JP2000049478A - Electronics - Google Patents

Abstract

(57) Abstract: Provided is an electronic device capable of reliably releasing heat of a circuit element, which tends to increase, without affecting the operation of the circuit element. A portable computer includes a housing that houses a second circuit board and a heat sink.
The second circuit board 21 has a microprocessor 23 mounted on a surface 21a and a cold plate 24 covering the microprocessor 23 attached thereto. The heat sink 22 has a heat receiving surface 33 facing the cold plate 24. The heat sink 22 has a heat transfer portion 35 protruding from the heat receiving surface 33. The heat transfer section 35 has a flat heat transfer surface 39 and a heat transfer surface 39.
And a restricting portion 42 provided on the peripheral edge portion. An elastic heat transfer member 40 is interposed between the heat transfer surface 39 and the cold plate 24. The restricting section restricts the amount of elastic deformation of the heat transfer member so that the stress acting on the microprocessor does not exceed a predetermined value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric device such as a portable computer or a mobile information terminal.

[0002]

2. Description of the Related Art Electronic devices such as book-type or notebook-type portable computers and mobile information terminals tend to be equipped with a microprocessor having a higher arithmetic processing speed. 2. Description of the Related Art In recent years, the mounting density of microprocessors has been improved in order to increase the operation processing speed and reduce the size. For this reason, the generated heat tends to increase as the arithmetic processing speed increases.

A conventional electronic device such as a portable computer has a heat sink attached to a cover member or the like attached to the microprocessor via a heat conductive member having thermal conductivity through a heat conductive silver paste or an adhesive. Is installed.

[0004] In the electronic device described above, heat generated by the microprocessor or the like is released to the outside through the heat sink. Further, in the electronic device, since the stress applied to the microprocessor by the silver paste or the adhesive described above does not exceed a predetermined value, the operation of the microprocessor is not affected.

[0005]

In an electronic device, the distance between the cover member and the heat sink is not constant and varies from one electronic device to another due to assembly tolerances. For this reason, the contact area with the heat sink, such as the above-mentioned heat conductive silver paste or adhesive, varies from one electronic device to another. Therefore, in the conventional electronic devices, it cannot be said that the heat generated by the microprocessor, which tends to increase as described above, can be reliably discharged in all the electronic devices.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an electronic device capable of reliably discharging the heat of a circuit element which tends to increase without affecting the operation of the circuit element.

[0007]

According to an aspect of the present invention, there is provided an electronic apparatus comprising: a circuit board; a circuit element which generates heat and is mounted on the circuit board;
A heat transfer portion to which heat is transmitted from the circuit element, a heat sink fixed to the circuit board and the heat transfer portion facing the circuit element, having elasticity, the circuit element and the heat sink A sheet-like heat transfer member provided between the heat sink and pressed when the circuit board and the heat sink are fixed to each other and elastically deformed, and transmitting heat generated by a circuit element to the heat sink; And a restricting portion for restricting an elastic deformation amount of the heat transfer member so that a stress acting on the circuit element does not exceed a predetermined value when the substrate and the substrate are fixed to each other.

According to this structure, the sheet-like heat transfer member provided between the circuit element and the heat sink is pressed and deformed when the circuit board and the heat sink are fixed to each other, and the regulating portion is transferred. Regulate the amount of elastic deformation of the heat member. Therefore, the variation in the contact area of the heat transfer member with the heat sink for each electronic device is suppressed. Therefore, the heat of the circuit element, which tends to increase, can be reliably released in all the electronic devices.

Further, the restricting portion restricts the amount of elastic deformation of the heat transfer member within a range in which the stress acting on the circuit element does not exceed a predetermined value. Therefore, even if the distance between the circuit board and the heat sink varies for each electronic device, the operation of the circuit element is not affected.

[0010] In carrying out the invention of claim 1,
It is preferable that a plurality of the regulating portions are provided as in the present invention. In this case, for each electronic device, the variation in the contact area of the heat transfer member with the heat sink is further suppressed, and the amount of elastic deformation of the heat transfer member is reduced by a range in which the stress applied to the circuit element does not exceed a predetermined value. Can be assured.

According to a second aspect of the present invention, the heat transfer section has a flat heat transfer surface facing the circuit element. It is desirable that the restricting portion is provided at a position that is point-symmetric with respect to the center of the heat transfer surface, or as in the present invention according to claim 4, wherein the heat transfer portion has a flat surface facing the circuit element. It is preferable that the heat transfer surface be provided, and the regulating portions be provided at equal intervals along a circumferential direction around the center of the heat transfer surface.

