JPH1024687A - Card type electronic equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently transmit the heat generated from an IC chip outside an IC card for radiation of heat in the IC card. SOLUTION: In an IC card covered by a metal case, an IC chip 11 as a heating element is arranged opposite to the metal case under a mounting method, in which the active surface is exposed. The active surface of the IC chip has a structure directly contacting with the metal case buy the elastic force of a sparingly spacer 15 locating beneath a printed-wiring board 13, on which the IC chip is mounted so as to realizing an electrically and thermally conducting constitution. Thus, since heat is transmitted directly from the IC chip as the heating element to the metal case, the efficient transmission of the heat outside the IC card becomes possible. Further, due to the structure, in which a module in the IC card and the metal case come into close contact with each other, the module can be prevented from being rickety, resulting in realizing high reliability.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a card-type electronic device, and more particularly to heat radiation of a card-type electronic device having a structure in which a semiconductor integrated circuit (hereinafter, referred to as "IC chip") is mounted and covered with a metal case. It is related to the structure.

[0002]

2. Description of the Related Art When an IC chip operates, power is consumed, heat is generated, and the temperature of the IC chip itself rises. When the temperature rise exceeds the operating limit temperature of the IC chip,
This will hinder the operation of the IC chip. Further, as a result, the card-type electronic device on which the IC chip is mounted cannot function normally. Therefore, by efficiently transmitting the heat generated from the IC chip to the outside and suppressing an increase in the temperature of the IC chip itself, the reliability of the card-type electronic device itself is improved. From this point of view, it is important to provide a structure in which the heat dissipation effect of the IC chip itself can be obtained in a state where the IC chip is assembled into a card-type electronic device.

[0003]

The applicant has proposed a structure as shown in FIG. 2 in Japanese Patent Application No. 7-139538 for a heat radiation structure of a card-type electronic device. In FIG.
Reference numeral 21 denotes an IC chip serving as a heating element, and reference numeral 22 denotes a sealing material (mold) for sealing the IC chip 21 serving as a bare chip. 23 is a printed wiring board on which an IC chip is mounted. 24 is a metal case, 25 is a filler having good thermal conductivity, 26 is a thermal via, 27 is a flat pattern having the same potential as the active surface of the IC chip. And a surface facing the metal case) and are connected via thermal vias. The IC chip 21 serving as a heating element is provided with COB (Ch
Ion Board) mounted, printed wiring board 23
A thermal via 26 having the same potential as the substrate of the IC chip 21 is provided on a surface of the IC chip 21 opposite to the active surface. Printed wiring board 23 on which IC chip 21 is mounted
A pattern 27 to which a thermal via 26 is connected is provided below the mounting surface of the IC chip 21 and on the opposite surface. This pattern 27 is also provided at a position facing the metal case 24, and a space between the metal case 24 and the pattern 27 is filled with a filler 25 having good heat conductivity.
The heat generated from the IC chip 21 is
Filler 25 via thermal via 26 provided in
From the metal case 24 to the metal case 24
By releasing heat to the outside of the card-type electronic device, the internal temperature rise is suppressed. In this method, heat generated from an IC chip is transmitted to a metal case via a thermal via provided on a printed wiring board and a filler having good heat conductivity. When the printed wiring board is multilayered and thickened,
In some cases, the thermal via becomes longer and the thermal resistance increases, making it impossible to efficiently release heat. Further, as shown in FIG. 3, the printed wiring board 23 and the metal case 2
4, the amount of the filler 25 filled between the printed wiring board 23 and the metal case 24 increases, and the thickness of the filler material increases. In some cases, the thermal conductivity becomes worse.

Accordingly, an object of the present invention is to provide a card-type electronic device capable of reducing the thermal resistance as much as possible and having high heat radiation.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and each component will be described below. A card-type electronic device according to claim 1 of the present invention includes: a metal case; and a semiconductor integrated circuit mounted such that a first surface forming an active surface is in contact with the case. Features. With such a configuration, the active surface of the semiconductor integrated circuit (IC chip) as the heating element is disposed so as to face the metal case, and the active surface of the IC chip and the metal case are in direct contact with each other. (Contact) structure. Therefore, the heat generated from the IC chip, which is a heating element, is directly transmitted from the IC chip to the metal case, so that the heat transfer distance to the outside is shortened, and heat can be transferred to the outside of the card-type electronic device extremely efficiently. Will be. Further, even if the density of the electronic circuit is increased and the printed wiring board is multilayered, the printed wiring board is not included in the heat transfer path, so that the heat dissipation efficiency is not affected.

Further, in the card-type electronic device according to the present invention, in addition to the contents described above, a surface of the metal case opposite to the first surface is in contact with the first surface. It is characterized by having possible projections. By adopting such a configuration, for example, when the density of the electronic circuit increases and the number of electronic components to be mounted increases, even when the electronic components have to be arranged between the printed wiring board and the metal case, Although the distance between the printed wiring board and the metal case increases, the distance between the printed wiring board and the metal case can be covered by the convex portion, so that the heat radiation efficiency does not deteriorate.

Further, in the card-type electronic device according to the third aspect, in addition to any of the above-mentioned contents, the metal case is set to a ground potential, and the metal case and the IC chip are grounded. And electrically connected to each other by contact with the pad. If the metal case is set to the ground potential as described above, the ground potential can be obtained from the case. Therefore, the electrode serving as the ground of the IC chip may be brought into contact with the metal case, and connection accuracy is not required.

According to a fourth aspect of the present invention, there is provided a card-type electronic device, wherein the semiconductor is mounted such that a metal case and a second surface opposed to the first surface forming the active surface are in contact with the case. And an integrated circuit. By adopting such a configuration, the heat generated from the IC chip, which is a heating element, is directly transmitted from the IC chip to the metal case as in the first embodiment, so that the heat transfer distance to the outside is also shortened, and extremely. Heat can be efficiently transmitted to the outside of the card-type electronic device. Further, even if the density of the electronic circuit is increased and the printed wiring board is multilayered, the printed wiring board is not included in the heat transfer path, so that the heat dissipation efficiency is not affected. In addition, since the IC chip is arranged so that the surface opposite to the active surface faces the metal case, the IC chip
The IC chip and the case can be relatively easily brought into contact with each other without worrying about the bonding area such as electrodes formed on the active surface of the chip.

In the card-type electronic device according to a fifth aspect of the present invention, in addition to the contents described above, a surface of the metal case facing the second surface can contact the second surface. It has a characteristic convex part. By adopting such a configuration, for example, when the density of the electronic circuit increases and the number of electronic components to be mounted increases, even when the electronic components have to be arranged between the printed wiring board and the metal case, ,
Although the distance between the printed wiring board and the metal case increases, the distance between the printed wiring board and the metal case can be covered by the convex portion, so that the heat radiation efficiency does not deteriorate.

According to a third aspect of the present invention, in addition to any one of the above-mentioned contents, the metal case is set to a ground potential.
By doing so, the IC chip is set to the ground potential, so that external noise countermeasures can be taken for the IC chip.

The card-type electronic device according to claim 7, wherein the semiconductor integrated circuit is in a bare chip state, a substrate on which the semiconductor integrated circuit is mounted, and at least a mounting surface side of the semiconductor integrated circuit. A metal case having a convex portion at the position where the semiconductor integrated circuit is mounted, and a pressing force such that the semiconductor integrated circuit and the convex portion come into contact with a surface of the substrate opposite to a surface where the semiconductor integrated circuit is mounted. And a spacer having an elastic force capable of applying the pressure. By adopting such a configuration, the structure is pressed against the metal case by the elasticity of the spacer, so that the IC chip and the metal case come into contact with each other with certainty. There is no loss of electrical continuity. Also, when any stress is applied to the metal case, the stress is absorbed by the spacer, thereby protecting the IC chip itself and leading to high reliability. Also good reworkability.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of the present invention. The case where the functions of the personal computer are integrated in an IC card-sized card-type electronic device (hereinafter, referred to as a “card”) has been described as an example. FIG. 1 shows a sectional view of the card.

Reference numeral 11 denotes an IC chip as a heating element. In this example, a central processing unit (hereinafter referred to as "C") having a relatively large amount of heat is used.
PU ”) as an example. This CPU is in a bare chip (unsealed) state, and is COB mounted. Reference numeral 12 denotes a metal case, which is preferably made of a material which has a certain strength so as to be able to withstand the exterior and has relatively good heat conduction. Specifically, for example, it is preferable to use a stainless steel plate. 13 is CPU1
Reference numeral 1 denotes a printed wiring board (hereinafter, referred to as a “second board”) on which the board is mounted. Reference numeral 14 denotes a printed wiring board (hereinafter, referred to as a “first board”) serving as a main board of the card.
Is a spring spacer, 16 is another electronic component, 17
Denotes a flexible tape, which electrically connects the second substrate 13 and the first substrate 14. The card is covered with a metal case 12, and the CPU 11 has its active surface (first
), That is, the surface on which the electrode is formed is the metal case 12 side. CPU1
The active surface 1 and the metal case 12 are in direct contact (contact) with each other, and in this example, no adhesive or the like is interposed between them. Thermal continuity is achieved by being in contact. It is also possible to make an electrical connection.
For example, a metal case is set to the ground potential as a measure against static electricity, and the metal case set to the ground potential and C
When the metal case functions as the ground potential if the ground potential pad of the PU 11 is in contact with the ground potential pad, the ground potential can be easily obtained, and the ground potential can be relatively wide, and the degree of freedom in arrangement can be increased. Will increase. CP
The active surface of U11 is connected to ground via a metal case 12. Heat from the heating element is radiated by radiation and conduction. In order to efficiently dissipate heat, it is necessary to adopt a structure in which the thermal resistance of these heat dissipation paths is reduced. However, in the present invention, a metal case 12 is directly connected from the CPU 11 which is a heating element. It is assumed that heat is efficiently transmitted and heat is radiated from the metal case 12 by radiation. IC chip 2 as a heating element as shown in FIG.
1 to thermal vias 2 provided on the printed wiring board 23
According to the present invention, the filler 25 having good heat conduction through the metal case 6 and the material that has been conducted to the metal case 24 and radiated by the radiation from the metal case 24 are, according to the present invention, directly transferred from the CPU 11 that is the heating element. The heat can be conducted to the case 12 made of metal, and the heat can be dissipated while minimizing the thermal resistance. In FIG. 1, the upper part of the CPU 11 of the metal case 12 is shown in a convex shape, but when there is no other electronic component on the same mounting surface as the CPU 11, the gap between the metal case 12 and the second substrate 13 is provided. It is only necessary to adopt a structure in which the CPU 11 comes into direct contact with the metal case 12 to reduce the number of cases. When another electronic component is mounted on the same mounting surface as the CPU 11, a convex portion is formed on the metal case 12 for height adjustment as shown in FIG. The CPU 11 has a lower thermal resistance than a filler material having good thermal conductivity or a separate metal member
The heat generated from the card can be released to the outside of the card.
Further, for example, when a card is composed of two printed wiring boards as shown in FIG. 1, means for electrically connecting the two substrates as shown in the figure, here, electrical connection using a flexible tape Is taking. If a flexible substrate is used, even if an external force is applied between the printed wiring boards and the distance between the printed wiring boards is slightly changed, it is possible to sufficiently cope with the expansion and contraction of the distance. Further, one of the substrates is particularly connected and fixed to the connector, but it is more effective if the other substrate has a free structure (not connected to the connector). By arranging a spring, that is, an elastic spacer between the two printed wiring boards, the CPU 11, which is a heating element, is constantly pressed against the metal case 12, and is electrically and thermally connected, and heat is released. Can be performed efficiently. The spacer used here may be a spring having a spring property, such as a coil spring, a leaf spring, or a silicone resin. With the above-described structure, the module in the card and the metal case are in close contact with each other, so that the module in the card is also prevented from rattling. In this example, the spacer is 2
Although it is arranged between two substrates, it does not need to be particularly between the substrates. Even if a single substrate covers the outside in a fixed state, for example, using a case is sufficient. It is possible to take the structure of the example.

In this embodiment, the active surface of the IC chip 11 is provided by COB mounting so as to face the case 12, but the surface opposite to the active surface (second surface), that is, the back surface of the IC chip faces the case. It may be provided as follows. In this case T
This can be easily achieved by performing AB mounting or face-down mounting. Further, a member having good heat conductivity may be provided between the IC chip 11 and the case 12. The member in this case is effective in that the member having an adhesive function can be firmly fixed.

[0015]

As described above, according to the present invention, an IC which is a heating element
Since heat is directly transmitted from the chip to the metal case, it is possible to efficiently transmit heat to the outside of the IC card.
Further, since the module in the IC card and the metal case are in close contact with each other, rattling of the module can be suppressed, leading to high reliability. Further, since the IC chip as the heating element is not directly joined to the metal case, but is pressed against the metal case by the elasticity of the spring spacer,
If any stress is applied to the metal case without impairing the electrical and thermal continuity between the IC chip and the metal case, the stress is absorbed by the spring-like spacer and high reliability is obtained. It is also good for rework.

[Brief description of the drawings]

FIG. 1 is a diagram showing a cross-sectional structure of an IC card of the present invention.

FIG. 2 is a diagram showing a heat dissipation structure of an IC chip before deriving the present invention.

FIG. 3 is a diagram showing a relationship between an IC chip and other electronic components before deriving the present invention.

[Explanation of symbols]

 Reference Signs List 11 CPU 12 Metal case 13 Printed wiring board on which CPU 11 is mounted 14 Printed wiring board serving as main IC card 15 Spring spacer 16 Electronic component 17 Flexible tape 21 IC chip as heating element 22 Sealing material (mold) 23) Printed wiring board 24 Metal case 25 Filler with good thermal conductivity 26 Thermal via 27 Solid pattern 28 Electronic component

Claims (7)

[Claims] 1. A card-type electronic device comprising: a metal case; and a semiconductor integrated circuit mounted such that a first surface forming an active surface is in contact with the case. 2. The card-type electronic device according to claim 1, wherein a surface of the metal case facing the first surface has a convex portion capable of contacting the first surface. machine. 3. The metal case is set to a ground potential, and is electrically connected by bringing the metal case into contact with a ground pad of the IC chip. 3. The card-type electronic device according to 1 or 2. 4. A semiconductor integrated circuit, comprising: a metal case; and a semiconductor integrated circuit mounted such that a second surface opposed to the first surface forming the active surface is in contact with the case. Card type electronic equipment. 5. The card-type electronic device according to claim 4, wherein a surface of the metal case facing the second surface has a convex portion that can contact the second surface. . 6. The card-type electronic device according to claim 4, wherein the metal case is set to a ground potential. 7. A semiconductor integrated circuit in a bare chip state, a substrate on which the semiconductor integrated circuit is mounted, and a projection at least covering a mounting surface of the semiconductor integrated circuit and mounted on the semiconductor integrated circuit. And a metal case having an elastic force capable of applying a pressing force such that the semiconductor integrated circuit and the projection come into contact with each other on the surface of the substrate opposite to the surface on which the semiconductor integrated circuit is mounted. A card-type electronic device, comprising: a spacer;