JP2001084862A - Surge absorbing structure and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surge absorbing structure capable of being mass-produced by an inexpensive printing method or the like. SOLUTION: A plurality of conductive ink 12a, 12b, 12c is printed on a substrate 11 to form conductive leads. A first resist 13 is printed on the whole body except portions to be connected by surge absorbing ink 16. The ink 16 is printed on a plurality of places so that the ink 12a, 12b forming a pair and including portions not printed with the resist 13 in the preceding process is connected to each other. Similarly, the ink 16 is printed on a plurality of places so that the ink 12 forming another pair can be connected to each other. A second resist 14 is printed over the whole surface to electrically insulate a surface of a membrane switch, thus forming a surge absorbing structure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a surge absorbing structure and a method of manufacturing the same, and more particularly to a surge absorbing structure which can be mass-produced at low cost and a method of manufacturing the same.

[0002]

2. Description of the Related Art FIGS. 12 to 14 show a conventional membrane switch.

A plurality of conductive leads a, b,... Are formed on a polyethylene terephthalate (PET) sheet 31 serving as a flexible substrate of the membrane switch 100. Then, as shown in FIG. 14, the upper surface of the conductive ink 34 forming the conductive leads a, b, etc. is placed at the connector insertion portion connected to the circuit board of the electric appliance via a socket (not shown). Insulate the resist 36 so as to cover it.
Is applied.

On the other hand, as shown in the sectional view of FIG. 13, the switch section has a conductive contact c formed on a PET sheet 32 which is a flexible sheet. The surface of the PET sheet 32 on which the conductive leads a, b, etc. are formed,
The spacer 30 is disposed so as to face the surface of the PET sheet 32 on which the conductive contact c is formed. Therefore, in the normal state, the conductive leads a, b and the like do not contact the contact c, but when the contact c is pressed, for example, the contact c comes into contact with the conductive leads a, b, and via the contact c. As a result, the conductive leads a and b conduct, and an electric circuit is formed to perform the switching function.

The above-mentioned membrane switch is used as a touch key of an electric appliance such as a button of a portable telephone or a key of a card type calculator. Such switch parts of electric appliances are becoming thinner and smaller with the operation panel.
The possibility of receiving static electricity from a person or the like during the pressing operation is increasing. This static electricity causes a surge in which the current or voltage of the electric circuit instantaneously increases greatly, which may damage the circuit board.

Normally, when the product specifications are satisfied without providing the surge absorbing structure, the cost is reduced without providing the surge absorbing structure. However, whether or not the specifications actually meet the specifications is confirmed by conducting a trial manufacture and a test. Therefore, even when it is determined that the surge absorbing structure is unnecessary at the design stage, a surge absorbing structure must be provided after the test.

On the other hand, the above-mentioned membrane switch includes:
Since protection against surge is not provided, protection measures are required for the circuit board connected thereto.

[0008]

However, when a circuit board is to be protected against a surge, a space for mounting a surge absorbing element on the circuit board side is required. This space may be provided in advance, but usually, no unnecessary space is provided on the circuit board due to a demand for miniaturization of the device.

Therefore, in order to mount a new surge absorbing element, it is necessary to change the layout of the elements on the circuit board. With this layout change, it is necessary to change the pattern on the circuit board (so-called artwork change). For this reason, there has been a problem that complicated work must be performed for each of the products after the test.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and it is an object of the present invention to form a surge absorbing structure in an electric device such as a membrane switch in advance by a simple method such as printing so that mass production is possible. Aim.

[0011]

In order to solve the above-mentioned problems, a surge absorbing structure according to the present invention has the following features.

(1) In an electric device in which a plurality of conductive leads are arranged, an insulating layer for insulating between the conductive leads, and an insulating layer formed on the insulating layer, when a surge voltage is applied. And a surge absorbing ink layer for electrically connecting the conductive lead to which the surge voltage is applied and another conductive lead.

The conductive leads are connected by using a surge absorbing ink which does not conduct at a normal operating voltage and which flows a current for the first time when a surge voltage is applied. Conductive leads and other conductive leads can be conducted through the surge absorbing ink layer. As a result, even if a surge voltage is applied to one conductive lead due to static electricity, the conductive lead is conducted to another conductive lead, and the potential difference between the two conductive leads can be eliminated. Therefore, since no surge voltage is applied to the circuit board, there is no risk of damaging the circuit board.

(2) In the surge absorbing structure according to the above (1), the surge absorbing ink layer may further include any two of
This is a surge absorbing structure formed at a plurality of different positions so as to allow conduction between more than one conductive lead.

