JP2000311050A - Keyboard device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lightweight/thin type key board which has a large heat radiating effect by closely sticking flexible graphite sheet to almost all over a shield plate bottom surface. SOLUTION: This device is equipped with a key top 1, a key board frame 2, circuit patterns 3a and 3b, a shield plate 4, a elasticity body 5a consisting of a rubber material having a projection 5b, a flexible graphite sheet 6, a CPU 7 which is heat radiating parts, and a wiring substrate 8. An aluminum alloy plate is used as this shield plate 4, and one flexible graphite sheet 6 is stuck to the bottom surface for improving a heat radiating effect. A heat radiating surface of a heat radiating body 7 provided on the wiring substrate 8 and the graphite sheet 6 are in direct contact with each other. Heat of the heat radiating body 7 is directly transmitted to the graphite sheet 6 in a horizontal direction, and is transmitted to the shield plate 4. The heat of the shield plate 4 is transmitted vertically and horizontally inside itself.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to measures for heat radiation of electronic devices such as notebook personal computers and portable information terminals which are required to be small and light.

[0002]

2. Description of the Related Art FIG. 3 is a sectional view of a conventional keyboard device used in a portable electronic device such as a notebook personal computer. In the figure, 50 is a key top, 51 is a keyboard frame, 52a and 52b are circuit patterns, 53 is a shield plate made of a metal plate, and 54a is an elastic body made of a rubber material having a projection 54b.

When the key top 50 is pressed with a finger, the elastic body 54 is pressed.
a is deformed, the protrusion 54b pushes the circuit pattern 52a,
The circuit pattern 52a contacts the circuit pattern 52b,
A signal corresponding to key top 50 is input. When the finger is released, the key top 50 returns to a predetermined position by the elastic body 54a.

[0004] The shield plate 53 is a metal plate made of aluminum having a thickness of, for example, about 0.8 mm, and its original purpose is to absorb unnecessary radiated radio waves radiated by electronic components incorporated under the keyboard device. From the viewpoint of heat dissipation measures, there is a case where a configuration is used in which the heat dissipation plate is used (JP-A-6-51868, JP-A-9-8189, etc.). In this case, the heat-generating electronic component 55 and the shield plate 5
3 is connected, for example, via a heat conductive grease 56 as a heat conductive member, and conducts the heat generated from the heat-generating electronic component 55 to the aluminum plate via the heat conductive grease 56, so that the keyboard frame 51, the key top Heat was radiated outside from the keyboard device surface such as 50.

However, recent portable information terminals have been remarkably light and thin, and the thickness of the shield plate 53 has to be reduced, for example, from the conventionally used aluminum plate of t = 0.8 mm in order to make the keyboard device thin. t = 0.4m
The thickness is reduced by changing to an aluminum plate of m. For this reason, the heat conduction capability of the shield plate 53 as a heat sink is reduced.

The original purpose of the shield plate 53 is to serve as a shield effect and as a means for holding the keyboard device. From this viewpoint, there is no problem even if the aluminum plate is changed to t = 0.4 mm. However, from the viewpoint of heat dissipation measures, reducing the thickness of the aluminum plate increases the heat resistance of the heat dissipation plate and reduces the heat capacity. In particular, if a rigid stainless steel is used instead of the aluminum plate for further thinning, t = 0.15 mm from the strength of the keyboard device.
Stainless steel rope. However, in this case, the heat radiation effect is further deteriorated. That is, since the thermal conductivity of stainless steel is about 1/10 that of an aluminum plate, the effect as a heat sink is significantly reduced, and the effect as a heat sink can no longer be expected.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a lightweight and thin keyboard device having a large heat radiation effect.

[0008]

SUMMARY OF THE INVENTION A flexible graphite sheet produced by a specific method has a thermal conductivity of about four times that of pure aluminum and a specific gravity of about one third of aluminum. It has been proposed to use a flexible graphite sheet as a heat conducting member by utilizing this high thermal conductivity property, but there was a drawback that the physical strength was brittle, and it was difficult to practically use as a heat conducting member due to easy tearing. .

A keyboard device according to the present invention is a device in which a flexible graphite sheet is attached to substantially the entire surface of a shield plate to improve the thermal conductivity of the shield plate, and is lightweight, thin and excellent in heat dissipation. Can be provided.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention provides a key top, a keyboard frame for positioning the key top, a circuit pattern for key input, a shield plate, and a flexible board. And a graphite sheet, wherein the flexible graphite sheet is in close contact with substantially the entire bottom surface of the shield plate, and the thickness of the shield plate is increased by the good thermal conductivity of the flexible graphite sheet. Even when the thickness is reduced, the shield plate can be used as a heat sink, and a thin and lightweight keyboard device can be provided. Further, since the flexible graphite sheet is used in close contact with the shield plate, even if the flexible graphite sheet has a small physical strength, it can be put to practical use.

According to a second aspect of the present invention, in the first aspect of the present invention, a tape having an adhesive layer or an adhesive layer on one surface is attached to the surface of a flexible graphite sheet, The invention is characterized in that the tape, which protrudes beyond the four sides of the graphite sheet, is adhered to a shield plate. Since the surface is protected by the tape material, even a material having a small physical strength can be used.

According to a third aspect of the present invention, in the second aspect of the present invention, a tape is attached to only four sides of a flexible graphite sheet. By connecting the surface of the flexible graphite sheet where no is adhered and the heat generating member directly or via a heat conductor such as heat conductive grease, the heat of the heat generating portion is efficiently transmitted to the graphite sheet. be able to.

According to a fourth aspect of the present invention, in the second aspect, the support of the tape is made of an aluminum foil or a copper foil, and covers the graphite sheet. Since the tape support is a good heat conductive material, the graphite sheet and the heating element can be in contact with each other via the tape foil, and a flexible graphite sheet with small physical strength is placed between the shield plate and the tape. Can be completely sealed.

(Embodiment 1) FIGS. 1 and 2 are a cross-sectional view and a perspective view seen from the back of a keyboard device according to an embodiment of the present invention, respectively.

In FIG. 1, 1 is a key top, 2 is a keyboard frame, 3a and 3b are circuit patterns, 4 is a shield plate, 5a is an elastic body made of a rubber material having a projection 5b, 6
Is a flexible graphite sheet, 7 is a heating component CP
U and 8 are wiring boards.

When the key top 1 is pressed with a finger, the elastic body 5a is deformed, the projection 5b presses the circuit pattern 3a, and the circuit pattern 3a and the circuit pattern 3b come into contact with each other.
Is input. When the finger is released, the elastic body 5a
The key top 1 returns to a predetermined position due to the elasticity of the key top 1.

Although the keyboard frame 2 is made of plastic having a thickness of about 1 mm, a hole for inserting the key top 1 is formed on the front surface, and thus the keyboard frame 2 is not rigid enough to keep the entire keyboard device flat. The shield device 4 mainly supports the keyboard device of FIG. Conventional shield plates are t = 0.8 mm aluminum alloy plates (for example, A
(an alloy containing 2.5% Mg in 1).
On the other hand, in the present embodiment, t =
A 0.4 mm aluminum alloy plate is used, and one flexible graphite sheet is adhered to the bottom surface of the aluminum alloy plate to improve heat radiation characteristics.

FIG. 2 is a projection view showing how the shield plate 4 and the flexible graphite sheet 6 are brought into close contact with each other. In the figure, the plane portion of the shield plate 4 is, for example, 110 × 24
It has a flat part with a dimension of 0 mm. The flexible graphite sheet 6 has a rectangular shape of, for example, 80 × 220 mm and t = 0.1 mm, and its periphery is stopped by the tape 10 and is in close contact with the shield plate 4. The tape 10 is not attached to the central part of the graphite sheet 6, and the graphite surface is exposed.

Next, referring to FIG. 1, a heating element 7 (for example, CP
A method of transmitting the heat of U) to the shield plate 4 will be described. The heating element 7 is provided on the wiring board 8, and the heating surface of the heating element 7 is in direct contact with the graphite sheet 6. The central portion where the graphite sheet 6 is exposed is selected as the contact surface with the heating element 7. The heat of the heating element 7 is directly transmitted to the graphite sheet 6, and the heat is transmitted in the graphite sheet 6 in the lateral direction and also to the shield plate 4. The heat of the shield plate 4 is transmitted horizontally and vertically inside the shield plate 4.

At this time, the manner of heat transmission was examined by measuring the surface temperature (Tables 1 and 2).

[0021]

[Table 1]

In Table 1, when a thin aluminum plate keyboard using an aluminum plate having a thickness of 0.4 mm as a shield plate is used, the keyboard of this embodiment is the same as the thin aluminum plate keyboard. When one graphite sheet (t = 0.1 mm) is adhered, the equilibrium temperature of each part is shown when a 0.8 mm thick aluminum plate keyboard is used as a conventional standard keyboard. Furthermore, when the shield plate is t = 0.
In the case of 15 mm stainless steel, the temperature distribution is shown when a flexible graphite sheet of t = 0.1 mm is stuck on the bottom surface of the shield plate.

In FIG. 1, the heating element 7 is provided on the right side of the shield plate 4. Therefore, the temperature of the shield plate is higher on the right side than on the left side. In Table 1, for example, the temperature of the upper surface of the keyboard means the temperature of the key top surface portion of the leftmost B or rightmost A key shown in FIG. 1 when the personal computer is continuously operated at full power at room temperature (35 ° C.). It shows the equilibrium temperature. Similarly, the keyboard back surface temperature indicates the equilibrium temperature of the shield plate 4 immediately below the A key or the B key in FIG. Also, CPU
The temperature is an equilibrium temperature inside the CPU output by the CPU itself.

In this case, since the heat transfer in the horizontal direction is poor, the temperature difference between the left and right of the keyboard is large, and
The temperature reached 8.5 ° C, 55.5 ° C on the right side of the keyboard. In contrast, and because of the graphite sheet and the thick aluminum plate, the heat transfer in the lateral direction is improved and the temperature difference between the left and right of the keyboard is considerably reduced. As a result, the temperature of the high-temperature portion is lower than that of 65.5 ° C. and 66 ° C. on the right side of the keyboard rear surface and 54 ° C. on the right side of the keyboard upper surface. Further, since the heat of the CPU has easily escaped to the left side of the keyboard, the temperature of the CPU has also dropped.

As described above, the heat radiation effect is improved and the temperature of the high-temperature portion is reduced. The degree of the heat radiation effect is almost the same.
Therefore, when a single graphite sheet (0.1 mm thick) is attached to the shield plate, the standard keyboard is 0.8 mm thick aluminum plate (0.8 × 1 mm).
(In the case of 10 × 240), the thickness can be reduced by about 0.3 mm, and the weight can be reduced to about half (about 27 g).

The lower the equilibrium temperature in Table 1 is, the more preferable. However, the maximum temperature of the key top surface A is 85 ° C. or less when the room temperature is 35 ° C. and the maximum temperature of the shield plate B is lower than the safety standard. Manufacturer's guaranteed temperature 70 ° C
Hereinafter, the maximum temperature of the CPU is 100 ° C. which is the manufacturer's guaranteed temperature. With respect to the above upper limit, all of the above are below the standard temperature. In this case, however, it is needless to say that the equilibrium temperature of the CPU is as high as 90 ° C., which is preferable.

When a stainless steel (austenite steel) with t = 0.15 was used as the shield plate 4 instead of the aluminum plate with t = 0.4 mm, the graphite sheet 6 was adhered in the same manner as above. Things. The keyboard device has the same rigidity as the keyboard device, but the heat dissipation effect is remarkably inferior due to the poor thermal conductivity of the stainless steel, and the temperature on the back of the keyboard is 75%.
° C, exceeding the manufacturer's guaranteed temperature. When one graphite sheet 6 is stuck, the heat radiation effect is improved and t
It is the same level as using an aluminum plate of = 0.4 mm. Weight of the shield plate is the same as
The thickness can be reduced by 0.15 mm.

