JPH0441443B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a printed circuit board that can be used as a highly reliable and inexpensive connector, voice coil, motor coil, etc.

(Prior Art) Recently, with the miniaturization and multifunctionalization of electronic devices, there has been a demand for connectors, coils, etc. that have high wiring density, excellent reliability, easy workability, and are economical.

Conventionally, a relatively high-grade connector is commercially available, in which a plastic socket equipped with conductive pins is connected to a sheet-like connector made of copper wire wrapped in polyvinyl chloride. Although this method has excellent reliability, it is expensive, and has a limitation in wiring density, making it difficult to handle high wiring density. Also, relatively inexpensive printed circuit films made of polyester film with conductive ink are used as connectors, but the leads can only be taken out from one side, and some parts cannot be connected. It has the disadvantage that it is difficult to use and requires a distance in the length direction of the printed circuit film. In order to increase the amount of current applied, a special thick film screen printing is required to increase the amount of ink applied, and the thick film does not dry sufficiently, causing blocking, so the film thickness is usually reduced. However, because of this, the conductivity is low, the adhesion to the substrate film is weak, and the mechanical strength of the coating film is also low.

Furthermore, as a slightly higher grade product than the above-mentioned printed circuit film, there is a film substrate on which a copper circuit is directly formed using a fully additive method using chemical copper plating. Although this type of film has a higher current flow rate than the above-mentioned printed circuit film, it has poor adhesion to the base material, making it difficult to form fine wiring, and is expensive due to poor productivity, which are unresolved technical issues. There are many problems. In addition, the above-mentioned film substrate has mechanical inconveniences, such as the leads can only be taken out from either the front or back surface, making it difficult to connect, and the distance in the length direction is large, making it difficult to arrange compactly. There are many points.

On the other hand, coils include low-frequency magnetic core coils made of copper wire wrapped around silicon steel or permalloy thin plates, and wire-wound coils with hollow rings, which are used for high frequencies. There is. However, these have the disadvantage of being expensive.

(Problems to be Solved by the Invention) The present invention provides a printed circuit that can be used as a connector or a coil, and which improves the conventional drawbacks and has excellent performance, reliability, and economical efficiency. It provides a substrate.

(Means for Solving the Problems) The present invention provides a circuit pattern with a density of 0.3 in which a circuit pattern is formed continuously in the vertical direction up to the back surface using conductive ink.
An anisotropically conductive adhesive layer is formed on at least one of the terminal portions on the front and back surfaces of a porous core material having a thickness of ~0.9 g/cm ³ and 0.02 to 0.4 mm, and the terminal portions on the front and back surfaces of the core material. This printed circuit board is characterized in that a resin layer is formed in addition to the above.

The present invention will be explained with reference to the drawings.

FIGS. 1 and 2 are a schematic diagram and a cross-sectional view of the printed circuit board of the present invention when it is used, for example, as a connector. A circuit pattern 2 is formed continuously on the porous core material 1 in the vertical direction from the front surface to the back surface using conductive ink, and other types of circuit boards are bonded to the terminals on the front and back surfaces of the core material 1. An anisotropically conductive adhesive layer 3 is formed for conduction, and a resin layer 4 is further formed on the front and back surfaces of the core material other than the terminals to protect and maintain strength of the core material. There is. As shown in the first embodiment, this printed circuit board has a function as a connector that directly connects the circuits of two sets of circuit boards.

FIGS. 3 and 4 are a schematic diagram and a sectional view of the printed circuit board of the present invention when it is used, for example, as a coil. A circuit pattern 2 is formed continuously on the porous core material 1 in the vertical direction from the front surface to the back surface using conductive ink, and an anisotropic conductive adhesive layer 3 is formed on the terminal portion at one end of the back surface of the core material 1. , and the terminal portion at the other end of the surface is formed with the core material exposed. The core material 1 is covered with a resin layer 4 made of prepreg except for the terminal portions on the front and back surfaces. As shown in FIG. 5, this printed circuit board is connected to a circuit to form a coil by overlapping and press-bonding the terminal portions on the front and back surfaces of the board.

The porous core material used in the present invention has a density of
Paper, woven and non-woven fabrics with porosity of 0.3 to 0.9 g/cm ³ are suitable for use. If the density is less than 0.3 g/cm ³ , it is likely to be cut when printed with conductive ink, resulting in poor workability. Also, if the density exceeds 0.9g/ ^cm3 , the permeability of the conductive ink to the core material will be extremely poor.
Not only does the conductivity deteriorate, but also the permeability of the resin when providing a protective layer as described later is impaired, making it impossible to obtain sufficient water resistance. The raw material fibers for woven fabrics and nonwoven fabrics are preferably fibers made from aromatic polyamide resins, polyethylene terephthalate resins, etc., fibers with good heat resistance such as glass fibers, and silica fibers. When the printed circuit board of the present invention is a flexible printed circuit board that requires high bending strength, it is preferable to use a woven or nonwoven fabric made of synthetic fibers such as aromatic polyamide resin or polyethylene terephthalate resin as a core material.

The core material used in the present invention is porous, so when a circuit pattern is printed on its surface with conductive ink, the ink penetrates into the core material and forms a vertically continuous circuit pattern on the back surface of the core material. can be done. For this purpose, a core material having a density within the above range is particularly preferable. As for the thickness of the core material
Those in the range of 0.02 to 0.4 mm are suitable for use.

The conductive ink used in the present invention is prepared from a conductive filler, a binder, an additive, a solvent, and the like. Examples of the conductive filler include powders of silver, copper, nickel, and other noble metals, and powders of carbon and graphite. Epoxy resin, phenolic resin, acrylic urethane resin, as a binder.
Synthetic resins with good heat resistance, such as unsaturated polyester resins, saturated polyester resins, and sialyl phthalate resins, are used depending on the use and purpose. A vinyl monomer or an allyl monomer may be used in combination with the resin, if necessary. As additives, conductive filler dispersants, leveling agents, and other various compounding agents used in the technical field are used as necessary. As the curing catalyst for the binder, a curing agent suitable for each resin is selected. The solvent is appropriately selected to have solubility and adhesive properties depending on the type of binder used.

To form a circuit pattern on a porous core material,
This is carried out by printing using a screen printer or the like using the above conductive ink. On this occasion,
The conductive ink has a viscosity of 100 to 2000 poise (25
It is desirable to choose one that is within the range of

If an ink with a lower poise than 100 poise is used, there is a risk that it will penetrate not only vertically but also horizontally into the core material and cause conduction to adjacent circuits that should be insulated. or
If an ink higher than 2000 poise is used, it will be difficult for the ink to penetrate into the core material, making it difficult to form a continuous circuit to the back surface.

Next, the core material on which the circuit pattern is printed is dried and cured. After thoroughly drying the solvent contained in the conductive ink by air-drying or heat treatment, the conductive ink is cured by heating. The heating temperature and time are selected mainly depending on the type of binder of the conductive ink and the type of core material. Usually, it is sufficient to heat it for 5 minutes or more at 130 to 240°C after drying to the touch. If curing is insufficient, the specified electrical performance may not be achieved, or
Furthermore, when reinforcing the substrate or applying silver ink, a resin layer is formed on the surface of the substrate by impregnation or coating in order to prevent migration and to impart heat resistance, water resistance, and solvent resistance. This is not preferable because the ink will be redissolved.

The components of the so-called anisotropic conductive adhesive layer, which is conductive in the thickness direction and insulating in the surface direction and is formed on the porous core material in the present invention, are already known, and the adhesive has insulating properties. This adhesive is made of conductive particles mixed and dispersed in it, and has the function of interposing it between two sets of circuit boards and bonding them under pressure to electrically connect both circuits. It has the following. Components of the anisotropically conductive adhesive layer of the present invention include anisotropically conductive adhesives, pressure-sensitive adhesives, elastomers, and anisotropically conductive materials formed by forming these adhesives into tape shapes. is used.

