JP2002176238A - Connection structure of circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To bond each electrode of a circuit board surely to each conductor of a heat seal even if thick electrodes are arranged at a fine pitch on the circuit board. SOLUTION: A large number of electrodes 2 are arranged at the fringe on the upper surface of a circuit board 1, an insulation film 12 is formed to cover these electrodes 2 and then cut until the upper surface of each electrode 2 is exposed, a metal plating 13 is formed on the upper surface of each electrode 2, and then each conductor 5 of a heat seal 3 is bonded to each electrode 2 through the metal plating 13. Even if the electrode 2 is thick, upper surface of the electrode 2 and the insulation film 12 can be formed flat. Since a substantially flat surface can be obtained even if each metal plating 13 is formed on the upper surface of each electrode 2, the circuit board 1 and the heat seal 3 can be bonded surely through an adhesive layer 6 even if the electrodes 2 are arranged at a fine pitch. Consequently, each electrode 2 and each conductor 5 can be bonded surely through the metal plating 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a connection structure for a circuit board used in electronic equipment such as an electronic wristwatch and a portable telephone.

[0002]

2. Description of the Related Art For example, in an electronic wristwatch, when a circuit board is electrically connected to a liquid crystal display device, connection electrodes arranged at one end of the circuit board and one end of the liquid crystal display device are arranged. The connection terminals are connected by heat sealing. In this case, the pitch of the connection electrodes of the circuit board is formed wider than the pitch of the connection terminals of the liquid crystal display device in order to ensure the reliability of connection with the heat seal. In such a connection structure, high-density mounting is demanded,
In response to this, it is necessary to narrow the pitch of the connection electrodes of the liquid crystal display device and the connection electrodes of the circuit board, in particular, to the same degree as that of the connection terminals of the liquid crystal display device.

FIGS. 6 (a) and 6 (b) are enlarged sectional views of an essential part showing an example thereof. In these figures,
A plurality of connection electrodes 2 are formed in rows on the upper surface of the circuit board 1. These electrodes 2 are patterned at a narrow pitch P, for example, a pitch of about 0.25 mm, by etching a copper foil or copper plating provided on the upper surface of the circuit board 1 into a predetermined shape. Is 3
The thickness is about 0 μm. The heat seal 3 bonded to the electrodes 2 has a structure in which a plurality of conductors 5 are formed on the lower surface of the base film 4 corresponding to each electrode 2, and an adhesive layer 6 is provided between the conductors 5. It has become.
In this case, the adhesive layer 6 is formed to be slightly thicker than the thickness of the conductor portion 5 and provided so as to slightly cover the lower surface of each conductor portion 5.

When the circuit board 1 and the heat seal 3 are connected to each other, the conductors 5 of the heat seal 3 are positioned so as to face each electrode 2 of the circuit board 1 while facing each other. Each conductor 5 is pressed against each electrode 2. Then, as shown in FIG.
Penetrates through the adhesive layer 6 slightly covering the lower surface thereof, and each conductor portion 5 and each electrode 2 are electrically connected. At the same time, the adhesive layer 6
Sinks together with the base film 4 and is adhered to the circuit board 1 side. Thereby, each electrode 2 of the circuit board 1 and each conductor 5 of the heat seal 3 are electrically connected and joined.

[0005]

However, in such a connection structure of the circuit board 1, the pitch P between the electrodes 2 formed on the circuit board 1 is as narrow as about 0.25 mm and the thickness of each electrode 2 is small. Since T is as thick as about 30 μm, when connecting the circuit board 1 and the heat seal 3, as shown in FIG. 6B, the base film 4 of the heat seal 3 located between the conductors 5 is bent. However, the adhesive layer 6 of the heat seal 3 does not securely adhere to the upper surface of the circuit board 1, and a gap S may be generated between the lower surface of the adhesive layer 6 and the upper surface of the circuit board 1. There is a problem that the bonding state between each electrode 2 and each conductor portion 5 of the heat seal 3 becomes unstable and connection reliability is lacking.