The graphite sheet preferably used in the present embodiment is obtained by heat-treating a film of a specific polymer compound at a temperature of 2,400 ° C. or more in an inert gas to obtain a graphite structure. A foamed state is created by the treatment, and the foamed state is rolled to obtain a graphite sheet having flexibility and elasticity (JP-A-3-75211, JP-A-8-23183, JP-A-8-267647). Gazette, JP-A-9-156
913). Among the graphite sheets obtained by this production method, the specific gravity is 0.5-2.
25. Those having a thermal conductivity of 600 to 1,004 W / mk are suitable for the graphite sheet 6 according to the present invention. Note that the range of the specific gravity is large due to the difference in the manufacturing method, and a sheet material having high flexibility has a small specific gravity (0.
5 to 1.5), the sheet material having poor flexibility has a large specific gravity (1.5 to 2.3).

The graphite sheet 6 used in the first embodiment is a graphite sheet manufactured by the above method, and has a thickness of 100 μm and a thermal conductivity of 800 to 860 kc.
al / m · h · ° C., specific gravity is 0.8 to 1.0, and is a flexible sheet.

The support of the tape to be used is preferably a heat-resistant one such as a polyimide film, an aluminum foil or a copper foil. When a metal tape having good heat conductivity such as an aluminum foil or a copper foil is used, even if a heat-generating component is brought into contact with the metal tape, the thermal resistance does not increase.

It is needless to say that the heat radiation effect can be further improved if a plurality of flexible graphite sheets are laminated and used in the embodiment.

Further, the keyboard device of the first embodiment has a heat radiation effect similar to that of the conventional aluminum plate of t = 0.8 mm, and the flexible graphite sheet 6 is placed on the back of the shield plate 4 serving as a reverberation plate. Since it is attached, it also has the effect of reducing the tapping sound due to key operation.

[0033]

According to the present invention, by attaching a graphite sheet having a high thermal conductivity and a low specific gravity to a shield plate of a keyboard device, the same heat radiation effect as when the shield plate is made of aluminum or copper alone is obtained. In addition, a thin and lightweight keyboard device can be provided. In addition, the physical strength of the flexible graphite sheet can be complemented by protecting the surface of the flexible graphite sheet having a small physical strength with a tape material and attaching the sheet to a shield plate.

[Brief description of the drawings]

FIG. 1 is a sectional view of a heat radiation mechanism of a keyboard according to an embodiment of the present invention.

FIG. 2 is a perspective view of the keyboard according to the embodiment of the present invention as viewed from the back.

FIG. 3 is a cross-sectional view of a heat radiation mechanism in a conventional keyboard.

[Description of Signs] 1 Key Top 2 Keyboard Frame 3a, 3b Circuit Pattern 4 Shield Plate 6 Flexible Graphite Sheet

Claims (5)

[Claims] 1. A key top, a keyboard frame for positioning the key top, a circuit pattern for key input, a shield plate, and a flexible graphite sheet are provided on substantially the entire bottom surface of the shield plate. A keyboard device, wherein the flexible graphite sheet is in close contact. 2. A method in which a tape having an adhesive layer or an adhesive layer on one side is attached to the surface of a flexible graphite sheet, and the tape which protrudes from four sides of the flexible graphite sheet is attached to a shield plate. Characteristic keyboard device. 3. The keyboard device according to claim 2, wherein a tape is attached to only four sides of the flexible graphite sheet. 4. The keyboard device according to claim 2, wherein the support of the tape is made of aluminum foil or copper foil. 5. The keyboard device according to claim 2, wherein the shield plate is made of aluminum or stainless steel having a thickness of less than 0.4 mm.