INTERPOSER DEVICE

Abstract: A liquid-crystal display (LCD) comprises an LCD device, including a substrate (107) with substrate pads (106) on the top surface of the substrate (107) and a chip (105) with chip electrodes (104) operatively connected to said substrate pads (106). Additionally, an interposer device (100) is mounted between the chip (105) and the substrate (107), wherein the interposer device (100) inter-connects with substrate pads (106) configured in a first pattern with the electrodes (104) configured in an arbitrary second pattern on the chip area, wherein the electrodes (104) have a reduced electrode pitch essentially smaller than said pad pitch.

Description: APPLICANT: TELEFONAKTIEBOLAGET L M ERICSSON TITLE: INTERPOSER DEVICE Field of the Invention The present invention relates to an arrangement of mounting a chip on a substrate, and more particularly to an interposer device for use in an arrangement of mounting a chip on a substrate for operatively connecting chip electrodes with substrate pads in a liquid-crystal display (LCD) . Description of the Prior Art Liquid-crystal display (LCD) technology is commonly used in mobile telephones, portable PCs and other portable electronic devices. Increasing demands for displays providing even higher information content, e.g greyscale functionality, larger number of pixels, etc, result in an increased silicon area of the LCD driver chip. However, the area of the driver chip already constitutes a significant part of the total silicon area in for example state of the art mobile phones. A Chip on Glass (COG) LCD is an LCD having a semiconductor or an LCD driver chip mounted directly on an LCD substrate, preferably a glass substrate. COG has become commonly used due to its relatively low cost and that the mounting method is space efficient and provides a compact solution. However, conventional COG has a disadvantage. The pad layouts of an LCD driver used in the conventional COG implementation have to meet certain restrictions. The restrictions are mainly due to the layout rules that the conductive line pattern on the LCD substrate has to follow. US-A-5 467 210 discloses an arrangement of bonding an IC chip to an LCD device. The IC chip is a "bare IC chip" in which a single surface of a semiconductor bulk has multiple semiconductor devices fabricated thereon and a passivation film covers the semiconductor devices fabricated side, so that only terminals for connection to a device outside the chip are uncovered. The bare IC chip lacks a lead frame to which the bare IC chip is bonded, leads, bonding wires connecting the terminals of the bare IC chip to the leads, and a package of ceramic etc. A prior art solution of a Chip On Glass LCD device according to US-A-5 467 210 or the like is illustrated in FIG 1 and 2. According to FIG 1, electrodes 1 are provided on a single line along the circumference of a driver chip 2, which is the only possible pattern for the electrodes. Segment output electrodes are provided along one side 3, and row output electrodes are split up in two halves on each side 4 and 4 ' of the segment output electrodes 3. Further, the logic supply input electrodes and the I/O interface electrodes are placed on the opposite side 5 of the chip to the segment output electrodes 3. The chip 2 is mounted on a lower glass substrate 6 in the form of a rectangular board by a bonding method. In the bonding method employed in US-A-5 467 210, the chip includes bumps swelling from the electrodes. An anisotropic electrically conductive adhesive is applied to substrate pads 7 on the substrate 6. The anisotropic electrically conductive adhesive comprises an adhesive medium and electrically conductive particles dispersed in the adhesive medium so as to separate from each other. The anisotropic electrically conductive adhesive possesses an electrical conductivity only along the thickness thereof. The chip 2 is bonded to the pads 7 of the lower glass substrate 6 so that the bumps of the electrodes 1 are bonded to the pads 7. A top view of an LCD device comprising the chip 2 mounted on the lower glass substrate 6 as described above is shown in FIG 2. Further, an upper glass substrate 8 in the form of a rectangular board is mounted on the larger lower glass substrate 6, and a rectangular area 9 including a grid constitutes a display area in which data lines and scanning lines cross in the form of a matrix. An obvious solution in order to limit the increase of the silicon area and/or reduce the total silicon area of the driver chip 2 would be to use silicon processes with finer line widths. Today, a minimum pad pitch of about 50-100 μm can be used on the substrate whilst maintaining an acceptable yield loss from the driver mounting process. An LCD driver chip has several hundred electrodes for connection to the pads of the glass substrate, which sets a minimum silicon area of the chip. If the silicon area needed for the implementation of the functionality of the driver is less than the area set by the circumference on the chip needed to lay out the pads with the associated pad pitch, the driver is pad- limited. A further reduction of the