Patent Application
20080123041
This application is based upon and claims the benefit of priority from Japanese Patent Application No. JP 2006-318947, filed on Nov. 11, 2006, the disclosure of which is incorporated herein in its entirety by reference.
1. Technical Field
The present invention relates to an electrode, a device and an electronic apparatus having the device. In particular, the present invention relates to a protruding electrode, a device having the protruding electrodes for external connections and an electronic apparatus having a substrate on which the device is mounted by using an anisotropic conductive film.
2. Background Art
For a display device for a portable device such as a mobile phone, a flat panel display device such as a liquid crystal display (LCD) device is used widely. It is required that circuit elements for driving a flat panel display device are arranged in high density thereon, while a large-sized flat panel display device is developed.
A COG (chip on glass) mounting method is known as one of technologies for mounting a circuit element on the flat panel display device. In a COG mounting method, a semiconductor device (hereinafter, described as an IC) as a drive circuit is directly mounted on a substrate of a flat panel display device. Bumps formed on a connecting face of an IC and electrodes formed on a substrate are joined electrically and mechanically via an anisotropic conductive film (hereinafter, referred to as an ACF).
An ACF is a film which is capable of thermal compression bond and includes insulating resin and conductive particles dispersed therein. Conductive particles are, for example, spherical resin balls plated with Ni or Au of having 2 μm to 10 μm in diameter, or metallic particles. When an ACF is heated and pressed, insulating resin is softened and spread. Some of conductive particles are pressed and held between bumps of an IC and electrodes of the substrate. When insulating resin is hardened, conductive particles make electrical connection between bumps of an IC and electrodes of a substrate to electrically connect an IC with circuits in a substrate.
When the IC 9 on which the bumps 31 are formed is mounted on the substrate of a display device, the ACF 14 is arranged between the connecting face of the IC 9 and the substrate of the display device. When the ACF 14 is heated and pressed, the insulating resin included in the ACF 14 is softened. Then the insulating resin spreads on the connecting face of the IC 9 together with conductive particles 15. Some conductive particles 15 flow out of the bump lines together with the insulating resin. Further some other conductive particles 15 are sandwiched between the bumps 31 and the electrodes of the opposing substrate. The sandwiched conductive particles 15 make electrical connection between the bumps 31 of the IC 9 and the substrate of the display device.
Here, when a distance between the bump line 30A and the bump line 30B or a distance between the bumps 31 is short, a flow of the conductive particles 15 is disturbed by the bumps 31. As a result, the conductive particles 15 remain between the bump line 30A and the bump line 30B, and further between the bumps 31. Remaining conductive particles 15 therebetween have strong tendency to aggregate. Aggregated conductive particles 15 short-circuit the bumps 31 and make a short-circuit failure between the bump lines and between the bumps 31.
Here, in order to prevent short circuit failure caused by the conductive particles 15 aggregating, a technology to lower a filling density of the conductive particles 15 in the ACF 14 is proposed. In the technology, the number of captured conductive particles 15 between the bump 31 and the electrodes of the substrate decreases. Then, disconnection between the IC 9 and the display device may occur.
An another technology for suppressing the aggregation of the conductive particle 15 which causes short-circuit failures between the bump lines 30 and between the bumps 31 is disclosed in a related art (Japanese Patent Application Laid-Open No. 2001-358165). In the related art, cross section of a bump 32 is an ellipse as shown in
An exemplary object of the present invention is to provide a protruding electrode which can suppress a short circuit occurrence and can perform an excellent electrical conduction between devices and to provide a device having the protruding electrodes and an electronic apparatus having the device.
An electrode arranged on a device according to an exemplary aspect of the invention includes a gap that is tapered toward an edge of the device and is formed from an end portion of the electrode to a different end portion thereof.
An electrode arranged on a device according to an exemplary aspect of the invention is for electrically connecting with an electronic apparatus via an anisotropic conductive film including conductive particles and a resin. The electrode includes a gap that is formed from an upper part of the electrode. A part of the resin which is softened by heating flows through the gap. The gap is tapered in a direction which the resin flows therethrough.
