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BACKGROUND OF THE INVENTION
1. FIELD OF THE INVENTION
This invention relates to non-contact type IC cards durable under the
presence of contaminants or dust and, more particularly, to an IC card
having an electromagnetic induction interface using coils.
2. DESCRIPTION OF THE RELATED ART
A type of IC card which can be effectively improved by the present
invention, i.e., an IC memory card which performs parallel transfer of
8-bit (N=8) data will be described below.
IC memory cards (hereinafter referred to as IC cards) are grouped into (1)
a multiple pin type and (2) a noncontact type with respect to the method
of connection to terminal units, as described on page 24 of "IC card"
edited by Denshi Joho Tsushin Gakkai and published by Ohmsha, Ltd. In the
case of multiple pin type cards, data exchange can be performed between
the IC card and the terminal by 8-bit or 16-bit parallel data transfer,
and data can be read from or written in the card at a high speed of about
200 nsec/byte at present. Non-contact type cards have no contact portions
and are therefore free from various problems due to mechanical contacts.
Non-contact type cards can be used in a bad operating environment such as
a factory automation environment since they can have a completely sealed
structure. Non-contact systems are advantageous when used as a means for
solving the following problems relating to the connection method for
multiple pin type IC cards:
(1) a change in internal data or breakdown of internal ICs caused by static
electricity entering through connector terminals,
(2) data error or a transmission/reception disabled state due to terminal
contact failure,
(3) failure of connection between the card and the terminal unit due to
deformation (spreading) of terminals, and
(4) a need for a large insertion/withdrawal force to an ejection mechanism
owing to the existence of many pins.
Light, electromagnetic induction or microwaves may be used as a means for
supplying power or effecting transmission/reception in a non-contact
manner. For non-contact IC cards presently put to practical use, however,
a type of electromagnetic induction system which uses what is ordinarily
called a sheet coil is adopted for portability, power consumption and
performance of the card.
FIG. 13 is a schematic illustration of internal parts of a conventional
sheet coil type IC card in a mounted state. As illustrated, a large sheet
coil 2, three small sheet coils 3, a control IC 4, a memory IC 5 and a
battery 6 are mounted on a printed circuit board 1. The large sheet coil 2
is a coil for receiving power and clock signals supplied from a terminal
unit to the IC card (hereinafter referred to as a "power coil"). The small
sheet coil 3 consists of three coils, for example, a data receiving coil
3a, a data transmitting coil 3b, and an instruction signal receiving coil
3c. The sheet coils 2 and 3 are formed in the same manner as the
conventional pattern formation on a printed circuit board (not
specifically illustrated). The memory IC 5 is an IC for storing data, and
the control IC 4 is an IC for controlling reading of data from the memory
IC 5 or writing data in the memory IC 5 based on an instruction signal
received by the sheet coil 3c. The battery 6 is an internal battery for
maintaining the data in the memory IC 5. FIG. 14 is a block diagram of the
electrical connection of the IC card shown in FIG. 13. A part of the
signal obtained by the power coil 2 is supplied to the control IC 4
through a clock signal line 7 and the part rectified by the rectifier
circuit 8 is supplied as DC power 9 to the control IC 4 and the memory IC
5. Two diodes 10 serve to stop DC currents from the rectifier circuit 8
and the battery 6 from reversely flowing to the power source. A received
data line 11 serves to deliver received data from the receiving coil 3a to
the control IC 4. A transmitted data line 12 serves to deliver transmitted
data from the control IC 4 to the transmitting coil 3b. An instruction
signal line 13 serves to deliver an instruction signal obtained by the
instruction signal receiving coil 3c to the control IC 4. All signal
exchanges between the card and the external unit (not shown) to which the
card is connected are effected by using serial signals. Data exchange
between the control IC 4 and the memory IC 5 is carried out by sending
through an 8-bit data bus 14 8-bit parallel data into which the serial
data is converted, if the control IC 4 has a parallel/serial data
conversion function. Sheet coils (not shown) corresponding to the sheet
coils 2 and 3 are provided on the terminal side in positions such as to
respectively face the sheet coils on the card side while being maintained
close to the same, when the card is connected to the terminal. Currents
induced in the sheet coils on the IC card side have differential
waveforms. Capacitors having small capacitances (not shown) are connected
to the signal lines 7, 11, 12 and 13 shown in FIG. 14 to convert, by
integration, the differential waveform induction currents into signals
which can be processed or used by the control IC 4. This type of IC card
further includes several control signal lines, address lines and the like,
which will not be specifically described in detail.
As mentioned above, the conventional sheet coils 2 and 3 shown in FIGS. 13
and 14 are formed in the same manner as printed circuit board patterns.
That is, a copper foil is formed on the base by plating, and a resist is
applied to portions of the copper foil layer which are to be left, i.e.,
portions for forming spiral coil conductors, and etching is thereafter
performed. After the etching, the resist is removed. The sheet coils
thereby formed have small sizes; for example, the power coil 2 has a
larger size, a diameter of about 20 mm (the number of turns: about 20),
and each of the receiving coil 3a, the transmitting coil 3b and the
instruction signal receiving coil 3c has a smaller size, a diameter of
about 10 mm (the number of turns: about 5).
The non-contact IC card having this electromagnetic induction system
performs serial data transmission as mentioned above. The data transfer
rate is 500 kbits/sec (2 .mu.sec/bit), which is higher than the data
transfer rates of other non-contact systems. This rate is, in terms of the
rate of byte transfer for transferring 8-bit data parallel, about 60
kbytes/sec (16 .mu.sec/byte) which is much lower than 5 m bytes/sec (200
nsec/byte) of the multiple pin type IC cards basically designed for
parallel transfer. This non-contact transfer system is therefore
unsuitable for data transmission/reception using an IC card having a large
capacity of several hundred bytes.
FIG. 15 is an enlarged plan view of one of the sheet coils shown in FIG.
13, FIG. 16(a) is a schematic sectional side view of portions of the IC
card and the terminal connected in an aligned state, showing lines of
magnetic force when the sheet coils of the IC card and the terminal facing
each other are connected by electromagnetic induction coupling, and FIG.
16(b) is a schematic sectional side view showing lines of magnetic force
when these sheet coils are electromagnetic-induction coupled in slightly
shifted positions. As shown in FIG. 15, pads or lands 20 are provided for
electrical connection at the two ends of a coil winding 18. As shown in
FIG. 16(a), when the IC card is correctly set on the terminal, almost all
lines of magnetic force 26 produced by a sheet coil 22 on the terminal
side interlink with a sheet coil 24 provided on the IC card side and
facing the sheet coil 22 while being maintained close to the same, a
current is induced in the sheet coil 24 in accordance with the Lenz's law,
thereby transferring the signal in a non-contact manner. If the IC card is
placed on the terminal in a shifted position as shown in FIG. 16(b), only
part of the lines of magnetic force 26, e.g., 3/4 of the same interlink
with the sheet coil 24, so that the electromotive force induced in the
sheet coil 24 is reduced to 3/4, and that the induced current is
correspondingly reduced to 3/4. The degree of coupling for data
transmission and the reliability of the non-contact system are thereby
reduced.
In the electromagnetic induction non-contact IC card thus constructed, the
sheet coils for transmitting signals in a non-contact manner occupy a
large area on the printed circuit board. The provision of these sheet
coils makes it difficult to develop large-capacity IC cards in which many
memory ICs are mounted on the printed circuit board. To further increase
the data transfer rate, the present serial data transmission system may be
replaced with, for example, a parallel data transmission system for
transmitting 8-bit data parallel. In such a case, there is a need for a
further increase in the number of coils arranged, and it is therefore
difficult to construct the card for parallel data transmission. Moreover,
the degree of electromagnetic induction coupling is easily reduced by an
error in positioning the terminal and the IC card relative to each other,
so that the current induced in the opposed sheet coil is changed and
cannot be constantly maintained with stability, resulting in deterioration
of the reliability of data transmitted between the terminal and the IC
card. The conventional non-contact type IC cards exhibit these drawbacks.
