JPH08181430A - Bonding method of substrate and electronic circuit - Google Patents

Abstract

PURPOSE: To enhance effect of temporary fixing during bonding and effect of reinforcement of bonded part, to prevent water from entering an electrode part and prevent a defect in insulation from occurring. CONSTITUTION: Before a hard printed substrate 1 and a flexible substrate 2 are connected by solder by laminating electrodes of both parts, circumference of laminated electrodes is enclosed with a pressure sensitive adhesive double coated tape 10 and is adhered. After adhesion by the tape 10, heat is applied to a laminated position so that solder applied to both electrodes before lamination is fused, and both substrates are electrically connected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a substrate bonding method and an electronic circuit.

[0002]

2. Description of the Related Art A hard printed circuit board (hereinafter referred to as PCB) and a flexible substrate (hereinafter referred to as FPC) are connected to each other by directly bonding their electrode portions with solder or a conductive resin. A state in which the PCB and the FPC are bonded together is shown in FIGS. 2 (a) and 2 (b). This is just PCB1
The FPC 2 and the FPC 2 are bonded to each other only by a conductive bonding means such as solder.

An ECU mounted in a vehicle, such as an engine control ECU equipped with an electronic circuit having such a configuration, is often an unfavorable mounting environment for an internal electronic circuit. In particular, when moisture 11 adheres to the connection electrode portion 12 which is a portion where the electrode portions of PCB1 and FPC2 are adhered to each other due to dew condensation or the like, when water enters due to a capillary phenomenon in the gap between PCB1 and FPC2, the difference between PCB1 and FPC2 This may result in poor insulation between the electrodes.

[0004]

As examples of those in which the connecting electrode portions of the PCB and the FPC are directly adhered to each other by using solder, conductive resin or the like, there are JP-A-1-189988 and JP-A-2-12988. Have been disclosed in. The contents disclosed in these publications are as follows.
At the time of connecting the electrodes to the PC, a fixing member such as an adhesive is used in advance to fix the two substrates to position each other, thereby obtaining an effect of temporarily fixing the both substrates. It is a thing. Further, by connecting both electrodes and applying an adhesive to reinforce the connecting portion, it is intended to obtain an effect of preventing damage to the connecting portion due to stress applied to the connected electrode portions.

However, the contents disclosed in these publications also result in infiltration of moisture into the gap between the PCB and the FPC, resulting in poor insulation between the electrode portions, as in the simple connection method described above. Therefore, it is an object of the present invention to prevent the infiltration of water into the electrode portion connecting between both substrates and obtain the effect of preventing insulation failure.

[0006]

In order to solve the above-mentioned problems, the present invention provides a method in which a first substrate and a second substrate are placed between the first and second substrates by superposing electrodes on both substrates. In a method of adhering a substrate which adheres while obtaining a conductive action, a waterproof member having a waterproof effect is provided around a periphery of the electrode in a space formed in a facing surface where the first substrate and the second substrate face each other. A method of adhering a substrate, in which the first electrode and the second electrode are adhered while being surrounded, is provided.

There may be a plurality of the electrodes, and the plurality of electrodes may be collectively surrounded by the waterproof member. The waterproof member may be adhered so as to be composed of an adhesive means such as a double-sided tape. An electronic circuit including a first substrate and a second substrate, wherein electrodes of both the substrates are overlapped with each other and bonded while obtaining first and second conductive effects, the first substrate and the second substrate (EN) An electronic circuit in which a space formed inside the facing surfaces facing each other and containing the adhered first electrode and second electrode inside is shielded from the outside air by a waterproof member having a waterproof effect. is there.

There may be a plurality of the electrodes, the space may include the plurality of electrodes collectively, and the waterproof member may collectively shield the plurality of electrodes from outside air. The waterproof member may be configured by an adhesive means such as a double-sided tape.

[0009]

According to claim 1 of the present invention having the above-mentioned structure, a waterproof effect is provided around the electrodes in the space formed in the facing surfaces where the first substrate and the second substrate face each other. According to claim 4 of the present invention having the above-mentioned structure in which the first electrode and the second electrode are adhered while being surrounded by a waterproof member, the first substrate and the second substrate face each other. A space formed inside and containing the adhered first electrode and second electrode inside is shielded from the outside air by a waterproof member having a waterproof effect.

[0010]

EXAMPLE An example of a substrate bonding method to which the present invention is applied will be described below. 1A and 1B are a plan view and a sectional view showing a first embodiment of the present invention. The electronic circuit shown in this embodiment in (a) of FIG. 1 includes a rigid printed circuit board (PCB) 1 that cannot be bent,
Flexible substrate (FPC) that can be bent 2
And a connection electrode portion 12 connecting both electrode portions so that both substrates are formed as an integrated electronic circuit.

The FPC 2 is attached to the base film 8 serving as the base of the substrate, the copper pattern 7 forming the pattern of the electronic circuit on the base film 8, and the copper pattern 7 for protecting the copper pattern 7. And a coverlay film 6. The coverlay film 6 is PCB1
An opening is provided in a portion that serves as a connection portion between the copper pattern 7 and the copper pattern 7, and the copper pattern 7 is partially exposed to form a part of the connection electrode portion 12.

