JPH0419823Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a printed circuit board equipped with a fixed contact portion for a switch used in a keyboard of an electronic device or the like.

[Prior Art] In an electronic device having a keyboard such as a computer terminal device, a conductive circuit having a pair of fixed contact portions and a wiring portion connected to the fixed contact portion is formed on an insulating substrate using metal such as copper foil. A switch is constructed by using a printed circuit board made of foil and supporting movable contacts made of conductive rubber or the like so that they can be brought into contact with and separated from each pair of fixed contact parts. The reason why the fixed contact part is made of metal foil is that the fixed contact part made of metal foil has superior mechanical strength and durability compared to a thin film fixed contact part made only of carbon paint, etc. This is because conductivity can be ensured. However, if the metal foil is exposed, the surface will oxidize and the surface resistance will increase. Therefore, in some printed circuit boards of this type, a contact conductive layer made of carbon paint or the like is coated on the fixed contact portions of the conductive circuit in order to prevent the fixed contact portions from oxidizing.

[Problem to be solved by the invention] However, since the edge of the fixed contact made of metal foil is edge-shaped, the contact conductive layer made of carbon etc. may be cut during printing in that part, or its thickness may be damaged. The problem arises that the color becomes thinner. In addition, if shocks are repeatedly applied by the movable contact, the contact conductive layer may come off from the part of the contact conductive layer above the edge-like edge of the fixed contact. This resulted in the disadvantage that the metal foil portion of the fixed contact was exposed and oxidized.

An object of the present invention is to provide a printed circuit board that suppresses chipping of the contact conductive layer and prevents oxidation of the fixed contact portion.

[Means for Solving the Problems] The present invention comprises an insulating substrate, and a pair of fixed contact portions each having a contact pattern made of a metal foil layer formed on the insulating substrate and short-circuited by a movable contact. The present invention is directed to a printed circuit board having a conductive circuit having a wiring section connected to the fixed contact section. In the present invention, the printing is printed across the opposing portions of the pair of fixed contact portions, and a portion is overlapped with at least the portion facing the movable contact among the edge portions of the opposing portions to form an overlapping portion. Provide an undercoat insulating layer.
Then, a pair of contact conductive layers each having a conductive paste printed thereon is provided so as to cover the overlapping portion of the undercoat insulating layer and the pair of fixed contact portions, respectively.

[Function] In the present invention, by providing an undercoat insulating layer that spans the opposing portions of a pair of fixed contact portions made of metal foil so that a portion (the overlapping portion) overlaps, the edges of the opposing portions of the fixed contact portions are reduce the sharpness of As a result, when the contact conductive layer is printed by the edges of the opposing portions of the fixed contact portion, it is possible to prevent the contact conductive layer from becoming thin or torn. In addition, since the part of the contact conductive layer that the movable contact comes into contact with can be provided so as not to be directly on the edge of the fixed contact part made of metal foil, the adhesive strength of the contact conductive layer can be increased, and the repeatability of the switch can be increased. Not only does it have the advantage of preventing the contact conductive layer from being missing due to use, but it also prevents the fixed contact part from being exposed due to the contact conductive layer being missing, and prevents the fixed contact part made of metal foil from oxidizing. It can be prevented.

[Embodiments] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

In FIGS. 1 to 6, reference numeral 1 denotes an insulating substrate made of, for example, a phenolic resin laminate. Reference numeral 2 denotes a metal foil layer made of copper or the like formed on the insulating substrate 1.
b, constitutes a conductive circuit having a terminal portion 2c. As shown in FIG. 2, each fixed contact portion 2a is formed with a C-shaped contact pattern short-circuited by a movable contact at the end of the wiring portion 2b, and the fixed contact portions 2a, 2a forming a pair are connected to each other. The recesses 2d are arranged to face each other. Reference numeral 3 denotes a top insulating layer formed on the insulating substrate 1 so as to cover the fixed contact part 2a of the conductive circuit and the wiring part 2b other than the terminal part 2c, and this top insulating layer 3 is made of phenolic resin, epoxy resin, etc. ing. 4 denotes opposing portions (recessed portions 2d,
This is an undercoat insulating layer printed across the edge portion (where 2d is formed). When viewed in relation to the movable contact A shown in FIG.
is provided in a region facing the contact surface A1 of the movable contact A. The end portions of the undercoat insulating layer 4 are overlapped with the end edges of the opposing portions of the fixed contact portions 2a, 2a to form an overlapping portion. This undercoat insulating layer 4 is
Like the top insulating layer 3, it is made of phenol resin, epoxy resin, or the like.

