JPH08138773A - Electrode portion structure of printed wiring board - Google Patents

Abstract

PURPOSE: To achieve stable formation of insulating layers on electrode surfaces other than the conducting parts between the electrodes and conductive particles by forming on the electrode surfaces the insulating layers which, when an anisotropic conductive film is heated and pressed, are broken by the conductive particles of the anisotropic conductive film and achieve conduction between the conductive particles and the electrodes. CONSTITUTION: An anisotropic conductive film 7 is placed between a glass substrate 1 on which is formed an electrode 2 covered with an insulating layer 5 and a flexible printed board 3 on which is formed an electrode 4 covered with an insulating layer 6, and is heated and pressed. Then the adhesive layer 7a of the film 7 pressed flows and conductive particles 7b between the electrodes 2, 4 are pressed by the electrodes 2, 4 and allowed to penetrate through the insulating layers 5, 6 to make contact with the electrodes 2, 4. Therefore, even if the adhesive layer 7a has absorbed moisture and condensation forms on the layer 7a, leakage currents to the electrodes 2, 4 are shut off at the layers 5, 6 other than the contact region. Therefore, initial insulation resistance can be enhanced, and good insulation reliability can be secured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode portion structure of a printed wiring board, and more specifically, it is applied to an electrode portion structure for connecting the printed wiring board to another printed wiring board or another electronic component. In particular, the present invention relates to an electrode portion structure of a printed wiring board that can increase the initial insulation resistance and can secure good insulation reliability regardless of the connection pitch and the anisotropic conductive film.

[0002]

2. Description of the Related Art In recent years, with the spread of full-color, large-sized LCDs, mounting of flexible printed circuit boards represented by TAB is widely used. Usually, a glass substrate and a flexible printed circuit board are connected to each other by interposing a film in which conductive particles are dispersed in an insulating adhesive called an anisotropic conductive film between the glass substrate and the flexible printed circuit board,
It is connected by heating and pressurizing using a bonding tool. Hereinafter, description will be given with reference to the drawings.

FIG. 9 is a sectional view showing the structure of a conventional connecting device for a general glass substrate and a flexible printed circuit board, and FIG. 10 is a sectional view showing the movement of the anisotropic conductive film shown in FIG. 9 during heating and pressing. 11 is a sectional view showing the structure of the connecting portion shown in FIG. Conventionally, in a device for connecting a glass substrate and a flexible printed circuit board, an anisotropic conductive film 104 in which conductive particles 104b are dispersed in an adhesive layer 104a is arranged on an electrode 103 of a glass substrate 102 placed on a stage 101. Then, after arranging the flexible printed circuit board 105 on the anisotropic conductive film 104 so that the electrode 103 of the glass substrate 102 and the electrode 106 of the flexible printed circuit board 105 face each other, heating and pressing are performed by the bonding tool 107.

At this time, the anisotropic conductive film 10 heated and pressed is used.
As shown in FIG. 10, the adhesive layer 104a of No. 4 flows between the electrodes 103 and 106 of the glass substrate 102 and the flexible printed board 105, and the conductive particles 104b dispersed in the adhesive layer 104a are shown in FIG. As shown in the figure, the electrodes 103 and 106 are pressed against each other and held by the adhesive layer 104a which is cured after heating and pressurization.

[0005]

In the conventional electrode portion structure of the printed wiring board as described above, the conductive particles 104b in the anisotropic conductive film 104 have a density such that a short circuit is unlikely to occur between the adjacent electrodes 103 and 106. After being dispersed and the adhesive layer 104a is connected, it plays a role of an insulating material between the adjacent electrodes 103 and 106. However, as the connection becomes finer or the diameter of the anisotropic conductive film 104 becomes larger, 103,10
6, the distance between the electrodes 103 and 106, the distance between the electrodes 103 and 106 and the conductive particles 104b, and the distance between the conductive particles 104b are small, so that the insulation resistance is reduced and the insulation reliability is significantly reduced. there were.

Further, in the conventional electrode portion structure of the printed wiring board as described above, since the adhesive layer 104a easily absorbs moisture,
After connecting, moisture is absorbed to generate many free ions. When many free ions are generated in this manner, the insulating effect of the adhesive layer 104a is reduced, and the electrodes 103 and 106 and the conductive particles 10 are reduced.
Since the metal portion is exposed on the entire surface of both 4b, adjacent electrodes 103 and between adjacent electrodes 103 and adjacent electrodes 10
6 flows through the adhesive layer 104a between the electrode 6 and the electrode 106, and there is a problem that the insulation reliability is significantly reduced.