On the other hand, the PCB 1 includes a base material 3 which serves as a base of the substrate and a copper pattern 4 formed on the base material 3.
And a solder resist 5 attached on the copper pattern 4 to protect the copper pattern 4. Also PCB
As in the case of No. 1, the solder resist 5 has an opening at a portion which becomes a connection portion with the copper pattern 4,
Are partially exposed to form a part of the connection electrode portion 12.

Both electrodes are provided at an equal pitch,
Both boards are electrically connected by stacking the respective copper patterns and positioning both boards and then welding them with solder. Solder is previously welded to each electrode of PCB1 and FPC2 before PCB1 and FPC2 are connected. When connecting both substrates, the electrodes are overlapped and a heat source for melting the solder such as a heater bar from the outside. Apply from outside and connect.

As a feature of the present invention, as shown in FIG. 1 (b), when the electrodes of both substrates are superposed, either the PCB1 or the FPC2 substrate is surrounded so as to surround the connection electrode portion. A double-sided adhesive tape 10 is attached to the.
Next, a procedure for assembling the thus constructed substrate will be described. After positioning so that the electrodes of PCB1 and FPC2 are aligned with each other, the double-sided tape 10 is
1 and FPC2 are attached so as to surround the electrodes,
2 and PCB1 are temporarily fixed.

Thereafter, the connecting electrode portion 12 is heated from the outside by using a heater bar. At this time, the solder that had been adhered to both electrode surfaces in advance melts, and the FPC2 and PC
The electrode with B1 is adhered, and both substrates are electrically connected as the connection electrode portion 12. As described above, FPC2 and P
Double-sided adhesive tape 1 around the connecting electrode portion 12 with CB1
By connecting in a state of being bonded with 0, the connection electrode portion 12 is shielded from the outside air, and it is possible to prevent water droplets from adhering to the connection electrode portion 12. Then, before fixing the substrates to each other, the electrodes are overlapped with each other and temporarily fixed with a double-sided adhesive tape.
Since the electrodes as disclosed in Japanese Patent No. 2988 can be soldered without being displaced from each other and the periphery of the connection electrode portion 12 is fixed even after the substrate is connected, the connection electrode portion 1
A reinforcing effect for protecting 2 is also obtained.

Although the double-sided adhesive tape 10 is used in the embodiment, the connection electrode portion 12 may be surrounded by a resin such as an adhesive as long as a waterproof effect can be obtained, and the invention is not limited to the double-sided adhesive tape 10. Further, as in the above-described embodiment, the electrodes are thermocompression bonded without temporarily fixing them with the double-sided adhesive tape 10, and the entire substrate is subsequently dipped in a moistureproof agent, so that the connection electrode portion 12 is replaced with the double-sided adhesive tape 10. A moistureproof agent can be attached to the surroundings, and the waterproof effect of the connection electrode portion 12 can be obtained.

[0017]

According to the present invention, the effect of preventing insulation failure can be obtained by blocking the electrode from the outside air by the waterproof member and preventing the intrusion of water droplets.

[Brief description of drawings]

FIG. 1 is a diagram showing an adhesion state of a flexible printed circuit board and a hard printed circuit board according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of adhesion between a conventional flexible board and a rigid printed board.

[Explanation of symbols]

 1 Hard Printed Circuit Board 2 Flexible Board 3 Base Material 4 Copper Pattern (for Hard Printed Circuit Board) 5 Solder Resist (for Hard Printed Circuit Board) 6 Coverlay Film (for Flexible Board) 7 Copper Pattern (for Flexible Board) 8 Base Film 10 Both Sides Adhesive tape 11 Moisture 12 Connection electrode part

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Koji Kondo, 1-1, Showa-cho, Kariya city, Aichi prefecture, Nihon Denso Co., Ltd. (72) Inventor, Takatsugu Kamiya, 1-1, Showa-cho, Kariya city, Aichi prefecture Sozo Co., Ltd.

Claims (6)

[Claims] 1. A method of adhering a first substrate and a second substrate, which comprises adhering electrodes on both substrates to each other while obtaining a conductive action between the first and second substrates, the method comprising the steps of: The first electrode and the second electrode are adhered while surrounding the electrode in a space formed in the facing surface where the substrate and the second substrate face each other with a waterproof member having a waterproof effect. Substrate bonding method. 2. The method for adhering a substrate according to claim 1, wherein a plurality of the electrodes are present, and the plurality of electrodes are collectively surrounded by the waterproof member. 3. The method for adhering a substrate according to claim 1, wherein the waterproof member is an adhering means such as a double-sided tape. 4. An electronic circuit comprising a first substrate and a second substrate, wherein electrodes of both the substrates are overlapped and bonded while obtaining first and second conductive effects, wherein the first substrate An electronic circuit in which a space formed between the first substrate and the second substrate, which are formed in the facing surfaces facing each other, and which includes the bonded first electrode and second electrode inside is shielded from the outside air by a waterproof member having a waterproof effect. . 5. The electronic circuit according to claim 4, wherein there are a plurality of the electrodes, the space collectively includes the plurality of electrodes, and the waterproof member collectively blocks the plurality of electrodes from outside air. 6. The electronic circuit according to claim 4, wherein the waterproof member is an adhesive means such as a double-sided tape.