JP2005235840A - Printed board, and heat radiator of heating electronic component mounted thereon - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printed board which conducts heat generated from a heating electronic component mounted thereon from the component mounting face to the opposite face to effectively radiate the heat, and to provide a heat radiator of the heating electronic component mounted thereon. <P>SOLUTION: In the component mounting face of the printed board 2 whereon a semiconductor device 4 which is the heating electronic component is to be mounted, a hexagonal through-hole 1 is formed. Heat generated from the heating electronic component is conducted via a conduction surface 6 formed on the inner wall of the through-hole 1 to a metal plate 3 in contact with and arranged on the opposite face of the printed board 2 to be radiated. Many through-holes 1 might be formed adjacent to each other in the heating electronic component mounting section. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a printed circuit board and a heat dissipation device for a heat generating electronic component mounted thereon, and in particular, dissipates heat generated from a heat generating electronic component such as a semiconductor device mounted on the printed circuit board to keep the temperature of the heat generating electronic component below a predetermined value. The present invention relates to a heat dissipation device for a printed circuit board and a heat generating electronic component mounted thereon.

  Electronic devices, particularly portable electronic devices such as mobile phones, are becoming smaller and higher performance. These electronic devices use one or more semiconductor integrated circuits (ICs) on which a large number of active devices are mounted at high density. These semiconductor devices are generally mounted on a printed circuit board (or printed wiring board) together with other active devices and passive electronic components to form an electronic circuit.

  For example, in an electronic device that requires high output, such as a mobile phone base station that constructs a mobile phone communication network for wireless communication with a mobile phone terminal in a service area, the amount of heat generated by the semiconductor device used increases. Since these semiconductor devices have higher reliability when their own temperature is lower, efforts are made to lower the temperature of the semiconductor devices during device design.

  In mounting a semiconductor device having a large amount of heat generation, a heat dissipation means for efficiently radiating the generated heat is taken. A printed wiring board that improves thermal conductivity in order to dissipate heat generated by a semiconductor device mounted on the printed board is disclosed (for example, see Patent Document 1).

  A conventional example of a mounting technique for a printed circuit board for improving heat dissipation characteristics and a semiconductor device using the printed circuit board will be briefly described. When soldering and mounting a semiconductor device with such heat generation on a printed circuit board, one or more through-holes are provided in the semiconductor device mounting portion of the printed circuit board, and the metal plate on which the semiconductor device and the printed circuit board are mounted Ensure heat dissipation path to.

  With reference to FIG. 6 and FIG. 7, the conventional through-hole of a general printed circuit board and the mounting technique of the semiconductor device to the printed circuit board are demonstrated. FIG. 6 is a plan view of one general through hole formed in a printed circuit board. The through hole 60 is a circular opening penetrating from one surface of the printed board to the opposite surface, and a thin conductive layer 61 such as copper is formed on the inner wall thereof by plating. The center of the through hole 60 is a hollow portion 62.

  As shown in FIG. 6, a general through hole 60 of the printed circuit board has a dimension from the center to the outer wall of the through hole 60 (that is, the radius of the through hole 60), and from the center to the inner wall of the conductive layer 61. The dimension of b is b.

  In the prior art described above, a semiconductor device is mounted on one surface of a printed circuit board on which a large number of through holes 60 are formed as shown in FIG. 7, and heat generated by the semiconductor device is generated on a thin copper foil plane pattern formed on this surface. Further, heat is radiated from the planar pattern to the thin copper foil planar pattern formed on the opposite surface of the printed circuit board through the plated layer of the through hole 60 to dissipate heat generated by the semiconductor device. When a large number of through holes 60 adjacent to each other are formed on the printed board for the purpose of heat dissipation of the semiconductor device, the minimum interval between the adjacent through holes is s.

Japanese Patent Laid-Open No. 9-148691 (page 3-4, FIG. 1)

  With the heat dissipation technique described above, the heat of the semiconductor device can be efficiently dissipated by the high thermal conductivity of the conductive layer 61 at the temperature of the semiconductor device. However, even with this heat dissipation means, there is a problem that heat dissipation is insufficient to keep the temperature of heat-generating electronic components such as high-performance semiconductor devices mounted at high density such as mobile phone base stations as described above below a predetermined value. It was.

  The present invention has been made in view of the above-described problems of the prior art, and efficiently generates heat from a heat generating electronic component mounted on a printed circuit board to reduce the temperature of the heat generating electronic component to a predetermined value or less. It is an object of the present invention to provide a printed circuit board to be suppressed and a heat dissipation device for a heat generating electronic component mounted thereon.