A device according to an exemplary aspect of the invention includes a plurality of electrodes arranged thereon. At least one of the electrodes having a gap that is tapered toward an edge of the device and is formed from an end portion of the electrode to a different end portion thereof.
A device according to an exemplary aspect of the invention includes a plurality of electrodes arranged thereon, the electrode connecting the device and an electronic apparatus electrically via an anisotropic conductive film including conductive particles and a resin. At least one of the electrodes includes a gap that is formed from an upper part of the electrode. A part of the resin which is softened by heating flows through the gap, and the gap is tapered in a direction which the resin flows therethrough.
An electronic apparatus to an exemplary aspect of the invention includes a conductive part and a device including a plurality of electrodes electrically connecting with the conductive part via an anisotropic conductive film including conductive particles and a resin. At least one of the electrodes has a gap which is formed from an upper part of said electrodes. A part of the resin which is softened by heating flows through the gap and the gap is tapered in a direction which the resin flows therethrough.
Exemplary features and advantages of the present invention will become apparent from the following detailed description when taken with the accompanying drawings in which:
Exemplary embodiments of the present invention will now be described in detail in accordance with the accompanying drawings.
A first exemplary embodiment will be described below using
A partial perspective view of a connecting face of an IC 9 is shown in
Next, a display device on which an IC 9 with bumps is mounted will be described.
In
When the ACF 14 is heated and pressed by the compression bonding tool 16, insulating resin in the ACF 14 is softened and spread. Conductive particles are also spread with the insulating resin and some of the spread conductive particles are held and sandwiched between the bumps of the IC 9 and the electrode pads of the TFT substrate 12. When the insulating resin is hardened, the IC 9 is fixed on the projecting area of the TFT substrate 12. The conductive particles sandwiched between the bumps of the IC 9 and the electrode pads of the TFT substrate 12 aggregate, and the IC 9 and the TFT substrate 12 are connected electrically.
A mounting structure of the IC 9 will be described in detail using
Electrode pads 21A and 21B are formed at tip portions of output wiring patterns 19A. Each of the electrode pads 21A in an electrode pad line 20A is connected with a bump 1A in a bump line 18A of the IC 9. Each of the electrode pads 21B in an electrode pad line 20B is connected with a bump 1B in a bump line 18B of the IC 9. The electrode pads 21A and the electrode pads 21B are formed so as to be able to oppose the bumps 1A and the bumps 1B of the IC 9, respectively. The electrode pad 21A and the electrode pad 21B are arranged in a staggered configuration on an IC mounting region.
On the other hand, a plurality of input wiring patterns 19B connected to a FPC 13 are formed on a TFT substrate 12 edge side of an IC mounting region. Electrode pads 21C connected with bumps 1C of the IC 9 are formed at tip portions of input wiring patterns 19B. The electrode pads 21C are arranged so as to oppose the bumps 1C.
On the other hand, in
When the IC 9 is mounted on the TFT substrate 12, a face of the IC 9 on which the bumps are formed is set on the ACF 14 arranged on the TFT substrate 12. The ACF 14 is hot-pressed in such a configuration. When the ACF 14 is heated, insulating resin therein is softened and flows out toward an outside from a lower part of the IC 9 together with conductive particles 15.
Some of the conductive particles 15 which flow out are captured and sandwiched between the bumps and the electrode pads of the TFT substrate 12. When the conductive particles 15 sandwiched therebetween aggregates, the FPC 13, the IC 9 and the TFT substrate 12 are connected electrically via the aggregated conductive particles. When the insulating resin of the ACF 14 is hardened, the IC 9 is fixed on the TFT substrate 12.
In
On the other hand, a part of the insulating resin and some of the conductive particles 15 in the ACF 14 flow through a distance between the bumps 1B toward the bump line 18A during the hot-pressing. Here, some of the conductive particles 15 are captured and sandwiched between the bumps 1B and the opposing electrode pads 21B.