In the printed circuit board of the present invention, the anisotropically conductive substance is coated or pasted by screen printing or by using a spacer on the portions that will become terminals on either or both of the front and back sides of the porous core material on which the circuit pattern is formed and cured. It is produced by laminating layers by laminating or the like. The thickness of the anisotropic conductive adhesive layer is 10 μm for conductive performance.
It is preferable to laminate m or more. However, if the film is too thick, the adhesive layer itself may be destroyed and conduction may be interrupted when the film is used as a connector or the like, so the thickness is preferably about 50 μm at most. By selecting the type of anisotropic conductive material used for the adhesive layer to be laminated, it can be used as an adhesive layer when used as a connector, etc., when permanently adhering to other circuit boards, or when adhering to other circuit boards in a removable manner. be able to.

In order to impart mechanical strength, heat resistance, water resistance, electrical properties, solvent resistance, etc. to the printed circuit board of the present invention, the front and back surfaces of the printed circuit board other than the terminal portion including the anisotropically conductive adhesive layer portion are A resin layer is formed by impregnation or coating. The resin used is
For example, thermosetting resins such as epoxy resin, phenolic resin, vinyl ester resin, unsaturated polyester resin, diallyl phthalate resin, thermosetting polybutadiene, thermoplastic resins such as ABS resin, polyvinyl chloride, acrylic resin, polyester resin, etc. Chloroprene, chlorinated polyethylene, NBR,
Examples include elastomers such as EPDM. These resins are dissolved in a solvent such as acetone, methyl ethyl ketone, toluene, ethyl acetate, etc., and a curing catalyst, curing accelerator, crosslinking agent, thickener, etc., and if necessary, a filler and an inorganic or organic coloring agent are added thereto. Prepare a resin liquid by dipping or coating the parts of the printed circuit board other than the terminals, including the anisotropically conductive adhesive layer, to form a protective layer of resin, and after drying to the touch, cure the resin. It can be formed by Drying may be carried out by heating at a temperature higher than the boiling point of the solvent used, for example 70 to 150°C, for 5 minutes or more. Curing is usually carried out by heating at 130 to 200°C for 10 minutes or more.

In addition to the method described above, the resin layer can also be formed by heating and laminating other woven fabrics, non-woven fabrics, etc. using prepregs impregnated with resin by hot pressing or the like.

When forming the resin layer, the protective layer preferably has a resin amount in the range of 100 to 300 parts by weight based on 100 parts by weight of the core material.

(Effects of the Invention) The printed circuit board of the present invention can be used as a connector because the circuit becomes conductive by bonding it to another rigid circuit board via an anisotropically conductive adhesive layer using a press or the like. . On this occasion,
Since the circuit of the printed circuit board of the present invention is conductive from the front surface to the back surface, it can be directly connected to another circuit board by forming an adhesive layer on the back surface of one end of the front surface and the other end. Further, by forming an adhesive layer on the end of the substrate, making it cylindrical, and connecting a circuit to the other end by crimping, it can be used as a voice coil or a motor coil. In addition, since the printed circuit board of the present invention is protected by a resin layer except for the portions containing the anisotropically conductive adhesive layer that serve as terminals, the board itself has high mechanical strength, and has high heat resistance and water resistance. etc. is also excellent.

