JPH06140774A - Heat dissipation structure of plastic cover - Google Patents

Abstract

PURPOSE:To improve heat dissipation property even if a plastic material of poor heat transmitting property is used. CONSTITUTION:Metallized metallic layers 2, 3 are provided to a specified partial surface or an entire surface of an inside surface and an outside surface of a plastic cover 1. The metallic layers 2, 3 are made conductive and connected by a plurality of through-holes 4. The metallic layers are provided to inside and outside surfaces of the plastic cover. A metallic conductor layer is provided to an intermediate layer inside the plastic cover. The metallic layers in both inside and outside surfaces are made conductive and connected through the metallic conductor layer and a via hole connected thereto.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic cover forming the outer shape of a cabinet that houses electronic circuits.

Due to the remarkable development of semiconductor parts, miniaturization, high performance, and low price have been realized, and electronic devices composed of electronic circuits using the same have come to be used in various fields. On the other hand, the development of plastics, especially engineering plastics, has been remarkable, and the design of the case of the housing that houses the electronic circuit is important in a single-use device. Good characteristics, productivity, low cost, etc. The current situation is that metal is being replaced by plastic molding.

[0003]

2. Description of the Related Art FIG. 3 shows a conventional electronic device housing. As a conventional example, as shown in FIG. 3, a case 99 of a mobile phone will be described.
It is required to be robust and lightweight, have good handling operability, good productivity, and low cost.

Therefore, the casing 99 has a streamlined outer shape,
The handling and operation parts are protected from erroneous operations (for example, the key top is lowered from the housing surface so that it cannot be pressed by mistake, and a funnel-shaped guard part is provided on the housing side, etc.), and irregularities are provided everywhere on the surface. In addition, character symbols are also integrally written on the surface, and ventilation holes (for transmitting sound from a speaker or a microphone, or for cooling ventilation) are provided.

The housing 99 is made of plastic,
A plastic cover 19 forming a front surface and a side surface and a plastic base 98 forming a rear surface and mounting an electronic circuit are divided and configured.

When shielding is required due to electrical characteristics, a predetermined portion of the inner surface of the plastic cover 19 and the plastic substrate 98 is metallized to provide a metal layer for shielding.

[0007]

However, in such a portable device, cooling ventilation with the inside can hardly be expected from the viewpoint of dustproofness. Further, since the heat conductivity of a general plastic material is extremely lower than that of a metal, the heat generated by the electronic circuit is trapped inside the housing 99, and the heat dissipation to the outside by the housing 99 is low. There were problems such as.

In view of the above problems, it is an object of the present invention to provide a heat dissipation structure for a plastic cover that improves the heat dissipation even with a plastic material having poor heat conductivity.

[0009]

As shown in FIGS. 1 and 2, the above-mentioned object is [1] a plastic cover forming an outer shape of a cabinet for housing an electronic circuit, wherein the plastic cover 1 has an inner surface and an outer surface. By the heat dissipation structure of the plastic cover of the first invention, which has metal layers 2 and 3 which are metallized on a predetermined part of the side surface or the entire surface and which is electrically connected by a plurality of through holes 4 between the metal layers 2 and 3. To be achieved. [2] In addition, the metal layer 2, on the inner and outer surfaces of the plastic cover 11,
3 and the metal conductor layer 5 is provided in the intermediate layer inside the plastic cover 11, and the metal layers 2 and 3 on the inner and outer surfaces are electrically connected through the metal conductor layer 5 and the Via hole 6 connected to the metal conductor layer 5. The heat dissipation structure of the plastic cover of the second invention is also applicable.

[0010]

In other words, the heat generated inside is absorbed by the metal layer 2 on the inner side surface, and the metal layer 2 is conductively connected to the metal layer 3 exposed on the outer side surface. The heat is radiated as it is exposed to the outside air and radiated as radiant heat.

The conduction between the metal layers 2 and 3 is carried out through the through hole 4 or the metal conductor layer 5 and the Via hole 6, and the heat conduction when connecting through the through hole 4 is as follows. .

Q = λ · ΔT / L ・ ・ ・ Q: Amount of heat passing through a unit area in an object (plastic cover) in a unit time λ; Thermal conductivity of object (plastic cover) L; Distance of heat transmission (plastic cover) Thickness) ΔT; temperature difference before and after the heat transfer distance L (for example, when the inner surface of the cover is T1 degrees and the outer surface is T2 degrees, | T1 −T2 |) where the thermal conductivity of the metal layer is λ ′, When the thermal conductivity is λ ″ and the cross-sectional area of the through-hole conductor in the unit area of the plastic cover 1 is 1 / K, the average thermal conductivity λ is λ = (1-1 / K) λ ″ + λ ′ / K ……, and if the metal layers 2 and 3 and the through holes 4 are made of copper material, λ ′ ≈ 300 W / m ° C, plastic material λ ″ ≈ 0.3 W / m
° C, and λ'≈1000λ ".

∴λ≈ (1-1 / K) λ ″ + 1000λ ″ / K = (K + 999) λ ″ / K) ... Here, if K = 1000, then λ≈2λ ″ K = 100 If λ≈11λ ″ K = 10, then λ≈101 λ ″.

That is, if the cross-sectional area of the through hole 4 is set to 1/1000 of the surface area and the metal layers 2 and 3 on the inner and outer surfaces are connected to each other, the heat transfer characteristic is twice as high as that of a plastic cover without a metal layer. Further, if the through hole 4 is provided in 1/100, it becomes 11 times, and if it is 1/10, it becomes 101 times, and the heat dissipation characteristics can be easily improved.

In the case where the intermediate metal conductor layer 5 and the via hole 6 are also electrically connected, the via hole 6 is connected to the through hole 4.
And the metal conductor layer 5 in the middle lowers the thermal resistance and reduces heat dissipation.

Thus, according to the present invention, it is possible to provide a heat dissipating structure for a plastic cover that improves the heat dissipating property even with a plastic material having a poor heat transfer property.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the embodiments shown in the drawings. Throughout the drawings, the same reference numerals denote the same objects. FIG. 1 shows an embodiment of the first invention, (a) is a plastic cover, (b) is an enlarged view of the AA cross section, and FIG. 2 is a partially enlarged view of the plastic cover of the second invention.

Each of the present embodiments is applied to the same portable mobile electronic device. One embodiment of the first invention is shown in FIG.
As shown in (a), vertical 20 × for the housing that houses the electronic circuit
It is a plastic cover 1 made of ABS resin with a width of 40 cm and a depth of 10 cm. The surface has an uneven shape due to the mounting holes 12 of the operating parts, finger hooks 13 and the like, and is further divided into two parts from the center to the left and right. ing.

The heat radiating mechanism for heat generation of the electronic circuit is the metal layer 3 provided on the outside in the shaded area shown in the figure, and the inside is also shown in FIG.
, The metal layer 2 is provided on almost the entire surface, and 5
Through holes 4 of 1 mmφ are bored in the mm grid, and the metal portion is formed by electroless plating of a copper base and electrolytic plating of nickel to form a conductive connection.

As a result, the cross-sectional area ratio of the through hole 4 to the unit area of the plastic cover 1 is 1 / K≈1 /
32, thus the average thermal conductivity from the above equation λ≈32λ ″
As compared to the case where a metal layer was provided only inside for electromagnetic shielding, 32 times more heat conduction was obtained, and it was possible to sufficiently clear the usage conditions that were not met in the past.

Further, an embodiment of the second invention is as shown in an enlarged cross section in FIG. 2, in which a metal layer 2 on the inner side surface, a metal layer 3 on the outer side surface, and an inner layer are further formed by a method of producing a printed wiring board. Is also a plastic cover 11 provided with a metal conductor layer 5, and a via hole 4 is provided in the metal conductor layer 5 and is connected to each of the metal layers 2 and 3 while being displaced.

Therefore, unlike the above-mentioned through hole 4, it is not necessary to fill the through hole, and the via hole 4 is short-circuited once in the metal conductor layer 5, and the through hole 4 is sufficiently transmitted by that amount. Since the thermal resistance is lowered, the thermal conductivity is further increased, and the same effect can be obtained even with the small diameter as the Via hole 4 of 0.6 mmφ, and the surface can be made less conspicuous.

The above embodiment is an example, and the shape, size, and material of each part are not limited to the above. The metal layers 2 and 3 provided on the inner and outer surfaces are provided on almost the entire surface, but may be provided only partially on a required predetermined surface, or
It does not matter even if it is provided in a grid pattern in which the strips are crossed.

The through hole 4 may be a tapered through hole.

[0025]

As described above, according to the heat dissipation structure of the plastic cover of the present invention, the heat dissipation can be improved even with a plastic material having poor heat conductivity, and a sufficient cooling cover can be realized. is there.

[Brief description of drawings]

FIG. 1 is an embodiment of the first invention (a) a plastic cover (b) an enlarged sectional view taken along line AA of FIG.

FIG. 2 is an enlarged view of a partial cross section of a plastic cover of the second invention.

FIG. 3 is an example of a conventional electronic device housing

[Explanation of symbols]

1,11,19 Plastic cover 2,3 Metal layer
4 Through hole 5 Metal conductor layer 6 Via hole
12 Mounting hole 13 Finger hook 98 Plastic base
99 housing

Claims (2)

[Claims] 1. A plastic cover forming an outer shape of a cabinet for accommodating an electronic circuit, the metal layer (2, 3) being metallized on a predetermined part or the whole of an inner side surface and an outer side surface of the plastic cover (1). ), And the heat dissipation structure of the plastic cover is characterized in that the metal layers (2, 3) are electrically connected by a plurality of through holes (4). 2. A plastic cover (11) having the metal layers (2, 3) according to claim 1 on the inner and outer surfaces thereof, and the plastic cover (11).
A metal conductor layer (5) is provided in the intermediate layer inside (11), and via the metal conductor layer (5) and the via hole (6) connected thereto,
A heat dissipation structure for a plastic cover, characterized in that the metal layers (2, 3) on the inner and outer surfaces are electrically connected.