According to the above configuration, it is possible to independently conduct any two or more conductive leads. Therefore, when a surge voltage is applied, the potential difference can be eliminated by conducting the conductive voltage with the conductive lead paired with the conductive lead to which the surge voltage is applied. Thus, there is no possibility that a surge voltage is applied to the circuit board.

(3) The surge absorbing structure according to the above (1) or (2), further comprising a surface insulating layer covering the entire surface of the insulating layer and the surge absorbing ink layer.

The surge absorbing structure can be electrically insulated from others by the surface insulating layer.

(4) In the membrane switch in which a plurality of conductive leads are arranged, one of the conductive leads is a ground terminal, and the other conductive lead is capable of inputting an electric signal. An input terminal, an insulating layer for insulating between the ground terminal and each input terminal, and formed on the insulating layer, and when a surge voltage is applied, any input terminal to which a surge voltage is applied and the ground A surge absorbing structure of a membrane switch having a surge absorbing ink layer formed at a plurality of different positions so that terminals can be conducted.

According to the above configuration, the ground terminal and the arbitrary input terminal can be independently conducted. Therefore, when a surge voltage is applied, the conductive lead connected to the input terminal to which the surge voltage is applied is connected to a conductive lead to eliminate a potential difference. Thus, there is no possibility that a surge voltage is applied to the circuit board.

(5) The surge absorbing structure for a membrane switch according to the above (4), further comprising a surface insulating layer covering the entire surface of the insulating layer and the surge absorbing ink layer.

The surge absorbing structure can be electrically insulated from the others by the surface insulating layer.

Further, a cable according to the present invention has the surge absorbing structure according to any one of the above (1) to (3).

In the method for manufacturing a surge absorbing structure according to the present invention, a step of applying a first resist to insulate between conductive ink applied to a substrate for forming conductive leads is provided. Applying a surge absorbing ink that can conduct when a surge voltage is applied between any conductive leads on which the first resist is not applied in the first resist applying step; Applying a second resist so as to cover the entire surface of the attached first resist and surge absorbing ink.

According to the above manufacturing method, the surge absorbing structure can be mass-produced at low cost by, for example, printing.

In the membrane switch and the cable according to the present invention, the surge absorbing structure is formed by using the method for manufacturing a surge absorbing structure described in (8).

[0026]

Embodiments of the present invention will be described below with reference to the drawings. Note that the same components as those of the above-described conventional membrane switch are denoted by the same reference numerals, and description thereof will be omitted.

Embodiment 1 A configuration in which the surge absorbing structure of the present embodiment is mounted will be described using a membrane switch as an example. FIG. 1 shows a schematic view of a membrane switch. FIG. 2 shows an enlarged view of the connector insertion portion 18 of the membrane switch 10.

As shown in FIG. 2, a plurality of conductive inks 12 serving as conductive leads are formed on a substrate at intervals by applying means such as printing. In the present embodiment, silver carbon ink is used as the conductive ink 12. A surge absorbing layer is formed on the plurality of conductive inks 12 to enable conduction between any two or more conductive inks 12 when a surge voltage is applied.
This surge absorbing layer is formed by printing the surge absorbing ink 16 or the like. Further, a surface insulating layer for insulating the surface of the membrane switch is formed on the entire upper surface thereof. In the present embodiment, a resist 14 generally used as insulation is used as a surface insulating layer.

Further, the surge absorbing structure of the present embodiment will be described in detail with reference to FIG. 3 showing a BB section of FIG. 2 and FIG. 4 showing a CC section.

As shown in FIG. 3, a conductive ink 12a, 12b, 1 is provided on a substrate 11 made of, for example, a PET sheet.
2c is formed as a conductive lead. The upper surface of the conductive ink 12a and the upper surface of the conductive ink 12b are connected by a surge absorbing ink 16 so as to be conductive at the time of a surge voltage. On the other hand, the side of the conductive ink 12a and the side of the conductive ink 12b, and the side of the conductive ink 12b
And the conductive ink 12c are insulated by the insulating ink made of the first resist 13. Then, the conductive inks 12a, 12b, 12c,...
On the upper surface of the surge absorbing ink 16, a second resist 14 which is a surface insulating layer is applied so as to cover the entire surface.

Similarly, as shown in FIG.
A conductive ink 12a, 1 is provided on a substrate 11 made of a sheet.
2b and 12c are formed as conductive leads. The upper surface of the conductive ink 12a and the upper surface of the conductive ink 12c are
The surge absorbing ink 16 is connected so as to be conductive at the time of a surge voltage. On the other hand, the conductive ink 12a
And the conductive ink 12b, and the conductive ink 12b and the conductive ink 12c are insulated by the insulating ink made of the first resist 13. .., The first resist 13 and the upper surface of the surge absorbing ink 16 are coated with a second resist 14, which is a surface insulating layer, so as to cover the entire surface of the conductive inks 12a, 12b, 12c,.

Next, a method of manufacturing the surge absorbing structure according to the present embodiment will be described with reference to FIGS. 5A to 5C, taking a membrane switch as an example.

As shown in FIG. 5A, a plurality of conductive inks 12a, 12b, and 12c are printed on the substrate 11 to form conductive leads. Next, FIG.
As shown in (b), the first resist 13 is printed on the entire surface except for the portion connected with the surge absorbing ink 16. Next, as shown in FIG. 5C, surge absorption is performed so as to connect the pair of conductive inks 12a and 12b in the portion where the first resist 13 is not printed in the previous step. The ink 16 is printed at a plurality of positions. Similarly, so that the other conductive inks 12 can be connected to each other.
The surge absorbing ink 16 is printed at a plurality of different positions. Then, the second resist 14 is printed on the entire surface to insulate the surface of the membrane switch.

Accordingly, the surge absorbing structure can be mass-produced at low cost by using the printing method generally used for forming the conductive lead of the membrane switch.

In the present embodiment, the manufacturing method using the above-described printing method has been described. However, the present invention is not limited to this, and any coating method may be used as long as each ink or resist can be applied. May be used.

Next, the function of the surge absorbing ink 1 will be described with reference to FIGS.

The structure of the connector insertion portion 18 shown in FIG.
As shown in FIG. 2, a ground terminal 20 (hereinafter referred to as “GND terminal 20”) and an input terminal 22 formed of, for example, conductive ink are formed on a substrate 11 and a GND terminal 2 is formed.
When 0 and the input terminal 22 to the IC are connected by the surge absorbing ink 16, an electric circuit configuration as shown in FIG. 7 is obtained.

The main cause of the surge is static electricity as described above. Normally, no discharge occurs between the GND terminal 20 and the input terminal 22. Therefore, when a surge is applied to the input terminal 22, for example, a large voltage may be applied to the circuit board, and if the large voltage exceeds the rating of the circuit board even instantaneously, the circuit board may be broken. Need arises.

Therefore, the surge absorbing ink 16 used in the present embodiment is made of an ink obtained by mixing aluminum or copper oxide balls with a binder. The binder is a material similar to a PET sheet used as a substrate of a membrane switch, a diluent, an adhesive, or the like. Therefore, it is easy to include the surge absorbing ink 16 in the printing process already existing in the manufacturing process of the membrane switch, and it is possible to reduce the surge without adding any special processing and without having to secure an extra space. This can be prevented. Here, since the metal oxide balls in the surge absorbing ink 1 are normally in contact with each other, when a high voltage such as a surge voltage is applied, the oxide layer of the metal oxide ball does not conduct electricity, and therefore, a spark ( Discharge), thereby absorbing surge. The spark here is
It does not involve abrupt voltage fluctuations, but is close to a state in which a current simply flows. Further, the GND terminal 20 and the input terminal 2 are connected via a metal oxide ball in the surge absorbing ink 16.
When a current flows between the two terminals, the potential difference between the two terminals is eliminated, so that the surge can be absorbed. Note that, when a current flows between the two terminals, the electric circuit is closed in FIG. 7, so that an ON signal current flows to the circuit board. However, by providing a filter in the circuit board that does not operate with a short ON signal current,
Even if the electric circuit is closed due to the surge voltage, the circuit board does not malfunction.

The surge voltage due to static electricity has a waveform as shown by the thin line in FIG. 9, and the potential difference between the two terminals disappears even if the surge absorbing structure is not adopted. However, in order to prevent a large voltage from being applied to the circuit board even at the moment, for example, when a surge is applied to the input terminal 22 in FIG. The voltage can be reduced like the A voltage shown by the thick line. As shown in FIG. 8, when the voltage A is the trigger voltage, as shown by the current B, a spark occurs between the metal oxide balls in the surge absorbing ink, and the current starts to flow in the surge absorbing ink. Decrease. Here, the term “clamp” refers to maintaining a voltage at which a surge is suppressed. This clamp voltage is due to the characteristics of the surge absorbing ink. Therefore, when the current flows and the surge voltage decreases, the voltage A returns to the original voltage.

FIG. 10 shows a comparison of the capacitance between the surge absorbing ink used in the present embodiment and varistors and diodes as other surge absorbing elements.

As shown in FIG. 10, the surge absorbing ink has a much smaller electrostatic capacity than other surge absorbing elements, so that the signal is not distorted compared to other surge absorbing elements and can be used for high-speed communication lines. Can be applied.

