JP5885630B2 - Printed board - Google Patents

Description

  The present invention relates to a printed circuit board, and more particularly, to a printed circuit board including an electronic component soldered to a main surface of a circuit substrate.

  There is a method of reducing the temperature of an electronic component by natural convection on the printed circuit board with respect to a temperature rise when the electronic component is energized in a printed circuit board including the electronic component. If this is insufficient, there is a method of dissipating heat by connecting a heat dissipating member to the back side of the printed board.

  For example, in Japanese Patent Application Laid-Open No. 2010-109036, a heat conductive member is provided in a through hole formed in a circuit substrate, and terminal patterns connected to the heat conductive member are provided on both sides of the circuit substrate to generate heat. The element is soldered to the terminal pattern.

  As for soldering, the method of simultaneously soldering a plurality of locations by the reflow soldering method or the like is more advantageous from the viewpoint of manufacturing cost as compared with the method of soldering individually. In this case, members located around the heat conductive member are also heated at the same time.

JP 2010-109036 A

  However, since the heat conductive member has a high heat conductivity and a large heat capacity, when soldering an electronic component by the reflow soldering method, the heat conductive member is provided around the heat conductive member. The circuit pattern rises faster. Therefore, the solder applied on the heat conductive member flows to the surrounding circuit pattern, and the gap portion may spread at the joint between the electronic component and the heat conductive member after soldering.

  As a result, the heat dissipation by the heat conductive member with respect to the electronic component is lowered, and the temperature of the electronic component is increased. Furthermore, there exists a problem that durability falls by connecting strength falling.

  The present invention has been made to solve the above-described problems. A main object of the present invention is to provide a printed circuit board having high heat dissipation properties for an electronic component and high connection strength between the electronic component and a circuit substrate.

A circuit substrate, an electronic component placed on the main surface of the circuit substrate, a heat dissipating member disposed on the back side facing the main surface of the circuit substrate in the thickness direction of the circuit substrate, and an electronic component And a heat conductive member for connecting the heat dissipating member. In the circuit base material, a through hole penetrating from the main surface to the back surface of the circuit base material is formed in a region where the electronic component is placed. The heat conductive member is provided in the through hole, and the end of the heat conductive member located on the main surface side is connected to the electronic component via solder, and the heat conductive member located on the back surface side The end is connected to the heat dissipation member. Furthermore, an outflow prevention member is provided on the main surface of the circuit substrate so as to surround the opening end of the through hole. A heat conductive member has a recessed part in the surface facing an electronic component.

  Thereby, it is possible to prevent the solder applied on the heat conductive member from flowing out to the surrounding pattern, and to suppress the generation of voids between the electronic component and the heat conductive member. The heat dissipation with respect to an electronic component and the connection strength of an electronic component and a circuit base material can be improved.

  According to the printed circuit board of the present invention, it is possible to prevent the solder applied on the heat conductive member from flowing out to the surrounding pattern, and to reduce the gap between the electronic component and the heat conductive member. Therefore, it is possible to improve the heat dissipation performance for the electronic component and the connection strength between the electronic component and the circuit substrate.

1 is a schematic cross-sectional view of a printed circuit board according to a first embodiment. It is a cross-sectional schematic diagram of the printed circuit board according to the second embodiment. It is a figure which shows the modification of FIG. It is a cross-sectional schematic diagram of the printed circuit board according to the third embodiment. FIG. 5 is a top view of FIG. 4.

  Embodiments of the present invention will be described below with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof will not be repeated.

(Embodiment 1)
Embodiment 1 of the present invention will be described below. First, the configuration of the printed circuit board 10 according to the first embodiment will be described with reference to FIG. A printed circuit board 10 according to the present embodiment includes a circuit substrate 11 having a main surface and a back surface that face each other in the thickness direction (vertical direction in FIG. 1). The circuit substrate 11 is formed with a through hole 12 penetrating the main surface side and the back surface side. Furthermore, the printed circuit board 10 according to the present embodiment includes an electronic component 30 provided on the through hole 12 on the main surface side of the circuit base material 11, and a heat dissipation member 50 provided on the back side of the circuit base material 11. The heat conductive member 13 provided in the through hole 12 and forming a heat path from the electronic component 30 to the heat radiating member 50 is further provided.

