JP2016184602A - Circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a circuit board in which the bonding strength or the like between a metal circuit board and a metal terminal is high.SOLUTION: A circuit board includes a ceramic substrate 1 having an upper surface, a metal circuit board 2 having an upper surface and a lower surface, where the lower surface is bonded to the upper surface of the ceramic substrate 1, and a metal terminal 4 joined to the upper surface of the metal circuit board 2 via a brazing material 3. The brazing material 3 contains copper and phosphorus as main components. Since the modulus of elasticity of the brazing material containing copper and phosphorus as main components is relatively small, thermal stress in the joint of the metal circuit board 2 and metal terminal 4 is reduced, and thereby mechanical failure at this joint is suppressed.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a circuit board used for an electronic device such as a power module.

2. Description of the Related Art In recent years, a circuit board in which a semiconductor element such as an IGBT (Insulated Gate Bipolar Transistor) is mounted and an electronic device such as a power module or a switching module in which a large current flows is bonded to a metal board such as copper on both upper and lower surfaces of a ceramic board (See, for example, Patent Document 1 below). The demand for such circuit boards is increasing in applications such as control devices for electric vehicles or power generation devices using thermoelectric conversion.

  Such a circuit board generally has a ceramic substrate and a metal plate provided on the main surface of the ceramic substrate. The metal plate includes, for example, an upper surface metal plate provided on the upper surface of the ceramic substrate. The upper surface metal plate is bonded to the ceramic substrate on the surface facing the ceramic substrate (such as the lower surface). The upper metal plate functions as a conductive path for connecting a base metal layer for mounting electronic components such as semiconductor elements or electronic components to an external electric circuit, for example. In some cases, a metal terminal for electrical connection with an electronic component is joined to the upper metal plate. The joining of the metal terminal to the upper metal plate is performed by a brazing material such as silver brazing.

JP 2002-100848 A

  Compared with conventional circuit boards, there is a possibility that mechanical damage such as cracks may occur at the joint between the metal terminal and the top metal plate due to stress such as thermal stress when the metal terminal is joined to the top metal plate There was a problem that it was big. In particular, since the metal terminal and the metal plate are joined to each other via a brazing material with a relatively small joining area (opposed area), mechanical breakage tends to occur within the brazing material.

  A circuit board according to one aspect of the present invention includes a ceramic substrate having an upper surface, an upper surface and a lower surface, the metal circuit plate having the lower surface bonded to the upper surface of the ceramic substrate, and the metal circuit board. And a metal terminal bonded to the upper surface via a brazing material, wherein the brazing material is a brazing material mainly composed of copper and phosphorus.

  A circuit board according to an aspect of the present invention includes a metal circuit board and a metal terminal joined to the upper surface of the metal circuit board via a brazing material, and the brazing material is composed mainly of copper and phosphorus. Since it is a material, the possibility of mechanical breakage due to stress such as thermal stress is effectively reduced at the joint between the metal terminal and the metal circuit board via the brazing material. This is because the elastic modulus of the brazing material mainly composed of copper and phosphorus is lower than that of the brazing material such as silver brazing in the prior art, and the stress is effectively relieved.

(A) is sectional drawing which shows the principal part of the circuit board in embodiment of this invention. It is sectional drawing which expands and shows an example of the A part of FIG. It is sectional drawing which shows the modification of the principal part of the circuit board shown in FIG. It is sectional drawing which shows the modification of the circuit board shown in FIG.

  A circuit board according to an embodiment of the present invention will be described with reference to the drawings. In addition, the distinction between the upper and lower sides in the following description is for convenience, and does not limit the upper and lower sides when the circuit board is actually used.

  FIG. 1 is a cross-sectional view showing a main part of a circuit board according to an embodiment of the present invention, and FIG. 2 is an enlarged cross-sectional view showing a portion A of FIG.

