JPH06186582A - Connecting structure and connecting method for electrode - Google Patents

Abstract

PURPOSE:To provide the electrode connecting structure having high reliability by a press welding method utilizing projecting electrodes consisting of conductive particles having a relatively large diameter. CONSTITUTION:The particles 6 for reflection of UV rays having the small diameter smaller than half the diameter of the conductive particles 5 or below are made to exit unevenly at a high density on an opaque substrate 2 side and the reflected UV rays 8 by these particles are cast even to the uncured parts of the adhesive 7 which are shadowed by the conductive particles 5 and are not irradiated with the UV rays 8 at the time of oppositely disposing a transparent substrate 1 formed with transparent electrodes 3 and the opaque substrate 2 formed with opaque electrodes 4 and connecting the electrodes by the UV curing type adhesive 7 while maintaining the electrical connection between both electrodes by the conductive particles 5, by which the adhesive 7 is completely cured and eventually the reliability of the electrode connecting structure is enhanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a connecting structure and a connecting method between electrodes of a circuit board on the device side and an external circuit board, and more particularly, to a liquid crystal through conductive particles having a relatively large diameter of 30 μm or more. The present invention relates to an electrode connecting method for electrically connecting a display plate and a semiconductor device.

[0002]

2. Description of the Related Art A circuit in which a semiconductor element such as an integrated circuit is formed and a circuit board such as a printed circuit board, a flexible circuit board or a ceramic circuit board are pressure-bonded by a simple method with ease, low cost and high reliability. Japanese Patent Application Laid-Open No. 2-32362 discloses a method of forming a protruding electrode by using an ultraviolet-curable adhesive and conductive particles for connection by the method described in JP-A-2-23623.
These are disclosed in Japanese Patent Publication No. 159090.

[0003]

However, all of these prior arts have a structure in which a large number of particles having a relatively small diameter of several μm to several tens of μm are used as the protrusion-forming material. However, recently, the high density of integrated circuits,
Along with miniaturization, there has been an increasing demand for connecting electrodes via conductive particles having a relatively large diameter of 30 μm or more.

When such particles having a relatively large diameter are used, contact with the electrode shown in FIG. 5 has not been a particular problem when conventional conductive particles having a relatively small diameter are used. The non-curing phenomenon of the ultraviolet-curing type adhesive occurs due to the fact that the ultraviolet ray does not hit near the portion. In particular, when the conductive particles are particles obtained by metal-coating a resin, there is a problem in that the reliability of the connection between the electrodes is reduced because the portion that is not exposed to the ultraviolet rays becomes large due to the deformation during pressing. .

The present invention has been made in view of the above problems and utilizes conductive particles having a relatively large diameter of 30 μm or more as a protruding electrode protruding from one substrate,
An object of the present invention is to provide a highly reliable electrode connection structure and connection method by a pressure welding method.

[0006]

The electrode connection structure of the present invention is an ultraviolet-curing type adhesive obtained by stacking an oxide transparent electrode formed on a transparent substrate and an opaque electrode formed on an opaque electrode substrate. In the connection structure in which the conductive particles are held by the conductive particles and the opposite electrodes are electrically connected by the conductive particles, in addition to the conductive particles that contribute to the connection, the light reflecting surface has a diameter that is less than half of the particles. It is characterized in that the particles are unevenly distributed on the opaque substrate side.

Further, the electrode connecting method of the present invention is a method of connecting an oxide transparent electrode formed on a transparent substrate and an opaque electrode formed on an opaque substrate to each other. Forming an adhesive layer on the electrode portion of the opaque substrate as an adhesive layer by applying or transferring an ultraviolet-curing type adhesive obtained by previously mixing particles having a light-reflecting surface having a diameter not more than half the diameter of the particles; After the electrodes and the opaque electrode are opposed to each other and aligned, a step of disposing conductive particles on the opaque electrode, and pressing these with the transparent electrode and the opaque electrode being connected via the conductive particles However, a step of irradiating ultraviolet rays from the transparent electrode side to cure the ultraviolet-curing type adhesive is included.

