (b) is a BB ′ line in each of FIGS. 2 to 4 (a), It is sectional drawing in CC 'line and DD' line, (c) is a bottom view. 2 to 4, members similar to those in FIG. 1 are denoted by the same reference numerals.

The circuit board 10 of the example shown in FIG. 2 has the same size when viewed in plan from a plurality of circuit members 41a and circuit members 41b arranged side by side on the first main surface 21a of the support substrate 21. The structure of the heat dissipation member 42 provided on the surface 21b is the same as that of the circuit board 10 in the example shown in FIG. When the circuit member 41a and the circuit member 41b having the same size are arranged on the first main surface 21a of the support substrate 21 as in the example shown in FIG. 2, the circuit board 10 of the example shown in FIG. Thus, warpage of the support substrate 21 that occurs in the manufacturing process of the circuit board 10 can be suppressed.

  Further, in the circuit board 10 of the example shown in FIG. 3, a plurality of circuit members 41 are arranged in a plurality of rows and a plurality of columns on the first main surface 21a of the support substrate 21, and a heat dissipation member provided on the second main surface 21b. 42 is the same as the circuit board 10 of the example shown in FIG. When the plurality of circuit members 41 having the same size are arranged in a plurality of rows and a plurality of columns on the first main surface 21a of the support substrate 21 as in the example shown in FIG. 3, the circuit substrate 10 of the example shown in FIG. As compared with the above, it is possible to suppress the warp of the support substrate 21 that occurs in the manufacturing process of the circuit board 10.

  Furthermore, in the circuit board 10 of the example shown in FIG. 4, a plurality of circuit members 41 are arranged in a plurality of rows and a plurality of columns on the first main surface 21a of the support substrate 21, and a plurality of heat radiation members are provided on the second main surface 21b. Reference numeral 42 denotes a circuit board 10 arranged in a plurality of rows and columns. When the circuit members 41 and the heat radiating members 42 having the same size are arranged in a plurality of rows and a plurality of columns on the first main surface 21a and the second main surface 21b as in the example shown in FIG. Since the warpage of the support substrate 21 generated in the manufacturing process can be suppressed and the vertical symmetry with the support substrate 21 as a boundary is improved, each circuit can be compared with the circuit substrate 10 shown in FIG. Even if the heat generation of the electronic components mounted on the member 41 varies, heat can be dissipated by the respective heat dissipating members 42, so that the circuit board 10 with high reliability that prevents the heat dissipating members 42 from peeling off can be obtained.

  Next, an example of the manufacturing method of the brazing material of this embodiment will be described.

  The brazing material is composed of silver and copper powders as main components, at least one element A selected from indium, zinc and tin, and at least one selected from titanium, zirconium, hafnium and niobium. A powder comprising a hydrogen compound of element B and a powder comprising at least one element C selected from molybdenum, osmium, rhenium and tungsten are prepared. Then, a predetermined amount is weighed and mixed, and then a resin and an organic solvent are added, and then kneaded and deaerated sequentially to obtain a paste-like brazing material.

  Here, as the resin, for example, acrylic resin, methyl cellulose, ethyl cellulose, nitrocellulose, polylate, polymetalate and the like can be used, and as the organic solvent, for example, alcohol such as terpineol, acetone, toluene, xylene, diethylene glycol monobutyl ether Etc. can be used.

Alternatively, a paste-like brazing material can also be obtained by adding an inorganic compound flux and an organic solvent to the mixed powder constituting the brazing material, and sequentially kneading and degassing. At this time, examples of the inorganic compound used for the inorganic compound flux include acids such as boric acid (H ₃ BO ₃ ) and borohydrofluoric acid (HBF ₄ ), lithium chloride (LiCl), and magnesium chloride (MgCl ₂ ). chloride, sodium fluoride (NaF) fluoride such as, bromides such as potassium bromide (KBr), can be used potassium 4 borate pentahydrate _{(K 2 B 4 O 7 ·} 5H 2 O) , etc. .

