JPH0680875B2 - Printed board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION “Object of the Invention” The present invention relates to the invention of a printed circuit board, which has a low dielectric constant, an appropriate mechanical strength, and a variation in its electrical characteristics depending on external conditions. It is an object of the present invention to provide a printed circuit board that does not have an etching process and can appropriately perform an etching process for obtaining a printed wiring board.

Industrial application fields Printed circuit boards used in electronic devices, especially computers that require high-speed signals.

2. Description of the Related Art The following is a conventional printed wiring board used in electronic devices and the like.

A glass epoxy base material or a paper epoxy base material obtained by impregnating and hardening glass cloth or paper with an epoxy resin, or a paper phenol base material obtained by impregnating and hardening a paper resin with a phenol resin.

Flexible insulating base material such as polyimide film and polyester film.

A heat resistant printed wiring board made of a composite material of glass fiber and polyimide.

Low dielectric constant base materials such as epoxy Kevlar, polyimide Kevlar, and epoxy oats.

Low dielectric constant substrate made of glass cloth and tetrafluoroethylene resin.

Problems to be Solved by the Invention However, the conventional ones as described above each have problems. That is, it is as follows.

Is a conventional one, but it has a high dielectric constant and is difficult to use in computers and the like that require high speed in recent years.

Similarly, a printed wiring board having a low dielectric constant cannot be obtained. By the way, the dielectric constants of these materials are as follows for a frequency of 1 MHz.

4.5-5.5 3.5-5.0 4.3-4.7 Even though it has excellent heat resistance, its dielectric constant is 3.5-5.5.
Around 4.0 does not satisfy the above-mentioned purpose.

Has a low dielectric constant of 2.5 to 3.0 and is considered to be a low dielectric constant base material, but it has a problem in adhesion to copper foil and has a difficulty in workability.

"Structure of the Invention" Means for Solving Problems The polytetrafluoroethylene porous body is used as an insulating base material,
A printed circuit board on which an electric conductor for forming an electric circuit is fixedly formed on one or both sides, or a polytetrafluoroethylene porous structure is formed of an epoxy resin, a polyimide resin, a polyester resin, an acrylic resin, a triazine resin, a bismaleimide / triazine resin. In a printed circuit board on which an electric circuit-forming conductor is fixedly formed on one or both sides of an insulating substrate impregnated and cured with one or more heat-resistant resins or low-dielectric constant resins having a dielectric constant of 3.2 or less, A printed circuit board, wherein an airtight coating layer is formed on a portion where the material directly contacts the atmosphere.

Action A low dielectric constant substrate can be obtained by impregnating the polytetrafluoroethylene porous structure itself or the polytetrafluoroethylene porous structure with a heat resistant or low dielectric constant resin.

The airtight coating layer of heat-resistant or low-dielectric constant resin formed on the peripheral surface of the substrate prevents external air, especially moisture, from entering the structure of the substrate, and changes in the low-dielectric constant characteristics as described above, particularly deterioration. Take care of.

Further, the coating layer as described above prevents the etching solution from invading the structure of the substrate during the etching process for forming the printed wiring on the substrate, so that unnecessary etching or characteristic change due to residual etching liquid components is prevented. To prevent.

EXAMPLE To further explain the present invention as described above, there is a strong demand for speeding up of signals in the above-mentioned computer and the like. Therefore, since an ultra-high speed element made of gallium arsenide or the like has been developed, It is strongly desired to respond to the speedup. That is, the signal propagation delay time τ in such a case is proportional to the square root of the dielectric constant of the material, and is expressed by the following equation in the strip line.

However, ε: permittivity of material, C: speed of light 3 × 10 ⁸ m / sec. Therefore, it is indispensable to reduce permittivity ε of material in order to respond to signal speedup immediately.

In the present invention, the polytetrafluoroethylene porous structure 1 has a low dielectric constant by itself, and was devised by repeated studies to meet such technical requirements. For example, the porosity is 80%. It has a very low dielectric constant of 1.2. In addition, in order to increase the mechanical strength of the polytetrafluoroethylene porous tissue body against tensile and compression forces, other resin components may be impregnated and cured in the porous body to obtain a low dielectric constant substrate.

However, as described above, in the polytetrafluoroethylene porous tissue or the porous body impregnated with a low dielectric constant or heat resistant resin, pores still remain in the tissue, which may cause a circuit formation. At the time of etching, the etching liquid penetrates into the pores to form unnecessary etching, and residual adhesion of the components of the etching liquid cannot be avoided. Invades and adversely affects the insulation and dielectric properties.

The invention according to the present invention, which has been proposed to solve the above-mentioned technical relationship, is as shown in the accompanying drawings, in which innumerable fine particles are formed between the fine knots 11 by rolling or stretching the polytetrafluoroethylene film. The fibers 12 form the porous tissue body 1 formed in the shape of a spider web.

