BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the manufacture of electronic devices, and in particular to the manufacture of an electronic device that includes an electronic component such as an integrated circuit chip electrically connected to one or more conducting traces provided on a substrate using an electrically conductive polymer.
2. Description of the Prior Art
The use of radio frequency identification (RFID) systems is expanding rapidly in a wide range of application areas. RFID systems consist of radio frequency tags or transponders (RFID tags) and radio frequency readers or interrogators (RFID readers). The RFID tags include an integrated circuit (IC) chip, such as a complementary metal oxide semiconductor (CMOS) chip, or some other electronic component and an antenna connected to the IC chip for communicating with an RFID reader over an air interface by way of RF signals. For ease of description and illustrative purposes, an IC chip is shown herein in connection with certain particular embodiments, but is should be appreciated that other electronic components, such as diodes, may also be used without departing from the scope of the present invention. Specifically, in a typical RFID system, one or more RFID readers query the RFID tags for information stored on them, which can be, for example, identification numbers, user written data, or sensed data. RFID systems have thus been applied in many application areas to track, monitor, report and manage items as they move between physical locations.
A number of RFID and related systems are known in the art. For example, U.S. Pat. Nos. 6,289,237 and 6,615,074, both entitled “Apparatus for Energizing a Remote Station and Related Method,” owned by the assignee hereof, describe a system where a remote station, such as an RFID tag, has a conversion device for energizing the remote station responsive to receipt of energy transmitted from a base station, such as an RFID reader. In addition, U.S. Pat. No. 6,856,291, entitled “Energy Harvesting Circuits and Associated Methods,” also owned by the assignee hereof, describes an antenna having a circuit for harvesting energy transmitted in space that may form part of an RFID tag. United States Patent Application Publication Nos. 20040189473 and 20040259604, both entitled “Recharging Method and Associated Apparatus,” and 20050030181, entitled “Antenna On A Wireless Untethered Device Such As A Chip Or Printed Circuit Board For Harvesting Energy From Space,” each describe various embodiments of a system and method for remotely energizing a remote station, such as an RFID tag, having an antenna having an effective area that is larger than it's physical area through the use of RF energy from a base station, such as an RFID reader, ambient energy or ultra-wide band energy. The antenna in such a system may be provided on an integrated circuit chip, such as a monolithic chip, or on a printed circuit board or other suitable substrate, such as a flexible substrate.
The IC chip and antenna components of an RFID tag are typically manufactured separately, often at different locations and by different entities. The IC chip and antenna components are then shipped to a manufacturing location where the RFID tags are assembled by attaching an IC chip and an antenna to a substrate, such as non-conducting polymer, plastic, paper, mylar, linen, gauze, FR-4 glass/epoxy laminate or the like, and electrically connecting the IC chip to the antenna. The IC chip typically includes a number of conductive pads, often made of aluminum, that are provided on a surface thereof which serve as points of contact for the electrical connections to the antenna. These points of contact may be, for example, on the order of 50 microns square or less, or, alternatively, on the order of 70-100 microns or larger. Thus, it is important for the IC chip connection points (the pads) and the corresponding points on the antenna to be aligned with one another before making a connection, which often proves to be difficult. Thus, there is a need for a method of manufacturing an RFID tag or similar electrical component that simplifies the connection of an IC chip to an antenna and the connection of the IC chip and antenna to a substrate.
In addition, as is known in the art, classical computer chips are typically formed by bonding a raw silicon die (also called a chip) to a chip carrier that provides a package for storing and carrying the die. The electrical connection points of the die are attached, through various known wire bonding techniques, to appropriate connection points on the chip carrier, which in turn are connected to pins on the chip carrier for making appropriate external connections to the chip carrier. The computer chip so formed is then typically used as a device in some form of electronic circuit, such as a circuit fabricated on a printed circuit board (PCB) or other appropriate substrate. Specifically, the pins of the chip carrier may be “plugged” into a socket or attached directly into a substrate such as a PCB using “through the hole” mounting techniques. More recent versions of chip carriers have the pins extended laterally to allow the chip carrier to be attached to one side of a PCB without affecting the second side. Such technology is commonly referred to as surface mount technology.
