JPH03297192A - Circuit board and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a circuit substrate whose bending workability is enhanced by installing organic or inorganic macromoles on an electric circuit layer in a bending work part. CONSTITUTION:An insulation layer 2 and an electric circuit layer 3 are installed on a metal base layer 1. A bending work section 31 of the electric circuit layer is covered with a protection layer 4 whose thickness ranges from around 10 to 1000mum. Organic or inorganic macromoles are used for the material of the protection layer. Preferably, they should be polyamide, si resin and the like with Young module ranging from 5000 to 100,000kg/cm<2> and electric insulating performance having volume resistivity of 10<9>OMEGAcm and over. This material is applied to a required section of the circuit substrate prior to bending work, and dried and hardened. This circuit substrate is easy to manufacture and enjoys excellent workability. Therefore, it is suitable to the production of equipment with high density packaging.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a circuit board that can be used for forming electric circuits of various electrical devices and electronic devices, and a method for manufacturing the same.

[Conventional technology]

2. Description of the Related Art With the recent trend toward miniaturizing electrical and electronic devices, there is a demand for miniaturization of various components used in these devices. As part of this, there is a demand for circuit boards to be bent and mounted in order to reduce the space factor.

Conventionally, as this circuit board, a metal base substrate has been used, which has a flexible insulating layer on a metal substrate such as aluminum, and further has an electric circuit layer made of a conductive metal such as copper on top of the flexible insulating layer.

[Problems that need to be solved]

By the way, the metal base substrate with the above structure does not have good bending workability, and when bent, for example, around 90 degrees, stress concentrates on the electrical circuit layer, which is generally thin and has low mechanical strength, causing it to break into the core layer. There is a problem of defects occurring. For this reason, there is a limit to the bending angle, and the actual situation is that miniaturization of the mounting board is not sufficient. Therefore, in view of the above problems, the present invention provides a circuit board with improved bending processability,
The object of the present invention is to provide a method for producing the same.

[Means to solve the problem]

The present inventors have found that the above problem can be solved by providing a layer of an organic polymer or an inorganic polymer on the electrical circuit layer of the bent portion.

Accordingly, the present invention provides a circuit board having an insulating layer and an electric circuit layer on a metal base layer, in which a bending protection layer made of an organic polymer or an inorganic polymer is provided on the electric circuit layer of the bent portion. A folding protection layer made of an organic polymer or an inorganic polymer is formed on the electric circuit layer of the portion to be bent of the circuit board having an insulating layer and an electric circuit layer on a metal base layer. The present invention relates to a method of manufacturing a circuit board, which is characterized in that the circuit board is then subjected to a bending process.

[Function and effect]

A bending protective layer is provided on the electrical circuit layer of the part of the circuit board that is to be bent, and then that part is bent using a press mold, for example, in the direction in which the electrical circuit is outward (in the direction in which the electrical circuit is stretched), or vice versa. Stress concentration on the electrical circuit can be avoided by bending in either direction (direction in which the circuit turns inward or direction in which the circuit is compressed by bending), and as a result, cutting defects in the electrical circuit layer are extremely reduced. Furthermore, the range of bending (bending angle, bending radius) is expanded, the mounting board can be made smaller, and the degree of freedom in bending is increased, making circuit design easier.

Therefore, since the circuit board of the present invention is easy to manufacture and has excellent bending workability, it can be suitably employed in the production of various electrical and electronic devices with high-density packaging.

〔Example〕

FIG. 1 shows a sectional view of an embodiment of the invention, and FIG. 2 shows a perspective view of an embodiment of the invention.

In these embodiments, an insulating layer 2 is provided on the metal base layer 1, and an electrical circuit layer 3 is provided thereon. Each layer may be composed of a material that has been conventionally used in this field or is well known. Therefore, examples of the constituent material of the metal base layer 1 include aluminum, copper, silicon steel, etc., and the insulating layer 2 Examples of the constituent material include polyimide, polyamide, glass fiber reinforced epoxy resin, etc., and examples of the constituent material of the electric circuit layer 3 include conductive metals such as copper, aluminum, nickel, silver, and gold.

Each layer may be bonded using a well-known adhesive.
Alternatively, when the insulating layer 2 is formed by electrodeposition coating, while the electrodeposition coating layer is in the B stage, layer Ill or layer 2 is placed on the electrodeposition coating and heated and pressurized to bring the electrodeposition coating layer to the C stage. and interlayer adhesion may be achieved at the same time.

The folded portion 31 of the electric circuit layer 3 is covered with a thin folding protection layer 4 having a thickness of, for example, about 10 to 1000 μm, in a well-adhered state. The folding protection layer 4 may cover the entire electrical circuit N3 as shown in FIG.
It is also possible to cover only 1.

An organic polymer or an inorganic polymer is used as the material for the bending protective layer 4, but it is difficult to use at least for the electric circuit layer 3, especially for the electric circuit layer 3 and the insulating layer 2, when bending the circuit board. It is preferable to use a material that exhibits good adhesion to the extent that it does not peel off. Note that if the material of the bending protective layer 4 has an excessively low mechanical strength, the protective effect will be poor, and if the material is excessively rigid, it will inhibit the bending processability of the circuit board.
100,000 kgf/cj, especially 8,000-50
．． 000 kgf/cffl is preferred. Examples of materials include polyamide, polyimide, polyamideimide, polyester, polyurethane, formal, silicone resin, epoxy resin, various ultraviolet curable resins, solder resist, and the like. Since it is often convenient for mounting the circuit board if the folding protective layer 4 is electrically insulating, it is preferable that the material constituting the layer is electrically insulating and has a volume resistivity of 09 Ω1 or more.

The bending protection layer 4 is formed by applying, for example, the above-mentioned resin varnish to the necessary parts of the circuit board before the bending process.
It can be formed by drying and further curing by irradiation with ultraviolet rays or electron beams, or heating if necessary.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to the same extent by these Examples.

Comparative Example 1 A polyimide film with a thickness of 25μ and having an adhesive layer with a thickness of 15μ on both sides was placed on an aluminum plate with a thickness of Q, 5+U, and then a copper foil with a thickness of 35μm was layered on top of it. Heat pressed at ℃, 60 minutes, 30 kg/-,
A circuit board material was obtained. Fifty square pieces were taken from this circuit board material, and then the copper foil layer was etched to create a width of 1 f.
A simulated electric circuit was formed by leaving a copper foil layer in the form of a dozen or so patterns of 50 mm in length and 50 mm in length.

Example 1 Epoxy resin was applied to the entire surface of the simulated electric circuit of the circuit board of Comparative Example 1 and cured (Young's modulus of the cured layer: approximately 17).
．． 000 kgf/c+J) thickness 20 μm (D-folding bending protective layer was formed).

Example 2 A folding protective layer having a thickness of 20 μm was formed in the same manner as in Example 1, except that a solder resist was used instead of the epoxy resin used in Example 1.

Each of the circuit boards of Examples 1 to 2 and Comparative Example 1 was bent at an angle of 90 degrees and 13 degrees in the direction in which the simulated electric circuit is outward (the direction in which it is stretched by bending) as shown in Figure 1 using a press mold.
5 degrees, bend RO, 5", 1.0" 1.5°, 2.
0'' bending process was carried out, and the presence or absence of breakage of the simulated electric circuit (crack in the pattern) was examined.The evaluation results are shown in the table below.

In the same table, if no abnormality was observed in the simulated electric circuit after the bending process, it is indicated by ○, and if cracks were observed, it is indicated by ×.

[Margin below]

Figure 1

[Brief explanation of the drawing]

1 and 2 show a cross-sectional view and a perspective view, respectively, of an embodiment of the invention. 1 Metal base layer 2 Insulating layer 3 Electric circuit layer 31 Bending portion 4 Bending protection layer (and above) Fig. 2

Claims (3)

[Claims] (1) In a circuit board having an insulating layer and an electric circuit layer on a metal base layer, a bending protection layer made of an organic polymer or an inorganic polymer is provided on the electric circuit layer of the bent portion. circuit board. (2) Young's modulus of the folded protective layer is 5,000 to 100
, 000 kgf/cm^2. (3) Forming a bending protection layer made of an organic or inorganic polymer on the electric circuit layer of the part to be bent of a circuit board having an insulating layer and an electric circuit layer on a metal base layer, and then performing the bending process. The method for manufacturing a circuit board according to claim 1 or 2, characterized in that: