JP2010109309A - Electronic substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electronic substrate configured to efficiently dissipate heat produced in a coil formed by a circuit pattern of a substrate. <P>SOLUTION: A DC-DC converter 100 includes heat dissipating members 161 to 163 formed so as to dissipate heat to a cooling section 103 from the side of one end. The heat dissipating members 161 to 163 are arranged so that one end thereof comes into contact with the cooling section 103 with a thermally conductive insulation sheet 102 sandwiched therebetween. The other end of each of the heat dissipating members 161 to 163 is connected to each of wiring circuits 152 to 154, respectively. Due to this, it becomes possible to dissipate heat that propagates on the wiring circuits 152 to 154 to the cooling section 103 via the heat dissipating members 161 to 163. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to the technical field of electronic substrates that generate a large amount of heat.

  The DC-DC converter for automobiles is generally of a system composed of four parts: a switching MOS-FET, a voltage converting transformer, a rectifying diode, and a smoothing choke coil. A DC-DC converter for a hybrid vehicle is configured such that each component is individually cooled by a cooling component such as a water jacket because heat from each component increases due to high voltage and large current. That is, each is separately mounted on a cooling component, and each component is electrically connected by a bus bar or the like (for example, cited document 1).

In the configuration as described above, not only the screw fastening work or welding work in the connection part is increased, but the number of assembling steps is increased, and in order to avoid an electrical problem caused by the contact resistance variation in the connection part, Also, it is necessary to add dedicated parts.
As a countermeasure against such a problem, these components are formed by forming a coil constituting a voltage converting transformer and a smoothing choke coil with a circuit pattern of a substrate on which a switching MOS-FET and a rectifying diode are mounted. Can be integrated, thereby reducing the number of connection points.
JP 2005-143215 A

  However, when a switching MOS-FET, a rectifying diode, a voltage conversion transformer, and a smoothing choke coil are formed and integrated on the same substrate, they are routed through a wiring circuit that electrically connects the components. As a result, heat is easily conducted. FIG. 12 shows an example of an electronic board formed by integrating the above components on the same board. FIG. 12 is a cross-sectional view of a conventional electronic substrate 900 constituting a DC-DC converter.

  When the coils constituting the voltage conversion transformer 920 and the smoothing choke coil 940 are formed in a circuit pattern, the heat generation therein is larger than that of the switching MOS-FET 910 and the rectifying diode 930. As a result, heat generated by the transformer 920 and the choke coil 940 is transmitted to the MOS-FET 910 and the diode 930 via the wiring circuits 952 to 954, and these are heated to a high temperature. The MOS-FET 910 and the diode 930 have a problem that reliability cannot be ensured when the temperature becomes higher than a predetermined temperature.

  In addition, in order to form a coil constituting the voltage conversion transformer 920 and the smoothing choke coil 940 with a circuit pattern and to reduce the substrate area used therefor, it is necessary to use a multilayer substrate having at least four conductor layers. There is. When a four-layer multilayer substrate is used, it is preferable to reduce the thickness per conductor layer in order to suppress the total thickness and total weight of the substrate.

  However, if the thickness per layer is made too thin, the amount of heat generated from the coils constituting the voltage conversion transformer and the smoothing choke coil becomes large and the substrate temperature rises. If the substrate temperature rises too much, it will be difficult to ensure the reliability of through-holes and interlayer insulating materials formed in the substrate. Furthermore, when the heat generated in the coil increases, the MOS-FET and the diode are further increased in temperature through the wiring circuit, making it difficult to ensure their reliability.

  In the electronic board with large current and high heat dissipation as described above, the conductor thickness is set to about 0.5 mm, which is the same as that of the insulating material, in order to conduct a large current. The conductor layer should also be made thinner. At the same time, it is preferable to increase the conductor width for facilitating heat dissipation. However, particularly in the choke coil, there is a problem that the conductor width of the coil portion cannot be increased due to the dimensional limitation of the ferrite core. As a result, since heat generation at the coil portion is increased, it is necessary to use an insulating resin material having high heat resistance for the substrate. As described above, it has been difficult to achieve both low cost (thinning) of the conductor and low cost of the insulating resin material (use of a low heat resistant material).

  Therefore, the present invention has been made to solve these problems, and provides an electronic substrate configured to efficiently dissipate heat generated by a coil formed by a circuit pattern of the substrate. Objective.

  A first aspect of the electronic substrate of the present invention is an electronic substrate having one or more conductor layers in which a coil is formed with a circuit pattern, the wiring circuit electrically connected to the coil, the coil, and the coil And a heat dissipating member formed so as to be able to dissipate heat from any one or more of the wiring circuits.

  In another aspect of the electronic substrate of the present invention, the heat dissipating member is formed so that one end can dissipate heat to a predetermined cooling portion, and the other end is connected to the wiring circuit.

  According to another aspect of the electronic substrate of the present invention, a circuit element is mounted and connected to the wiring circuit, one end is formed to be able to radiate heat to the predetermined cooling unit, and the other end can be radiated from the circuit element. It is provided with another heat radiating member formed so that it may become.

  In another aspect of the electronic substrate of the present invention, another wiring circuit formed so as to be able to dissipate heat is further connected to one end side of the heat radiating member or the other heat radiating member. It is characterized by being.

  Another aspect of the electronic substrate of the present invention is characterized in that the heat dissipation member is a copper post formed vertically in the substrate.

  In another aspect of the electronic substrate of the present invention, the heat dissipation member is a through hole formed in the substrate.

  Another aspect of the electronic substrate of the present invention is characterized in that the coil is a transformer in which a primary coil and a secondary coil are formed in different conductor layers.

  Another aspect of the electronic substrate of the present invention is characterized in that the transformer is formed on four or more conductor layers.

  Another aspect of the electronic substrate of the present invention is characterized in that the coil is a smoothing choke coil.

  Another aspect of the electronic substrate of the present invention is characterized in that the smoothing choke coil is composed of a coil formed in two or more conductor layers.

  Another aspect of the electronic substrate of the present invention is characterized in that the conductor layer has a thickness of 0.1 mm or more and 1 mm or less.

  In another aspect of the electronic substrate of the present invention, the cooling member is a coil extension portion formed at a predetermined position between a start point and an end point of the coil.

  Another aspect of the electronic substrate of the present invention is characterized in that the coil extension portion is formed at least at a substantially central portion between a start point and an end point of the coil.

  In another aspect of the electronic substrate according to the present invention, two or more formations are disposed in the approximate center position and the outer periphery of the coil, and the coil extension portion is disposed in a position not overlapping the formation. It is characterized by that.

  Another aspect of the electronic substrate of the present invention is characterized in that the formation is a through hole for allowing a predetermined magnetic material to pass therethrough.

  Another aspect of the electronic substrate of the present invention is characterized in that the width of the coil extension portion is increased as the distance from the start point or end point of the coil increases.

  According to the electronic substrate of the present invention, it is possible to efficiently dissipate heat generated by the coil formed by the circuit pattern of the substrate.

  A configuration of an electronic substrate in a preferred embodiment of the present invention will be described in detail with reference to the drawings. In addition, about each structural part which has the same function, the same code | symbol is attached | subjected and shown for simplification of illustration and description.

  In the electronic board of the present invention, a coil and a circuit element are mounted on the same board, and heat generated in the coil is transmitted to the circuit element via a wiring circuit that electrically connects the coil and the circuit element. The circuit element is configured to be prevented from being heated to a high temperature. Hereinafter, a DC-DC converter used for a hybrid vehicle as an electronic substrate will be described as an example.

  An electronic substrate according to a first embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a cross-sectional view showing a schematic configuration of a DC-DC converter 100 which is an example of the electronic substrate of the present embodiment. The DC-DC converter 100 includes a switching MOS-FET 110 and a rectifying diode 130 as circuit elements, and includes a voltage conversion transformer 120 and a smoothing choke coil 140 as coils.

  The MOS-FET 110 and the diode 130 are mounted on the substrate 101, and the transformer 120 and the choke coil 140 are formed on the substrate 101 by wiring, and these are electrically connected by the wiring circuits 152 to 154. Yes. Further, a wiring circuit 151 for supplying power to the MOS-FET 110 from the outside and a wiring circuit 155 for supplying power from the choke coil 140 to the outside are provided. The wiring circuits 151 to 155 can be provided by forming a pattern on the substrate 101, for example.

  In the DC-DC converter 100 used for a hybrid vehicle or the like, the voltage and current input to the MOS-FET 110 are, for example, 288V / 20A, and the voltage and current output from the choke coil 140 are, for example, 15V / 100A. . The DC-DC converter 100 converts a high-voltage direct current into an alternating current by the MOS-FET 110, steps down the voltage by the transformer 120, rectifies the stepped-down alternating current by the diode 130, and smoothes it by the choke coil 140. As described above, since the DC-DC converter 100 operates at a high voltage and a large current, heat generated from each component increases. Especially, in the transformer 120 and the choke coil 140 that form a coil with a circuit pattern, the amount of generated heat cannot be ignored.

  In order to release the heat generated in each of the MOS-FET 110, the transformer 120, the diode 130, and the choke coil 140, conventionally, each of the MOSs configured and mounted to be individually cooled by the cooling unit 103. The FET 110 and the diode 130 are connected to the cooling unit 103 via a heat sink (not shown) attached to the surface. However, in order to ensure each insulation, the heat conductive insulation sheet is provided between the cooling parts 103. FIG.

  However, since the amount of heat generated in the transformer 120 and the choke coil 140 cannot be ignored due to the pattern thickness and width of the conductor, part of the heat generated in the transformer 120 and the choke coil 140 passes through the wiring circuits 152 to 154 and the MOS-FET 110. And conducted to the diode 130 (see FIG. 12). Since the MOS-FET 110 and the diode 130 are heated by the transformer 120 and the choke coil 140 in addition to their own heat generation, the temperature becomes even higher.

