JPH11177197A - Flexible wiring board and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase flexibility in a circuit design, by electrically connecting a jumper portion to a conductive circuit pattern without increasing resistance of a conductor. SOLUTION: In a flexible wiring board 20 including a plurality of conductive circuit patterns 12, 13, 14 formed on a flexible insulating board 11 and having a metallic film 15 on the surface, wherein two freely selected conductive patterns 12, 14 of the plurality of conductive circuit patterns 12, 13, 14 are electrically connected to each other, and a jumper portion 17 formed between the two conductive patterns 12, 14 such that it is not put into contact with the other conductive pattern 13, a resist layer 16 is formed on the top surface of the jumper portion 17, and the conductive circuit pattern 13 between the two conductive circuit patterns 12, 14 is formed on the top surface of the resist layer 16 so that it is electrically insulated from the jumper portion 17.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexible wiring for forming a plurality of conductive circuit patterns on a flexible insulating substrate and forming a jumper for connecting an arbitrary pattern among the plurality of conductive circuit patterns. Regarding the substrate.

[0002]

2. Description of the Related Art An example of this type of flexible wiring board will be described with reference to FIGS. FIG. 3 is a sectional view showing the structure of a conventional flexible wiring board.
Is PET (polyethylene terephthalate), PEI
A conductive circuit pattern 2 made of a conductive paste (for example, Ag paste) formed in an arbitrary shape on an insulating substrate 1 made of (polyetherimide), PI (polyimide), or the like.
3, 4 and a metal film 5 made of a metal or an alloy having a low conductor resistance such as Cu, Au, SnPb, or Ni formed on the surfaces of the conductive circuit patterns 2, 3, and 4; An organic or inorganic resist layer 6 formed so as to cover the conductive circuit pattern located between 2 and 4, and the conductive circuit pattern 2 on the resist layer 6;
And 4 (for example, Ag)
And a resist layer 8 formed to cover the entire conductive circuit patterns 2, 3, 4, the metal film 5, the resist layer 6, and the jumper portion 7 formed on the insulating substrate 1. Is a flexible wiring board including:

The jumper 7 is wired by the resist layer 6 so as to electrically connect the conductive circuit patterns 2 and 4 so as not to contact the conductive circuit pattern 3.

An example of such a conventional method for manufacturing a flexible wiring board will be described with reference to FIG. The same parts as those in FIG. 3 are denoted by the same reference numerals, and detailed description thereof will be omitted.

As shown in FIG. 4A, the conductive circuit patterns 2, 3, and 4 are arranged on the insulating substrate 1 by using a screen printing technique so as to form an arbitrary circuit, and are cured. In this curing step, when the conductive paste (for example, Ag paste) used for the conductive circuit patterns 2, 3, and 4 is thermosetting, a hot blast furnace is used. , IR (infrared) curing, an IR furnace, and electron beam curing, an electron beam curing furnace.

In order to improve the electrical efficiency by lowering the conductor resistance of the conductive circuit patterns 2, 3, and 4, metals such as Cu, Au, and SnPb shown in FIG. 4B are plated.
As a processing method, for example, conductive circuit patterns 2, 3, 4
Immersed in the plating solution of the above metal while energizing
A metal film 5 is formed on the surface of the conductive circuit pattern.

Next, as shown in FIG. 4C, a resist is placed on the insulating substrate 1 by screen printing so as to cover the conductive circuit pattern 3 on which the metal film 5 is formed, and a hot air furnace, a UV furnace , An IR furnace or an electron beam curing furnace to form a resist layer 6.

FIG. 4D shows a step of forming the jumper portion 7. The conductive paste (for example, Ag paste) used for the jumper part 7 is also the conductive circuit patterns 2, 3,
Various materials such as thermosetting, UV-curing, and IR-curing are selected in the same manner as in 4, and are printed so as to cover the conductive circuit pattern 3 and cured by an appropriate means.

Finally, as shown in FIG. 4 (e), the conductive circuit patterns 2, 3, 4 and the metal film 5, the resist layer 6, and the jumper portion 7 formed on the insulating substrate 1 are covered to form a protective film. Is formed through the steps of printing and curing.

[0010]

However, the conventional flexible wiring board 10 described above has the following disadvantages. That is, in the step of forming the resist layer 6 shown in FIG. 4C, when the resist disposed by printing is cured, the resist is heated in the air by any method, so that the metal film that is exposed to the outside air is used. 5 is oxidized.

As a result, the conductor resistance at the interface between the jumper portion 7 formed in the step of FIG. 4D and the metal film 5 on the conductive circuit patterns 2 and 4 increases, or the resistance at the interface varies. Therefore, there is a problem that the performance as an electric circuit is reduced or there is a problem in reliability.

For this reason, as shown in FIG. 5, the present inventor has taken measures to prevent oxidation of the metal film 5. 3 and 4
The same parts as those described above are denoted by the same reference numerals, and detailed description thereof will be omitted. That is, the insulating substrate 1 after the formation of the metal film 5 shown in FIG. 4B is immersed in, for example, a methanol-based antioxidant to coat the metal film 5 with the antioxidant film 9. In this case, since the metal film 5 does not oxidize, it was predicted that the above-mentioned inconvenience would not occur.

However, the antioxidant film 9 and the jumper 7
However, there is a problem that the compatibility such as adhesion is poor and the conductor resistance at the interface is still high.

[0014]

According to the present invention, a plurality of conductive circuit patterns each having a metal film on the surface are formed on a flexible insulating substrate according to the present invention. Of the plurality of conductive circuit patterns, two or more arbitrarily selected conductive circuit patterns are electrically connected, and the other conductive circuit patterns located between the two or more conductive circuit patterns include: In a flexible wiring board having a jumper portion formed so as not to contact, a resist layer is formed on an upper surface of the jumper portion, and the two or more conductive circuits described above are electrically insulated from the jumper portion. The problem is solved by a flexible wiring board characterized in that another conductive circuit pattern located between the patterns is formed on the upper surface of the resist layer.

[0015] The above object is also achieved by a first step of forming a conductive jumper on a flexible insulating substrate according to claim 3 of the present invention, and an end of the jumper. A second step of forming a first resist layer on the upper surface of the jumper portion except for this end portion, so that the first and second portions are in contact with the connection portion of the jumper portion and become electrically conductive. Forming a third conductive circuit pattern on an insulating substrate and forming a third conductive circuit pattern on an upper surface of the first resist layer; and upper surfaces of the first, second, and third conductive circuit patterns. Forming a metal film on the insulating substrate, and forming a second resist layer so as to cover the jumper portion, the first resist layer, the first, second, and third conductive circuit patterns formed on the insulating substrate. And a fifth step of forming. It is solved by the method for manufacturing a flexible wiring board, wherein the door.

According to another aspect of the present invention, there is provided a first step in which a conductive paste is printed on a flexible insulating substrate and cured to form a jumper portion. A second step of printing a resist on the upper surface of the jumper portion so that both ends of the jumper portion are exposed and hardening to form a first resist layer, and contacting the exposed both ends of the jumper portion with each other. A conductive paste is printed on the insulating substrate, and at the same time, a conductive paste is printed on the upper surface of the first resist layer so as to form a circuit, and cured to form the first, second, and third pastes. A third step of forming a conductive circuit pattern, and first, second, and third steps;
Forming a metal film by plating on the conductive circuit pattern, and forming a jumper portion formed on the insulating substrate, first, second, and third conductive circuit patterns, a metal film, and a first resist. And a fifth step of printing and curing a resist so as to cover the layer to form a second resist layer.

According to the first aspect of the present invention, since the metal film and the jumper do not contact each other, the jumper and the two or more conductive circuit patterns are electrically connected without increasing the conductor resistance. be able to.

According to the flexible wiring board of the second aspect, insulation between the other conductive circuit patterns located between the two or more conductive circuit patterns electrically isolated by the resist layer and the jumper portion is ensured. Can be

Further, according to the method for manufacturing a flexible wiring board according to the second and third aspects, the metal film and the jumper do not come into contact with each other. Can be electrically connected to the conductive circuit pattern.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing an embodiment of a flexible wiring board according to the present invention. In the drawing, reference numeral 20 denotes an arbitrary pattern on an insulating substrate 11 made of PET, PEI, PI, or a composite thereof. A jumper portion 17 made of a conductive paste (a paste containing a conductive metal such as an Ag paste or a copper paste) formed on
Conductive circuit patterns 12 and 14 made of conductive paste and conductively connected to each other via jumper portion 17 therebetween.
And an organic or inorganic resist layer 16 formed on the upper surface of the jumper portion 17, a conductive circuit pattern 13 formed on the upper surface of the resist layer 16, and a surface formed on the conductive circuit patterns 12, 13, and 14. Cu, Au, S
A metal film 15 made of a metal or an alloy having a low conductor resistance such as nPb, and the whole of the conductive circuit patterns 12, 13, 14, the metal film 15, the resist layer 16 and the jumper portion 17 formed on the insulating substrate 11 are covered. And a resist layer 18 formed on the flexible wiring board.

The jumper portion 17 is arranged so as to be in direct contact with the conductive circuit patterns 12 and 14 and not to be in contact with the metal film 15, but this arrangement can be achieved by the following manufacturing process.

FIG. 2 is a process chart showing one embodiment of a method for manufacturing a flexible wiring board according to the present invention. In FIG. 2A, a conductive paste is arranged on the insulating substrate 11 by screen printing in an arbitrary pattern, and is cured to form a jumper portion 17.

In this curing step, as in the conventional case, the Ag paste used for the jumper 17 is a hot-air oven if it is thermosetting, a UV oven if it is UV-curing,
In the case of R curability, an IR furnace is used, and in the case of electron beam curability, an electron beam curing furnace is used.