Further, a part of the insulating resin and some of the conductive particles 15 flow out of a lower part of the IC 9 through a distance between the bumps 1A or the gaps 2 formed in each of the bumps 1A. Here, some of the conductive particles 15 which flow to the bump line 18A side are captured and sandwiched between the bumps 1A and the opposing electrode pads 21A.
When the conductive particles 15 captured between the bumps 1B and the electrode pads 21B and between the bumps 1A and the electrode pads 21A aggregate, the IC 9 and the output wiring patterns 19A connected to the TFT device are connected electrically.
Many conductive particles 15 which enter the gap 2 formed in the bump 1A cannot pass through the tapered gap 2 and stop thereinside. The many conductive particles 15 which remain in the gap 2 readily aggregate therein. And when the aggregated conductive particles 15 fill the tapered gap 2 to reach to an upper surface of the bump 1A, a upper surface area of the bump 1A in which the gap 2 is formed becomes substantially equal to an upper surface area of the bump 1B or the bump 1C in which no gap is formed. Therefore sufficient conductive particles 15 may be held between the bumps 1A and the opposing electrode pads 21A. Thereby, excellent electrical connection is given between the bumps 1A having the tapered gap 2 and the electrode pads 21A. Further, because many conductive particles 15 are captured in the tapered gap 2 while small conductive particles and the insulating resin passes therethrough, aggregated conductive particles between the bumps 1A and between the bumps 1A and 1B may decrease or disappear.
Next, formation processes of bumps will be described with reference to
First, the formation process of the bump 1B in which the gap 2 is not formed will be described using
Next, as shown in
After washing an inside of the opening 7 using an acid, as shown in
Next, formation processes of the bump 1A having the tapered gap 2 will be described using
Next, as shown in
After washing an inside of the openings 7 using an acid, as shown in
In the exemplary embodiment, the square pole-shaped bumps 1B and 1C are formed on the connecting face of the IC 9 by the method shown in
Although the bumps are formed of the gold (Au) in the exemplary embodiment, the bumps may be formed of a gold alloy including other metal, solder, etc. A size of the bumps and the gap 2 is not limited in particular. In the exemplary embodiment, in
In the exemplary embodiment, although the bumps 1A, 1B and 1C have the same outer sizes, an outer size of the bump may be changed for each bump line. In the same bump line, the outer size of each bump may be changed.
In the exemplary embodiments, although the tapered gap 2 is formed only in the bump 1A of the bump line 18A, the gap 2 may be formed in the bump 1B of the bump line 18B and the bump 1C of the bump line 18C.
Moreover, a shape of the gap 2 formed in each bump 1A of the bump line 18A is identical. Sizes of the width of the gap 2 may be changed for each bump 1A. The gap 2 formed in the center of the bump line 18A may have a wide opening because the conductive particles 15 tends to be collected therein.
In the exemplary embodiments, a slit-shaped gap 2 which reaches a surface of the IC 9 from a top surface of a bump 1A is formed, and the bump 1A is separated into two parts completely. However the shape of the gap 2 is not limited to such a shape. For example, the gap 2 may be a shallow gap having a depth shorter than height of the bump 1A. Then, the bump 1A is not completely separated into two parts. When a shallow gap is formed in the bump 1A, after forming a square pole-shaped bump 1A, a resist pattern exposing an area for the gap 2 is formed, and the bump 1A may be etched by a predetermined depth using the resist pattern as a mask.
Here,
When the IC 9 is mounted on the TFT substrate 12 via the ACF 14, the bump 1A having the tapered gap 2 is used in the exemplary embodiment as described above. Because small conductive particles 15 which reach just before the bump 1A during mounting flow smoothly out of the IC 9 through the gap 2 and many conductive particles are captured in the gap 2, it is suppressed that the conductive particles 15 aggregate between the bumps 1A and between the bump lines. Therefore, it can be suppressed that a short circuit failure occurs between the bumps and between the bump lines.