In particular, the content of the hydrogen compound of element A, element B and element C in the brazing material is such that the content of element A is 2 mass% or more and 22 mass% or less, and the content of the hydrogen compound of element B is 1 mass. % To 8% by mass, and the content of element C is preferably 1% by mass or less and 8% by mass or less. To make the content within the above range, the brazing material of this embodiment is configured. Of 100% by mass of powder, the content of the powder consisting of element A, the powder consisting of hydrogen compound of element B, and the powder consisting of element C is 2% by mass or more and 22% by mass or less, and 1% by mass or more and 8% by mass or less. And 1% by mass or less and 8% by mass or less.

Moreover, in order to make the copper content in the brazing material 35 mass% or more and 50 mass% or less, the copper powder content in the brazing material 100 mass% is 35 mass% or more and 50 mass% or less. And it is sufficient.

  Further, in order to set the average crystal grain size of the element C in the bonding layers 31 and 32 to 3 μm or more and 10 μm or less, a powder made of the element C having an average grain size of 3 μm or more and 10 μm or less may be used.

  The brazing material obtained by the manufacturing method as described above has good flowability and good wettability between the support substrate 21, the circuit member 41 and the heat radiation member 42 and the brazing material. Since the gap generated between the circuit member 41 and the heat dissipation member 42 can be reduced, a high bonding strength can be obtained. In addition, since the element B is made of a hydrogen compound, it is less likely to be oxidized than the metal powder of the element B, so that the possibility that the bonding strength between the support substrate 21, the circuit member 41, and the heat radiating member 42 is reduced due to the oxidation may be reduced. it can. Further, by including element C that has a high melting point and can prevent the viscosity from becoming too low, unnecessary protrusion at the joint can be reduced, so that the possibility of short circuit due to contact of the protruding brazing material can be reduced.

  Next, an example of the circuit board 10 shown in FIG. 1 will be described as a method for manufacturing the circuit board of the present embodiment.

  First, a support substrate 21 made of ceramics mainly composed of silicon nitride or aluminum nitride having a length of 30 mm to 250 mm, a width of 10 mm to 200 mm, and a thickness of 0.13 mm to 0.64 mm is prepared. By performing heat treatment at 800 ° C. or more and 900 ° C. or less, organic substances and residual carbon adhering to the surface of the support substrate 21 are removed.

  Next, the paste material of the present embodiment is applied to the first main surface 21a and the second main surface 21b of the heat-treated support substrate 21 in accordance with the arrangement of the circuit member 41 and the heat radiating member 42. After applying by any method such as pressure printing method and brush coating method, it is dried at 120 ° C. or higher and 150 ° C. or lower.

  Then, a plurality of circuit members 41a and 41b containing copper are applied to the second main surface 21b and dried on the brazing material of the present embodiment applied to the first main surface 21a of the support substrate 21 and dried. The heat dissipating member 42 is disposed on the brazing material of the present embodiment, and the circuit members 41a and 41b and the heat dissipating member 42 are implemented by heating in a vacuum atmosphere in a range of 800 ° C. or higher and 900 ° C. or lower. Thus, the circuit board 10 bonded to the support substrate 21 through the bonding layers 31a, 31b, 32 made of the brazing material can be obtained. Note that by performing the heat treatment in a vacuum atmosphere, the oxygen content of the bonding layers 31a, 31b, and 32 can be reduced to 2% by mass or less. In order to obtain the circuit board 10 in which the element B is chemically bonded to the metal element in the vicinity of the first main surface 21a of the support substrate 21, the temperature may be set to 840 ° C. or more and 900 ° C. or less.

  Further, in order to obtain the circuit board 10 in which the carbon contents in the bonding layers 31a, 31b, and 32 are each 0.05% by mass or less, heat treatment at the time of bonding is performed in a nitrogen atmosphere in a range of 350 ° C. or more and 500 ° C. or less. After heating, heating may be performed in a vacuum atmosphere in the range of 800 ° C to 900 ° C.

