JPH06181396A - Heat pipe system cooling device for circuit board - Google Patents

Abstract

PURPOSE:To make thin the plate thickness of a circuit board without damaging the heat dissipation property of the circuit board as well as to make possible removal of a heat pipe by a method wherein the flat part of the heat pipe is connected to a heat dissipation plate on the upper part of a substrate having a circuit pattern on its surface. CONSTITUTION:A substrate 18 has a circuit pattern 12 consisting of a copper foil or the like on its surface and consists of an insulating sheet 13, a heat dissipation plate 19 consisting of oxygen free high conductivity copper for heat dissipation and an insulating substrate 16, which is provided under the lower part of the plate 19 and consists of a glass epoxy resin or the like. A heat pipe 17 with a section formed flatly is connected to the surface of the plate 19 by a solder 20 or the like. A semiconductor element 31 is placed on the upper surface of a circuit board 11, a heating part 32 on the lower surface of the board 11 is connected to a heating component mounting part 12a with an adhesive material 33 and lead parts 34 are connected to the pattern 12 and are used as lead parts for the semiconductor element. Heat of the mounting part 12a is transmitted to the pipe 17 via the plate 19 and is dissipated through a heat dissipation part of the pipe 17.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling device using a heat pipe for cooling a circuit board on which a large amount of heat such as a semiconductor element is mounted.

[0002]

2. Description of the Related Art A circuit board using a heat pipe has advantages such as high cooling efficiency and no need of power, and is used for cooling components such as semiconductor elements which generate a large amount of heat. As an example thereof, the present inventors have previously filed Japanese Patent Application No. 2-2
In No. 48644, "heat pipe embedded circuit board and its manufacturing method" was proposed. As shown in FIG. 8, this circuit board includes an insulating sheet 13 having a circuit pattern 12 on the surface of a board 18, an adhesive layer 14, and a metal plate 15 for soaking.
And the insulating substrate 16 are laminated and integrated, and the heat absorbing portion 17a of the heat pipe, which is formed flat so as to have a plane parallel to the surface of the substrate 18, is embedded in the insulating substrate 16.

The heat generated by a semiconductor element (not shown) mounted on the surface of the circuit pattern is absorbed by the heat absorbing portion of the flatly shaped heat pipe, and is radiated by the heat radiating portion at the end of the heat pipe for cooling. is there. This circuit board embeds the wide surface of the flat heat pipe on the heating surface side, so it has good thermal conductivity to the heat absorbing part, and the cooling effect is improved compared to the one using the conventional circular heat pipe. There is an advantage to However, the above heat pipe-embedded circuit board has a large thickness. For example, when the thickness is 3.0 mm, it is difficult for the lead wire of the component to penetrate the substrate, and it is not easy to mount the component. In addition, since the heat pipe cannot be removed, there is a problem in design, manufacturing and maintenance.

[0004]

As a result of studying the above problems, the present invention has developed a circuit board cooling device in which the thickness of the circuit board is thin, components can be easily mounted, and a heat pipe can be removed. It was done.

[0005]

According to the present invention, there is provided a heat pipe type cooling device for a circuit board, characterized in that a flat portion of a heat pipe is connected to a heat radiating plate on an upper portion of the board having a circuit pattern on its surface. The heat pipe type cooling device for a circuit board according to claim 1, wherein the heat pipe connecting surface of the heat radiating plate is formed with a depression. The heat pipe type cooling device for a circuit board according to claim 1, wherein the connection surface is formed with irregularities or a rough surface, and the heat pipe comprises at least one part of the heat pipe, A heat pipe type cooling device for a circuit board according to claim 1, which is formed by bending the circuit board above the circuit board.

[0006]

That is, in the circuit board cooling device of the present invention, the flat portion of the heat pipe is directly connected to the surface of the heat radiating plate of the heat absorbing portion of the circuit board, and the heat of the heating element is transferred by the heat pipe through the heat radiating plate. The circuit board is cooled by absorbing heat and radiating heat from the heat radiating portion at the other end of the heat pipe. Since this heat pipe is connected to the surface of the heat radiating plate adjacent to the heat generating element by solder or an adhesive, it can be removed and the design and manufacture are facilitated. Since the heat pipe is not embedded in the circuit board, the thickness of the circuit board is reduced by that much, which facilitates component mounting. Further, since the heat absorbing portion of the heat pipe is formed flat and the wide surface thereof is in contact with the heat radiating plate, the heat conductivity is good.

Further, by forming a recess on the heat pipe connection surface of the heat dissipation plate, the contact area with the heat pipe is increased and the thermal conductivity is further improved. Furthermore, by forming unevenness or a rough surface on the heat pipe connection surface of the heat dissipation plate, the contact area with the heat pipe is increased and the thermal conductivity is improved. In addition, the above-mentioned depression may be provided to further form an uneven surface or a rough surface. When the heat pipe connected to the surface of the heat dissipation plate is bent and formed above the circuit board, there is an advantage that a circuit pattern can be provided in this space.

[0008]

Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a partial sectional view showing an embodiment of a heat pipe type cooling device for a circuit board according to the present invention. This circuit board 11 has a circuit pattern 12 such as a copper foil on the surface of a board 18, an insulating sheet 13, a heat dissipation plate 19 made of oxygen-free copper for heat dissipation, and a glass epoxy resin etc. below the heat dissipation plate. Of the insulating substrate 16.
The circuit pattern 12, the insulating sheet 13, the heat dissipation plate 19 and the insulating substrate 16 are bonded to each other with an adhesive material (not shown). The heat pipe 17 having a flat cross section is formed on the surface of the heat dissipation plate 19.
They are connected by solder 20 or an adhesive material.