[0008]

In the present invention, particles having a light-reflecting surface, which are mixed in advance in an ultraviolet-curable adhesive, are unevenly distributed on the opaque substrate side. Therefore, when ultraviolet rays are irradiated from the transparent substrate side (conductive particle side), the reflected ultraviolet rays from this light reflecting surface will also hit the shadow of the large diameter conductive particles. It can be cured evenly, and as a result, the connection reliability between the electrodes is increased.

[0009]

Embodiments of the present invention will now be described with reference to the drawings while comparing the method of curing an adhesive according to the prior art with comparison. In all the drawings for explaining the embodiments, parts having the same function are designated by the same reference numerals, and repeated description thereof will be omitted.

FIG. 1 is a cross-sectional view showing an embodiment of an electrode connecting structure according to the invention as defined in claim 1, and FIG. 2 is a principle of eliminating an uncured portion of an ultraviolet curing type adhesive according to the present invention. 5 is a cross-sectional view for explaining the principle of generation of a non-cured portion of the adhesive according to the prior art.

In FIG. 1, a transparent substrate 1 (for example, PE) on which a transparent electrode 3 (for example, tin-doped indium oxide ITO) and an opaque electrode 4 (for example, tin) are formed on the surface thereof, respectively.
T) and the opaque substrate 2 (for example, polyimide) have the ultraviolet-reflecting particles 6 unevenly distributed on the opaque substrate 2 side through the conductive particles 5 and are pressure-contacted to each other by the ultraviolet-curing adhesive 7 so as to face each other.

Here, the conductive particles 5 are Au, Ag, Cu, C, In, having a relatively large diameter of 30 μm or more and having a relatively large diameter.
Metal particles made of a metal of Pd, Ni, Pb or Sn or an alloy of these metals, particles of elastic synthetic resin such as silicone rubber or urethane rubber coated with Au, Ni, C or the like, or a synthetic material having the elasticity. Au, A for resin
g, Cu, Ni, C, In, Pd and other metals, or conductive particles having elasticity mixed with fine particles of an alloy of these metals are included. Further, as the particles for reflecting ultraviolet rays, those having a diameter less than half the diameter of the conductive particles 5 and having a light reflecting surface made of the same material as the conductive particles 5 can be used.

In the connection of the transparent electrode 3 and the opaque electrode 4 shown in FIG. 1 by the pressure contact method, ultraviolet rays 8 are irradiated from the transparent electrode 3 side while the both electrodes are pressed through the conductive particles to cure the adhesive 7. When the diameter of the conductive particles 5 is large, the non-cured portion 9 of the adhesive, which is shaded by the conductive particles 5 and is not exposed to the ultraviolet rays 8 as shown in FIG. To do. In particular, when the conductive particles 5 are particles obtained by coating the resin elastic body with a metal, the portion 9 which the ultraviolet ray 8 does not reach becomes large due to the deformation at the time of pressurization.
As a result, there is a problem in that the connection strength between the electrodes is deteriorated due to a decrease in the adhesive strength due to insufficient curing of the ultraviolet curing type adhesive, and the reliability of the connection is reduced.

On the other hand, in the connection structure of the electrodes in which the small-diameter ultraviolet reflecting particles 6 having the light reflecting surface are unevenly distributed on the opaque electrode 4 side according to the present invention, as shown in FIG. Even the portion which is shaded by the ultraviolet rays 8 is not irradiated directly with the reflected ultraviolet rays from the ultraviolet ray reflecting particles 6 as indicated by the arrow in the figure, and as a result, the uncured portion 9 of the adhesive is generated. As a result, the adhesive strength is sufficiently exhibited and the reliability of the connection between the electrodes is improved.

Next, a preferred embodiment of the present invention will be described in more detail in the order of steps. Example 1 In FIGS. 3 to 13, particles 6 for ultraviolet ray reflection (diameter 8 μm
m, Ni-plated elastic particles on the silicone resin surface)
UV curable adhesive 7 (ThreeBond 303
4) which is mixed in a volume ratio of 25% on the substrate 11 (FIG. 3), the transfer head 12 is brought into contact with the surface side, and the ultraviolet curable adhesive 7 in which the ultraviolet reflecting particles 6 are mixed in the transfer head 12 Layer is transferred onto the transfer head 12 (FIG. 4).

