JP2006019660A - Circuit board for surface mounting of power element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a circuit board which enables a power element, which has a radiation fin and is surface mounted on the board, to radiate heat efficiently. <P>SOLUTION: A first conductor pattern 4, to which the radiation fin 3 of the power element 2 is fixed in close contact by soldering or the like, is formed on a power element mounting surface 1A of the circuit board 1 which is made up of a glass epoxy board or the like. A second conductor pattern 7, which is connected to the first conductor pattern 4 via through-holes 6 in a heat conductive manner, is formed on the back surface 1B of the circuit board 1. The back surface 1B of the circuit board 1 is attached to a device frame 9 in surface contact therewith via a heat-transmissive electrically insulating sheet 8. Heat from the radiation fin 3, therefore, can be released constantly through the first conductor pattern 4 in a stable manner to suppress a temperature increase of the power element 2 efficiently. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a circuit board on which a power element having a radiation fin portion is surface-mounted, and heat dissipation of the surface-mounted power element can be efficiently performed.

  Conventionally, power elements such as power transistors, power MOS FETs, and IGBTs have been used in power control circuits such as power supply circuits, motor drive circuits, and inverter circuits. The power element generates heat due to the power consumption of the element itself, and the voltage handled by the power element is high. As the current increases, the power consumption increases and the heat generation also increases. The failure rate of a power element is known to be significantly affected by temperature, and the failure rate as a power device increases as the temperature of the power device increases.

  For this reason, in the circuit board on which the power element is mounted, various heat radiating means are provided as a method for suppressing the temperature rise of the power element so that heat from the power element can be efficiently and promptly released to the outside. Among them, a method of attaching a power element to a heat radiating plate, a heat radiator or the like has been generally performed.

An electronic device (see Patent Document 1) that can reduce the mounting area of a field-effect transistor (FET) mounted on a substrate and can radiate heat generated by the FET mounted on the substrate is proposed. ing.
As shown in FIG. 7, in the electronic device described in Patent Document 1, a hollow through hole 37 is provided in the wiring substrate 31, and a metal plating layer 32 is provided inside the through hole 37, and the metal in the through hole 37 is provided. The inside of the plating layer 32 is filled with a ferromagnetic material 33. By using a magnetic material having a different magnetic susceptibility as the filling ferromagnetic material 33, the magnitude of the inductance in the high frequency circuit using the FET 35 can be changed.

In addition, an FET 35 is mounted on a hollow through hole 37 having a metal plating layer 32 on the inside, and the source electrode of the FET 35 and the metal plating layer 32 of the through hole 37 are electrically connected via a wiring 34. The metal plating layer 32 of the through hole 37 is connected to the ground 36.
Japanese Patent Laid-Open No. 10-261731

  In an electronic device as disclosed in Patent Document 1, heat generated in the FET 35 can be conducted to the ground 36 through the metal plating layer 32 of the through hole 37 disposed immediately below the FET 35. However, the solder used to closely fix the FET 35 to the wiring 34 on the wiring board 31 connected to the through hole 37 flows into the through hole 37 immediately below the FET 35, and the FET 35 is wired in a flat state. It was difficult to fix to 34.

  In addition, a large number of through holes arranged directly under the FET 35 cannot be formed due to the restriction of the size of the wiring 34. For this reason, heat generated in the FET 35 cannot be conducted in a large amount to the back side of the wiring substrate 31, and the through-hole 37 does not exhibit a sufficient effect for heat conduction.

  Further, no consideration is given to the number and positions of the through holes 37 formed, and the thermal conductivity between the wirings 34 on both the front and back surfaces of the wiring board 31 is not necessarily good.

  An object of the present invention is to provide a circuit board that solves the above-described problems in the prior art and that can efficiently dissipate heat from a power element having a surface-mounted heat dissipating fin portion.

The object of the present invention can be achieved by the inventions described in claims 1 to 2.
That is, in the circuit board of the present invention, as described in claim 1, the circuit board on which a plurality of power elements each having a radiation fin portion are surface-mounted, and the circuit on which the radiation fin portions are separated and surface-mounted. A first conductor pattern formed on the front surface of the substrate, a second conductor pattern formed on the back surface of the circuit board, and a number of through-holes connecting the first conductor pattern and the second conductor pattern so as to allow heat conduction A fixed region in which the first heat dissipating fin portion is placed and fixed tightly, and a heat radiating region extending outward from the power element in the surface direction of the circuit board from the fixed region. And the plurality of through holes are arranged in the heat dissipation region so as to be arranged substantially parallel to the edge of the heat dissipation fin portion, and the back surface of the circuit board has a heat transfer property. Forms a most important characterized by being disposed in surface contact with the device frame or the radiator for accommodating the circuit board via an insulating sheet.

  Further, in the present invention, as described in claim 2, the second conductor pattern is formed on the back side portion of the circuit board corresponding to the portion of the circuit board on which each of the first conductor patterns is formed, The main feature is that at least one pair of adjacent second conductor patterns are integrally formed.

  In the circuit board according to the present invention, the first conductor pattern for surface mounting the power element having the radiation fin portion is arranged on the surface of the circuit board so as to be arranged for each power element surface mounted on the first conductor pattern. Forming. Further, the second conductor pattern and the first conductor pattern formed on the back side of the circuit board are connected so as to be capable of conducting heat through a large number of through holes.

  In addition, an electrically insulating sheet having heat conductivity can be disposed between the back surface of the circuit board and the equipment frame or the radiator that houses the circuit board. Arranged so as to be in surface contact between the back surface of the circuit board and the surface of the equipment frame that houses the circuit board or between the back surface of the circuit board and the surface of the radiator via the electrical insulating sheet. Can do. The first conductor pattern includes a fixed region for mounting and fixing the heat dissipating fin portion, and a heat dissipating region extending outward from the power element in the surface direction of the circuit board from the fixed region. It is formed into a configuration. In addition, a number of through holes that connect the second conductor pattern and the first conductor pattern so as to allow heat conduction are formed in the heat dissipation region, and the formation state of the through holes is substantially parallel to an edge of the heat dissipation fin portion. It forms so that it may become an arrangement | sequence state.

  As a result, the heat released from the heat radiating fin portion is substantially linear from the through holes arranged substantially in parallel from the vicinity of the heat radiating fin portion by a large number of through holes arranged in parallel with the edges of the heat radiating fin portion. And can be thermally conducted to the second conductor pattern. In the second conductor pattern, heat conduction can be performed in a planar shape along the surface of the second conductor pattern from through holes arranged substantially linearly.

  For this reason, with respect to the heat transferred from the radiating fin portion to the first conductor pattern, the temperature distribution in the first conductor pattern is rapidly reduced at the portion where the through hole is formed, and the heat is conducted to the second conductor pattern. And heat can be extracted more efficiently. In addition, by arranging a plurality of through holes arranged substantially in parallel with the edges of the radiating fin portions, the temperature distribution in the first conductor pattern can be reduced stepwise for each row of through holes. Thereby, the temperature in a 1st conductor pattern can always be kept low, and the taking-out of the heat | fever from a radiation fin part to a 1st conductor pattern can be performed still more efficiently.

  In addition, since the electrically insulating sheet having heat conductivity is arranged so as to be in surface contact between the back surface of the circuit board and the equipment frame or radiator that houses the circuit board, it is electrically insulated from the second conductor pattern. Heat can be conducted to the equipment frame or radiator through the sheet, and the heat can be released from the thermally conducted equipment frame or radiator to the outside air. In addition, since the second conductor pattern and the circuit board are electrically insulated from the device frame or the radiator by the insulating sheet, the device frame or the radiator can be used as the ground member.

  Furthermore, since a through hole is not formed in the fixed region on which the radiating fin portion is placed, solder or the like flows into the through hole during surface mounting of the power element, and solder or the like is not formed on the mounting surface of the radiating fin portion. Uniform distribution can be prevented. Therefore, the power element can be surface-mounted on the circuit board in a state where solder and the like are always uniformly distributed, and the power element can be mounted flat on the circuit board.

  In the present invention, as in the second aspect of the present invention, the second conductor pattern is also formed on the back side portion of the circuit board corresponding to the forming portion of the first conductor pattern formed on the surface of the circuit board. In other words, at least one pair of adjacent second conductor patterns can be integrally formed.

  As a result, the second conductor pattern can be formed on both the front and back surfaces of the circuit board in a positional relationship corresponding to the first conductor pattern, so that a desired number of through hole formation positions can be formed for each first conductor pattern. it can. Moreover, since the adjacent second conductor patterns can be integrally formed as the second conductor pattern, the second conductor pattern can be formed as a second conductor pattern having an area sufficient to dissipate heat.

  Preferred embodiments of the present invention will be specifically described below with reference to the accompanying drawings. As the configuration of the circuit board for power element surface mounting of the present invention, in addition to the shape and arrangement described below, if the shape and arrangement can solve the problems of the present invention, those shapes and arrangement The configuration can be adopted. For this reason, this invention is not limited to the Example demonstrated below, A various change is possible.

  FIG. 1 is a pattern diagram of a circuit board on a power element mounting surface according to an embodiment of the present invention. FIG. 2 is a view of the circuit configuration on the back surface of the circuit board as seen through the power element mounting surface. FIG. 3 is a main part schematic diagram showing the arrangement relationship between the power element and the first conductor pattern as viewed from the power element mounting surface. 4 is a cross-sectional view taken along the line IV-IV in FIG. FIG. 5 is a schematic view of the main part of the second conductor pattern as viewed from the back surface of the circuit board. FIG. 6 is a cross-sectional view showing the positional relationship between the device frame and the circuit board.

  As shown in FIG. 1, on a power element mounting surface 1A of a circuit board 1 formed of an insulating substrate such as a glass epoxy substrate, various electrically connected wires, a first conductor pattern 4, and a power element drive A circuit 5 and the like are formed. Further, the power element 2 made of a power MOS FET is fixedly adhered to the first conductor pattern 4 by soldering via the radiation fin portion 3 (see FIGS. 3 to 5 for the power element 2 and the radiation fin portion 3). can do.

  In the illustrated example, a state before the power element 2 is firmly fixed to the first conductor pattern is shown, and a part of the wiring is omitted. Although an example using a power MOS FET as the power element 2 will be described below, the power element that can be used in the present invention is not limited to the power MOS FET, and generates heat due to the power consumption of the element itself. Other power elements can be used as long as they do.

  The first conductor pattern 4 is formed separately for each power element 2 that is placed and fixed in close contact therewith. Each first conductor pattern 4 is formed with a fixed region 13 for tightly fixing the heat dissipating fin portion 3 of the power element 2 and a heat dissipating region 14 thermally conducted from the heat dissipating fin portion 3. 6 is formed. As shown in FIG. 3, the radiating fin portion 3 can be tightly fixed to the fixing region 13 by appropriate fixing means such as solder so that the heat radiating region exists in the front direction and the side direction.

  A large number of through holes 6 are formed in a state of being arranged so as to be substantially parallel to the edge of the radiating fin portion 3. A through hole 6 can be formed so as to surround the radiating fin portion 3. FIG. 3 shows an example in which two rows of through holes 6 are formed in front of the radiating fin portion 3 and one row is formed on both sides of the radiating fin portion 3.

  FIG. 1 shows an example in which five to three rows are formed in front of the radiating fin portion 3 and one row is formed on the side of the radiating fin portion 3. Further, the number of through holes 6 and the number of formations in each row are determined by the size and shape of the first conductor pattern 4 so that the number of through holes in each row is also formed from 2 to 9. An appropriate number can be formed accordingly.

  FIG. 2 shows a state on the back surface 1 </ b> B of the circuit board 1 when seen through from the mounting surface of the power element 2. In FIG. 1, five first conductor patterns 4 are formed in a horizontal row on the upper side of the circuit board 1, and five first conductor patterns 4 are also formed in a horizontal row in the middle part of the circuit board 1. On the back surface 1B of the circuit board 1 corresponding to the first conductor pattern 4 formed on the upper side of the circuit board 1, five second conductor patterns 7 are formed in the same manner as the first conductor pattern 4 on the upper side. is doing.

  On the back surface 1B of the circuit board 1 corresponding to the first conductor pattern 4 formed in the middle part of the circuit board 1, one second conductor pattern 7 is integrally connected. As the second conductor pattern 7, the adjacent second conductor pattern 7 depends on the arrangement configuration on the back surface 1 </ b> B side of the circuit board 1, or on the circuit configuration using the power element 2 that is closely fixed to the first conductor pattern 4. A number of conductor patterns 7 can be appropriately formed integrally.

  In addition, the number of first conductor patterns 4 and the number of second conductor patterns 7 formed on the circuit board 1 are described for illustrative purposes, and the number of first conductor patterns 4 formed on the circuit board 1 and the second number. The number of conductor patterns 7 and the shapes of the first conductor pattern 4 and the second conductor pattern 7 can be formed in any appropriate number and shape.

  As shown in FIG. 4, the first conductor pattern 4 and the second conductor pattern 7 are connected by a through hole 6 so as to be capable of conducting heat. In the first conductor pattern 4, the second conductor pattern 7, and the through hole 6, a metal layer 15 having high thermal conductivity such as copper metal is formed. The metal layer 15 is formed by an appropriate forming method such as plating. The back surface 1B of the circuit board 1 is attached to the device frame 9 in a surface contact state via an electrically insulating sheet 8 having heat conductivity.

  Further, as shown in FIG. 5, the second conductor pattern 7 is formed on the back surface 1B of the circuit board 1 so as to wrap around the formation portion of the first conductor pattern 4 on the circuit board 1, and the heat from the second conductor pattern 7 is It is formed so that discharge can be performed over a wide area.

  3 and 5 show an example in which the first conductor pattern 4 and the second conductor pattern 7 are formed to have substantially the same size. However, the second conductor pattern 7 is the same as the first conductor pattern 4. It does not have to be formed as the same size. As shown in FIG. 2, it is desirable that the size of the second conductor pattern 7 is larger than the size of the first conductor pattern 4 in order to surely release heat from the second body pattern 7.

  As shown in FIG. 6, the circuit board 1 can be mounted in surface contact with the device frame 9 with an electrically insulating sheet 8 having heat conductivity interposed therebetween. As a result, heat conducted from the power element 2 through the radiation fin portion 3 to the first conductor pattern 4 is conducted to the second conductor pattern 7 through the through hole 6 and insulated from the surface of the second conductor pattern 7. By conducting heat to the device frame 9 via the seat 8, heat can be released from the device frame 9 to the outside air.

  As shown in FIG. 6, another circuit board 10 that constitutes the electronic device is configured in layers by columns 11. By using the circuit board 1 according to the present invention, a plurality of circuit boards 10 can also be arranged in layers, and the shape as an electronic device can be configured compactly.

  Instead of conducting heat to the device frame 9, heat can be emitted by conducting heat to a radiator or the like. Even when a radiator or the like is used, it is desirable to interpose an electrically insulating sheet 8 having heat conductivity between the radiator or the like and the back surface 1B of the circuit board 1. When the drain fin portion is shared as the heat radiating fin portion 3, the second conductor pattern 7 and the radiator or the device frame can be electrically connected.

  As a result, the heat generated by the power element 2 taken out from the radiating fin portion 3 can be taken out to the first conductor pattern 4, and the heat transferred to the first conductor pattern 4 is substantially parallel to the edge of the radiating fin portion 3. Heat can be transferred to the second conductor pattern 7 by the row of through-holes 6 formed in the above. In addition, the heat conducted from the through hole 6 to the second conductor pattern 7 can show a heat distribution diffused in a plane within the plane of the second conductor pattern 7. It can be discharged to the equipment frame 9 or the like via the insulating sheet 8.

  For this reason, the heat distribution in the 1st conductor pattern 4 can reduce rapidly the temperature distribution on the 1st conductor pattern 4 with the row | line-shaped through-hole 6 if the radiation fin part 3 is made into a high temperature part. In addition, by forming the through holes 6 over multiple stages, the rate of decrease in temperature distribution can be increased. As a result, heat can always be removed from the radiation fins 3 by the first conductor pattern 4, temperature rise in the power element 2 can be suppressed, and the power element 2 can always be used in a stable state. It becomes like this.

  Further, the heat conducted to the second conductor pattern 7 is diffused in a plane shape of the second conductor pattern 7 and is conducted from the surface to the surface via the insulating sheet 8 so as to release heat from the equipment frame 9 and the like. Can be conducted to the part. Thereby, the temperature rise of the power element 2 can be efficiently suppressed, and the power element can be used in a stable state for a long time.

  In the present invention, the technical idea of the present invention can be applied to a circuit board provided with a heating element in addition to a power element.

It is a pattern figure of the circuit board in a power element mounting surface. (Example) It is the figure which showed the state of the back surface of a circuit board when it sees through from the power element mounting surface. (Example) It is a principal part schematic diagram which shows the arrangement | positioning relationship between the power element seen from the power element mounting surface, and the 1st conductor pattern. (Example) It is IV-IV sectional drawing in FIG. (Example) It is the principal part schematic of the 2nd conductor pattern seen from the back surface of the circuit board. (Example) It is sectional drawing which showed the arrangement | positioning relationship between an apparatus frame and a circuit board. (Example) It is sectional drawing which shows schematic structure of a high frequency power amplifier. (Conventional example)

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Circuit board 1A Power element mounting surface 1B Back surface 2 Power element 3 Radiation fin part 4 1st conductor pattern 5 Power element drive circuit 6 Through hole 7 2nd conductor pattern 8 Insulation sheet 9 Equipment frame 10 Circuit board 11 Support | pillar 13 Fixing area 14 Heat dissipation area 15 Metal layer 31 Wiring substrate 32 Metal plating layer 33 Ferromagnetic material 34 Wiring 35 FET
36 Ground 37 Through hole

Claims (2)

A circuit board for surface mounting a plurality of power elements each having a radiation fin portion;
A first conductor pattern formed on the surface of the circuit board for surface mounting by dividing the radiating fin portion,
A second conductor pattern formed on the back surface of the circuit board;
A plurality of through-holes connecting the first conductor pattern and the second conductor pattern so as to allow heat conduction;
With
The first conductor pattern has a fixed region on which the heat dissipating fin portion is placed and fixed in close contact, and a heat dissipating region extending outward from the power element in the surface direction of the circuit board from the fixed region. ,
The plurality of through holes are formed by being arranged substantially parallel to the edge of the heat radiating fin portion in the heat radiating region,
A power element surface mounting characterized in that the back surface of the circuit board is disposed in surface contact with a device frame or a radiator that houses the circuit board via an electrically insulating sheet having heat conductivity. Circuit board. A second conductor pattern is formed on a portion of the back side of the circuit board corresponding to the portion of the circuit board on which each of the first conductor patterns is formed, and at least one pair of adjacent second conductor patterns is integrated. The circuit board according to claim 1, wherein the circuit board is formed.

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