JPH0231493A - Circuit board - Google Patents

Abstract

PURPOSE:To obtain a circuit board where an irregularity in a resistance value is small by a method wherein dummy resistors which do not function as circuit elements are formed simultaneously on both ends of many resistors. CONSTITUTION:A base film 6 where resistors 9a to 9j, conductive parts 11a, 11b and dummy resistors 10 have been printed and formed is laminated on and united to another base film via a spacer; a membrane switch is formed. During this process, the individual conductive parts 11a, 11b are connected to contacts via leading patterns; however, the leading patterns are not connected to dummy resistors 10; these resistors do not function as circuit elements. In this manner, the dummy resistors 10 are formed, on the base film 6, near both ends of the resistors 9a to 9j which are formed at nearly regular intervals in a drive direction of a squeeze member 7. As a result, a resistance value of the resistors 9a to 9j is made uniform; a circuit board with an excellent characteristic can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a circuit board, and particularly to a circuit board in which a large number of resistors are printed and formed in rows at approximately equal intervals on a base film.

[Conventional technology]

A circuit board on which a large number of resistors are printed in rows at approximately equal intervals on a base film is used, for example, as a membrane switch for a keyboard in a word processor input device.

This type of membrane switch usually consists of two base films, each with an upper contact and a lower contact printed thereon.
It is constituted by a laminate including spacers interposed between these base films.

This spacer has openings formed at the upper and lower contact positions of the base film, and when the membrane switch is pushed in, both contacts formed on each base film come into contact with each other at the opening, and the membrane switch The ON operation is performed.

By the way, when using a keyboard equipped with a membrane switch as described above, if a large number of keys are pressed one after another at an extremely fast speed, the next key will turn off before the previously pressed key returns from ON to OFF. The ON operation of the key may be performed. In some cases, during the key operation process, three keys that are operated in sequence are turned on at the same time.
There may even be times when it is in an operational state.

Therefore, in personal computers and word processors, even if such simultaneous ON operations are performed, the input order of switch operations does not change, phantom key operation is not performed, and the keys are not pressed according to the operation order up to the Nth key. There are known devices equipped with a so-called N-key rollover circuit that allows input operations to be performed correctly. This N
As the key rollover circuit, a circuit is used in which a diode, a capacitor, or a resistor is connected in series between one contact point of a membrane switch constituting the keyboard and an input signal output terminal. In this case, if chip components such as diodes and capacitors are used as circuit elements for the N-key rollover circuit, not only will forming and attaching them to the base film become a complicated process, but the thin feature of the membrane switch will not be utilized. Generally, an N-key rollover circuit is used in which a resistive film is printed on a flexible film.

FIG. 4 shows the process of creating resistors 9 in rows at approximately equal intervals on the base film 6 by screen printing for the purpose of configuring the N-key rollover circuit described above. A printing screen 1 as shown in a perspective view in FIG. 5 is used. This printing screen 1 includes a frame 2 having an opening 2a, a mesh 3 made of Teflon fiber or the like stretched over the entire surface of the frame 2, and a mesh 3 of a predetermined shape formed at a predetermined position on the mesh 3. Except for the pattern 4 position, it is composed of a resist film 5 made of a photosensitive resin material etc. which is coated on the mesh 3. These patterns 4 and resist film 5 are created by applying a photosensitive resin to the entire surface of the mesh 3, transferring and baking a mask onto the photosensitive resin, and developing this to make the portion corresponding to pattern 4 photosensitive. Formed by removing resin.

As shown in FIG. 4, the above-mentioned printing screen 1 is positioned on the base film 6 and S! When the squeeze member 7 made of an elastic material such as rubber is driven in the six directions of the arrows, the resistance paste material 8 passes through the mesh 3 facing the pattern 4 and is applied onto the base film 6. After this application, a drying and baking process is performed, and resistors 9 made of resistor paste material 8 are printed and formed at predetermined positions on base film 6, depending on the formation position and shape of pattern 4.

