JPH05201184A - Ic memory card - Google Patents

Abstract

PURPOSE:To enrich workability, and to improve the reliability of electrical contacts by enhancing a conductive method between specified sections in an IC memory card. CONSTITUTION:Electricity is conducted between cover panels 3, 3' and between the cover panel 3 and the ground level of a circuit board 2 by using a conductive rubber or conductive forms in place of conventional coil spring and leaf spring. Accordingly, an IC memory card can be obtained, wherein the workability in assembly and the reliability of conduction between specified sections on the inside are improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an IC memory card which has greatly improved workability during assembly and reliability of internal electrical contact.

[0002]

2. Description of the Related Art Recently, an IC memory card has been widely used as a medium for storing information or supplying prewritten data to a main unit. These IC memory cards require that the main unit in which they are mounted must guarantee reliability against various noises.
Reliability against electromagnetic noise and static electricity noise is required.

For such a purpose, for example, by making the cover panel conductive and electrically shielding the IC memory card, the IC caused by electromagnetic waves coming from the outside is used.
Electromagnetic wave noise prevention to prevent the malfunction of the circuit board, and by conducting the potential of the cover panel to the ground level of the circuit board through an appropriate electric resistance and gradually releasing the energy, the ground level of the circuit board, the data bus, the address. Various measures have been taken such as static electricity noise countermeasures to prevent level fluctuations.

FIG. 3 shows a typical example of such a conventional IC memory card. FIG. 3 (a) is a sectional view thereof and FIG. 3 (b) is a perspective view showing a state where a cover panel is removed. .. In FIG. 3A, a circuit board 2 on which a group of electronic components mainly including a memory IC is mounted, and a connector 6 for making an electrical connection to the outside are arranged by spacers 4 and 4 ′ and a frame 5 in position. , And their front and back surfaces are covered with conductive cover panels 3, 3 '. The connector may be a so-called card edge type in which terminals are exposed on the circuit board or a so-called shutter type in which this is covered with a slide type cover. Further, spacer holes 8, 8'and 9 are formed in the spacers 4 and 4 ', and a board hole 7 is formed in the circuit board 2 at a position corresponding to the spacer holes 8 and 8'.
Are opened and coil springs 12 and 12 'are fitted in these positions, respectively.

As shown in FIG. 3, both ends of the coil spring 12 are electrically contacted with the inner walls of the cover panels 3 and 3'to establish continuity between the cover panels, and both ends of the coil spring 12 'are covered with the cover panel. Three
By electrically contacting the inner wall of the pad and the pad 10 connected to the ground level of the circuit board 2, the electromagnetic wave shielding property for the IC memory card is maintained and at the same time, the electrostatic charge energy charged on the cover panel is grounded on the circuit board. Measures against static electricity noise by releasing to level,
Such measures were taken. The pad 10
May be directly connected to the ground level of the circuit board 2 for this purpose, but suppresses transient fluctuations,
For the purpose of controlling the discharge current, it is often connected to the ground level of the circuit board via a discharge resistor 11 of 100 KΩ to 1 MΩ.

FIG. 4 shows a leaf spring 1 mounted on a circuit board 2 instead of the coil spring 12 shown in FIG.
3 shows an example in which an electrical connection is made between the cover panels 3 and 3 '. In both of the examples of FIGS. 3 and 4, the spacers 4 and 4 ′ do not need to be present on the upper and lower sides of the circuit board 2 and are present on only one side, and the circuit board 2 and the connector 6 are not provided. Some hold the position of.

The material of the conductive cover panels 3 and 3'may be a metal plate or a plastic sheet, which is attached to the surface contacted by the coil springs 12 to 12 'with a metal foil or a vapor deposition method. The conductive layer may be formed.

Although such a conventional IC memory card structure has been put to practical use due to its reliability against electromagnetic waves and static electricity, it is used for a circuit board, a plate spring is attached, or a circuit board, a connector and a frame are installed. After assembling, the work of assembling the coil spring at the predetermined hole position is troublesome, and the IC
Not only was the contact between the coil spring or leaf spring and the cover panel not always reliable, it was a major bottleneck in the manufacturing process of the memory card, and the reliability was slightly poor. A measure for improving contact reliability was desired.