The circuit board 9 according to the embodiment includes a ceramic substrate 1, a metal circuit board 2 provided on the upper surface of the ceramic substrate 1, and metal terminals 4 joined to the upper surface of the metal circuit board 2 via a brazing material 3. doing. In this example, the metal circuit board 2 is joined to the ceramic substrate 1 by a brazing material 5 for a metal plate. The circuit board 9 is an electronic device such as a semiconductor device in which an electronic component (not shown) such as a semiconductor element is mounted on a part of the metal circuit board 2, for example. The electronic device forms a power module such as an IGBT (Insulated Gate Bipolar Transistor) module, and is used by being mounted on various devices.

The electronic component is mounted on the metal circuit board 2 and joined to the upper surface of the metal circuit board 2 by a connecting material (not shown) such as a low melting point brazing material. Examples of the electronic component include a semiconductor element such as a transistor, an LSI (Large Scale Integrated circuit) for a CPU (Central Processing Unit), an IGBT (Insulated Gate Bipolar Transistor), or a MOS-FET (Metal Oxide Semiconductor-Field Effect Transistor). . The low melting point brazing material is, for example,
It is a solder such as tin-silver or tin-lead.

  The ceramic substrate 1 has a function as a mounting substrate for mounting electronic components, for example. The ceramic substrate 1 has a function as a connection substrate for bonding and holding the metal circuit board 2.

  The metal circuit board 2 includes, for example, a base metal material for connecting electronic components, a heat dissipating material for radiating heat generated by the operation of the electronic components to the outside, and an electronic component and an external electric circuit (not shown). It functions as a conductive path for electrical connection such as between. For example, an electronic component mounted on the metal circuit board 2 is electrically connected to an external electric circuit by the metal circuit board 2. Heat generated by operations including transmission / reception of signals to / from an external electric circuit is dissipated to the outside from the exposed surfaces of the metal circuit board 2 and the ceramic substrate 1.

  In the circuit board 9 of the embodiment, the metal plate 6 is disposed on the lower surface of the ceramic substrate 1. In this example, the metal plate 6 is joined to the ceramic substrate 1 by the same metal plate brazing material 5 as described above. The metal plate 6 is disposed, for example, to assist the above function of the metal circuit board 2. For example, the metal plate 6 functions as a heat radiating portion, and heat radiation from the circuit board 9 to the outside is more effectively performed by the metal plate 6. In this case, the metal circuit plate 2 and the metal plate 6 are more effectively thermally connected by a metal member (not shown) penetrating the ceramic substrate 1 in the thickness direction, and the heat radiation is more effectively performed. You may be made to do. Further, the metal circuit plate 2 and the metal plate 6 may be electrically connected to each other so that signals are transmitted also to the metal plate 6.

The ceramic substrate 1 is formed of a ceramic material such as an aluminum oxide sintered body, a mullite sintered body, a silicon carbide sintered body, an aluminum nitride sintered body, or a silicon nitride sintered body. . Of these ceramic materials, a silicon nitride sintered body, an aluminum nitride sintered body, and a silicon carbide sintered body are preferable in terms of thermal conductivity (heat dissipation). In terms of mechanical strength, a silicon nitride sintered body and a silicon carbide sintered body are preferable.

  In the case where the ceramic substrate 1 is made of a ceramic material having a relatively high mechanical strength such as a silicon nitride sintered body, even if the thickness of the metal circuit board 2 and the metal board 6 is increased, for example, The possibility of cracks occurring on the substrate 1 is reduced. Therefore, it is more advantageous in realizing the circuit board 9 that can flow a larger current even if it is small.

  If the ceramic substrate 1 is made of, for example, silicon nitride ceramics, it is manufactured as follows. That is, first, an appropriate organic binder, plasticizer, solvent, and the like are added to and mixed with raw material powders such as silicon nitride, aluminum oxide, magnesium oxide, and yttrium oxide to prepare a ceramic slurry. Next, the ceramic slurry is formed into a sheet by a forming method such as a doctor blade method or a calender roll method to produce a band-shaped ceramic green sheet (ceramic green sheet). Next, the band-shaped ceramic green sheet is appropriately punched and formed into a predetermined shape, and a plurality of sheets are laminated as necessary to form a formed body. Then, the ceramic substrate 1 can be manufactured by firing this molded body at a temperature of about 1600 to 2000 ° C. in a non-oxidizing atmosphere such as a nitriding atmosphere.

  The metal circuit board 2 is bonded to the upper surface of the ceramic substrate 1 by a metal plate brazing material 5. The metal circuit board 2 bonded to the ceramic substrate 1 functions as a base metal layer for mounting and bonding electronic components as described above, for example. Moreover, the metal circuit board 2 may function as a terminal electrically connected to an electronic component through a conductive connecting material (not shown) such as a bonding wire. Moreover, the metal circuit board 2 may function as an external terminal electrically connected to an external electric circuit through the metal terminal 4, for example.

  In the case where a plurality of functions are required for the metal circuit board 2 as described above, when there are items that need to be electrically insulated from each other, for example, as shown in FIG. A plurality of independent metal circuit boards 2 may be provided on the upper surface of the ceramic substrate 1. The plurality of metal circuit boards 2 can also be joined to the upper surface of the ceramic substrate 1 by the same metal plate brazing material 5 as described above.

  The metal circuit board 2 and the metal board 6 are made of metal such as copper or aluminum, for example. The metal circuit board 2 and the metal board 6 are obtained by subjecting a copper ingot (lumb) to a conventionally known metal processing method such as mechanical processing such as rolling or punching or chemical processing such as etching. For example, it can be manufactured by forming a flat pattern having a thickness of 0.05 to 1 mm into a predetermined pattern. At this time, the metal circuit board 2 and the metal plate 6 may be formed in a predetermined pattern shape in advance, or after a metal plate having the same size and shape as the ceramic substrate 1 is joined to the ceramic substrate 1. You may process into a predetermined pattern shape by an etching.

When the metal circuit board 2 and the metal board 6 are formed in a predetermined pattern in advance and then bonded to the ceramic substrate 1, the following may be performed. First, a plurality of ceramic substrates 1 are prepared. Further, the metal plate is processed into a predetermined pattern shape of the metal circuit board 2 and the metal plate 6 by using press working or etching. Next, a brazing material paste containing an active metal, which becomes the brazing material 5 for the metal plate after joining, is formed into a predetermined shape on at least one of the joint portions where the ceramic substrate 1, the metal circuit board 2 and the metal plate 6 face each other. Apply by screen printing. A brazing material 3 is formed in advance on the lower surface of the metal circuit board 2 and the upper surface of the metal plate 6. The brazing material 5 for the metal plate may be provided at a predetermined position by screen printing, or a metal plate having a predetermined thickness clad with the brazing material 5 for the metal plate may be shaped as the metal circuit board 2 and the metal plate 6. It may also be formed by punching into dimensions. Each member is arranged at a predetermined position, and the temperature is raised to a temperature at which the brazing material 5 for the metal plate melts in a vacuum while applying a load using a jig or the like so that the position does not shift, and the members are joined. By the above, the metal circuit board 2 and the metal plate 6 are joined to the ceramic substrate 1 respectively.

  When the metal circuit board 2 and the metal board 6 are made of copper, it is preferably formed of oxygen-free copper. When formed of oxygen-free copper, when the ceramic substrate 1 and the metal circuit board 2 or the metal board 6 are joined, the surface of the copper is not oxidized by oxygen present in the copper and wetted with the brazing material 3. Since the properties are good, the bonding becomes stronger.

  The brazing material 5 for metal plate is for joining the metal circuit board 2 and the metal plate 6 and the ceramic substrate 1 as described above. The brazing material 5 for the metal plate may be one containing an active metal (active metal brazing material) or a normal one containing no active metal. The brazing material 5 for the metal plate may be an active metal brazing material in all the above-described joining. However, in consideration of productivity and economy as the circuit board 9, it is preferable to use a larger amount of the brazing material 5 for a metal plate that does not contain an active metal.

In order to join the metal circuit board 2 and the metal plate 6 to a predetermined portion of the ceramic substrate 1 with the brazing material 5 for the metal plate, first, the brazing material for the metal plate by screen printing or the like on at least one of the joining surfaces of the respective members. The paste (brazing material paste) is printed and applied in a predetermined pattern with a thickness of 30 to 50 μm, for example. Next, these members are aligned with a brazing filler paste so as to have a predetermined structure. Then, while applying a load of 5 to 10 kPa on the metal plate, heat in a non-oxidizing atmosphere such as a hydrogen gas atmosphere or a hydrogen-nitrogen gas atmosphere at 780 ° C. to 900 ° C. for 10 to 120 minutes. The organic solvent, the solvent, and the dispersing agent are changed to gas to diverge and the brazing material 3 is melted. Thereafter, the metal circuit board 2 and the metal plate 6 can be bonded to a predetermined portion of the ceramic substrate 1 by cooling them and solidifying the metal plate brazing material 5.

  When the metal circuit board 2 and the metal board 6 are made of copper, the above-mentioned brazing material paste containing no active metal is, for example, silver solder made of silver and copper powder, silver-copper alloy powder, or a mixed powder thereof. A material (for example, silver: 72% by mass-copper: 28% by mass) is prepared by adding an appropriate binder, an organic solvent, and a solvent to a powder and kneading. The brazing material paste containing the active metal is prepared by adding 2 to 5% by mass of an active metal such as titanium, hafnium or zirconium or a hydride thereof to the normal brazing material paste, and mixing and kneading. Make it.

  When the metal circuit board 2 and the metal board 6 are made of aluminum, an aluminum brazing material (for example, aluminum: 88% by mass—silicon: 12% by mass) may be used instead of the silver brazing material. In this case as well, a brazing material paste and a brazing material paste containing an active metal may be produced in the same manner and joined in the same manner. When an aluminum brazing material is used, bonding can be performed at about 600 ° C., which is lower than copper.

In order to join the metal circuit board 2 or the metal board 6 to the ceramic substrate 1 with the brazing paste containing no active metal, a metallized layer (not shown) is formed on the ceramic substrate 1, and the metallized layer and the metal circuit are formed. A brazing paste may be disposed between the plate 2 or the metal plate 6. The metallized layer on the ceramic substrate 1 can be formed by forming the ceramic substrate 1 by printing and applying a metallized paste in a predetermined pattern shape on the ceramic green sheet and firing it. it can. Alternatively, after the ceramic substrate 1 is manufactured, the metallized paste may be printed on the ceramic substrate 1 in a predetermined pattern shape and baked. The metallized paste is prepared, for example, by adding and mixing a metal powder composed of tungsten (W), molybdenum (Mo), manganese (Mn) or a mixed powder thereof, an appropriate binder, an organic solvent / solvent, and kneading. To do.

  In addition, after the metal circuit board 2 and the metal board 6 are joined to the ceramic substrate 1, the plating layer 7 having high conductivity such as a nickel plating layer on the surface and having good corrosion resistance and wettability with the brazing material 3 is formed. It may be a deposited one. In this case, for example, an electronic component such as a semiconductor element can be more firmly bonded to the metal circuit board 2 via solder. Further, the electrical connection between the metal circuit board 2 and the external electric circuit can be made better.

In this case, when the thickness of the plating layer 7 such as a nickel plating layer is 1.5 μm or more,
The exposed surfaces of the metal circuit board 2 and the metal board 6 (parts of the surface that are not joined to the ceramic substrate 1) can be covered and protected more effectively, and the oxidative corrosion of the metal circuit board 2 can be more effective. Can be reduced. If the thickness is 10 μm or less, the internal residual stress is relatively small. For example, even if the thickness of the ceramic substrate 1 is less than 300 μm, the internal stress of the plating layer 7 causes the ceramic substrate 1 to The possibility of mechanical failure such as warping or cracking can be further reduced.

  Further, the circuit board 9 of the embodiment has a metal terminal 4 joined to the upper surface of the metal circuit board 2 via a brazing material 3. For example, the metal terminal 4 functions as a terminal when the circuit board 9 is electrically connected to an electronic component or an external electric circuit as described above. If the above-described electrical connection is made via the metal terminal 4, the mutual alignment at the time of connection becomes easier. Further, the connection area can be increased by increasing the mutual connection area.

  In the example of FIGS. 1 and 2, the metal terminal 4 is an elongated rod-shaped (columnar) metal member, for example, copper, iron-nickel-chromium (FeNiCo) alloy, copper-tungsten (CuW), or copper-molybdenum (CuMo). ) Or the like. Copper-tungsten and copper-molybdenum may not be alloys but may be tungsten or molybdenum and copper separated from each other. The metal terminal 4 is of a so-called nail head type having a larger diameter at the end joined to the metal circuit board 2. The metal terminal 4 may have another shape such as a lead terminal type (not shown).

  If the metal terminal 4 is made of, for example, copper, the metal terminal 4 can be produced by subjecting a raw material such as a copper plate to predetermined metal processing such as cutting, rolling and etching, and processing the raw material into a predetermined shape and size.

  The brazing material 3 is a brazing material mainly composed of copper and phosphorus. Since the brazing material 3 joined to the upper surface of the metal circuit board 2 is a brazing material mainly composed of copper and phosphorus, heat is generated at the joint portion between the metal terminal 4 and the metal circuit board 2 through the brazing material 3. The possibility of mechanical failure due to stress such as stress is effectively reduced. This is because the elastic modulus of the brazing material 3 mainly composed of copper and phosphorus is lower than that of the brazing material such as silver brazing in the prior art, and the stress is effectively relieved.

Regarding the elastic modulus of the brazing material 3, the Young's modulus is about 80 to 90 GPa at 25 ° C. On the other hand, for example, a silver solder (JIS standard BAG-8 or the like) containing about 50% by mass or more of silver has a Young's modulus of about 98 GPa at about 25 ° C. As described above, since the elastic modulus (for example, Young's modulus) of the brazing material in the circuit board 9 of the embodiment is low, heat is applied to the joint portion where the joint area between the metal terminal 4 and the metal circuit board 2 is relatively small. Even when stress such as stress occurs, the occurrence of mechanical breakage such as cracks in the joint portion due to the stress is effectively suppressed.

  The brazing material 3 is a phosphorous copper brazing material containing about 70% by mass or more of copper and phosphorus as main components. Examples of the phosphorous copper brazing material include phosphorous (P) -copper (Cu) alloy, phosphorous (P) -copper (Cu) -tin (Sn) alloy, phosphorous (P) -copper (Cu) -tin (Sn). -Nickel (Ni) alloy etc. can be used. If the main component of phosphorus and copper is 80% by mass or more of the entire brazing material, it is easy to keep the elastic modulus of the brazing material 3 relatively small as described above.

  Moreover, as for this main component, copper is about 65 to 95 mass% with respect to the whole brazing material, and phosphorus is about 3 to 8 mass%.

  In this case, if copper is 80% by mass or more, it is more advantageous in terms of the conductivity of the brazing material. Moreover, if phosphorus is 3 mass% or more, it is advantageous at the point of the effect of reducing melting | fusing point. In addition, when phosphorus exceeds 8 mass%, there exists a tendency for the brazing material 3 to become hard.

  The brazing material 3 paste can be prepared, for example, by adding and mixing an appropriate binder, an organic solvent, and a solvent to the phosphorus-copper alloy powder, and kneading the brazing material 3 paste. The brazing material 3 is formed by disposing the metal terminal 4 in the main part by screen printing or the like, disposing the metal terminal 4 in the vicinity of the melting point temperature in a vacuum or the like and melting it.

  In the example shown in FIG. 2, a metal layer 2 a is provided on the surface of the metal circuit board 2. Further, another metal layer 4 a is provided on the surface of the metal terminal 4. These metal layers and the other metal layers 2a and 4a suppress the formation of a fragile metal layer (not shown) in the portion where the metal circuit board 2 and the metal terminal 4 and the brazing material 3 are directly joined. It is provided for things. The metal layer 2 a is provided for improving the wettability of the brazing material 3 with respect to the metal circuit board 2. The metal layer 2a is a plating layer such as copper or an alloy containing copper as a main component. The metal layer 2a is not necessarily required as will be described later.