(Example) Example 1 Polyester resin nonwoven fabric with a density of 0.45 g/cm ³ and a thickness of 0.66 mm (“JH-3003” manufactured by Nippon Vilene Co., Ltd.)
Ink ("ED") made of conductive silver paste is applied to the surface of
-427SS (manufactured by Nippon Acheson Co., Ltd.), a circuit pattern with a width of 1 mm, a circuit gap of 1 mm, a length of 50 mm, and 10 circuits, with the ink penetrating to the back side, was screen printed, and after it was dry to the touch, it was heated at 130℃ for 20 minutes. The ink was cured. As shown in FIG. 1, an ink made of an insulating resin liquid ("ED-411SS" manufactured by Acheson Japan Co., Ltd., ) and dried at 130°C for 10 minutes. In the same manner, the entire surface of the back side was printed with ink except for the terminal portion, and then dried. Next, apply a tape-shaped anisotropic conductive adhesive (Morphit HM-
1000 (manufactured by Daiso) was temporarily bonded and then heated at 150℃ for 10
The adhesive layer was transferred to the circuit board by pressing at Kg/cm ² for 1 second, thereby producing a printed circuit board from which leads could be taken out from the front surface at one end and the back surface at the other end.
A schematic diagram of the circuit board is shown in FIG.

The printed circuit board prepared above was used as a connector, and an anisotropically conductive adhesive layer at one end and an anisotropically conductive adhesive layer at the other end were connected to glass-based epoxy resin copper-clad laminates (1.6 mm thick) ( "Ed Light
CCL-E300 (manufactured by Mitsubishi Gas Chemical Co., Ltd.) and a liquid crystal panel (manufactured by Optrex Co., Ltd.) with a circuit made of indium oxide film ^. in 10
A liquid crystal panel component was produced by pressing the wires together in seconds. When current was passed through this liquid crystal panel component, characters and figures were clearly displayed on the liquid crystal panel, confirming that it was working normally.

Example 2 The same conductive ink as in Example 1 was applied to the surface of a polyester resin non-woven fabric ("Hayale C40HR" manufactured by Miki Tokushu Paper Co., Ltd.) with a density of 0.74 g/cm ³ and a thickness of 0.054 mm, with a width of 1.5 mm and a circuit spacing of 1.5 mm. mm, length 70mm, number of circuits
A circuit pattern with ink penetrating the backs of 50 lines was screen printed, and after drying to the touch, the ink was cured by heating at 130°C for 20 minutes. Next, as shown in FIG. 3, a 0.08 mm thick aramid nonwoven fabric was impregnated with a composition made of diallyl phthalate resin, except for the terminal area on which the anisotropically conductive adhesive layer 3 was laminated on the back side and the terminal area on the front side. A coverlay material for circuit protection ("P-1045B" manufactured by Daiso Corporation) was layered on both sides of each layer and pressed at 130° C. and 30 kg/cm ² for 15 minutes.
Next, a tape-shaped anisotropic conductive adhesive was transferred onto the terminal portion in the same manner as in Example 1 to produce a printed circuit board. A schematic diagram of the circuit board is shown in FIG.

The above-mentioned printed circuit board is made into a cylindrical shape as shown in Fig. 5, and the adhesive layer is overlapped with the other end to connect the circuit.
A voice coil (Fig. 5) was prepared by pressing at 150°C and 10 kg/cm ² for 15 seconds. When the obtained voice coil was attached to a speaker, connected to a recorder, and electricity was applied, normal sound was obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of the printed circuit board obtained in Example 1, and FIG. 2 is a sectional view taken along line BB' in FIG. FIG. 3 is a schematic diagram of the printed circuit board obtained in Example 2, and FIG. 4 is a schematic diagram of the printed circuit board obtained in Example 2.
It is a C′ cross-sectional view. FIG. 5 is a schematic diagram of an application example using the printed circuit board obtained in Example 2. 1: porous core material, 2: circuit, 3: anisotropic conductive adhesive layer, 4: resin layer.

Claims (1)

[Claims] 1 A circuit pattern is formed continuously in the vertical direction to the back surface using conductive ink, with a density of 0.3 to 0.9 g/
cm ³ and a thickness of 0.02 to 0.4 mm, an anisotropically conductive adhesive layer is formed on at least one of the terminal parts on the front and back sides of the porous core material, and a resin layer is formed on at least one of the terminal parts on the front and back sides of the core material. A printed circuit board characterized by being formed with.