  Therefore, in the DC-DC converter 100 of the present embodiment, the heat radiating members 161 to 163 are formed so as to be able to radiate heat to the cooling unit 103 from one end side. The heat radiating members 161 to 163 are arranged such that one ends thereof are in contact with the cooling unit 103 with the heat conductive insulating sheet 102 interposed therebetween. The other ends of the heat radiation members 161 to 163 are connected to the wiring circuits 152 to 154, respectively. Here, the heat radiation members 161 to 163 are provided in all the wiring circuits 152 to 154, but may be appropriately omitted depending on the heat radiation amount or the like.

  By disposing the heat dissipating members 161 to 163 as described above, heat conducted through the wiring circuits 152 to 154 can be released to the cooling unit 103 via the heat dissipating members 161 to 163. That is, most of the heat conducted from the transformer 120 and the choke coil 140 through the wiring circuits 152 to 154 to the circuit element side is conducted to the heat radiating members 161 to 163 on the way and released to the cooling unit 103.

  FIG. 2 schematically shows a state where heat generated by the MOS-FET 110, the transformer 120, the diode 130, and the choke coil 140 is conducted through the wiring circuits 152 to 154 and the heat radiation members 161 to 163. In FIG. 2, a large amount of heat generated in the transformer 120 and the choke coil 140 is conducted to the wiring circuits 152 to 154 to the MOS-FET 110 and the diode 130 side. A state where heat is radiated to the portion 103 is shown. Since one end side of the heat radiation members 161 to 163 is cooled by the cooling unit 103, more heat can be conducted to the cooling unit 103 side than conducted to the MOS-FET 110 and the diode 130 side.

  As the heat radiating members 161 to 163, copper posts can be formed in the substrate 101 and used. Alternatively, a through hole may be formed in the substrate 101 and used. One end side of the heat radiating members 161 to 163 is electrically insulated by disposing a heat conductive insulating sheet between the heat radiating members 161 to 163. On the other hand, the other end side of the heat radiation members 161 to 163 is directly connected to the wiring circuits 152 to 154 and is in a conductive state. Thereby, thermal conductivity can also be improved.

In the embodiment shown in FIG. 1, the heat dissipation members 161 to 163 are connected to the wiring circuits 152 to 154, but as another embodiment, the heat dissipation members are also connected to the wiring circuit 151 and / or the wiring circuit 155. You may do it. Further, another heat dissipating member may be connected below the MOS-FET 110 and the diode 130 that are conventionally thermally connected to the cooling unit 103 via a heat sink (not shown). Another heat dissipating member can be connected to the MOS-FET 110 and the diode 130 via the wiring circuits 151 to 155, or can be directly connected to the MOS-FET 110 and the diode 130 without passing through the wiring circuits 151 to 155. .
FIG. 3 shows an embodiment in which a heat radiating member is connected to both the wiring circuits 151 and 155, and another heat radiating member is connected below the MOS-FET 110 and the diode 130 via the wiring circuit. As shown in FIG. 3, heat radiation members 164 and 165 are provided in the wiring circuits 151 and 155 which are input / output portions of the DC-DC converter 100 ′, and another heat radiation is performed under the MOS-FET 110 and the diode 130 via the wiring circuit. By providing the members 171 and 172, the cooling effect of the MOS-FET 110, the diode 130, and the choke coil 140 can be further enhanced, and as a result, the temperature of the substrate 101 can be lowered.

  An electronic substrate according to a second embodiment of the present invention will be described below with reference to FIGS. 4 and 5 are a cross-sectional view and a plan view showing a schematic configuration of a DC-DC converter 200 which is an example of the electronic substrate of the present embodiment. In this embodiment, a multilayer substrate having two or more conductor layers is used as a substrate on which circuit elements and coils are mounted. In the embodiment shown in FIG. 4, a multilayer substrate 201 composed of four conductor layers is used. The multilayer substrate 201 is composed of four conductive layers 202 and three insulating layers 203 for insulating between them.

  In the case where the coils constituting the voltage conversion transformer 220 and the smoothing choke coil 240 are formed with a circuit pattern of the substrate, a multilayer substrate 201 having four or more conductor layers 202 is required in order to reduce the necessary substrate area. Should be used. When the number of conductor layers 202 is four, the total thickness and the total weight of the multilayer substrate 201 are four times or more the thickness and weight per layer of the conductor layer 202. It is desirable to make it thinner. However, if the thickness of the conductor layer 202 is made too thin, the amount of heat generated from each coil of the transformer 220 and the choke coil 240 becomes large. Further, when the heat generated in the coil becomes excessive, the amount of heat conducted to the MOS-FET 210 and the diode 230 without moving from the wiring circuits 252 to 254 to the heat radiation members 261 to 263 increases, and these circuit elements are heated to a high temperature. It will become.

  When the thickness per one layer of the conductor layer 202 is less than 0.1 mm, a current of about 100 A that is generally energized by a DC-DC converter for a hybrid vehicle or the like is passed through a coil formed on the conductor layer 202. Then, the temperature of this coil exceeds 180 ° C., and reaches the melting temperature of the solder. When the thickness per one layer of the conductor layer 202 is about 0.3 mm, the temperature of the coil becomes 150 ° C. and a margin up to the melting temperature of the solder is obtained. In this case, since the range of selection of the insulating material used for the insulating layer 203 is widened, the cost of the DC-DC converter 200 can be reduced.

  On the other hand, if the thickness of one conductor layer 202 is 0.7 mm or more, the total thickness of the multilayer substrate 201 including the four conductor layers 202 and the insulating layer 203 exceeds 3.5 mm. The multilayer substrate 201 having such a thickness cannot be put into a normal etching apparatus, and a special apparatus is required, resulting in an increase in cost. Furthermore, if the thickness of the conductor layer 202 per layer is 1 mm or more, the total thickness of the multilayer substrate 201 is 5 mm or more, which necessitates the introduction of a new manufacturing apparatus and further increases the cost.

  An example of the relationship between the thickness of the conductor layer 202, the coil temperature, and the manufacturing cost is shown in FIG. The coil temperature decreases as the thickness of the conductor layer 202 increases. On the other hand, the manufacturing cost of the multilayer substrate 200 increases as the thickness of the conductor layer 202 increases, and particularly increases rapidly when the thickness of the conductor layer 202 exceeds 0.7 mm and exceeds 1 mm. ing.

  In the DC-DC converter 200 of the present embodiment, the thickness per layer of the conductor layer 202 is suitably set in consideration of the above-described circumstances, so that the amount of heat generated from the coil does not increase. In addition, it is possible to manufacture at a low cost. The thickness per layer of the conductor layer 202 of this embodiment is preferably 0.1 mm or more and 1 mm or less. More preferably, it is 0.3 mm or more and 0.7 mm or less.

  In the DC-DC converter 200 of the present embodiment shown in FIGS. 4 and 5, the first conductor layer 202a is used for the wiring circuits 251 to 255 that connect the components, and among these, the MOS-FET 210, Heat radiation members 261 to 263 are connected to wiring circuits 252 to 254 that mutually connect the transformer 220, the diode 230, and the choke coil 240. Further, under the MOS-FET 210 and the diode 230, other heat radiation members 271 and 272 are connected via a wiring circuit so as to be thermally connected to the cooling unit 103. Here, the heat radiation members 261 to 263 and 271 and 272 are arranged so as to be insulated from the second to fourth conductor layers 202b to 202d. Thereby, the heat generated in each coil of the transformer 220 and the choke coil 240 is conducted to the MOS-FET 210 and the diode 230 side via the wiring circuits 252 to 254, and most of the heat is released from the heat radiation members 261 to 263. So that the heat is dissipated to the cooling unit 103. Furthermore, the heat generated by the MOS-FET 210 and the diode 230 is also radiated to the cooling unit 103 via the separate heat radiation members 271 and 272. With such a structure, the temperature of the substrate 101 can be further lowered.

  One example of the heat radiating members 261 to 263 and 271 and 272 will be described in more detail with reference to FIG. The heat radiating member 260a shown in FIG. 7 is formed of a copper post provided on the multilayer substrate 201, and can be used for any of the heat radiating members 261 to 263. Here, it is assumed that the wiring circuits 251 to 255 are formed on the first conductor layer 202a. Further, portions of the conductor layer 202a other than the wiring circuits 251 to 255 and the conductor layers 202b to 202d are used to form a coil, another circuit, or the like. One end of the heat dissipating member 260a is in contact with the cooling unit 103 through the heat conductive insulating sheet 102, and the other end is connected to the first conductor layer 202a, that is, one of the wiring circuits 252 to 254 by solder 204. Yes. The outer periphery of the heat radiating member 260 a is also fixed to the multilayer substrate 201 with solder 204. However, the heat radiating member 260a and the second to fourth conductor layers 202b to 202d are insulated by the same insulating material as the insulating layer 203.

  In the above description, all of the wiring circuits 252 to 254 are formed on the first conductor layer 202a. However, the wiring circuit may be formed on another layer. The heat dissipation member 260a is provided between at least the conductor layer 202 on which the wiring circuit is formed and the heat conductive insulating sheet 102.