[Problem to be solved by the invention]

FIG. 6 shows how ten resistors of the same shape are formed in a row at approximately equal intervals on the base film 6 using the screen printing method shown in FIG. 4 described above. This is data of measured resistance values. As is clear from this measurement result, the resistance values of the resistors located at both ends along the arrangement direction are significantly lower than those of the other resistors.

This is thought to be because the state of sliding friction between the resistance paste material 8 and the printing screen 1 in FIG. 4 is different in the pattern 4 portions at both ends than in the other portions. Partly, the squeezing member 7 is driven in contact with the resistance paste material 8, which is a pseudoplastic fluid, at a predetermined angle.
When the resistive paste material 8 moves on the printing screen l by this drive, the sliding friction between the resistive paste material 8 and the printing screen 1 suddenly increases at the initial pattern 4 position. For this reason, the movement of the upper layer of the resistive paste material 8 and the lower layer that contacts the pattern 4 becomes uneven, and a relatively large amount of the resistive paste material 8 adheres to the base film 6 . On the other hand, at an intermediate position beyond the first pattern 4, the sliding friction between the resistive paste material 8 and the printing screen 1 stabilizes at a predetermined value, and the resistive paste material 8 moves uniformly as a whole, as described above. Less resistive paste material 8 than in the original pattern 4 positions is deposited on the base film 6 more or less uniformly. Then, when the last pattern 4 position is reached, the sliding friction between the resistance paste material 8 and the printing screen 1 suddenly decreases on the tip side in the moving direction, so that the movement state of the resistance paste material 8 resumes at that position. This results in non-uniformity, and a relatively large amount of the resistive paste material 8 is deposited on the base film 6.

In this way, the resistors 9 that are printed in rows on the base film 6 at approximately equal intervals are arranged so that the resistors 9 located at both ends in the driving direction of the squeezing member 7 during printing are larger than the other resistors 9. There is also a tendency for the resistance value to decrease as the thickness increases.

The present invention has been made in view of the current state of this type of circuit board as described above, and an object thereof is to provide a circuit board with less variation in resistance value.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a circuit board in which resistors are printed on a base film using a printing screen. This feature is characterized in that a dummy resistor is printed and formed at the same time.

[Effect]

A pattern corresponding to a resistor required on the circuit and dummy patterns located at both ends of the pattern arrangement are formed on a printing screen, and the resistor is printed on a base film using this printing screen. Although the resistance values of the resistors at both ends vary, the resistance values of the other resistors are relatively uniform. Therefore, by treating the resistors at both ends with large variations as dummy resistors that do not function as circuit elements, and the other resistors as circuit elements, a circuit board with small variations in resistance value can be realized.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to FIGS. 1 to 3.

Here, FIGS. 1 to 3 are diagrams explaining the present invention in detail, with FIG. 1 being a plan view showing the structure of the circuit board, and FIG. 2 being an explanatory diagram showing the printing process of the circuit board. FIG. 3 is a characteristic diagram showing the measured resistance value of the resistor on the circuit board.

This embodiment is an example of application to a membrane switch equipped with an N-key rollover circuit, and as shown in FIG. Resistor 9a, 9
b...9j are printed in two rows at equal intervals, and conductive parts 11a and 11b made of silver or carbon paste material are printed on both ends of each resistor in the longitudinal direction. There is. In addition, dummy resistors 10 are printed near both ends of each row of resistors 9a to 9j in the arrangement direction (arrow entry direction), and these dummy resistors 10 have conductive parts 11a, 11b. is not printed.

In this way, the conductive parts 11a of the resistors 9a to 9L.

The base film 6 on which the dummy resistor 11b and the dummy resistor 10 are printed is laminated and integrated with the other base film (both not shown) via a spacer to form a membrane switch. In this case, each of the conductive parts 11a, l
lb is connected to the contact via a routing pattern (not shown), but the routing pattern is not connected to each dummy resistor 10. In other words, each dummy resistor 10 is printed on the base film 6. It does not function as a circuit element.

