JP5780777B2 - Ceramic circuit board and electronic device using the same - Google Patents

Description

  The present invention relates to a ceramic circuit board in which a circuit made of a metal plate is formed on a ceramic substrate, and an electronic device using the same.

In recent years, semiconductor elements such as IGBTs (Insulated Gate Bipolar Transistors) have been mounted, and as circuit boards used in electronic devices such as power modules and switching modules for flowing large currents, copper and aluminum are used on both sides of a ceramic substrate. A ceramic circuit board in which metal circuit boards made of metal plates are joined is used.

  Such ceramic circuit boards are in increasing demand for applications such as control devices for electric vehicles and power generation devices using thermoelectric conversion, and miniaturization and high density are required. As a method of reducing the size of the circuit of the ceramic circuit board by increasing the density, there is a method of forming the circuit conductor not only on the surface of the ceramic circuit board but also inside.

  As one of the methods, an internal circuit conductor of a so-called ceramic multilayer wiring board is formed by metallization of a thickness of one insulating layer and co-fired with the insulating layer, and a metal circuit board is bonded to the surface of the ceramic multilayer board. (For example, see Patent Document 1).

  As another method, the upper metal circuit board joined to the lower surface of the upper ceramic substrate and the lower metal joined to the upper surface of the lower ceramic substrate and having a shape corresponding to the upper metal circuit board in plan view. There is one in which a metal circuit is formed between upper and lower adjacent ceramic substrates by bonding a circuit board via a bonding material (see, for example, Patent Document 2).

  As another method, ceramic substrates having a plurality of via hole through holes are arranged in the mold so as to be spaced apart from each other, and after pouring the molten metal into the mold, the molten metal is cooled and solidified. In some cases, via holes for connecting the metal plate and the upper and lower metal plates are formed on the ceramic substrate and between the ceramic substrates (see, for example, Patent Document 3).

Japanese Patent Laid-Open No. 2003-31946 JP 2006-319313 A JP 2006-66595 A

  However, in the method of forming the internal circuit conductor on the ceramic multilayer wiring board by the metallization of the insulating layer and the simultaneous firing of the insulating layer, in order to fire the internal circuit conductor together with the insulating layer, Since it is not possible to use a material such as pure copper as a conductor layer, it is difficult to flow a large current with a smaller wiring, and since a thick internal circuit conductor is filled in an insulating layer made of ceramic, There has been a problem that the insulating layer is easily cracked by the thermal stress between the internal circuit conductor and the insulating layer due to the heat generated by the electronic component mounted on the ceramic circuit board, and the insulating property tends to be lowered.

Further, in the method of joining the upper metal circuit board joined to the lower surface of the upper ceramic substrate and the lower metal circuit board joined to the upper surface of the lower ceramic substrate via a joining material, the internal circuit conductor is Since it consists of two metal plates and a bonding material between them, the thickness of the ceramic circuit board is increased, which is not suitable for miniaturization.

  In addition, the method of forming the internal circuit conductor by casting is not easy to manufacture, and the metal plate on the ceramic substrate can be processed into a circuit pattern shape by etching or the like, but the metal formed between the ceramic substrates Since the plate cannot perform such pattern processing, only a so-called solid conductor can be formed, the shape of the internal circuit conductor is not flexible, and the density cannot be increased.

  The present invention has been completed in view of the above problems, and even when the internal circuit conductor having a complicated shape is formed of a metal plate, a large current can flow, and the reliability is high, and the size and thickness are reduced. It is an object of the present invention to provide a ceramic circuit board and an electronic device that can be used.

The ceramic circuit board of the present invention includes a ceramic multilayer substrate in which three or more ceramic substrates are laminated and bonded to each other by a brazing material, and a surface metal circuit board bonded to the upper and lower surfaces of the ceramic multilayer substrate by a brazing material. An inner layer metal circuit board disposed in a circuit through hole having an inner layer circuit pattern shape formed on the ceramic substrate of the inner layer, and formed on the ceramic substrate above and below the ceramic substrate on which the circuit through hole is formed. It is arranged in the through hole, one end is joined to the inner layer metal circuit board and the other end is joined to the other inner layer metal circuit board or the surface layer metal circuit board by a brazing material, and the inner layer metal circuit board and the other inner layer are joined. and a metal post that connects the metal circuit plate or the surface layer metal circuit board, and wherein the inner metal circuit board, the cell of the upper and lower inner layer metal circuit plate It is characterized in that the electrochromic substrate is not directly bonded.

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

  According to the ceramic circuit board of the present invention, a ceramic multilayer substrate in which three or more layers of ceramic substrates are laminated and bonded to each other by a brazing material, and a surface metal circuit board that is bonded to the upper and lower surfaces of the ceramic multilayer substrate by a brazing material An inner layer metal circuit board disposed in an inner layer circuit pattern-shaped circuit through hole formed in the inner layer ceramic substrate, and a through hole formed in the ceramic substrate above and below the ceramic substrate in which the circuit through hole is formed. One end is joined to the inner layer metal circuit board and the other end is joined to the other inner layer metal circuit board or the surface layer metal circuit board by a brazing material, and the inner layer metal circuit board and the other inner layer metal circuit board or the surface layer metal circuit board are joined. Since the inner metal circuit board is made of a metal plate in the same manner as the surface metal circuit board, a large current can flow through the inner metal layer. Since the circuit board is placed in the circuit through hole and is not filled, even if the thermal expansion coefficients of the inner metal circuit board and the ceramic substrate are different, the thermal stress that damages the ceramic substrate to the inner wall surface of the circuit through hole The inner layer metal circuit board is made of a single metal plate, and is formed from a metal plate that has been processed into the inner layer circuit pattern shape in advance. It can be used as a circuit conductor, and is a highly reliable ceramic circuit board that can be reduced in size and thickness.

  According to the electronic device of the present invention, since the electronic component is mounted on the ceramic circuit board of the present invention having the above-described configuration, a large current can flow, a highly reliable, small and thin electronic device and can do.

(A) is a top view which shows an example of embodiment of the electronic device of this invention, (b) is sectional drawing in the AA of (a), (c) is A- of (b). It is sectional drawing in A line. It is an enlarged view of the A section of FIG.1 (b). It is sectional drawing which expands and shows the principal part of the other example of embodiment of the electronic device of this invention. It is sectional drawing which expands and shows the principal part of the further another example of embodiment of the electronic device of this invention. It is sectional drawing which expands and shows the principal part of the further another example of embodiment of the electronic device of this invention. It is sectional drawing which expands and shows the principal part of the further another example of embodiment of the electronic device of this invention. It is sectional drawing which shows the other example of the structure shown by FIG.1 (c). (A)-(d) is sectional drawing which shows an example of the process of manufacturing the ceramic circuit board of this invention, respectively. (A)-(d) is sectional drawing which shows an example of the process of manufacturing the ceramic circuit board of this invention, respectively. (A) And (b) is sectional drawing which shows an example of the process of manufacturing the ceramic circuit board of this invention, respectively. (A) is a top view which shows another example of embodiment of the electronic device of this invention, (b) is sectional drawing in the AA of (a), (c) is a bottom view. .

  The ceramic circuit board and electronic device of the present invention will be described in detail with reference to the accompanying drawings. 1 to 11, 1 is a ceramic substrate, 1 a is a circuit through hole formed in the ceramic substrate 1, 1 b is a through hole formed in the ceramic substrate 1, 2 is a brazing material, 3 is a surface metal circuit board, 4 Is an inner layer metal circuit board, 5 is a metal column, 6 is an electronic component, 7 is a bonding wire, 8 is a heat sink, 9 is a frame, 9a is an insulating frame, and 9b is a metal frame.

  As shown in FIGS. 1 and 11, the ceramic circuit board of the present invention includes a ceramic multilayer board in which three or more layers of ceramic boards 1 are laminated and joined to each other by a brazing material 2, an upper surface of the ceramic multilayer board, and A surface layer metal circuit board 3 joined to the lower surface by a brazing material 2, an inner layer metal circuit board 4 disposed in an inner layer circuit pattern-shaped circuit through hole 1a formed in the inner layer ceramic substrate 1, and a circuit through hole 1a Are disposed in through-holes 1b formed in the ceramic substrate 1 above and below the ceramic substrate 1, and one end is the inner metal circuit board 4 and the other is the other inner metal circuit board 4 or the surface metal circuit board 3. And the metal pillar 5 that is joined by the brazing material 2 to connect the inner metal circuit board 4 and the other inner metal circuit board 4 or the surface metal circuit board 3. Since the inner layer metal circuit board 4 is made of a metal plate similarly to the surface layer metal circuit board 3 because of such a configuration, a large current can flow, and the inner layer metal circuit board 4 is disposed in the circuit through hole 3. Therefore, even if the inner layer metal circuit board 4 and the ceramic substrate 1 have different coefficients of thermal expansion, thermal stress that damages the ceramic substrate 1 to the inner wall surface of the circuit through hole 1a should not be applied. The inner-layer metal circuit board 4 is made of a single metal plate, and is formed of a metal plate that has been processed into an inner-layer circuit pattern shape in advance. Therefore, the inner-layer metal circuit board 4 can be an internal circuit conductor having a complicated circuit pattern shape that can flow a large current. Therefore, the ceramic circuit board is highly reliable and can be reduced in size and thickness.

  Further, the inner layer ceramic substrate 1 can be structured such that mechanical stress such as thermal stress due to the difference in thermal expansion coefficient from the surface layer metal circuit board 3 or the inner layer metal circuit board 4 is not applied. Since a silicon nitride substrate having excellent strength can be used for the ceramic substrate 1 and an aluminum nitride substrate having excellent thermal conductivity can be used for the inner ceramic substrate 1, it depends on the heat dissipation and the mechanical strength of the ceramic substrate 1. Therefore, it is possible to provide a ceramic circuit board having different characteristics such as temperature cycle reliability.

  Since the circuit is routed by the inner layer metal circuit board 4, the surface layer metal circuit board 3 can be reduced in size, and the thermal stress generated between the surface layer metal circuit board 3 and the ceramic substrate 1 can be reduced. The surface metal circuit board 3 can be bonded with high reliability.

  In the example shown in FIG. 1, the ceramic multilayer substrate is formed by laminating three layers of ceramic substrates 1 and joining them together with a brazing material 2, and is connected to the inner layer metal circuit board 4 on the upper surface of the ceramic multilayer substrate. Six surface layer metal circuit boards 3 and one surface layer metal circuit board 3 for mounting the electronic component 6 are joined, and the lower surface metal circuit board on the upper surface via the inner layer metal circuit board 4 and the metal pillar 5 on the lower surface. 6 are respectively connected to the surface metal circuit board 3 and the heat radiating plate 8 for conducting heat generated in the electronic component 6 to the external circuit board and the cooling body. The number of layers of the ceramic multilayer substrate may be more than three, and in order to increase the inner layer circuit conductor by one layer, the ceramic substrate 1 and the metal pillar 5 having the circuit through hole 1a in which the inner layer metal circuit board 4 is disposed. Is added to the two-layer ceramic substrate 1 with the ceramic substrate 1 having a through hole 1b disposed therein.

  The ceramic substrate 1 is made of an insulating ceramic material, for example, ceramics such as aluminum oxide ceramics, mullite ceramics, silicon carbide ceramics, aluminum nitride ceramics, and silicon nitride ceramics. Among these, silicon carbide ceramics, aluminum nitride ceramics, and silicon nitride ceramics are preferable from the viewpoint of thermal conductivity (heat dissipation), and silicon nitride ceramics and silicon carbide ceramics are preferable from the viewpoint of strength. Further, if the ceramic substrate 1 is a ceramic having a high strength such as silicon nitride ceramics, the ceramic substrate 1 is cracked even if the thicker surface metal circuit board 3, inner metal circuit board 4 and heat sink 8 are used. Therefore, it is preferable because the ceramic circuit board can flow a larger current even if it is small. The thinner the thickness, the better in terms of thermal conductivity, but the thickness may be selected according to the size of the ceramic circuit board and the thermal conductivity and strength of the material used, and is about 0.1 mm to 1 mm.

  If the ceramic substrate 1 is made of, for example, silicon nitride ceramics, an appropriate organic binder, plasticizer, and solvent are added to and mixed with raw material powders such as silicon nitride, aluminum oxide, magnesium oxide, yttrium oxide, etc. to make a slurry. The ceramic green sheet (ceramic green sheet) is formed by adopting the doctor blade method and the calender roll method, which are well known in the past, and then the ceramic green sheet is punched appropriately to obtain a predetermined shape. A plurality of sheets are laminated to form a molded body, and then manufactured by firing at a temperature of 1600 to 2000 ° C. in a non-oxidizing atmosphere such as a nitriding atmosphere.

The circuit through hole 1a of the ceramic substrate 1 is a through hole for accommodating the inner layer metal circuit board 4, and is one size larger than the inner layer metal circuit board 4 as in the example shown in FIG. The through-hole 1 b is a through-hole for accommodating the metal pillar 5 that connects the surface metal circuit board 3 and the inner metal circuit board 4 or the surface metal circuit board 3, and is slightly larger than the cross section of the metal pillar 5. is there. Specifically, the distance between the side surface of the inner layer metal circuit board 4 and the inner wall surface of the circuit through hole 1a and the distance between the side surface of the metal pillar 5 and the inner wall surface of the through hole 1b are respectively the inner layer metal circuit. If the length of the plate 4 is 1% of the length and width, and the length of the cross section of the metal column 5 (the diameter if the metal column 5 is a cylinder) is about 1%, the coefficient of thermal expansion is relatively high. Ceramic substrate 1 made of small silicon nitride ceramics (thermal expansion coefficient: about 3 × 10 ⁻⁶ / ° C.) and aluminum having a large thermal expansion coefficient between copper and aluminum (thermal expansion coefficient: about 23 × 10 ⁻⁶ / ° C.) Even when the inner layer metal circuit board 4 and the metal pillar 5 are used, the ceramic due to the heat generation of the electronic components mounted on the ceramic circuit board or the heat generation of the inner layer metal circuit board 4 itself due to a large current. Between the substrate 1, the inner metal circuit board 4 and the metal pillar 5; No stress may be applied to the inner surface of the circuit through-hole 1a and the through hole 1b by differential expansion.

