JP6392583B2 - Circuit board and electronic device - Google Patents

Description

  The present invention relates to a circuit board and an electronic device.

  2. Description of the Related Art Conventionally, as a circuit board used in an electronic device on which an electronic component such as an IGBT (Insulated Gate Bipolar Transistor) such as a power module or a switching module is mounted, for example, a first metal plate provided with a flow path has two insulations. These are sandwiched between substrates, and these insulating substrates are each formed with a metal plate serving as a circuit layer.

JP 2003-86747 A

  However, in the conventional circuit board described above, since the flow path of the first metal plate is provided in the first metal plate in a hollow shape, the bonding area between the upper and lower surfaces of the first metal plate and the insulating substrate is large. It was. Therefore, peeling was likely to occur due to stress caused by the difference in thermal expansion between the first metal plate and the insulating substrate.

  Moreover, in the hollow flow path, the size of the cross-sectional area of the flow path is not sufficient, so that the cooling effect of the first metal plate is insufficient.

  In view of the above problems, an object of the present invention is to provide a circuit board and an electronic device that can improve the cooling effect while suppressing the first metal plate from peeling from the insulating substrate.

A circuit board according to an aspect of the present invention is sandwiched between a first insulating substrate, a second insulating substrate, the first insulating substrate, and the second insulating substrate, and an outer edge of the circuit substrate is the first insulating substrate and the second insulating substrate. A flat metal plate that extends along the outer edge of the second insulating substrate, has a first metal plate having a flow path, a second metal plate provided on the upper surface of the first insulating substrate, and a lower surface of the second insulating substrate. A third metal plate provided, and the flow path is surrounded by a lower surface of the first insulating substrate, an upper surface of the second insulating substrate, and an inner wall of the first metal plate , The second metal plate and the third metal plate overlap with mounting regions of electronic components, and have two openings respectively connected to both ends of the flow path on the outer surface of the first metal plate. And

  An electronic device according to one aspect of the present invention includes the above circuit board and an electronic component mounted on the circuit board.

  According to the circuit board of the present invention, the flow path is surrounded by the lower surface of the first insulating substrate, the upper surface of the second insulating substrate, and the inner wall of the first metal plate. The surface area of the upper and lower surfaces of the metal plate can be reduced. Therefore, the difference in thermal expansion between the first metal plate, the first insulating substrate, and the second insulating substrate can be suppressed. Therefore, the occurrence of peeling can be suppressed.

In addition, since the cross-sectional area of the flow path can be increased as compared with the case where the flow path is hollow, the flow path overlaps with the mounting area of the electronic components of the second metal plate and the third metal plate, so that cooling is performed. The effect is improved.

According to the electronic device of the present invention, since the circuit board described above is included, it is possible to suppress peeling of the first metal plate from the first insulating substrate and the second insulating substrate, and to improve cooling efficiency. it can.

(A) is a top view of the circuit board and electronic device of embodiment of this invention, (b) is sectional drawing in the AA of (a). (A) is a bottom view of the circuit board of FIG. 1, (b) is a side view of the circuit board of FIG. 1, and (c) is a cross-sectional view taken along line BB of (b). is there. (A)-(c) is sectional drawing which shows the other example of the circuit board of embodiment of this invention. (A)-(d) is sectional drawing which shows the example of the manufacturing process of the circuit board of embodiment of this invention. (A) is a top view which shows the other example of the circuit board of embodiment of this invention, (b) is sectional drawing in the AA of (a), (c) is a bottom view. . It is sectional drawing in the BB line of FIG.5 (b). It is a side view which shows the other example of the circuit board and electronic device of embodiment of this invention.

  Hereinafter, a circuit board and an electronic device according to embodiments of the present invention will be described with reference to the drawings. In the drawings, the circuit board and the electronic device are provided in a virtual xyz space and are placed on the xy plane. In the present embodiment, the upper, upper, and upper portions indicate the positive direction of the virtual z axis, and the lower, lower surface, and lower portion indicate the negative direction of the virtual z axis.

  1 and 2, the circuit board includes a first insulating substrate 1a, a second insulating substrate 1b, a first metal plate 3, a second metal plate 4a, and a third metal plate 4b. ing. 1 and 2, the electronic device includes a circuit board and an electronic component 8.

