JPH03157001A - Manufacture of lamination sheet and circuit board - Google Patents

Abstract

PURPOSE:To easily manufacture a lamination sheet and a circuit board with a large adhesive force between a fluorine resin impregnated fiber cloth and a metallic foil by arranging a porous fluorine resin sheet in contact with the metallic foil in the case of adhering the both. CONSTITUTION:In the case of prescribed number of fluorine resin impregnated cloth and metallic foil such as copper foil are overlapped and adhered, a porous fluorine resin sheet is interposed between them. The porous fluorine resin sheet of the same type of material as a fluorine resin impregnated in the fiber cloth such as PTFE, FEP, PFA, ETFE and PCTFE is used and the thickness is normally nearly 10-500mum, the porosity is nearly 20-95% and the porous diameter is nearly 0.01-100mum. The fluorine resin impregnated fiber cloth and the metallic foil are overlapped via the porous fluorine resin sheet, heated and pressed to melt the porous fluorine resin sheet and the fiber cloth and the metallic foil are adhered by using the sheet as an adhesives.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a laminate and a circuit board that can be used in high frequency ranges of electronic equipment, computers, etc. or microwave receiving antennas.

(Prior art) For high-frequency range or micro-receiving antennas for electronic equipment, computers, etc., the surface of fluororesin-impregnated fiber cloth is
A laminate in which metal foil is bonded with or without a fluororesin sheet (non-porous) is used (Japanese Unexamined Patent Publication No. 60-240436).

In order to use this laminate for the above applications, metal foil is patterned, but in recent years, in order to satisfy the demands for improving the performance of equipment, the line width of the pattern has been narrowed and the distance between the line widths has been shortened. Increasingly, efforts are being made to increase the density of materials (so-called fine patterning).

(Problem to be Solved by the Invention) By the way, various stresses are applied during the process of patterning metal foil in a laminate, so the adhesive strength between the fluororesin-impregnated cloth and the metal foil must be able to withstand these stresses. It won't happen.

Since the above-mentioned stress increases as the pattern becomes denser, the adhesive strength between the fluororesin-impregnated cloth and the metal foil is required to correspond to this.

However, the adhesion strength between the fluororesin-impregnated cloth and the metal foil in conventional products is not sufficient to meet such demands, and the fluororesin-impregnated cloth and the metal foil may peel off during patterning.

Therefore, an object of the present invention is to provide a laminate with improved adhesive strength between a fluororesin-impregnated cloth and metal foil, and a method for easily producing a circuit board formed by patterning the metal foil of the laminate. .

(Means for Solving the Problems) As a result of various studies to achieve the above object, the inventor of the present invention has discovered that a porous fluororesin sheet is interposed in contact with the metal foil when bonding the fluororesin-impregnated cloth and the metal foil. It was discovered that the adhesive strength between the two was improved, and the present invention was completed.

That is, in the present invention, a metal foil is placed on the surface of a fiber cloth impregnated with a fluorocarbon resin through a porous fluororesin sheet, and then the fiber cloth and the metal foil are made porous by heating and pressurizing them. It is characterized by being bonded using a high-quality fluororesin sheet.

In the present invention, fiber cloths conventionally used for manufacturing laminates or circuit boards can be used as they are. Specific examples of such fiber cloths include woven and non-woven fabrics made of inorganic fibers such as glass fibers, asbestos fibers, alumina fibers, boron fibers, silicon carbide fibers, titania fibers, and boron nitride fibers.

In the present invention, polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), ethylene-tetrafluoroethylene It is used by impregnating it with a fluororesin such as ethylene copolymer (ETFE) or polychlorotrifluoroethylene (PCTFE).

When the amount of fluororesin impregnated into the fiber cloth is large, the fluororesin penetrates into the inside of the fiber cloth and forms a thin layer on the surface of the cloth, and if the fiber cloth has a network, it may also block this network. be. On the other hand, when the amount of fluororesin impregnated is small, although the fluororesin penetrates into the interior of the fiber cloth, it often exists covering the surface of the fibers that make up the cloth without forming a continuous thin layer on the surface of the cloth.

The impregnation rate of the fluororesin into the fiber cloth is not particularly limited, but is usually about 35 to 90%. In addition, the impregnation rate is the weight of the fluororesin impregnated into the fiber cloth,
It is calculated by dividing the weight of the fiber cloth by the sum of the weight of the fluororesin impregnated into the fiber cloth.

Such a fluororesin-impregnated fiber cloth can be obtained, for example, by (a) a method in which the fiber cloth is immersed in a fluororesin dispersion, pulled up, and then heated at a temperature equal to or higher than the melting point of the fluororesin (dipping and heating are repeated if desired); (b) A method of spraying a fluororesin dispersion onto a fiber cloth and then heating it at a temperature higher than the melting point of the fluororesin (if desired, repeating the application and heating); (C) a method of spraying a fiber cloth and a fluororesin sheet; It can be obtained by a method such as stacking the sheets and then heating at a temperature higher than the melting point of the sheet.

In the method of the present invention, when a predetermined sheet of the fluororesin-impregnated cloth and a metal foil such as copper foil are overlapped and bonded together, it is important to interpose a porous fluororesin sheet between the two. By interposing the quality sheet, the adhesive force between the fluororesin-impregnated cloth and the metal foil can be improved.

The reason why adhesion is improved by the inclusion of a porous fluoropolymer sheet is not necessarily clear, but porous fluoropolymer sheets are more flexible than conventionally used non-porous fluoropolymer sheets, so they can be bonded to metal by applying pressure. It is inferred that the main reason is that the foil closely follows and adheres to the minute irregularities on the surface of the foil, resulting in an increase in the substantial contact area (i.e., adhesive area) between the porous fluororesin sheet and the metal foil.

This porous fluororesin sheet is made of the same material as the fluororesin that is impregnated into the fiber cloth, such as PTFE or FEP.
, PFA, ETFE, PCTFE, etc., and the thickness, porosity and pore size are usually about 1
0-500 μm, about 20-95% and about 0.01-1
00 μm.

In the present invention, a fluororesin-impregnated fiber cloth and a metal foil are overlapped with each other via a porous fluororesin sheet, heated and pressurized, the porous fluororesin sheet is melted, and this is used as an adhesive between the fiber cloth and the metal foil. It connects the Therefore, the heating temperature is set to be higher than the melting point of the porous fluororesin sheet. Further, the pressure and heating and pressing time may vary depending on the material of the sheet. For example, when using a porous IPTFE sheet, the temperature is about 350 to 400°C, the pressure is about 10 to
Preferably, the weight is 80 kg/cTA and the heating and pressurizing time is approximately 30 to 120 minutes.

In the laminate thus obtained, the original porous structure of the porous fluororesin sheet has disappeared, and the sheet has a substantially non-porous (solid) structure.

In the present invention, a non-porous fluororesin sheet can be interposed between the porous fluororesin sheet and the fluororesin-impregnated fiber cloth, if desired, and when a plurality of fluororesin-impregnated fiber cloths are used, the fiber In order to improve the adhesive strength between the cloths, a porous fluororesin sheet and/or a non-porous fluororesin sheet may be interposed between the fiber cloths.

The present invention further provides a method for manufacturing a circuit board by patterning the metal foil in the laminate.

Patterning of the metal foil can be carried out in the same manner as in the conventional manufacture of printed circuit boards, using a peel-and-develop photoresist, a solvent- or alkali-develop photoresist.

For example, an alkali-developable photoresist layer is formed on the surface of the metal foil of a laminate, then exposed to light through a photomask in a pattern, and then the unexposed portions of the photoresist are dissolved and removed to partially remove the metal foil. By exposing the metal foil to a specific area and then etching and removing the exposed portion of the metal foil, a patterned circuit corresponding to the exposed portion of the photoresist can be formed.

