Active solid-state devices (e.g. – transistors – solid-state diode – Housing or package – Smart card package
Reexamination Certificate
1999-03-10
2001-03-27
Williams, Alexander O. (Department: 2811)
Active solid-state devices (e.g., transistors, solid-state diode
Housing or package
Smart card package
C257S673000, C257S680000, C257S774000, C257S792000, C257S730000, C235S492000, C235S487000, C361S761000
Reexamination Certificate
active
06208019
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a card-type semiconductor device such as an IC card.
2. Description of the Related Art
Card-type semiconductor devices with a semiconductor chip built in, called IC card, are being developed actively these years.
An example of the structure of such a card-type semiconductor device is shown in FIG.
5
. Reference numeral
21
denotes a wiring substrate, which has a desired wiring layer formed on one side (the upper face in the drawing) of an insulating substrate and a wiring layer to be an external connection terminal on the other side (the lower face in the drawing). Both wiring layers are electrically connected through conductive holes (not shown). A semiconductor chip
22
is mounted onto the upper face of the wiring substrate
21
with an insulating adhesive agent (mounting agent)
23
, and its electrode pads are connected to the wiring layer of the wiring substrate
21
by bonding wires
24
such as gold wires. And a mold resin layer
25
of epoxy resin layer or the like is formed on the exterior of the wire-bonded portion. The resin-molded chip-mounted section is fitted into a recess of an exterior sheet
26
made of polyvinyl chloride resin, polyester resin or the like, and the wiring layer on the lower face of the wiring substrate
21
is exposed as external connection terminal.
Such a conventional card-type semiconductor device, however, could not be fabricated to have a satisfactory small thinness because the semiconductor chip
22
has a large thickness of 350 to 450 &mgr;m and defines an overall thickness of the device.
The IC card is required to have a strength enough to resist against an impact, bending, twisting, etc. due to an external force. But the card-type semiconductor device, which has the above-described thick semiconductor chip
22
mounted, could not meet the requirement in terms of a bending strength and the like.
SUMMARY OF THE INVENTION
The present invention was achieved to remedy the problems described above. And it is an object of the invention to provide a card-type semiconductor device, which is thin with a sufficient strength against bending, twisting and the like and suitable as an IC card.
This invention is disclosed in Japanese Patent Application No. 10-063135 filed on Mar. 13, 1998, and the entire disclosure thereof is incorporated herein by reference.
A first aspect of the present invention is a card-type semiconductor device, which comprises:
a film insulating substrate having a device hole; a wiring layer formed on at least one main face of the insulating substrate and a group of leads whose one end is connected to the wiring layer and the other end is protruded into the device hole; a semiconductor element which has a thickness smaller than the insulating substrate with its each electrode pad electrically connected to respective leading ends of the group of leads; and
an exterior layer which is laminated on both faces of the insulating substrate,
wherein the semiconductor element is fully embedded into the device hole of the insulating substrate.
A second aspect of the present invention is a card-type semiconductor device, which comprises a semiconductor element and an enclosure portion made of an insulating resin for fully covering the periphery of the semiconductor element without remaining any gap; wherein
the semiconductor element has a flexible bending radius of 15 to 40 mm, and the enclosure portion has a bending radius of less than 15 mm; and the semiconductor device as a whole has a flexible bending radius of 15 to 40 mm.
According to the invention, the film insulating substrate can be an insulating resin film such as a polyimide resin film (trade name: UPILEX manufactured by Ube Industries, Ltd.). The film preferably has a thickness of 75 to 125 &mgr;m. It is also preferable that the device hole formed in the insulating resin film has such a size and a plane shape to correspond with those of the semiconductor element to be described afterward, so that the semiconductor element is embedded with a sufficient allowance around it.
The wiring layer formed on at least one main face of the film insulating substrate and the group of leads whose one end connected to the wiring layer are formed of Cu, a Cu-based alloy or the like by deposition patterning of such metal on the insulating substrate or photo-etching of a Cu foil or the like, which is directly laminated on the insulating substrate or with an adhesive agent layer such as an epoxy-based layer or the like between them.
In the card-type semiconductor device according to the invention, the end (leading end) of the group of leads protruded into the device hole is bonded (inner lead bonding) to the electrode pads, made of aluminum or the like, of the semiconductor element by heating and pressing. It is desirable that the leading ends of the leads are coated with a gold, tin or solder layer by plating or the like in order to improve their bonding strength. The electrode pads of the semiconductor element may be bonded to the leads through the gold bumps formed on the electrode pads. The bonding strength can be further improved by bonding the leads, which are plated with gold, tin or the like, to the gold bumps formed on the electrode pads.
For the bonding portions between the leads and the electrode pads of the semiconductor element, it is preferable that the leading ends of the leads have a width smaller than that of the electrode pads or that of the gold bumps formed on the electrode pads. By fabricating as described above, a protective film (passivation film) of the semiconductor element can be effectively prevented from being damaged through a contact with the leading ends of leads.
The invention can use an insulating resin film having flexibility, such as a polyester resin film, as the exterior layer. This insulating resin film is laminated on both faces of the film substrate (wiring film), on which the above-described wiring layer or the like is formed, by thermal fusion bonding for example. The film is not limited to have a particular thickness but preferably has a thickness of about 50 &mgr;m (25 to 75 &mgr;m) so to protect as an enclosure its inside and also to contribute in making the device thinner as a whole.
According to the present invention, the semiconductor element is preferably a thin semiconductor element having each side of 3 to 6 mm and a thickness of 30 to 70 &mgr;m which is thinner than the film insulating substrate so that it can be fully embedded in the device hole of the above-described film insulating substrate.
By using the semiconductor element having a thickness in the above-described range (30 to 70 &mgr;m), the card-type semiconductor device having a bending radius to allow repeated bending (hereinafter referred to as the bending radius) of 15 to 40 mm can be realized.
Strength against bending which is required for the card-type semiconductor device such as the IC card is not standardized yet. But it is expected that the card-type semiconductor device has such a very high bending strength corresponding to that of the conventional Japanese magnetic telephone card that its appearance and function are not affected even after repeatedly applying strong bending (e.g., a bending radius of about 166 mm on the long side) for about 1000 times.
The semiconductor element having a thickness of 30 to 70 &mgr;m has a bending radius of about 17 to 33 mm though it is slightly variable depending on a grinding direction and a very high bending strength as large as 7 times or more as compared with a conventionally used semiconductor element having a thickness of 350 to 450 &mgr;m (a bending radius of about 200 mm). Thus, a necessary and sufficient bending strength for the IC card can be realized for the first time by using the semiconductor element having a thickness of 30 to 70 &mgr;m. The semiconductor element having a thickness of less than 30 &mgr;m is not processed with ease, the yield of its manufacture is not good, and its strength against bending and the like is low.
According t
Tanaka Kazuyasu
Tane Yasuo
Kabushiki Kaisha Toshiba
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Williams Alexander O.
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