JPH05121872A - Manufacture of curved circuit board - Google Patents

Abstract

PURPOSE:To provide a method for easily manufacturing a curved circuit board wherein a circuit formed of metallic foil is provided on a curved surface without requiring a conductive paste and curved surface print method for circuit formation. CONSTITUTION:A manufacturing method of a curved circuit board which is formed of a resin impregnated base material and a circuit formed on its surface and which is formed by laminating a substrate 1 wherein resin of the resin impregnated base material is cured not to have flowability in a following formation process and an uncured resin impregnated base material 2 wherein resin flows to show adhesion in a following formation process and by pressurizing and heating for formation by dies 5, 6 whose pressurizing surface is curved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a curved circuit board.

[0002]

2. Description of the Related Art Conventionally, most printed circuit boards have a flat plate shape. However, recently, a circuit board provided with a circuit on an insulating curved molded body such as a radar for military use has also been proposed. First, make an insulating curved surface molding by injection molding,
The conductive paste is printed on the surface according to the circuit pattern by the curved surface printing method.

However, in the case of the curved surface printing method, since the printing surface is not flat, a special printing machine is required and the printing itself is not easy. In addition, the circuit formed by the conductive paste has high resistance and is not suitable for high frequency applications, and a special three-dimensional exposure device is required to cure the conductive paste. In order to avoid using the conductive paste, stack the metal foil on the required number of prepreg laminates, press and heat mold with a mold with a curved pressure surface, and then pattern the metal foil. It is possible to form a circuit by doing so. The circuit can be made of metal foil. However, in the case of this method, wrinkles are easily formed in the metal foil, and patterning of the metal foil formed into a curved surface is accompanied by curved surface printing of the resist material.

[0004]

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention provides a curved circuit board in which a circuit made of metal foil is provided on a curved surface without requiring a conductive paste and a curved surface printing method for forming a circuit. It is an object to provide a method that can be easily manufactured.

[0005]

In order to solve the above problems, in the method for manufacturing a curved circuit board according to the present invention, the resin of the resin-impregnated base material is composed of a resin-impregnated base material and a circuit formed on the surface thereof. Is a substrate that has been cured to the point where it has no fluidity in the next molding step, and an uncured resin-impregnated base material on which the resin flows and exerts adhesive strength in the next molding step. It is designed so that it can be heated under pressure with the mold.

The present invention will be specifically described below. First, a substrate which is composed of a resin-impregnated base material and a circuit formed on the surface of the resin and is cured to the extent that the resin of the resin-impregnated base material does not have fluidity in the next molding step (hereinafter, referred to as "circuit board"). To say). A metal foil is placed on one or both sides of a prepreg (uncured resin-impregnated base material) that is obtained by impregnating and drying a glass cloth (reinforcing material) with a resin composition, and there is no resin flow in the curved surface molding process that is a post process. Make a flat metal foil-clad substrate that is hardened to a degree. The reinforcing material is not limited to a cloth-shaped material, but may be a mat-shaped material or a fiber-shaped material. Copper foil is desirable as the metal foil,
It is not limited to this. Examples of the resin include PPO (polyphenylene oxide) resin and epoxy resin.

Next, the metal foil of the metal foil-clad substrate is patterned by a usual method to form a circuit (conductive pattern).
For example, patterning is performed by applying a photosensitive resist material → exposure → developing → etching. At this time, the unnecessary metal foil on the surface in contact with the inner layer is removed by etching or physical method. In this way, a circuit board is obtained. The patterning of the flat metal foil makes it extremely easy to process. The thickness of the circuit board is 200 μm or less, particularly 120 μm or less when a curved circuit board having a small size is manufactured. If it is too thick, curved surface molding becomes difficult.

An uncured resin-impregnated base material (hereinafter referred to as "uncured base material") in which a resin flows and exhibits an adhesive force in a curved surface molding process.
To say)). If a prepreg is made by impregnating and drying a glass cloth (reinforcing material) with a resin composition, this becomes an uncured base material. The thickness of this uncured substrate is 200 μm
The following are preferred. If it is too thick, curved surface molding becomes difficult. For the circuit board and the uncured base material prepared as described above,
Before performing the curved surface molding, it is preferable to cut by laser processing to partially remove or make a cut so that there is no overlap or void during molding. The curved surface molding accuracy is improved, and the circuit is accurately positioned at a predetermined place.

Then, as shown in FIG. 1, the circuit-equipped substrate 1 and a plurality of uncured base materials 2 are superposed and set between upper and lower molds 5 and 6 each having a curved pressing surface, and heated under pressure. When molded, the curved circuit board 3 is obtained as shown in FIG. Normally, the circuit board with the circuit is arranged on each of the uppermost layer and the lowermost layer, and plural uncured base materials are arranged between them, but not limited to this.
For example, the circuit board may be arranged only on the uppermost layer.