SUMMARY OF THE INVENTION
In view of the above-described problems, an object of the present invention
is to provide an electromagnetic non-contact type IC card in which the
area occupied by the coils is reduced by using smaller and thinner data
transfer coils, and in which parallel data transmission is effected
between a terminal and the IC card at a high speed with improved
reliability.
In other to achieve this object, according to one aspect of the present
invention, there is provided a non-contact type IC card based on an
electromagnetic induction system wherein, to effect N-bit parallel data
transfer between the card and a terminal unit for reading or writing data
to the card, N thin-film coils formed of at least one layer of a laminated
spiral electrically conductive pattern formed by thin-film technology are
arranged on an insulating base at a position in the IC card close to the
terminal unit facing the terminal unit.
According to another aspect of the present invention, each of the N
thin-film coils is formed as a thin-film pot core coil having a pot core
formed by thin-film technology.
According to still another aspect of the present invention, shielding walls
for shielding from lines of magnetic force formed by the thin-film
technology are provided between adjacent coils of the N-thin-film pot core
coils.
According to a further aspect of the present invention, one or a plurality
of thin-film pot core coils and shielding walls are covered with an
insulating material by molding to form a coil module.
In the non-contact type IC card of the present invention, for N-bit
parallel data transfer between the card and the terminal unit, N thin-film
coils formed of at least one layer of a laminated spiral electrically
conductive pattern formed by thin-film technology are arranged on an
insulating base, thereby achieving an increase in the data transfer rate.
According to a still further aspect of the present invention, the N coils
are thin-film pot coils formed by thin-film technology, thereby preventing
leakage of lines of magnetic force and stabilizing the signal even when
the IC card and the terminal are incorrectly positioned.
According to a still further aspect of the present invention, shielding
walls for shielding from lines of magnetic force formed by thin-film
technology are provided between the adjacent coils of the N thin-film pot
core coils, thereby preventing interference between the adjacent coils on
each of the terminal unit or the IC card and enabling the coils to be
arranged at a high density.
According to a still further aspect of the present invention, the thin-film
pot core coils and the shielding walls are covered with an insulating
material by molding to form a coil module which is easy to handle.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic illustration of internal parts of a non-contact type
IC card in a mounted state in accordance with the present invention;
FIG. 2 is a block diagram of electrical connection of the IC card shown in
FIG. 1;
FIGS. 3(a) and 3(b) are a sectional side view and a plan view of a
thin-film coil having a one-layer spiral coil winding;
FIGS. 4(a) and 4(b) are a sectional side view and a plan view of a
thin-film coil having a laminated spiral coil winding;
FIGS. 5(a)-5(f) illustrate a process for manufacturing the thin film coil
shown in FIG. 3;
FIG. 6 is a sectional view of the relationship between a terminal unit and
the IC card in accordance with the present invention;
FIG. 7 is an enlarged perspective view of a pot core coil in accordance
with the present invention;
FIGS. 8(a) and 8(b) are sectional side views of lines of magnetic force
produced when pot core coils of the IC card and the terminal unit facing
each other are coupled by electromagnetic induction;
FIG. 9 is a perspective view of a state in which shielding walls are
provided between the pot core coils in accordance with the present
invention;
FIG. 10 is a sectional side view of lines of magnetic force produced when
the opposed pot core coils of the terminal unit and the IC card with
shielding walls shown in FIG. 9 are coupled by electromagnetic induction;
FIGS. 11(a)-11(g) and 12(a)-12(g) are plan views and sectional side views
of a process for manufacturing the pot core coils in accordance with the
present invention;
FIG. 13 is a schematic illustration of internal parts of a conventional
sheet coil type IC card in a mounted state;
FIG. 14 is a block diagram of the electrical connection of the IC card
shown in FIG. 13;
FIG. 15 is an enlarged plan view of one of the sheet coils shown in FIG.