The resistors 93 to 9j and the dummy resistor 10 described above are printed on the base film 6 using the printing screen 1, as shown in FIG. This printing screen 1
is basically the same as that already explained using FIG. 5, except that a dummy pattern 4' corresponding to each dummy resistor 10 is provided. That is, on the printing screen 1, dummy patterns 4' at both ends and a plurality of patterns 4 located between these are formed in a row at approximately equal intervals, and the printing screen 1 is placed on the base film 6. After positioning and placing the squeegee member 7 in the direction of arrow A in FIG. It is applied onto the film 6. In this case, move the squeezing member 7 from the left end of FIG.
When moving in the direction with a predetermined contact pressure, first the dummy resistor 10 is applied corresponding to the dummy pattern 4', then the resistors 9a to 9j are applied corresponding to each pattern 4, and finally the resistor 10 is applied corresponding to the dummy pattern 4'. Then, a dummy resistor 10 is applied again corresponding to the dummy pattern 4'.

At this time, as already explained, the state of sliding friction between the resistance paste material 8 and the printing screen 1 is different from that of the dummy patterns 4 at both ends of the squeezing member 7 in the driving direction.
Since the position ' is different from the other positions of the butter 24, the thickness of the dummy resistor 10 coated on the base film 6 is slightly thicker than that of the other resistors 9a to 9j.

FIG. 3 is a characteristic diagram obtained by measuring the resistance values of the resistors 9a to 9j on the circuit board printed in this way, and shows that the resistance values of all the resistors 9a to 9j are approximately It can be seen that it has uniform and excellent resistance value characteristics. (In Figure 3, the maximum value of the measured values obtained from multiple circuit boards is shown by ``mu'', the minimum value of the measured values is shown by ``, and the average value of the measured values is shown by ``x''.) In this way, , in the above embodiment, the base film 6
Above, these resistors 9a to 9j are formed in rows at approximately equal intervals in the driving direction of the squeeze member
Since the dummy resistors 10 are formed near both ends of the array of resistors a to 9j, the resistance values of the resistors 9a to 9j are made uniform, and a circuit board with excellent characteristics can be obtained.

In addition, although the above-mentioned example explained the case where the resistor for the N-key rollover circuit was printed and formed on the base film, the present invention is not limited to this example.
It is applied when a large number of resistors are printed in rows at approximately equal intervals on a base film on which a general integrated circuit is formed.

[Effects of the Invention] As explained in detail above, according to the present invention, it is possible to set a plurality of resistors used as circuit elements to almost uniform resistance values, so that a circuit board with excellent characteristics can be manufactured. can be provided.

[Brief explanation of the drawing]

FIG. 1 is a plan view schematically showing a circuit board according to an embodiment of the present invention, FIG. 2 is an explanatory diagram showing a printing process of an embodiment of the present invention, and FIG. 3 is a plan view schematically showing a circuit board according to an embodiment of the present invention. A characteristic diagram showing the resistance value characteristics of the circuit board, Figure 4 is an explanatory diagram showing the screen printing process, Figure 5 is a perspective view of the printing screen, and Figure 6 is a diagram showing the resistance value characteristics of the circuit board.
The figure is a resistance value characteristic diagram of a conventional circuit board. 1... Printing screen, 3...
...Mesh, 4... Pattern, 4
′・・・・・・Dummy pattern, 5・・・・・・
...Resist film, 6...Base film, 7...Squeeze member, 8...
...Resistance paste material, 9a to 9j...
...Resistor, 10...Dummy resistor, l
la, llb... Conductive part. -〇Figure 4 Figure 5!

Claims (1)

[Claims] In a circuit board in which a large number of resistors that function as circuit elements are printed and formed in rows at approximately equal intervals on a base film, dummy resistors that do not function as circuit elements are placed at both ends of each of the resistors in the arrangement direction. A circuit board characterized in that it is printed and formed simultaneously with each of the resistors.