SUMMARY OF THE INVENTION An object of the present invention is to make it possible to reliably join each electrode of a circuit board to each conductor of a heat seal even if the pitch of each electrode of the circuit board is narrow and its thickness is large. It is.

[0007]

According to the present invention, there is provided a connection structure for a circuit board, wherein a plurality of electrodes are formed in a row, and an insulating film is applied so as to cover the plurality of electrodes. And a heat seal provided with a plurality of conductors joined to the plurality of electrodes of the circuit board. According to the present invention, even if the thickness of each electrode of the circuit board is large, the insulating film is cut off until the upper surface of each electrode is exposed, since the insulating film applied to cover the electrodes on the circuit board is exposed. Because it can be formed on a flat surface with no steps, even if the pitch of each electrode is narrow, an adhesive layer is provided between each conductor of the heat seal and each electrode of the circuit board is connected to each conductor of the heat seal In this case, the adhesive layer of the heat seal can be securely adhered to and adhered to the insulating film of the circuit board, so that each electrode of the circuit board and each conductor of the heat seal can be securely bonded. it can.

In this case, as described in claim 2, the metal plating such as nickel or gold is formed on the upper surface of the plurality of electrodes exposed by shaving the insulating film, so that the thickness of the metal plating is reduced. However, the metal plating is thinner than the electrodes, so it is almost flat, and the adhesive layer for heat sealing can be securely bonded to the insulating film on the circuit board. Each electrode of the substrate and each conductor of the heat seal can be securely joined, and the reliability of conduction between each electrode and each conductor can be enhanced by metal plating. Further, as described in claim 3, even if the plurality of electrodes have a structure including a conductor pattern such as copper and metal plating such as nickel or gold formed on the entire surface of the conductor pattern, Similar to the invention described in Item 1, the insulating film can be formed on a flat surface with no steps, so that each electrode of the circuit board and each conductor of the heat seal can be securely joined, By plating, the reliability of conduction between each electrode and each conductor can also be enhanced.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] A first embodiment of a circuit board connection structure according to the present invention will be described below with reference to FIGS. 6 (a) and 6 (b) are denoted by the same reference numerals and will be described. This connection structure, as shown in FIG.
In the connection structure between the circuit board 1 and the heat seal 3 when the circuit board 1 and the liquid crystal display device 10 are electrically connected by the heat seal 3, the pitch of the connection terminals 11 arranged on the edge of the liquid crystal display device 10 And the pitch P of the electrodes 2 of the circuit board 1 is formed to be narrow at substantially the same pitch. In this connection structure, as shown in FIGS. 2A and 2B, a large number of electrodes 2 are formed in a row at the edge of the upper surface of the circuit board 1 and cover these electrodes 2. An insulating film 12 is provided, the insulating film 12 is ground until the upper surface of each electrode 2 is exposed, and a metal plating 13 is provided on the exposed upper surface of each electrode 2. It has almost the same structure as the example.

That is, each electrode 2 of the circuit board 1 is formed by etching a copper foil or copper plating provided on the upper surface of the circuit board 1 into a predetermined shape to form a predetermined narrow pitch P, for example, 0, as in the conventional example. The pattern is formed at a pitch of about .25 mm, and the thickness T is formed to be about 30 μm. The insulating film 12 is a plating resist having an insulating property. The insulating film 12 is coated on the circuit board 1 so as to cover the electrodes 2 as shown in FIG. 3A, and is milled or the like as shown in FIG. Thus, the structure is such that the upper surface of each electrode 2 is cut off until it is exposed. Thus, the upper surface of each electrode 2 and the upper surface of the insulating film 12 are formed as flat surfaces with no steps. In this state, as shown in FIG. 3C, the metal plating 13 is formed on the exposed upper surface of each electrode 2.
The metal plating 13 has a two-layer structure composed of nickel plating formed on the electrode 2 and gold plating formed on the nickel plating, and has a total thickness t of about 5 to 6 μm. It is formed much thinner than the thickness T.

When the circuit board 1 and the heat seal 3 are connected to each other, first, as shown in FIG. 2A, each metal plating formed on each electrode 2 of the circuit board 1 is performed. 13, the conductors 5 of the heat seal 3 are positioned so as to face each other.
Is pressed against each metal plating 13. Then, Figure 2
As shown in (b), each of the conductors 5 breaks through an adhesive layer 6 provided between the conductors 5 of the heat seal 3 and slightly covering the lower surface of each of the conductors 5, and each of the conductors 5 and each of the conductors 5 Metal plating 1
3 is conducted. At the same time, the adhesive layer 6 sinks together with the base film 4 of the heat seal 3 and adheres to the upper surface of the insulating film 12 provided on the circuit board 1. Thus, the circuit board 1 and the heat seal 3 are connected in a state where the electrodes 2 of the circuit board 1 and the conductors 5 of the heat seal 3 are conducted through the metal platings 13.

As described above, in this connection structure, the insulating film 12 applied to the circuit board 1 so as to cover the electrodes 2 is provided on the circuit board 1.
Of the circuit board 1 can be formed into a flat surface with no step even if the thickness T of the electrode 2 of the circuit board 1 is large. For this reason,
Even if each metal plating 13 is formed on the upper surface of each electrode 2, a step occurs by the thickness t of the metal plating 13. However, when the thickness t of the metal plating 13 is about 5 to 6 μm, the thickness T ( 3
(Approximately 0 μm), so that it can be made almost flat. For this reason, even when the pitch P of each electrode 2 is as narrow as about 0.25 mm, when connecting each electrode 2 of the circuit board 1 and each conductor portion 5 of the heat seal 3, The sinking of this portion with the base film 4 can be reduced. As a result, the adhesive layer 6 of the heat seal 3 can be securely brought into close contact with the insulating film 12 of the circuit board 1 and bonded.
The electrodes 2 of the circuit board 1 and the conductors 5 of the heat seal 3 can be securely joined together, and the metal plating 13 can also improve the reliability of conduction between the electrodes 2 and the conductors 5. .

In the first embodiment, the circuit board 1
An insulating film 12 is coated on the upper surface of each electrode 2 so as to cover each electrode 2, and the insulating film 12 is shaved until the upper surface of each electrode 2 is exposed, and a metal plating 13 is formed on the exposed upper surface of each electrode 2. Although the respective conductors 5 of the heat seal 3 are joined to the metal plating 13, the metal plating 13 does not necessarily have to be formed. For example, as shown in FIG. The provided insulating film 12 is
May be shaved until the upper surface of the electrode is exposed, and in this state, each electrode 2 and each conductor 5 of the heat seal 3 may be directly joined. In this case, since the upper surface of each electrode 2 of the circuit board 1 and the upper surface of the insulating film 12 are formed on a flat surface without any step, the base film 4 of the heat seal 3 hardly bends, 3 is applied to the insulating film 1 of the circuit board 1.
2 can be more securely brought into close contact with each other, so that each electrode 2 of the circuit board 1 and the heat seal 3
And the respective conductor portions 5 can be securely joined.

[Second Embodiment] Next, FIGS.
A second embodiment of the circuit board connection structure according to the present invention will be described with reference to FIG. In this case, FIG.
The same parts as those of the first embodiment shown in FIGS. This connection structure has a two-layer structure in which each electrode 15 of the circuit board 1 is made up of a conductor pattern 16 and a metal plating 17, and has almost the same structure as that of the first embodiment except for this. That is, as shown in FIG. 5A, the conductor pattern 16 is formed by etching a copper foil or copper plating provided on the upper surface of the circuit board 1 into a predetermined shape, thereby forming a predetermined narrow pitch P, for example, 0.25 mm. The pattern is formed at a pitch of about 30 μm, and the thickness T is formed to about 30 μm.

The metal plating 17 is formed of the conductive pattern 1
6 is nickel-plated on its surface, and has a two-layer structure in which gold is plated on this nickel plating.
The thickness is about 6 μm. Thereby, the electrode 15
Has a two-layer structure including a conductor pattern 16 and a metal plating 17, and is formed to have a total thickness (T + t) of about 35 to 36 μm. Further, on the circuit board 1, FIG.
As shown in FIG. 5A, the insulating film 12 is applied so as to cover each electrode 15, and as shown in FIG. 5B, the upper surface of each electrode 15, that is, the upper surface of the metal plating 17 is exposed by milling or the like. The structure has been cut down to the point. Thus, the upper surface of each electrode 15 and the upper surface of the insulating film 12 are formed as flat surfaces with no steps.

When the circuit board 1 is connected to the heat seal 3, the conductors 5 of the heat seal 3 are opposed to the electrodes 15 of the circuit board 1 as in the first embodiment. Each conductor 5 is pressed against each electrode 15 while heating in this state. Then, as shown in FIG. 5C, each conductor 5 breaks through the adhesive layer 6 provided between the conductors 5 of the heat seal 3 and slightly covering the lower surface of each conductor 5, and each conductor 5 The portion 5 and the metal plating 17 of each electrode 15 conduct. At the same time, the insulating layer 6 of the heat seal 3 is bonded on the insulating film 12 of the circuit board 1. At this time, the upper surface of the electrode 15 and the insulating film 1
2 is formed on a flat surface with no steps,
The base film 4 of the heat seal 3 is hardly bent, and the adhesive layer 6 of the heat seal 3 is closely adhered to the insulating film 12 of the circuit board 1. Therefore, the circuit board 1 and the heat seal 3 are securely connected in a state where the electrodes 15 of the circuit board 1 and the conductors 5 of the heat seal 3 are in conduction.

As described above, in this connection structure, the insulating film 12 applied to the circuit board 1 so as to cover each electrode 15 is shaved until the upper surface of each electrode 2 is exposed. Even if the thickness (T + t) is large, the insulating film 1
By using 2, a flat surface with no steps can be formed. For this reason, even when the pitch P of each electrode 15 is as narrow as about 0.25 mm, when connecting each electrode 15 of the circuit board 1 and each conductor portion 5 of the heat seal 3, the adhesive layer 6 of the heat seal 3 is removed. It can be adhered to the insulating film 12 of the circuit board 1 in close contact. Therefore, each electrode 15 of the circuit board 1 and each conductor 5 of the heat seal 3 can be securely joined,
This makes it possible to obtain a connection with high reliability, and to provide each electrode 15 with the metal plating 17 of each electrode 15.
The reliability of conduction between the conductors 5 and each conductor 5 can also be improved.

In the modification of the first embodiment and the second embodiment, the adhesive layer 6 is provided between the conductors 5 of the heat seal 3 so as to slightly cover the lower surface of each conductor 5. However, the adhesive layer 6 does not necessarily need to be provided so as to cover the lower surface of the conductor portion 5, and may be provided with the same thickness as the conductor portion 5 and with the lower surface of the conductor portion 5 exposed. In addition, the first,
In the second embodiment and its modifications, the case where the circuit board 1 and the liquid crystal display device 10 are connected by the heat seal 3 has been described. However, the present invention is not limited to this, and the present invention can be applied to the case where the circuit boards are connected. it can. Further, the first and second
In the embodiments and the modifications thereof, the connection structure of the circuit board 1 incorporated in the electronic wristwatch has been described. However, the present invention is not limited to this, and is widely applied to electronic devices such as mobile phones, electronic organizers, and mobile personal computers. Can be applied.

[0019]

As described above, according to the present invention, the thickness of each electrode of the circuit board is reduced by shaving the insulating film applied to the circuit board so as to cover each electrode until the upper surface of each electrode is exposed. Even if it is thick, it can be formed on a flat surface with no steps due to the insulating film. Therefore, even if the pitch of each electrode is formed narrow, each electrode of the circuit board and each conductor of the heat seal are connected. Sometimes, the adhesive layer provided between the conductor portions of the heat seal can be securely adhered to and adhered to the insulating film of the circuit board, whereby each electrode of the circuit board and each conductor portion of the heat seal can be bonded. Can be reliably joined, and a highly reliable connection can be obtained.

In this case, by forming a metal plating such as nickel or gold on the upper surface of the plurality of electrodes which are exposed by shaving the insulating film, even if a step is formed by the thickness of the metal plating,
Since the thickness of the metal plating is thinner than that of the electrodes, it can be made almost flat, so that the adhesive layer of the heat seal can be securely adhered on the insulating film of the circuit board. In addition to securely joining each electrode and each conductor of the heat seal, the reliability of conduction between each electrode and each conductor can be enhanced by metal plating. In addition, even if the plurality of electrodes have a structure including a conductor pattern such as copper and a metal plating such as nickel or gold formed on the entire surface of the conductor pattern, the electrode is formed on a flat surface with no steps due to the insulating film. This makes it possible to securely join the electrodes of the circuit board and the conductors of the heat seal, and also enhances the reliability of conduction between the electrodes and the conductors by metal plating. .

[Brief description of the drawings]

FIG. 1 is an external plan view showing a first embodiment of a circuit board connection structure according to the present invention.

2 shows a state in which the circuit board of FIG. 1 is connected to the heat seal, and FIG. 2A is an enlarged view of a main part in a state where the circuit board and the heat seal are viewed from the direction of arrows AA in FIG. Sectional drawing, (b) is an expanded sectional view of the principal part in the state which joined the circuit board and the heat seal.

3A and 3B show a manufacturing process of the circuit board of FIG. 2; FIG. 3A is an enlarged cross-sectional view of a main part showing a state in which electrodes are formed on the circuit board and an insulating film is applied so as to cover these electrodes; , (B)
Is an enlarged cross-sectional view of a main part showing a state in which the insulating film applied over the electrode is shaved until the upper surface of the electrode is exposed, and FIG. 3C shows a state in which metal plating is formed on the upper surface of the exposed electrode. FIG.

FIG. 4 is an enlarged sectional view of a main part showing a modification of the first embodiment.

5A and 5B show a second embodiment of the circuit board connection structure according to the present invention, in which FIG. 5A shows the formation of electrodes made of a conductor pattern and metal plating on a circuit board, and application of an insulating film covering these electrodes; FIG. 4B is an enlarged cross-sectional view of a main part showing a state where the insulating film provided over the electrode is cut off until the upper surface of the electrode is exposed, and FIG. FIG. 3 is an enlarged cross-sectional view of a main part showing a state where a circuit board with exposed electrodes and a heat seal are joined.

6A and 6B show a conventional connection structure of a circuit board, wherein FIG. 6A is an enlarged cross-sectional view of a main part in a state where the circuit board and the heat seal are opposed to each other, and FIG. The expanded sectional view of the principal part in the state which joined.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Circuit board 2, 15 Electrode 3 Heat seal 5 Conductor part 6 Adhesive layer 12 Insulating film 13, 17 Metal plating 16 Conductor pattern

Continued on the front page F term (reference) 5E343 AA02 AA12 AA33 BB09 BB14 BB15 BB16 BB23 BB24 BB44 BB67 BB71 DD32 DD75 EE43 ER49 FF23 GG02 GG06 5E344 AA02 AA22 BB02 BB04 BB10 CC15 CC23 DD08 DD10 DD13 DD17

Claims (3)

[Claims] 1. A circuit board comprising: a plurality of electrodes formed in rows; an insulating film covering the plurality of electrodes; an insulating film applied to the plurality of electrodes; and the insulating film being cut until the upper surfaces of the plurality of electrodes are exposed. And a heat seal provided with a plurality of conductors joined to the plurality of electrodes of the circuit board. 2. The connection structure for a circuit board according to claim 1, wherein metal plating such as nickel or gold is formed on the upper surfaces of the plurality of electrodes exposed by shaving the insulating film. 3. The circuit according to claim 1, wherein the plurality of electrodes are formed of a conductor pattern such as copper and a metal plating such as nickel or gold formed on the entire surface of the conductor pattern. Board connection structure.