JPH08150U - Printed board - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To prevent the carbon paint from rubbing and scattering on the end portions of through-hole conductors even when they are transported in piles. The conductive pattern does not easily break and migration occurs. PROBLEM TO BE SOLVED: To provide a difficult printed circuit board. Conductive patterns 4, 4 made of carbon paint.
′ To cover the ends of the through-hole conductors and to provide terminal portions 4a, 4a
To form ´. The conductive pattern is covered with the insulating protection layer 7. In addition, a pair of through-hole conductors connected to a pair of conductive patterns 4 and 4'connected to a pair of fixed contact switches for key switches 3 and 3'constituting one fixed contact are connected to a pair of fixed contacts for key switch. It is arranged outside the region where the patterns 3 and 3'are formed. Then, one of the pair of conductive patterns 4'is formed so as to cross between the pair of terminal portions 4a, 4a '.

Description

[Detailed description of the device]

[0001]

[Technical field to which the device belongs]

 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.

[0002]

[Prior art]

 In this type of conventional printed circuit board, the fixed contact pattern and conductive pattern for the key switch and the copper foil circuit are provided on the same surface of the board.Therefore, electronic components such as capacitors and transistors are mounted on the board and flow soldering is used. When soldering each electronic component to the copper foil circuit, it was necessary to take measures to prevent the solder from adhering to the fixed contact pattern provided in the exposed state. Therefore, conventionally, the fixed contact pattern is masked with a semiconductor 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, these patterns are printed. 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 also needs a step of removing the masking after mounting the electronic parts. Also, since the conductive pattern needs to be formed in different steps, there is a drawback that the number of steps is increased and the cost is increased.

In order to solve this drawback, the inventor of the present application forms a pattern of fixed contact points for key switches and a conductive pattern for wiring on one surface of the insulating substrate to insulate the copper foil circuit. It was considered to form it only on the other surface of the substrate, and to form the fixed contact pattern for the key switch and the conductive pattern with carbon paint. Further, in the case of forming the fixed contact pattern for the key switch and the conductive pattern by carbon paint, if the through-hole conductor is formed after the circuit patterns are formed on both surfaces of the substrate, there arises 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, carbon paint may partially flow into the opening end of the through hole when the circuit pattern is formed. become. However, the surface of the inflow part formed by curing the carbon paint is relatively incompatible with the conductive paint for forming the through-hole conductor such as silver paint. Therefore, when forming a through-hole conductor using a conductive paint such as silver paint later, the conductive paint for forming the through-hole conductor is removed from the inflow part formed by the carbon paint formed in the through-hole. There is a high possibility that it will run down, and a poor connection will easily occur between the circuit pattern and the through-hole conductor. It is possible to form a circuit pattern by using carbon paint so that the open 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 open end of the through hole. It may be broken, and in this case also, 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 conductive pattern with carbon paint after forming the through-hole conductor first.

[0005]

[Problems to be solved by the device]

 However, since sharp edges are formed at the corners of the copper foil circuit pattern formed by etching, if a number of printed circuit boards are transported in a stacked state, they will be damaged by the sharp edges of the copper circuit on the upper printed circuit board. There was a problem that the conductive pattern and the fixed contact pattern formed by the carbon paint on the other printed substrate arranged on the side were cut off.

In particular, since the surface of the end of the through-hole conductor has large irregularities, when a conductive pattern is formed with carbon paint so as to cover the surface of the end, the carbon paint on the end will not It becomes easy to rub. If the carbon paint is rubbed and scattered, there is a problem that the insulation between fixed contact patterns is adversely affected.

In addition, even if the ends of the pair of through-hole conductors connected to the pair of conductive patterns connected to the pair of fixed contact patterns for key switches that form one fixed contact are covered with carbon paint, There was a migration that occurred between the ends of the through-hole conductors.