Embodiment 2 FIG. 11 shows a flat flexible cable (hereinafter, “FFC”) that electrically connects two electronic control units 1 and 2 (hereinafter, referred to as “ECU”).
Cable "). The surge absorbing structure described in the first embodiment can be formed in this FFC cable. That is, the FFC cable has a plurality of conductive leads, and the conductive leads to be paired are connected by surge absorbing ink, and the conductive leads are insulated from each other. A surge absorbing structure can be formed. The surge absorbing structure may be located at any position on the FFC cable.

Thus, even if a surge voltage is applied to the FFC cable due to, for example, static electricity, there is no possibility that a large voltage is applied to the ECUs 1 and 2.

[0045]

As described above, according to the surge absorbing structure of the present invention, even if a surge voltage is applied to an electric device by static electricity, for example, the surge voltage is immediately absorbed and the electric device is connected. There is no possibility that a large voltage is applied to the circuit board or the like.

Further, the surge absorbing ink for connecting the pair of conductive leads can be formed by an inexpensive printing process, and the surge absorbing structure can be mass-produced. Therefore, there is an advantage that the complicated work of changing the artwork of the surge absorbing element to the circuit board and incorporating the surge absorbing element in the circuit board as in the related art can be omitted.

[Brief description of the drawings]

FIG. 1 is a diagram showing an outline of a membrane switch having a surge absorbing structure according to the present invention.

FIG. 2 is an enlarged view of a portion A of the connector insertion portion 18 of FIG.

FIG. 3 is a sectional view taken along line BB of FIG. 2;

FIG. 4 is a sectional view taken along line CC of FIG. 2;

FIG. 5 is a diagram illustrating a method of manufacturing a surge absorbing structure according to the present invention.

FIG. 6 is another enlarged view of a portion A of the connector insertion portion 18 of FIG.

FIG. 7 is an electric circuit diagram of the connector insertion section shown in FIG.

FIG. 8 is a diagram illustrating a surge voltage absorption state by the surge absorption structure according to the present invention.

FIG. 9 is a diagram showing a decrease in surge voltage due to the surge absorbing structure according to the present invention.

FIG. 10 is a comparison diagram of capacitance between a conventional surge absorbing element and a surge absorbing ink.

FIG. 11 is an FF using the surge absorbing structure according to the present invention.
It is a figure which shows the example of a connection of C cable.

FIG. 12 is a diagram showing an outline of a conventional membrane switch.

13 is a sectional view taken along line AA of FIG.

FIG. 14 is a sectional view taken along line BB of FIG.

[Explanation of symbols]

10 membrane switch, 12, 12a, 12b, 1
2c conductive ink, 13 first resist, 14 second
Resist, 15 switch section, 16 surge absorbing ink, 18 connector insertion section.

Claims (8)

[Claims] An electric device in which a plurality of conductive leads are arranged, an insulating layer for insulating between the conductive leads, and an insulating layer formed on the insulating layer and being provided when a surge voltage is applied. ,
A surge absorbing structure, comprising: a surge absorbing ink layer that connects a conductive lead to which a surge voltage has been applied and another conductive lead in a conductive manner. 2. The surge absorbing structure according to claim 1, wherein the surge absorbing ink layer is formed at a plurality of different positions so that any two or more conductive leads can be conducted. Surge absorption structure characterized by the following. 3. The surge absorbing structure according to claim 1, further comprising a surface insulating layer covering all surfaces of the insulating layer and the surge absorbing ink layer. 4. A membrane switch in which a plurality of conductive leads are arranged, wherein one of the conductive leads is a ground terminal, and the other conductive lead is an input capable of inputting an electric signal. A terminal, an insulating layer for insulating between the ground terminal and each input terminal, and formed on the insulating layer, when a surge voltage is applied,
A surge absorption structure for a membrane switch, comprising: a surge absorption ink layer formed at a plurality of different positions so that an arbitrary input terminal to which a surge voltage is applied and the ground terminal can conduct. 5. The surge absorbing structure for a membrane switch according to claim 4, further comprising a surface insulating layer covering all surfaces of said insulating layer and said surge absorbing ink layer. . 6. A cable having the surge absorbing structure according to claim 1. 7. A step of applying a first resist to insulate between conductive ink applied to a substrate for forming a conductive lead, and a step of applying a first resist in the first resist applying step. A step of applying a surge absorbing ink that can be conducted when a surge voltage is applied between the upper surfaces of any conductive leads to which no resist is applied, and a step of applying the applied first resist and surge absorbing ink. Applying a second resist so as to cover the entire surface; and a method of manufacturing a surge absorbing structure. 8. A membrane switch or a cable having a surge absorbing structure formed by using the method for manufacturing a surge absorbing structure according to claim 7.