  In order to solve the above-described problems, the printed circuit board according to the present invention and the heat dissipating device for the heat generating electronic components mounted thereon employ the following characteristic configuration.

(1) In a printed circuit board on which at least one active electronic component and passive electronic component are mounted on a component surface to form an electronic circuit,
A hexagonal through hole is formed on the opposite surface from the component surface, a conductive surface is formed on the inner wall of the through hole, and heat generated by the electronic component mounted on the component surface is transmitted through the conductive surface of the through hole. A printed circuit board that conducts to the opposite side.

  (2) The print according to (1), wherein the through hole is formed so that a plurality of through holes are formed adjacent to each other substantially corresponding to a contact area of the electronic component mounted on the component surface with the component surface. substrate.

  (3) The printed circuit board according to (2), wherein the plurality of through holes are formed such that the centers of three adjacent through holes are positioned at the apexes of an equilateral triangle.

(4) The printed circuit board according to (1), (2), or (3), wherein a good heat conductive filling is provided in the central opening of the through hole.

(5) In a discharge device for a heat generating electronic component that dissipates heat generated by a heat generating electronic component mounted on a printed circuit board and keeps the temperature of the heat generating electronic component below a predetermined value.
A metal plate that conducts heat generated by the heat generating electronic component to the component surface of the printed circuit board, and a conductive surface formed on an inner wall that conducts heat conducted to the metal plate from the component surface to the opposite surface of the printed circuit board. A heat dissipating device for a heat generating electronic component comprising a hexagonal through hole.

  (6) The heat dissipating device for heat-generating electronic components according to (5) above, wherein a metal plate having good heat conductivity is disposed on the opposite surface of the printed circuit board.

  (7) The heat dissipating device for a heat generating electronic component according to (5) or (6), wherein a plurality of the through holes of the printed circuit board are formed on substantially the entire contact surface of the heat generating electronic component with the printed circuit board.

  (8) The heat dissipating device for a heat-generating component according to (5), (6), or (7), wherein a material having good heat conductivity is packed in the opening of the through hole of the printed board.

  According to the printed circuit board of the present invention and the heat dissipating device for the heat generating electronic components mounted thereon, the following remarkable practical effects can be obtained. That is, a hexagonal through hole is formed in the mounting portion of the heat generating electronic component, and the heat generation of the heat generating electronic component is opposed to the component surface of the printed circuit board on which the heat generating electronic component is mounted mainly by the conductive surface formed on the inner wall. It is possible to dissipate heat by conducting heat to the surface with lower thermal conductivity than the conventional circular through hole. Furthermore, a large number of hexagonal through-holes are formed at a high density in the mounting portion of the heat generating electronic component, and heat generated from the heat generating electronic component can be transferred to and dissipated from the metal plate placed in contact with the opposite surface of the printed circuit board. Is possible.

  Hereinafter, the configuration and operation of a preferred embodiment of a printed circuit board according to the present invention and a heat dissipation device for heat-generating electronic components mounted thereon will be described in detail with reference to the accompanying drawings.

  First, FIG. 1 shows a heat dissipation device for heat generating electronic components mounted on a printed circuit board according to a first embodiment of the present invention. The heat dissipating device 10 for heat generating electronic components dissipates heat generated by a heat generating electronic component mounted on the printed circuit board 2, for example, a substantially rectangular semiconductor device 4, and the temperature of the heat generating electronic component 4 is reduced to a predetermined value or less. It is a device that suppresses and maintains its reliability. FIG. 1A is a perspective view of a heat dissipation device for a heat generating electronic component including a heat generating electronic component 4 mounted on the printed circuit board 2, and FIG. 1B is a heat generating electronic component (see FIG. 1B) before being mounted on the printed circuit board 2. (Or semiconductor device) 4 is a perspective view.

  The heat generating electronic component 4 shown in FIG. 1B is mounted on the component surface (the upper surface in FIG. 1A), which is the surface on which the heat generating electronic component 4 of the printed board 2 is mounted. A large number of regular hexagonal through-holes 1 are formed in the mounting portion of the printed circuit board 2 in a honeycomb shape. The printed circuit board 2 on which the heat generating electronic component 4 is mounted is placed on the metal plate 3. The heat generating electronic component (semiconductor device) 4 has a metal plate 5 for heat dissipation on the mounting surface to the printed circuit board 2 as shown in FIG. The heat generating electronic component 4 is mounted on the printed circuit board 2 together with the metal plate 5 by soldering, for example.