Therefore, according to the present invention, the electrode portion of a printed wiring board which can increase the initial insulation resistance and can secure good insulation reliability in any connection pitch and anisotropic conductive film. It is intended to provide a structure.

[0008]

According to the first aspect of the present invention,
In the electrode portion structure of a printed wiring board, which is formed by connecting a first wiring board and a second wiring board or another electronic component facing the first wiring board with an anisotropic conductive film, The anisotropic conductive film when heating and pressing the electrode surface formed on at least one of the second wiring board and the other electronic component facing the wiring board and the first wiring board It is characterized in that it is formed of an insulating layer which is destroyed by the conductive particles therein and electrically connects the conductive particles and the electrode.

A second aspect of the invention is characterized in that, in the first aspect of the invention, an insulating layer is formed on a base material between the electrodes on which the insulating layer is formed. A third aspect of the present invention is characterized in that, in the first and second aspects of the present invention, an insulating layer is formed on the surface of the conductive particles in the anisotropic conductive film.

According to a fourth aspect of the present invention, in the above-described first to third aspects, the insulating layer is made of an inorganic material. The invention according to claim 5 is the same as the invention according to any one of claims 1 to 4, wherein:
The total thickness of the insulating layers formed on the wiring board and the second wiring board, or on the first wiring board and the other electronic component is smaller than the particle diameter in the anisotropic conductive film. It is characterized by becoming.

[0011]

According to the first aspect of the present invention, the electrode surface formed on at least one of the first wiring board and the second wiring board facing the first wiring board or other electronic component, An insulating layer which is destroyed by the conductive particles in the anisotropic conductive film during heating and pressurization and electrically connects the conductive particles and the electrode is formed.

Therefore, when heating and pressing the electrode surface,
By forming an insulating layer that is broken by the conductive particles of the anisotropic conductive film and electrically connects the conductive particles and the electrode, a stable insulating layer may be formed on the electrode surface other than the conductive portion between the electrode and the conductive particles. it can. Therefore, in any connection pitch and anisotropic conductive film, it is possible to increase the initial insulation resistance, such as making it difficult for current to leak between opposing electrodes, and to obtain good insulation. The reliability can be secured.

According to the second aspect of the invention, the insulating layer is formed on the base material between the electrodes on which the insulating layer is formed. Therefore, by forming the insulating layer on the base material between the electrodes on which the insulating layer is formed, stable insulation is achieved not only on the electrode surface other than the conductive portion between the electrodes and the conductive particles but also on the base material between the electrodes. Since it can be formed by forming a layer,
It is possible to make it difficult for current to leak to the base material between the electrodes formed on the same base material, and thus to improve the initial connection reliability at any connection pitch, and to improve the insulation reliability. You can get a high connection.

According to the third aspect of the invention, an insulating layer is formed also on the surface of the conductive particles in the anisotropic conductive film. Therefore, by forming an insulating layer on the surface of the conductive particles in the anisotropic conductive film, a stable insulating layer can be formed not only on the electrode side but also on the conductive particle side. It is possible to make it difficult for current to leak through the conductive particles, so that the initial connection reliability can be increased at any connection pitch, and a connection with high insulation reliability can be obtained.

According to a fourth aspect of the invention, the insulating layer is made of an inorganic material. Therefore, by forming the insulating layer from an inorganic material, it is possible to form a more stable insulating layer having a low hygroscopic property and an insulating property on the electrode surface other than the conductive portion of the electrode and the conductive particles. Therefore, the initial connection reliability can be further increased at any connection pitch, and the connection with higher insulation reliability can be obtained.

According to the fifth aspect of the invention, the total thickness of the insulating layers formed on the first wiring board and the second wiring board, or on the first board and the other electronic component is the anisotropic conductive film. Is smaller than the particle diameter of. Therefore, the total thickness of the insulating layers formed on the first wiring board and the second wiring board, or on the first wiring board and the other electronic component is made smaller than the particle diameter in the anisotropic conductive film. As a result, the electrodes and the conductive particles can be brought into stable contact with each other, so that higher connection reliability can be obtained.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) FIG. 1 is a sectional view showing a structure before connection of an electrode portion structure of a printed wiring board according to an embodiment of the present invention, and FIG. 2 is an electrode portion structure of the printed wiring board shown in FIG. FIG. 3 is a cross-sectional view showing the structure of the connection device in FIG. 3, and FIG. 3 is a cross-sectional view showing the structure after connection of the electrode portion structure of the printed wiring board shown in FIG.

As shown in FIG. 1, insulating layers 5 and 6 are formed on the surface of the electrode 2 formed on the glass substrate 1 and the surface of the electrode 4 formed on the flexible printed board 3, respectively. Insulating layers 5 and 6 formed on the surfaces of the electrodes 2 and 4
May be made of a thermosetting resin that does not change by heating when connecting the electrode portions, or may be made of a thermoplastic resin that becomes soft when heated. The anisotropic conductive film 7 has an adhesive layer 7a.
Conductive particles 7b are dispersed and formed therein.

As shown in FIG. 2, the anisotropic conductive film 7 is arranged on the glass substrate 1 placed on the stage 11, and the flexible printed circuit board 3 is mounted on the anisotropic conductive film 7. The electrodes 2 formed on the flexible printed circuit board 3 and the electrodes 2 formed on the flexible printed circuit board 3 are arranged so as to face each other, and heating and pressing are performed by the bonding tool 12. At this time, the adhesive constituting the adhesive layer 7a of the anisotropic conductive film 7 pressed by the bonding tool 12 flows and the electrodes 2 and the flexible printed circuit board 3 formed on the glass substrate 1 flow.
The conductive particles 7b of the anisotropic conductive film 7 located between the electrodes 4 formed above are pressed against the electrodes 2 and 4 to form the insulating layers 5 and 6.
By penetrating the electrode 2 and contacting the electrodes 2 and 4,
4 are electrically connected (Fig. 3).

Conductive particles 7b contained in the anisotropic conductive film 7
Considering that they are particles that are not easily broken when the electrode part is pressed and have excellent conductivity, it is preferable to be composed of metal particles having high hardness using solder, Ni, or the like. As described above, in this embodiment, after the electrodes 2 formed on the glass substrate 1 and the electrodes 4 formed on the flexible printed circuit board 3 are connected by the conductive particles 7b of the anisotropic conductive film 7, the conductive particles 7b are Electrodes other than the contact area 2,
4 is covered with stable insulating layers 5 and 6.

Therefore, even if the adhesive constituting the adhesive layer 7a absorbs moisture and dew condensation occurs on the adhesive layer 7a, and the number of free ions causing a decrease in insulation resistance increases, the conductive particles 7b and the electrodes are prevented. Electrodes 2,4 other than the area where 2,4 are in contact
The insulating layers 5 and 6 covering the surface can block the leak current to the electrodes 2 and 4. Therefore, when the glass substrate 1 and the flexible printed circuit board 3 are heated and pressed through the anisotropic conductive film 7 to be connected to each other, it is possible to prevent current from leaking between the electrodes 2 and 4 facing each other.
In any connection pitch and anisotropic conductive film, the initial insulation resistance can be increased and good insulation reliability can be ensured. (Embodiment 2) Next, FIG. 4 is a sectional view showing a structure before connection of an electrode portion structure of a printed wiring board of an embodiment according to the invention of claim 2, and FIG. 5 is a sectional view of the printed wiring board shown in FIG. It is sectional drawing which shows the structure of the connection device in an electrode part structure.

As shown in FIG. 4, insulating layers 5 and 6 are formed on the entire surface of the glass substrate 1 on which the electrodes 2 are formed and on the entire surface of the flexible printed circuit board 3 on which the electrodes 4 are formed. ing. The insulating layers 5 and 6 formed on the surfaces of the glass substrate 1 and the flexible printed circuit board 3 are
It may be made of a thermosetting resin that does not change by heating when connecting the electrode portions, or may be made of a thermoplastic resin that becomes soft when heated. The anisotropic conductive film 7 is formed by dispersing conductive particles 7b in the adhesive layer 7a.

As shown in FIG. 5, the electrode 2 is placed on the stage 11.
The glass substrate 1 on which the insulating layer 5 is formed is arranged so as to cover the entire surface on the side, and the anisotropic conductive film 7 is formed on the glass substrate 1.
And the flexible printed circuit board 3 having the insulating layer 6 formed on the anisotropic conductive film 7 so as to cover the entire surface of the electrode 4 side, the electrode 2 formed on the glass substrate 1 and the flexible printed circuit board 3. The electrodes 4 formed on the surface 3 are arranged so as to face each other, and heating and pressing are performed by the bonding tool 12.

At this time, the adhesive forming the adhesive layer 7a of the anisotropic conductive film 7 pressed by the bonding tool 12 flows and the electrodes 2 formed on the glass substrate 1 and the flexible printed circuit board 3 are formed. The conductive particles 7b of the anisotropic conductive film 7 located between the electrodes 4 formed on the
The electrodes 2 and 4 are pressure-contacted with each other and penetrate the insulating layers 5 and 6 to come into contact with the electrodes 2 and 4, so that the electrodes 2 and 4 are electrically connected (FIG. 4).

Conductive particles 7b contained in the anisotropic conductive film 7
Considering that they are particles that are not easily broken when the electrode part is pressed and have excellent conductivity, it is preferable to be composed of metal particles having high hardness using solder, Ni, or the like. As described above, in this embodiment, after the electrodes 2 formed on the glass substrate 1 and the electrodes 4 formed on the flexible printed circuit board 3 are connected by the conductive particles 7b of the anisotropic conductive film 7, the conductive particles 7b are Electrodes other than the contact area 2,
At the same time that the surfaces of the glass substrate 1 and the flexible printed circuit board 3 where the electrodes 2 and 4 are not formed are also covered with the stable insulating layers 5 and 6, the insulating layers 5 and 6 are also stable.
It is configured to be covered by.

For this reason, even if the adhesive constituting the adhesive layer 7a absorbs moisture and dew condensation occurs on the adhesive layer 7a and the number of free ions causing a decrease in insulation resistance increases, the conductive particles 7b come into contact with each other. Insulating layers 5 and 6 to cover the surfaces of the electrodes 2 and 4 other than the regions where the electrodes 2 and 4 are formed and the surfaces of the glass substrate 1 and the flexible printed circuit board 3 where the electrodes 2 and 4 are not formed to block the leak current. You can

Therefore, when the glass substrate 1 and the flexible printed circuit board 3 are heated and pressed through the anisotropic conductive film 7 to connect the electrode portions, the electrodes 2 and 4 facing each other or on the same substrate 1 and 3 are connected. It is possible to make it difficult for current to leak between the formed electrodes 2 and 4, so that the initial insulation resistance can be increased and good insulation can be obtained in any connection pitch and anisotropic conductive film. The reliability can be secured.

In each of the above embodiments, the case where the anisotropic conductive film 7 in which the conductive particles 7b whose surface is not formed is exposed is simply dispersed in the adhesive layer 7a is used. However, the present invention is not limited to this. For example, as shown in FIGS. 6 and 7, the insulating layer 7c is formed on the surface of the conductive particles 7b such as metal particles or resin particles coated with metal. You may comprise.

Also in this case, as in Examples 1 and 2, the anisotropic conductive film 7 is arranged on the glass substrate 1 placed on the stage 11, and the flexible printed board 3 is placed on the anisotropic conductive film 7. Are arranged so that the electrodes 2 formed on the glass substrate 1 and the electrodes 4 formed on the flexible printed circuit board 3 face each other, and heating and pressing are performed by the bonding tool 12.

At this time, the conductive particles 7b pressed between the electrodes 2 and 4 penetrate the insulating layers 5 and 6 formed on the surfaces of the electrodes 2 and 4 and the insulating layer 7 formed on the surface of the conductive particles 7b.
When c is broken and contacts the electrodes 2 and 4, the electrodes 2 and 4 facing each other are made conductive. In this case, after the electrodes 2 and 4 are connected by the conductive particles 7b, not only the surface of the electrode 2 of the glass substrate 1 and the surface of the electrode 4 of the flexible printed circuit board 3 but also the surface of the conductive particles 7b other than the portions which are respectively conductive. Since all are covered with the stable insulating layers 5, 6, and 7c, it is possible to prevent the leakage current from flowing through the conductive particles 7b.

Therefore, even if dew condensation or the like occurs in the adhesive forming the adhesive layer 7a and the number of free ions increases, the glass substrate 1 and the flexible printed board 3 are heated and pressed through the anisotropic conductive film 7. When contacting with each other, it is possible to prevent current from leaking not only to the surfaces of the electrodes 2 and 4 but also to the surface of the conductive particles 7b, so that the initial insulation resistance is high at any connection pitch and anisotropic conductive film. It is possible to secure good insulation reliability.

Next, in each of the above embodiments, the insulating layer 5,
Considering that hygroscopicity is reduced and insulation is improved, 6 and 7c are preferably formed of an inorganic material. This inorganic material is, for example, SiO ₂ , Al ₂ O ₃
Any material having an insulating property and capable of forming a thin film may be used. Next, in each of the above embodiments, FIG.
As shown in FIG. 2, the insulating layers 5 and 6 on the surface of the electrode 2 formed on the glass substrate 1 and the surface of the electrode 4 formed on the flexible printed circuit board 3 are configured to have different film thicknesses, and the insulating layers 5 and 6 have different thicknesses. It is preferable that the total thickness is smaller than the diameter of the conductive particles 7b in the anisotropic conductive film 7. In this case, the electrodes 2, 4 and the conductive particles 7b can be brought into stable contact with each other, so that higher connection reliability can be obtained.

In each of the above embodiments, the case where the glass substrate 1 and the flexible printed circuit board 3 are used as the substrate has been described, but the present invention is not limited to this. For example, the glass substrate 1 side is usually used. The flexible printed circuit board 3 side may be used as an electronic component, and in this case, the same effect as in the case of using the glass substrate 1 and the flexible printed circuit board 3 can be obtained.

[0034]

According to the present invention, there is an effect that the initial insulation resistance is high and good insulation reliability can be secured in any connection pitch and anisotropic conductive film.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a structure before connection of an electrode portion structure of a printed wiring board according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a structure of a connection device in the electrode portion structure of the printed wiring board shown in FIG.

FIG. 3 is a cross-sectional view showing a structure after connection of the electrode portion structure of the printed wiring board shown in FIG.

FIG. 4 is a cross-sectional view showing a structure after connection of an electrode part structure of a printed wiring board according to an embodiment of the present invention.

5 is a cross-sectional view showing the structure of a connecting device in the electrode portion structure of the printed wiring board shown in FIG.

FIG. 6 is a cross-sectional view showing a structure after connection of an electrode portion structure of a printed wiring board applicable to the present invention.

7 is a cross-sectional view showing the structure of a connection device in the electrode portion structure of the printed wiring board shown in FIG.

FIG. 8 is a cross-sectional view showing a structure after connection of an electrode portion structure of a printed wiring board applicable to the present invention.

FIG. 9 is a cross-sectional view showing the structure of a conventional connecting device for a glass substrate and a flexible printed circuit board.

10 is a cross-sectional view showing the movement of the anisotropic conductive film shown in FIG. 9 during heating and pressing.

FIG. 11 is a cross-sectional view showing the structure of the connection portion shown in FIG.

[Explanation of symbols]

 1 glass substrate 2,4 electrode 3 flexible printed board 5,6,7c insulating layer 7 anisotropic conductive film 7a adhesive layer 7b conductive particles 11 stage 12 bonding tool

Claims (5)

[Claims] 1. An electrode portion structure of a printed wiring board, comprising an anisotropic conductive film connecting a first wiring board and a second wiring board or another electronic component facing the first wiring board. When the surface of the electrode formed on at least one of the first wiring board and the second wiring board facing the first wiring board or the other electronic component is heated and pressed, An electrode part structure of a printed wiring board, comprising an insulating layer formed by being broken by conductive particles in an anisotropic conductive film to electrically connect the conductive particles to the electrode. 2. The electrode part structure of a printed wiring board according to claim 1, wherein an insulating layer is formed on a base material between the electrodes on which the insulating layer is formed. 3. The electrode part structure of a printed wiring board according to claim 1, wherein an insulating layer is formed on the surface of the conductive particles in the anisotropic conductive film. 4. The electrode part structure of a printed wiring board according to claim 1, wherein the insulating layer is made of an inorganic material. 5. The anisotropic conductive film is the total film thickness of the insulating layers formed on the first wiring board and the second wiring board, or on the first wiring board and the other electronic component. The electrode part structure of a printed wiring board according to claim 1, wherein the electrode part structure is smaller than the inner particle size.