  Another embodiment of the heat dissipating members 261 to 263 and 271, 272 will be described in detail with reference to FIG. The heat radiating member 260b shown in FIG. 8 is used to electrically connect any of the wiring circuits 252 to 254 in addition to the function of radiating heat to the cooling unit 103. As an example, the wiring circuit 250a formed in the first conductor layer 202a is connected to the MOS-FET 210 or the diode 230, and the wiring circuit 250b formed in the fourth conductor layer 202d is the transformer 220 or the choke coil 240. It is assumed that it is connected to In this case, any of the wiring circuits 252 to 254 is formed by electrically connecting the wiring circuit 250a and the wiring circuit 250b. The heat radiation member 260b shown in FIG. 8 is also used for electrical connection between the wiring circuit 250a and the wiring circuit 250b.

  The heat radiating member 260b electrically connects the wiring circuit 250a and the wiring circuit 250b, and heat conducted from the transformer 220 or the choke coil 240 to the wiring circuit 250b to the cooling unit 103 via the thermally conductive insulating sheet 102. I try to dissipate heat. Thus, the amount of heat conducted from the wiring circuit 250b to the wiring circuit 250a and applied to the MOS-FET 210 or the diode 230 is reduced. The heat dissipating member 260b can be formed by providing a through hole in the multilayer substrate 201. A layer of solder 204 is formed on the inner wall of the through hole, whereby the wiring circuit 250a and the wiring circuit 250b are electrically connected and the thermal conductivity to the heat conductive insulating sheet 102 is enhanced. .

  In FIG. 8, the wiring circuit 250b connected to the transformer 220 or the choke coil 240 is preferably formed in the fourth conductor layer 202d on the cooling unit 103 side. Thereby, the heat conducted from the transformer 220 or the choke coil 240 is also radiated from the wiring circuit 250 b to the cooling unit 103 via the heat conductive insulating sheet 102.

  Next, an example of a coil formed using each conductor layer 202 of the multilayer substrate 201 will be described with reference to FIG. FIG. 9 is a cross-sectional view showing an embodiment of the transformer 220. However, in FIG. 9, the description of the insulating layer 203 disposed between the conductor layers 202 is omitted. The transformer 220 includes a primary coil 221 composed of coils 221a and 221b and a secondary coil 222 composed of coils 222a and 222b. The primary coil 221 on the high voltage side has coils 221a and 221b formed of, for example, a four-turn coil with a first conductor layer 202a and a fourth conductor layer 202d. The secondary coil 222 on the low voltage side is formed in, for example, a one-turn coil, with the coils 222a and 222b each including a second conductor layer 202b and a third conductor layer 202c.

  The coils 221a and 221b constituting the primary coil 221 are connected to the MOS-FET 210 via the wiring circuits 252a and 252b connected thereto, respectively, and the coils 222a and 222b constituting the secondary coil 222 are connected to each other. The wiring circuit 253a and 253b are connected to the diode 230. The coil 221 b formed on the fourth conductor layer 202 d is in direct contact with the heat conductive insulating sheet 102, and the heat generated here is released to the cooling unit 103 via the heat conductive insulating sheet 102.

  On the other hand, heat generated in the coil 221a on the primary coil 221 side formed in the first layer is released to the cooling unit 103 via the wiring circuit 252a and the heat dissipation member 261. Further, the heat generated in the coils 222a and 222b on the secondary coil 222 side formed in the second layer and the third layer is released to the cooling unit 103 through the heat radiating members 262a and 262b. Thus, both the coil 221 a on the primary coil 221 side and the coils 222 a and 222 b on the secondary coil 222 side have a heat dissipation path to the cooling unit 103.

  In the embodiment shown in FIG. 9, the heat radiating member 261 connected to the wiring circuit 252a has only the role of radiating the heat generated in the coil 221a on the primary coil 221 side to the cooling unit 103 side. The heat dissipating members 262a and 262b connected to the coils 222a and 222b on the secondary coil 222 side dissipate heat generated in the respective coils to the cooling unit 103 side, and the coils 222a and 222b and the wiring circuits 253a and 253b. Are also electrically connected to each other. As described above, by using the heat radiation members 261, 262 a, and 262 b, the heat generated in each coil can be efficiently released to the cooling unit 103 side, and the MOS-FET 210 and the diode 230 connected to the transformer 220. The heat transfer can be suppressed and reliability can be ensured.

  Next, an example of the choke coil 240 formed using each conductor layer 202 of the multilayer substrate 201 will be described with reference to FIG. FIG. 10A is a plan view showing an embodiment of the choke coil 240, and FIG. 10B is a cross-sectional view. However, the description of the insulating layer 203 disposed between the conductor layers 202 is omitted here. The choke coil 240 is composed of four coils 240a to 240d, which are formed on the first to fourth conductor layers 202a to 202d, respectively.

  The coil 240a is connected to the diode 230 via the wiring circuit 254, and is sequentially connected to the coils 240b to 240d via the through holes 241a to 241c. The coil 240d formed in the fourth layer is connected to the wiring circuit 255 via the through hole 241d and supplies power to the load. In the choke coil 240 of the present embodiment, a heat radiating member 263 is provided in the high-temperature wiring circuit 254 connected to the diode 230, and the heat is radiated from the heat radiating member 263 to the cooling unit 103 through the heat conductive insulating sheet 102. The Further, the coil 240d of the fourth layer is directly radiated to the cooling unit 103 via the heat conductive insulating sheet 102. Accordingly, the choke coil 240 is cooled from both sides of the first layer coil 240a and the fourth layer coil 240d.

  Another embodiment of the choke coil formed using each conductor layer 202 of the multilayer substrate 201 will be described with reference to FIG. FIG. 11A is a plan view showing a choke coil 240 ′ according to another embodiment, and FIG. 11B is a cross-sectional view. However, the description of the insulating layer 203 disposed between the conductor layers 202 is also omitted here. The choke coil 240 'is composed of four coils 240a to 240d as in the above embodiment, and is formed on each of the first to fourth conductor layers 202a to 202d.

  In this embodiment, the fourth layer coil 240 d is connected to the wiring circuit 254 via the heat dissipating member 273 and further connected to the diode 230. Further, the coils 240d are sequentially connected to the coils 240c to 240a through the through holes 241c to 241a. A coil 240a formed in the first layer is connected to the wiring circuit 255 and supplies power to the load. In the choke coil 240 ′ of the present embodiment, the heat radiation member 263 is provided in the high-temperature side wiring circuit 254 connected to the diode 230, and is connected to the fourth layer coil 240d that is in direct contact with the heat conductive insulating sheet 102. Thus, the high-temperature side wiring circuit 254 can be cooled more efficiently. In the present embodiment, the heat radiation member 263 conducts heat and electrically connects the wiring circuit 254 and the coil 240d.

  As described above, by connecting the heat radiating member 263 to the wiring circuit 254, the heat generated in the choke coil 240 can be efficiently released to the cooling unit 103 side, and the diode 230 connected to the choke coil 240 can be discharged. The heat transfer can be suppressed and reliability can be ensured.

  An electronic substrate according to the third embodiment of the present invention will be described below. In an electronic board with high current and high heat dissipation, it is better to make the conductor layer thinner for cost reduction and to increase the conductor width in order to improve heat dissipation. Conventionally, the conductor width of the coil portion could not be increased. An example of the arrangement of ferrite cores in a conventional choke coil is shown in FIG. FIG. 13 is a cross-sectional view showing an example of a conventional choke coil 800. The choke coil 800 has a coil pattern 801 formed on a conductor layer.

  In the center of the coil pattern 801, an insertion hole 811 for inserting a ferrite core is formed as a formed product, and insertion holes 812 and 813 are also formed on the left and right sides of the coil pattern 801. Accordingly, the coil pattern 801 needs to be disposed between the insertion hole 811 and the insertion hole 812, and between the insertion hole 811 and the insertion hole 813. Conventionally, the coil pattern 801 is not formed between the insertion hole 811 and the insertion hole 812. It was formed with a uniform width smaller than the distance (or the distance between the insertion hole 811 and the insertion hole 813). Therefore, the width of the coil pattern 801 is limited, and high heat dissipation cannot be realized. Therefore, in the second embodiment described above, for example, a heat dissipation member is connected to the wiring circuit 802 or 803 to improve heat dissipation to the cooling unit 103.

  On the other hand, in the coil provided on the electronic substrate of the present embodiment (hereinafter referred to as the coil of the present embodiment), in order to improve the heat dissipation from the coil pattern whose dimensions are restricted by the formation arranged in the periphery. In addition, a coil extension portion having a shape suitable for the coil pattern is added in place of the heat dissipating member described in the first or second embodiment. Hereinafter, the choke coil will be described as an example of the coil of the present embodiment. The choke coil of the present embodiment is configured to increase the heat dissipation of the coil pattern by adding a coil extension portion to the coil pattern portion that is not subjected to dimensional restrictions by a ferrite core or the like to increase the width. In particular, the heat dissipation is enhanced by adding a coil extension to the portion where the heat dissipation is low and the temperature is high, thereby increasing the coil width.

  In the conventional choke coil 800 shown in FIG. 13, the heat generation at the coil start point 801a and the coil end point 801b connected to the wiring circuits 802 and 803 is conducted and dissipated from the wiring circuits 802 and 803, so the temperatures are compared. The temperature increases as the distance from the coil start point 801a and the coil end point 801b increases. And the temperature of the coil center part 801c facing the coil start point 801a and the coil end point 801b becomes the highest.

  FIG. 14 shows a first example of the choke coil provided on the electronic board of the present embodiment in which the heat dissipation of the conventional choke coil 800 shown in FIG. 13 is improved. FIG. 14 is a plan view of the choke coil 300 of the present embodiment. In the choke coil 300 according to the present embodiment, the coil expansion portion 302 is formed in a portion (coil central portion) facing the coil start point 301a and the coil end point 301b of the coil pattern 301. As described above, the heat radiation from the coil pattern 301 decreases as the distance from the coil start point 301a and the coil end point 301b increases and the temperature increases, so that the coil width increases as the distance from the coil start point 301a and the coil end point 301b increases. The coil extension part 302 is formed in the upper part. As described above, in the choke coil 300 according to the present embodiment, the coil extension portion 302 is formed in the portions facing the coil start point 301a and the coil end point 301b, which conventionally have a low heat dissipation and a high temperature. It is possible to increase heat dissipation.

