JPH05291723A - Electrical connection structure and connection method between substrates - Google Patents

Abstract

PURPOSE:To enhance the connection strength of two substrates and to eliminate the connection error of the two substrates due to the movement of conductive particles by a method wherein, when sheet faces of the two substrates are connected electrically and mechanically to each other, the two substrates are bonded by using a bonding means which is adapted to materials constituting the individual substrates. CONSTITUTION:A polyethylene terephthalate substrate 1 which is provided with electrodes 3 on the surface is coated with a thermoplastic adhesive 6 so as to have a uniform thickness. Then, conductive particles 5 are dispersed on the thermoplastic adhesive 6; then, the conductive particles 5 are pressurized by using a pressurization means 10; at the same time, the adhesive 6 is heated by using a heating means 11. In addition, the adhesive is coated with a low-temperature-curing adhesive 7 so as to have a uniform thickness. While a substrate 2 on the other side is being aligned, it is placed on the low-temperature-curing adhesive 7 and pressurized. Thereby, terminals 3, 4 on the upper and lower substrates 1, 2 are connected electrically by means of the conductive particles 5. In addition, while the adhesive 7 is being pressurized, it is hardened. Thereby, the mechanical bonding strength of the substrates 1, 2 is increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in an electrical connection structure between substrates using a film-like joining means used for electrically connecting a flexible substrate or the like to a printed circuit board surface.

[0002]

2. Description of the Related Art Japanese Patent Laid-Open No. 63-310581 discloses that
A flexible printed circuit board is heat-sealed to the wiring board surface by using an anisotropic conductive film with a structure in which an insulating resin layer of the same material is bonded to a heat-melting insulating resin layer containing conductive particles dispersed therein. By doing so, there is disclosed a technique in which the wiring patterns exposed on both substrate surfaces are electrically connected to each other through the conductive particles in the film to improve the resolution and the adhesive strength. However, according to the present invention, the surfaces of the two substrates are welded at once by using the two-layered anisotropic conductive film made of the heat-meltable insulating resin of the same material. The problem is the lack of consideration for obtaining the optimum adhesive strength. That is, for example, when the above-mentioned heat bonding is applied to the connection between the substrate made of PET and the substrate made of polyimide or the like, the pitch of the electrodes provided on the surface of each substrate is deviated due to the difference in the coefficient of thermal expansion of the material forming each substrate. Occurs and the resolution decreases.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and when the plate surfaces of two substrates are electrically and mechanically connected to each other, the bonding means adapted to the material of each substrate is used. An object of the present invention is to provide an electrical connection structure such as a plurality of substrates that can improve connection strength by bonding and can eliminate connection mistakes due to movement of conductive particles.

[0004]

In order to achieve the above object, the first invention of the present application is to provide conductive particles for electrically connecting electrodes located on each surface of two substrates, and the conductive particles to each substrate. In a connection structure between substrates, which is composed of an adhesive for fixing, the adhesive is composed of a plurality of layers.

The second invention of the present application is characterized in that the adhesive applied to the surface of the one substrate is a thermoplastic adhesive, and the adhesive applied to the surface of the other substrate is a low temperature curing adhesive. In the third invention of the present application, after the polyester hot melt adhesive is applied and formed on the PET substrate, the conductive particles are embedded in the adhesive layer so that the conductive particles are electrically connected to the electrodes on the PET substrate. Then, the adhesive layer is heat-cured, and non-PE is applied on the low temperature curing adhesive applied on the adhesive layer.
The two substrates are electrically connected to each other via the conductive particles by pressing the T substrates.

According to a fourth aspect of the present invention, when at least one of the substrates to be joined is a PET substrate, an intermediate adhesive layer having elasticity after curing is provided between the adhesive layers applied to both substrate surfaces. It is characterized by

A fifth invention of the present application is a substrate comprising conductive particles for electrically connecting electrodes located on each surface of two substrates and an adhesive for fixing the conductive particles to each substrate. In the connection structure between the substrates, a thermoplastic adhesive sheet is coated on one of the substrates on which the conductive particles are dispersedly arranged, and then the sheet is pressed by an elastic body to press the thermoplastic adhesive sheet. Electrodes provided on both substrates through the conductive particles by developing a layer, applying a low temperature curing adhesive on the adhesive layer, and then pressing another substrate onto the low temperature curing adhesive. Is electrically connected.