  That is, for the circuit board 9, for example, as shown in FIG. 3, the brazing material 3 may be directly joined to the upper surface of the metal circuit board 2. In other words, the metal terminal 4 may be joined to the upper surface of the metal circuit board 2 directly by the brazing material 3 without interposing the metal layer 2a therebetween. When the brazing material 3 is directly bonded to the upper surface of the metal circuit board 2, the productivity as the circuit board 9 is increased while ensuring high long-term reliability of the connection of the metal terminals 4 to the metal circuit board 2. More advantageous above. FIG. 3 is a cross-sectional view showing a modification of the main part of the circuit board 9 shown in FIG. In FIG. 3, the same parts as those in FIGS. 1 and 2 are denoted by the same reference numerals. As an example in which no brittle intermetallic compound is generated even if the brazing material 3 is directly joined to the upper surface of the metal circuit board 2, the copper metal terminal 4 is joined to the copper circuit board 2 by the phosphorous copper brazing material 3. Can be mentioned.

  This is due to the following reason. If silver brazing is used as the brazing material 3, there is a possibility that the copper component of the metal circuit board 2 is cured by diffusion of the silver component into the metal circuit board 2. On the other hand, in the circuit board 9 of the embodiment, since the brazing material does not contain a silver component, the possibility of curing such a copper component is greatly reduced. Further, as a means for suppressing diffusion of the silver component to the metal circuit board 2 and the metal terminal 4, a plating layer (for example, the metal layer 2a described above) that prevents the silver from spreading on the exposed surface including the upper surface of the metal circuit board 2 in advance. It is conceivable to join the metal terminal 4 previously coated with a plating layer (for example, the above metal layer 4a) for preventing gold diffusion after coating with (4), but in this case, the step of depositing the plating layer Therefore, it is not advantageous in terms of improvement in productivity as the circuit board 9. On the other hand, the circuit board 9 of this modified example is more advantageous in improving productivity because such a coating plating layer is unnecessary.

  In the circuit board 9 of the embodiment, the brazing material 3 may further contain tin or nickel. In this case, the melting point of the brazing material 3 is lowered by the addition of tin or nickel. Therefore, the temperature at the time of joining the metal terminal 4 to the metal circuit board 2 (at the time of brazing) can be further suppressed. That is, the heating temperature at the time of joining the metal terminal 4 to the metal circuit board 2 is compared with the melting point of the brazing material 5 for the metal plate such as an active brazing material joining the metal circuit board 2 and the ceramic substrate 1. It can be kept lower. Therefore, melting (including partial melting) of the metal plate brazing material 5 due to heat at the time of joining the metal terminals 4 can be more effectively suppressed. In this case, for example, the possibility of misalignment of the metal circuit board 2 due to, for example, the melting of the brazing material 5 for the metal sheet is more effectively reduced, and long-term reliability (for example, reliability for the temperature cycle test). Is further improved.

In addition, the addition amount of tin or nickel with respect to the brazing material 3 is set to a ratio of, for example, 4 to 15% by mass of tin with respect to the entire brazing material 3. Nickel is set to a ratio of 1 to 4.5% by mass. If tin is 4 mass% or more, it has the effect of lowering the melting point of the brazing material and improving wettability. When tin exceeds 15 mass%, the strength of the brazing material is lowered. If nickel is 1% or more, there is an effect of lowering the melting point of the brazing material. When nickel exceeds 4.5%, the melting point of the brazing material increases.

  FIG. 4 is a cross-sectional view showing a modification of the circuit board 9 shown in FIG. 4, parts similar to those in FIGS. 1 and 2 are denoted by the same reference numerals. The example of FIG. 4 is an example of a multilayer circuit board 9A having a plurality of ceramic substrates 1 each having a metal circuit board 2 bonded thereto.

  The multilayer circuit board 9A is formed by bonding a lower ceramic substrate 1B having a metal circuit board 2 on its upper surface to a lower side of an upper ceramic substrate 1A having a metal circuit board 2 on its upper surface. Yes. On the lower surface of the upper ceramic substrate 1A, an auxiliary metal circuit plate 2A joined to face the metal circuit plate 2 on the upper surface of the lower ceramic substrate 1B is provided. Further, a metal plate 6 is provided on the lower surface of the lower ceramic substrate 1B in the same manner as the circuit substrate 9 of the above-described embodiment.

  The joining of the auxiliary metal circuit board 2A and the metal circuit board 2 on the upper surface of the lower ceramic substrate 1B is performed by, for example, the same joining material as the brazing material 5 for the metal plate as described above. The circuit board 9A in the example of FIG. 4 includes a metal circuit board 2 and an auxiliary metal circuit board 2A in the central part (inner layer part) in the thickness direction of the ceramic substrate 1 of the circuit board 9 in the example of FIG. It can also be regarded as an example in which the portion (the metal portion has no reference numeral) is arranged. Such an arrangement of the metal part facilitates improvement in the degree of freedom in designing the conductive path in the circuit board 9 (9A), reduction in conduction resistance, improvement in heat dissipation, and the like.

  As described above, when the multilayer circuit board 9A having the metal circuit board 2 in the inner layer portion is formed, the surface (the upper surface of the ceramic substrate 1A and the lower surface of the ceramic substrate 1B) is to be the metal circuit board 2 positioned in the inner layer portion. Etc.) can be produced in the same manner as the metal circuit board 2 positioned in In this case, for example, if the metal circuit board 2 and the auxiliary metal circuit board 2A formed in a predetermined circuit pattern or the like in advance by etching are attached to the ceramic substrates 1A and 1B, the following is performed. Effects can be obtained. That is, the metal circuit board 2 having a predetermined pattern can be bonded to the upper and lower ceramic substrates 1A and 1B in a state where the warpage is suppressed. Thereby, for example, it becomes easy to ensure the flatness of the entire circuit board 9A. Therefore, peeling of the metal circuit board 2 is more effectively suppressed in a reliability test confirmed by a temperature cycle test or the like. Therefore, this case is more preferable in improving the reliability with respect to the temperature change.

In the multilayer circuit board 9A of the embodiment, if the melting point of the brazing material 3 is in the range of 550 ° C. to 680 ° C., it is further advantageous in the following points. The above active metal brazing material used as the brazing material 5 for the metal plate joining the ceramic substrates 1A, 1B and the metal circuit board 2 has a melting point of about 780 ° C. In consideration of workability, the bonding material such as the brazing material for bonding the upper ceramic substrate 1A and the lower ceramic substrate 1B can be bonded at a temperature at which the brazing material 5 for the metal plate is not remelted. It is preferably about 50 ° C. lower than the melting point of the brazing material 5. Similarly, if the melting point of the brazing material 3 is 680 ° C. or less which is about 50 ° C. lower than the melting point of the brazing material 5 for the metal plate, the metal plate is heated by brazing the metal terminal 4 in the circuit board 9A shown in FIG. The possibility that a part of the brazing filler metal 5 is remelted is more effectively reduced. If the melting point of the brazing material 3 is 550 ° C. or higher, the melting point of the brazing material 3 is sufficiently higher than the heating temperature when the electronic component is joined to the metal circuit board 2 with a low melting point brazing material such as solder. . Therefore, the possibility that the brazing filler metal 3 is most melted during mounting and mounting of the electronic component is effectively reduced. Therefore, in this case, it is possible to provide the circuit board 9A that is more effective for improving the reliability.

1 ... Ceramic substrate 1A, 1B ... Ceramic substrate (modification)
2 .... Metal circuit board 2a ... Metal layer 2A ... Auxiliary metal circuit board 3 ... Braze material 4 ... Metal terminal 4a ... (other) metal Layer 5... Brazing material for metal plate (joining material)
6 ... Metal plate 7 ... Plated layer 9 ... Circuit board

Claims (4)

A ceramic substrate having an upper surface;
A metal circuit board having an upper surface and a lower surface, the lower surface being bonded to the upper surface of the ceramic substrate;
A metal terminal joined to the upper surface of the metal circuit board via a brazing material,
A circuit board, wherein the brazing material is a brazing material mainly composed of copper and phosphorus. The circuit board according to claim 1, wherein the brazing material is directly bonded to the upper surface of the metal circuit board. The circuit board according to claim 1, wherein the brazing material further contains tin or nickel. The circuit board according to claim 3, wherein the melting point of the brazing material is in the range of 550 ° C. to 680 ° C.

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