Further, a contact conductive layer 5 made of a conductive paste such as carbon is printed so as to cover each fixed contact portion 2a. Each contact conductive layer 5 as shown in FIG.
are provided so that a part thereof overlaps a part of the top insulating layer 3 and the edge part (overlapping part) of the undercoat insulating layer 4, and each contact conductive layer 5 is provided so that it overlaps with a part of the top insulating layer 3 and the edge part (overlapping part) of the undercoat insulating layer 4. The portion covering the contact portion 2a is provided so as to cover the surface of the substrate 1 beyond the edge portion of the fixed contact portion 2a. That is, each contact conductive layer 5
is provided so as to cover the entire area of the metal foil exposed from the top insulating layer 3 and the undercoat layer 4. Since the adhesive strength between the contact conductive layer 5 and each of the insulating layers 3 and 4 and the substrate 1 is high, if the end of the contact conductive layer 5 is not located on the metal foil layer 2, the contact conductive layer 5 may peel off. The strength can be increased, and the contact conductive layer 5 can be prevented from being chipped due to repeated use of the switch.

Further, as described above, the fixed contact portions 2a, 2 forming a pair
When an undercoat insulating layer 4 is provided spanning between the opposing portions of a, and a contact conductive layer 5 is overlaid on the overlapping portion of the undercoat insulating layer 4, the undercoat insulating layer 4 makes the edges of the fixed contact portions 2a, 2a sharp. Since the degree of damage can be reduced, it is possible to prevent the contact conductive layer 5 from being cut at the edge portion of the fixed contact portion 2a. In order to enhance the effect of this undercoat insulating layer 4,
When constructing the switch, it is preferable that the contact surface A1 of the movable contact A, which is provided so as to come into contact with and separate from the fixed contact portion 2a, is formed in a size that does not protrude from the area where the undercoat insulating layer 4 is provided.

FIG. 7 shows another embodiment of the present invention.
In this embodiment, an undercoat insulating layer 4' is formed over the entire opposing portions of fixed contact portions 2a, 2a forming a pair similar to the above embodiment, and contact conductive layers 5', 5' are overcoated insulating layers. Fixed contact part 2a of layer 3,
Approximately the entire area of the edge portion 3a facing the end portion 2a is coated. With this configuration, when the movable contact is pressed against the edge portion of the opposing portion of the pair of fixed contact portions 2a, 2a, the contact conductive layers 5', 5' at that portion are prevented from being cut. be able to. In this embodiment, the undercoat insulating layer 4' and the top insulating layer 3 are connected to each other.

In the embodiment shown in FIG. 7, the opposing contact conductive layers 5', 5' are formed on a moisture-proof undercoat insulating layer 4', and the paired contact conductive layers are formed of a silver-containing conductive paste. Migration can be effectively prevented from occurring between 5' and 5'.

[Effects of the invention] As described above, according to the invention, by providing an undercoat insulating layer that partially overlaps the opposing portions of a pair of fixed contact portions made of metal foil, the fixed contact portions can be improved. In order to reduce the sharpness of the edges of the opposing portions, there is an advantage that when printing the contact conductive layer using the edges of the opposing portion of the fixed contact portion, it is possible to prevent the contact conductive layer from becoming thin or being cut. . In addition, since the part of the contact conductive layer that the movable contact comes into contact with can be provided so as not to be directly on the edge of the fixed contact part made of metal foil, the adhesive strength of the contact conductive layer can be increased, and the repeatability of the switch can be increased. Not only does it have the advantage of preventing the contact conductive layer from being missing due to use, but it also prevents the fixed contact part from being exposed due to the contact conductive layer being missing, and prevents the fixed contact part made of metal foil from oxidizing. It can be prevented.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of a printed circuit board to which the present invention is applied, Fig. 2 is a plan view showing the fixed contact portion of the metal foil layer, and Fig. 3 is a top insulating layer and an insulating undercoat coated on the board. FIG. 4 is a perspective view showing the state in which the contact conductive layer is coated on the substrate, and FIG.
The figure is an explanatory diagram showing the facing position of a movable contact facing a pair of contact conductive layers and the contact conductive layer, FIG. 6 is a sectional view taken along the line - - of FIG. 1, and FIG. 7 is another embodiment of the present invention. FIG. 3 is a plan view of main parts showing an example. DESCRIPTION OF SYMBOLS 1... Insulating substrate, 2... Metallic foil, 2a... Fixed contact portion, 2b... Wiring portion, 4, 4'... Undercoat insulating portion, 5, 5'... Contact conductive layer.

Claims (1)

[Scope of utility model registration request] A conductive device comprising an insulating substrate, a pair of fixed contact portions each having a contact pattern formed of a metal foil layer formed on the insulating substrate and short-circuited by a movable contact, and a wiring portion connected to the fixed contact portion. In a printed circuit board equipped with a circuit, the printed circuit board is printed across opposing portions of the pair of fixed contact portions, and a portion thereof overlaps with at least a portion of the edge portion of the opposing portion facing the movable contact portion. an undercoat insulating layer forming an overlapping part, and a pair of contact conductive layers each having a conductive paste printed so as to respectively cover the overlapping part of the undercoat insulating layer and the pair of fixed contact parts. A printed circuit board characterized by: