Registers – Records – Laminated
Reexamination Certificate
1999-02-09
2001-01-30
Le, Thien M. (Department: 2876)
Registers
Records
Laminated
C235S492000
Reexamination Certificate
active
06179210
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to microelectronic assemblies, and more particularly, to dual mode smartcards and to punch out patterns in the hot melt tape used in such dual mode smartcards.
BACKGROUND OF THE INVENTION
Dual mode smartcards typically contain an antenna embedded in a smartcard body and a module encapsulating a microprocessor coupled to a substrate surface, the latter provided with external leads for contacted smartcard operation to a card reader.
The smartcard body and module are matedly attached using a conductive adhesive. The conductive adhesive is typically deposited in each of two vias buried within the smartcard body. The vias are formed by milling the smartcard body to a depth sufficient to expose associated antenna leads buried in the smartcard body. After the vias (or antennas exposing cavities) are formed, they are filled with the conductive adhesive and the module properly aligned in mated fashion on top of the smartcard body, resulting in an electrical connection between the antenna and module by way of the conductive adhesive.
A critical element of smartcard manufacture is that dispensed volumes of conductive adhesive need to be precisely controlled in order not to overfill the vias. To date this has been inadequately achieved by using what is known as a non-conductive hot melt tape having a specific punch out pattern. The hot melt tape
10
includes three cut outs, an overmold receiving cavity (
11
) and two circular punch out holes
12
,
13
, as shown in FIG.
1
. Circular punch out holes
12
and
13
are substantially the diameter of corresponding vias on the smartcards, over which the hot melt tape is superimposed during smartcard assembly.
Before combining the top surface of the smartcard body to the bottom surface of the module, the hot melt tape
10
is first adhesively bonded to the bottom surface of the module. The punch out holes
12
and
13
are dimensioned to expose corresponding electrical contact areas on the bottom surface of the module. Once the hot melt tape is affixed to the module, both vias on the smartcard body are filled with the conductive adhesive. The module (with hot melt tape) are then brought together with the smartcard body. In an ideal situation, when filling the vias, only enough adhesive is provided as necessary to fill the punch out holes
12
,
13
sufficiently, and without overfill, so that contact is made between adhesive and the exposed electrical contact areas on the bottom surface of the module.
FIG. 2
shows the smartcard body facing surface of the hot melt tape with no overflow
14
having spread onto the surface area.
If overfill
14
′ does occur, and often times does occur, as shown in
FIG. 3
, it can lead to contamination of the hot melt tape around one or both vias and also result in insufficient adhesion of the module to the smartcard body. Insufficient adhesion around the via could result in a weak (or intermittent) electrical connection, particularly when the smartcard is bent—as expected to occur during normal use by its owner. Also, the overfill from adjacent connections could migrate towards each other and result in an electrical short, as shown by
14
″ in FIG.
4
.
Controlling the dispensed volume of viscous materials like conductive adhesive has always been very difficult. Several issues, such as changing viscosity as the material cures, differing viscosity within the same tube of material, and differing viscosity between lots of material are the cause of the dispensing inaccuracies.
It would be a great advance in the art of smartcard manufacture to be able to provide a solution to the problem of overflowing conductive adhesive.
REFERENCES:
patent: 4417413 (1983-11-01), Hoppe et al.
patent: 4463971 (1984-08-01), Hoppe et al.
patent: 4639585 (1987-01-01), Haghiri-Tehrani et al.
patent: 4764803 (1988-08-01), Ueda
patent: 4897534 (1990-01-01), Haghiri-Tehrani et al.
patent: 5027190 (1991-06-01), Haghiri-Tehrani et al.
patent: 5031026 (1991-07-01), Ueda
patent: 5055913 (1991-10-01), Haghiri-Tehrani
patent: 5208450 (1993-05-01), Uenishi et al.
patent: 5550402 (1996-08-01), Nicklaus
patent: 5554885 (1996-09-01), Yamasaki et al.
patent: 5834755 (1998-11-01), Haghiri-Tehrani et al.
patent: 5856662 (1999-01-01), Kohama et al.
Gore Kiron P.
Haas Kevin L.
Egan Wayne J.
Le Thien M.
Motorola Inc.
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