The semiconductor element 31 is placed on the upper surface of the circuit board 11 thus formed, and the heat generating portion 32 on the lower surface thereof is adhered to the heat generating component mounting portion 12a by the adhesive material 33 and the lead portion. 34 is connected to the circuit pattern 12 and is used for a semiconductor element. The heat of the heat generating component mounting part is transmitted to the heat pipe through the heat dissipation plate,
The heat is dissipated from the heat dissipating portion of the heat pipe.

On the heat dissipation plate 19 of this circuit board,
Oxygen-free copper or tough pitch copper with a thickness of 0.5 mm and 150 × 150 mm was used. Heat pipe is made of copper 3mm
The one with φ and 110 mm in length was annealed, flattened to a thickness of 2 mm, and the surface of which was plated with nickel.
The copper foil of the circuit pattern 12 was 35 μm electrolytic copper, and the insulating substrate 16 was glass epoxy resin FR-4.
The heat dissipation plate 19 and the heat pipe 17 are connected to each other by a flat heat pipe 1 as shown in FIG.
7 is placed on the surface of the heat dissipation plate 19 and bonded by using solder 20 or an adhesive having good thermal conductivity. These were laminated as shown in FIG. 1 and bonded by hot pressing to form the circuit board 11.

Using the circuit board 11 thus produced, the semiconductor element 31 having a heat generation amount of 2 W is mounted on the heat generating component mounting portion 12a as shown in FIG. 3, and the temperature is measured after 20 minutes have passed. The temperature was almost the same as that of the conventional embedded circuit board shown in FIG. The thickness of the circuit board of this example was 1.5 mm, which was 1/2 of the conventional thickness of 3 mm. In the figure, 17b is a heat radiating portion of the heat pipe, and the fins 23 enhance the heat radiating property.

The heat dissipation plate 19 and the heat pipe 1 described above.
As another example of the connection of No. 7, as shown in FIG. 4, by forming a recess 21 by half etching or the like on the surface of the heat dissipation plate 19 to which the heat pipe 17 is connected, the contact area between the heat dissipation plate and the heat pipe. And the positioning of the heat pipe becomes easy. Further, as another example, as shown in FIG. 5, if the uneven portion 22 is formed on the connection surface of the heat dissipation plate 19 with the heat pipe 17 by half etching or the like, the contact area can be increased in the same manner as described above.

The shape of the above heat pipe may be formed by bending the heat radiating plate 19 upward as shown in FIG. In this case, the circuit pattern 12 is provided in the space.
There is a design advantage that can be arranged.

The heat pipe may have a flat cross section, but as shown in FIG. 7, the heat absorbing section 17a of the heat pipe has a flat cross section and the heat radiating section 17b has a circular cross section. You can And the heat dissipation part 17b
A fin 24 for radiating heat or a water-cooling jacket (not shown) is attached to this to accelerate heat radiation.

[0015]

As described above, according to the present invention,
The thickness of the circuit board can be reduced without compromising the heat dissipation of the circuit board, the heating element can be easily mounted, and the heat pipe can be removed, making it easy to design, manufacture, and maintain. It has a great effect.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of a heat pipe type cooling device for a circuit board according to an embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a heat pipe mounting portion according to an embodiment of the present invention.

FIG. 3 is a perspective view schematically showing a heat pipe type cooling device for a circuit board according to an embodiment of the present invention.

FIG. 4 is an enlarged cross-sectional view of another example of the heat pipe attachment portion according to the embodiment of the present invention.

FIG. 5 is an enlarged cross-sectional view of still another example of the heat pipe attachment portion according to the embodiment of the present invention.

FIG. 6 is a side view showing the shape of the heat pipe according to the embodiment of the present invention.

FIG. 7 is a side view showing another example of the shape of the heat pipe according to the embodiment of the present invention.

FIG. 8 is a cross-sectional view of a conventional heat pipe embedded circuit board.

[Explanation of symbols]

 Reference Signs List 11 circuit board 12 circuit pattern 12a heat-generating component mounting portion 13 insulating sheet 14 adhesive layer 15 metal plate 16 insulating substrate 17 heat pipe 17a heat pipe heat absorbing portion 17b heat pipe heat radiating portion 18 substrate 19 heat radiating plate 20 solder 21 dent 22 uneven portion 23 Fin 31 Semiconductor element 32 Heat generating part 33 Adhesive material 34 Lead part

Claims (4)

[Claims] 1. A heat pipe type cooling device for a circuit board, wherein a flat portion of a heat pipe is connected to a heat radiating plate on the upper side of the board having a circuit pattern on its surface. 2. The heat pipe type cooling device for a circuit board according to claim 1, wherein a recess is formed in a heat pipe connection surface of the heat dissipation plate. 3. The heat pipe type cooling device for a circuit board according to claim 1, wherein the heat pipe connection surface of the heat dissipation plate is provided with irregularities or a rough surface. 4. The heat pipe type cooling device for a circuit board according to claim 1, wherein the heat pipe is formed by bending at least one location of the heat pipe above the circuit board.