Active solid-state devices (e.g. – transistors – solid-state diode – Housing or package
Reexamination Certificate
1999-06-02
2001-09-11
Wong, Don (Department: 2821)
Active solid-state devices (e.g., transistors, solid-state diode
Housing or package
43
Reexamination Certificate
active
06288443
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a chip module with a substrate and at least one chip arranged on the substrate, wherein the chip is contacted via terminal surfaces arranged on its front side onto connecting leads of the substrate provided with a conductor path structure and the chip has a thickness which is reduced compared to its original thickness. The present invention further relates to a process for the production of a chip module with a substrate and at least one chip arranged on the substrate, wherein a handling unit with a chip and a substrate is formed by contacting the chip or chips onto the substrate provided with a conductor path structure in such manner that the chip or chips is/are contacted by its/their terminal surfaces onto connecting leads of the substrate, and wherein the processing of the chip or chips is effected by a material removal process on its or their rear side, the substrate providing for the handling and stabilization of the chip or chips during the processing.
BACKGROUND OF THE INVENTION
Chip modules comprising a chip arranged on a substrate are basically used in all cases in which simplified electric contacting of the chip is to be facilitated by means of substrate connecting leads which are substantially larger than the chip terminal surfaces. Thus such chip modules are used, for example, in chip cards and via the exposed substrate connecting leads extending over the card surface permit “external contacting” of the chip accommodated inside the chip card by the arrangement on the rear side of the substrate. Such chip modules are also used to construct so-called contactless chip cards in the case of which the substrate connecting leads provide for simplified contacting with an antenna coil arranged inside the card body. Naturally such chip modules can also be used, for example, to construct a so-called “combi-card” in the case of which external contacting for contact access to the card chip as well as internal contacting for contactless access to the chip via the antenna coil are facilitated by means of the substrate.
The combination of a chip with the substrate to form the chip module results in a composite structure, the thickness of which is relatively great compared to the thickness of the chip and the thickness of the substrate and which must be accommodated in a card body with defined outer dimensions. To ensure that the accommodation of a chip module in a card body imposes the least possible restrictions upon the possibilities of further component installations in the card body, it thus proves essential for the chip module to be designed to be as thin as possible.
A disadvantage of the known, relatively thick chip modules is that simply by virtue of their relative thickness, they have greater bending resistance compared to the flexible card body and therefore when the card body is subjected to bending stress as frequently occurs in everyday use, in particular when the substrate is arranged in the card surface as in the case of a contact card, the connection between chip module and card body can be stressed to a high level, leading to the detachment of the chip module from the card body. U.S. Pat. No. 5,155,068 has disclosed a chip module and process for the production of a chip module wherein the connection between chip and substrate is established in two consecutive process steps in which firstly the electric contacting of the bonding pads of the chip to terminal surfaces ofthe substrate is performed and then the mechanical connection between the chip and the chip substrate is effected by embedding the entire chip into a synthetic resin compound surrounding the chip. As a result of the embedding of the chip into the synthetic resin compound surrounding the chip, during the following abrasive processing ofthe rear side ofthe chip it is necessary to abrasively remove the material surrounding the chip in addition to the chip material.
JP-A-63 147 352, referred to in “Patent Abstracts of Japan”, also discloses a process for the production of a chip module wherein the connection between chip and chip substrate is established in two process steps and wherein the chip is embedded in a synthetic resin compound for mechanical connection to the chip substrate.
EP-A-0 207 853 has disclosed a process wherein a plurality of chip modules are produced continuously using a film carrier.
SUMMARY AND OBJECTS OF THE INVENTION
The object of the present invention is to propose a chip module and a process for the production of a chip module facilitating the simplified establishment of a connection between a chip and a chip substrate and more effective processing of the chip to reduce the chip thickness.
The chip module according to the invention utilizes the fact that the electric circuit planes in the silicon body of the chip are adjacent to the front- or contact side of the chip provided with the terminal surfaces, and the region of the silicon body adjoining the surface of the rear side is free of electric circuit planes. It is thus possible, without impairing the function of the chip, to remove the surface of the chip from the rear side until a minimum thickness of the chip body ensuring satisfactory chip functioning is obtained, and in this way to make the chip substantially thinner.
The reduction in thickness of the chip not only facilitates a corresponding reduction in the overall thickness of the chip module but also enables the bending behavior of the chip module to be influenced. As a result of the reduction in the chip thickness, the bending behavior of the chip is adapted to the bending behavior of the substrate, thus leading to an overall more readily bending, more flexible chip module, the bending behavior of which resembles that of the card body.
In the chip module according to the invention, in order to achieve an interlocking contacting with bonding pads formed on the terminal surfaces, the chip projects into recesses of the substrate whose base is formed by the conductor path structure. The engagement of the bonding pads in the recesses of the substrate leads to a connection between chip and substrate with particularly good shearing strength. Furthermore, due to this “sunken” arrangement of the bonding pads in the substrate, a particularly planar design ofthe chip module is achieved simply by virtue of its configuration.
Here the bonding pads ofthe chip are embedded in an electrically conductive connecting material which is arranged in the recesses of the substrate and provides both for the electrical contacting of the chip and for the mechanical connection of the chip to the substrate. By means of this embedding of the bonding pads in the connecting material it is also easily possible to compensate for any tolerances occurring in the difference between the height of the bonding pads and the depth of the recesses through the connecting material and, while retaining a reliable, electrically conductive connection between the bonding pads of the chip and the connecting leads of the substrate, to provide the flattest possible overall arrangement of chip and substrate wherein the surface of the chip and the surface of the substrate can adjoin one another directly, thus without a gap. In the production of the chip module according to the invention it is thus also possible to omit the application of an underfiller known in the context of underfiller technology. The mechanically stabilizing effect ofthe underfiller which improves the shearing strength of the chip module can also be dispensed with since a particularly stable, mechanical load-bearing connection is provided by the “embedding” of the bonding pads and the associated covering of the bonding pads with the connecting material on all sides, at least in partial regions of the contact metallizations. The bonding pads can be formed from any electrically conductive material, such as for example an electrically conductive adhesive or a contact metallization made of solder material or the like.
The above described form of interlocking contacting between a chip and a substra
Finn David
Rietzler Manfred
Clinger James
McGlew and Tuttle , P.C.
Wong Don
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