Injection molding method for board for IC card

A plate for an IC card having recesses for mounting components is formed by injection molding of plastics. First, a mold for forming recesses for mounting components is formed to have a slide core. After molten resin is filled in a cavity, the slide core is forced to penetrate into the cavity. Thus, the molten resin is removed by the slide core so as to form the recesses and walls. Because the resin has been filled beforehand, even if the wall is thin, the filling process is carried out normally, and the walls can be formed without increasing an injection pressure.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a manufacturing method of a board for an 
IC card for mounting an integrated circuit chip or the like, and a board 
manufactured by the method. 
2. Description of the Prior Art 
An IC (integrated circuit) card comprises a board on which electronics 
components such as an IC chip of a memory device or a microprocessor are 
mounted. A board provided for producing an IC card may have one or more 
recesses on a plane thereof for mounting components. A board may be 
produced by injection molding. For example, after the components are fixed 
to the recess, resin is filled into the recesses to seal the components. 
Such a board is described for example in Japanese Patent laid open 
Publication 62-298143/1987. In the production of the board, a plastic 
plate of a prescribed thickness is punched with a press to produce a card 
blank. Then, recesses for mounting components are cut in the blank 
precisely by a numerical control machine, to provide the board. However, 
the board produced as described above has a high production cost, and it 
is hard to reduce the cost even by mass production. 
If the board is formed with injection molding with a plastics material at 
the same time as the recesses for mounting the components as an integral 
body, the production cost can be reduced largely. However, the thickness 
of the board is about 0.8 mm. Therefore, if the recesses are formed at the 
same time, the thickness at the bottom wall of the recesses becomes very 
thin, or the bottom walls cannot be formed surely. Therefore, cutting is 
adopted at present than injection molding. 
However, if cutting is adopted, when an integrated circuit chip is fitted 
to the recess for adhesion, a portion of the recess to be adhered has a 
relatively smooth surface due to precise cutting. Therefore, when an IC 
card is subjected to a strong shock or when a card is bent, a part of 
adhesion plane is liable to be separated. In order to prevent the 
separation, the walls may be remained to have rough surfaces to increase 
adhesion strength. However, in such a case, precision along depth 
direction is liable to have a scattering, and precision of positions of 
connection terminals of integrated circuit chips cannot be maintained. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide a manufacturing method of 
a board for an IC card, the board having a recess with a film-like wall at 
the bottom of the recess, the method being able to mass-produce the board 
to reduce a production a cost to a large degree. 
Another object of the present invention is to provide a manufacturing 
method of a board for an IC card which can form a film-like wall surely 
without increasing injection pressure while improving mechanical strength 
and heat resistance. 
A third object of the present invention is to provide a manufacturing 
method of a board for an IC card which can form the board without strain 
due to forming. 
A fourth object of the present invention is to provide a manufacturing 
method of a board for an IC card which can remove a gate during the 
forming so that removal of the gate after separating the mold is not 
needed to reduce a production cost of the board. 
A fifth object of the present invention is to provide a board for an IC 
card, the board itself or a bottom wall thereof having a sufficient 
mechanical strength to improve endurance. 
A sixth object of the present invention is to provide a board for an IC 
card having no strain due to forming, no deformation due to heat and 
superior on heat resistance. 
A seventh object of the present invention is to provide a board for an IC 
card wherein a component such as an IC chip can be adhered and fixed 
strongly to a recess so that the component is not removed when an abnormal 
strength of bending and shock exerts to the board or the endurance is 
good. 
In one aspect of the invention, a board for an IC card is manufactured. The 
board has a recess for receiving a component such as an integrated circuit 
chip in one of the planes of the board, and the recess has a film-like 
wall integrated as one body with the board at an inner bottom of the 
recess. In the method, (a) a slide core is provided in a mold for 
injection molding for forming the board, the slide core 15 facing a cavity 
12 in the mold. (b) Then, molten resin is injected into the cavity, and 
the slide core is moved into the cavity to a forming position before the 
resin began to solidify. Thus, the recess and the film-like wall can be 
formed at the same time surely. 
In a second aspect of the invention, a board for an IC card, comprises a 
recess for receiving a component such as an integrated circuit chip in one 
of the planes of the board, the recess having a film-like wall integrated 
as one body with the board at an inner bottom of the recess. The board is 
made of a plastic material by using injection molding, and the recess and 
the film-like wall are made with a slide core projecting into a cavity 
with injected molten resin. 
