JPH0631737Y2 - Printed board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a printed circuit board having an electrically conductive pattern for wiring made of carbon paint and a copper foil circuit on an insulating substrate.

[Prior Art] In the conventional printed circuit board of this type, the fixed contact pattern for the key switch and the conductive pattern and the copper foil circuit are provided on the same surface of the board. Therefore, electronic parts such as capacitors and transistors are mounted on the board. It has been necessary to take measures to prevent the solder from adhering to the fixed contact pattern provided in the exposed state when soldering each electronic component to the copper foil circuit by flow soldering. Therefore, conventionally, the fixed contact pattern is masked with a solder resist film, and after the soldering process of the electronic component is completed, the resist film is removed to expose the fixed contact pattern.
Recently, fixed contact patterns have been formed with carbon paint.Since the conductive pattern for wiring this fixed contact pattern to a predetermined part of the circuit was formed with silver paint, it is necessary to print these patterns. It was necessary to perform each in a separate process.

As described above, the conventional printed circuit board of this type requires an extra step of masking the fixed contact pattern and a step of removing the mask after mounting the electronic component, and the fixed contact pattern and the conductive pattern are removed. Since it needs to be formed in different steps, there is a drawback that the number of steps increases and the cost increases.

Therefore, the inventor of the present application, in order to eliminate this drawback,
The fixed contact pattern for key switches and the conductive pattern for wiring are formed on one surface of the insulating substrate, and the copper foil circuit is formed only on the other surface of the insulating substrate. It was considered to be formed by carbon paint. Further, when the fixed contact pattern for the key switch and the conductive pattern are formed by the carbon paint, if the through hole conductor is formed after the circuit patterns are formed on both surfaces of the substrate, there is a problem that a sufficient through hole conductor cannot be formed. For example, if the circuit pattern is formed so that the end of the pattern extends to the position just before the opening end of the through hole, the carbon paint partially flows into the opening end of the through hole when the circuit pattern is formed. . However, the surface of the inflow portion formed by curing the carbon paint is relatively unsuitable for a conductive material for forming a through-hole conductor such as silver paint. Therefore, when a through-hole conductor is formed later by using a conductive paint such as silver paint, the conductive paint for forming the through-hole conductor flows down from the inflow part formed by the carbon paint formed in the through-hole. There is a high possibility that a defective connection easily occurs between the circuit pattern and the through-hole conductor. It is possible to form a circuit pattern by using carbon paint so that the opening end of the through hole is left, but in this case, the conductive paint for forming the through hole conductor is formed by the corner of the opening end of the through hole. It may break, and in this case as well, poor connection between the circuit pattern and the through-hole conductor is likely to occur. Therefore, the inventor considered forming the fixed contact pattern and the conductor pattern with carbon paint after forming the through-hole conductor first.

[Problems to be Solved by the Invention] However, since sharp edges are formed at the corners of the pattern of the copper foil circuit formed by etching, if a number of printed circuit boards are transported in a stacked state, the copper of the upper printed circuit board is transported. There is a problem that the conductive pattern and the fixed contact pattern formed by the carbon paint of the other printed circuit board arranged on the lower side are cut by the sharp edge of the foil circuit. In particular, since the surface of the end portion of the through-hole conductor has large irregularities, when the conductive pattern is formed by the carbon coating material so as to cover the surface of the end portion, the carbon coating material on the end portion is easily rubbed. If the carbon paint is rubbed and scattered, there is a problem that the insulation between fixed contact patterns is adversely affected.

An object of the present invention is to provide a printed circuit board in which the conductive pattern does not easily break even when stacked and transported.

[Means for Solving the Problem] In the present invention, in order to achieve the above-mentioned object, a conductive pattern is formed so as to cover an end of a through-hole conductor, and the conductive pattern is covered with an insulating protective layer. This forms a conductive pattern and a polymerized layer of an insulating protective layer on the end of the through-hole conductor.

[Advantage of the Invention] If the conductive pattern is formed so as to cover the end portion of the through-hole conductor, the contact area between the through-hole conductor and the conductive pattern increases, and the disconnection is less likely to occur. Further, by forming a polymerized layer in which a conductive pattern and an insulating protective layer are stacked on the protruding end portion of the through-hole conductor, a protruding portion that considerably protrudes from the surface of the substrate can be formed. Since it functions as a spacer between other substrates,
The edge of the copper foil circuit formed on the other side of the other substrate can greatly reduce the likelihood of disconnecting contact patterns not covered by an insulating protective layer.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

1 and 2 show an embodiment of the present invention, in which 1 is an insulating substrate composed of a paper phenol laminate, a paper epoxy laminate, a glass epoxy laminate, etc. A copper foil circuit 2 having a predetermined pattern is formed on one surface of the substrate 1 by etching. On the other surface of the substrate 1, fixed contact patterns 3 for key switches are provided.
3'and wiring conductive patterns 4 and 4'for connecting these patterns to predetermined locations on the substrate are both formed of carbon paint (carbon powder added to resin binder). If both the fixed contact patterns 3 and 3'and the conductive patterns 4 and 4'are made of carbon paint as described above, both patterns can be formed by one printing, and the number of steps can be reduced. The terminal portions 4a and 4'a of the conductive patterns 4 and 4'that can be connected to the copper foil circuit are through-hole conductors 5 provided through holes 1a penetrating the substrate 1.
Is connected to a predetermined portion of the copper foil circuit 2. In the illustrated example, the through-hole conductor 5 is provided before the conductive patterns 4 and 4 ′ are formed, and the conductive patterns 4 and 4 ′ are arranged so that the terminal portions 4 a and 4 a ′ overlap the ends of the through-hole conductor 5. It is printed. A portion of the copper foil circuit 2 that avoids the adhesion of solder is covered with a solder resist 6.

The conductive patterns 4 and 4'are covered with an insulating protection layer 7 formed by printing. Sharp edges are formed at the corners of the pattern of the copper foil circuit 2 formed by etching. However, if the insulating protective layer 7 is formed on the conductive patterns 4 and 4 ', the conductive patterns 4 and 4'formed from a mechanically weak carbon coating can be protected, so that the printed circuit boards are stacked. Even if it is transported in this state, the conductive pattern is not cut by the sharp edge of the copper foil circuit 2 of another printed circuit board. In particular, since the conductive patterns 4 and 4'are formed so as to cover the ends of the through-hole conductors 5, the conductive patterns are less likely to be cut, and in this embodiment, the entire through-hole conductors 5 are insulated and protected. Since it is covered with the layer 7, the cutting of the conductive patterns 4 and 4 ′ hardly occurs. Through-hole conductor 5
Since the conductive pattern 4'is formed so as to cover the end of the through hole conductor 5, it protrudes above the end of the through-hole conductor 5 considerably above the fixed setting patterns 3 and 3 '. It functions as a spacer means when it is polymerized with another printed circuit board. Therefore, cutting of the fixed contact pattern can be reliably prevented. According to the present embodiment, the conductive pattern and the fixed contact pattern for the key switch are formed of carbon paint, but the carbon paint on the through-holes and the carbon paint on the contacts are rubbed and scattered. Can be prevented. Further, even if the carbon paint on the contacts is scattered, it does not adversely affect the insulation between the fixed contact patterns.

Although not shown, the fixed contact pattern 3,
On the surface on which 3'and the conductive patterns 4 and 4'are provided, further fixed contact patterns and conductive patterns are provided by the required number. Further, a hole (not shown) for mounting an electronic component is provided through a predetermined portion of the substrate 1 and the copper foil circuit 2, and the copper foil circuit is provided with the electronic component lead wire inserted in this hole. By applying the flow solder to the surface, the electronic component is soldered to the copper foil circuit. In this case, since the fixed contact patterns 3, 3'and the conductive patterns 4, 4'are on the surface opposite to the copper foil circuit 2,
Solder does not adhere to these patterns. Therefore, it is not necessary to mask the fixed contact pattern and the wiring conductor pattern.

As described above, when both the fixed contact pattern and the conductor pattern are made of carbon paint, the operating resistance of the key switch is unavoidably higher than 500Ω, but in most cases, the key switch is "1" and "0". Since it suffices to be able to selectively obtain the state of "", even if there is an operating resistance of this level, it does not cause any trouble in almost all cases.

In the above embodiment, the fixed contact patterns 3 and 3'are formed in a U shape, but the shape of this fixed contact pattern is arbitrary, and it is easy to contact the movable contact of the key switch such as a comb blade shape and a T shape. Can be formed in the shape of.

In the above embodiment, it is needless to say that the surface of the substrate 1 on which the fixed contact pattern is provided can be further provided with other patterns such as a printing resistor and a resistor for a variable resistor, if necessary.

[Effect of the Invention] As described above, according to the present invention, since the conductive pattern is formed so as to cover the end portion of the through-hole conductor, the contact area between the through-hole conductor and the conductive pattern is increased, resulting in disconnection. It gets harder. Further, by forming a polymerized layer in which a conductive pattern and an insulating protective layer are stacked on the protruding end portion of the through-hole conductor, a protruding portion that considerably protrudes from the surface of the substrate can be formed. It acts as a spacer to the other board, which greatly reduces the possibility that the edge of the copper foil circuit formed on the other side of the other board will break the contact pattern not covered by the insulating protective layer. There is an advantage that can be reduced. In particular, since the surface of the end of the through-hole conductor has large irregularities, if a conductive pattern is formed with carbon paint so as to cover the surface of the end, the carbon paint on the end of the through-hole conductor Although it rubs easily, if a conductive pattern that covers the surface of the end of the through-hole conductor is also covered with an insulating protective layer as in the present invention, even if another substrate is stacked, the end of the through-hole conductor is covered. There is an advantage that the carbon paint of 1 does not rub and scatter.

[Brief description of drawings]

FIG. 1 is a plan view showing an essential part of an embodiment of the present invention, and FIG. 2 is an enlarged sectional view showing a part of the section taken along the line II-II of FIG. 1 ... Insulating substrate, 2 ... Copper foil circuit, 3, 3 '... Fixed contact pattern for key switch, 4 ... Conductive pattern for wiring, 5 ... Through-hole conductor.

Claims (1)

[Scope of utility model registration request] 1. A conductive pattern for power distribution and a fixed contact pattern for a key switch are formed on one surface of an insulating substrate by a carbon paint, and a copper foil circuit is formed on the other surface of the insulating substrate. A printed circuit board formed by connecting a predetermined portion of the conductive pattern and a predetermined portion of the conductive pattern by a through-hole conductor penetrating the insulating substrate, wherein the conductive pattern is formed so as to cover an end portion of the through-hole conductor, A printed circuit board, wherein the conductive pattern is covered with an insulating protective layer, and the conductive pattern and the polymerized layer of the insulating protective layer are formed on the end portions of the through-hole conductor.