The classical view of chips is one with many pins extending from the carrier. As technology has advanced as in the case of system on a chip, more and more circuit elements are included within the silicon die, thereby reducing the pin count on typical processors and chips for embedded (and other) applications. In many situations where a chip such as an embedded processor or system on a chip is to be a part of a more complicated device for very large volume applications, the current practice has been to simply bond the silicon die directly to the substrate of the device, and to the contacts provided thereon, rather than to use a chip carrier as described above. This reduces the handling of the die (chip) and reduces total device cost. Once the die (chip) is bonded directly to contacts on the substrate, it is typically covered with some form of a protective covering. As will be appreciated, the above process requires an expensive bonding machine to perform multiple sequential bonds. Thus, there is a need for a method of manufacturing electronic devices that simplifies the connection of an IC die or chip to contacts that are provided on a substrate.
SUMMARY OF THE INVENTION
A method of making an electronic device is provided that includes placing an electronic component, such as a silicon die, on a substrate in a position where the first surface of the electronic component contacts the top surface of the substrate, and depositing an electrically conductive polymer on at least a portion of the second surface and the substrate in a first pattern, wherein the electrically conductive polymer in the first pattern contacts at least one electrically conductive contact provided on the second surface (opposite the first surface) of the electronic component. In addition, the electrically conductive polymer in the first pattern includes one or more endpoints positioned to contact one or more conducting traces that are provided on the substrate. Finally, the method includes curing the electrically conductive polymer in the first pattern.
An alternative method is provided that includes depositing an electrically conductive polymer on at least a portion of a substrate in a first pattern that includes one or more endpoints positioned to contact one or more conducting traces provided on the substrate, placing an electronic component, such as a silicon die, on the substrate in a manner in which at least one electrically conductive contact provided on the electronic component contacts a portion of the electrically conductive polymer, and curing the electrically conductive polymer in the first pattern.
The curing step in either method may include heating the electrically conductive polymer or allowing the electrically conductive polymer to dry. Furthermore, the electrically conductive polymer in either method may be a thermo-set material or, alternatively, a thermo-plastic material.
An electronic device is also provided that includes a substrate having one or more conducting traces provided thereon, and an electronic component provided on the substrate. A first surface of the electronic component contacts a top surface of the substrate. The electronic component has a second surface opposite the first surface that includes one or more electrically conductive contacts. The electronic device further includes an electrically conductive polymer provided on at least a portion of the second surface of the electronic component and the substrate in a first pattern. The electrically conductive polymer in the first pattern contacts at least one of the electrically conductive contacts. The electrically conductive polymer in the first pattern also includes one or more endpoints, each positioned to contact a respective one of the one or more conducting traces provided on the substrate.
An alternative electronic device is also provided that includes one or more conducting traces provided on a substrate, an electrically conductive polymer provided on at least a portion of the substrate in a first pattern including one or more endpoints, each of the endpoints being positioned to contact a respective one of the conducting traces, and an electronic component provided on said substrate. The electronic component includes a first surface that faces a top surface of the substrate and that has one or more electrically conductive contacts. Also, at least one of the one or more electrically conductive contacts is in contact with a portion of the electrically conductive polymer.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other advantages of the present invention will become readily apparent upon consideration of the following detailed description and attached drawings, wherein:
FIG. 1 is a bottom plan view of an exemplary IC chip that may form a part of an RFID tag or other electronic device fabricated in accordance with the present invention;
FIG. 2 is a top plan view of a mask used in one embodiment of a method of manufacturing an electronic device such as an RFID tag according to the present invention;
FIG. 3 is a flowchart showing a method of fabricating an antenna and connecting the antenna to an IC chip according to a first embodiment of the present invention;
FIG. 4 is a top plan view of a substrate on which the IC chip of FIG. 1 is positioned according to the method of FIG. 3;
FIG. 5 is a top plan view of the mask of FIG. 2 placed over the IC chip and substrate of FIG. 4;
FIG. 6 is a top plan view of a pattern of electrically conductive polymer deposited on the IC chip and substrate of FIG. 4;
FIG. 7 is a partial cross-section taken along lines 7-7 in FIG. 6;
FIG. 8 is a flowchart showing a method of fabricating an antenna and connecting the antenna to an IC chip according to a second embodiment of the present invention;
FIG. 9 is a top plan view of the mask of FIG. 2 positioned on a substrate according to the method of FIG. 8;
FIG. 10 is a top plan view of a pattern of electrically conductive polymer deposited on the substrate of FIG. 9;
FIG. 11 is a top plan view of the IC chip of FIG. 1 positioned on the pattern of electrically conductive polymer deposited and the substrate of FIG. 10;
FIG. 12 is a partial cross-section taken along lines 12-12 in FIG. 11;
FIG. 13 is a top plan view of a pattern of conductive polymer forming an antenna according to an alternative embodiment of the present invention;
FIG. 14 is a top plan view of a pattern of conductive polymer forming an antenna according to a further alternative embodiment of the present invention;
FIG. 15 is a top plan view of a number of antennas as shown in FIG. 14 fabricated on a flexible substrate to form a sheet wherein each portion of the substrate including an antenna may be readily separated;
FIG. 16 is a side view of the sheet shown in FIG. 15 in a rolled up condition;
FIG. 17 is a top plan view of a substrate having conducting traces provided thereon utilized in further embodiments of the present invention;
FIG. 18 is a top plan view of a mask utilized in further embodiments of the present invention;
FIG. 19 is a top plan view showing an IC chip positioned on the substrate of FIG. 17;
FIG. 20 is top plan view showing the mask of FIG. 18 positioned over the substrate and IC chip shown in FIG. 19;
FIG. 21 is a top plan view of the substrate and IC chip shown in FIG. 19 after a conductive polymer has been applied thorough the mask;
FIG. 22 is a top plan view showing the mask of FIG. 18 positioned on the substrate of FIG. 17 according to a particular alternate embodiment;
FIG. 23 is a top plan view of the substrate of FIG. 22 after the conductive polymer has been applied and the mask has been removed; and
FIG. 24 is a top plan view of the substrate of FIG. 23 (having the conductive polymer applied thereto) having an IC chip positioned thereon.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Several electrically conductive polymer materials, sometimes referred to as polymer-based conductive inks, are currently known. For example, one such polymer is described in U.S. Pat. No. 6,291,568, entitled “Polymer Composition,” the disclosure of which is incorporated herein by reference. The present invention solves many of the problems associated with the manufacture of RFID tags or similar electronic devices having an IC chip connected to an antenna and/or conducting traces by utilizing an electrically conductive polymer to, for example, fabricate the antenna, make the required connections between the antenna and the IC chip, make the required connections between the IC chip and one or more conducting traces provided on a substrate, such as, without limitation, non-conducting polymer, plastic, paper, mylar, linen, gauze, FR-4 glass/epoxy laminate or the like, and/or at least partially, if not wholly, attach the antenna and/or the IC chip to the substrate. The present invention may, for this purpose, employ any known or hereafter developed electrically conductive polymer or like material that has: (i) sufficient adhesion properties to enable it to adhere to the appropriate contact points on the IC chip and to the substrate, and (ii) sufficient electrical/conductive properties to enable it to either function as an antenna for the particular application in question or to make the required electrical connections to conducting traces for the particular application in question. Ideally, the sheet resistance or conductance of the electrically conductive polymer will be as good as a pure metal, such as copper, silver or aluminum. Preferably, the sheet resistance of the electrically conductive polymer is about 1.0 ohm/square or less, and most preferably 0.5 ohm/square or less. In one embodiment, the sheet resistance of the electrically conductive polymer is in the range of about 1.0 ohm/square to 0.1 ohm/square. In another embodiment, the sheet resistance of the electrically conductive polymer is in the range of about 0.1 ohm/square to about 0.01 ohm/square. In yet another embodiment, the sheet resistance of the electrically conductive polymer is in the range of about 0.01 ohm/square to about 0.001 ohm/square. In still another embodiment, the sheet resistance of the electrically conductive polymer is in the range of about 0.001 ohm/square to about 0.0001 ohm/square. In still another embodiment, the sheet resistance of the electrically conductive polymer is less than about 0.0001 ohm/square.
FIG. 1 is a bottom plan view of an exemplary IC chip 5 that may form a part of an RFID tag or other electronic device. IC chip 5 includes pads 10A, 10B, 10C and 10D on the bottom surface 15 thereof. Pads 10A, 10B, 10C and 10D are connected to the internal circuitry of the IC chip 5 and provide contact points for electrical connections to be made to an antenna and/or other external circuitry. In particular embodiments, the IC chip 5 may be a CMOS device and/or the pads may be made of aluminum.
FIG. 2 is a top plan view of a mask 20 used in one embodiment of a method of manufacturing an electronic device such as an RFID tag according to the present invention. Mask 20 includes a solid portion 25 made of, for example, thin metal sheet stock, magnetic film, plastic, paper or any other suitable material, and a cut-out portion 30, which may include two or more separate sections as shown in FIG. 2. As is known in the art, a mask such as mask 20 may be used to selectively apply a material to one or more surfaces placed thereunder. In particular, the cut-out portion 30 allows the material in question to pass through the mask 20 and defines a desired pattern for deposition of the material in question onto the one or more surfaces, and the solid portion 25 prevents the material in question from passing through the mask 20. In the present invention, the cut-out portion 30 defines a pattern for forming an antenna. As will be appreciated, numerous different antenna designs having different shapes and configurations are known and/or are possible, and FIG. 2 shows only one exemplary antenna design and shape.
FIG. 3 is a flowchart showing a method of fabricating an antenna and connecting the antenna to an IC chip such as IC chip 5 according to a first embodiment of the present invention. In step 100, the IC chip 5 is placed at a desired location on a substrate 35 with the pads 10A, 10B, 10C and 10D and the bottom surface 15 facing up (and not against the substrate 35) as shown in FIG. 4. The IC chip 5 may be affixed to the substrate 35, such as with an adhesive, to hold it in place during the remaining steps of the method, or may simply be positioned on the substrate 35 without any other means of affixation thereto. Next, at step 105, the mask 20 is placed over the IC chip 5 and the substrate 35 as shown in FIG. 5. The mask 20 is positioned such that selected portions 40 of the cut-out portion 30 are aligned with and placed over the pads 10A, 10B, 10C and 10D. Next, at step 110, an electrically conductive polymer is applied to the mask 20 by an appropriate method such as, without limitation, spraying or brushing. Step 110 will result in the electrically conductive polymer passing through the mask 20 and being deposited onto the IC chip 5 (and in particular the pads 10A, 10B, 10C, and 10D) and the substrate 35 only at the locations defined by cut-out portion 30. At step 115, the mask 20 is removed as shown in FIG. 6, with the result being a pattern 45 of the electrically conductive polymer being deposited the substrate 35. As described above, the pattern 45 of the electrically conductive polymer forms an antenna. Finally, at step 120, the electrically conductive polymer is cured, such as by heating it or exposing it to the ambient air for a period of time, thereby causing the conductive polymer to adhere to the IC chip 5, and in particular the pads 10A, 10B, 10C, and 10D, and the substrate 35. The electrically conductive polymer will in this manner be electrically connected to the pads 10A, 10B, 10C, and 10D and thus to the internal circuitry of the IC chip 5. Furthermore, the IC chip 5 will be affixed to the substrate 35 and held in place by the electrically conductive polymer. FIG. 7 is a partial cross-sectional view of the IC chip 5, the pattern 45 of electrically conductive polymer, and the substrate 35 taken along lines 7-7 in FIG. 6. As seen in FIG. 7, the electrically conductive polymer is deposited on and adhered to the pads 10A and 10D, the sides of the IC chip 5, and the substrate 35.