In a third aspect of the invention, a board for an IC card comprises a 
recess for receiving and adhering a component such as an integrated 
circuit chip in one of the planes of the board produced by injection 
molding, and the recess has a film-like wall integrated as one body with 
the board at an inner bottom of the recess. The board comprises an 
adhesion wall for adhering the component for fixing it, the adhesion wall 
having an uneven surface. 
It is an advantage of the invention that a film-like wall at the bottom of 
the recess can be formed surely in a board for an IC card. 
It is another advantage of the invention is that a board for an IC card can 
be mass-produced.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to the drawings, wherein like reference characters designate 
like or corresponding parts throughout the views, embodiments of the 
invention are explained. A board for an IC card has a recess for receiving 
a component such as an integrated circuit chip in one of the planes of the 
board, and the recess has a film-like wall integrated as one body with the 
board provided at the bottom of the recess. The board is made of a 
plastics material by injection molding. 
In injection molding where resin is filled into a narrow cavity in a mold, 
it is proposed that fluidity of molten resin is improved or injection 
pressure is increased (refer to Japanese Patent laid open Publication 
62-202373/1987). However, if this technique is applied to production of a 
board for an IC card, the inventors found that the bottom wall at the 
recesses for mounting components cannot be formed surely. If injection 
pressure is increased, though the bottom wall can be formed, weld lines 
are formed at the surfaces thereof. Such a bottom wall do not have a 
sufficient mechanical strength, and when an external force is applied to 
the bottom wall, the component mounted to the recess cannot be protected 
enough. Further, an increase in injection pressure also increases wear of 
an injection mold. 
FIG. 1 shows a board of an IC card schematically, and FIG. 2 is a sectional 
view along A--A line in FIG. 1. The board 1 has a square shape, and it has 
a recess 3 on a plane thereof for mounting a component 2 such as an 
integrated circuit chip at left or right side thereof at about the center. 
The recess 3 comprises a first square recess 4 for mounting a base 2a (not 
shown) of the component 2. Further, a second hole 5 smaller than the first 
one 4 is provided at the bottom of the first one 4 like a terrace 
structure. The inner bottom of the recess 3 or of the second hole 5 
comprises a bottom wall 6 which is formed as an integral body continuous 
to a main body of the board 1 with injection molding using a plastics 
material. The bottom wall 6 is thin like a film. Further in FIGS. 2 and 6, 
the sizes of the recess 3 is exaggerated along vertical direction. 
The board 1 has a size of a longer side of 85.6 mm, a shorter side of 54 mm 
and a thickness T of 0.80 mm. Longer and shorter sides of the first hole 5 
are 12 mm and 10.6 mm, respectively. A thickness T1 of the bottom wall 6 
is 0.22 mm. A resin material for the board 1 may be an ordinary resin for 
injection molding such as vinyl chloride, vinyl acetate or ABS. 
FIGS. 3A and 3B show a mold for injection molding for producing the board 
1. The mold is made of a fixed mold 10 and a movable mold 11. A cavity 12 
or a space for forming is formed between contact planes of the mold. A 
spool (not shown) for supplying molten resin under pressure is provided 
for the fixed mold 10, and a runner 13 connects the spool with each cavity 
12 at a narrow gate space 14. Molten resin is injected through the runner 
13 and the gate 14. As shown in FIG. 1, the gate space 14 is provided at a 
longer side of the board near the recess 3 for mounting a component, by 
avoiding longer and shorter sides S1 and S2 of the IC card. 
A slide core 15 is provided at the movable mold 11 for forming the recess 4 
of the board 1. The slide core 15 comprises a circular pin, and it has a 
top forming section 15a having a shape in correspondence to the recess 3 
for mounting. The slide core 15 slides perpendicularly to contact planes 
of a pair of the two molds 10 and 11 to reciprocate between a retracted 
position where almost all the forming section 15a moves out of the cavity 
12 and a forming position where the forming section 15a moves into the 
cavity 12. When the molds and 11 are dissociated after injection, the 
slide core 15 moves across the forming position. 
Further, a gate pin 16 is provided to connect or disconnect the gate space 
14 to each cavity 12. A partition wall 16a is provided at a top portion of 
the gate pin 16, and it can move to reciprocate between a first position 
where the cavity 12 is blocked at the gate space 14 and a second position 
where the partition wall 16a is withdrawn from the gate space 14. 
The board 1 is produced with use of the molds 10, 11 explained above 
according to processes described in FIGS. 4A-4E. 
(1) First, the slide core 15 and the gate pin 16 are located at the 
retracted positions, and the molds 10 and 11 are fixed (FIG. 4A). The top 
portion 15b of the slide core 15 protrudes a little from an opening of a 
core hole 17 (FIG. 1) connecting to the cavity 12 (refer to a state shown 
as a phantom line in FIG. 3A). Thus, a sufficient space can be provided 
between the top portion 15b and an opposing wall of the cavity 12, so that 
molten resin can flow with no difficulty to a portion for forming the 
recess 3. 
(2) Next, molten resin is injected through the runner 13 and the gate space 
14 into the cavity 12. Because resin flows smoothly into the cavity 12, it 
is prevented for a flow line around the slide core 15 to be generated in 
the cavity 12. This means that a strain due to deformation does not happen 
within the cavity 12. The slide core 15 in the retracted position may 
project a little into the cavity 12 as long as it does not hinder the flow 
or the resin. A removed amount of the resin may be large as long as no fin 
is generated at planes for combining the molds 10 and 11. 
After the resin fills the cavity 12, the slide core 15 is moved into the 
forming position to push aside the resin from an occupied area (FIG. 4B). 
Because a bottom wall 6 is formed by moving the slide core 15 into the 
forming position after resin is filled, insufficient injection of resin or 
defective portions such as weld lines do not occur. In other words, the 
bottom wall can be formed surely by injection molding. In this step, the 
board 1 having the bottom wall 6 can be formed surely without increasing 
injection pressure. 
The timing of the movement of the slide core 15 to the forming position may 
be at any point after the molten resin is injected and until the molten 
resin solidifies. However, the earliest timing is a time when the molten 
resin arrives to a portion for forming the film-like resin 6. If the slide 
core 15 is located to the forming position before the molten resin arrives 
to a portion for forming the bottom wall 6, it is necessary to fill the 
molten resin at a higher injection pressure. An appropriate timing is 
after the molten resin fills the cavity and until the injection pressure 
is kept constant. 
(3) Next, while the injection pressure is kept the same, the gate pin 16 is 
moved into the gate space 14 to seal the cavity 12 (FIG. 4C). Thus, the 
gate 14 is cut off from the resin in the cavity 12 during the 
manufacturing process. The gate space 14 is formed at a periphery adjacent 
to the recess 3 because molten resin flows surely to portions for forming 
the recess 3 and the bottom wall 6, especially to prevent defectives due 
to forming at the bottom wall 6. It is not needed to remove the gate space 
14 after separating the molds 10, 11. 
(4) Next, in the state described above, the molds 10 and 11 are cooled to 
solidify the resin filled in the cavity 12. After a prescribed 
solidification time elapses, the slide core 15 and the gate pin 16 are 
moved back to the retracted positions thereof (FIG. 4D). 
(5) Next, the movable mold 11 is located at a position to be separated from 
the fixed mold 12, and the molds are opened or the movable mold 10 is 
removed. In this state, the slide core 15 is moved again into the cavity 
12 to separate the board 1 from the movable mold 11 to be taken out from 
the machine (FIG. 4E). Thus, it can be prevented to form a remain of the 
knockout pin at a wall of the board 1. The runner 13 is separated from a 
knockout pin used exclusively for the separation. 
By repeating the above-mentioned processes, boards 1 having bottom walls 6 
shown in FIGS. 1 and 2 can be mass-produced. 
Because the slide core 15 is moved after resin is injected, the board 1 can 
be formed without a strain due to forming. Therefore, the board 1 has a 
superior mechanical strength as a whole, and it can also prevent bending 
due to heat. That is, the board 1 had good endurance. 
As shown in FIG. 6, a component 2 such as an IC chip is mounted in the 
recess 3 of the board 1 produced as explained above, with connection 
terminals 8 thereof exposed above a plane of the board 1. As shown in FIG. 
5, the number of the connection terminals 8 is eight in this example. 