Note that the exposed portion of the photoresist is removed by dissolving.

(Example) Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 Glass cloth with a thickness of about 50 μm was coated with PTFE powder at a concentration of 60
% by weight dispersion, pulled up and then heated at a temperature of 380°C for 2 minutes.

This dipping and heating were repeated four times, and the PTFE impregnation rate was 6.
A fiber cloth impregnated with 5% fluororesin is obtained.

Next, three of these fluororesin-impregnated fiber cloths are made into a set, and the three sets are overlapped. In addition, when stacking, a non-porous PTFE with a thickness of 50 μm is placed between the pairs of fiber cloths.
A sheet was inserted. Furthermore, a non-porous PTFE sheet (thickness 50 μm) and a porous P
A TFE sheet (thickness: 50 μm, porosity: 80%, average pore diameter: 1 μm) and electrolytic copper foil (thickness: 18 μm) are stacked on each other in this order.

Then, these are heated at a temperature of 385°C and a pressure of 50kg/cf.
A laminate was obtained by heating and pressurizing for 30 minutes under the conditions of 1.

The adhesive force between the copper foil and the fluororesin-impregnated fiber cloth in this laminate was 2.2 kg/cm. The adhesive strength was measured using a tensile tester at a temperature of 25° C. and a tensile speed of 50 m/min, using a 90° peeling method.

Next, both copper foils were processed into a predetermined pattern using an alkali-developed photoresist (pattern line width: 0.15 mm,
The distance between the line widths was 0.15 mm) to obtain a circuit board.

The above pattern processing was applied to 100 laminates, but the adhesive strength between the metal foil and the fluororesin-impregnated fiber cloth was strong, and there was no problem of peeling during the work.

Example 2 Example 1 except that a porous PTFE sheet (thickness 50 μm, porosity 80%, average pore diameter 1 μm) and electrolytic copper foil (thickness 18 μm) were superimposed on both outer fluororesin-impregnated fiber cloths. A laminate was obtained by working in the same manner as above.

The adhesive force between the copper foil and the fluororesin-impregnated cloth in this laminate was 2 kg/cm.

Next, a pattern was processed in the same manner as in Example 1 to obtain a circuit board.

The above pattern processing was applied to 100 laminates, and the adhesive strength between the metal foil and the fluororesin-impregnated fiber cloth was strong (and there was no inconvenience such as peeling during the work).

Comparative Example Non-porous PTFE sheet (thickness 50 μm) and electrolytic copper foil (thickness 18 μm) were placed on the fluororesin-impregnated fiber cloth on both outer sides.
A laminate was obtained in the same manner as in Example 1, except that the laminates were laminated in this order.

The adhesive force between the copper foil and the fluororesin-impregnated fiber cloth in this laminate was as small as 1 kg/cm.

Next, the metal foil of this laminate was patterned in the same manner as in Example 1.

When the above pattern was applied to 100 laminates,
In two cases, the metal foil and the fluororesin-impregnated fiber cloth peeled off, and no circuit boards were obtained.

(Effects of the Invention) The present invention is configured as described above, and when adhering the fluororesin-impregnated fiber cloth and the metal foil, the porous fluororesin sheet is placed in contact with the metal foil. High force laminates and circuit boards can be easily produced.

Claims (2)

[Claims] (1) On the surface of the fiber cloth impregnated with fluororesin,
A method for manufacturing a laminate, characterized in that metal foil is placed through a porous fluororesin sheet, and then the fiber cloth and the metal foil are bonded by the porous fluororesin sheet by heating and pressurizing them. (2) On the surface of the fiber cloth impregnated with fluororesin,
A circuit characterized in that a metal foil is placed through a porous fluororesin sheet, and then the fiber cloth and the metal foil are bonded by the porous fluororesin sheet by heating and pressurizing them, and then the metal foil is patterned. Method of manufacturing boards.