JP2001068607A - Cooling structure for electronic component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress warpage of a circuit board, to relax stress on soldered parts and to perform proper heat radiation even when a high heat conductor is interposed. SOLUTION: A circuit board 1 on which a semiconductor device 2 is mounted is fixed on bearing surfaces 5 formed on a heat radiating plate 3 by bolts 8, the distance 12 between a contact surface 3b formed on the heat radiating plate 3 and the substrate 1 is limited and a high heat conductor 4 whose thickness is limited is interposed in the gap. A concave part 3a for suppressing the loads imposed on the substrate 1 from the heat conductor 4 is provided on the contact surface 3b and an electronic component 7 is further disposed on the rear side of the circuit board 1 on the surface with which the heat conductor 4 is not in contact for suppressing the warpage of the substrate 1. Also, the state of the heat conductor 4 can be checked by a through hole 6 placed in the heat radiating plate 3 and the heat radiating plate 3 is connected to a housing to ensure a proper heat radiation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling structure for an electronic component which conducts heat of a semiconductor element or the like to a heat radiating portion to maintain the heat generating portion at a predetermined temperature.

[0002]

2. Description of the Related Art A conventional structure for cooling electronic components is as follows.
As described in Japanese Patent Application Laid-Open No. 08-204070, an electronic circuit board and a flat heat sink are brought into contact with a high thermal conductor over a wider area than a semiconductor element, and a heat generating portion of the semiconductor element and the heat sink are heated by heat conduction. An example of connecting and cooling is shown.

[0003]

As the size of electronic equipment is reduced, the space available for cooling is reduced, and the cooling performance is improved in a narrow space. It conducts heat to the heat radiating part through the high thermal conductor with the heat. When a flexible high thermal conductor is interposed in the conventional example, a load is applied to the circuit board to compress the high thermal conductor between the circuit board and the heat radiating section in order to secure contact with the heat radiating section, and the circuit board flexes, There was a problem that stress was applied to the upper soldered portion.

[0004] It is an object of the present invention to suppress bending of a circuit board, relieve stress on a soldered portion, and perform good heat radiation even when a high thermal conductor is interposed.

[0005]

In order to achieve the above object, a cooling structure for an electronic component according to the present invention is applied to a circuit board by forming a part of a heat radiating plate in contact with a high thermal conductor into a concave portion. The purpose is to suppress the load, reduce the deflection of the circuit board, and alleviate the stress at the soldered portion.

In addition, the distance between the circuit board or the semiconductor element and the heat sink and the thickness of the heat conductor are limited, or the distance between the circuit board or the semiconductor element and the heat sink or the thickness of the heat conductor is restricted. Thus, the load applied to the circuit board is suppressed, the bending of the circuit board is reduced, and the stress at the soldered portion is reduced.

Further, when electronic components are arranged on both sides of the circuit board, the electronic components are arranged so as to avoid the contact surface between the high thermal conductor and the circuit board. This is to prevent a large load from being applied to the circuit board, reduce the load applied to the circuit board, reduce the deflection of the circuit board, and alleviate the stress at the soldered portion.

Further, by attaching the heat radiating plate to the metal housing, good heat radiation is enabled, and by providing a through hole at a contact portion of the heat radiating plate with the heat conductor, it is possible to confirm the state of the high thermal conductor. Who has done it.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below. FIG. 1 shows a sectional view of an embodiment of the present invention. This figure shows that a seating surface 5 for fixing an electronic circuit board 1 on which a semiconductor element 2 is mounted on a surface thereof, and a contact surface 3b in which a distance 12 between the seating surface 5 is limited is formed on a heat sink 3;
By sandwiching the heat conductor 4 between the substrate 1 fixed to the seat surface 5 with the bolts 8 and the contact surface 3b, the substrate 1 and the heat sink 3
Are thermally coupled. The distance 12 between the seating surface 5 and the contact surface 3b so that the heat conductor 4 can surely contact the substrate 1 and the contact surface 3b.
, The heat conductor 4 is compressed, and as a result, a load is applied to the substrate 1 to compress the heat conductor 4. In order to reduce this load, a concave portion 3a is formed on the contact surface 3b.
Is formed, and the load force applied to the substrate 1 is reduced by reducing the compression area. The cooling structure of the electronic component can relieve the stress of the soldered portion due to the bending of the substrate 1. The electronic component 7 arranged on the surface of the substrate 1 different from the mounting surface of the semiconductor element 2 is arranged so as to avoid the contact surface between the substrate 1 and the heat conductor 4.
To reduce the load on the substrate 1 due to the compression. Also, by connecting the heat sink 3 to the metal housing 9,
Since the heat radiation to the surface increases, good heat radiation can be performed. Further, a through hole 6 is provided in the heat sink 3 so that the state of the heat conductor 4 can be checked.

According to the present embodiment, the flexible heat conductor 4
Is a liquid material such as rubber, gel, or heat conductive grease sealed in a flexible bag. Thickness T1 of thermal conductor 4, distance T2 between contact surface 3b and substrate 1, thermal conductor 4
, The area A of the heat conductor 4, the compressive force P per unit area, and the load C applied to the substrate 1, can be expressed as follows.

[0011]

## EQU1 ## Assuming that the area A of the heat conductor 4 is constant as described above, a load proportional to the amount of compression acts, and bending occurs. Here, when the compression amount ΔT is constant, the load C applied to the substrate 1 can be reduced by reducing the area of the contact surface 3b in the same manner as when the area A of the heat conductor 4 is reduced. In addition, the bending of the substrate 1 can be suppressed, and the stress at the soldered portion can be reduced.

FIG. 2 shows a second embodiment of the present invention. 1 has the same configuration as that of FIG.
The mounting portion is fixed through the electronic circuit board 1 by the through hole 11, and the heat conductor 4 is brought into contact with the mounting portion of the circuit board and the semiconductor element 2, and is thermally coupled to the heat radiating plate 3, thereby releasing heat. Will be The concave portion provided on the contact surface 3b has a shape in which the end of the contact surface 3b is dented instead of the vicinity of the center of the contact surface 3b, thereby reducing the contact area of the heat conductor 4 so that the substrate 1
, The bending of the substrate 1 is suppressed, and the stress at the soldered portion is relaxed. Further, a through-hole 6 is provided in the contact surface 3b so that the state of the heat conductor 4 can be checked. This figure shows that it is also suitable for cooling the semiconductor element 2 mounted on the substrate 1 through the through hole.

FIG. 3 shows a third embodiment of the present invention. The semiconductor element 2 and the electronic component 10 are formed through holes 11
The electronic circuit board 1 is mounted on the seat surface 5 with bolts 8, and the high thermal conductor 4 is sandwiched between the contact surface 3 b formed on the heat sink 3 and the circuit board 1. In order to reduce the load applied to the substrate 1, a part of the contact surface 3b is formed as a recess. Further, a through hole 6 is provided in the contact surface 3b so that the state of the heat conductor 4 can be checked. This is almost the same as FIG. 2 and shows that the semiconductor device 2 and the electronic component 10 fixed through the through holes are also suitable for cooling. FIG. 4 shows a fourth embodiment of the present invention. A metal housing or the like facing the semiconductor element 2 mounted on the electronic circuit board 1 is used as a heat sink 3 and the semiconductor element 2
A flexible high thermal conductor 4 is interposed between the heat radiation plate 3 and the heat radiation plate 3 to thermally couple them. In this figure, as in FIG.
By compressing a part of the contact surface 3b between the heat radiating plate 3 and the heat conductor 4 into a concave portion 3a,
, The bending of the substrate 1 is suppressed, and the stress on the soldered portion can be reduced. In addition, by providing the through hole 6 in the concave portion 3a of the heat sink 3, the state of the heat conductor 4 can be checked. This figure shows that the present invention can be applied to cooling of a semiconductor element or the like performed through a flexible heat conductor on the side of a heating element such as a semiconductor.

[0014]

According to the present invention, when heat is radiated by sandwiching a high thermal conductor between the electronic circuit board and the heat radiating plate, bending of the substrate is suppressed, and heat is efficiently conducted from the heat generating portion to the heat radiating portion.

[Brief description of the drawings]

FIG. 1 is a sectional view of one embodiment according to the present invention.

FIG. 2 is a sectional view of a second embodiment according to the present invention.

FIG. 3 is a sectional view of a third embodiment according to the present invention.

FIG. 4 is a sectional view of a fourth embodiment according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electronic circuit board, 2 ... Semiconductor element, 3 ... Heat sink, 3a
... recess, 3b ... contact 4 ... high thermal conductor, 5 ... seat surface, 6 ... through-hole, 7 ... electronic parts, 8 ... bolt, 9 ... metal housing, 10
... electronic parts, 11 ... through holes, 12 ... distance.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Koichi Yawata 2520 Oaza Takaba, Hitachinaka City, Ibaraki Prefecture F-term in the Automotive Equipment Group, Hitachi, Ltd. 5F036 AA01 BB01 BB08 BB21 BC03

Claims (7)

[Claims] An electronic circuit board on which a semiconductor element is mounted, wherein a heat dissipating member facing a surface of the electronic circuit board different from a surface on which a specific semiconductor element is mounted, and a surface on which the semiconductor element is mounted. In a cooling structure for an electronic component having a flexible high heat conductor between different surfaces and the heat radiation member, a part of a contact surface of the heat radiation member that contacts the high heat conductor is concave. Parts cooling structure. 2. An electronic circuit board on which a semiconductor element is mounted, comprising a heat radiating member facing a specific semiconductor element on the electronic circuit board, and a flexible high thermal conductor between the semiconductor element and the heat radiating member. A cooling structure for an electronic component, wherein a part of a contact surface of the high thermal conductor that contacts the high thermal conductor is recessed. 3. The electronic circuit board according to claim 1, wherein a distance between a mounting seat surface of the electronic circuit board and a surface of the heat radiating member on which the high thermal conductor is in contact and a thickness of the high thermal conductive element are limited. Cooling of the electronic component, wherein the contact of the high heat conductor is ensured by limiting either the distance between the mounting seat surface of the heat conductor and the surface contacting the heat conductor or the thickness of the high heat conduction element. Construction. 4. The semiconductor device according to claim 2, wherein a distance between a surface of the semiconductor element and a surface of the heat radiating member where the high thermal conductor contacts and a thickness of the high heat conductive element are limited. A cooling structure for an electronic component, wherein the contact of the high thermal conductor is ensured by limiting either the interval between the surfaces contacting the high thermal conductor or the thickness of the high thermal conductive element. 5. The electronic component according to claim 1, wherein an electronic component arranged on a surface of the electronic circuit board different from the surface on which the semiconductor element is mounted is arranged avoiding a portion where the high thermal conductor contacts. Cooling structure for electronic components. 6. The electronic component according to claim 1, wherein the heat radiating plate is connected to a metal housing and radiates heat to the metal housing through the heat radiating plate. Cooling structure. 7. The cooling structure for an electronic component according to claim 1, wherein a through hole is provided in said high heat conductor contact portion of said heat sink.