13; and
FIG. 16(a) and 16(b) are sectional side views of lines of magnetic force
produced when the sheet coils of the conventional IC card and the terminal
facing each other are coupled by electromagnetic induction.
DESCRIPTION OF THE REFERRED EMBODIMENT
An embodiment of the present invention will be described below with
reference to the accompanying drawings. FIG. 1 schematically shows
internal parts of a non-contact type IC card in a mounted state in
accordance with an embodiment of the present invention. This IC card
performs, for example, N=8 bit parallel data transmission. The components
of this embodiment corresponding or identical to those of the arrangement
shown in FIG. 13 are indicated by the same reference characters. A
thin-film coil module 15 has nine coils: eight transmitting/receiving
thin-film coils 15a to 15h for effecting 8-bit parallel data transmission,
and one instruction signal receiving coil 15i for receiving instruction
signals. These coils are arranged in a 3.times.3 form and are molded in an
insulating material by. The nine thin-film coils 15a to 15i may be
integrally combined and formed as the thin-film coil module 15 or may be
formed separately from each other. The arrangement of the coils 15a to 15i
is not limited to that shown in FIG. 1 the coils 15a to 15i may be
suitably arranged according to the available mounting space. A control IC
41 is provided which can control transmission/reception of 8-bit parallel
data. FIG. 2 is a block diagram of electrical connections of the IC card
shown in FIG. 1. The thin film coils 15a to 15h and transmitted/received
data lines 16a to 16h are used in common for bidirectional data transfer
for reception and transmission of 8-bit parallel data. The control IC 41
determines whether or not an instruction received from the instruction
signal line 13 is a data write instruction or a data read instruction, and
effects bidirectional control of 8-bit parallel data in accordance with
this instruction. A device, e.g., a general purpose gate IC "74HC245" or
its equivalent in functions may be used for an input stage of the control
IC 41.
FIGS. 3(a)-4(b) show enlarged views of examples of one of the coil elements
of the thin-film coil module shown in FIG. 1. FIGS. 3(a) and 3(b) show a
thin-film coil having a one-layer spiral coil winding; FIGS. 4(a) and 4(b)
show a thin-film coil having a laminated spiral coil winding; FIGS. 3(a)
and 4(a) are sectional side views; and FIGS. 3(b) and 4(b) are plan views
showing coil windings alone viewed from above. The thin-film coils shown
in FIGS. 3(a)-4(b) are formed by, for example, the present technology
relating to manufacture of thin-film coils for thin-film magnetic heads
used for stationary hard disk units (hereinafter referred to as "thin-film
technology"). Pads 20 for connection to the circuit are also formed at the
two ends of the coil winding 18. The present thin-film technology enables
manufacture of a 48 turn spiral coil having widths of 0.2 to 0.3 mm and a
thickness of 0.01 mm. In this embodiment, 10 turn spiral coils having
several millimeter (mm) widths may be formed. It is therefore possible to
form a group of coils occupying a smaller area in comparison with the
conventional coils.
The following equation represents the relationship between the inductance,
the number of coil winding turns, and the inside and outside diameters the
coil windings, which is used in inductance design:
L=20.32a.sup.2 n.sup.2 /(6a+10c)[nH]
where a=(d.sub.o +d.sub.i)/4,c=(d.sub.o +d.sub.i)/2, d.sub.o =outside
diameter (.mu.m), d.sub.1 =inside diameter, and n=number of turns. That
is, the inductance of the spiral coil is increased if the number of turns
and the outside diameter are larger and if the difference between the
inside and outside diameters is minimized. Accordingly, to provide many
spiral coils having a substantial inductance in a restricted area on the
printed circuit board, the inside and outside diameters are set close to
each other and the pitch of the spiral pattern formed in the narrow area
defined by the inside and outside diameters is reduced to maximize the
number of turns. According to the conventional method of forming a coil
winding by etching a copper foil on a printed circuit board, the etching
pattern width and the pattern spacing are about 100 .mu.m at the minimum.
In contrast, the thin-film technology makes it possible to reduce the
corresponding size to several microns (.mu.m) as well as to form a very
thin lamination. Consequently, it enables a reduction in the diameter of
the thin film coil and, hence, a reduction in the area in which the
thin-film coils are mounted on the printed circuit board. h FIGS.
5(a)-5(f) illustrate a process of manufacturing the thin-film coil based
on the thin-film technology. This process will be schematically described
below. First, as shown in of FIG. 5(b), copper substrate sputtering is
performed over the upper surface of an insulating base 17 shown in of FIG.
5(a) to form a copper substrate layer 18a having a thickness of about 0.1
.mu.m on the whole insulating base 17 surface. Next, portions on which the
coil winding 18 is not to be formed are covered with a resist 18b by
resist patterning, as shown in of FIG. 5(c). That is, the pattern of the
resist 18b is formed as a reversal pattern for the coil pattern. Copper
coil pattern plating is thereafter performed to form a plating portion 18c
on the surface of the copper substrate layer 18a corresponding to coil
winding 18, as shown in of FIG. 5(d). The thickness of the plating portion
is about 2 to 4 .mu.m. Thereafter, as shown in of FIG. 5(e ), the resist
18b is removed and unnecessary portions of the copper substrate layer 18a
are also removed by sputter etching, thereby forming the coil winding 18
on the insulating base 17. The coil winding 18 is thereafter covered with
an insulating layer 19 as shown in of FIG. 5(f). This is performed by a
photoresist insulating layer forming step and a baking step.
As shown in FIG. 6, a thin-film coil module having the same construction
(wherein the coils are arranged to face the corresponding coils of the IC
card) is also provided in a connector 50a of a terminal unit 50 into which
an IC card 100 of the present invention is inserted (for connection). The
coil module provided in the connector 50a is disposed in a coil section
150b which is opposed to a coil section 150a of the IC card 100.
The electromagnetic induction non-contact type IC card having the
above-described thin coils performs parallel 8-bit data
transmission/reception and has a data transfer rate of 500 kbytes/sec (2
.mu.sec/byte) which is 8 times higher than the data transfer rate of the
conventional 8 bit serial type IC card. Although this rate is one order of
magnitude lower than that of the contact-type multi-pin IC card, the IC
card of the present invention is advantageous in that the IC card and the
terminal unit have completely sealed structures and can therefore be used
in a severe environment in the field of factory automation. Since the area
occupied by the coils is reduced and since the data transfer rate is
increased, the number of memories 5 and, hence, the memory capacity can
easily be increased, as shown in FIGS. 1 and 2.
To obtain more stable electromagnetic induction coupling even if the card
and the terminal are incorrectly positioned relative to each other, each
of the thin-film coils of the thin-film coil module may be provided with a
pot core. FIG. 7 is an enlarged perspective view of a pot core coil
provided for this purpose, before the coil is covered by molding. FIG.
8(a) is a sectional side view of lines of magnetic force produced by
electromagnetic induction coupling of pot core coils of the IC card and
the terminal opposed to each other when the IC card and the terminal are
connected in correct positions, and FIG. 8(b) is a sectional side view of
lines of magnetic force produced by electromagnetic coupling when the
positions of the IC card and the terminal and, hence, the pot core coils
provided therein are slightly shifted from each other. Referring to FIG.
7, a pot core 33 of a pot core coil 30 formed on an insulating base 35 is
E-shaped in section such as to fill a central and surround an outer
peripheral portion and a bottom portion of a coil winding 33. A gap 33d
for leading the two ends of the coil winding 31 out of the pot core 33 is
formed in an outer peripheral portion of the pot core 33. The surface of
the coil winding 31 is covered with an insulating layer 34. Pads 32 are
attached to both ends of the coil winding 31. The pot core coil 30 is also
formed based on the above-described thin-film technology. Consequently,
the size of each pot core coil and the overall size of a coil module in
which a plurality of pot core coils constructed in this manner are housed
are effectively reduced in comparison with the conventional arrangement. A
process of manufacturing the pot core coil will be described later.
In the case of an IC card having this type of pot core coil, when the IC
card is connected to the terminal while being incorrectly positioned as
shown in FIG. 8(b), as well as when the IC card is connected to the
terminal while being correctly positioned so that the centers of pot core
coils 30a and 30b of the IC card and the terminal coincide with each other
as shown in FIG. 8(a), almost all lines of magnetic force 38 produced by
the pot core coil 30a of the terminal, for example, are led together to
the pot core of the pot core coil 30b of the IC card opposed to the pot
core coil 30a and maintained close to the same through a magnetic path
having small magnetic reluctance. Even in the state shown in FIG. 8(b),
therefore, the magnetic flux leakage is small, and substantially the same
electromagnetic induction current as the state shown in FIG. 8(a) is
generated in the coil winding 31 of the pot core coil 30b. Thus, if a pot
core coil is used which has a structure such that a central portion and a
bottom portion connecting these portions surround the coil winding 31 and
these are formed of a material such as ferrite having a high relative
magnetic permeability, the possibility of an error in data transfer due to
an error in positioning the terminal and the IC card is reduced. Since a
material such as ferrite having a high relative magnetic permeability is
used to form the pot core, the number of turns, the diameter of the coil
and the coil current can be reduced in comparison with sheet coils formed
on a printed circuit board by the conventional method, while substantially
the same electromagnetic induction current is generated.
In a case where a plurality of coils are disposed close to each other on
each of the IC card and the terminal, there is a possibility of leakage of
magnetic force lines, i.e., interference between, for example, adjacent
coils of the IC card and, hence, a possibility of a failure to correctly
transmit data. To cope with this problem, shielding walls may be provided
between adjacent pot core coils. FIG. 9 is a perspective view of part of a
pot core module having shielding walls before the coil module is covered
by molding, and FIG. 10 is a sectional side view of magnetic force lines
produced when the pot core coils of the terminal unit and the IC card with
the shielding walls are coupled by electromagnetic induction. As
illustrated, almost all the magnetic force lines 38 produced by the pot
core coil 30a of the terminal interlink with the pot core coil 30b of the
IC card facing the pot core coil 30a. The magnetic force lines leaking
from the outer peripheral portion of the pot core coils 30b of the IC card
strike shielding walls 39 and are absorbed therein as an energy loss, and
the possibility of the magnetic flux leakage influencing the adjacent pot
core coils or unassociated pot core coils of the terminal facing the IC
card is therefore very small. Consequently, it is possible to prevent
interference between adjacent coils, to mount the coils at a high density
in a restricted area and to reduce the area occupied by the coils. The
shielding walls 39 may be formed of an electrically conductive material
such as aluminum and may have a height higher than that of the core and a
width, thinner than that of the outer peripheral portion of the core. The
shielding walls 39 are formed based on thin-film technology like the pot
cores, the coil winding and the insulating layer.
Next, a process of manufacturing a pot core coil will be described below
with reference to FIGS. 11(a)-11(g) show plan views of a pot core coil,
and FIGS. 12(a)-12(g) show sectional side views of the same. In the
process step of FIGS. 11(a) and 12(a), a magnetic material (which is,
preferably, a ferromagnetic material such as ferrite or permalloy) is
attached by pattern plating on an insulating base (substrate) 35 formed of
glass or ceramic to form a pot core bottom portion 33a. At this time, a
gap 33d for leading out the coil winding 31 is also formed. In process
step of FIGS. 11(b) and 12(b), a photoresist insulating layer 34a is
formed into a doughnut-like shape, and baking is thereafter effected. In a
process step of FIGS. 11(c) and 12(c), a spiral electrically conductive
pattern, e.g., a copper coil, is formed by pattern plating to form the
coil winding 31 and pads 32 at the two ends thereof. The coil winding 31
is formed by the same manufacturing method as that described above with
reference to FIGS. 5(a)-5(g). In the process step of FIGS. 11(d) and
12(d), a photoresist insulating layer 34b is formed into a doughnut-like
shape as illustrated as in FIGS. 11(b) and 12(b), followed by baking. A
inner end of the coil winding 31, however, is exposed on the insulating
layer 34b. In the process step of FIGS. 11(e) and 12(e), a lead 31a
extending from the inner end of the coil winding 31 and another pad 32 are
formed by pattern plating as in the step of FIGS. 11(c) and 12(c). In the
process step of FIGS. 11(f) and 12(f), a ferromagnetic material is
attached to a central portion and an outer peripheral portion by pattern
plating as in the step of FIGS. 11(a) and 12(a) to form a central pot core
portion 33b and an outer peripheral pot core portion 33c having a gap for
leading out the coil winding 31. Further, if a shielding wall 39 is
formed, an electrically conductive material such as aluminum is, for
example, deposited or sputtered to form the shielding wall 39 in the
process step of FIGS. 11(g) and 12(g). One or a plurality of pot core
coils 30 and shielding walls 39 are fully covered with an insulating
material by molding to be used as, for example, the thin-film coil module
15 shown in FIG. 1. In the above-described embodiment, the coil winding in
each pot core coil is formed in a one-stage spiral pattern. Alternatively,
multi-stage laminated spiral patterns (refer to FIG. 4) may be used. In
such a case, the steps of FIGS. 11(b) to 11(d) and 12(b) to 12(d), for
example, of the manufacturing process may be repeated a plurality of
times, the ends of coil windings being connected to form one continuous
winding.
If pot core coils are formed based on the thin-film technology as described
above, the thickness and the overall size of each pot core coil and,
hence, those of the thin-film coil module in which a plurality of such pot
core coils are housed can be reduced.
Because the pot core coil can be formed so as to be reduced in thickness
and size, it can also be designed for an IC microcomputer card (a smart
card) having a thickness of 0.76 mm in accordance with the ISO
specification, and IC microcomputer cards can easily be designed as a
non-contact type.
In the above-described embodiment, parallel 8-bit data transfer is
performed. However, the present invention is not limited to this. Parallel
transmission of N-bit data (N: positive integer) can be effected by
providing N data transmitting/receiving coils while considering the mount
area. A volatile RAM (random access memory) requiring a data maintenance
battery 6 or a non-volatile ROM (read only memory) requiring no data
maintenance battery 6 may be selected as the memory IC 5 to achieve the
same performance.
As described above, in the electromagnetic induction non-contact type IC
card of the present invention, thin film coils reduced in thickness and
overall size are formed, and N units of these coils are arranged to effect
N-bit (8-bit, in the described embodiment) parallel data transfer. This IC
card can therefore transfer data at a speed higher than that of the
conventional serial data transfer system. The pot core structure of each
thin film coil ensures that data transfer can be performed with improved
reliability even when the terminal unit and the IC card are incorrectly
positioned. Further, the provision of the shielding walls between adjacent
thin-film coils of the terminal or the IC card enables prevention of
interference between the adjacent coils, enables the coils to be mounted
by being closely arranged with small spacings, and thereby reduces the
area occupied by the coil section.
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