FIG. 8 is a flowchart showing a method of fabricating an antenna and connecting the antenna to an IC chip such as IC chip 5 according to a second embodiment of the present invention. The method begins at step 125, where the mask 20 is placed over the substrate 35 in an appropriate, desired location as shown in FIG. 9. Next, at step 130, the electrically conductive polymer is applied to the mask 20 by an appropriate method such as, without limitation, spraying or brushing. Step 130 will result in the electrically conductive polymer passing through the mask 20 and being deposited onto the substrate 35 only at the locations defined by cut-out portion 30. At step 135, the mask 20 is removed, with the result being a pattern 45 of the electrically conductive polymer being deposited the substrate 35 as shown in FIG. 10 that, according to an aspect of the present invention, forms an antenna. Next, at step 140, the IC chip 5 is placed on the electrically conductive polymer with the bottom surface 15 thereof facing down against the substrate 35 as seen in FIG. 11. Step 140 is performed before the conductive polymer is cured. Care is taken to position the IC chip 5 such that the pads 10A, 10B, 10C and 10D each contact a respective portion 50 (FIG. 10) of the pattern 45 of electrically conductive polymer. Then, at step 145, the conductive polymer is cured, such as by heating it or exposing it to the ambient air for a period of time, thereby causing the electrically conductive polymer to adhere to the IC chip 5, and in particular the pads 10A, 10B, 10C, and 10D, and the substrate 35. In addition, as was the case with the method shown in FIG. 3, the electrically conductive polymer will in this manner be electrically connected to the pads 10A, 10B, 10C, and 10D and thus to the internal circuitry of the IC chip 5. Furthermore, the IC chip 5 will be affixed to the substrate 35 and held in place by the electrically conductive polymer. FIG. 12 is a partial cross-sectional view of the IC chip 5, the pattern 45 of electrically conductive polymer, and the substrate 35 taken along lines 12-12 in FIG. 11. As seen in FIG. 12, the pads 10A and 10D are positioned on and adhered to the electrically conductive polymer, and the appropriate electrically conductive polymer as described elsewhere herein is deposited on and adhered to substrate 35.
FIGS. 3 and 8 show two particular embodiments of methods for applying the electrically conductive polymer. However, it should be understood that a number of alternative methods may be employed to apply the electrically conductive polymer to either the IC chip 5 and the substrate 35 (as in FIG. 6) or the substrate 35 (as in FIG. 10) before placing the IC chip 5 thereon. For example, the electrically conductive polymer can be applied in a desired pattern using ink jet printing technology (and an ink jet print head), such as continuous or drop-on demand ink jet printing technology. Alternatively, screen printing techniques may be used to apply the electrically conductive polymer. As is known, screen printing uses a screen, made of, for example, a porous fabric or stainless steel mesh, that is stretched tightly over a frame made of wood or metal. A stencil that defines the image to be printed is produced on the screen either manually or photochemically. Screen printing is performed by placing the screen over the object to be printed, placing the print material, in this case the electrically conductive polymer, onto the top of the screen, and forcing the print material through the screen openings using a squeegee that is drawn across the screen. The print material will pass through only in areas where no stencil is applied, thus forming an image on the object to be printed.
Furthermore, as is known, some antenna designs include one or more capacitors or capacitive elements. Typically, such capacitors or capacitive elements are formed on a substrate as part of the antenna structure by providing first and second conductive layers with a layer of a dielectric material, such as BaTiO3, provided therebetween. According to a further aspect of the invention, antennas having capacitors or capacitive elements and electronic components such as RFID tags having such antennas may be fabricated utilizing the principles described herein. Specifically, a first conductive layer made of an electrically conductive polymer may be applied using a first mask, a layer of dielectric material may be applied on top of the first conductive layer using a second mask, and a second conductive layer made of an electrically conductive polymer may be applied on top of the layer of dielectric material using a third mask (the third mask may be the same as the first and/or second mask). The various layers may be applied using either the method of FIG. 3 (on top on the IC chip 5) or the method of FIG. 8 (on the substrate 35 with the IC chip being attached thereafter). In addition, one or more of the layers may be applied using other techniques described herein, such as ink jet printing or screen printing. As will be appreciated, the IC chip 5 may, in this embodiment, be positioned such that one of the pads 10A, 10B, 10C and 10D is connected to the first conductive layer and another of the pads 10A, 10B, 10C and 10D is connected to the second conductive layer. Alternative dielectric materials that may be used include, without limitation, polyester (Mylar) film, combination polyester (Mylar) and polypropylene film, KF (polymer) film, polycarbonate film, Kapton film, polypropylene film, polysulfone film, polystyrene film, supermetallized polypropylene film, supermetallized polypulse film, Teflon film, and paper or Kraft paper film.