The present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a cross-sectional view showing a connection structure according to a first embodiment of the present invention, and FIGS. 2A to 2D are views showing a manufacturing procedure for obtaining the connection structure of FIG.

In this embodiment, PET is used for PET substrate 1.
Materials other than (polyethylene terephthalate) (for example,
An example of electrically and mechanically connecting another substrate 2 made of a material suitable for bonding with a low temperature adhesive such as polyimide is shown. The electrode 3 on the upper surface of the PET substrate 1 and the other substrate 2 are shown.
Are electrically connected by the conductive particles 5 in a state where the electrodes 4 on the lower surface of each are opposed to each other, and the PET substrate 1 side is fixed with a thermoplastic adhesive (for example, polyester hot melt adhesive) to fix the conductive particles to the upper and lower substrates. Agent 6 and the other substrate 2 side is joined and integrated by a low temperature curing adhesive 7 such as a UV adhesive. Here, the electrodes include wiring patterns on the board, terminals of parts on the board, and the like. The conductive particles include metal particles, resin particles having a conductive coating film formed on their peripheral surfaces, and the like.

Next, the procedure for forming the connection structure shown in FIG. 1 will be described with reference to FIG. 2. First, in FIG.
The thermoplastic adhesive 6 is applied to the PET substrate 1 having the above in a uniform thickness (thickness such that the electrode 3 is buried). This is P
This is because a thermoplastic adhesive is the most suitable adhesive for the ET substrate, and a low-temperature adhesive such as a UV adhesive has a weak adhesive force.

Then, on the thermoplastic adhesive layer 6 (in particular,
After dispersing the conductive particles 5 on the electrode 3), the pressurizing means 1
The conductive particles 5 are pressurized by 0, and at the same time, the adhesive 6 is heated by the heating means 11. By this heating / pressurizing operation, the conductive particles 5 are embedded in the adhesive 6, and are fixed in a state of being in contact with the electrodes 3 without moving laterally.

In (c), the low temperature curing adhesive 7 is applied to this on a uniform thickness, and in (d), the other substrate 2 is placed on the low temperature curing adhesive 7 while being aligned and pressed. The terminals 3, 4 of the upper and lower substrates 1, 2 are electrically connected by the conductive particles 5, and the mechanical bonding strength between the substrates 1, 2 is enhanced by curing the adhesive 7 while applying pressure. .. The connection structure obtained in this example can be used by selecting and using an adhesive agent according to the material of each substrate to be joined. Sufficient bond strength can be secured without causing a problem.

Next, FIGS. 3 (a) and 3 (b) show a second embodiment of the present invention, in which an intermediate layer after curing is used to bond two substrates, at least one of which is a PET substrate. A characteristic is that an adhesive having high elasticity is interposed. In the illustrated example, the two PET substrates 1 and 15 are electrically and mechanically connected to each other. The electrode 3 on the upper surface of the first PET substrate 1 and the electrode 16 on the lower surface of the second PET substrate 15 are shown. The electrodes are electrically connected to each other by the conductive particles 5 in a state where they are opposed to each other, and the upper and lower substrates 1 and 15 and the upper surface of the first PET substrate 1 and the second PET substrate 15 are used to fix the conductive particles. A thermoplastic adhesive (polyester-based hot melt adhesive) 6 and 17 having a predetermined thickness is laminated on each of the lower surfaces, and an adhesive layer which increases the elasticity after curing as an intermediate layer between the thermoplastic adhesives 6 and 17 ( The intermediate adhesive layer) 18 is interposed.

As a procedure for forming this adhesive structure, first, the first thermoplastic adhesive 6 is applied on the first PET substrate 1 having the electrode 3 on its upper surface to a uniform thickness (thickness enough to bury the electrode 3). ). Then, the first thermoplastic adhesive layer 6
After the conductive particles 5 are dispersed on the top (particularly on the electrode 3), the conductive particles 5 are pressed by the pressing means and at the same time the adhesive 6 is heated by the heating means. By this heating and pressing work,
The conductive particles 5 are embedded in the adhesive 6 and come into contact with the electrodes 3. Subsequently, the intermediate adhesive 18 is applied to the first thermoplastic adhesive layer 6 to a uniform thickness, and then the second thermoplastic adhesive layer 17 is applied to the intermediate adhesive layer 18 to a uniform thickness. Finally, by placing the second PET substrate 15 while aligning it and heating it under pressure, the conductive particles 5 electrically connect the electrodes 3 and 16 of the upper and lower substrates 1 and 15 to each other. Increase the mechanical bonding strength of 1 and 2.