Further, as a circuit member 41, after joining a metal foil containing copper having a size covering a plurality of circuit members 41 to the main surface 21a of the support substrate 21 via the brazing material of this embodiment, for example, one row Resist is printed on the surface of the bonded metal foil in accordance with the matrix, such as 2 columns, 2 rows, 4 columns, 3 rows, 2 columns, 3 rows, 3 columns, etc. Is dried and sprayed with nitric hydrosulfuric acid, hydrofluoric nitric acid, hydrochloric acid or ferric chloride aqueous solution to the joined body to remove the portion where the resist is not printed on the surface of the metal foil. The circuit member 41 constituting the circuit board 10 of the present embodiment may be obtained by removing the resist using an alkaline aqueous solution such as an aqueous potassium hydroxide solution.

  Further, in order to suppress oxidation of the circuit member 41 containing copper, the surface of the circuit member 41 may be covered with nickel or gold through palladium. Further, with respect to the heat radiating member 42, the surface of the heat radiating member 42 may be covered with nickel or gold via palladium.

  Alternatively, after chemically polishing the surfaces of the circuit member 41 and the heat dissipation member 42, 2-aminopyridine, 2-aminoquinoline, 2-aminopyrimidine, 6-aminopyrimidine, 2-aminopyrazine, 2-aminoquinazoline, 4- Oxidation is suppressed by immersion treatment in an aqueous solution containing at least one of aminoquinazoline, 2-aminoquinoxaline, 8-aminopurine, 2-aminobenzimidazole, aminotriazine, aminotriazole and substituted derivatives thereof. Also good.

  The circuit board 10 obtained by the manufacturing method as described above has a circuit member 41 containing copper on the first main surface 21a side of the support substrate 21 and heat radiation on the second main surface 21b side facing the first main surface 21a. Each of the members 42 is provided, and a plurality of circuit members 41 are arranged side by side on the first main surface 21a of the support substrate 21 and are bonded via the bonding layer 31 made of the brazing material of the present embodiment. Since there is little unnecessary protrusion at the joint and there is little risk of short circuit between the adjacent circuit members 41a and 41b, the circuit board 10 that can cope with high integration can be obtained. In addition, since the gap generated between the support substrate 21 and the circuit member 41 is small and the bonding strength is high, the circuit substrate 10 with high reliability can be obtained. Furthermore, if copper having a content of 99.995% by mass or more is used as the circuit member 41 constituting the circuit board 10, when the electronic component is mounted on the circuit member 41, the heat generated from the electronic component is efficient over a long period of time. It can dissipate heat well.

  In addition, an insulated gate bipolar transistor (IGBT) element, an intelligent power module (IPM) element, a metal oxide film type field effect transistor (on the circuit member 41 in the circuit board 10 of the present embodiment having the above-described characteristics) Various electronic components such as semiconductor elements such as MOSFET) elements, light emitting diode (LED) elements, free wheeling diode (FWD) elements, giant transistor (GTR) elements, sublimation thermal printer head elements, thermal ink jet printer head elements, etc. Since the mounted electronic device is less likely to be short-circuited, high reliability can be obtained.

  Examples of the present invention will be specifically described below, but the present invention is not limited to these examples.

  First, a predetermined amount of various powders are weighed and mixed so as to have the contents shown in Tables 1 to 3, and then methylcellulose and terpineol are added, sequentially kneaded and deaerated to obtain a paste-like brazing material. Got. In Tables 1 to 3, when the hydrogen compound of element A and element B and element C are one kind, their element symbols are shown in the respective columns of A1, B1 and C1, respectively. When the hydrogen compound and the element C were two kinds, their element symbols were written in the respective columns of A1 and A2, B1 and B2, C1 and C2, respectively.

