JP3454013B2 - Terminal connection method for flexible printed circuit boards - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for connecting terminals to a flexible wiring board having a conductive pattern formed on a resin film.

[0002]

2. Description of the Related Art In recent years, electronic parts used in electronic equipment have been made smaller and thinner, and flexible wiring boards are often used to make these electronic parts smaller and thinner. It's getting more and more.

This flexible wiring board has a conductive pattern formed on the basis of various resin films.
It is classified into the following two types depending on the method of forming the conductive pattern.

The first is a substrate in which a copper foil is adhered on a resin film to form a conductive pattern by etching, and the second is a screen printing of a conductive paste such as silver paste on the resin film. Then, a conductive pattern is formed, and generally, a conductive pattern is formed by screen-printing a conductive paste such as a second silver paste because of its low manufacturing cost.

However, since this conductive pattern contains a large amount of resin component in addition to metal powder, it is difficult to directly solder it, and even if soldering is possible, there is a problem that the soldering strength is very low.

In order to solve this problem, a method is employed in which a metal terminal is electrically and mechanically fixed to a conductive pattern of a connecting portion of a flexible wiring board and the metal terminal is soldered. As a method for fixing the conductive pattern of the connecting portion and the metal terminal for this purpose, as disclosed in Japanese Patent Laid-Open No. 5-21097, a method of crimping the metal terminal to the connecting portion can be considered, but the mechanical strength is weak and the terminal is weak. Not only is the rattling likely to occur, but when crimping the film is deformed and cracks or disconnections occur in the printed conductive pattern, resulting in an increase in connection resistance and contact instability. After crimping the metal terminal to the connection part, it was electrically and mechanically reinforced with a conductive adhesive.

[0007]

However, in the above method, since it is necessary to reinforce with a conductive adhesive, not only equipment for coating / drying / curing is required, but also the process is complicated. Since the cost is increased and it is necessary to apply the conductive adhesive so as to wrap the crimped portion of the terminal, there is a limit to reduction in thickness.

The present invention solves these problems and is a cheap and thin flexible wiring board that does not cause rattling of terminals even if it is not reinforced with a conductive adhesive and has excellent mechanical strength and electrical connection stability. It is an object of the present invention to provide a method for connecting terminals.

[0009]

In order to solve the above problems, the present invention provides a flexible wiring board with a soft polyester.
To form a conductive pattern in Le resin binder and the conductive paste, crowded defeat caulking portion of the metal terminal both sides to face the upright terminal side connected soldered of the conductive pattern on the inside, the conductive pattern caulked at embracing form, the inside of the caulking portion is intended to be connected by bite into the conductive pattern.

As a result, the connection can be made at a low cost, the terminal backlash does not occur even if the conductive adhesive is not reinforced, and the mechanical strength can be secured, so that the device can be made thin and stable electrical connection can be secured . Half the terminal side of the above metal terminals
Due to the heat transmitted to the metal terminals when attaching the rice,
Increased stability of electrical connection between metal terminal and conductive pattern
It can be something.

[0011] According to a first aspect of the present invention, polyether glass transition temperature of ordinary temperature (23 ° C.) or less as a binder
A conductive pattern formed on a flexible wiring board by a conductive paste using a stell resin and silver powder as a conductive powder.
The metal terminal to which the terminal side is soldered and connected.
The kick metal terminal crimping portion stood in opposition to either side of the conductive pattern, crowded tilted inward so as to embrace the conductive pattern, and the metal terminal crimping unit side and caulking method by bite into the conductive pattern Since there is no backlash of the terminals without reinforcement with conductive adhesive,
It has strong mechanical strength and can secure a stable electrical connection.
In both cases, the electrical connection is secured by soldering the terminals of the metal terminals.
It has an effect that a thin terminal connection method with increased qualitativeness can be provided at low cost.

According to a second aspect of the invention, in the first aspect of the invention, the conductive pattern of the terminal connecting portion has a thickness of 10
The thickness of the terminal connection resistance value can be further reduced, and at the same time, the stability of the connection resistance value after soldering to the terminal can be improved.

[0013]

According to a third aspect of the present invention, in the invention according to the first aspect, the direction of the burr at the time of punching the metal terminal is the inner side surface of the caulking portion, and the electrical connection stability is improved. Has the effect of being able to increase.

[0015] The invention according to claim 4, in <br/> invention of claim 1, wherein the binder of the conductive paste and the polyester resin having a heater <br/> Toshiru of the metal terminal, the metal
After the terminals have been crimped,
The heat transferred to the metal terminals during soldering causes the metal
Since the terminal and the conductive pattern are adhered , and the metal terminal and the conductive pattern are adhered to each other after soldering to the metal terminal, the airtightness of the connection portion is increased and the reliability of the connection is improved.

An embodiment of the present invention will be described below with reference to FIGS. 1 to 4 and (Table 1) by taking a resistor for a rotary variable resistor as an example.

FIG. 1 is a plan view showing a state in which metal terminals are connected to a resistor for a rotary variable resistor to which the method for connecting terminals of a flexible wiring board according to the embodiment is applied. FIG. 2 is a plan view of the resistor. 3 (a) is a plan view of the metal terminal, FIG.
Is a side view of the same.

In the figure, the resistor 1 has a thickness of 188 μm.
Various patterns 1b and 1 by screen printing on the polyester resin film 1a (made by Toray: Lumirror H10)
c, 1d is a flexible wiring board on which 1
b is a resistance pattern formed of a conductive paste using carbon as a conductive powder for the phenol resin binder, 1c is a derived pattern formed of a conductive paste using silver powder as a conductive powder for the phenol resin binder, and 3d are 1d Is a conductive pattern formed by a conductive paste using a polyester resin (Vylon 300 manufactured by Toyobo Co., Ltd.) having a glass transition temperature of 7 ° C. as a binder and silver powder (TCG-1 manufactured by Tokuriki Kagaku) as conductive powder. Yes, its thickness is 15 μm to 2
It is 0 μm. Then, terminal holes 1e for inserting the caulked portions 2a of the metal terminals are provided at opposing positions on both sides of each of the conductive patterns 1d.

On the other hand, the metal terminal 2 is pressed from a direction such that the burrs of the two caulking portions 2a provided so as to be opposed to the ends thereof are opposed to each other, and at the same time, the two caulking portions 2a are pressed. The inner surface is provided with the uneven portion 2b.

As a method for connecting the metal terminal 2 to the resistor 1, the metal terminal caulking portions 2a are inserted into the terminal holes 1e from below, and the metal terminal caulking portions 2a standing opposite to both sides of the conductive pattern 1d are provided. Film 1a and conductive pattern 1d
Crowded tilted to the inside prejudiced bets in the conductive pattern 1d metal terminals crimped portion 2a inside surface as shown in the sectional view of FIG. 4
It is something that is caulked by being cut into.

In this way, by adopting the crimping method in which the substrate film 1a is held by the metal terminal crimped portion 2a, there is no rattling of the terminal and sufficient mechanical strength can be obtained. Further, the escape of the substrate film 1a disappears, the portion of the conductive pattern 1d of the substrate film 1a is deformed along the terminal caulking portion 2a, the connection area between the conductive pattern 1d and the terminal caulking portion 2a increases, and the connection resistance value is increased. Get lower.

Here, there is a concern that mechanical stress due to caulking may be applied to the end 1f of the conductive pattern 1d to cause cracks and increase the connection resistance value, but the glass transition point is below room temperature (7 ° C.). Since the flexible conductive pattern 1d using the soft resin as a binder is used, the occurrence of cracks is suppressed and a low connection resistance value is obtained.

Further, when the metal terminal 2 connected to the resistor 1 is soldered by using a soldering iron, the heat of the soldering iron is transmitted through the metal terminal 2 and the inside of the metal terminal caulking portion 2a.
Conductive pattern 1d using the above polyester resin as a binder
Softens. As a result, the conductive pattern 1d and the metal terminal 2
The contact area with and increases, and the connection resistance value further decreases. Furthermore, since the polyester resin having heat sealability is used for the metal terminal 2, the metal terminal 2 and the conductive pattern 1d are adhered to each other at the time of soldering, so that the airtightness of the connection surface is increased and the connection reliability is improved. Will increase.

Here, the results of evaluating the characteristics of each sample of the resistor 1 produced by using several kinds of binders of the conductive paste are shown in Table 1.

[0025]

[Table 1]

In the table, if the connection resistance value is less than 1 Ω, it can be said that the connection has no electrical problem in actual use. However, as shown in (Table 1), the conductive pattern 1d has a thickness of 10 μm. In the above case, the connection resistance value is less than 0.1Ω, and the connection is more stable.

The film to be used is not limited to the polyester film, and examples thereof include glass epoxy substrate, polyethylene naphthalate, polyphenylene sulfide, polyether imide, polyimide, and the like.
Resin films having various thicknesses such as polyether ether ketone and polyether sulfone can be used.

[0028]

As described above, according to the present invention, the terminal side is
Connect the metal terminals to be soldered to the flexible wiring board
It is possible to obtain a thin and inexpensive connection to a conductive pattern, which has excellent mechanical strength, electrical connection stability, and reliability even without reinforcement of a conductive adhesive.
The terminal part of the metal terminal fixed by crimping on the wiring board.
By soldering, the metal terminals and the conductive patterns
It is possible to provide a method of connecting terminals to a flexible wiring board, which improves the electrical connection stability between terminals.

[Brief description of drawings]

FIG. 1 is a plan view showing a state in which a metal terminal is connected to a resistor for a rotary variable resistor to which a flexible wiring board terminal connecting method according to an embodiment of the present invention is applied.

FIG. 2 is a plan view of the resistor.

FIG. 3 (a) is a plan view of the same metal terminal. (B) Side view

FIG. 4 is a sectional view taken along line XX of FIG.

[Explanation of symbols] 1 resistor 1a film 1b resistance pattern 1c Derivation pattern 1d conductive pattern 1e Terminal hole 1f Conductive pattern end 2 metal terminals 2a Caulking part 2b uneven part

─────────────────────────────────────────────────── --- Continuation of front page (56) References JP-A-4-28108 (JP, A) JP-A-6-333618 (JP, A) JP-A-7-153522 (JP, A) JP-A-54- 78491 (JP, A) Actual Kaihei 6-9167 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01R 9/09 H01C 17/28 H05K 1/18 H05K 3/32

Claims (4)

(57) [Claims] 1. A polyester resin having a glass transition temperature of room temperature (23 ° C.) or lower as a binder and silver as a conductive powder.
Solder the terminal side to the conductive pattern formed on the flexible wiring board with the conductive paste using powder
In the metal terminal to be connected, the metal terminal caulking portions that are erected on both sides of the conductive pattern are placed on the conductive pattern.
Crowded tilted inward so as to entertain, terminal connecting method of the flexible printed circuit board in which the inner surface of the metal terminal crimping portion caulked so by bite into the conductive pattern. 2. The thickness of the conductive pattern of the terminal connecting portion is 10
The terminal connection method for a flexible wiring board according to claim 1, wherein the terminal connection is not less than μm. 3. The terminal connecting method for a flexible wiring board according to claim 1, wherein the direction of the burr at the time of punching the metal terminal is the inner side surface of the caulking portion. 4. A binder of a conductive paste for forming a conductive pattern is a polyester resin having heat sealability on a metal terminal, and the metal terminal after the metal terminal is fixed by caulking.
When soldering the terminal side of the above metal terminals, transfer it to the above metal terminals.
The metal terminal and the conductive pattern are bonded by the heat
The method for connecting terminals of a flexible wiring board according to claim 1 .