Next, referring to FIG.
An organic or inorganic resist is printed on the upper surface of 7, and cured by any method in the same manner as the jumper 17, thereby forming a resist layer 16.

At this time, the resist layer 16 is formed except for both ends so that both ends of the jumper portion 17 become connection portions.

The conductive circuit patterns 12, 13, and 14 formed in FIG. 2C are formed by curing a printed conductive paste by any method in the same manner as in the related art.

In FIG. 2D, the conductive circuit patterns 12,
The metal films 15 are formed by immersion in Cu, Au, and SnPb plating while energizing 13 and 14.

In FIG. 2E, a protective film covering the whole of the conductive circuit patterns 12, 13, and 14, the jumper 17, the resist layer 16, and the metal film 15 formed on the insulating substrate 11 is the same as the resist layer 16. A resist is printed on the substrate and cured by any method, so that a resist layer 18 is formed.

In the flexible wiring board 20 according to the embodiment of the present invention having such a configuration, the jumper portion 17 is formed on the insulating substrate 11 before the metal film 15 is plated on the surface of the conductive circuit pattern. Therefore, the jumper portion 17 and the metal film 15 do not substantially contact with each other, and thus the contact with the jumper portion 17 is the conductive circuit patterns 12 and 14 having the metal film 15. Since a film having a high resistance is not formed, there is no inconvenience that the conductor resistance at the interface between the conductive circuit patterns 12 and 14 and the jumper portion 17 increases.

[0030]

As is apparent from the above description, in the flexible wiring board according to the present invention, since the jumper portion does not come into contact with the metal film, an oxide film formed on the surface of the metal film or a coating on the metal film is not formed. Due to the antioxidant film, the conductor resistance at the interface is increased, and as a result, it is not necessary to consider the adverse effect such that the electric efficiency is deteriorated, so that the degree of freedom in circuit design is increased.

Further, since the metal film and the jumper portion are formed so as not to be in contact with each other by the method for manufacturing a flexible wiring board according to the present invention, the oxide film formed on the surface of the metal film or the metal film is coated. The anti-oxidation film increases the conductor resistance at the interface, and as a result, it is not necessary to consider adverse effects such as a decrease in electrical efficiency, thereby increasing the degree of freedom in circuit design.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a flexible wiring board according to the present invention.

FIG. 2 is a process chart showing one embodiment of a method for manufacturing a flexible wiring board according to the present invention.

FIG. 3 is a cross-sectional view showing the structure of a conventional flexible wiring board.

FIG. 4 is a process chart showing a conventional method for manufacturing a flexible wiring board.

FIG. 5 is a cross-sectional view showing a measure for preventing metal film oxidation in a conventional flexible wiring board.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Insulating substrate 12, 13, 14 Conductive circuit pattern 15 Metal film 16 First resist layer 17 Jumper part 18 Second resist layer 20 Flexible wiring board

Claims (3)

[Claims] A plurality of conductive circuit patterns having a metal film on a surface are formed on a flexible insulating substrate, and two or more arbitrarily selected ones of the plurality of conductive circuit patterns are formed. A flexible wiring board having a jumper portion electrically connected to a conductive circuit pattern and located between the two or more conductive circuit patterns and formed so as not to contact another conductive circuit pattern, A resist layer is formed on the upper surface of the part, so that it is electrically insulated from the jumper part,
A flexible wiring board, wherein another conductive circuit pattern located between the two or more conductive circuit patterns is formed on an upper surface of the resist layer. 2. A first step of forming a conductive jumper on a flexible insulating substrate, and the jumper excluding this end so that the end of the jumper becomes a connection. A second step of forming a first resist layer on the upper surface of the substrate, and forming, on the insulating substrate, first and second conductive circuit patterns that are in contact with the connection portion of the jumper portion and are electrically conductive. A third step of forming a third conductive circuit pattern on the upper surface of the first resist layer, and a fourth step of forming a metal film on the upper surface of the first, second, and third conductive circuit patterns And a fifth step of forming a second resist layer so as to cover the jumper portion, the first resist layer, and the first, second, and third conductive circuit patterns formed on the insulating substrate. And at least, Of manufacturing flexible wiring boards. 3. A first step of printing and curing a conductive paste on a flexible insulating substrate to form a jumper, and a step of forming a jumper so that both ends of the jumper are exposed. Print the resist on the top surface and cure it first
A second step of forming a resist layer, and printing a conductive paste on the insulating substrate so as to be in contact with each of the exposed ends of the jumper portion, and at the same time, on the upper surface of the first resist layer. A third step of printing and curing a conductive paste to form a circuit to form first, second, and third conductive circuit patterns; and forming the first, second, and third conductive patterns. A fourth step of forming a metal film by plating on the conductive circuit pattern, and the jumper portion formed on the insulating substrate;
A resist is printed and cured so as to cover the third conductive circuit pattern, the metal film, and the first resist layer.
And a fifth step of forming a resist layer according to (1).