Next, a support substrate 21 made of ceramics mainly composed of silicon nitride, having a length of 60 mm, a width of 30 mm, and a thickness of 0.32 mm is prepared, and the support substrate 21 is heat-treated at 840 ° C. Organic substances and residual carbon adhering to the surface of 21 were removed. Thereafter, paste-like brazing material is screen-printed on the first main surface 21a and the second main surface 21b of the heat-treated support substrate 21 at portions corresponding to the arrangement of the circuit members 41a and 41b and the heat radiation member 42 shown in FIG. 135 ℃ after coating
The bonding layers 31a, 31b, and 32 were formed by drying the film.

Then, circuit members 41a and 41b made of oxygen-free copper are formed on the first main surface 21a of the support substrate 21, and a heat dissipation member 42 made of oxygen-free copper is formed on the second main surface 21b opposite to the first main surface 21a. By placing in contact with 31a, 31b, 32 and heating at 840 ° C in a vacuum atmosphere,
A circuit board was obtained in which the circuit members 41a, 41b and the heat dissipation member 42 were bonded to the support substrate 21 via the respective bonding layers 31a, 31b, 32.

Part of the surface of the metal foil so that the circuit members 41a and 41b have the shape and arrangement shown in FIG. 2 after joining the metal foil made of oxygen-free copper to the first main surface 21a of the support substrate 21. The resist is printed on the substrate, dried at 135 ° C., and a ferric chloride aqueous solution or the like is sprayed onto the joined body to remove the portion where the resist is not printed on the surface of the metal foil. The circuit members 41a and 41b can also be obtained by removing the resist using an aqueous solution.

Each of the circuit members 41a and 41b has a square shape with a side of 24 mm and a thickness of 0.3 mm.
The distance between the circuit member 41a and the circuit member 41b was 2 mm. Further, the heat dissipating member 42 had a length of 58 mm, a width of 26 mm, and a thickness of 0.3 mm. Further, the bonding layers 31a and 31
b and 32 were shaped to match the circuit members 41a and 41b and the heat dissipation member 42, and the thickness was 0.02 mm.

Then, the maximum lengths of the bonding layer 31a and the bonding layer 31b protruding from the side surfaces of the circuit member 41a and the circuit member 41b on the line that vertically connects the side surfaces of the circuit members 41a and 41b and the side surface of the support substrate 21, The magnification was measured at 50 times with an optical microscope, and this maximum length was defined as the protruding length. In this embodiment, it is assumed that an unnecessary protrusion occurs when the protrusion length exceeds 0.2 mm.

Further, the bonding layer 31a and the supporting substrate 21 by ultrasonic flaw detection method, the area S _V viewed from above the gap that occurs between the 31b was measured and the state voids no area, or circuit members 41a, 41b of the As the area S _{O of the} main surface, the ratio of the area S _V to the area S _O (= S _V / S _O × 100) is obtained,
This value was taken as the porosity. Here, the measurement conditions of the ultrasonic flaw detection method were a flaw detection frequency of 50 MHz, a gain of 30 dB, and a scan pitch of 100 μm.

  Further, the bonding strength between the circuit member 41a and the support substrate 21 was evaluated by measuring the peel strength of the circuit member 41a in accordance with JIS C 6481-1996. The peel strength was measured after the width of the circuit member 41a was reduced from 24 mm to 10 mm by etching.

  Moreover, about the identification and content of each element which comprises each brazing material, it calculated | required by the fluorescent X ray analysis method. These measured values and calculated values are shown in Tables 1 to 3.

As shown in Tables 1 to 3, Sample No. 2, 3, 5 to 7, 9 to 92 are mainly composed of silver and copper, and at least one element A selected from indium, zinc and tin, and at least selected from titanium, zirconium, hafnium and niobium The circuit members 41a and 41b are supported on the support substrate via bonding layers 31a and 31b made of a brazing material containing one kind of hydrogen compound of element B and at least one kind of element C selected from molybdenum, osmium, rhenium and tungsten. Since the brazing material has good flowability and the wettability between the support substrate 21 and the circuit members 41a and 41b is good, the support substrate 21 and the circuit members 41a and 41b Since there are few voids between the two, high bonding strength can be obtained, and there is no unnecessary protrusion exceeding 0.2 mm, so that a circuit board with a low risk of short-circuiting can be obtained. I understood.

  In addition, the hydrogen compounds of element A and element B and the element C are indium, titanium hydride, and molybdenum, respectively, and the content of the hydrogen compound of element A and element B is the same, but the content of element C is different. When comparing Nos. 9 to 18, Sample Nos. 10 to 17 have an element C content of 1% by mass or more and 8% by mass or less, so that there is no protrusion of the bonding layer 31a and the bonding layer 31b. It was found that there were also few gaps between them.

  Samples No. 2 and No. B, in which the hydrogen compound of element A and element B and the element C are indium, titanium hydride, and molybdenum, respectively, have the same contents of element A and element C, and different contents of the hydrogen compound of element B. When comparing 5-7 and 43-45, sample no. 6, 7, 43, and 44, since the hydrogen compound of element B is 1% by mass or more and 8% by mass or less, the peel strength is 30 kN / m or more, and the bonding strength between the circuit member 41a and the support substrate 21 Was found to be expensive.

  Further, the hydrogen compounds of element A and element B and the element C are indium, titanium and molybdenum, respectively, and the contents of the hydrogen compound of element B and element C are the same, but the contents of element A are different. 2, 3, 7, 12-15, 70-72, sample No. 3, 7, 12 to 15, 70, 71, since the element A is 2% by mass or more and 22% by mass or less, the porosity between the support substrate 21 and the bonding layer 31 is zero, and the bonding strength is It was high and the length of protrusion was short.

In addition, the sample Nos. 1 and 2 in which the types and contents of the hydrogen compounds of element A and element B and element C are the same. When comparing 11 to 15, sample No. Since 12, 13 and 14 had a copper content of 35% by mass or more and 50% by mass or less, it was found that there was no void and sufficient bonding strength was ensured and no protrusion occurred.

First, 51.5% by mass of silver and 40% by mass of copper, the contents of tin as element A, titanium hydride as a hydrogen compound of element B, and molybdenum as element C are 3% by mass and 2.5% by mass, respectively.
After mixing various powders weighed to 3% by mass, methylcellulose and terpineol were added, and the mixture was kneaded and degassed in order to obtain a paste-like brazing material. In addition, the powder of the average particle diameter shown in Table 4 was used for the powder of molybdenum.

  Next, after preparing a support substrate 21 made of ceramics mainly composed of silicon nitride and having a length of 60 mm, a width of 30 mm, and a thickness of 0.32 mm, the circuit members 41a and 41b and the heat dissipation member 42 are attached to the support substrate 21. A circuit board was obtained by the same method as shown in Example 1 except that the bonding temperature was changed from 840 ° C to 900 ° C.

  Then, the protruding length, the void ratio, and the peeling strength were obtained by the same method as that shown in Example 1, and are shown in Table 4, respectively.

The average crystal grain size of molybdenum in the bonding layer 31 is set such that the temperature of the solution in which 50% by mass of hydrogen peroxide and dilute sulfuric acid are mixed is 40 ° C., and the bonding layer 31 is immersed in this solution for 1 minute. After etching, molybdenum was identified using an electron probe microanalyzer (Electron Probe Micro Analysis) and determined in accordance with the cutting method described in JIS H 0501-1986 (ISO 2624-1973).

  As shown in Table 4, the sample No. 1 in which the average crystal grain size of the element C in the bonding layer 31 is 3 μm or more and 10 μm or less. Nos. 94 to 97 were found to have high bonding strength because unnecessary protrusion at the bonding portion was suppressed and the gap generated between the support substrate 21 and the circuit member 41 was sufficiently suppressed. .

First, 51.5% by mass of silver and 40% by mass of copper, the contents of tin as element A, titanium hydride as a hydrogen compound of element B, and molybdenum as element C are 3% by mass and 2.5% by mass, respectively.
After mixing various powders weighed to 3% by mass, methylcellulose and terpineol were added, and the mixture was sequentially kneaded and deaerated in the atmosphere shown in Table 5 to obtain a paste-like brazing material. In addition, when the said atmosphere was a vacuum atmosphere, the ultimate vacuum degree and the content of oxygen contained in the obtained brazing material were measured by an infrared absorption method, and the values are shown in Table 5, respectively.

  Next, after preparing a support substrate 21 made of ceramics mainly composed of silicon nitride and having a length of 60 mm, a width of 30 mm, and a thickness of 0.32 mm, a circuit board is formed by the same method as shown in Example 1. Got.

  The peel strength of the circuit member 41a was measured according to JIS C 6481-1996 as in Example 1, and the values are shown in Table 5.

  As shown in Table 5, Sample No. using a brazing material having an oxygen content of 2% by mass or less. Samples Nos. 100 and 101 are sample Nos. Using brazing filler metals having an oxygen content exceeding 2 mass%. It was found that the peel strength was higher than 99 and a high bonding strength was obtained.

First, 51.5% by mass of silver and 40% by mass of copper, the contents of tin as element A, titanium hydride as a hydrogen compound of element B, and molybdenum as element C are 3% by mass and 2.5% by mass, respectively.
After mixing various powders weighed to 3% by mass, methylcellulose and terpineol were added, and the mixture was kneaded and degassed in order to obtain a paste-like brazing material.

  Next, a support substrate 21 made of ceramics mainly composed of silicon nitride, having a length of 60 mm, a width of 30 mm, and a thickness of 0.32 mm is prepared, and the support substrate 21 is heat-treated at 800 ° C. or more and 900 ° C. or less. Thus, organic substances and residual carbon adhering to the surface of the support substrate 21 were removed. Thereafter, paste-like brazing material is screen-printed on the first main surface 21a and the second main surface 21b of the heat-treated support substrate 21 at portions corresponding to the arrangement of the circuit members 41a and 41b and the heat radiation member 42 shown in FIG. After the application, the bonding layers 31a, 31b, and 32 were formed by drying at 135 ° C.

Then, circuit members 41a and 41b made of oxygen-free copper are formed on the first main surface 21a of the support substrate 21, and a heat dissipation member 42 made of oxygen-free copper is formed on the second main surface 21b opposite to the first main surface 21a. The circuit members 41a, 41b and the heat radiation member 42 are disposed so as to be in contact with 31a, 31b, 32, heated in a nitrogen atmosphere at a temperature shown in Table 6, and then heated in a vacuum atmosphere at 850 ° C. Obtained a circuit board bonded to the support substrate 21 through the respective bonding layers 31a, 31b, 32.

Then, the carbon content contained in the bonding layers 31a, 31b, and 32 was determined by an infrared absorption method. Further, a heat cycle test of the circuit board was performed, and every time 100 cycles after 3000 cycles, the presence or absence of cracks generated in the bonding layers 31a, 31b, and 32 was confirmed using an optical microscope at a magnification of 500 times. One cycle was a cycle in which the temperature was lowered from room temperature to −45 ° C. and held for 15 minutes, the temperature was raised and held at 125 ° C. for 15 minutes, and then the temperature was lowered to room temperature. Crack is bonding layer 31
Table 6 shows the number of cycles confirmed in any one of a, 31b, and 32.

As shown in Table 6, the sample Nos. In which the carbon contents in the bonding layers 31a, 31b, and 32 are each 0.05% by mass or less. 103 and 104 are combined with titanium, which is the element B, and the carbide content that tends to be the starting point of cracks is limited, so that it is found that cracks are less likely to occur in the bonding layers 31a, 31b, and 32. It was.

A support substrate 21 made of ceramics mainly composed of aluminum nitride and silicon nitride is prepared, and a circuit member 41 and a heat radiating member 42 made of oxygen-free copper and SUS304 are joined together by the brazing material of this embodiment similar to that of the first embodiment. A circuit board bonded through layers 31 and 32 was fabricated. Then, a simulation was performed assuming that a heat amount of 40 W / m ² per unit area was given to the main surface of the circuit member 41 of the circuit board having such a material and configuration, and the thermal resistance of the circuit board was estimated. The estimated values are shown in Table 7.