An object of the present invention is to prevent the carbon paint on the end portions of the through-hole conductors from rubbing and scattering even when they are stacked and transported, and the conductive pattern does not easily break, and migration does not occur. It is to provide a printed circuit board that is hard to generate.

[0009]

[Means for Solving the Problems]

 In order to achieve the above object, the present invention has a conductive pattern for power distribution and a fixed contact pattern for a key switch formed on one surface of an insulating substrate by a carbon paint, and a copper foil circuit on the other surface of the insulating substrate. The object of the improvement is a printed circuit board which is formed and in which a predetermined portion of the copper foil circuit and a predetermined portion of the conductive pattern are connected by a through-hole conductor penetrating the insulating substrate.

In the present invention, the conductive pattern covers the ends of the through-hole conductors to form the terminal portions (4a, 4a ′). Then, the conductive pattern is covered with an insulating protective layer. As a result, a polymerized layer is formed on the end of the through-hole conductor. In addition, a pair of through-hole conductors connected to a pair of conductive patterns connected to a pair of fixed contact patterns for key switches forming one fixed contact are formed in a region where a pair of fixed contact patterns for key switches are formed. Place it outside. Then, one of the pair of conductive patterns is formed so as to cross between the pair of terminal portions (4a, 4a ') formed on the pair of through-hole conductors.

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 is increased, and the disconnection is less likely to occur. Also, if a conductive layer and an insulating protective layer are overlaid on the protruding end of the through-hole conductor to form a polymer layer, it is possible to form a protruding portion that is significantly protruding from the surface of the substrate. Acts as a spacer to the other substrate overlaid, so that the edges of the copper foil circuit formed on the other side of the other substrate can break contact patterns that are not covered by an insulating protective layer. Can be significantly reduced.

Further, when one of the pair of conductive patterns (4 ′) is formed so as to cross between the pair of terminal portions (4a, 4a ′) formed on the pair of through-hole conductors, a pair of different potentials is formed. A part of the conductive pattern (4 ') made of carbon paint having a potential substantially equal to the potential of one through-hole conductor exists between the ends of the through-hole conductor. If a part of such a conductive pattern is located between the pair of terminal portions (4a, 4a '), the potential gradient between the ends of the pair of through-hole conductors becomes small, so that the gap between the ends of the pair of through-hole conductors becomes small. It is possible to suppress the occurrence of migration that occurs in

[0013]

[Embodiment of device]

 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 laminated plate, a paper epoxy laminated plate, a glass epoxy laminated plate, etc. A copper foil circuit 2 having a predetermined pattern is formed on one surface of the insulating substrate 1 by etching. On the other surface of the substrate 1, fixed contact patterns 3 and 3 ′ for key switches and conductive patterns 4 and 4 ′ for wiring for connecting these patterns to predetermined locations on the substrate are both carbon paint ( It is formed by adding carbon powder to a resin binder. If both the fixed contact patterns 3 and 3'and the conductive patterns 4 and 4'are made of carbon paint in this way, 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 connected to predetermined portions of the copper foil circuit 2 by the through-hole conductors 5 provided through the holes 1a penetrating the substrate 1. Has been done. 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.

As shown in FIG. 1, a pair of through patterns connected to a pair of conductive patterns 4 and 4 ′ connected to a pair of fixed contact point patterns 3 and 3 ′ for a key switch forming one fixed contact. The hole conductors (through-hole conductors formed below the terminal portions 4a and 4a ') are arranged outside the region where the pair of fixed contact patterns 3 and 3'for key switches are formed. The one conductive pattern 4'of the pair of conductive patterns 4 and 4'is curved and formed so as to cross between the pair of terminal portions 4a and 4a '.

