Method to prevent intrusions into electronic circuitry

[0002] This application is a continuation of application Ser. No. 08/917,988, filed Aug. 25, 1997, which is a continuation of application Ser. No. 08/412,159, filed Mar. 28, 1995, now abandoned.

[0003] 1. Field of the Invention

[0004] The present invention relates to an integrated circuit package which prevents the interrogation of an integrated circuit.

[0005] 2. Description of the Related Art

[0006] Integrated circuits are typically housed within a plastic or ceramic package that is soldered to a printed circuit board. The integrated circuit may contain information such as microcode that is proprietary to the producer of the chip. The downloading of such information can be valuable to a competitor that may want to duplicate the circuit. Additionally, the integrated circuit may contain information proprietary to the end user, such as credit and banking information.

[0007] The information on a integrated circuit can be accessed by exposing the circuit die to a probe(s). The die can be exposed to the probe by simply removing the package lid or etching away the package material. It would be desirable to provide an integrated circuit package that would prevent the interrogation of an integrated circuit by an external probe.

[0008] The present invention is an integrated circuit package which has a flexible circuit that covers an integrated circuit. The flexible circuit contains a conductive line, which prevents a probe from accessing the integrated circuit. The conductive line of the flexible circuit can be attached to the power lines, synchronization line, memory erase line, or any other line that will disable, erase or otherwise prevent access to the integrated circuit if the flexible circuit conductive line is broken.

[0009] The objects and advantages of the present invention will become more readily apparent to those ordinarily skilled in the art after reviewing the following detailed description and accompanying drawings, wherein:

[0010] FIG. 1 is a perspective view of an integrated circuit assembly of the present invention;

[0011] a FIG. 2 is an exploded view of the integrated circuit package;

[0012] FIG. 3 is an enlarged view of a flexible circuit that is wrapped around an integrated circuit;

[0013] FIG. 4 is a perspective view of an integrated circuit and flexible circuit attached to a printed circuit board;

[0014] FIG. 5 is a cross-sectional view showing the integrated circuit, flexible circuit and printed circuit board within a package;

[0015] FIG. 6 is a schematic of a flexible circuit line that functions as a fuse for an integrated circuit;

[0016] FIGS. 7a-care schematics showing the flexible circuit line connected to a sync line, a memory erase line and a sensing line of an integrated circuit.

[0017] FIG. 8 is a flow chart illustrating a method to prevent intrusions into the integrated circuit assembly.

[0018] Referring to the drawings more particularly by reference umbers, FIGS. 1 and 2 show an integrated circuit assembly 10 of the present invention. The assembly 10 includes a flexible circuit 12 that is wrapped around an integrated circuit die 14 that is mounted to a substrate 15. The substrate 15 may have a plurality of contacts (not shown) that allow the substrate 15 and integrated circuit 14 to be connected to an external device. The integrated circuit 14 typically has a plurality of terminals and bonding pads located throughout the circuit. The signals and corresponding information within the integrated circuit 14 can be sensed and downloaded by an external probe 16 that is placed into contact with the pads. The flexible circuit 12 prevents the probe 16 from coming into contact with the terminals, thereby precluding access to the information within the integrated circuit 14. The integrated circuit 14 may be covered with an encapsulant (not shown) located between the outer surface of the circuit 14 and the undersurface of the flexible circuit 12. The encapsulant may further protect the surface of the circuit 14.

[0019] The flexible circuit 12 can be constructed to have a conductive line 18 routed throughout the circuit 12. The conductive line 18 can be an etched trace that is attached to an outer layer of dielectric polyimide material. The conductive line 18 can be routed in a serpentine manner to form a continuous single trace across the flexible circuit 12. The conductive line 18 may be spaced so that any attempt to place a probe onto the integrated circuit 14 will result in the probe making electrical contact with the conductive trace, thereby shielding access to the terminals and pads of the circuit 14.

[0020] As shown in FIG. 3, to increase the spacing of the conductive line 18 and decrease the cost of producing the flexible circuit 12, the flexible circuit 12 may have two layers wherein the conductive line 18′ of the first layer are located within the spaces between the conductive traces 18″ of the second layer. The flexible circuit 12 may be bonded to the integrated circuit 14 with an adhesive that stronger than the material of the flexible circuit 12, or the integrated circuit 14, so that any attempt to unwrap the flexible circuit 12 from the die 14 will result in the destruction of the integrated circuit 14, or the separation of the polyimide and the conductive line 18 so that the conductive line 18 remains attached to the die 14.

[0021] As shown in FIG. 4, one or more integrated circuits 14 can be mounted to a printed circuit board 20. The printed circuit board 20 may contain wire routing to interconnect the integrated circuits 14. The flexible circuit 12 can be wrapped around the integrated circuits 14 to protect the same. Additionally, the flexible circuit 12 can also be wrapped around the printed circuit board 20 to prevent access to the routing of the board 20. As an alternate embodiment, a portion of the flexible circuit 12 may be reinforced with a rigid substrate and mounted to the integrated circuits 14. The flexible circuit 12 may have additional conductive line to provide routing between the integrated circuits 14.

[0022] As shown in FIG. 5, the integrated circuits 14, flexible circuit 12 and printed circuit board 20 may be enclosed within a package 22. The package 22 may be formed by a plastic injection molding process. The integrated circuit 14 may be connected to external package leads (not shown) by vias, a lead frame, or other package interconnect known in the art. The flexible circuit 12 prevents access to the integrated circuits even if the circuits are removed from, or exposed within, the package.

[0023] FIG. 6 shows the conductive line 18 of the flexible circuit 12 connected to a pair of power pins of the integrated circuit 14. The conductive line 18 can function as a fuse, so that if the line is opened, power cannot be provided to the integrated circuit 14. Therefore if an intruder attempts to access the die 14 by cutting through the flexible circuit 12, the severing of the conductive line 18 will create an open circuit that will prevent operation of the integrated circuit 14.

[0024] As shown in FIG. 7, the conductive line 18 may also be connected to other pins of the integrated circuit 14 that will render the integrated circuit inoperable or in accessible if the conductive line 18 is broken. For example, the conductive line 18 of the flexible circuit 12 may provide the synchronization (sync) clock signal to the integrated circuit. The clock synchronization signal may be an unknown value, so that when the conductive line is broken, an intruder may not provide a valid sync signal to the integrated circuit to operate the same. If the integrated circuit 14 is a memory device, the conductive line 18 can be connected to the erase pin, so that an open line 18 will erase the contents of the memory device. As another alternative, the conductive line 18 may be connected to a sensing circuit which senses when the line 18 is broken or is being probed and disables the integrated circuit 14, accordingly. The flexible circuit 12 therefore prevents accordingly. The flexible circuit 12 therefore prevents access to the integrated circuit die and/or the information contained within the integrated circuit.

[0025] FIG. 8 is a now chart 50 illustrating a method to prevent intrusions into the integrated circuit assembly 10 according to one embodiment of the invention. The flexible circuit 12 is provided with the conductive line 18 (Block 52), and the conductive line 18 is coupled to the integrated circuit die 14 (Block 54). The conductive line 18 is routed to a synchronous clocking signal of the integrated circuit die 14 (Block 56). Next, the flexible circuit 12 is placed on the integrated circuit die 14 (Block 58). The integrated circuit assembly 10 is disabled if the conductive line 18 is broken (Block 60).

[0026] While certain exemplary embodiments have been described and shown in the accompanying drawings. it is to be understood that such embodiments are merely illustrative of and not restrictive on the broad invention, and that this invention not be limited to the specific constructions and arrangements shown and described, since various other modifications may occur to those ordinarily skilled in the art.