As shown in Table 7, the circuit member 41 and the heat radiating member 42 are made of SUS304. For sample Nos. 106, 108, and 110, the circuit member 41 and the heat radiating member 42 are made of oxygen-free copper. 105, 107, and 109 had smaller thermal resistance values as a result of the simulation than the sample using the support substrate 21 made of the same material. From this result, it was found that copper has a higher thermal conductivity than iron, so that the heat dissipation characteristics can be improved.

First, 51.5% by mass of silver and 40% by mass of copper, the contents of indium as element A, titanium hydride as a hydrogen compound of element B, and molybdenum as element C are 3%, 2.5% and 3%, respectively. After mixing various powders weighed so as to be in mass%, methylcellulose and terpineol were added, and the mixture was kneaded and degassed in order to obtain a paste-like brazing material. Using this brazing material, a circuit board was obtained in the same manner as in Example 1 except that the heat treatment temperature for bonding shown in Table 8 was used.

  Then, by identifying using the X-ray diffraction method, it was confirmed that titanium was chemically bonded to silicon in the vicinity of the first main surface of the support substrate 21, and the presence or absence of titanium silicide was entered in Table 8. Further, as in Example 1, the peel strength of the circuit member 41a was measured in accordance with JIS C 6481-1996, and the value is shown in Table 8.

As shown in Table 8, sample no. Samples Nos. 111 and 112, in which titanium silicide was identified and titanium silicide was not identified. The peel strength was higher than 113. Therefore, by performing heat treatment at a temperature of 840 ° C. or more and 900 ° C. or less during bonding, silicon in the vicinity of the first main surface 21a of the support substrate 21 mainly composed of silicon nitride and titanium which is element B are chemically bonded. It has been found that the bonding strength can be increased because the bond between silicon and silicon has a high covalent bond.

  In addition, when an electronic component was mounted on the circuit member of the circuit board according to the present embodiment which was excellent as described above, a highly reliable electronic device with little risk of short-circuiting could be obtained.

10: Circuit board
21: Support substrate
31, 32: Bonding layer
41: Circuit members
42: Heat dissipation member

Claims (8)

The main component contains 30.5% by mass or more of silver and 35% by mass or more and 50% by mass or less of copper, and at least one element A selected from indium, zinc and tin is 1% by mass to 24% by mass. If, titanium, zirconium, and at least one 9% by mass to 0.5% by mass of hydrogen compounds of the elements B following selected from hafnium and niobium, molybdenum, osmium, of at least one selected from rhenium and tungsten A brazing material comprising element C in an amount of 0.5 mass% to 9 mass% . A circuit board in which a circuit member containing copper is provided on a first main surface side of an insulating support substrate and a heat dissipation member is provided on a second main surface side opposite to the first main surface, wherein the circuit member is A circuit, wherein a plurality of the support substrates are arranged side by side on the first main surface of the support substrate, and are bonded to the support substrate via respective bonding layers made of the brazing material according to claim 1. substrate. The circuit board according to claim 2 , wherein an average crystal grain size of the element C in the bonding layer is 3 μm or more and 10 μm or less. The circuit board according to claim 2 or claim 3, characterized in that of all components 100% by mass constituting the bonding layer, the oxygen content is not more than 2 wt%. Of all components 100% by mass constituting the bonding layer, the circuit board according to any one of claims 2 to 4, wherein the content of carbon is less than 0.05 wt%. The circuit board according to claim 2 , wherein the support substrate is made of ceramics mainly composed of silicon nitride or aluminum nitride. The circuit board according to claim 6 , wherein the element B is chemically bonded to a metal element in the vicinity of the first main surface of the support substrate. Electronic device characterized in that an electronic component is mounted on the circuit member in the circuit board according to any one of claims 2 to 7.

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