JPH06310826A - Mounting structure of electronic component in flexible printed-wiring board - Google Patents

Abstract

PURPOSE:To make it possible to mount an electronic component on an FPC without reducing the thin-walled thickness and flexibility of this FPC and moreover, to contrive a finer formation of the flexible printed circuit and a reduction in the cost of the circuit. CONSTITUTION:Conductor circuits 13 formed on a FPC 10 are formed by a screen printing method and lead wires 14a for an electronic component 14 are respectively connected to the circuits 13 via each conductive bonding agent 15 applied to terminals 13a in a landless state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure for mounting electronic parts such as ICs and FPs (flat pack ICs) on terminals of conductor circuits in flexible printed wiring boards.

[0002]

2. Description of the Related Art FIG. 3 shows a keyboard switch 4 in which a signal is turned on and off by pressing a flexible sheet 1 and touching an electronic component 3 such as an IC mounted on a printed wiring board 2. 1 shows a schematic cross section, and the printed wiring board 2 in this case is a hard substrate type printed wiring board (hereinafter abbreviated as RPC). In this RPC, since the substrate 5 has heat resistance, the conductor circuit 6 formed by etching is connected to the lead wire 3 of the electronic component 3.
The electronic component 3 is mounted by connecting a by soldering. Such an RPC has the advantage of being capable of achieving higher dimensional accuracy and being sufficiently compatible with circuit fineness (miniaturization), but since the substrate is rigid and requires an appropriate thickness, space saving (mainly There are restrictions on thinness and flexibility, and costs are high.

[0003]

Therefore, in order to solve the above problems, a flexible printed wiring board (hereinafter abbreviated as FPC) made of a flexible sheet is being applied to the substrate itself. As a substrate material for this FPC, especially a polyester (hereinafter abbreviated as PET) film is inexpensive, which is advantageous in terms of cost.
Due to its poor heat resistance, it is unavoidable that the mounting part of electronic parts, that is, the connecting part of the lead wire, has a double structure in which it is soldered using the above-mentioned RPC, and the original thinness and flexibility of the FPC are fully demonstrated There is a problem that it is not done. Further, if the conductor circuit of the FPC is formed by the screen printing method, it is more advantageous in terms of cost, but on the other hand, since the dimensional accuracy of the circuit is inferior, there is a limit to the fineness of the circuit. The present invention has been made in view of the above circumstances, and enables mounting of electronic components on an FPC without impairing the thinness and flexibility of the FPC.
Moreover, it is an object of the present invention to provide a mounting structure for electronic components on a flexible printed wiring board, which enables finer circuits and lower costs.

[0004]

The present invention has been made in order to achieve the above object, and has a structure in which an electronic component such as an IC is mounted on a terminal of a conductor circuit formed on a flexible printed wiring board. , The conductor circuit is formed by a printing method, and the end of the conductor circuit is set to a landless state by setting the width of the conductor circuit to be approximately the same as the width of the conductor circuit. It is characterized by connecting wires.

[0005]

According to the present invention, since the electronic component is mounted on the conductor circuit by the conductive adhesive, it is not necessary to use the RPC in the mounting portion to form the double structure, and therefore, the thinness and the flexibility are achieved. Electronic components can be mounted without impairing the property. When the thinning is applied to various devices such as a keyboard switch, downsizing of the entire device can be achieved. Further, since the end of the conductor circuit is in a landless state and the conductive adhesive does not cause dripping or bleeding, it is possible to sufficiently deal with finer circuits.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIGS. These figures show a schematic cross section of a keyboard switch 11 configured by using an FPC 10 to which an electronic component mounting structure according to an embodiment is applied. The FPC 10 is formed by forming a plurality of conductor circuits 13 on the surface of a sheet substrate 12 made of flexible PET or the like, and the conductor circuits 13 are formed by a screen printing method. The conductor circuit 13 in the illustrated portion is in a state in which a plurality of parallel-arranged conductor circuits 13 are abutted to each other with a gap, and the terminals 13a of each pair of abutted conductor circuits 13 are mounted on the mounted IC or FP. Are connected by electronic components 14 such as. The terminal 13a of the conductor circuit 13 is set to have the same width as the conductor circuit 13,
It is in a landless state.

The electronic component 14 is provided with a pair of lead wires 14a which are connectors to the conductor circuit 13, and the lead wires 14a are attached to the terminals 13a of the conductor circuit 13 via a conductive adhesive 15. Connected. In this case, the conductive adhesive 15 is a thermosetting epoxy resin having a viscosity of, for example, about 500 poise and an appropriate amount of Ag filler mixed therein. The keyboard switch 11 is configured by being provided on the FPC 10 having the above configuration so as to cover the flexible sheet 16.

Next, the steps from manufacturing the FPC 10 to mounting the electronic components 14 will be described. First, the conductor circuit 13 is formed on the surface of the sheet substrate 12 by the screen printing method as described above. Then, the conductive adhesive 15 in a wet state is applied to the surface of the terminal 13a of each conductor circuit 13 and the sheet substrate 12 around it, and the lead wire 14a of the electronic component 14 is inserted into the conductive adhesive 15. .
Then, the conductive adhesive 15 is heated at a predetermined temperature for a predetermined time to cure the conductive adhesive 15 and secure the connection state of each lead wire 14a. Since the heating temperature is about 60 ° C., there is no influence on the sheet substrate 12, electronic parts and the like. Then, the sealing resin is applied to the surface of the FPC 10 to complete the process.

According to the FPC 10 of this embodiment, the connection of the lead wire 14a of the electronic component 14 to the conductor circuit 13, that is, the mounting of the electronic component 14 on the FPC 10 is performed.
Since the conductive adhesive 15 is used, it is not necessary to use the RPC for the mounting portion to form a double structure, and therefore, the electronic component 14 can be mounted on the FPC 10 without impairing thinness and flexibility. By thinning the FPC 10 in this way, the overall thickness of the keyboard switch 11 is reduced and downsizing is achieved. Also, when the end of the conductor circuit 13 is in the landless state,
And since the conductive adhesive 15 does not cause bleeding,
It can also be used for finer circuits. Furthermore, since the conductor circuit 13 is formed by the screen printing method and the sheet substrate 12 is made of PET, it can be manufactured at low cost.

[0010]

As described above, according to the mounting structure of the electronic component in the flexible printed wiring board of the present invention, the conductor circuit is formed by the printing method, and
A terminal of the conductor circuit is set to a width similar to that of the conductor circuit to be in a landless state, and a lead wire of the electronic component is connected to the terminal via a conductive adhesive, Since the electronic component is mounted on the conductor circuit by the conductive adhesive, it is not necessary to use the RPC in the mounting portion to form a double structure, and therefore the electronic component can be mounted without impairing the thinness and flexibility. This is possible, and by applying such a thin structure to various devices such as a keyboard switch, downsizing of the entire device can be achieved. In addition, since the end of the conductor circuit is in the landless state and the conductive adhesive does not cause bleeding or bleeding,
It can also be used for finer circuits.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of a keyboard switch using an FPC to which an embodiment of the present invention is applied.

FIG. 2 is a view taken along the line AA of FIG.

FIG. 3 is a partial cross-sectional view of a keyboard switch using a conventional FPC.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Flexible printed circuit board (FPC), 11 ... Keyboard switch, 12 ... Sheet board, 13 ... Conductor circuit, 13a ... Conductor circuit terminal, 14 ... Electronic component, 14a
… Lead wires for electronic parts, 15… Conductive adhesive

Claims (1)

[Claims] 1. A structure in which an electronic component such as an IC is mounted on a terminal of a conductor circuit formed on a flexible printed wiring board, wherein the conductor circuit is formed by a printing method, and the terminal of the conductor circuit is formed on the conductor circuit. A mounting structure for an electronic component on a flexible printed wiring board, characterized in that a lead wire of the electronic component is connected to this terminal via a conductive adhesive, by setting the width to the same level as in the landless state.