Next, the component 2 is fixed with an adhesive to an adhesion wall 7 of 
the first hole 4. The adhesion wall 7 means an area at the bottom of the 
first hole 4 except the area where the second hole 5 is formed. The 
adhesive is coated beforehand only on the adhesion wall 7. As shown in 
FIG. 7, the adhesion wall 7 of the first hole 4 is formed to have an 
uneven plane such as a rough surface or a plane having a shape of wave, 
protrusion, saw-teeth or comb in order to fix the component 2 strongly to 
the recess 3. By coating an appropriate amount of adhesive to the adhesion 
wall 7, a base 2a of the component 2 is adhered and fixed to the adhesion 
wall 7. Because the adhesion wall 7 is uneven, adhesion strength increases 
due to a surface area thereof. Further, the precision of the position 
along thickness direction of the component 2 does not scatter because the 
uneven surface for adhesion has generally the same depth. The uneven 
surface may be formed as the adhesion wall 7 on injection molding. 
Then, printing is performed on the front and back planes of the board 1, 
and a protection film is laminated on the board 1 to complete an IC card. 
If necessary, as shown in FIG. 1, a magnetic stripe 18 is formed at the 
back or front side of the board 1 to record magnetic signals. 
As shown in FIG. 2 with a phantom line, in the board 1 formed with 
injection molding, the bottom wall 6 of the recess 3 including the bottom 
wall 6 tends to expand toward the outside. Measurements of an expansion 
amount .delta. show that a maximum thereof is 0.038 mm around the center 
of the wall 6 and a minimum thereof is 0.007 mm around the peripheral 
thereof. This means that the expansion amount .beta. is suppressed to a 
negligible amount by using the above-mentioned manufacturing method which 
uses the slide core 15 moving into the cavity 12 filled with molten resin 
to form the bottom wall 6. 
FIGS. 8A-8C show modified examples of the recess for mounting. In FIG. 8A, 
a recess 103 for mounting a component is extended to a side 120 of a board 
101 for an IC card where the gate space 14 is provided, so that a first 
hole 104 of the recess 103 is open both to the side of the board 101 and 
to the peripheral. Further, a second hole 105 is formed at the bottom of 
the first hole 104 leaving an adhesion wall 107. In FIG. 8B, a recess 203 
is formed like a terrace so as to occupy one of the four corners of a 
board 201 for an IC card. Further, a second hole 205 is formed at the 
bottom of the first hole 204 leaving an adhesion wall 207. In FIG. 8C, a 
recess 303 is formed to occupy a whole shorter side of a board 301 
including side S2, and a first hole 304 is formed at the terrace plane. A 
plurality of second holes 305 is formed at the bottom of the first hole 
304 leaving an adhesion wall 307, in contrast to the second hole 105 and 
205 shown in FIGS. 8A and 8B having similar shapes as the first one. 
The first and second holes 4, 5 may have any form such as circle, ellipse 
or triangle beside square. The second hole 5 may have a shape different 
from that of the first one 4 according to a shape of a component 2 to be 
mounted. Though the recess 3 comprises the rectangular first and second 
holes 4, 5 in the above-mentioned embodiments, the recess 3 needs not to 
have such a structure. For example, the second hole 5 may be omitted and 
the bottom wall of the first hole 4 is made as a bottom wall 6. Further, 
the shape of the recesses may be changed to a truncated cone, a truncated 
pyramid or the like. 
The size of the board 1 can be selected in a range of a side along the 
longitudinal direction from 84.00 to 86.00 mm, a side perpendicular to the 
longitudinal direction from 53.00 to 55.00 mm and a thickness T1 from 0.05 
mm to 0.5 mm. If the thickness T1 is less than 0.05 mm, it becomes harder 
to form the bottom wall 6 surely even by using the above-mentioned 
manufacturing method. On the other hand, if the thickness T1 increases 
above 0.5 mm, the bottom wall 6 can be formed without moving the slide 
core 15, and the fluidity of the resin is not damaged even if a protrusion 
wall in correspondence to the slide core 15 is located at the forming 
position before filling the molten resin. 
In the embodiment, it is expected to change the area of the bottom wall 6 
in a wide range between 40.00-1,200.00 mm.sup.2. This complies with a case 
where a plurality of IC chips are mounted or components 2 such as a film 
cell, a display device and/or input/output terminals, in the recesses as 
shown in FIGS. 8A-8C. 