The conductive patterns 4 and 4 ′ are covered with an insulating protective 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 the state, the conductive pattern is not cut by the sharp edge of the copper foil circuit 2 on another printed 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 the present embodiment, all of the through-hole conductors 5 are insulated. Since it is covered with the protective layer 7, the conductive patterns 4, 4 ′ are hardly cut. Further, since the conductive pattern 4'is formed so as to cover the end portion of the through-hole conductor 5, it projects considerably above the fixed setting pattern 3, 3'on the end portion of the through-hole conductor 5. Therefore, when this protrusion is overlapped with another printed substrate, it functions as a spacer means. Therefore, disconnection 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 by the carbon coating, but the carbon paint on the through-holes or the carbon paint on the contacts is rubbed and scattered. Can be prevented. 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, on the surface of the substrate 1 on which the fixed contact patterns 3 and 3 ′ and the conductive patterns 4 and 4 ′ are provided, other fixed contact patterns and conductive patterns are required. It is provided. 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 flow soldering to the exposed surface, electronic components are 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 conductive pattern for wiring.

As described above, when both the fixed contact pattern and the conductive pattern are formed of carbon paint, it is inevitable that the operating resistance of the key switch becomes 500Ω or more, but in most cases, the key switch is “1”. Since it suffices to be able to selectively obtain the state of “0” and “0”, even if there is an operating resistance of this level, no problem occurs in almost all cases.

In the above-mentioned 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 the movable contact of the key switch such as the comb blade shape and the T shape is formed. It can be formed into an appropriate shape that is easy to contact with.

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

[0021]

[Effect of device]

 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, and the disconnection is less likely to occur. In addition, by forming a polymer layer with a conductive pattern and an insulating protective layer overlaid on the protruding end of the through-hole conductor, it is possible to form a protruding portion that is significantly protruding from the surface of the substrate. Acts as a spacer between other stacked boards, so that the edge of the copper foil circuit formed on the other side of the other board can cut the contact pattern that is not covered by the insulating protective layer. The advantage is that the sex can be significantly reduced. In particular, since the surface of the end of the through-hole conductor has large irregularities, when a conductive pattern is formed with carbon paint so as to cover the surface of the end, the surface of the end of the through-hole conductor is not covered. Although the carbon paint is easy to rub, if the conductive pattern covering the surface of the end of the through-hole conductor is covered with an insulating protective layer as in the present invention, the end of the through-hole conductor will be covered even when another substrate is stacked. There is an advantage that the carbon paint on the part does not rub and scatter.

Further, according to the present invention, when one of the pair of conductive patterns is formed so as to cross the pair of terminal portions formed on the pair of through-hole conductors, a pair of through-hole conductors having different potentials are formed. Since there is a part of the conductive pattern made of carbon paint whose potential is substantially equal to the potential of one through-hole conductor, the potential gradient between the ends of a pair of through-hole conductors is It is possible to suppress the occurrence of migration that occurs between the ends of the pair of through-hole conductors.

[Brief description of drawings]

FIG. 1 is a plan view showing a main part of an embodiment of the present invention.

FIG. 2 is an enlarged sectional view showing a section along a line II-II of FIG. 1 with a part thereof omitted.

[Explanation of symbols]

 1 Insulating board 2 Copper foil circuit 3, 3'Fixed contact pattern for key switch 4 Conductive pattern for wiring 5 Through hole conductor

Claims (2)

[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 predetermined part of the conductive pattern and a predetermined part of the conductive pattern are connected by a through-hole conductor penetrating the insulating substrate, the conductive pattern (4, 4 ') is connected to the through-hole conductor (5). A printed circuit board, characterized in that terminal portions (4a, 4a ') are formed so as to cover the end portions, and the conductive pattern is covered with an insulating protective layer. 2. A pair of said throughs connected to a pair of said conductive patterns (4, 4 ') connected to a pair of said fixed contact patterns for key switches (3, 3') constituting one fixed contact. The hole conductor (5) is arranged outside an area where the pair of fixed contact patterns (3, 3 ') for key switches are formed, and one (4') of the pair of conductive patterns (4, 4 ') is The printed circuit board according to claim 1, wherein the printed circuit board is formed so as to traverse between a pair of terminal portions (4a, 4a ') formed on the pair of through-hole conductors (5).