[0012] In these cases, too,
Variations in the contact area of the heat transfer member with the heat sink can be further suppressed, and the amount of elastic deformation of the heat transfer member can be ensured within a range in which the stress acting on the circuit element does not exceed a predetermined value.

In practicing the third or fourth aspect of the present invention, it is preferable that the restricting portion is provided at a peripheral portion of the heat transfer surface as in the fifth aspect of the present invention. In practicing the invention according to any one of claims 3 to 5, as in the invention according to claim 6, the regulating portion projects from the heat transfer surface toward the circuit board. Preferably, it is formed.

According to a sixth aspect of the present invention, it is preferable that the restricting portion has a flat surface along the heat transfer surface. In the implementation of the invention described in Item 7, as in the invention described in Item 8, it is preferable that the restricting portion is formed to have a C-shaped cross section along the heat transfer surface.

According to the configuration of the electronic device according to the fifth to eighth aspects, the variation of the contact area of the heat transfer member with the heat sink for each electronic device is more reliably suppressed, and the heat transfer member The elastic deformation amount of the member can be further ensured in a range where the stress acting on the circuit element does not exceed a predetermined value.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIG.
A description will be given with reference to FIG. FIG. 1 shows a book-type portable computer 1 as an electronic device. The computer 1 includes a computer main body 2 as a main body, and a display unit 3 as a flat display unit supported by the computer main body 2.

The computer body 2 includes a flat box-shaped housing 4, a CPU, a ROM,
It includes various functional components such as a circuit board on which a RAM or the like is mounted, a keyboard 5 mounted on the upper surface of the housing 4, and the like.

The housing 4 has a flat bottom wall (not shown).
And a lower housing 6 having a peripheral wall 6a connected to the bottom wall, an upper housing 7 having an upper wall 7a arranged substantially parallel to the bottom wall, and a peripheral wall 7b connected to the upper wall 7a. The various functional components described above are accommodated in the housings 6 and 7.

The housings 6, 7 are detachably connected to each other. As shown in FIG. 1, when the housings 6 and 7 are connected to each other, the peripheral walls 6a and 7b of the housings 6 and 7 are continuously connected to each other. Is configured.

The upper wall 7a of the upper housing 7
Has a flat armrest 8, and behind the armrest 8, the above-mentioned keyboard 5 as a means for inputting information is arranged. A pair of display supporting portions 13a and 13b are formed at the rear end of the upper wall 7a of the upper housing 7. These display support portions 13a and 13b are arranged apart from each other in the width direction of the housing 4 of the computer main body 2, and support the display unit 3.

The display unit 3 includes a housing 14 serving as a flat box-shaped housing, and a color liquid crystal display 15 (hereinafter, referred to as an LCD) housed in the housing 14. The LCD 15
Has a screen 15a for displaying information such as characters and figures. The housing 14 has, at one end thereof, a pair of hinge portions 18 opposed to the respective display support portions 13a and 13b along the width direction of the computer main body 2.
a, 18b.

The hinge portions 18a and 18b and the display support portions 13a and 13b are rotatably connected to each other by hinge shafts (not shown). The display unit 3 is rotatably supported by the computer main body 2 via these hinge shafts and the like. For this reason, the display unit 3 can be freely opened and closed between a closed position for covering the armrest 8 and the keyboard 5 and an open position for exposing the armrest 8 and the keyboard 5.

Also, in the housing 4 of the computer main body 2, a first circuit board (not shown), a second circuit board 21 shown in FIGS. 2, 4 and 5, and FIGS. And a heat sink 22 shown in FIG.

The first circuit board (not shown) is screwed to a boss (not shown) on the bottom wall of the housing 4 and arranged in parallel with the bottom wall. The first circuit board has a front surface and a back surface, and the back surface faces the bottom wall of the housing 4. D and D on the front and back surfaces of the first circuit board, respectively.
A plurality of extension connectors for connecting various circuit elements such as a RAM, a card connector, and various peripheral devices are arranged side by side.

The second circuit board 21 is arranged above the first circuit board and parallel to the first circuit board. The first circuit board and the second circuit board 21
They are separated from each other along the thickness direction of the housing 4 and are electrically connected to each other by a stacking connector (not shown).

The second circuit board 21 has a front surface 21a as a mounting surface and a back surface 21b. The back surface 21b of the second circuit board 21 faces the front surface of the first circuit board. Front surface 21a and back surface 2 of second circuit board 21
Various circuit elements such as an LSI package are mounted on 1b, respectively, and these circuit elements are connected to a wiring pattern on the second circuit board 21. In addition,
The second circuit board 21 forms the circuit board described in this specification, and the front surface 21a forms a first surface, and the back surface 21b forms a second surface.

As shown in FIGS. 4 and 5, on the surface 21a of the second circuit board 21, a microprocessor 23 having a quadrangular planar shape as a circuit element is mounted. The microprocessor 23 is electrically connected to the second circuit board 21 via the solder balls 19 arranged in a matrix on the surface 21a of the second circuit board 21. The microprocessor 23 has a ball grid array type (BGA: Ba) as a surface mount type semiconductor package.
ll Grid Array) It is a semiconductor package.

A cold plate 24 as a cover member for covering the microprocessor 23 from the front surface 21a side is attached to the front surface 21a. The cold plate 24 includes, as shown in FIGS. 2, 4 and 5, a plate body 25 facing the microprocessor 23, and an extending portion 26 extending from the plate body 25. ing. Cold plate 2
Reference numeral 4 is made of a metal having excellent thermal conductivity, such as an aluminum-based or copper-based alloy.

The plate body 25 is formed in a square shape larger than the microprocessor 23 and flat. The plate body 25 is connected to the second circuit board 21.
And an upper surface 25b exposed on the second circuit board 21. Boss portions 27 are protrudingly provided at two corners facing each other with the center of the upper surface 25b of the plate body 25 interposed therebetween.

Each boss 27 has a screw hole 28. One end of the screw hole 28 is open on the upper surface of the boss 27, and the other end of the screw hole 28 is open on the lower surface 25 a of the plate body 25.

Pins 30 (shown in FIG. 2) and the like are inserted into the peripheral portion of the plate body 25 and a position facing the peripheral portion of the second circuit board 21. The cold plate 24 is fixed to the second circuit board 21 by caulking the pins 30 to the plate body 25 and the second circuit board 21.

As shown in FIGS. 4 and 5, a heat transfer material 29 having thermal conductivity is provided between the lower surface 25a of the plate body 25 and the microprocessor 23. The heat transfer material 29 is provided on the surface 23a of the microprocessor 23.
And the lower surface 25 a of the plate body 25. As the heat transfer material 29, it is desirable to use a thermally conductive silver paste, an adhesive, or the like, or a rubber-like elastic body obtained by adding alumina to a silicon resin.

When the microprocessor 23 generates heat according to the above-described configuration, the heat of the microprocessor 23 is mainly transmitted through the heat transfer material 29 and the plate body 25 to the direction of the surface 21 a of the second circuit board 21. Is to be escaped.

The heat sink 22 is attached to the second circuit board 21 so as to cover the microprocessor 23 and the cold plate 24 from the front surface 21 side. The heat sink 22 is for releasing the heat of the microprocessor 23 transmitted to the cold plate 24,
It is made of a metal material having excellent thermal conductivity such as a magnesium alloy or an aluminum alloy.

As shown in FIGS. 2 and 3, the heat sink 22 includes a heat radiating panel 31, a module supporting portion 32,
Is provided integrally. The heat radiation panel 31 is formed slightly larger than the second circuit board 21. As shown in FIG. 4 and FIG.
A flat heat receiving surface 33 facing the upper surface 25b, etc., a flat heat radiating surface 34 exposed upward from the second circuit board 21, and a transfer formed so as to project from the heat receiving surface 33 toward the cold plate 24. A heating section 35.

When the heat sink 22 is attached to the second circuit board 21, the heat sink 22 has a screw hole 28 in the boss 27.
Are provided with communication holes 36 facing each other. Screws 37 are inserted into these communication holes 36, respectively. These screws 37 are screwed into the screw holes 28 from above the heat sink 22 through the communication holes 36, so that the heat sink 22 is attached to the second circuit board 21 via the cold plate 24. .

The heat radiating surface 34 is integrally provided with a large number of heat radiating projections 38 each having a columnar or frusto-conical shape and protruding. The heat radiation projections 38 are arranged in a matrix. Due to the presence of these heat radiation projections 38, a sufficient heat radiation area of the heat radiation surface 34 is ensured.

When the heat sink 22 is attached to the second circuit board 21, the heat transfer section 35
4 and located at a position opposite to the microprocessor 23. The heat transfer section 35 is provided with the cold plate 24.
And a heat transfer surface 39 which is substantially parallel to and flat.

When the heat sink 22 is attached to the second circuit board 21, the heat transfer surface 39
4 and the microprocessor 23. The heat transfer surface 39 is formed in a square shape having substantially the same size as the plate body 25 of the cold plate 24. A sheet-shaped heat transfer member 40 having thermal conductivity and elasticity is interposed between the heat transfer surface 39 and the cold plate 24.

The heat transfer portion 35 has boss receiving portions 41 formed at the four corners of the heat transfer surface 39 along the outer shape of the boss portion 27. Due to the presence of the boss receiving portion 41,
As described above, the heat sink 22 is connected to the cold plate 2.
When it is attached to the second circuit board 21 via 4, a restricting portion 42 described later comes into contact with the upper surface 25 b of the plate body 25.

The heat transfer member 40 is a rubber-like elastic body obtained by adding alumina to silicon resin, and is formed in a substantially square shape having substantially the same size as the plate body 25 and the heat transfer surface 39. When the heat sink 22 is attached to the second circuit board 21, the heat transfer member 40 is elastically deformed by being pressed by the upper surface 25 b of the plate body 25 and the heat transfer surface 39 when the heat sink 22 is attached to the second circuit board 21. 25b, 39. The heat transfer member 40 is located between the second circuit board 21 and the heat sink 22.

A regulating portion 42 is provided on the peripheral portion 39a of the heat transfer surface 39. A pair of regulating portions 42 are provided near the respective communication holes 36 and at positions facing each other with the geometric center P of the heat transfer surface 39 interposed therebetween.
The restricting portions 42 are provided at positions that are point-symmetric with respect to the center P, respectively, and are also provided at equal intervals along a circumferential direction around the center P.

The restricting portions 42 are formed so as to protrude from the heat transfer surface 39 toward the heat receiving surface 33, that is, toward the second circuit board 21. The restricting portions 42 are each provided with a heat transfer member so that the amount of protrusion from the heat transfer surface 39 does not exceed a predetermined value described later when the stress acting on the microprocessor 23 when the heat sink 22 is attached to the second circuit board 21. 40
Is a value that regulates the amount of elastic deformation. This predetermined value does not affect the operation of the microprocessor 23.

The regulating portion 42 has a tip end surface 43 formed on the heat transfer surface 3.
9 are formed flat. In addition, this tip surface 4
3 is a flat surface. The restricting portion 42 has a C-shaped cross section along the heat transfer surface 39 along the boss receiving portion 41 and surrounding the communication hole 36 from the circumferential direction.

When the screws 37 are screwed into the screw holes 28 and the heat sink 22 is mounted on the cold plate 24 by the above-described configuration, the restricting section 42 operates the microprocessor 23 via the cold plate 24 or the like.
The amount of elastic deformation of the heat transfer member 40 is regulated so that the stress transmitted to the heat transfer member does not exceed a predetermined value.

The module support 32 is connected to the side of the heat radiating panel 31. The module support part 32
It has a bottom 44 formed one step lower than the heat dissipation panel 31 and a plurality of bosses 45 extending upward from the bottom 44. The module support 32 is provided with the boss 45.
The first circuit board and the second circuit board 21
A separate circuit board (not shown) and a circuit module such as a modem are supported.

According to the present embodiment, when the second circuit board 21 and the heat sink 22 are fixed to each other, the sheet-like heat transfer member 40 is pressed and elastically deformed, and the regulating portion 42 is transferred to the heat transfer member 40. The amount of elastic deformation of the heat member 40 is regulated. For this reason, the variation in the contact area of the heat transfer member 40 with the cold plate 24 covering the heat sink 22 and the microprocessor 23 for each electronic device 1 is suppressed.

Since the heat transfer member 40 transfers the heat generated by the microprocessor 23 to the heat sink 22, the heat of the microprocessor 23, which tends to increase, can be reliably released in all the electronic devices 1. it can.

Further, a regulating portion 42 protruding toward the second circuit board 21 and formed on the peripheral portion 39 a of the heat transfer surface 39.
However, the elastic deformation of the heat transfer member 40 is restricted to a range in which the stress acting on the microprocessor 23 does not exceed a predetermined value. Therefore, the second circuit board 21 and the heat sink 2
2 can be prevented from affecting the operation of the microprocessor 23 even if the interval between the electronic devices 1 varies from one electronic device 1 to another, and the microprocessor 23 can be reliably prevented from being damaged.

Further, the restricting portion 42 is positioned at the center P of the heat transfer surface 39.
A pair is provided at positions opposed to each other with respect to the center P and at positions symmetrical with respect to the center P and at equal intervals in the circumferential direction about the center P. Therefore, the stress acting on the microprocessor 23 can be reliably prevented from exceeding a predetermined value.

Therefore, even if the distance between the second circuit board 21 and the heat sink 22 varies from one electronic device 1 to another, it is possible to more reliably prevent the operation of the microprocessor 23 from being affected.

In this embodiment, the regulating portion 42 is connected to the heat transfer surface 39.
Are provided at positions opposing each other with the center P interposed therebetween. In the present invention, the regulating portion 42 is located at at least one of a position symmetrical with respect to the center P and a position equidistant along the circumferential direction around the center P,
More than one pair may be provided.

If the regulating portion 42 is formed so as to protrude from the heat transfer surface 39 toward the second circuit board 21, it is needless to say that the planar shape thereof does not have to be C-shaped. Absent. Further, the regulating section 42 may be arranged at an interval from the heat transfer section 35.

[0054]

According to the present invention described in detail above, the sheet-like heat transfer member provided between the circuit element and the heat sink is pressed and deformed when the circuit board and the heat sink are fixed to each other. At the same time, the regulating section regulates the amount of elastic deformation of the heat transfer member.

Therefore, the variation in the contact area of the heat transfer member with the heat sink in each electronic device is suppressed. Therefore, the heat of the circuit element, which tends to increase,
In all electronic devices, it can be released reliably.

Further, the restricting section restricts the amount of elastic deformation of the heat transfer member so that the stress acting on the circuit element does not exceed a predetermined value. Therefore, even if the distance between the circuit board and the heat sink varies for each electronic device, the operation of the circuit element is not affected.

[Brief description of the drawings]

FIG. 1 is an exemplary perspective view showing a portable computer according to an embodiment of the present invention;

FIG. 2 is an exemplary exploded perspective view showing a main part of the portable computer according to the embodiment;

FIG. 3 is an exemplary perspective view of the heat sink of the portable computer according to the embodiment as viewed from a lower surface side;

FIG. 4 is an exemplary sectional view showing a part of a main part of the portable computer according to the embodiment before attaching a heat sink;

FIG. 5 is an exemplary sectional view showing a part of a main part after the heat sink is mounted in the portable computer of the embodiment;

[Description of sign]

 DESCRIPTION OF SYMBOLS 1 ... Portable computer (electronic device) 21 ... 2nd circuit board (circuit board) 22 ... Heat sink 23 ... Microprocessor (circuit element) 35 ... Heat transfer part 39 ... Heat transfer surface 39a ... Peripheral part 40 ... Heat transfer member 42 … Regulator 43… Front surface (flat surface)

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Atsushi Tatemichi 1-3-3 Shinmachi, Ome-shi, Tokyo Toshiba Computer Engineering Co., Ltd. F-term (reference) 5E322 AA01 AA11 AB02 FA04 FA05 FA06

Claims (8)

[Claims] 1. A circuit board, comprising: a circuit element that generates heat mounted on the circuit board; and a heat transfer section to which heat is transmitted from the circuit element, wherein the heat transfer section faces the circuit element. A heat sink fixed to the circuit board and fixed to the circuit board; an elastic member provided between the circuit element and the heat sink; the circuit board and the heat sink are elastically deformed by being pressed when the circuit board and the heat sink are fixed to each other; A sheet-like heat transfer member that transfers heat generated by the element to the heat sink; and a heat transfer member that, when the heat sink and the circuit board are fixed to each other, prevents a stress acting on the circuit element from exceeding a predetermined value. An electronic device, comprising: a regulating unit that regulates an elastic deformation amount of a member. 2. The electronic apparatus according to claim 1, wherein a plurality of said regulating portions are provided. 3. The heat transfer section has a flat heat transfer surface facing the circuit element, and the regulating section is provided at a point-symmetric position with respect to the center of the heat transfer surface. The electronic device according to claim 2, wherein 4. The heat transfer portion has a flat heat transfer surface facing the circuit element, and the regulating portions are provided at equal intervals along a circumferential direction around the center of the heat transfer surface. 3. The electronic device according to claim 2, wherein 5. The electronic device according to claim 3, wherein the restricting portion is provided on a peripheral portion of the heat transfer surface. 6. The electronic device according to claim 3, wherein said regulating portion is formed so as to protrude from said heat transfer surface toward said circuit board. 7. The electronic device according to claim 6, wherein the restricting portion has a flat surface along the heat transfer surface. 8. The electronic device according to claim 7, wherein the restricting portion has a C-shaped cross section along the heat transfer surface.