Semiconductor device

Details Semiconductor device Semiconductor device

2000-04-25

2001-05-29

Clark, Sheila V. (Department: 2815)

Active solid-state devices (e.g., transistors, solid-state diode

Housing or package

Smart card package

C257S723000, C257S724000

Reexamination Certificate

active

06239483

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a semiconductor device; more specifically, the present invention relates to a semiconductor device particularly preferable for use in extremely thin, inexpensive IC cards with high bending toughness, wireless multi-chip modules and mobile communication terminals.
BACKGROUND ART
As to IC cards, a card with the cross structure shown in
FIG. 20
is described in “Data Carrier, II”, page 137 to 194, Japan Industrial Press Corporation, issued Mar. 15, 1991.
In the card, as apparently shown in
FIG. 20
, thick condenser chip
411
mounted on board
410
is connected through bonding wire
416
to printed wiring board
412
and is then molded with resin
415
, and the resulting whole structure is incorporated into center core
413
, of which the top and bottom are covered with over-sheet
409
,
414
.
Furthermore, Japanese Patent Laid-open No. Hei 3-87299 proposes an IC card comprising a thin-thickness chip.
In the card of such conventional type having the structure shown in
FIG. 20
, elements such as condenser chip
411
are so thick that these elements are weak to stress of bending and are therefore readily broken, disadvantageously.
As to the card proposed by the Japanese Patent Laid-open No. Hei 3-87299, as shown in
FIG. 8
, the surface and back face of the condenser chip
41
bonded to the thick board
42
are stressed by a stretch or press operation if the board is bent, so that larger stress is applied to the condenser chip
41
(of a thickness of 200 &mgr;m). Therefore, the connection between metallized pattern
43
and the condenser chip
41
connected to the pattern
43
fails; or the condenser chip
41
weak to mechanical stress because of the thin-thickness is readily broken through the stress. Hence, the reliability thereof is particularly low.
A card of such conventional structure using condenser chip
41
is fabricated by attaching condenser chip
41
onto thin card
42
readily bendable, followed by wire bonding, and therefore, the card is at low reliability because condenser chip
41
is readily broken. Additionally, the number of the process steps for mounting is so large. Accordingly, it has been difficult to reduce the production cost.
DISCLOSURE OF THE INVENTION
It is an object of the present invention to overcome the problems of the prior art and provide a highly reliable, inexpensive semiconductor device strong to bending, particularly a semiconductor device of a thin-thickness type, having functions as IC card, multi-chip module or mobile communication terminal.
So as to attain the object, in accordance with the present invention, a thin-thickness device or integrated circuit comprising a condenser is mounted on a flexible card board of the same size as that of a card, and the thickness of the condenser, an integrated circuit or a coil and the thickness of the card provided with the condenser, the integrated circuit or the coil are individually fixed at given dimensions.
More specifically, the thickness of the integrated circuit, the condenser or the coil is defined as 110 &mgr;m or less, provided that the lower limits of the thickness of the card and the condenser are 50 &mgr;m and 0.1 &mgr;m, respectively.
By fixing the integrated circuit, the condenser or the coil at such thin thickness, the integrated circuit, the condenser or the coil gets strong to stress of bending. When these are connected to a thin board such as IC card with a flexible adhesive, a highly reliable IC card strong to stress of bending can be produced.
Preferably, the thickness of a semiconductor device, namely the card on completion, is 760 &mgr;m or less when the thickness of the integrated circuit, the condenser or the coil is 110 &mgr;m or less.
Preferably, the thickness of a semiconductor device, namely the card on completion, is 500 &mgr;m or less, when the thickness of the integrated circuit, the condenser or the coil is 19 &mgr;m or less. Additionally, the thickness of a semiconductor device, namely the card on completion, is 250 &mgr;m or less, when the thickness of the integrated circuit, the condenser or the coil is 4 &mgr;m or less.
Because the thin-thickness condenser attached on the card is thin, the board and the condenser are now possibly wired by means of a conductive paste. Accordingly, compared with conventional wire bonding by means of gold wire, a flat IC card of thin thickness can be produced at a low material cost and at a large scale.
The structure comprising such a thin-thickness condenser can be applied to the fabrication of not only IC card but also other devices of similar shapes and multi-chip mounting.
On the cross section of the card bent, stretch forces are induced on the surface of the curved board, while shrink forces are induced on the back face. Because no shrinkage occurs then at the central part of the cross section of the card under less stress, the stress to be loaded onto a thin-thickness condenser chip can be released, if the condenser chip is placed on the part.
It is needless to say that the condenser chip of a thin thickness is better. Extremely preferable outcome can be gained if the thickness is 110 &mgr;m or less. If the card is thick, however, the stiffness of the card enlarges the critical curvature ratio. Hence, the card is scarcely bent. Thus, the condenser chip may satisfactorily be thick at some extent.
If the card is of a thin thickness, on contrast, the card is readily bent. So as to release the stress of the condenser chip, the condenser chip should be thin. For preparing a condenser of a thin thickness, a thinner thickness of the condenser requires more precise apparatuses for fabricating such condenser. Thus, as to how thin the condenser should be fabricated, it should be assessed from both the standpoints of economical efficiency and procurement of reliability.
A given correlation in thickness between the card and the condenser chip is present; by fixing both the card and the condenser chip at the aforementioned thickness, various cards strong to bending and highly reliable can be produced at a low cost. It is needless to say that this is the case with the thickness of the coil and the integrated circuit placed internally in the card, other than the thickness of the condenser.
The lowest thickness limits of the semiconductor device, namely the card on completion, and the condenser, are 50 &mgr;m and 0.1 &mgr;m, respectively. If the card thickness is smaller than 50 &mgr;m, the flexibility of the card is distinctively reduced which causes difficulty in putting the card for practical use; and it is also difficult to fabricate a condenser of a thickness of 0.1 &mgr;m.


REFERENCES:
patent: 5598032 (1997-01-01), Fidalgo
patent: 5909050 (1999-01-01), Furey et al.
patent: 5969951 (1999-10-01), Fisher et al.
patent: 5986341 (1999-11-01), Usamie et al.
patent: 5996897 (1999-12-01), Prancz

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