  Next, with reference to the flowchart shown in FIG. 2, the process of radiating the heat generated from the semiconductor device 4 which is a heat generating electronic component by the heat dissipation device 10 for the heat generating electronic component of the present invention will be described. When the semiconductor device 4 is operated, heat is generated (step S1). The heat generated from the semiconductor device 4 is thermally conducted to the heat radiating metal plate 5 provided on the mounting surface of the semiconductor device 4 on the printed board 2 (step S2). The heat conducted to the heat radiating metal plate 5 is conducted to the mounting surface of the semiconductor device 4 on the printed circuit board 2 to which the heat radiating metal plate 5 is soldered (step S3).

  Next, the heat of the component surface of the printed circuit board 2 is conducted through the conductive surface 6 plated on the inner wall of the through hole 1 to the opposite side of the component surface of the printed circuit board 2 (hereinafter referred to as the opposite surface of the printed circuit board 2). (Step S4). Furthermore, the heat on the opposite surface of the printed circuit board 2 is in contact with the metal plate 3, and is radiated to the metal plate 3 (step S5). The metal plate 3 is formed of a metal having a sufficient mass or volume (that is, area and thickness) and good heat dissipation characteristics, and efficiently dissipates heat generated by the semiconductor device 4.

Here, the heat conduction characteristics of the through hole 1 will be described. The conventional through hole 60 as shown in FIGS. 6 and 7 has a circular shape, and when the outer peripheral radius is a and the inner peripheral radius is b, the contact area of the semiconductor device 4 with the metal plate 5 for heat dissipation is π. (A ² -b ² ). On the other hand, in the case of the regular hexagonal through-hole 1 as shown in FIG. 3A, the distance from the center to each side of the outer regular hexagon is a, and the distance to each side of the inner regular hexagon is b. Then, the contact area of the semiconductor device 4 with the heat radiating metal plate 5 is (12 / (2 * √3)) * (a ² −b ² ). That is, by changing the shape of the through hole from a circle to a regular hexagon, (12 / (2 * √3)) / π≈1.1, that is, the contact area can be increased by about 10%. It is possible to reduce the thermal resistance from 4 to the component surface of the printed circuit board 2.

Further, the improvement of the heat radiation characteristic from the component surface to the opposite surface of the printed circuit board 2 will be described with reference to FIG. The heat radiation from the component surface of the printed circuit board 2 to the opposite surface mainly uses the conduction surface 6 of the through hole 1 as a heat radiation path, so that the thermal resistance is proportional to the length of the conduction surface 6 and inversely proportional to the cross-sectional area. That is, the thermal resistance θ is given by the following (Equation 1).
θ = α * (t / (l * d)) (Equation 1)
Here, t is the length of the heat conduction surface, and in the case of this specific example, the thickness of the printed circuit board 2.
l is the inner peripheral length of the conduction surface 6 of the through hole 1
d is the thickness of the conduction surface 6 of the through hole.
α is a coefficient and depends on the conductor material

  In (Equation 1) described above, l varies depending on the shape of the through hole 1, but α, t, and d do not depend on the shape of the through hole 1, so only l is compared. In the case of a circular through hole, l is equal to the circumference of radius b and is 2 * π * b. On the other hand, in the case of a regular hexagonal through hole, l is equal to the outer periphery of a regular hexagon whose distance from the center to one side is b (12 / √3) * b. Accordingly, the thermal resistance of the regular hexagonal through hole 1 is ((12 / √3) * b) / (2 * π * b) ≈1.1, that is, about 10%.

  As described above, since the heat resistance from the semiconductor device 4 to the metal plate 3 can be lowered by the hexagonal through hole 1, it is possible to effectively dissipate the heat generated by the semiconductor device 4 and lower its temperature. The long-term reliability of the semiconductor device 4 is improved. Further, in the case where the temperature of the semiconductor device 4 is the same as that of the conventional device, that is, the same long-term reliability, the cost can be reduced and the size can be reduced by removing the heat radiating fan. Furthermore, if a through-hole 1 in the printed circuit board is filled with a heat conductive material to improve heat dissipation, the cost of the circuit board is reduced because it is no longer necessary, and components that have been mounted on conventional metal plates Can be mounted on a printed circuit board, the manufacturing process can be simplified and the manufacturing cost can be reduced.

  Next, with reference to FIG. 4, a heat radiating device for heat generating components mounted on a printed circuit board according to a second embodiment of the present invention will be described. For convenience of explanation, the same reference numerals are used for corresponding elements. In this embodiment, the basic configuration is the same as that of the heat-radiating device 10 for heat-generating electronic components shown in FIG. 1, but has a good heat-conductive padding 7 in the opening of the regular hexagonal through-hole 1. The padding 7 can further reduce the thermal resistance from the component surface of the printed circuit board 2 to the opposite surface. Also in this embodiment, the circular through hole 60 is filled with a cylindrical material, but if the regular hexagonal through hole 1 is filled with a regular hexagonal columnar material, the cross-sectional area of the material is (12 / (2 * √3 )) / Π≈1.1, that is, about 10% larger, so that the thermal resistance can be reduced accordingly.

  Next, a heat dissipation device for heat generating electronic components mounted on a printed circuit board according to a third embodiment of the present invention will be described. In the first embodiment and the second embodiment described above, heat conduction is performed from the component surface of the printed circuit board 2 to the opposite surface by one hexagonal through hole 1, but when the semiconductor device 4 is large, As shown in FIG. 5, a large number of hexagonal through holes 1 may be formed in the mounting portion of the semiconductor device 2. In this case, the distance between the centers of the regular hexagons of the three through holes 1 adjacent to each other is (2 * a + s). Here, s is the minimum conductor distance of the printed circuit board 2. That is, the plurality of regular hexagons are arranged so that the centers thereof coincide with the vertices of the regular triangle T whose one side is (2 * a + s). Also in this case, the contact area between the semiconductor device 4 and the printed circuit board 2 is (12 / (2 * √3)) / π≈1.1, that is, about 10 as compared with the case where circular through holes are arranged. % Can be widened, so the heat resistance can be lowered accordingly.

  The configuration and operation of the preferred embodiment of the printed circuit board according to the present invention and the heat dissipating device for heat generating electronic components mounted thereon have been described in detail. However, it should be noted that such examples are merely illustrative of the invention and do not limit the invention in any way. Those skilled in the art will readily understand that various modifications and changes can be made according to a specific application without departing from the gist of the present invention.

1 shows a preferred embodiment of a heat dissipation device for a heat generating electronic component mounted on a printed board according to the present invention, (A) is a perspective view of the heat dissipation device for the heat generating electronic component, and (B) is a heat generating electronic component before mounting on the printed circuit board. It is a perspective view. 3 is a flowchart illustrating a heat dissipation process of a heat dissipation device for heat-generating electronic components according to the present invention. The through-hole of 1st Example of the printed circuit board by this invention is shown, (A) is a top view of a through-hole, (B) is a perspective view of a through-hole. It is a perspective view of the through hole of 2nd Example of the printed circuit board by this invention. It is a top view which shows many through holes formed in the heat-emitting electronic component mounting part of the printed circuit board by this invention. It is a top view which shows one through hole formed in the conventional printed circuit board. It is a top view of the several through hole formed in the conventional printed circuit board.

Explanation of symbols

1 Through hole 2 Printed circuit board 3 Metal plate 4 Heating electronic component (semiconductor device)
5 Metal plate for heat dissipation 6 Conducting surface of through hole 7 Stuff with good heat conductivity 10 Heat dissipation device for heat generating electronic parts

Claims (8)

In a printed circuit board on which at least one active electronic component and passive electronic component are mounted on the component surface to form an electronic circuit,
A hexagonal through hole is formed on the opposite surface from the component surface, a conductive surface is formed on the inner wall of the through hole, and heat generated by the electronic component mounted on the component surface is transmitted through the conductive surface of the through hole. A printed circuit board that conducts to the opposite surface.   The plurality of through holes are formed adjacent to each other substantially corresponding to a contact area of the electronic component mounted on the component surface with the component surface. The printed circuit board described.   The printed circuit board according to claim 2, wherein the plurality of through holes are formed such that the centers of three adjacent through holes are located at the apexes of an equilateral triangle. The printed circuit board according to claim 1, wherein the through hole is provided with a pad with good thermal conductivity in the center opening. In a discharge device for a heat generating electronic component that dissipates heat generated by a heat generating electronic component mounted on a printed circuit board and keeps the temperature of the heat generating electronic component below a predetermined value,
A metal plate that conducts heat generated by the heat generating electronic component to the component surface of the printed circuit board, and a conductive surface formed on an inner wall that conducts heat conducted to the metal plate from the component surface to the opposite surface of the printed circuit board. A heat dissipating device for a heat generating electronic component comprising a hexagonal through hole.   6. The heat dissipation device for heat-generating electronic components according to claim 5, wherein a metal plate having good heat conductivity is disposed on the opposite surface of the printed circuit board.   The heat dissipation device for a heat generating electronic component according to claim 5 or 6, wherein a plurality of the through holes of the printed circuit board are formed on substantially the entire contact surface of the heat generating electronic component with the printed circuit board.   The heat dissipation device for a heat-generating component according to claim 5, 6 or 7, wherein a material having good heat conductivity is packed in the opening of the through hole of the printed circuit board.

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