JPH0538783A - Composite body and use therefor - Google Patents

Abstract

(57) [Abstract] [Purpose] To improve the adhesive force between a copper foil and a prepreg in a circuit board in which a prepreg impregnated with a fluororesin and a copper foil are bonded to a cloth-like substrate. [Structure] A composite having a non-fired thin layer of fluororesin formed on a matte surface of a copper foil is prepared, and the non-fired thin layer of fluororesin of the composite is laminated on both sides of the fluororesin prepreg so as to face each other. This is heated and pressed to be integrated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a circuit board which can be used for producing a high frequency device such as an electronic device or a computer, or a high frequency communication device, and a composite useful as a material for the circuit substrate. ..

[0002]

2. Description of the Related Art As electronic equipment, computers and other high frequency utilization equipment or high frequency communication equipment, the matte surface of copper foil is laminated so that it faces a prepreg obtained by impregnating a cloth-like base material with fluororesin. A circuit board is known in which a circuit board is obtained by integrating the two by heating and pressing, and then a copper foil of the board is patterned.

[0003]

By the way, the above conventional circuit board has a problem that the adhesive force between the copper foil and the prepreg is weak. Microscopically, the copper foil matte surface is a rough surface having innumerable minute irregularities, and when the copper foil and the prepreg are adhered, the protrusions of the minute irregularities on the copper foil matte surface and the prepreg adhere, so the contact area is small, Therefore, it seems that the adhesive strength does not increase. Further, the improvement of the adhesive force between the copper foil and the prepreg on the circuit board or circuit board is an important problem, but a practical solution has not yet been found.

[0004]

In order to solve the above problems of the prior art, the present inventor has made earnest studies and found that an unfired thin layer of fluororesin was previously formed on a specific surface of a copper foil. The inventors have found that the objectives of the present invention can be achieved and completed the present invention.

That is, in the method for producing a circuit board substrate according to the present invention, a fluororesin dispersion is applied to the matte surface of a copper foil and dried to obtain a composite having an unfired thin layer of fluororesin. It is characterized in that the fluororesin unfired thin layers of the composite are laminated on both sides of the fluororesin prepreg so as to face each other, and heated and pressed to integrate the prepreg and the composite.

In the method of the present invention, first, a fluororesin dispersion is applied and dried on the matte surface of the copper foil,
A composite in which an unfired thin layer of fluororesin is formed on the mat surface is obtained. The amount of the fluororesin unfired thin layer attached to the copper foil in this composite is usually about 10 mg / cm ² or less, but it does not prevent the thickness from becoming thicker than this.
To form a fluororesin thin layer on the copper foil mat surface, for example, a fluororesin dispersion is applied to the copper foil mat surface by a spray method or the like and then heated to a temperature below the melting point of the fluororesin to remove the dispersion medium. It can be performed by a method. The thickness of the thin layer can be adjusted by repeating this application and drying a predetermined number of times. As the fluororesin dispersion, polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), ethylene-tetrafluoroethylene copolymer A polymer (ETFE) or the like dispersed in a dispersion medium such as water may be used. Of course, it is also possible to use a dispersion in which two or more kinds of fluororesins are mixed and dispersed. The fluororesin concentration in the dispersion is not particularly limited,
Usually, it is about 30 to 70% by weight.

Due to the manufacturing method of copper foil, one side is usually a rough side called mat, and the other side is shiny.
It is known to be a mirror surface called iny) surface,
It is also recognized that the matte surface has innumerable minute irregularities and has a surface roughness larger than that of a mirror surface. And since these two sides can be easily distinguished visually,
The work of applying fluororesin dispersion to the copper foil mat surface can be done easily.

After the composite is obtained in this manner, the fluororesin unfired thin layers of the composite are superposed on both surfaces of the fluororesin prepreg so as to face each other and heated and pressed to integrate the composite on both surfaces of the prepreg. By doing so, a circuit board is obtained. Examples of the prepreg include cloth-like base materials (woven cloth, non-woven cloth, mesh-like sheet, etc.) made of glass fiber, asbestos fiber, alumina fiber, boron fiber, silicon carbide fiber, titania fiber, boron nitride fiber, aromatic polyamide fiber and the like. It is possible to use a single-layer product obtained by impregnating (1) with a fluororesin dispersion and then heating, or a laminate of a predetermined number of the single-layer products. The heating temperature during the production of the prepreg is usually equal to or higher than the melting point of the fluororesin, but in some cases it may be a low temperature below the melting point (however, equal to or higher than the evaporation temperature of the dispersion medium).

