JPH04493Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a key switch device provided on a circuit board, and particularly to the structure of a pattern for electrically connecting key switch contacts.

[Conventional technology]

As a conventional key switch device of this type, there is one shown in FIG. 2, which is used, for example, in a dial switch section of a telephone.

This figure is a pattern diagram of a circuit board on which a circuit pattern is formed only on one side, and 1 is a key switch contact consisting of a row contact 1a and a column contact 1b, and 2 is a key switch contact that electrically connects the row contacts 1a of each row for each row. Row pattern made of thin copper foil, 3 is column contact 1 of each column
This is a column pattern made of thin copper foil that electrically connects each column. Row pattern 2 is dial
Row pattern 3 is dial for IC row address
Connected to the IC column address. Furthermore, at the pattern locations where the row patterns 3 intersect, one of the row patterns 3 is separated, and thin patterns 3a and 3b made of carbon are formed as jumpers on the other row pattern 3 covered with an insulating film, The divided patterns are electrically connected.

[Problem that the invention attempts to solve]

However, the key switch device having the above configuration has the following problems.

First, the layout of the pattern that electrically connects the row contacts for each row and the column contacts for each column becomes complicated, and it takes time to design the pattern. The problem was that it was easily affected by noise.

Second, the narrow patterns 3a and 3b provided at the intersections of the patterns have a high resistance, and when the key switch is pressed, the voltage level input to the detection circuit becomes high, causing false detection of the key switch. It was hot too. This will be explained in detail below with reference to the equivalent circuit diagram of FIG.

In the figure, 5 is a dial IC, and an output port 5a and an input port 5b of the dial IC 5 are connected via a key switch 7 by a wiring 6 corresponding to a copper foil pattern on the circuit board, and this wiring 6 An equivalent resistance R ₀ corresponding to the thin carbon pattern as the jumper described above is inserted in . In addition, the output port 5a is the dial IC 5
The input port 5b is connected to the gate 8 within the gate 9, the gate 8 is connected to the power supply _VSS , and the input port 5b is lifted to the power supply _VDD via a resistor _R1 .

The voltage V input to the gate 9 when the key switch 7 is closed is expressed by the following equation.

V=R ₀ ×V _DD −V _SS /R ₀ +R _1For simplification, let R ₀ =R ₁ and V _SS =0, and the above equation becomes as follows.

V=R ₀ ×V _DD /2R ₀ =V _DD /2 In other words, when key switch 7 is pressed, the dial
The voltage level detected by IC5 is V _DD /2,
Temporarily set the threshold level of gate 9 to V _DD /3.
If it is less than this, the voltage level of the input port 5b will not fall below this level, and the depression of the key switch 7 will not be detected.

[Means for solving problems]

The present invention was developed to solve the above problems. Either the row contacts or the column contacts are connected by a thin pattern made of copper foil, and the other is connected by a thick pattern made of carbon through an insulating film. This is what I did.

[Effect]

The configuration of the pattern that connects each contact is simplified, and jumper portions of the pattern are eliminated.

〔Example〕

Next, the present invention will be explained with reference to the drawings.
FIG. 1 is a pattern diagram showing an embodiment in which the present invention is applied to a dial switch section of a telephone set.

Figure a is a pattern diagram of a pattern made of copper foil that is first formed on a circuit board, 11, 12
are row contacts and column contacts arranged in a matrix on the circuit board, these constitute key switch contacts, and the row contacts 11 are electrically connected by one thin row pattern 13 for each row. One end of the pattern 13 is connected to each row address of the dial IC. Further, among the column contacts 12, the one located at the bottom of each column in the figure is connected to the column address of the dial IC by a pattern 14. In addition,
15 is a ground pattern connected to ground potential, and a resist treatment is applied to the copper foil pattern except for the row contacts 11 and column contacts 12;
An insulating film is formed.

FIG. 2b is a pattern diagram of a pattern formed on the pattern shown in a after it is formed on the circuit board, and 16 is a pattern diagram of a pattern formed on each row of contacts 11.
A row contact carbon layer 17 made of carbon is formed on top of and electrically connected to each column contact 12.
This is a column pattern consisting of a single thick piece of carbon that electrically connects each column. Each column pattern 17 is electrically connected to each column address of the dial IC by the pattern 14.

In such a configuration, a key switch (not shown) is disposed on each key switch contact, and the row contact carbon layer 16 and the column pattern 17 at the location where the key switch is pressed are electrically connected by the key switch. , the row contact 11 and the column contact 12 located below this point are electrically connected, and the row pattern 1
3 and pattern 14, this conductive point is transmitted to the dial IC, and the dial IC detects the pressed point of the key switch.

As described above, according to this embodiment, row pattern 1
3 and the column pattern 17 in a straight line, the pattern configuration is simplified and the noise resistance of the circuit is improved.Furthermore, it is possible to arrange the ground pattern with a large area as shown in Figure 1a. 15, the noise resistance of the circuit is further improved. Furthermore, since the patterns do not intersect with each other as in the past, there are no jumper points, and therefore, there is no longer any erroneous detection of the key switch of the dial IC due to the resistance of the jumper part as in the past. Furthermore, since the row pattern 17 uses inexpensive carbon, the manufacturing cost of the pattern is reduced.

Although the above embodiment shows a case where the key switch contacts are arranged in 4 rows and 3 columns, the present invention is not limited to this. Also, although the above embodiment shows a case where the key switch contacts are applied to a telephone, other general switch devices may be used. In addition, although in the above embodiment the column contacts are connected by thick carbon patterns and the row contacts are connected by thin copper foil patterns, the reverse may be used, and the same effect as in the above embodiment can be obtained.

[Effect of idea]

As explained above, the present invention connects either the row contact or the column contact with a thin pattern made of copper foil, and connects the other with a thick pattern made of carbon through an insulating film.
The configuration of the pattern connecting each contact is simplified,
The design of the pattern can be done in a short time, and the effect of noise on the circuit is reduced.Also, since there are no jumper parts in the pattern, the resistance of the pattern does not increase, which reduces the possibility of false key switch detection. It also has the effect that it no longer occurs.
In addition, since cheap carbon is used for the pattern,
This also has the effect of reducing pattern manufacturing costs.

[Brief explanation of the drawing]

FIG. 1 is a pattern diagram showing an embodiment of the present invention, FIG. 2 is a conventional pattern diagram, and FIG. 3 is an equivalent circuit diagram for explaining the problems of the conventional technology. 11... Row contact, 12... Column contact, 13... Row pattern, 14... Column pattern, 15... Earth pattern, 16... Row contact carbon layer, 17...
column pattern.

Claims (1)

[Scope of utility model registration request] In a key switch device consisting of row contacts and column contacts arranged in a matrix on a circuit board, the row contacts and column contacts are electrically connected to either the row contact or the column contact for each row or each column. forming a thin pattern of copper foil, forming an insulating film on the copper foil except for the row contacts and column contacts, and connecting the row contacts or column contacts not connected to the pattern to each row or each column; A key switch device characterized by electrical connection using a thick pattern made of carbon.