[0009]

SUMMARY OF THE INVENTION The present invention has been made as a result of various studies in view of the drawbacks of the conventional IC memory card as described above, and an object thereof is to provide a conventional coil spring or leaf spring. The present invention aims to provide an IC memory card with improved workability in assembly and reliability of electrical contact by adopting a new electrical contact method as an alternative.

[0010]

That is, the present invention provides a circuit board on which an electronic component group mainly composed of a memory IC is mounted,
A connector having electrical connections between the circuit board and the outside, a frame and a spacer for holding the circuit board and the connector, and an IC having two cover panels that cover the circuit board, the connector, the frame and the spacer as basic components. In the memory card, between the cover panels, and between the cover panel and the ground level of the circuit board,
An IC memory card is characterized in that it is electrically conducted through a conductive rubber or a conductive foam.

The present invention will be described in detail below with reference to the drawings. 1A and 1B show an example of the structure of an IC memory card according to the present invention. FIG. 1A is a sectional view thereof, and FIG. 1B is a perspective view with a cover panel removed. In FIG. 1A, a group of electronic components 1 is mounted, a connector 6 is mounted on one end of the circuit board 2, spacers 4 and 4 ′, a frame 5, a circuit board 2, and the spacer 4 is provided. The configuration relating to the holes 8 and 8'provided, the holes 9 provided in the spacer 4 ', the pad 10 on the circuit board 2 and the discharge resistor 11 is basically the same as that of the conventional IC memory card shown in FIG. There is no place. In the present invention, the connector may be a card edge type or a shutter type other than the connector shown in FIG. 1, and the spacer is not limited to the one shown in FIG.
It may be present only in one of the upper and lower sides of.

In the present invention, instead of the conventional coil spring or leaf spring, the conductive connection between the cover panels 3 and 3'or between the cover panel 3 and the pad 10 is made of conductive rubber or conductive foam. The biggest feature is to do it. Needless to say, the smaller the volume resistivity of the conductive rubber or the conductive foam used in the present invention, the more preferable it is, but it is preferable to use one having a resistivity of 10 ⁵ Ω-cm or less. That is, if the volume resistivity of the conductive rubber or conductive foam is at most this value or less, the volume of the cavity formed by the spacer holes 8, 8'and the substrate hole 7 shown in FIG. Since the height is about 3 mm and the height is about 2 to 3 mm, the electric resistance value of the conductive rubber or the conductive foam to be charged therein is kept at about 1 MΩ at the maximum.

When the electric resistance value between the upper and lower cover panels is such a level, even if the potential of at least one of the cover panels fluctuates due to electromagnetic waves, static electricity, etc., the potential of the upper and lower cover panels except for the initial time. Is maintained at the same level, and the discharge resistance value is an appropriate value, whereby the effect of suppressing the discharge current is also exerted, which is preferable, and it can be used as a sufficient conductor in practical use.
If the electric resistance is more than this value, the shielding effect will be weakened, and the charge up on the cover panel or the level fluctuation between the cover panels will be noticeable, which is not preferable. Therefore, the volume resistivity of the conductive rubber or conductive foam is 10 ⁵
It is desirable to select a material of Ω-cm or less.

In the present invention, the conductive rubber or the conductive foam is not necessarily the same as the one shown in FIG. 1, and the cavity formed by the spacer holes 8 and 8'and the substrate hole 7 and the spacer hole 9 are formed. The present invention is not limited to being present in any of the cavities formed in 1., and even if it is present only in one of the cavities as shown in FIG. 2, a considerable effect is exhibited as compared with the prior art. Of.

As the material of the conductive rubber or conductive foam used in the present invention, silicone-based, SBR-based, butyl-based, nitrile-based, chloroprene-based, urethane-based materials can be used as long as they have excellent mechanical properties and strain characteristics. The type of material is not particularly limited, such as rubber such as, or foam molded products such as polyvinyl chloride, polystyrene, polyethylene, polypropylene, etc., but especially for conductive rubber, it is excellent in a wide temperature range. Silicone-based materials that exhibit compressive strain characteristics and are chemically stable and are widely used in calculators, etc., and polyethylene and polystyrene that exhibit appropriate elasticity and excellent compression recovery as electrically conductive foams. Etc. can be mentioned as a preferable material.

The so-called π-electron transfer type additives such as carbon black, graphite and carbon fiber may be added as additives for imparting conductivity to these base materials, and free electron transfer such as gold, nickel and copper. Although it may be of a mold type, the type is not particularly limited, but generally, carbon black, which is inexpensive, rich in workability and moldability, and whose resistance is easy to control by the added amount, may be mentioned as a suitable material. it can.

Further, the conductive rubber or conductive foam used in the present invention ensures electrical contact between the cover panels or between the cover panels and the pads when the cover panels are finally assembled. , The spacer holes 8 and 8'and the substrate hole 7 or the holes formed by the spacer holes 9 are prepared to be 0.2 mm to 0.5 mm larger than the height of the cavity, and when the cover panels are finally attached, the conductive property is obtained. It is preferable that the elastic rubber or conductive foam is packed so as to be slightly compressed. Furthermore, in order to obtain more reliable electrical contact, JIS hardness 70 to 1
More preferable results can be obtained by using a material having a compression strain of about 50 and a compression strain of about 20%.

The shape of the conductive rubber or the conductive foam used in the present invention does not have to be a columnar shape or a straight pillar shape, and a method of laminating thin slices may be used. Small pieces are randomly formed into holes. It does not matter if you stuff it in, so when you attach the cover panels,
If its both ends are in contact with the inner wall of the cover panel or the pads on the circuit board, and do not contact the lead terminals of the mounted parts or the peripheral pads, specify its shape, size, packing method, etc. It is not something to do.

In the present invention, it goes without saying that the same effect can be obtained even if the cover panel is made of metal or a plastic sheet having a conductive layer formed on the inner surface thereof, but the latter is particularly effective. When using a conventional coil spring or leaf spring, the mechanical resilience of itself is so large that the cover panel may be noticeably lifted after the cover panels are finally assembled and assembled. On the other hand, according to the method of the present invention, since the repulsive force of the conductive rubber or the conductive foam is smaller than that of the coil spring or the leaf spring, the cover panel does not float after assembly, and the appearance is good. There is also an advantage that can be obtained.

[0020]

EXAMPLES Examples and comparative examples of the present invention will be given below. Example 1 and Comparative Example 1 As shown in FIG. 1, an IC memory card having a total of eight electronic component groups mainly composed of a 1 Mbit SRAM chip mounted on a circuit board has two spacers and two parts on the circuit board. I made a hole. The size of this hole is 2.5mm in diameter,
The height was 2.6 mm between the cover panels and 1.1 mm between the circuit board and the cover panel. The holes had a diameter of 2.0 mm and a height of 3.0 mm and 1.5 mm, respectively, and had a volume resistivity of 2 × 10 ⁴ Ω-cm, which was made of polyethylene as a base material and carbon black as an additive. An IC memory card prepared by assembling the foam at the time of assembling and further pasting a 200 μm thick stainless steel sheet as a cover panel,
As a comparative example, 20 conventional IC memory cards similar to this were prepared, except that a phosphor bronze coil spring having a height of 3.0 mm and 1.5 mm and having 8 turns was placed in each hole.

The cover panel is a stainless steel sheet having a thickness of 200 μm, and a heat-sensitive adhesive sheet was used for bonding, and after heating under pressure at a temperature of 115 ° C. and a pressure of 200 g / cm ² for 60 seconds, the same pressure was applied. It was cooled to room temperature. The assembling time of these IC memory cards was 11 minutes for the former and 17 minutes for the latter.

To the cover panel of these IC memory cards, a probe of a discharge tester having a discharge time constant of 100Ω and 150 pF was charged up to a voltage of +15 KV, and the cover panel was charged 10 times at arbitrary positions on the cover panel, followed by −.
After discharging the battery at a voltage of 15 KV for 10 times each, for a total of 20 times, when it was mounted on the main unit and accessed, which IC
The memory card also worked normally, and no abnormality was found. Next, these IC memory cards are attached to the main body device, and the frequency of 144 MHz,
Also, when a radio wave with an oscillation output of 1 W at 430 MHz was radiated from a position where the distance between the antenna and the IC memory card was 1 m, this also maintained normal operation in any IC memory card, and no abnormality was found. Was not recognized.

Example 2 A conductive rubber having a volume resistivity of 1 × 10 ⁵ Ω-cm as a base material made of silicone rubber and having carbon fibers added thereto was used as an internal electric conductor for electrical contact. ,
Twenty IC memory cards similar to those in Example 1 were prepared.
The assembly time was 10 minutes per sheet. Further, when the same test as in Example 1 was conducted, no abnormality was found in both the discharge test and the radio wave test.

Example 3 An IC memory card similar to that of Example 1 was used except that the cover panel was a polycarbonate sheet having a thickness of 150 μm and an aluminum foil having a thickness of 50 μm was attached to one surface thereof. One sheet was prepared. Also for this sample, the same results as in Example 1 were obtained in all of the assembly time, the discharge test, and the radio wave test. Furthermore, when these IC memory cards were left to stand at 50 ° C. for 48 hours, no floating of the cover panel portion corresponding to the position where the conductive rubber was charged was observed and the appearance was good.

Comparative Example 2 The volume resistivity of polyethylene conductor foam is 1 × 10.
^When 20 pieces of IC memory cards similar to those in Example 1 were prepared except that the value was ⁶ Ω-cm, the assembly time was 1
It was the same as 11 minutes per sheet, but after performing the same discharge test as in Example 1, even if 5 sheets were mounted on the main body device, normal access could not be performed. When a radio wave test was further conducted, 8 sheets malfunctioned during the test.

Comparative Example 3 Twenty conventional IC memory cards similar to those of Example 1 were prepared except that the same cover panel as that of Example 3 was used. When this was assembled and left for 48 hours at 50 ° C. in the same manner as in Example 3, 16 pieces of floating occurred on the cover panel at the position corresponding to the coil spring.

[0027]

As is apparent from the above description, in the present invention, instead of the coil spring or the leaf spring, the conductive rubber or the conductive foam is used for the electrical contact inside the IC memory card. It is possible to realize a significant improvement in workability and improved reliability of electrical contact compared to
In addition to its great manufacturing advantages, especially in the case of IC memory cards that use a rigid plastic sheet for the cover panel, it prevents the cover panel from floating.
The effect is great.

[Brief description of drawings]

FIG. 1 is an example of a structure of an IC memory card according to the present invention, (a) is a cross-sectional view, and (b) is a perspective view with a cover panel removed.

FIG. 2 is a sectional view showing another example of the structure of the IC memory card according to the present invention.

FIG. 3 is an example of a structure of a conventional IC memory card,
(A) is sectional drawing, (b) is a perspective view of the state which removed the cover panel.

FIG. 4 is a sectional view showing another example of the structure of a conventional IC memory card.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electronic component 2 Circuit board 3, 3'Cover panel 4, 4'Spacer 5 Frame 7 Board hole 8, 8 ', 9 Spacer hole 10 Pad 12, 12' Coil spring 13 Leaf spring 14, 14 'Conductive material

Claims (1)

[Claims] 1. A circuit board on which an electronic component group mainly composed of a memory IC is mounted, a connector for electrically connecting the circuit board to the outside, a frame and a spacer for holding the circuit board and the connector, and the circuit. In an IC memory card having two cover panels as basic components for covering a board, a connector, a frame and a spacer, conductive rubber or a rubber is used between the cover panels and between the cover panel and the ground level of the circuit board. I, characterized in that it is electrically conducted through a conductive foam
C memory card.