Examples of the molded curved surface include, but are not limited to, a dome-shaped curved surface corresponding to a part of a spherical surface. Inorganic particles may be dispersed in the resin of the circuit board or the uncured base material. Inorganic particles are dispersed in order to adjust the dielectric constant, thermal expansion coefficient, thermal conductivity and the like. For example, in order to increase the dielectric constant, TiO
Particles such as ₂ , BaTiO ₃ and PbZr _0.5 Ti _0.5 O ₃ are used.

The ratio of the resin to the reinforcing material in the circuit board and the uncured base material is 30 to 80 vol.
%, The remaining reinforcing material, when inorganic particles are used in combination,
The ratio of the resin, the inorganic particles and the reinforcing material is 30 to 7 for the resin.
5 vol%, 5 to 32 vol% of inorganic particles, and the remaining reinforcing material. Applications of the curved circuit board obtained by the method of the present invention include, but are not limited to, satellite broadcast antennas and circuit boards for decorative watches.

[0012]

In this invention, the resin of the resin-impregnated base material is cured to such an extent that it does not have fluidity in the next curved surface forming step by superposing the metal foil on the resin-impregnated base material and pre-curing it. Since the circuit can be formed by patterning the metal foil-clad resin-impregnated base material by a usual method, the circuit can be easily formed before the curved surface processing. Therefore, it is not necessary to use the conductive paste for forming the circuit, and it is not necessary to perform the difficult curved surface printing of printing the conductive paste or the resist material on the curved surface. No expensive and special equipment is required. A circuit formed of a metal foil has a lower resistance than a circuit formed of a conductive paste and is suitable for high frequency applications.

If the circuit-equipped substrate is deformed during curved surface molding, the circuit may be damaged. However, in the case of the present invention, the circuit board is sufficiently reinforced with a reinforcing material,
Since the resin is cured to the extent that it does not have fluidity, no deformation occurs even when forming a curved surface, and the circuit does not break or wrinkles. Since the uncured resin-impregnated base material that is laminated on the base material on which the circuit is formed contains a reinforcing material, it is elastic and easy to handle even if it is thin.

Since the obtained curved circuit board naturally contains a reinforcing material, it is hard to be deformed and has a good retainability of the curved shape.

[0015]

EXAMPLES Next, examples of the present invention will be described. The present invention is not limited to the following embodiments. -Example 1-1000 parts of trichlorethylene to 100 parts by weight of PPO resin
A varnish was prepared by adding parts by weight and stirring until the resin was completely dissolved.

This varnish is 600 mm long x 600 mm wide
Was impregnated with a plain woven glass cloth (thickness: 80 μm, fiber diameter: 7 μm) and dried at about 50 ° C. to obtain a prepreg with a thickness of about 150 μm. Prepreg is also used for uncured substrates. A copper foil with a thickness of 17 μm is placed on the front and back of one sheet of this prepreg and the temperature is set to 2
Pressure molding is performed under the conditions of 50 ° C. and a pressure of 33 kg / cm ² for 10 minutes to obtain a flat double-sided metal foil-clad substrate in which the resin is cured to the required extent. The insulating layer (dielectric layer) of this substrate had a thickness of about 140 μm.

Then, a circuit board having a thickness of about 160 μm was obtained by a method of applying a resist material on the front side metal foil by screen printing and performing an etching treatment. The metal foil on the back side was completely removed by etching.
The purpose of providing the metal foil on the back side that is to be removed is to prevent the metal foil from adhering to the mold during molding during copper foil bonding and to prevent the substrate from warping. If the substrate has a warp, it is difficult to form a pattern.

In the circuit board and the prepreg, the resin was 60 vol% and the remaining reinforcing material was used. Next, the circuit board 1 and the prepreg 2 are laser-processed so that there are no overlaps or voids when forming a curved surface, as shown in FIG.
Some were removed. Next, a circuit board with a circuit is arranged on the uppermost layer and the lowermost layer, and 20 uncured base materials are arranged between them, and the pressing surface is a dome-shaped curved surface with a radius of 490 mm. It was set between them, and was pressed and heat-molded under the conditions of a pressure of 40 kg / cm ² and 250 ° C. for 3 hours using a 400 ton press to obtain a curved circuit board. The side of the circuit board with no metal foil was in contact with the prepreg.

The obtained curved circuit board has a dome shape with a radius of 490 mm and a thickness of 3.0 mm and a relative dielectric constant of 3.2.
Met. -Example 2- The varnish impregnated in the glass cloth is PPO resin 110.
Parts by weight, 80 parts by weight of styrene-butadiene copolymer, 10 parts by weight of triallyl isocyanurate, 2.5-dimethyl-2,5-di- (tert-butylperoxy) hexyne-
A curved circuit board was obtained in the same manner as in Example 1 except that 4 parts by weight of 3, 3, 462 parts by weight of TiO ₂ particles and 1000 parts by weight of trichlorethylene were added.

In the case of the second embodiment, the circuit board and the circuit board
And prepreg resin is 37.2vol% vol%, T
iO₂Particles are 22.8vol%, the remaining reinforcing material,
The relative permittivity of the surface circuit board was 10.3. -Example 3-The varnish impregnated in the glass cloth is YDB-500.
(Brominated bisphenol A type epoxy resin: Tohto Kasei
87.5 parts by weight, YDCN-220 (cresol)
Novolac type epoxy resin: Toto Kasei Co., Ltd.) 12.5
Parts, 2.42% by weight of dicyandiamide, 2E4MZ
(2-ethyl 4-methylimidazole: manufactured by Shikoku Kasei)
0.1 parts by weight, DMF 9.7 parts by weight, methyl cellulose
19.4 parts by weight, MEK 47 parts by weight of epoxy FR-
4 compound varnish, the drying conditions after impregnating glass cloth are
150 ° C, 5 minutes, molding condition 33k in metal foil bonding process
g / cm ²130 ° C for 40 minutes, 175 ° C for 60 minutes
And And the condition of curved surface molding is 40 kg / cm²,
130 ° C, 40 minutes, 175 ° C, 90 minutes
A curved circuit board was obtained in the same manner as in Example 1.

In the case of Example 3, the circuit board and the prepreg contained 65 vol% of resin and the remaining reinforcing material, and the curved circuit board had a relative dielectric constant of 4.8. Example 4 In Example 1, a plain woven glass cloth having a thickness of 50 μm is used to obtain a prepreg of about 90 μm.
Other than the number of prepregs being 32 when forming a curved surface,
A curved circuit board was obtained in the same manner as in Example 1.

The thickness of the circuit board is about 110 μm.
m, and resin is 6 in the circuit board and prepreg.
2% by volume, the remaining reinforcing material, and the relative permittivity of the curved circuit board was 3.2. Example 5 In Example 2, a plain woven glass cloth having a thickness of 50 μm is used to obtain a prepreg of about 90 μm.
Other than the number of prepregs being 32 when forming a curved surface,
A curved circuit board was obtained in the same manner as in Example 2.

The thickness of the circuit board is about 110 μm.
m, the resin is 3 in the circuit board and prepreg.
8.4 vol%, 23.6 vol% of TiO ₂ particles, the remaining reinforcing material, and the relative permittivity of the curved circuit board was 10.4. -Example 6-In Example 3, a plain woven glass cloth having a thickness of 50 µm was used to obtain a prepreg of about 90 µm.
Other than the number of prepregs being 32 when forming a curved surface,
A curved circuit board was obtained in the same manner as in Example 3.

The thickness of the circuit board is about 110 μm.
m, and resin is 6 in the circuit board and prepreg.
6% by volume was the remaining reinforcing material, and the relative permittivity of the curved circuit board was 4.8.

[0025]

As described above, according to the manufacturing method of the present invention, the circuit can be easily formed before the curved surface is processed. There is no need for difficult curved surface printing such as resist material printing. Moreover, pre-curing of the reinforcing material of the circuit board and resin does not cause the circuit to break or wrinkle when forming the curved surface, and it also reinforces the uncured base material. Since it contains a material, it is easy to handle, and since the obtained curved circuit board also contains a reinforcing material, it has many advantages that it is difficult to deform and has a good retainability of the curved shape, which is very useful.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an example of a curved surface forming step in a method for manufacturing a curved circuit board according to the present invention.

FIG. 2 is an explanatory view showing a curved circuit board obtained by the manufacturing method of the present invention.

FIG. 3 is a plan view showing a substrate with a circuit and an uncured base material before performing curved surface molding in Example 1.

[Explanation of symbols]

 1 circuit board 2 uncured base material 3 curved circuit board 5 mold 6 mold

Claims (2)

[Claims] 1. A substrate comprising a resin-impregnated base material and a circuit formed on the surface of the substrate, wherein the resin of the resin-impregnated base material is cured to such an extent that it has no fluidity in the next molding step, and the next molding step. Then, a method of manufacturing a curved circuit board in which uncured resin-impregnated base materials in which a resin flows and exerts an adhesive force are overlapped and pressure-heat-molded by a mold having a curved pressure surface. 2. The method for manufacturing a curved circuit board according to claim 1, wherein an inorganic powder is dispersed in the resin.