  The first insulating substrate 1a and the second insulating substrate 1b are made of an electrically insulating material, for example, ceramics such as aluminum oxide ceramics, mullite ceramics, silicon carbide ceramics, aluminum nitride ceramics, or silicon nitride ceramics. . Among these ceramic materials, silicon carbide ceramics, aluminum nitride ceramics, or silicon nitride ceramics are preferred in terms of thermal conductivity that affects heat dissipation, and silicon nitride ceramics or silicon carbide ceramics in terms of strength. Is preferred.

  When the first insulating substrate 1a and the second insulating substrate 1b are made of a relatively strong ceramic material such as silicon nitride ceramics, the first to third metal plates, the first insulating substrate 1a, the second insulating substrate 1b, Since the possibility of cracks in the first insulating substrate 1a and the second insulating substrate 1b due to the thermal stress due to the difference in thermal expansion coefficient is reduced, a circuit board capable of flowing a larger current while reducing the size is provided. Can be realized.

The thickness of the first insulating substrate 1a and the second insulating substrate 1b may be smaller in terms of thermal conductivity, for example, about 0.1 mm to 1 mm, and the size of the circuit board or the thermal conductivity or strength of the material used. You may choose according to it.

If the first insulating substrate 1a and the second insulating substrate 1b are made of, for example, silicon nitride ceramics, organic binders, plasticizers suitable for raw material powders such as silicon nitride, aluminum oxide, magnesium oxide, and yttrium oxide, A ceramic green sheet (ceramic raw sheet) is formed by applying a well-known doctor blade method or calender roll method to the slurry by adding and mixing the solvent and then, and then subjecting this ceramic green sheet to suitable punching processing, etc. To form a molded body by laminating a plurality of sheets as necessary, and then firing it in a non-oxidizing atmosphere such as a nitriding atmosphere at a temperature of 1600-2000 ° C. Is done.

  In the example shown in FIGS. 1 and 2, the first metal plate 3 is sandwiched between a first insulating substrate 1 a and a second insulating substrate 1 b and has a flow path 2. The second metal plate 4a is provided on the upper surface of the first insulating substrate 1a, and the third metal plate 4b is provided on the lower surface of the second insulating substrate 1b.

  As in the example shown in FIG. 1B, the flow path 2 is surrounded by the lower surface of the first insulating substrate 1a, the upper surface of the second insulating substrate 1b, and the inner wall of the first metal plate 3. The surface area of the upper and lower surfaces of the first metal plate 3 can be reduced by the amount of the flow path 2. Therefore, the bonding area between the first metal plate 3 and the first insulating substrate 1a and the second insulating substrate 1b can be reduced. Therefore, it is possible to suppress the occurrence of thermal stress between the first metal plate 3 and the first insulating substrate 1a and the second insulating substrate 1b. Therefore, the occurrence of peeling can be suppressed. Moreover, since the cross-sectional area of the flow path 2 can be increased in the thickness direction of the first metal plate 3 as compared with the case where the flow path 2 is hollow, the cooling effect is improved.

  In the example shown in FIGS. 1 and 2, the flow path 2 meanders. In this case, a cooling effect can be exhibited over a wide range, which is preferable.

  In the example shown in FIG. 1A, the flow path 2 overlaps the electronic component 8. In this case, the flow path 2 is located directly below the electronic component 8 with the first insulating substrate 1a interposed therebetween. Therefore, the heat generated in the electronic component 8 can be efficiently radiated.

  Similarly, from the viewpoint of dissipating heat generated by the second metal plate 4a and the third metal plate 4b that are circuit layers, the flow path 2 overlaps with the second metal plate 4a and the third metal plate 4b. Is preferred.

  As in the example shown in FIG. 2B, the entrance / exit of the flow path 2 is an opening 7. In the example shown in FIG. 2B, the opening 7 does not reach the upper and lower first insulating substrates 1a and 2b. The opening 7 is provided in a hollow shape on the side surface of the first metal plate 1. Thereby, it becomes easy to join a base or the like using the periphery of the opening 7 on the side surface of the first metal plate 1 as a joining region. With this base, the inflow of fluid into the flow path 2 or the outflow of fluid from the flow path 2 can be facilitated.

The 1st metal plate 3, the 2nd metal plate 4a, and the 3rd metal plate 4b are flat plate shape, The thickness is 20-600 micrometers, for example. If the 1st metal plate 3, the 2nd metal plate 4a, and the 3rd metal plate 4b are copper plates, since electrical resistance is low and they have high thermal conductivity, they are preferable as a member which comprises a circuit board.