chip area needed for the functionality by using silicon processes with finer line widths will, however, not lead to a smaller total chip area. Increasing demands for displays providing even higher information content result in driver chips with an increased number of pads and, consequently, a larger chip size. As described above, the driver chip will be pad- limited and the total chip area will not decrease even if smaller line widths are used. Summary of the Invention It is therefore an object of the present invention to provide an improved arrangement of mounting an IC chip on a substrate in order to reduce the problem of pad limitation. This object is accomplished by an interposer device according to the invention for use in the arrangement of mounting the IC chip on a substrate. Interposer electrodes are mounted on said interposer device according to a first pattern corresponding to a configuration of chip electrodes on the IC chip with a reduced electrode pitch. Further, interposer pads are mounted on said interposer device according to a second pattern corresponding to a configuration of substrate pads with a particular pad pitch on the substrate. In order to operatively connecting the chip electrodes with the corresponding substrate pads, the interposer pads are interconnected with interposer electrodes via interconnecting leads printed on the interposer . Another object of the invention is to provide an improved liquid-crystal display (LCD) with a reduced silicon area on the LCD driver, whereby the disadvantages caused by substrate pad-limitation are reduced. This object is accomplished by a liquid-crystal display (LCD) according to the invention, including an interposer device mounted between the IC chip and the substrate, wherein said interposer device operatively interconnects substrate pads configured in a first pattern on the substrate with electrodes configured in a second pattern on the driver chip, wherein said electrodes have a reduced electrode pitch essentially smaller than the pad pitch of the substrate pads. Still another object of the invention is to provide an improved method of mounting an IC chip on a substrate in order to reduce the problem of pad limitation. This object of the invention is accomplished by a method according to the invention, wherein the chip is bonded to an interposer device, and then the interposer device is bonded to the substrate, wherein the interposer device interconnects substrate pads configured in a first pattern on the substrate with electrodes configured in a second pattern, wherein said electrodes have a reduced electrode pitch essentially smaller than the pad pitch of the substrate pads. An advantage of the LCD according to the invention is that a total cost reduction is achieved, because the. cost per area of the interposer means is lower than the cost per area of the chip. Brief Description of the Drawings In order to explain the invention in more detail and the advantages and features of the invention a preferred embodiment will be described in detail below, reference being made to the accompanying drawings, in which FIG 1 is a perspective view of a glass substrate and a corresponding driver chip before bonding to the substrate according to a prior art method, FIG 2 is plan view of a prior art LCD display, comprising the chip and the glass substrate in FIG 1 after the bonding, FIG 3 is a perspective view of a glass substrate, a driver chip, and an intermediate interposer device according to the present invention before the bonding, and FIG 4 is plan view of an LCD display according to the invention, comprising the chip, the glass substrate, and the intermediate interposer in FIG 3 after bonding. Detailed Description of the Invention An embodiment of an interposer device according to the invention for use in an arrangement of mounting an IC chip on a substrate is shown in FIG 3. The interposer device 100 has interposer electrodes 101 or pads, mounted on the interposer device in a first pattern, and interposer pads 102, mounted on the interposer device 100 in a second pattern. In this embodiment the interposer pads 102 are designed as metallized holes through the interposer substrate for interconnecting with said interposer electrodes 101 by means of printed electronically conductive leads 103 provided on the same side of the interposer as the interposer electrodes 101. In an alternative embodiment of the interposer the interposer electrodes 101 are designed as metallized holes through the interposer substrate for interconnecting with said interposer pads 102 by means of the printed electronically conductive leads 103 provided on the same side of the interposer as the interposer pads 102. The interposer device 100 is a metallized polyamide substrate or flex film in the embodiment. The electrodes 101, pads 102 and the leads 103 are made of copper or gold/nickel plated copper in the embodiment. However, other electronically conductive materials can be used in alternative embodiments of the invention . The first pattern corresponds to a configuration of chip electrodes 104 mounted on an IC chip 105 with a reduced electrode pitch, and the second pattern corresponds to a configuration of substrate pads 106 mounted on a substrate 107, a glass substrate in the embodiment, with a particular pad pitch. In this embodiment, the interposer electrodes 101 as well as the chip electrodes 104 are configured in a grid pattern covering a smaller area than the interposer pads 102 configured according to the second pattern. The grid pattern is only an exemplification of a suitable pattern, but, of course, the chip electrodes 104 can be arranged in another pattern in an alternative embodiment of the invention. A preferred pattern is still the circumference pattern, in which the electrodes are provided on a single line along the circumference of the driver chip. However, there are several other possible patterns, which can be used within the scope of the invention. As shown in FIG 3, the interposer pads 102 are provided on a single line along the circumference of the interposer 100. Segment output pads are provided along one side 108, and row output electrodes are split up in two halves on each side 109 and 109'. Further, the logic supply input pads and the I/O interface pads are placed on the opposite side 110 of the interposer to the segment output pads . With reference to FIG 4, the chip 105 is bonded to the interposer 100 by means of bumps swelling from the chip electrodes 104 and an anisotropic electrically-conductive adhesive or film is applied to the interposer electrodes 101 on the interposer 100. The anisotropic electrically conductive adhesive comprises an adhesive medium and electrically conductive particles dispersed in the adhesive medium so as to separate from each other. The anisotropic electrically conductive adhesive possesses an electrical conductivity only along the thickness thereof. The chip 105 is bonded to the interposer 100 so that the bumps of the chip electrodes 104 are bonded to the interposer electrodes 101. Similarly, the interposer 100 is then bonded to the lower substrate 107 by means of bumps swelling from the interposer pads 102 or ' the substrate pads 106 of the substrate 107 and an intermediate anisotropic electrically- conductive adhesive is applied to the substrate pads 106 on the substrate 107. Thus, the interposer is bonded to the substrate pads 106 of the lower glass substrate 107 so that the bumps of the interposer pads 102 are bonded to the substrate pads 106. Consequently, the chip electrodes 104 are operatively connected to the substrate pads 106 by means of the interposer device 100. Even though the anisotropic electrically conductive adhesive bonding method is a preferable bonding method, the mounting of the chip on the interposer and the interposer on the substrate is not limited to this particular anisotropic electrically conductive adhesive system. An upper glass substrate 111 in the form of a rectangular board is mounted on the larger lower glass substrate 107, and a rectangular area 112 including a grid constitutes a display area in which data lines and scanning lines cross in the form of a matrix, forming a liquid- crystal display (LCD) for use in an electronic apparatus, such as a mobile telephone, pager, communicator, electronic organizer, smartphone etc. Even though characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure, it is to be understood that the disclosure is illustrative only, and changes may be made in detail, especially in matters of size of the chip and the pad layouts, i.e the electrode pattern on the chip and the corresponding electrodes on the interposer means, within the principles of the invention indicated by the broad general meaning of the claims. In this embodiment of the invention, the chip is rectangular. However, in another embodiment of the invention the chip can have a different shape, for example as a square, or as another kind of polygon etc.

Claims: CLAIMS 1. A liquid-crystal display (LCD), comprising an LCD device, including a substrate (107) with substrate pads (106) on the top surface of said substrate (107) and a chip (105) with chip electrodes (104) operatively connected to said substrate pads (106), and an interposer device (100) mounted between said chip (105) and said substrate (107), c h a r a c t e r i z e d in that said interposer device (100) interconnects said substrate pads (106) configured in a first pattern with said electrodes (104) configured in a second pattern placed accross the chip area, such as a grid pattern, wherein said electrodes (104) have an electrode pitch essentially smaller than the pad pitch. 2. A liquid-crystal display (LCD) according to claim 1, c h a r a c t e r i z e d in that said interposer device (100) has interposer electrodes (101) , mounted on said interposer device (100) according to said first pattern with said electrode pitch, wherein said interposer electrodes (101) are connected to said chip electrodes (104) , and interposer pads (102) , mounted on said interposer device (100) according to said second pattern with said pad pitch, wherein said interposer pads (102) are connected to said substrate pads (106), and in that said interposer pads (102) are interconnected with said interposer electrodes (101) . 