  FIG. 15 shows a second example of the choke coil provided on the electronic substrate of the present embodiment. FIGS. 15A and 15B are plan views of the choke coil 310 of the present embodiment, where FIG. 15A shows the first layer coil pattern 311 and FIG. 15B shows the second layer coil pattern 312. The coil pattern 311 of the first layer has a coil extension portion 313, like the coil pattern 300 of the first embodiment. On the other hand, the coil pattern 312 of the second layer has a uniform coil width as in the conventional coil pattern 801. The coil pattern 312 of the second layer is arranged so as to be in contact with the cooling unit 103, for example, similarly to the choke coil 140 provided in the electronic substrate 100 of the first embodiment. Therefore, heat generated in the coil pattern 312 is directly released to the cooling unit 103, and the temperature of the coil pattern 312 is kept low.

  As described above, in the choke coil having two or more layers of coil patterns, it is not necessary to provide a coil expansion portion to further improve the heat dissipation for the coil pattern having a separate heat dissipation means. In the present embodiment, the coil expansion portion 313 is formed only for the coil pattern 311 that does not have another heat radiating means, and this increases the temperature particularly in any of the coil patterns of the choke coil 310. The place can be lost.

  FIG. 16 shows a third example of the choke coil provided on the electronic substrate of the present embodiment. FIG. 16 is a plan view of the choke coil 320 of the present embodiment. In the choke coil 320 of this embodiment, ferrite core insertion holes 821 to 824 are provided in four directions so as to surround the coil pattern 321. Also in the present embodiment, the coil expansion portion 322 is formed between the insertion holes 821 and 824 facing the coil start point 321a and the coil end point 321b that are the highest temperature. In addition to this, in the choke coil 320 of this embodiment, coil expansion portions 323 and 324 are formed between the insertion holes 821 and 822 and between the insertion holes 823 and 824, respectively. The heat dissipation of the pattern 321 is further enhanced.

  FIG. 17 shows a fourth example of the choke coil provided on the electronic substrate of the present embodiment. FIG. 17 is a plan view of the choke coil 330 of the present embodiment. In the choke coil 330 of this embodiment, the ferrite core insertion hole 831 provided in the center of the coil pattern 331 is formed in a rectangular shape, and is symmetrical with respect to the central axis C between the coil start point 331a and the coil end point 331b. In addition, rectangular insertion holes 832 and 833 are provided. In contrast to such rectangular insertion holes 831 to 833, the coil pattern 331 of this embodiment is also formed in a rectangular shape surrounding the insertion hole 831. In the present embodiment in which the choke coil 331 is formed in such a shape, the coil extension portion 332 is formed on the side facing the coil start point 331a and the coil end point 331b, thereby increasing the coil width and improving heat dissipation. Can be increased.

  FIG. 18 shows a fifth example of the choke coil provided on the electronic substrate of the present embodiment. FIG. 18 is a plan view of the choke coil 340 of the present embodiment. In the choke coil 340 of the present embodiment, a rectangular ferrite core insertion hole 841 is formed so as to surround the coil pattern 341. In the choke coil 340 of the present embodiment having the insertion hole 841 having such a shape, the coil width can be reduced as much as possible by forming the coil expansion portion 342 at the coil central portion facing the coil start point 341a and the coil end point 341b that become high in temperature. The heat dissipation of the coil pattern 341 can be increased by increasing the size.

  FIG. 19 shows a sixth example of the choke coil provided on the electronic substrate of the present embodiment. FIG. 19 is a plan view of the choke coil 350 of the present embodiment. In the choke coil 350 of this embodiment, two ferrite core insertion holes 851 and 852 that restrict the width of the coil pattern 351 are provided symmetrically with respect to the central axis C between the coil start point 351a and the coil end point 351b. However, it is not provided on the side facing the coil start point 351a and the coil end point 351b. Therefore, in the choke coil 350 of the present embodiment, the coil expansion portion 352 is formed in the coil central portion on the side facing the coil start point 351a and the coil end point 351b, thereby increasing the coil width and improving the heat dissipation. When the insertion hole is not provided on the side facing the coil start point 351a and the coil end point 351b as in the present embodiment, it is preferable to make the width of the coil expansion portion 352 as large as possible, and the coil start point 351a and the coil end point 351a It is preferable to increase the width of the coil expansion part 352 sequentially from the end point 351b side toward the coil center part.

  Note that the description in the present embodiment shows an example of the electronic substrate according to the present invention, and the present invention is not limited to this. The detailed configuration, detailed operation, and the like of the electronic substrate in this embodiment can be changed as appropriate without departing from the spirit of the present invention.

It is sectional drawing which shows schematic structure of the DC-DC converter which is an Example of the electronic substrate which concerns on the 1st Embodiment of this invention. It is sectional drawing which shows typically the state of the heat conduction of a wiring circuit and a heat radiating member. It is sectional drawing which shows another Example of the electronic substrate which concerns on 1st Embodiment. It is sectional drawing which shows schematic structure of the DC-DC converter which is one Example of the electronic substrate which concerns on the 2nd Embodiment of this invention. It is a top view of the DC-DC converter which concerns on 2nd Embodiment. It is a figure which shows the relationship between the thickness of a conductor layer, coil temperature, and manufacturing cost. It is sectional drawing which shows one Example of a thermal radiation member. It is sectional drawing which shows another Example of a thermal radiation member. It is sectional drawing which shows one Example of a transformer. It is the top view and sectional drawing which show one Example of a choke coil. It is the top view and sectional drawing which show another Example of a choke coil. It is sectional drawing of the conventional electronic substrate. It is sectional drawing which shows an example of the conventional choke coil. It is a top view of the choke coil of the 1st example with which the electronic substrate concerning a 3rd embodiment was equipped. It is a top view of the choke coil of the 2nd example with which the electronic substrate concerning a 3rd embodiment was equipped. It is a top view of the choke coil of the 3rd example with which the electronic substrate concerning a 3rd embodiment was equipped. It is a top view of the choke coil of the 4th example with which the electronic substrate concerning a 3rd embodiment was equipped. It is a top view of the choke coil of the 5th example with which the electronic substrate concerning a 3rd embodiment was equipped. It is a top view of the choke coil of the 6th example with which the electronic substrate concerning a 3rd embodiment was equipped.

Explanation of symbols

100, 200 DC-DC converter 101 Substrate 102 Thermally conductive insulating sheet 103 Cooling unit 110, 210 Switching MOS-FET
120, 220 Voltage conversion transformer 130, 230 Rectifier diode 140, 240, 300, 310, 320, 330, 340, 350, 800
Smoothing choke coils 151-155, 251-255, 802, 803 Wiring circuits 161-165, 260-263 Heat radiation member 201 Multilayer substrate 202 Conductor layer 203 Insulating layer 204 Solder 221 Primary coil 222 Secondary coils 301, 311, 312 , 321, 331, 341, 351, 801
Coil pattern 302, 313, 322-324, 332, 342, 352 Coil expansion part 811-813, 821-824, 831-833, 841, 851, 852
Insertion hole

Claims (16)

An electronic substrate having one or more conductor layers in which a coil is formed with a circuit pattern,
A wiring circuit electrically connected to the coil;
An electronic board comprising: a heat radiating member formed to be able to radiate heat from at least one of the coil and the wiring circuit. One end of the heat radiating member is formed to be able to radiate heat to a predetermined cooling part, and the other end is connected to the wiring circuit. A circuit element is mounted and connected to the wiring circuit,
The heat sink according to claim 2, further comprising: another heat dissipating member formed so that one end can dissipate heat to the predetermined cooling unit and the other end can dissipate heat from the circuit element. Electronic substrate 4. Another wiring circuit formed so that heat can be radiated to the predetermined cooling portion is further connected to one end side of the heat radiating member or the other heat radiating member. Electronic board as described in The electronic substrate according to any one of claims 2 to 4, wherein the heat dissipation member is a copper post formed vertically in the substrate. The electronic substrate according to claim 2, wherein the heat dissipation member is a through hole formed in the substrate. The electronic board according to any one of claims 1 to 6, wherein the coil is a transformer in which a primary coil and a secondary coil are formed in different conductor layers. The electronic board according to claim 7, wherein the transformer is formed in four or more conductor layers. The electronic board according to claim 1, wherein the coil is a smoothing choke coil. The electronic substrate according to claim 9, wherein the smoothing choke coil is configured by a coil formed in two or more conductor layers. The thickness of the said conductor layer is 0.1 mm or more and 1 mm or less. The electronic board | substrate of any one of the Claims 1 thru | or 10 characterized by the above-mentioned. The electronic board according to claim 1, wherein the cooling member is a coil extension portion formed at a predetermined position between a start point and an end point of the coil. The electronic board according to claim 12, wherein the coil extension portion is formed at least at a substantially central portion between a start point and an end point of the coil. The two or more formations are arrange | positioned in the approximate center position and outer periphery vicinity of the said coil, The said coil expansion part is arrange | positioned in the position which does not overlap with the said formation. The electronic substrate as described. The electronic substrate according to claim 14, wherein the formation is a through hole for allowing a predetermined magnetic material to pass therethrough. The electronic board according to any one of claims 12 to 15, wherein a width of the coil extension portion is increased as the distance from the start point or end point of the coil increases.

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