  When the 1st metal plate 3, the 2nd metal plate 4a, and the 3rd metal plate 4b are copper plates, it is preferable that a copper plate is oxygen-free copper, for example. When oxygen-free copper is used as the copper plate, the surface of the copper plate is oxidized by oxygen present in the copper when the copper plate is bonded to the first insulating substrate 1a and the second insulating substrate 1b with the bonding material 5. Is reduced, and the wettability with the bonding material 5 is improved, so that the bonding strength between the first insulating substrate 1a and the second insulating substrate 1b is improved.

  In the example shown in FIGS. 1 and 2, the first metal plate 3, the second metal plate 4 a, and the third metal plate 4 b are disposed on the main surfaces of the first insulating substrate 1 a and the second insulating substrate 1 b through the bonding material 5. Is provided.

For example, the bonding material 5 is Ag-Cu-based. The bonding material 5 contains, for example, at least one active metal material of titanium, hafnium, and zirconium in order to be firmly bonded to the first insulating substrate 1a and the second insulating substrate 1b by being wetted. Yes. Further, the bonding material 5 may have at least one of In and Sn, for example. Note that the thickness of the bonding material 5 may be about 5 to 100 μm, for example.

  When the first metal plate 3, the second metal plate 4a, and the third metal plate 4b are copper plates and the bonding material 5 has a copper component, the bonding material 5, the first metal plate 3, and the second metal plate. 4a and the third metal plate 4b, the diffusion layer is formed by the diffusion of the copper component in each member at the joint between the two members, so that the bonding material 5, the first metal plate 3, the second metal plate 4a The third metal plate 4b is preferably joined firmly to each other.

  In the example shown in FIGS. 1 and 2, an electronic component 8 is mounted on the upper surfaces of the second metal plate 4 a and the third metal plate 4 b in the center via a bonding material 9. The other second metal plate 4a and the third metal plate 4b are connected by a conductive connecting material such as a bonding wire 10 or the like. Thus, in the example shown in FIGS. 1 and 2, the second metal plate 4a and the third metal plate 4b function as circuit conductors. The second metal plate 4a and the third metal plate 4b can also be used as a metal member for mounting the electronic component 8 mounted on the circuit board and a metal member for the ground conductor.

  1 and 2, the first metal plate 3 sandwiched between the first insulating substrate 1a and the second insulating substrate 1b has a flow path 2 and is mainly used as a heat radiating plate. . A fluid (for example, water, air, etc.) flowing in and out of the opening 7 flows in the flow path 2, thereby exhibiting a heat dissipation effect.

The electronic component 8 is, for example, a transistor or an LS for a CPU (Central Processing Unit).
It is a semiconductor element such as I (Large Scale Integrated circuit), IGBT (Insulated Gate Bipolar Transistor), or MOS-FET (Metal Oxide Semiconductor-Field Effect Transistor).

  The bonding material 9 for bonding the electronic component 8 to the second metal plate 4a and the third metal plate 4b is made of, for example, metal or conductive resin. The bonding material 9 made of metal is, for example, solder, gold-tin (Au—Sn) alloy, tin-silver-copper (Sn—Ag—Cu) alloy, or the like. The bonding material 9 made of a conductive resin is, for example, an adhesive having a high thermal conductivity such as an Ag epoxy resin.

  A plating film may be formed on the surfaces of the second metal plate 4a and the third metal plate 4b by a plating method. According to this configuration, since the wettability with the bonding material 9 is improved, the electronic component 8 can be firmly bonded to the surfaces of the second metal plate 4a and the third metal plate 4b. The plating film may be made of a metal having high conductivity and corrosion resistance, and examples thereof include nickel, cobalt, copper, gold, and alloy materials containing these metal materials as main components. The thickness of the plating film may be, for example, 1.5 to 10 μm.

  The plating film preferably contains phosphorus inside. For example, a nickel-phosphorus amorphous alloy plating film is preferable because surface oxidation of the nickel plating film can be suppressed and wettability of a bonding material or the like can be maintained for a long time. Further, when the content of phosphorus with respect to nickel is about 8 to 15% by mass, a nickel-phosphorus amorphous alloy is easily formed, and the adhesive strength of a bonding material or the like to the plating film can be further improved.

  Next, a method for manufacturing a circuit board according to the embodiment of the example shown in FIG. 1 of the present invention will be described.

First, for example, the metal plate base material to be the first metal plate 3 and the second metal plate 4a are respectively disposed on the upper and lower surfaces of the first insulating substrate 1a, and the metal plate base material to be the third metal plate 4b is 2 Arranged on the lower surface of the insulating substrate 1b. In addition, before arrangement | positioning of a metal plate base material, it is predetermined by methods, such as screen printing etc., beforehand in the predetermined position on both the main surfaces of the 1st insulated substrate 1a, and the lower surface of the 2nd insulated substrate 1b. Apply to the shape.

  Next, the metal plate base material to be the first metal plate 3 and the second metal plate 4a is joined to the first insulating substrate 1a by heat treatment, and the metal plate base material to be the third metal plate 4b is connected to the second insulating substrate. Join to 1b. In this step, the laminate is placed in a vacuum furnace and heat treated at about 830 ° C. in a vacuum state.

  Next, a circuit layer and a flow path 2 are formed on each metal plate base material by an etching process. A resist is formed in a region to be left as a metal plate, and for example, an etching process may be performed using ferric chloride as an etchant.

  Next, the first insulating substrate 1a on which the first metal plate 3 and the second metal plate 4a are formed is applied to the second insulating substrate on which the third metal plate 4b is formed by the bonding material 5 in the same manner as described above. Join to 1b. In addition, before arrangement | positioning of a metal plate base material, the bonding | jointing material 5 is beforehand apply | coated to the predetermined shape by methods, such as screen printing, on the upper surface of the 2nd insulated substrate 1b previously.

  As described above, the circuit board of the example shown in FIGS. 1 and 2 can be formed.

  Next, an example of another embodiment of the present invention will be described with reference to FIGS. 3A to 3C are cross-sectional views showing other examples of the circuit board according to the embodiment of the present invention.

  In the example shown in FIG. 3A, the first metal plate 3 includes a third metal layer 3a sandwiched between a first metal layer 3a, a second metal layer 3b, a first metal layer 3a, and a second metal layer 3b. And a metal layer 3c. With this configuration, the degree of freedom in design is increased when the flow path 2 is formed as compared to the example shown in FIG.

  The first metal layer 3a and the second metal layer 3b are, for example, copper layers, and the third metal layer 3c is a brazing material layer mainly composed of silver and copper. The third metal layer 3c has a function of bonding the first metal layer 3a and the second metal layer 3b to each other.

  In the example shown in FIG. 3B, the flow path 2 formed in the first metal layer 3a and the flow path 2 formed in the second metal layer 3b are displaced in the vertical direction. Thereby, the surface area of the whole flow path 2 can be increased, and the cooling effect can be improved.

  In the example shown in FIG. 3C, in the first metal layer 3a and the second metal layer 3b, the width of the flow path 2 becomes narrower as the distance from the insulating substrate increases. As a result, in the first metal plate 3, the width of the flow path 2 is narrow at the center in the thickness direction, and the width of the flow path 2 is widened on the first insulating substrate 1a and the second insulating substrate 1b side. Therefore, the surface area on the insulating substrate side of the flow path 2 is increased, so that the cooling effect is improved. Moreover, since the width of the flow path 2 is narrow at the center, a sufficiently large bonding area between the first metal layer 3a and the second metal layer 3b can be secured, so that the bonding strength is improved.

  Next, a method for manufacturing a circuit board according to the embodiment of the example shown in FIG. 3A of the present invention will be described with reference to FIG.

(1) First, as a first step, as shown in FIG. 4A, the main surfaces of the second metal plate 4a and the metal plate base materials 3a 'and 4a' to be the first metal layer 3a are formed on the first insulating substrate. It arrange | positions on the main surface of 1a. In this step, before the metal plate base material is arranged, the bonding material 5 is applied in a predetermined shape to the two main surfaces of the first insulating substrate 1a in a predetermined position in advance by a method such as screen printing. This bonding material 5 contains, for example, silver and copper as main components, further contains Ti, and has a melting point of 7 by In or Sn.
What was adjusted to about 90 degreeC is used.

  Moreover, although not shown in figure, the metal plate base material used as the 3rd metal plate 4b and the 2nd metal layer 3b also arrange | positions the main surface on the main surface of the 2nd insulated substrate 1b.