In the embodiment shown in FIG. 3, both substrates are PET substrates. However, when only one of them is a PET substrate, a thermoplastic adhesive is applied to the PET substrate side while the other non-PET substrate side is applied. Is coated with a low temperature curing adhesive, and an intermediate adhesive is interposed between both adhesives.

The connection structure obtained by the second embodiment is
Adhesives can be selected and used according to the material of each board to be joined, so sufficient bonding strength can be achieved without causing problems due to the difference in the coefficient of thermal expansion between boards as in the past. Can be secured. Furthermore, as shown in the schematic view of FIG. 3 (b), even in the peel test in which a tensile force is applied to the outer adhesive layers 6 and 7 respectively, the intermediate adhesive layer 18 is elastic in both directions indicated by the arrows. To deform,
The stress concentration at the interface indicated by arrow A is relaxed, and the resistance to the tensile force is improved.

Next, FIGS. 4 (a) to 4 (d) are views showing the procedure for forming the connection structure of the third embodiment of the present invention. In FIG. 4 (a), on the PET substrate 1 having the electrode 3 on the upper surface. After the conductive particles 5 are dispersed in the substrate, the heating means 2 is used in a state where the substrate is covered with the thermoplastic adhesive sheet 20 having a thickness smaller than the diameter of the conductive particles.
While the sheet 20 is being heated by 1, the sheet is pressed by the elastic member pressing means 22 such as silicon rubber to form the thermoplastic adhesive layer 20 on the substrate 1. At this time, the portion of the sheet 20 which is in contact with the conductive particles 5 is pressed by the pressing means 22 to be in a perforated state, flow down along the outer surface of the conductive particles 5, and finally as shown in (c), the electrode surface. Substrate 1 containing
Deploy along the top surface.

Subsequently, a low temperature curing adhesive 23 is applied thereon with a uniform thickness, and then the other substrate (here, a non-PET substrate) 24 is placed on the low temperature curing adhesive 23 while being aligned. By applying pressure, the conductive particles 5 electrically connect the electrodes 3, 25 of the upper and lower substrates 1, 24 to each other, and the adhesive 23 is cured while being pressed to mechanically bond the two substrates 1, 24 together. Increase strength.

(B) Since the conductive particles 5 are fixed by the thermoplastic adhesive 20 applied in (c), there is no possibility of defective conduction due to the movement of the particles. Although FIG. 4 shows the case where only one of the substrates is made of PET, the third embodiment can also be applied when both substrates are made of PET. In this case, the low temperature effect adhesive 23 Of course, a thermoplastic adhesive is used instead. Also,
The second embodiment may be combined with the third embodiment. That is, an intermediate adhesive layer having elasticity may be interposed between the adhesives 20 and 23 in FIG. 4D to increase the strength against the tensile force in the thickness direction.

In each of the above embodiments, P
Since a thermoplastic adhesive is applied to the bonding surface of the ET substrate, even if it is found that there is a conduction failure after curing each adhesive, it is necessary to reheat the thermoplastic adhesive to remelt it. By taking measures (moving conductor particles to a proper position, replenishing, replacing defective portion, etc.), it becomes possible to repair the substrate without causing significant waste such as discarding.

In each of the above-described embodiments, not only the printed wiring boards, the flexible printed boards, the printed wiring board and the flexible printed board are connected to each other, but the electrical connection between the surfaces of the two plate-like bodies is performed. It is generally applicable when mechanically connecting. Also, PET has been exemplified as a material that is difficult to connect with a low temperature curing adhesive, but this is only an example, and a thermoplastic adhesive is used for a substrate suitable for bonding with a thermoplastic adhesive, and low temperature curing is performed. The purpose of the present invention is to selectively apply a low temperature curing adhesive to a substrate suitable for bonding with an adhesive, and the material of the substrate to be connected is not limited.

[0022]

As described above, according to the present invention, it is ideal to use an agent suitable for each substrate as an adhesive for electrically and mechanically connecting the surfaces of two substrates. Good adhesive strength can be obtained. In particular, for a material such as a PET substrate that is not easily bonded by a low temperature curable adhesive, a thermoplastic adhesive is applied to enhance the adhesive force at the interface of the PET substrate, while the other non-PET substrate is used. Since the low temperature curing type adhesive is used for the adhesion to the substrate, it is possible to prevent the occurrence of conduction failure due to the pitch shift of the electrode portions due to the difference in the coefficient of thermal expansion of each substrate. Further, by interposing the elastic intermediate adhesive layer between the adhesive layers applied to the two substrates, the peeling force in the thickness direction prevents stress concentration at the adhesive interface. As a result, the strength is improved. Further, since the conductive particles are fixed on the electrode of one of the substrates by the thermoplastic adhesive, the particles do not move during the bonding work. Also,
When one of the substrates is non-PET, low-temperature bonding can be performed, so that the influence of heat can be suppressed to the necessary minimum. Further, since the portion coated with the thermoplastic adhesive can be softened by heating, the repair becomes easy.

[Brief description of drawings]

FIG. 1 is a sectional view showing a connection structure of a first embodiment of the present invention.

2A to 2D are views showing a manufacturing procedure for obtaining the connection structure of FIG.

3 (a) and 3 (b) are cross-sectional views showing the structure and effect of the second embodiment of the present invention.

4 (a) to 4 (d) are diagrams showing a procedure for forming a connection structure according to a third embodiment of the present invention.

[Explanation of symbols]

1, 15 PET substrate, 2 other substrate (adhesive that can be easily connected with low temperature curing adhesive), 3, 4, 25 electrodes, 5
Conductive particles, 6,17 thermoplastic adhesive, 7 low temperature curing adhesive, 10 pressing means, 11 heating means, 18 adhesive layer (intermediate adhesive layer), 20 thermoplastic adhesive sheet,
21 heating means, 22 elastic material pressing means, 23 low temperature curing adhesive, 24 other substrate (non-PET substrate),

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takeshi Kozuka 1-3-6 Nakamagome, Ota-ku, Tokyo Within Ricoh Co., Ltd. (72) Yoshihiro Yoshida 1-3-6 Nakamagome, Ota-ku, Tokyo Shares Inside Ricoh Company (72) Inventor Kazushi Iwata 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company, Ltd.

Claims (5)

[Claims] 1. A connection structure between substrates, comprising conductive particles for electrically connecting electrodes located on the respective surfaces of two substrates and an adhesive for fixing the conductive particles to the surfaces of the substrates. 2. The electrical connection structure between substrates according to claim 1, wherein the adhesive comprises a plurality of layers. 2. The substrate according to claim 1, wherein the adhesive applied to the surface of the one substrate is a thermoplastic adhesive, and the adhesive applied to the surface of the other substrate is a low temperature curing adhesive. Electrical connection structure between. 3. A polyester hot melt adhesive is applied and formed on a PET substrate, and then the conductive particles are embedded in the adhesive layer so that the conductive particles are electrically connected to the electrodes on the PET substrate. The adhesive layer is heat-cured, and the non-PET substrate is pressed onto the low-temperature curing adhesive applied on the adhesive layer to electrically connect electrodes provided on both substrates via the conductive particles. A method for electrically connecting substrates, the method comprising: 4. When at least one of the substrates to be bonded is a PET substrate, an intermediate adhesive layer having elasticity after curing is provided between the adhesive layers applied to both substrate surfaces, respectively. An electrical connection structure or a connection method between the substrates according to claim 1, 2 or 3. 5. A connection structure between substrates, comprising conductive particles for electrically connecting electrodes located on each surface of two substrates, and an adhesive for fixing the conductive particles to each substrate. , By coating a thermoplastic adhesive sheet on one substrate in which the conductive particles are dispersedly arranged and then pressing the sheet while pressing the sheet with an elastic body, to develop a thermoplastic adhesive layer on the substrate surface, After applying a low temperature curing adhesive on the adhesive layer and then pressing another substrate onto the low temperature curing adhesive, the electrodes provided on both substrates are electrically connected to each other via the conductive particles. A method for electrically connecting substrates, the method comprising: