Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
1999-09-03
2001-02-20
Gandhi, Jayprakash N. (Department: 2841)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C361S767000, C361S760000, C361S809000, C257S679000, C235S492000
Reexamination Certificate
active
06191951
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The invention relates to a smart card module and a smart card including a smart card module.
Smart card modules usually include a carrier on which a semiconductor chip is bonded or fastened in some other way. The carrier may be a thin printed circuit board or a plastic sheet having a side remote from the chip on which an electrically conductive layer made of copper or the like is laminated. The layer is structured to form individual contact areas which can be tapped by a card reader. Instead of the laminated carrier sheet, the semiconductor chip can also be fitted to a metallic lead frame, with or without an intermediate carrier, into which the individual contact areas are stamped. The form and size of the contact areas usually depend on specific standard specifications such as, for example, ISO Standard 7816. In conventional smart card modules, electrical contact is made between the semiconductor chip and the contact areas with the aid of bonding wires which are routed from contact-making points of the semiconductor chip to terminal points of the contact areas. As an alternative, the semiconductor chip may be applied by using flip-chip technology.
In order to protect the chip and the connections to the contact areas, a layer of epoxy resin, thermosetting plastic or the like is applied over the chip and the connection points. The finished smart card module is finally implanted in a card carrier of a smart card.
Such smart card modules are disclosed, for example, in German Patent DE 44 24 396 C2, German Patent DE 195 32 755 C1, German Patent DE 26 59 573 C2, U.S. Pat. No. 4,803,542, as well as European Patent Application 0 071 311 A2.
Particularly the smart card module disclosed in German Patent DE 195 32 755 C1, from which the invention of the instant application proceeds, shows a metallic lead frame with a semiconductor chip mounted in flip-chip technology. The lead frame has a three-dimensional structure produced through etching.
German Patent DE 195 12 191 C1 describes specific materials for producing lead frames of smart card modules. Patent Abstracts of Japan Publication No. 06342794 A describes a semiconductor package in which a passivation layer partially covers an electrode surface between a chip surface and a housing.
The smart card modules constructed in the manner described above generally have a component height of at least 500 to 600 &mgr;m. It has not been possible to date to realize smaller component heights. Moreover, due to the relatively large component height of the smart card modules, the card carrier can only be very thin in the region of the module in order not to exceed the predetermined total thickness of the smart card. Sunken locations therefore appear on the card surface in the region of the smart card module.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a smart card module and a smart card including a smart card module, which overcome the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type, in which the smart card module can be produced in a simple and effective manner and has the smallest possible component height, in which a semiconductor chip is given the best possible protection against mechanical damage and chemical influences and in which it is possible, by using the smart card module, to produce a smart card having an extremely flat surface without bulges or sunken locations.
With the foregoing and other objects in view there is provided, in accordance with the invention, a smart card module, comprising a semiconductor chip having sides; an electrically insulating protective layer disposed on at least one of the sides of the semiconductor chip, the protective layer having a surface facing away from the semiconductor chip; contact-making points disposed on the surface of the protective layer; connection areas electrically conductively connected to the contact-making points; and a metallic lead frame receiving the semiconductor chip with the connection areas disposed at the front, the lead frame having contact areas electrically conductively contacting the connection areas.
The invention is distinguished by the fact that the semiconductor chip is not incorporated as a “naked” chip in the smart card module, but rather is provided with an electrically insulating protective layer on at least one side. The connection areas which are electrically conductively connected to the contact-making points of the semiconductor chip are formed on a surface of the protective layer which is remote from the semiconductor chip. This protective layer ensures increased protection of the semiconductor chip against mechanical stress and, at the same time, keeps away moisture and other harmful chemicals.
In accordance with another feature of the invention, particularly good protection is ensured when protective layers are provided on the top and bottom sides of the semiconductor chip or the semiconductor chip is enclosed by a housing on all sides.
The semiconductor components described, with connection areas disposed on a surface, are usually referred to as “die size packages” and are described, for example, in International Publication No. WO 96/02071.
Electrical contact is made between the semiconductor chip and the contact areas of the metallic lead frame through connection areas located on one of the surfaces of the die size package. For this purpose, the package is placed onto the lead frame with the connection areas at the front, and the electrical contacts are established.
In accordance with a further feature of the invention, the electrical contacts can be established through the use of soldered joints, for example. In that case, the connection areas, which are also referred to as bonding bumps, are composed of a solder material such as soft solder or solder paste or of a soldering-resistant material. In the latter case, a solder material is applied to the connection areas of the semiconductor chip component and/or to the contact-making points of the lead frame, and the soldered joints are then produced.
In accordance with an added feature of the invention, the soldered joints are implemented by using tin-lead solder. The high ductility of this material means that the soldered joints can absorb high mechanical stresses without material fatigue occurring.
In accordance with an additional feature of the invention, particularly good results are obtained when the metallic lead frame is composed of copper or of a copper alloy. Preferred alloys are copper-tin alloys such as CuSn
6
. The high ductility of these materials means that the smart card modules produced in this way and the smart cards containing these modules have a very low susceptibility to flexural loading. Their reliability is therefore excellent. The tapping side of the lead frame can be provided with one or more protective layers in a known manner.
The soldered joints between the chip connection areas and the lead frame may be produced in a manner that is known per se. In accordance with yet another feature of the invention, the preferred method is hot-air soldering. The soldering capability additionally ensures that the housing has a high resistance to moisture, in other words the risk of cracks in the package due to the ingress of moisture is minimal.
In accordance with yet a further feature of the invention, an alternative contact-making method is connecting the connection areas and the lead frame with the aid of a conductive adhesive. Materials and techniques correspond to those which are customarily used in the field of semiconductor technology.
The mounting of the die size packages can, in principle, be carried out in a conventional manner using customary method steps. The mounting is expediently carried out on a lead frame strip from which the individual smart card modules and the contact areas are separated, only after the positioning and contact-making of the die size packages.
With the objects of the invention in view there is also provided a smart card in which the sm
Heitzer Josef
Houdeau Detlef
Huber Michael
Mundigl Josef
Pueschner Frank
Gandhi Jayprakash N.
Greenberg Laurence A.
Infineon - Technologies AG
Lerner Herbert L.
Stemer Werner H.
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