As yet another alternative, the present invention may be used to fabricate an electronic device having an RF antenna coupled to a non-linear device such as a rectifying diode as described in United States Patent Application Publication Number 20040189473, owned by the assignee of the present invention, entitled “RFID Radio Frequency Identification Or Property Monitoring Method And Associated Apparatus,” the disclosure of which is incorporated herein by reference. In such a device, one or more antennas 55 having the general shape and configuration shown in FIG. 13 may be fabricated and electrically connected to a non-linear device 60 such as a rectifying diode using an electrically conductive polymer as described herein. Furthermore, many conductive polymers, when cured, are flexible, and thus antenna 55 may be fabricated on a flexible substrate such as a non-conducting polymer, plastic, paper, mylar, linen, gauze or a like material.
According to yet another aspect of the present invention, it is possible to fabricate antennas made of a conductive polymer having varying, complex shapes using the techniques described herein. For example, a spiral shaped antenna 65 such as the one shown in FIG. 14 may be fabricated on a substrate for use in connection with, for example, an RFID reader. As used herein, the term spiral shall refer to any pattern of a line that winds around a fixed center point, including, without limitation, curved lines and lines having a number of straight segments having an angular relationship with one another. As will be appreciated, a spiral is only one example of a shape that may be utilized, and other shapes, such as, without limitation, those shown in FIGS. 10 and 13, or a dipole, monopole, folded dipole, patch or any other known or hereafter developed one, two or three dimensional antenna configuration, may also be used. A number of such antennas may be fabricated on a flexible substrate 70 to form a sheet as shown in FIG. 15. Due to the flexible nature of the flexible substrate 70 and the conductive polymer, the sheet may then be stored in a rolled up condition, for example in a cylindrical shape, as shown in FIG. 16, much like a roll of paper towels, until one or more of the antennas are used. It will be appreciated that, when rolled up, the sheet may take on any number of other shapes. Preferably, a separating mechanism 75, such as, without limitation, perforations, folds or cut line indications may be provided between each segment of the flexible substrate 70 that includes an antenna 65 to enable them to be separated easily when desired. Alternatively, the segments may be cut apart when desired using a cutting mechanism, such as, for example, a serrated edge like those typically provided with a roll of plastic wrap or aluminum foil used in the home.
The present invention also relates to various alternative embodiments in which, rather than using the conductive polymer to form an antenna as in the various embodiments described above, the conductive polymer is used to attach an IC chip, such as IC chip 5 shown in FIG. 1, to a substrate 100 shown in FIG. 17 and to make the electrical connections between the IC chip 5 and the conducting traces 105 provided on the substrate 100. FIG. 18 is a top plan view of a mask 110 used in these alternative embodiments. In particular, as described in greater detail below, the mask 110 is used in method steps similar to those shown in FIGS. 3 and 8 to attach the IC chip 5 to the substrate 100 and to make the electrical connections between the IC chip 5 and the conducting traces 105 provided on the substrate 100.
Mask 110 includes a solid portion 115 made of, for example, thin metal sheet stock, magnetic film, plastic, paper or any other suitable material, and a cut-out portion 120, which may include a single section or, alternatively two or more separate sections as shown in FIG. 18. The cut-out portion 120 allows a material, such as the conductive polymers described herein, to pass through the mask 110 and defines a desired pattern for deposition of the material in question onto the one or more surfaces provided under the mask 110, and the solid portion 115 prevents the material in question from passing through the mask 110. In this aspect of the present invention, the cut-out portion 120 defines a pattern for providing electrical connections between the ads 10A, 10B, 10C and 10D of the IC chip 5, which are connected to the internal circuitry of the IC chip 5, and the conducting traces 105 provided on the substrate 100. As will be appreciated, numerous different patterns are possible depending on the layout of the substrate 100, and FIG. 18 shows only one exemplary pattern.
In one particular embodiment, the IC chip 5 is placed at a desired location on the substrate 35 with the pads 10A, 10B, 10C and 10D and the bottom surface 15 facing up (and not against the substrate 100) as shown in FIG. 19. The IC chip 5 may be affixed to the substrate 100, such as with an adhesive, to hold it in place during the remaining steps of the method, or may simply be positioned on the substrate 100 without any other means of affixation thereto. Next, the mask 110 is placed over the IC chip 5 and the substrate 100 as shown in FIG. 20. The mask 110 is positioned such that selected portions of the cut-out portion 120 are aligned with and placed over the pads 10A, 10B, 10C and 10D and such that the outside ends of the cut-out portion 120 are aligned with the ends of the conducting traces 105. Next, an electrically conductive polymer (as described elsewhere herein) is applied to the mask 110 by an appropriate method such as, without limitation, spraying or brushing. This will result in the electrically conductive polymer passing through the mask 110 and being deposited onto the IC chip 5 (and in particular the pads 10A, 10B, 10C, and 10D) and the substrate 100 only at the locations defined by cut-out portion 120. The mask 110 is then removed as shown in FIG. 21, with the result being a pattern 125 of the electrically conductive polymer being deposited the substrate 100 that connects each of the pads 10A, 10B, 10C, and 10D to a respective one of the conducting traces 105. Finally, the electrically conductive polymer is cured, such as by heating it or exposing it to the ambient air for a period of time, thereby causing the conductive polymer to adhere to the IC chip 5, and in particular the pads 10A, 10B, 10C, and 10D, the substrate 100, and the conducting traces 105. The electrically conductive polymer will in this manner be electrically connected to the pads 10A, 10B, 10C, and 10D, and thus to the internal circuitry of the IC chip 5, and to the conducting traces 105. Furthermore, the IC chip 5 will be affixed to the substrate 100 and held in place by the electrically conductive polymer. Optionally, a protective coating, such as, without limitation, a coating made of a non-conductive polymer material, may be applied over the IC chip 5.
In an alternative particular embodiment, the mask 110 is placed over the substrate 100 in a position as shown in FIG. 22 wherein the outside ends of the cut-out portion 120 are aligned with the ends of the conducting traces 105. Next, an electrically conductive polymer is applied to the mask 110 by an appropriate method such as, without limitation, spraying or brushing. This will result in the electrically conductive polymer passing through the mask 110 and being deposited onto the substrate 100 only at the locations defined by cut-out portion 120. The mask 110 is then removed, with the result being a pattern 125 of the electrically conductive polymer being deposited the substrate 100 as shown in FIG. 23. Next, before the conductive polymer is cured, the IC chip 5 is placed on the electrically conductive polymer with the bottom surface 15 thereof facing down against the substrate 100 as seen in FIG. 24. Care is taken to position the IC chip 5 such that the pads 10A, 10B, 10C and 10D each contact a respective portion of the pattern of electrically conductive polymer. Then, the conductive polymer is cured, such as by heating it or exposing it to the ambient air for a period of time, thereby causing the electrically conductive polymer to adhere to the IC chip 5, and in particular the pads 10A, 10B, 10C, and 10D, the substrate 100, and the conducting traces 105. The electrically conductive polymer will in this manner be electrically connected to the pads 10A, 10B, 10C, and 10D, and thus to the internal circuitry of the IC chip 5, and to the conducting traces 105. Furthermore, the IC chip 5 will be affixed to the substrate 100 and held in place by the electrically conductive polymer. Again, an optional protective coating may be applied over the IC chip 5.
FIGS. 17-24 demonstrate two particular embodiments of methods for applying the electrically conductive polymer. However, it should be understood that a number of alternative methods may be employed to apply the electrically conductive polymer. For example, the electrically conductive polymer can be applied in a desired pattern using ink jet printing technology (and an ink jet print head), such as continuous or drop-on demand ink jet printing technology. Alternatively, screen printing techniques may be used to apply the electrically conductive polymer. Furthermore, many conductive polymers, when cured, are flexible, and thus patterns 125 may be fabricated on a flexible (as opposed to fixed) substrate 100 such as a non-conducting polymer, plastic, paper, mylar, linen, gauze or a like material to provide a electronic device having overall flexibility.
While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the breadth of the claims appended in any and all equivalents thereof.
Patent Application
20070012773