3. A liquid-crystal display (LCD) according to claim 1 or 2, c h a r a c t e r i z e d in that said first pattern is a circumference pattern. 4. A liquid-crystal display (LCD) according to claim 1 or 2, c h a r a c t e r i z e d in that said first pattern is a grid pattern. 5. A liquid-crystal display (LCD) according to any of the preceding claims, c h a r a c t e r i z e d in that said chip (105) is bonded to said interposer device (100) by an anisotropic adhesive system. 6. A liquid-crystal display (LCD) according to claim 5, c h a r a c t e r i z e d in that said interposer device (100) is bonded to said substrate (107) by an anisotropic adhesive system. 7. A liquid-crystal display (LCD) according to any of the preceding claims, c h a r a c t e r i z e d in that said interposer device is a flex film provided with electronically conductive leads (103) interconnecting said interposer pads (102) with said interposer electrodes (101) . 8. A liquid-crystal display (LCD) according to any of the preceding claims, c h a r a c t e r i z e d in that said interposer pads (102) are metallized holes through said interposer substrate for interconnecting with said interposer electrodes (101) by means of printed electronically conductive leads (103) provided on said interposer (100), or said interposer electrodes (101) are metallized holes through the interposer substrate for interconnecting with said interposer pads (102) by means of the printed electronically conductive leads (103) provided on said interposer. 9. An electronic apparatus, c h a r a c t e r i z e d by a liquid-crystal display (LCD) according to any of the preceding claims. 10. An electronic apparatus according to claim 9, c h a r a c t e r i z e d in that said electronic apparatus is a mobile telephone, pager, communicator, electronic organizer, or smartphone. 11. An interposer device for use in an arrangement of mounting a chip (105) with chip electrodes (104) on a substrate (107) with substrate pads (106) for operatively connecting said chip electrodes (104) with said substrate pads (106) in a liquid-crystal display (LCD), c h a r a c t e r i z e d by interposer electrodes (101) , mounted on said interposer device (100) according to a first pattern corresponding to a configuration of said chip electrodes (104), placed accross the chip area, such as in a grid pattern, and interposer pads (102), mounted on said interposer device (100) according to a second pattern corresponding to a configuration of said substrate pads (106), wherein said interposer pads (102) are interconnected with said interposer electrodes (101) , and wherein said electrodes (104) have an electrode pitch essentially smaller than the pad pitch. 12. An interposer device according to claim 11, c h a r a c t e r i z e d in that said first pattern is a circumference pattern. 13. An interposer device according to claim 11, c h a r a c t e r i z e d in that said first pattern is a grid pattern. 14. An interposer device according to any of the claims 11 to 13, c h a r a c t e r i z e d in that said interposer device is a flex film provided with electronically conductive leads (103) interconnecting said interposer pads (102) with said interposer electrodes (101) . 15. An interposer device according to any of the claims 11 to 14, c h a r a c t e r i z e d in that said interposer pads (102) are metallized holes through the interposer substrate for interconnecting with said interposer electrodes (101) by means of printed electronically conductive leads (103) provided on the interposer (100), or said interposer electrodes (101) are metallized holes through the interposer substrate for interconnecting with said interposer pads (102) by means of the printed electronically conductive leads (103) provided on said interposer. 16. A method of mounting a chip (105) with chip electrodes (104) in a first configuration on a substrate (107) with substrate pads (106) in a second configuration for operatively connecting said chip electrodes (104) with said substrate pads (106) in a liquid-crystal display (LCD) , c h a r a c t e i z e d by the steps of bonding said chip (105) to an interposer device (100), and then bonding said interposer device (100) to said substrate (107) , wherein said interposer device (100) interconnects said substrate pads (106) configured in a first pattern with said chip electrodes (104) configured in a second pattern, placed accross the chip area, such as a grid pattern, wherein said electrodes have an electrode pitch essentially smaller than the pad pitch. 17. A method according to claim 16, c h a r a c t e r i z e d in that said chip (105) is bonded to said interposer device (100) by an anisotropic adhesive system. 18. A method according to claim 17, c h a r a c t e r i z e d in that said interposer device (100) is bonded to said substrate (107) by an anisotropic adhesive system.

Inventors: BJOERKENGREN ULF CHRISTIAN, GAERDENFORS TORBJOERN, BJOERKENGREN, ULF, CHRISTIAN, GAERDENFORS, TORBJOERN
Applicants: ERICSSON TELEFON AB L M, TELEFONAKTIEBOLAGET L M ERICSSON (PUBL)
Application year: 2000
Main classification: H01L23
IPC codes: G02F1, H01L23