Many conductive particles 15 captured in the gap 2 aggregate therein. When the aggregated conductive particles 15 in the gap 2 reach to an upper surface of the bump 1A, an area of the upper surface thereof is substantially equal to an upper surface area of the bump 1B having no gap. Therefore, the conductive particles 15 are readily held and sandwiched between the bump 1A and an electrode pad of a TFT substrate. Accordingly an excellent electrical connection can be made between the IC 9 and the TFT substrate 12.
Next, a second exemplary embodiment will be described.
In the first exemplary embodiment, a tapered gap 2 whose width gradually decreases toward an edge side of an IC 9 is formed in a bump 1A. In contrast, in the second exemplary embodiment, as shown in
In
By setting the width of the gap 2B at the side thereof remote from the edge side of the IC 9 to decrease gradually toward the upper surface from the bottom of the bump 1D, the ACF 14 entered the inside of the gap 2B tends to flow up. Therefore, the ACF 14 easily enters the gap 2B. On the other hand, because the length of the upper base of the trapezoid is shorter than the average diameter of the conductive particle 15, many conductive particles 15 which enter the gap 2B can not escape to an upper direction and aggregate densely inside the gap 2B. The densely aggregated conductive particles 15 overflow from the upper surface of the gap 2 and reach an electrode of the TFT substrate to make an excellent connection between the IC 9 and the TFT substrate.
By forming the gap 2B whose width in a vertical direction of the side remote from the edge side of the IC 9 decreases gradually toward the upper surface from the bottom of the bump 1D, it is suppressed that a short circuit failure occurs between the bumps and between the bump lines. Moreover, better electrical conduction can be given to between the IC 9 and the TFT substrate.
The formation process for the bump 1D according to the second exemplary embodiment is almost the same as that for the bump 1A according to the first exemplary embodiment. That is, an Al pad 3 is formed in an area where a bump 1D and a gap 2B are formed, and an area other than the area where the bump 1D is formed is covered with a passivation protection film 4. Then a barrier metal 5 is deposited on the passivation protection film 4 and the Al pad 3.
Moreover, a film resist 6 is formed in an area other than the area where the bump 1D is formed. Here, in the formation process of the bump 1D according to the second exemplary embodiment, the film resist 6 having a horizontal cross section of a wedge shape is formed in an area corresponding to the gap 2B. A portion with a large width of the wedge-shaped cross section of the film resist 6 becomes narrow toward a vertical upper part thereof.
And an Au plating film 8 is formed inside the opening 7 of the film resist 6, and the film resist 6 and the barrier metal 5 are removed. Thus, the bump 1D having the gap 2B shown in
A modification of the second exemplary embodiment is shown in
In the gap 2C shown in
A third exemplary embodiment of the present invention will be described.
As shown in
By forming the V-shaped gap 2D in each bump 1F of the bump line 18D, an ACF 14 located between the bump line 18D and the bump line 18E can readily move to an area between the bumps 1F of the bump line 18D. By forming the V-shaped gap 2D, an occupied area by the gap 2D on the upper surface area of the bump 1F can be reduced. Therefore, the bump 1F can have enough upper surface area to capture conductive particles 15. Because the width of each portions of the gap 2D is tapered toward the edge of the IC 9, conductive particles 15 can be captured and aggregated efficiently.
A formation process for the bump 1F with the V-shaped gap 2D is almost the same as that for the bumps 1A and 1D according to first and second exemplary embodiments. In the exemplary embodiment, a film resist 6 is formed such that an opening 7 becomes a V-shaped during forming the film resist 6. Further, each of two portions of the gap 2D may be formed into a shallow form so that the gap 2D does not reach a bottom of the bump 1F.
The ACF 14 can flow between the bumps 1F and the upper surface area for capturing the conductive particles 15 does not greatly decreases, even if the V-shaped gap 2D is formed in the bump 1F. The conductive particles 15 can be accumulated efficiently in the gap 2D, since at least one of two portions of the gap 2D is tapered toward the edge of the IC 9.
A modification of the third exemplary embodiment is shown in
4. Fourth Exemplary Embodiment
Next, other exemplary embodiment of the present invention will be described.
The conductive particles 15 which enter the step shape gap 2F tend to remain at the step portion in the gap 2F. Thus the conductive particles 15 tend to aggregate inside the gap 2F and the aggregated conductive particles 15 easily fill the gap 2F to reach a surface thereof. Therefore, an excellent connection can be given between devices.
5. The Fifth Exemplary Embodiment
In the bump 1K shown in
Further, although the IC is described in the above-mentioned exemplary embodiments, the present invention can be applied to an optional device having a plurality of bumps as a terminal for connecting with different device. The LCD panel of the reflective type using the active matrix can be employed as the LCD device. A drive system of the LCD panel and a structure of the TFT can be different ones.
Moreover, although the bump according to the present invention is applied to the COG mounting is described, it is not limited to the COG mounting. It can be applied to mounting using the ACF, and applied to a COF mounting in which a semiconductor device is mounted on a flexible substrate.
Although the LCD device is described as a display device, the present invention can be applied to a display device such as a plasma display and an organic EL (electroluminescence) display. Moreover, the present invention can be applied to a general electronic apparatus in which a device with the bump is mounted via the ACF.
As mentioned above, the insulating resin and the conductive particles which flowed from the ACF pass the gap, and flow smoothly by forming the tapered gap in the bump arranged in the edge side of the device. Because the conductive particles do not aggregate between the bumps and the bump lines, it can be suppressed that a short circuit failure occurs between the bumps and the bump lines.
On the other hand, the part of the conductive particles which enter the gap can not pass the gap and are stopped therein because the gap is formed like a taper and its width becomes small in a direction through which the insulating resin and the conductive particles of the ACF flow. The conductive particles which stop in the gap aggregate therein and the aggregated conductive particles come to be pressed and held between the bump and the opposing electrode when reaching the upper surface of the gap of the aggregated conductive particles. Thereby, the electrode pad and the bump of the IC are connected electrically. At the same time, when the ACF is hardened, the device is fixed on the electronic apparatus.
When the bump structure of the related art described in the background art is used to mount an IC 9 on an electronic apparatus, the following problem occurs. That is, when a cross-sectional shape of a bump is made ellipsoidal, an upper surface area of the ellipsoidal bump is smaller than an upper surface area of a bump with a square cross-sectional shape. When the upper surface area of the bump is small, when the IC 9 is mounted on the electronic apparatus, the number of the conductive particles captured between the bump and an opposing electrode of the electronic apparatus decreases. Therefore, an electric continuity defect occurs between the IC 9 and the electronic apparatus.
On the other hand, when a bump is formed in an ellipsoidal shape having an upper surface area equal to an upper surface area of a square bump, a size of the ellipsoidal bump becomes large. Therefore, in order to form an ellipsoidal bump of a predetermined number, it is necessary to make a distance between bumps or a distance between bump lines short, and to make an area of a connecting face of an IC 9 wide. When the distance between bumps or the distance between bump lines is made short, it is easy to generate a short circuit failure. When the area of the connecting face of the IC 9 is made large, miniaturization of the IC 9 becomes difficult.
In contrast the above problem, in order to mount an IC on an electronic apparatus, when a bump with a taper-like gap according to the present invention is used, the following exemplary beneficial effects are obtained. That is, a short circuit failure is suppressed and an excellent conduction between devices can be given. Therefore, by using the bump with the taper-like gap, a small device with the bumps formed in a narrow pitch can be provided. Moreover, by mounting the small device according to the present invention on the electronic apparatus in high density, an electronic apparatus of small size, high quality and high reliability can be provided.
While the invention has been particularly shown and described with reference to exemplary embodiments thereof, the invention is not limited to these exemplary embodiments. It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the claims.
Further, it is the inventor's intention to retain all equivalents of the claimed invention even if the claims are amended during prosecution.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-318947 | Nov 2006 | JP | national |