  The electronic component 30 includes a power semiconductor element such as a MOSFET, and generates heat when energized. In this case, for example, a power semiconductor element is soldered to the copper base of the electronic component 30 inside the electronic component 30 (not shown).

  With reference to FIG. 1, the circuit base material 11 is flat form and shows electrical insulation. The material of the circuit substrate 11 can be any material having electrical insulation, but may be a glass epoxy resin, for example. The circuit substrate 11 has a main surface and a back surface that face each other in the thickness direction (vertical direction in FIG. 1). In the circuit substrate 11, a through hole 12 penetrating the circuit substrate 11 is formed from the main surface to the back surface of the circuit substrate 11. Through hole 12 is formed as a round hole in a direction parallel to the main surface and the back surface. By making the hole diameter of the through hole 12 smaller than the outer shape of the electronic component 30, it is possible to adopt the existing circuit pattern 15 or the like without requiring any change.

  An electronic component 30 is provided on the through hole 12 on the main surface side of the circuit substrate 11. A circuit pattern 15 is formed on the main surface of the circuit substrate 11. The electronic component 30 and the circuit pattern 15 are electrically connected via the terminal 31, whereby the printed circuit board 10 according to the present embodiment operates electrically. For example, the power semiconductor element in the electronic component 30 and the terminal 31 are connected by wire bonding, and the terminal 31 and the circuit pattern 15 are connected by the solder 21. The circuit pattern 15 may be bordered by an insulating member 18 (outer peripheral side outflow prevention member). Thereby, when the circuit pattern 15 is adjacent to another circuit pattern, it is possible to prevent the solder 21 from flowing out and conducting between the circuit patterns. The insulating member 18 may be a resist, for example.

  The thermally conductive member 13 is disposed inside the through hole 12. The material of the heat conductive member 13 is an arbitrary material that exhibits a high thermal conductivity of several tens W / m · K or more. Preferably, the heat conductive member 13 is made of copper or aluminum having a heat conductivity of 100 W / m · K or more. The shape of the heat conductive member 13 can be any shape that can be fitted to the through hole 12, but preferably the through hole 12 is round and the heat conductive member 13 is cylindrical. Thereby, a solder can be spread | diffused uniformly at the time of a soldering process. Further, in this case, the through hole 12 can be easily formed by a drill, and the heat conductive member 13 can be easily manufactured by pressing.

  In the heat conductive member 13, the end portion located on the main surface side of the circuit substrate 11 is connected to the electronic component 30 via the solder 20. Further, in the heat conductive member 13, an end portion located on the back surface side of the circuit substrate 11 is connected via the heat radiating member 50 and the heat transfer material 40. At this time, the upper surface and the lower surface of the heat conductive member 13 may be curved. That is, the heat conductive member 13 can be easily manufactured by, for example, pressing a heat conductive plate member. The heat conductive member 13 produced by pressing is curved on two surfaces perpendicular to the pressurized direction, and a concave portion is formed on one surface and a convex portion is formed on the other surface. In this case, referring to FIG. 1, it is preferable to arrange the end portion on which the concave portion is formed on the main surface side of the circuit base material 11 and the end portion on which the convex portion is formed on the back surface side of the circuit base material 11. . If it does in this way, since the solder for joining the electronic component 30 and the heat conductive member 13 will be arrange | positioned at a recessed part, the outflow of solder can be suppressed at the time of a soldering process.

  In addition, it is preferable that the lower surface in which the convex part of the heat conductive member 13 was formed, and the back surface of the circuit base material 11 are formed on the same plane. Thereby, since the back surface of the circuit base material 11 and the back surface of the heat conductive member 13 can be provided at equal intervals with respect to the heat radiating member 50, the back surface of the heat conductive member 13 is more than the back surface of the circuit base material 11. The amount of heat transfer material 40 used can be reduced as compared with the case where the heat dissipating member 50 is separated.