Further, one or more kinds of heat-resistant resin such as epoxy resin, polyimide resin, polyester resin, acrylic resin, triazine resin, bismaleimide triazine resin or low dielectric constant resin having a dielectric constant of 3.2 or less on the peripheral surface of the substrate. Is coated to form an airtight coating layer. Further, the one according to the present invention, which is proposed in order to enhance the mechanical strength against the tensile force and the compressive force of the polytetrafluoroethylene porous structure and to solve the above-mentioned technical relationship, is as shown in the drawing, By rolling and stretching the tetrafluoroethylene film, the porous tissue body 1 is formed in which a myriad of fine fibers between the fine nodules 11 are formed in a web-like shape. An epoxy resin as described above as a resin solution preferable as such a substrate for such a porous tissue body 1,
1 of heat resistant resin such as polyimide resin, polyester resin, acrylic resin, triazine resin, bismaleimide triazine resin or low dielectric constant resin having a dielectric constant of 3.2 or less
Impregnate and cure one or more seeds. For impregnation of such a resin component, vacuum impregnation or pressure impregnation can be adopted, and the impregnated resin 2 is formed in the tissue.

Further, the same or other resin as the impregnating resin 2 is coated on the peripheral surface of such a base material to form the airtight coating layer 3.

That is, the mechanical strength of the polytetrafluoroethylene porous tissue body 1 is improved by the impregnating resin 2 that has penetrated into the porous tissue body 1. Polytetrafluoroethylene resin generally has a heat resistance of about 260 ° C. and does not impair the heat resistance of the impregnated heat resistant resin. The airtight coating layer 3 blocks the outside air to prevent the etching liquid from entering, enables the etching of a fine circuit pattern, and avoids the deterioration of the insulating property and the dielectric property due to the intrusion of moisture or the like. Furthermore, for the resin coated around the polytetrafluoroethylene porous structure, the mechanical strength against tensile and compressive force is also improved, and the adhesive effect with the metal foil due to the anchor effect of the resin on the porous structure. Also improves.

A concrete production example of the device according to the present invention is as follows.

A porous polytetrafluoroethylene film with a thickness of 0.09 mm and a porosity of 77% was impregnated with a bismaleimide triazine resin varnish and then cured to form a base material with a porosity of 27%.
Then, the bismaleimide triazine resin varnish was coated on the peripheral surface of this product to form an airtight coating layer, and a product having a total thickness of 0.10 mm as shown in the accompanying drawings was obtained.

That is, the results of measuring the water absorption of this product are shown in Table 1 below.
As shown in, the water absorption is remarkably different.

Separately, the results of measurement of the dielectric constant and the volume resistivity after the moisture absorption treatment are shown in Table 2 below. In all cases, the one with the coating layer according to the present invention is excellent and the pattern width of the substrate, the line length, etc. It has been confirmed that it is an excellent printed wiring board that can be advantageously designed and that its characteristics are not changed by moisture etc. when used in the atmosphere.

Other specific manufacturing examples are as follows. A porous polytetrafluoroethylene film having a thickness of 0.09 mm and a porosity of 77% is coated with an epoxy resin to form an airtight coating layer, and the overall thickness is 0.10 mm as shown in the drawing. Got the product. The dielectric constant of this product is 1.8
It was confirmed that the printed wiring board was extremely low, and its characteristics did not fluctuate due to moisture when used in the atmosphere.

[Advantages of the Invention] According to the present invention as described above, it is possible to obtain a printed circuit board having a low dielectric constant or heat resistance, which is suitable for the purpose of speeding up signals, such as a computer. It is possible to provide a printed circuit board which has strength and does not cause performance deterioration during etching or characteristic variation or deterioration due to attachment of moisture from the outside air, and is an invention having a great industrial effect.

[Brief description of drawings]

1 is a perspective view showing the technical contents of the present invention, in which a printed circuit board according to the present invention is cut and enlarged to show a cross section. However, in this drawing, 1 is a polytetrafluoroethylene porous tissue, 2 is an impregnated resin, 3 is an airtight coating layer by coating, 11 is a fine nodule of the porous tissue 1, and 12 is a fine fiber thereof. It is a thing.

Claims (1)

[Claims] 1. A printed circuit board having a polytetrafluoroethylene porous body as an insulating base material, on one or both sides of which a conductor for forming an electric circuit is fixedly formed, or a polytetrafluoroethylene porous body having an epoxy resin, Heat resistant resin such as polyimide resin, polyester resin, acrylic resin, triazine resin, bismaleimide / triazine resin or low dielectric constant resin having a dielectric constant of 3.2 or less 1
In a printed circuit board on which an electric conductor that forms an electric circuit is fixedly formed on one or both sides of an insulating base material that is impregnated and cured with one or more species, it is necessary to form an airtight coating layer on the part where the insulating base material and the atmosphere directly contact Characterized printed circuit board.