  The thickness of the ceramic substrate 1 is preferably thicker than the thickness of the inner metal circuit board 4 and the height of the metal pillars 5. If the thickness of the ceramic substrate 1 is smaller than any of these thicknesses, the metal pillar 5 causes the surface metal circuit board 3 to pass through the through hole 1b due to the difference in thermal expansion between the ceramic substrate 1, the inner metal circuit board 4 and the metal pillar 5. This is because the pressing force acts and the bonding strength and connection reliability between the surface metal circuit board 3 and the ceramic substrate 1 are likely to decrease. Further, when the thickness of the ceramic substrate 1 is equal to or less than the thickness of the inner layer metal circuit board 4, the ceramic substrate 1 and the inner layer metal circuit board 4 are bonded to the upper and lower sides of the ceramic substrate 1 having the circuit through holes 1a due to a difference in thermal expansion between the ceramic substrate 1 and the inner layer metal circuit board 4. This is because the force by which the inner metal circuit board 4 presses the ceramic substrate 1 acts, and the bonding strength and connection reliability between the ceramic substrate 1 having the circuit through hole 1a and the ceramic substrate 1 above and below the ceramic substrate 1 are likely to be lowered. .

  The circuit through hole 1a and the through hole 1b can be formed by forming holes in the ceramic green sheet by die processing or laser processing in the manufacturing process of the ceramic substrate 1 described above. Alternatively, after the ceramic substrate 1 is manufactured, it is formed by laser processing or sand blast processing.

  The surface metal circuit board 3, the inner metal circuit board 4, the metal pillar 5 and the heat sink 8 are made of metal such as copper or aluminum. For example, mechanical processing such as rolling or punching a copper ingot. By applying a conventionally known metal processing method such as chemical processing such as etching or etching, it is formed in a predetermined pattern, for example, in a flat plate shape having a thickness of 0.05 to 1 mm. At this time, as the surface layer metal circuit board 3 and the inner layer metal circuit board 4, those formed in a predetermined pattern shape in advance may be used. As will be described later, a metal plate having the same size and shape as the ceramic substrate 1. After bonding to the ceramic substrate 1, it may be processed into a predetermined pattern shape by etching.

  When the surface layer metal circuit board 3, the inner layer metal circuit board 4, the metal pillar 5 and the heat sink 8 are made of copper, it is preferably formed of oxygen-free copper. When formed with oxygen-free copper, copper is bonded when the surface layer metal circuit board 3 or the inner layer metal circuit board 4 and the metal pillar 5 are bonded or when the ceramic substrate 1 and the surface layer metal circuit board 3 or the inner layer metal circuit board 4 are bonded. The surface of the metal is not oxidized by oxygen present in the copper, and the wettability with the brazing material 2 is improved, so that the bonding becomes strong.

  Joining between ceramic substrates 1, joining ceramic substrate 1 and surface metal circuit board 3 or inner layer metal circuit or heat sink 8, joining metal pillar 5 and heat sink 8 route board 4, metal pillar 5 and surface metal circuit board 3 or the inner metal circuit board 4 is joined by the brazing material 2. The brazing filler metal 2 may contain an active metal or may be a normal one containing no active metal. The brazing material 2 may use the brazing material 2 containing an active metal for all the above-mentioned joining, but the joining of the metal pillar 5 and the surface metal circuit board 3 or the inner metal circuit board 4 contains an active metal. When the brazing filler metal 2 is used, the brazing filler metal 2 is not bonded to the ceramic substrate 1, so that the brazing filler metal 2 that has flowed out adheres to the inner surface of the circuit through hole 1a, and the inner metal circuit board 4 is fixed to the circuit through hole by thermal stress or the like. It is preferable because no cracks are generated from 1a.

In order to connect each member with the brazing material 2, a brazing material paste is printed and applied in a predetermined pattern with a thickness of, for example, 30 to 50 μm by screen printing or the like on at least one of the joining surfaces of the respective members. After being placed so as to be, 780 ° C. to 900 ° C., 10 to 120 in a vacuum or in a non-oxidizing atmosphere such as a hydrogen gas atmosphere or a hydrogen / nitrogen gas atmosphere while applying a load of 5 to 10 kPa on the metal plate This is performed by heating for a minute, changing the organic solvent or solvent / dispersant of the brazing material paste into a gas to diverge, and melting the brazing material 2.

When the surface layer metal circuit board 3, the inner layer metal circuit board 4, the metal pillar 5 and the heat sink 8 are made of copper, the normal brazing material paste containing no active metal is silver and copper powder, silver-copper alloy powder, Alternatively, it is manufactured by adding and mixing a suitable binder and an organic solvent / solvent to a silver brazing material (for example, silver: 72% by mass-copper: 28% by mass) powder composed of these mixed powders. . The brazing material paste containing the active metal is obtained by adding 2 to 5% by mass of an active metal such as titanium, hafnium, zirconium, or a hydride thereof to the normal brazing material paste, and kneading. Produced.

  When the surface layer metal circuit board 3, the inner layer metal circuit board 4, the metal pillar 5 and the heat radiating plate 8 are made of aluminum, an aluminum brazing material (for example, aluminum: 88 mass%-silicon: 12 mass%) is used instead of the silver brazing material. May be used. 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 the aluminum brazing material 2 is used, bonding can be performed at about 600 ° C., which is lower than copper.

  In order to join the surface layer metal circuit board 3 or the inner layer metal circuit board 4 or the heat sink 8 to the ceramic substrate 1 with an ordinary brazing material paste containing no active metal, a metallized layer is formed on the ceramic substrate 1. The brazing material paste may be disposed between the metallized layer and the surface metal circuit board 3 or the inner metal circuit board 4 or the heat sink 8. The metallized layer on the ceramic substrate 1 is formed by printing and applying a metallized paste in a predetermined pattern shape on a ceramic green sheet when the ceramic substrate 1 is manufactured, or firing the ceramic substrate 1. After fabrication, the metallized paste may be formed on the ceramic substrate 1 by printing, applying and baking it in a predetermined pattern shape. The metallized paste is manufactured 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. .

Further, after the surface layer metal circuit board 3 is bonded to the ceramic substrate 1, a metal having good conductivity, corrosion resistance and good wettability with a brazing material is deposited on the surface thereof by a plating method. In this case, the electronic component 5 such as a semiconductor element can be firmly bonded to the surface metal circuit board 3 via solder, and the electrical connection between the surface metal circuit board 3 and the external electric circuit is good. can do. In this case, if an amorphous alloy of nickel-phosphorus is prepared by containing 8 to 15% by mass of phosphorus inside, the surface of the plating layer made of nickel is well prevented and the wettability with the brazing material is maintained for a long time. This is preferable. When the content of phosphorus with respect to nickel is less than 8% by mass or more than 15% by mass, it becomes difficult to form an amorphous alloy of nickel-phosphorus, and it becomes difficult to firmly bond the solder to the plating layer. Cheap. If the thickness of this nickel plating layer is less than 1.5 μm,
There is a tendency that the surface of the surface metal circuit board 3 cannot be completely covered, and the oxidative corrosion of the surface metal circuit board 3 cannot be effectively prevented. If the thickness exceeds 10 μm, especially when the thickness of the ceramic substrate is less than 300 μm, the internal stress inside the plating layer increases and the ceramic substrate is likely to warp or crack. turn into. Further, if a similar nickel metal layer is formed on the heat radiating plate 8, the bonding to the external circuit board or the cooling body is good.

When the surface layer metal circuit board 3, the inner layer metal circuit board 4 and the heat dissipation plate 8 are formed in a predetermined pattern and bonded in advance using the three-layer ceramic substrate 1, the following may be performed. First, three ceramic substrates 1 having a through hole 1b at a predetermined position and three ceramic substrates 1 having a circuit through hole 1a are prepared. Further, the metal plate is processed into a predetermined pattern shape of the surface metal circuit board 3, the inner metal circuit board 4, the metal pillar 5, and the heat radiating plate 8 using press processing, etching processing or the like. Next, a brazing material paste containing an active metal, which becomes the brazing material 2 after joining, is applied to at least one of the joint portions where the ceramic substrates 1 face each other by screen printing or the like. The brazing material 2 is formed in advance on the upper and lower surfaces of the metal pillar 5. In this brazing material 2, a brazing material paste may be similarly formed on the front and back of the metal column 5 by screen printing, or a metal plate having a predetermined thickness with the brazing material 2 clad on the front and back is punched to the dimensions of the metal column 5. You may form by. By placing each member at a predetermined position and applying a load using a jig or the like so that the position does not shift, the temperature is raised to a temperature at which the brazing filler metal 2 melts in a vacuum, and the respective members are joined to each other. It becomes a substrate.

  A metal plate having the same size and shape as the ceramic substrate 1 is joined to the ceramic substrate 1 on the upper and lower surfaces of the multilayer ceramic substrate on which the internal circuit is formed by the inner layer metal circuit plate 4 and the metal pillars 5. Is processed into a predetermined pattern shape of the surface metal circuit board 3 and the heat sink 8 by etching, for example, as follows. An etching resist ink is applied to the surface of the metal plate bonded on the ceramic substrate 1 by using a technique such as a screen printing method to form a resist film by printing and applying to a predetermined pattern shape. For example, the metal plate is a copper plate. If so, remove portions other than the predetermined pattern of the surface metal circuit board 3 and the heat sink 8 by immersing in an etching solution such as ferric chloride, cupric chloride solution or spraying the etching solution, The resist film may be removed.

  As shown in FIG. 5 or FIG. 6, the inner metal circuit board 4 may be bent or curved. Even if the inner layer metal circuit board 4 and the ceramic substrate 1 have different thermal expansion coefficients, the stress can be relieved by the bent or curved inner layer metal circuit board 4, so that the stress applied to the ceramic substrate 1 is further reduced. Therefore, a more reliable ceramic circuit board can be obtained.

  Further, as shown in FIG. 5, the circuit through hole 1a is connected to the outside air by the vent hole 1c, or as shown in FIG. 6, the vent hole 1c is provided with a filler 1d. Therefore, the circuit through hole 1a may be blocked from outside air, and the inside of the circuit through hole 1a may be filled with gas. The material of the filler 1d is, for example, glass or a metal brazing material. When a brazing material is used for the filler 1d, a metallized layer is preferably formed on the inner surface of the vent hole 1c. If the circuit through hole 1a is connected to the outside air by the vent hole 1c or the circuit through hole 1a is filled with, for example, a gas having a pressure close to atmospheric pressure, no vacuum discharge occurs in the circuit through hole 1a. Even if the brazing material is bonded in a vacuum in order to reduce the voids in the brazing material and improve the thermal conductivity, the dielectric breakdown voltage can be suppressed from being lowered, resulting in a highly reliable ceramic circuit board.

  Further, as shown in FIG. 5 or FIG. 6, a structure in which the brazing material 2 is provided in a portion away from the end portion of the ceramic substrate 1 may be employed. That is, a structure in which the brazing material 2 is provided in a portion away from the circuit through hole 1a may be employed. The possibility of contact between the brazing material 2 and the inner metal circuit board 4 can be reduced, and the reliability can be improved. Further, since the brazing material 2 is separated from the through hole 1b, the possibility of contact between the brazing material 2 and the metal pillar 5 can be reduced.

  Moreover, as shown in FIG. 7, a structure in which a plurality of circuit through holes 1a are connected may be used. For example, even if the shape of the plurality of circuit through holes 1a is complicated, it is possible to provide one common vent hole 1c for the plurality of circuit through holes 1a.

If the ceramic circuit board is a case where the inner metal circuit board 4 is bonded to the ceramic substrate 1 as in the example shown in FIGS. 1 to 3, the inner layer is formed by the steps shown in FIGS. The metal circuit board 4 can also be processed into a predetermined pattern shape by etching. First, as in the example shown in FIG. 8 (a), the upper surface and the lower surface of the upper ceramic substrate 1 having the through holes 1b are formed on the upper surface and the lower surface of the metal to be the surface metal circuit board 3 having the same size as the ceramic substrate 1. The plate 3 ′ and the metal plate 4 ′ to be the inner metal circuit board 4 are joined to each other, and these are connected by the metal pillar 5 in the through hole 1b by the same method as described above. Next, as in the example shown in FIG. 8B, resist films 10 having a predetermined pattern shape of the surface metal circuit board 3 and the inner metal circuit board 4 are formed on the surfaces of the metal plate 3 ′ and the metal plate 4 ′, respectively. To do. Next, as in the example shown in FIGS. 8C and 8D, unnecessary portions of the metal plate 3 ′ and the metal plate 4 ′ that are not covered with the resist film 10 are dissolved by the etching solution, and the resist film 10 Is peeled to produce only the upper side of the ceramic circuit board (upper circuit board). Next, as in the example shown in FIG. 9A, the intermediate layer ceramic substrate 1 having a predetermined circuit through hole 1a and the lower layer ceramic substrate 1 having a predetermined through hole 1b are brazed. A metal plate 3 ′ having the same size as the ceramic substrate 1, which becomes the surface metal circuit board 3 and the heat sink 8 on the lower surface of the ceramic circuit board, is bonded to the lower surface of the ceramic substrate 1 for the lower layer, In the through hole 1b, a metal column 5 bonded to the metal plate 3 ′ is produced. Next, as in the example shown in FIG. 9B, a resist film 10 having a predetermined pattern shape of the surface metal circuit board 3 and the heat sink 8 is formed on the surface of the metal plate 3 ′. Next, as in the example shown in FIGS. 9C and 9D, unnecessary portions of the metal plate 3 ′ that are not covered with the resist film 10 are dissolved with an etching solution, and the resist film 10 is peeled off. Only the lower side of the ceramic circuit board (lower circuit board) is produced. At this time, the ceramic for the intermediate layer is prevented from entering the circuit through hole 1a and the through hole 1b so that the exposed portions of the metal pillar 5 and the metal plate 3 'are exposed in the through hole 1b. The opening of the circuit through hole 1a on the upper surface of the substrate 1 may be closed with a jig or a resist on a film. Then, as in the example shown in FIG. 10A, the upper circuit board and the lower circuit board are overlapped so that the inner layer metal circuit board 4 of the upper circuit board enters the circuit through hole 1a of the lower circuit board. 10B, between the upper layer ceramic substrate 1 and the intermediate layer ceramic substrate 1, and between the inner layer metal circuit board 4 and the lower layer ceramic substrate 1 and the metal pillar 5. The ceramic circuit board 1 of the present invention having a structure in which three layers of ceramic substrates 1 are laminated as in the example shown in FIG. In this method, both the surface layer metal circuit board 3 and the inner layer metal circuit board 4 can be processed into a predetermined pattern shape by etching after joining the large metal plate 3 ′ and metal plate 4 ′ to the ceramic substrate 1. Since the possibility that the metal plate 3 ′ and the metal plate 4 ′ are bent by handling is reduced, it is preferable when a soft copper plate is used or when a thin metal plate is used. Further, since one metal plate 3 ′ or metal plate 4 ′ may be arranged on one ceramic substrate 1, the ceramic substrate 1 before joining, the metal plate 3 ′, and the metal plate 4 ′ are arranged so as to overlap each other. It is easy to do and alignment is easy.

  In the example shown in FIGS. 1 and 2 and the example of FIGS. 8 to 10 showing the manufacturing process, the inner layer metal circuit board 4 has a top surface on the upper ceramic substrate 1 and a lower surface on the lower ceramic substrate 1. 2, but only one side of the upper and lower surfaces of the inner metal circuit board 4 may be bonded to the ceramic substrate 1 as in the example shown in FIG. 3, or ceramic as in the example shown in FIG. 4. It is not necessary to join to the substrate 1.

  When the upper and lower ceramic substrates 1 and the inner metal circuit board 4 are not directly joined as in the example shown in FIG. 4, the ceramic substrate 1 is joined to the ceramic substrate 1 via the metal pillar 5 and the surface metal circuit board 3. The thermal stress generated between the inner layer metal circuit board 4 and the inner layer metal circuit board 4 is easily relaxed by deformation of the inner layer metal circuit board 4 not directly connected to the ceramic substrate 1. As a result, the stress applied to the surface metal circuit board 3 through the metal pillar 5 is also reduced. In addition to the structural reason, the inner layer metal circuit board 4 is connected to the surface metal circuit board 3 through the metal pillars 5 for the reason that there are few portions where the hardness is increased by metal diffusion from the brazing material 2 at the time of joining. This is preferable because the applied stress is small.

  Further, even when only one of the upper and lower surfaces of the inner layer metal circuit board 4 is bonded to the ceramic substrate 1 or when both the upper and lower surfaces of the inner layer metal circuit board 4 are bonded to the ceramic substrate 1, FIG. As in the example shown in FIG. 4, if the upper and lower surfaces of the inner layer metal circuit board 4 are not joined to the ceramic substrate 1, the inner layer metal circuit board 4 is easily deformed, and the hardness is increased by metal diffusion from the brazing material 2. Since the heightened portion is reduced, the stress can be further relaxed.

  When the stress can be relaxed in this way, the ceramic substrate 1 made of a material having high thermal conductivity but low mechanical strength like the aluminum nitride ceramic can be used as the surface ceramic substrate 1. Thus, since it can be formed of an all-layer aluminum nitride ceramic, a ceramic circuit board having both heat dissipation and temperature cycle reliability can be obtained. In this case, a ceramic circuit board having a particularly high heat dissipation property can be obtained.

  In the circuit board of the present invention, the thermal stress applied to the ceramic substrate 1 is mainly generated by the difference in thermal expansion coefficient between the surface layer metal circuit board 3, the inner layer metal circuit board 4, and the heat sink 8 and the ceramic substrate 1, This stress increases in proportion to the hardness of the bonded metal plates and the bonding length between the circuit board and the surface metal circuit board 3 (inner metal circuit board 4). Therefore, as described above, it is preferable that the inner layer metal circuit board 4 is not joined to the ceramic substrate 1 as in the example shown in FIG. 4, and even if it is joined, the example shown in FIG. 2 and FIG. Furthermore, it is preferable that the inner layer metal circuit board 4 is not bonded to the ceramic substrate 1 over the entire upper and lower surfaces of the inner layer metal circuit board 4 because the inner layer metal circuit board 4 is prevented from becoming hard due to diffusion of the brazing material 2. In the example shown in FIG. 11, a relatively large heat sink 8 is joined to the central portion of the lower surface of the ceramic circuit board. However, as in the example shown in FIG. Thus, it is preferable to reduce the thermal stress by shortening the joining length of the heat sink 8 and the ceramic substrate 1. Specifically, the bonding length between the ceramic substrate 1 and the metal plate such as the surface metal circuit board 3 should not exceed 10 mm.

  In the example shown in FIG. 11, a frame 9 is provided on the upper surface of the uppermost ceramic substrate 1 so as to surround the mounting portion of the electronic component 6 and the surface metal circuit board 3. In this example, the frame body 9 is formed on a ceramic substrate 1 by sequentially joining a metal frame body 9 b, an insulating frame body 9 a, and a metal frame body 9 b through a brazing material 2. The upper metal frame 9b is for joining the lid. An electronic device in which the electronic component 6 is hermetically sealed can be obtained by airtightly bonding a lid made of metal or the like on the frame body 9 by brazing, seam welding, YAG laser welding or the like. By doing so, the electronic component 6 can be hermetically sealed, and the surface metal circuit board 3 on the lower surface of the multilayer ceramic substrate can be electrically connected to an external circuit as an external terminal. The lower metal frame 9 b may be formed simultaneously with the surface metal circuit board 3 in the same manner as the surface metal circuit board 3. On the lower metal frame 9b, an insulating frame 9a made of the same ceramic as the ceramic substrate 1 is joined with active metal, and the upper metal frame 9b with active metal on the insulating frame 9a. Are joined. In the example shown in FIG. 11, the frame body 9 is formed by laminating and joining the metal frame body 9b and the insulating frame body 9a in this way, so that the height is higher than the electronic component 6 mounted on the ceramic circuit board. A high frame 9 is formed. The frame body 9 is not limited to the example shown in FIG. 11. For example, the frame body 9 is formed only by the lower metal frame body 9 b and a box-shaped lid that covers the electronic component 6 is joined. May be.

  The electronic component 6 is mounted on the circuit board of the present invention as described above and electrically connected to the electronic device of the present invention. According to the electronic device of the present invention, since the electronic component 6 is mounted on the ceramic circuit board of the present invention having the above-described configurations, a large current can flow, and the reliability is high, and the electronic device is small and thin. It becomes a device. Further, by using the first ceramic substrate and the second ceramic substrate having different characteristics, for example, heat generated from the electronic component can be efficiently discharged to the outside, and the strength of the circuit board can be improved. Therefore, an electronic device having both different characteristics such as heat dissipation and temperature cycle reliability can be obtained.

Electronic components 6 include transistors, LSIs for CPU (Central Processing Unit)
(Large Scale Integrated circuit), IGBT (Insulated Gate Bipolar Transistor)
) And MOS-FET (Metal Oxide Semiconductor-Field Effect Transistor).

  The electronic component 6 is fixed with a metal bonding material such as solder or Au—Si alloy or a conductive resin, mounted on a circuit board, and electrically connected by a bonding wire 7. In the example shown in FIGS. 1 to 10, the surface layer metal circuit board 3 for mounting the electronic component 6 is formed on the upper surface of the first ceramic substrate 1 from the top, but directly on the upper surface of the ceramic substrate 1. Alternatively, it may be mounted on a metallized layer formed on the upper surface of the first ceramic substrate 1.

DESCRIPTION OF SYMBOLS 1 ... Ceramic substrate 1a ... Circuit through hole 1b ... Through hole 2 ... Brazing material 3 ... Surface layer metal circuit board 4 ... Inner layer metal circuit Plate 5 ... Metal pillar 6 ... Electronic component 7 ... Bonding wire 8 ... Heat sink 9 ... Frame body 9a ... Insulation frame body 9b .... Metal frame

Claims (2)

A ceramic multilayer substrate in which three or more layers of ceramic substrates are laminated and bonded to each other by a brazing material, a surface metal circuit board bonded to the upper and lower surfaces of the ceramic multilayer substrate by a brazing material, and an inner layer formed on the ceramic substrate The inner layer metal circuit board disposed in the circuit through hole having the inner layer circuit pattern shape and the through hole formed in the ceramic substrate above and below the ceramic substrate in which the circuit through hole is formed, Are joined to the inner layer metal circuit board and the other end is joined to the other inner layer metal circuit board or the surface layer metal circuit board by a brazing material, respectively, and the inner layer metal circuit board and the other inner layer metal circuit board or the surface layer metal circuit. and a metal post that connects the plate, and the inner metal circuit board, and the top and bottom of the ceramic substrate of the inner layer metal circuit plate are directly bonded Ceramic circuit board, characterized in that brewing.   An electronic device in which an electronic component is mounted on the ceramic circuit board according to claim 1.

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