A heat radiating member 50 is formed on the back surface side of the circuit substrate 11 via a heat transfer material 40.
As the heat transfer material 40, any material that can connect the back surface of the circuit substrate 11 and the heat radiating member 50 without a gap can be employed. For example, the heat transfer material 40 may be grease or an adhesive. In this case, the viscosity of the heat transfer material 40 is preferably several tens Pa · s or less, and more preferably 10 Pa · s or less. Further, the heat transfer material 40 may be a sheet or a tape. In this case, the heat transfer material 40 preferably has an Asker C hardness of 30 or less, more preferably 10 or less. By doing in this way, the space | gap between the through hole 12, the heat conductive member 13, and the heat radiating member 50 in the back surface side of the circuit base material 11 can be reduced, and heat dissipation can be improved.

  The heat radiating member 50 is made of a material having high thermal conductivity, and is made of, for example, copper or aluminum. Thereby, the heat generated in the electronic component 30 can be propagated to the heat radiating member 50 provided on the back surface side of the circuit substrate 11 through the heat conductive member 13 and the heat transfer material 40, and can be radiated. At this time, when the heat radiating member 50 has conductivity, the material of the heat transfer material 40 may be a silicon resin or epoxy resin material having electrical insulation and high heat dissipation. Moreover, the heat radiating member 50 may constitute a heat sink having fins or the like, and the cooling method may be air cooling or water cooling. When the heat radiating member 50 cannot be configured as a heat sink, for example, a heat transport mechanism made of a heat pipe or a carbon material may be provided to transport heat to a predetermined place and dissipate heat.

  An outflow prevention member 14 is formed on the main surface of the circuit substrate 11 and immediately below the electronic component 30 so as to surround the through hole 12. The outflow prevention member 14 suppresses the solder 20 applied on the heat conductive member 13 from flowing out to the surrounding members by heating the members around the heat conductive member 13 during the soldering process. Therefore, the outflow prevention member 14 can be made of any material capable of suppressing the outflow of the solder 20, and may be a resist, for example. As the resist, a general photoresist or a screen printing resist can be used. The shape of the outflow prevention member 14 can be any shape that can suppress the outflow of the solder 20, but may be a planar shape along the outer peripheral shape of the opening end portion of the through hole 12, and preferably a planar shape Is a circular shape. Thus, as described above, when the through hole 12 is formed in a round hole shape and the heat conductive member 13 is formed in a cylindrical shape so that the solder can be uniformly diffused during the soldering process, the diffused solder 20 Can be prevented from being partially concentrated. As a result, it is possible to suppress an increase in the gap between the electronic component 30 and the heat conductive member 13, and it is possible to increase heat dissipation with respect to the electronic component 30 and adhesion strength of the electronic component 30.

  Next, a method for manufacturing the printed circuit board 10 according to the present embodiment will be described. First, the circuit substrate 11 is prepared (S01). The circuit substrate 11 is prepared by, for example, bonding a copper foil or the like to the main surface and processing it into an arbitrary pattern, thereby preparing the circuit substrate 11 having the circuit pattern 15. At this time, when a large current of 200 A or more flows through the circuit pattern 15, it is preferable that the thickness of the circuit pattern 15 is 100 μm or more. The circuit pattern 15 may be formed on the circuit substrate 11 by plating or the like. However, when the circuit pattern 15 is formed with a thickness of 100 μm or more, the sheet-like circuit pattern 15 is pressure-bonded to the circuit substrate 11. The method is simple.

  Next, the through hole 12 is formed (S02). The through hole 12 is formed in the circuit substrate 11 on which the electronic component 30 is disposed so as to penetrate the main surface and the back surface of the circuit substrate 11. For example, the through hole 12 is formed by drilling the circuit substrate 11 using a drill.

  Next, the heat conductive member 13 is press-fitted into the through hole 12 (S03). The heat conductive member 13 is previously produced from a heat conductive plate member by press molding or the like. At this time, as described above, the thermal conductive member 13 is curved on two surfaces perpendicular to the direction of pressure applied at the time of production, and a concave portion is formed on one surface and a convex portion is formed on the other surface. The In this case, referring to FIG. 1, it is preferable to arrange the end portion on which the concave portion is formed on the main surface side of the circuit base material 11 and the end portion on which the convex portion is formed on the back surface side of the circuit base material 11. .

  Next, the outflow prevention member 14 is formed (S04). When the outflow prevention member 14 is formed as a resist, a resist is applied on the main surface of the circuit substrate 11 and the end portion where the recesses of the heat conductive member 13 are formed, and exposure and development are performed. A resist pattern is formed so as to surround the through hole 12. At this time, the thickness of the resist may be about 20 μm to 40 μm, for example.

  Next, solders 20 and 21 are applied on the main surface of the circuit substrate 11 (S05). The solder 20 is applied to a region where the electronic component 30 and the heat conductive member 13 are bonded, and the solder 21 is applied to a region where the terminal 31 and the circuit pattern 15 are bonded. At this time, the solders 20 and 21 may be applied using a mask formed with a uniform thickness on the main surface of the circuit substrate 11.

  Next, the electronic component 30 and the terminal 31 are soldered (S06). The electronic component 30 is joined to the heat conductive member 13 by the solder 20, and the terminal 31 is joined to the circuit pattern 15 by the solder 21. At this time, the reflow soldering method etc. are employ | adopted and the printed circuit board 10 whole can be heated, and a some solder joint location can be joined simultaneously. Even when the reflow soldering method is employed, the outflow prevention member 14 can suppress the solder 20 from flowing out to the periphery of the heat conductive member 13, and can reduce the gap generated immediately below the electronic component 30.

Next, the heat transfer material 40 and the heat dissipation member 50 are formed on the back surface side of the circuit substrate 11 (S07).
As described above, the printed circuit board 10 according to the present embodiment is on the main surface of the circuit base material 11, and immediately below the electronic component 30, the outflow prevention member 14 is formed so as to surround the through hole 12. ing. For this reason, the solder 20 flows out to the periphery of the heat conductive member 13 even when a method of heating and soldering the entire printed circuit board 10 such as a reflow soldering method is used for joining the electronic component 30 or the like. Can be suppressed. In the conventional printed circuit board that employs the reflow soldering method, it is possible to reduce voids that have occurred at the joint between the electronic component 30 and the heat conductive member 13. As a result, compared with the conventional printed circuit board, the heat dissipation with respect to the electronic component 30 can be increased, and the bonding strength of the electronic component 30 can be increased.

(Embodiment 2)
Next, a second embodiment of the present invention will be described with reference to FIG. 2 and FIG. The printed circuit board and the manufacturing method thereof according to the present embodiment basically have the same configuration as the printed circuit board and the manufacturing method thereof according to the first embodiment, but an electronic component is provided on the main surface side of the circuit substrate 11. The difference is that a circuit pattern 16 is formed which is thermally and electrically connected to 30 copper bases.

  When the heat conductive member 13 is small with respect to the electronic component 30 and the bonding area by the solder 20 is small, for example, when the outer shape of the electronic component 30 is 10 mm square or more, the diameter of the heat conductive member 13 is about 5 mm. In some cases, the circuit pattern 16 may be formed so as to surround the outer periphery of the heat conductive member 13, and the circuit pattern 16 and the electronic component 30 may be connected by the solder 22. Further, at this time, the circuit pattern 16 and the heat conductive member 13 may be connected thermally and electrically.

  The electronic component 30 in the present embodiment heats from the copper base of the electronic component 30 through the solder 22 and the circuit pattern 16 in addition to the heat path from the copper base of the electronic component 30 through the solder 20 to the heat conductive member 13. It has a heat path to the conductive member 13. In this case, the thermal resistance can be reduced by the newly provided heat path.

  In addition to the current path from the power semiconductor element to the circuit pattern 15 through the terminal 31, the electronic component 30 in the present embodiment has the circuit pattern 16 and the heat from the copper base of the electronic component 30 through the solders 20 and 22. It has a current path to the conductive member 13. Since the heat conductive member 13 can be used as a current path in addition to the circuit pattern 16, the electric resistance can be reduced. The circuit pattern 15 and the circuit pattern 16 are electrically insulated by the insulating member 18. For example, a part of the insulating member 18 is formed so as to surround the outer periphery of the circuit pattern 16. A part of the insulating member 18 is formed so as to surround the outer periphery of the circuit pattern 15.

  Referring to FIG. 2, conductive film 17 may be formed on the side wall of through hole 12. The conductive film 17 plays a role of electrically connecting the circuit pattern 16 to the heat conductive member 13 and the solder 20. As a result, the circuit pattern 16 and the heat conductive member 13 and the solder 20 can be connected well, and the electrical resistance can be reduced. As the conductive film 17, for example, a film made of a metal such as copper may be formed using, for example, a plating method. In this case, a conductive film is formed on the side wall of the through hole 12 after the step (S02) of forming the through hole 12 and before the step of pressing the heat conductive member 13 into the through hole 12 (S03). That's fine. In the present embodiment, the conductive film 17 may be provided on a part of the side wall of the through hole 12. Even if it does in this way, the circuit pattern 16, the heat conductive member 13, and the solder 20 can be connected favorably, and electrical resistance can be reduced.

  Also in the present embodiment, by providing the outflow prevention member 14 on the main surface of the circuit substrate 11 so as to surround the through hole 12, the solder 20 flows out around the heat conductive member 13. Can be suppressed. At this time, the outflow prevention member 14 may be formed on the conductive film 17 and the circuit pattern 16. As a result, the same effect as in the first embodiment can be obtained.

  Further, referring to FIG. 3, the outflow prevention member 14 may be formed so as to surround the through hole 12 outside the outer peripheral end portion of the through hole 12. By doing in this way, since the solder 20 is bonded to both the circuit pattern 16 and the heat conductive member 13, the circuit pattern 16, the heat conductive member 13, and the solder 20 can be satisfactorily connected. Electric resistance can be reduced. Also in this case, the outflow prevention member 14 can suppress the solder 20 from flowing out to the region on the outer peripheral side of the outflow prevention member 14 on the circuit pattern 16. As a result, the same effect as in the first embodiment can be obtained. In the example of FIG. 3, the conductive film is not formed on the side wall of the through hole 12, but a conductive film may be formed on the side wall.

(Embodiment 3)
Hereinafter, Embodiment 3 of the present invention will be described with reference to FIG. 4 and FIG. The printed circuit board and the manufacturing method thereof according to the present embodiment are basically provided with the same configuration as the printed circuit board and the manufacturing method thereof according to the second embodiment, but on the outer peripheral side of the outflow prevention member 14, The difference is that a via 70 is formed under the electronic component 30.

  FIG. 5 is a step (S05) of applying solder to the main surface of the circuit substrate 11 after the step (S04) of forming the outflow prevention member 14 in the method for manufacturing a printed circuit board according to the present embodiment. FIG. 3 is a top view when the previous printed circuit board 10 is viewed from the main surface side of the circuit substrate 11. A plurality of vias 70 are formed in a region surrounding the through hole 12 below the electronic component. The via 70 is formed so as to penetrate the circuit pattern 16. A plurality of circuit patterns 15 are formed surrounded by the insulating member 18.

  The via 70 can be formed in the same manner as the through hole 12 in the step of forming the through hole 12 (S02). For example, it can be formed by drilling the circuit substrate 11 using a drill. By introducing the solder 22 into the via 70, a new heat path from the electronic component 30 to the heat radiating member 50 through the solder 22 and the heat transfer material 40 can be provided, and the thermal resistance can be further reduced. .

  At this time, a back surface circuit pattern 19 that is electrically connected to the circuit pattern 16 may be provided on the back surface side of the circuit substrate 11. In this case, the solder 22 flowing into the via 70 can electrically connect the circuit pattern 16 and the back surface circuit pattern 19.

  A conductive film 71 may be formed on the sidewall of the via 70. The conductive film 71 plays a role of electrically connecting the circuit pattern 16 to the heat conductive member 13 and the solder 20. The material constituting the conductive film 71 can be, for example, copper plating. As a result, the circuit pattern 16, the back surface circuit pattern 19, and the solder 22 can be satisfactorily connected, and the electrical resistance can be reduced.

  Also in the present embodiment, by providing the outflow prevention member 14 on the main surface of the circuit substrate 11 so as to surround the through hole 12, the solder 20 flows out around the heat conductive member 13. Can be suppressed. As a result, the same effect as in the first and second embodiments can be obtained.

  The embodiments and examples disclosed herein are illustrative in all respects and should not be construed as being restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 10 Printed circuit board, 11 Circuit base material, 12 Through hole, 13 Thermal conductive member, 14 Outflow prevention member, 15, 16 Circuit pattern, 17, 71 Conductive film, 18 Insulating member (outer peripheral side outflow prevention member), 19 Back circuit pattern, 20, 21, 22 Solder, 30 Electronic component, 31 Terminal, 40 Heat transfer material, 50 Heat dissipation member, 70 Via.

Claims (10)

A circuit substrate;
An electronic component placed on the main surface of the circuit substrate;
A heat dissipating member disposed on the back side facing the main surface of the circuit substrate and the thickness direction of the circuit substrate;
A heat conductive member that connects the electronic component and the heat dissipation member;
In the circuit base material, a through hole penetrating from the main surface of the circuit base material to the back surface is formed in a region where the electronic component is placed,
The thermally conductive member is provided in the through hole,
The end of the thermally conductive member located on the main surface side is connected to the electronic component via solder, and the end of the thermally conductive member located on the back side is connected to the heat dissipation member. And
Furthermore, on the main surface of the circuit substrate, comprising an outflow prevention member formed so as to surround the opening end of the through hole ,
The thermal conductive member is a printed circuit board having a recess on a surface facing the electronic component .   The printed circuit board according to claim 1, wherein the outflow prevention member is formed along the opening end of the through hole on the main surface of the circuit base material.   The outer periphery side outflow prevention member which is located in the outer peripheral side of the said outflow prevention member on the said main surface of the said circuit base material, and is formed along the said opening edge part of the said through hole is further provided. Or the printed circuit board of 2. The planar shape of the through hole is circular,
The printed circuit board according to any one of claims 1 to 3, wherein the thermal conductive member is formed in a columnar shape and fits into the through hole. The outflow prevention member is disposed under the electronic component,
In a region located on the outer peripheral side of the outflow prevention member and below the electronic component, a via penetrating from the main surface of the circuit base material to the back surface is formed,
The via is filled with solder,
The printed circuit board according to claim 1, wherein the electronic component and the heat dissipation member are connected via the solder.   The printed circuit board according to claim 1, wherein the member constituting the outflow prevention member is a resist. The thermally conductive member has a convex portion on a surface facing the heat radiating member,
  The printed circuit board according to any one of claims 1 to 6, wherein a portion of the convex portion closest to the heat radiating member and the back surface of the circuit base material are formed on the same plane.   The printed circuit board according to claim 1, wherein a conductive film is formed on a side wall of the through hole. On the main surface of the circuit substrate, a circuit pattern is formed so as to surround the opening end of the through hole,
The printed circuit board according to claim 1, wherein the outflow prevention member is formed on the circuit pattern. On the back surface of the circuit substrate, a back circuit pattern is formed so as to surround the through hole,
The printed circuit board according to claim 1, wherein the heat dissipation member is connected to the back surface circuit pattern.

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