Next, the base 11 is removed and the opaque electrode 4 is removed.
Bring the opaque substrate 2 on which (copper) is formed (FIG. 5), and then lower the transfer head to bring the layer of the ultraviolet curing adhesive 7 containing the ultraviolet reflecting particles 6 into contact with the opaque electrode 4. (FIG. 6) Further, the transfer head 12 is raised and transferred onto the opaque electrode 4 on the opaque substrate 2 by a transfer method, and a layer of an ultraviolet curing adhesive 7 for fixing conductive particles on the opaque electrode 4. Are formed (FIG. 7) (step 1).

Conductive particles 5 arranged on the conductive particle transfer head 13 (diameter 40 μm, N on the silicone resin surface)
i-plated and then Au-plated elastic particles) are aligned (FIG. 8) and then pressed against the opaque electrode 4 (FIG. 9), and then the conductive particle transfer head 13 is separated to separate the conductive particles 5 on the opaque electrode 4. Is transferred (FIG. 10) (step 2).

The opaque substrate 2 having the opaque electrode 4 on which the conductive particles 5 are transferred is attached to the particle fixing head 14 and the transparent plate 15.
A state in which the conductive particles 5 are electrically connected to the opaque electrode 4 by irradiating ultraviolet rays 8 from the side of the conductive particles 5 through the transparent plate 15 to cure the ultraviolet curable adhesive 7 after sandwiching the conductive particles 5 between them. Fix with. At this time, since the ultraviolet rays 8 reflected on the surface of the ultraviolet ray reflecting particles 6 hit the shaded portions generated by the conductive particles 5, the adhesive on the lower side of the conductive particles 5 is also cured (FIG. 11) (step 3). ).

An adhesive 7a for electrode connection (may be the same adhesive as the adhesive for fixing the conductive particles) is applied on the opaque electrode 4 to which the conductive particles 5 are fixed (FIG. 12).
(Step 4).

The transparent substrate 1 on which the transparent electrode 3 is formed is opposed to the opaque substrate 2, the electrodes are aligned with each other, and they are superposed and irradiated with ultraviolet rays from the transparent substrate 1 side while applying pressure (8 gf / particle or less). Do (Integrated amount of ultraviolet light 500 to 30
00nJ) (FIG. 13) (step 5).

In the above step 3, if the ultraviolet reflection amount particles are distributed and unevenly distributed on the opaque electrode with high density as described in claim 2, the ultraviolet curing type adhesive agent is further applied over the entire circumference of the conductive particles. It is more effective to cure completely. FIG. 14 shows a perspective view in the case where the transparent substrate side is the extraction electrode of the liquid crystal display device and the opaque substrate side is the connection substrate for the external drive circuit such as the semiconductor device.

Example 2 By the same process as in step 1 of Example 1, an ultraviolet-curable adhesive 7 containing no ultraviolet-reflecting particles 6 is applied onto the extraction electrode (transparent electrode 3) of the liquid crystal display device. (Step 1). The conductive particles 5 are transferred onto the transparent electrode 3 by the same process as in step 2 of Example 1 (step 2). Ultraviolet rays 8 are irradiated from the transparent electrode 3 side while applying pressure to fix the conductive particles 5 (step 3). On the opaque substrate 2 for connection, an adhesive 7 containing particles 6 for ultraviolet ray reflection (diameter 5 μm, polyurethane white resin elastic sphere) is applied (step 4). After aligning the extraction electrodes 1 of the liquid crystal panel on which the conductive particles 5 are fixed so as to face each other, the transparent electrodes 1 are overlapped and pressed.
Ultraviolet rays 8 are irradiated from the side. At this time, the irradiation of the reflected ultraviolet rays 8 from the ultraviolet ray reflecting particles 6 eliminates the uncured portion on the side of the opaque electrode 4 which is the cause of the conductive particles 5 (step 5). In this way, a highly reliable electrode connection structure as shown in FIG. 1 is obtained.