The board 1 can be modified partly as shown in FIG. 9 where two narrow ribs 
20 protrude to the recess 3 at inner walls of a first hole 4' at each 
shorter side thereof. By using the ribs 20, an IC chip 2 can be mounted or 
fixed temporarily by pressing it in the first hole 4'. When an IC chip 2 
is fixed by the ribs 20 temporarily as explained above so as not to be 
dropped from the recess 5, it can be prevented for the IC chip 2 to be 
removed under inertia shock such as vibrations, start or stop of a 
carrier. The IC chip 2 is fixed by filling an adhesive between an adhesion 
wall 7 of the first hole 4' and the IC chip 2. The positions and the 
number of the ribs 20 can be changed so as to be arranged within the 
recess 3, and the shape and the size thereof can also be adapted according 
to conditions. 
In a board 1 shown in FIG. 10, the peripheral 1a at the front side has 
round corners 1a. A mold for injection molding is formed to have partial 
arcs for the round corners 1a. Because the round corners 1a can be formed 
on injection molding, it can be produced at a low cost. The board 1 having 
round corners is hard to be caught when inserted to or removed from a card 
reader, or malfunctions such as errors on loading or injection occur 
hardly. The round corners 1a can also be flat small slant planes formed at 
edges of the board. It may also be formed only at a pair of longer or 
shorter sides among the four sides. 
As explained above, injection molding is used to manufacture the board for 
an IC card. Therefore, various structures can be added at the outer planes 
of the board. For example, in a structure shown in FIG. 11A, a knob 521 is 
provided at one of the surfaces of the board 501, and a safeguard 521a 
having continuous grooves and ridges for preventing sliding can be formed 
as an integral body with a main body of the board 501. In a structure 
shown in FIG. 11B, a frame 622 is formed along the peripheral of a board 
601 for an IC card, and a wall plane surrounded by the frame 622 is 
depressed as an adhesion plane 624 for adhering a protection film 623. In 
a structure shown in FIG. 11C, a plane wall of the board 701 has a 
depressed portion 725 for embedding a mark 726 of a company, an emblem for 
displaying a grade of the card or the like. Though not shown in detail, in 
these examples, a component 502, 602, 702 such as an IC chip is fixed to a 
recess 503, 603, 703 (not shown) having a structure similar to the 
above-mentioned recesses. 
The board for an IC card is not needed to be a square. For example, FIG. 12 
shows a board 801 having a shape of a telephone card. The board 801 has a 
slant side 809 besides shorter and longer S1 and S2. In this example, the 
board 801 has a size of a longer side of 80.00-15.00 mm, a shorter side of 
50.00-10.00 mm and a thickness T of 0.5-0.9 mm. A ratio of a thickness T1 
of a bottom wall 806 of a recess 803 to an area of the board 801 is set to 
be from 1/(8.5*10.sup.4)-1/(3.0*10.sup.2). 
The recess 3 for mounting a component does not necessarily have a terrace 
structure. The second hole 5 may be omitted as shown in FIG. 13. In this 
case, a hole having a bottom wall is formed, and a part of the inner 
surface of the hole is used for adhesion of a component. For example, the 
recess 3 may be formed as an upside-down truncated pyramid or cone, and 
the slopes at the side of the opening is formed as an uneven surface as an 
adhesion wall 7. The inner wall of the recess 4 may be formed as a 
continuous ridge plane, to be used as an adhesion plane 7. The uneven 
plane of the adhesion wall 7 may also be formed as grooves and ridges 
arranged as a lattice, parallel grooves or ridges, or independent pits or 
projections. 
The board for IC card shown in FIG. 13 has a shape of character T for use 
as a key for locking a door. The board 901 has a length S3 along a shorter 
side of 30-60 mm and a length S4 along a longer side of 30-60 mm. A recess 
903 having a bottom wall 906 is provided near an end of the shorter side. 
Although the present invention has been fully described in connection with 
the preferred embodiments thereof with reference to the accompanying 
drawings, it is to be noted that various changes and modifications are 
apparent to those skilled in the art. Such changes and modifications are 
to be understood as included within the scope of the present invention as 
defined by the appended claims unless they depart therefrom.