The temperature at which the prepreg and the composite are integrated should be equal to or higher than the melting point of the fluororesin, which is the constituent material of both. The pressure and heating / pressurizing time are set according to various conditions such as heating temperature, but normally the pressure is 10 to 70 kg / c.
m ² , the heating and pressurizing time is about 0.5 to 2 hours. At the time of this integration, a fluororesin film can be interposed between the prepreg and the composite.

By this heating and pressing, the prepreg and the composite are firmly integrated with each other to obtain the intended circuit board. It was confirmed that the adhesive strength between the copper foil and the prepreg in this circuit board substrate was large as shown in the following examples. The reason for this is not necessarily clear, but when the unsintered thin layer of fluororesin is formed on the matte surface of the copper foil, the fluororesin enters into the minute irregularities of the matte surface, and it becomes as if it was anchored, and becomes firm with the copper foil. It is presumed that this is because the flat thin layer is bonded to the fluorinated resin, which is a constituent material of the prepreg, and is firmly bonded to the prepreg.

To obtain a circuit board using this circuit board, a peeling development type photoresist, a solvent development type photoresist or an alkali development type photoresist is used in the same manner as in the conventional production of printed circuit boards. It is only necessary to pattern the copper foil of the substrate. For example, an alkali-development type photoresist layer is formed on the surface of a copper foil of a circuit board substrate, a pattern is exposed from above through a photomask, and then the unexposed portion of the photoresist is dissolved and removed to form a copper foil. Partially exposed, then the exposed portion of the copper foil is removed by etching, and the exposed portion of the photoresist is dissolved and removed by a solvent, whereby a circuit board having a patterned circuit corresponding to the exposed portion of the photoresist is formed. can get.

[0012]

The present invention will be described in more detail with reference to the following examples.

Example 1 (Production of Composite) A fluororesin aqueous dispersion was applied to the matte surface of an electrolytic copper foil having a thickness of 18 μm by a spray method and dried at a temperature of 80 ° C. for 10 minutes to obtain an unbaked fluororesin thin film. A composite with a layer (deposition 5 mg / cm ² ) formed is obtained. The fluororesin dispersion used had a weight ratio of PTFE to FEP of 100: 14 and a fluororesin concentration of 60% by weight.

(Production of prepreg) A glass cloth having a thickness of 50 μm was immersed in an aqueous dispersion having a PTFE powder concentration of 60% by weight and pulled up, and then at a temperature of 380 ° C. for 2 minutes.
Heat for minutes. This dipping and heating are repeated three more times to obtain a prepreg having a PTFE impregnation rate of 65%. In addition,
The impregnation rate is a value calculated by dividing the weight of the PTFE impregnated in the glass cloth by the weight of the obtained prepreg and multiplying this by 100.

(Production of Circuit Board Substrate) Eleven prepregs obtained as described above are superposed and a PTFE film having a thickness of 50 μm is arranged on both outer surfaces of the superposed body. Then, the composite is further laminated so that the unsintered thin layers of the fluororesin are on the side of the PTFE film, and heated and pressed under the conditions of a temperature of 380 ° C. and a pressure of 10 kg / cm ² for 60 minutes to form a circuit board substrate. Got

Copper foil and PTFE in this circuit board substrate
Adhesive strength with film at temperature of 25 ℃, pulling speed of 50mm /
When it was measured by a 90 ° peeling method using a tensile tester under the condition of min, it was 2.0 kg / cm.

Example 2 A circuit board was obtained in the same manner as in Example 1 except that an aqueous dispersion in which only PTFE was dispersed to a concentration of 60% by weight was used as the fluororesin dispersion. It was Copper foil and PTF on this substrate
The adhesive force with the E film was 1.9 kg / cm.

Comparative Example A circuit board substrate was obtained in the same manner as in Example except that the unbaked fluororesin thin layer was not formed on the surface of the electrolytic copper foil mat. The adhesive force between the copper foil and the prepreg in this circuit board substrate was 1.1 kg / cm.

[0019]

EFFECTS OF THE INVENTION The present invention is configured as described above, and the fluororesin unfired thin layer is formed on the copper foil mat surface prior to the joining of the copper foil and the prepreg. The adhesive strength can be improved.

Claims (2)

[Claims] 1. A composite body formed by forming an unfired thin layer of fluororesin on a matte surface of a copper foil. 2. A fluororesin dispersion is applied to the matte surface of a copper foil and dried to obtain a composite having an unfired thin layer of fluororesin, and then the fluororesin of the composite is formed on both surfaces of the fluororesin prepreg. A method for manufacturing a circuit board, characterized in that the unfired thin layers are superposed so as to face each other and heated and pressed to integrate the prepreg and the composite.