[0023]

According to the invention as set forth in claim 1, since the particles for ultraviolet ray reflection having a diameter less than half the diameter of the conductive particles are unevenly distributed on the opaque electrode, they are reflected on the surface of the particles. Further, since the ultraviolet rays also hit the adhesive on the lower side of the conductive particles, the uncured portion is eliminated and the reliability of the connection between the electrodes is improved. Further, according to the invention of claim 2, since the number of the particles for ultraviolet ray reflection, which is sufficiently larger than the number of the conductive particles, is dispersed in the lower part of the conductive particles, the adhesive agent below the conductive particles. Thus, the reflected ultraviolet rays are sufficiently applied to the conductive particles, so that the conductive particles can be completely cured over the entire circumference. Further, the above effect is exhibited even when the liquid crystal display device is connected to the semiconductor device by the flexible substrate. Further, according to the invention of claim 4, the ultraviolet curing capable of high-speed bonding without using a heating process. Since the uncured portion of the adhesive of the type can be eliminated, the process can be simplified and highly reliable inter-electrode connection can be performed in a short time.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of an electrode connection structure of the present invention.

FIG. 2 is a cross-sectional view illustrating the principle of action and effect of the present invention.

FIG. 3 is an explanatory view showing the steps of an embodiment of the electrode connecting method of the present invention.

FIG. 4 is an explanatory view showing the steps of an embodiment of the electrode connecting method of the present invention.

FIG. 5 is an explanatory view showing the steps of an embodiment of the electrode connecting method of the present invention.

FIG. 6 is an explanatory view showing the steps of one embodiment of the electrode connecting method of the present invention.

FIG. 7 is an explanatory view showing the steps of an embodiment of the electrode connecting method of the present invention.

FIG. 8 is an explanatory view showing the steps of one embodiment of the electrode connecting method of the present invention.

FIG. 9 is an explanatory view showing the steps of an embodiment of the electrode connecting method of the present invention.

FIG. 10 is an explanatory diagram showing the steps of an embodiment of the electrode connecting method of the present invention.

FIG. 11 is an explanatory diagram showing the steps of an embodiment of the electrode connecting method of the present invention.

FIG. 12 is an explanatory view showing the steps of an embodiment of the electrode connecting method of the present invention.

FIG. 13 is an explanatory view showing the steps of one embodiment of the electrode connecting method of the present invention.

FIG. 14 is a perspective view illustrating a connection between a liquid crystal display device according to the present invention and an external drive circuit.

FIG. 15 is a cross-sectional view for explaining the defect generation principle of the conventional technique.

[Explanation of symbols]

 1 Transparent Substrate 2 Opaque Substrate 3 Transparent Electrode 4 Opaque Electrode 5 Conductive Particles 6 Ultraviolet Reflecting Particles 7 Ultraviolet Curing Type Adhesive 7a Electrode Connecting Adhesive 8 Ultraviolet 9 Uncured Area 11 Base 12 Transfer Head 13 Conductive Particle Transfer Head 14 Particle fixing head

Claims (4)

[Claims] 1. An oxide transparent electrode formed on a transparent substrate and an opaque electrode formed on an opaque substrate are superposed on each other, and conductive particles are held by an ultraviolet curable adhesive.
In a connection structure for electrically connecting opposing electrodes with conductive particles, in addition to the conductive particles contributing to the connection, particles having a light-reflecting surface whose diameter is less than half of the particles are unevenly distributed on the opaque substrate side. An electrode connection structure characterized by the following. 2. The connection structure according to claim 1, wherein the small-diameter particles having the light-reflecting surface are dispersed and unevenly distributed on the opaque electrode at a density higher than that of the conductive particles. 3. The transparent electrode formed on the transparent substrate is a lead electrode of a liquid crystal display device, and the opaque electrode formed on the opaque substrate is a substrate on which a drive circuit is formed or a drive circuit substrate. The connection structure according to claim 1 or 2, which is a flexible substrate for connection. 4. A method of interconnecting an oxide transparent electrode formed on a transparent substrate and an opaque electrode formed on an opaque substrate, wherein a diameter of half or less of a diameter of conductive particles contributing to the connection is set. A step of forming an adhesive layer of an ultraviolet-curing type adhesive obtained by previously mixing particles having a light-reflecting surface on an electrode portion of an opaque substrate as an adhesive layer, and positioning the transparent electrode and the opaque electrode so as to face each other. After combining, a step of disposing conductive particles on the opaque electrode, and irradiating ultraviolet rays from the transparent electrode side while pressurizing the transparent electrode and the opaque electrode with the conductive particles interposed therebetween. And a step of curing the ultraviolet curing type adhesive.