  (2) Next, as a second step, the metal plate base materials 3a ′ and 4a ′ are joined to the first insulating substrate 1a by heat treatment. In this step, the laminated body obtained in the first step is placed in a vacuum furnace, and heat treatment is performed at about 830 ° C. in a vacuum state. Thereby, the bonding material 5 is melted and cooled, so that the bonding material 5 is solidified, and the metal plate base materials 3a ′ and 4a ′ are bonded to the first insulating substrate 1a.

  Further, the metal plate base material to be the third metal plate 4b and the second metal layer 3b is also bonded to the second insulating substrate 1b.

  (3) Next, as a third step, as shown in FIGS. 4 (a) and 4 (b), the metal plate non-formation regions in the metal plate base materials 3a ′ and 4a ′ are removed by an etching process. Leave 3a, 4a.

  Specifically, as shown in FIG. 4A, a resist 11 is formed in a copper plate forming region to be left as the metal plates 3a and 4a. For example, ferric chloride may be used as the etching solution. Note that the resist 11 is removed after etching. Through the above steps, as shown in FIG. 4B, the first insulating substrate 1a to which the metal plates 3a and 4a are bonded can be obtained.

  Moreover, the 2nd insulated substrate 1b to which the 3rd metal plate 4b and the 2nd metal layer 3b were joined is obtained by the same process.

  (4) Next, as a fourth step, as shown in FIG. 4C, the first insulating substrate 1a to which the metal plates 3a and 4a are bonded is changed to the second insulating substrate to which the metal plates 3b and 4b are bonded. 1b is disposed via the third metal layer 3c.

  In this step, before the placement, a paste to be the third metal layer 3c is applied in advance to a predetermined position on the second metal layer 3b in a predetermined shape by a method such as screen printing. As the paste used as the third metal layer 3c, a paste having a lower melting point than the bonding material 5 is used.

  (5) Next, as a fifth step, as shown in FIG. 4C, the first insulating substrate 1a to which the metal plates 3a and 4a are bonded is changed to the second insulating substrate to which the metal plates 3b and 4b are bonded. 1b is disposed via the third metal layer 3c.

  As described above, the circuit board of the example shown in FIG. 4D can be formed.

  Next, an example of another embodiment of the present invention will be described with reference to FIG. FIG. 5 is a diagram showing another example of the circuit board according to the embodiment of the present invention.

  In the example shown in FIG. 5, a column 12 is formed in the flow path 2. With this configuration, even when the width of the flow path 2 is increased as in the example shown in FIG. 5, the strength of the circuit board can be maintained because the pillars 12 support the insulating substrates 1a and 1b. it can. Therefore, since the width of the flow path 2 can be increased safely, the cooling effect is further improved.

In addition, the copper plate of this invention is not limited to the example of the said embodiment, A various change is possible if it is in the range of the summary of this invention.

  For example, in FIGS. 1 and 2, the opening 7 is hollow, but the opening 7 may reach the upper and lower first insulating substrates 1a and 2b as in the example shown in FIG. . In this case, the amount of fluid flowing out or inflow from the opening 7 can be increased.

DESCRIPTION OF SYMBOLS 1a ... 1st insulated substrate 1b ... 2nd insulated substrate 2 ... Flow path 3 ... 1st metal plate 3a ... 1st metal layer 3b ... 2nd metal layer 3c ... 3rd metal layer 4a ... 2nd metal plate 4b ... 3rd metal plate 5 ... Bonding material 7 ... Opening 8 ... Electronic component 9 ... Bonding material 10 ... Bonding wire 11 ... Resist 12 ... Pillar

Claims (4)

A first insulating substrate;
A second insulating substrate;
A first metal plate having a flow path, which is sandwiched between the first insulating substrate and the second insulating substrate, and whose outer edge is a flat plate shape along the outer edges of the first insulating substrate and the second insulating substrate. When,
A second metal plate provided on an upper surface of the first insulating substrate;
A third metal plate provided on the lower surface of the second insulating substrate;
Have
The flow path is surrounded by the lower surface of the first insulating substrate, the upper surface of the second insulating substrate, and the inner wall of the first metal plate, and the electronic components of the second metal plate and the third metal plate It overlaps with the mounting area,
A circuit board comprising two openings connected to both ends of the flow path on the outer surface of the first metal plate . The first metal plate is
A first metal layer;
A second metal layer;
A third metal layer sandwiched between the first metal layer and the second metal layer,
The circuit board according to claim 1. The circuit board according to claim 1, wherein a column is formed in the flow path. A circuit board according to any one of claims 1 to 3,
Electronic components mounted on the circuit board;
Including electronic devices.

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