JPH03273695A - Multilayer printed-wiring board - Google Patents

Abstract

PURPOSE:To enable a low permittivity to be maintained using fluorine plastic layer and obtain a multilayer printed-wiring board with further reduced dimensions change rate by allowing the fluorine plastic layer as an adhesive for joining a resin-impregnated fiber material and a metal layer or an inner layer material and the metal layer to be reinforced by a fiber base. CONSTITUTION:Metal layers 4 and 6 are joined in one place by an inner layer material which is obtained by joining metal layers 4 and 6 through low melt- point fluorine plastic layers 3 and 5 reinforced by a fiber base on both surfaces of a polytetrafluoroethylene impregnated fiber material 1 or on both surfaces of two or more fiber materials 1 which are joined by the polytetrafluoroethylene layer. Concrete examples of the polytetrafluoroethylene(PTEE) impregnated fiber material 1 to be used are inorganic fiber including glass one, woven cloth and nonwoven cloth of organic fiber including aromatic polyimide one and fiber material including paper which are impregnated with PTFE.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a multilayer printed wiring board having a novel structure.

(Prior art) Multilayer printed wiring boards are made by laminating a predetermined number of base materials made of glass cloth impregnated with epoxy resin or polyimide, bonding metal foil to both sides to form an inner layer material, and adhering to both sides of this inner layer material. A structure in which metal foils are bonded using an agent is known.

However, this multilayer printed wiring board has a high dielectric constant of approximately 4.0 or more due to the use of epoxy resin or polyimide, and is therefore unsuitable for computers and the like that require high-speed calculation performance.

For this reason, it has been proposed to use a fluororesin as a resin to impregnate the glass cloth and to use a fluororesin as an adhesive between the base material and the metal foil, and between the inner layer material and the metal foil (
(Japanese Patent Application Laid-Open No. 64-51937).

By using such a fluororesin, it is possible to achieve a low dielectric constant of a multilayer printed wiring board, and furthermore, the rate of dimensional change of the resulting printed wiring board can be reduced.

(Problem to be solved by the invention) In recent years, demands for improved performance on printed wiring boards have been severe. For example, increasing wiring density (packing density) in order to miniaturize equipment is one of them. There is a need to further reduce the dimensional change rate of wiring boards.

Therefore, an object of the present invention is to provide a multilayer printed wiring board that maintains a low dielectric constant by using a fluororesin and further reduces the rate of dimensional change.

(Means for Solving the Problems) As a result of various studies, the present inventor found that by reinforcing the fluororesin layer, which serves as an adhesive for bonding the resin-impregnated fiber material and the metal layer or the inner layer material and the metal layer, with a fiber base material. Although the reason for this is not necessarily clear, they have found that the intended purpose can be achieved, and have completed the present invention.

That is, the multilayer printed wiring board according to the present invention can be used on both sides of a polytetrafluoroethylene-impregnated fiber material or on two sides of the fiber material.
An inner layer material is formed by bonding two or more sheets with a polytetrafluoroethylene layer, and a metal layer is bonded to both sides of the material through a low melting point fluororesin layer reinforced with a fiber base material, and a fiber base material is attached to both sides of this inner layer material. The metal layer is bonded and integrated with a low melting point fluororesin layer reinforced with.

Specific examples of the polytetrafluoroethylene (PTFE)-impregnated fiber materials used in the present invention include inorganic fibers such as glass fibers, asbestos fibers, alumina fibers, boron fibers, silicon carbide fibers, titania fibers, and boron nitride fibers; PT is applied to fibrous materials such as woven fabrics, non-woven fabrics, and paper made of organic fibers such as aromatic polyamide fibers.
Examples include those impregnated with FE.

When the amount of PTFE impregnated into the fibrous material is large, the PTFE penetrates into the inside of the fibrous material and forms a thin layer on the surface of the fibrous material, and furthermore, when the fibrous material has a network, this mesh may be occluded. On the other hand, when the amount of fluororesin impregnated is small, P
Although TFE penetrates into the interior of the fibrous material, it often exists covering the surface of the fibers forming the fibrous material without forming a continuous thin layer on the surface of the fibrous material.

The PTFEO impregnation rate with respect to the fiber material is not particularly limited, but is usually about 50 to 70%. The impregnation rate is determined by dividing the weight of PTFE impregnated into the fibrous material by the weight of the fibrous material and multiplying it by 100.

Such a PTFE-impregnated fibrous material can be obtained by, for example, (a) dipping the fibrous material in PTFE dispersion, pulling it up, and then heating it at a temperature equal to or higher than the melting point of PTFH (dipping and heating are repeated if desired); (b) ) PTF in fiber material
Spray application of E-disversion, then PTFH
It can be obtained by a method of heating at a temperature above the melting point of (c) a method of laminating a fibrous material and a PTFE sheet and then heating it to a temperature above the melting point of the sheet, etc. can.

In the present invention, a low melting point fluororesin layer reinforced with a fiber base material is provided on both sides of one sheet of this PTFE-impregnated fiber material or on both sides of a predetermined sheet of the impregnated fiber material bonded and integrated via a PTFE layer. the metal layer as an adhesive (
metals or alloys such as copper, aluminum, stainless steel, etc.)
The material bonded with these is used as the inner layer material. In order to bond the PTFE-impregnated fiber materials to each other, the fiber materials are stacked one on top of the other, and the PTFE layer they have on the surface is used as an adhesive to bond them, a PTFE sheet is interposed between the fiber materials, A method of joining using this sheet as an adhesive can be adopted.

In addition, as the low melting point fluororesin layer used as an adhesive to bond the PTFE-impregnated fiber material and the metal layer, PTF
Fluororesins other than E, such as tetrafluoroethylene-
Hexafluoropropylene copolymer (FEP), ethylene-tetrafluoroethylene copolymer (ETFE)
, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), and polychlorotrifluoroethylene (CTFE).

In the present invention, it is important to use the low melting point fluororesin layer reinforced with a fiber base material in order to achieve the objective of reducing the dimensional change rate of the multilayer printed wiring board. As this fiber base material, woven fabric, nonwoven fabric, or paper made of organic fibers or inorganic fibers similar to those used for the above-mentioned PTFE-impregnated fiber material can be used. The low melting point fluororesin layer reinforced with such a fiber base material can be obtained in the same manner as the PTFE-impregnated fiber material described above.

Note that the metal layer in the inner layer material is used as a predetermined pattern. Patterning of the metal layer can be carried out in the same manner as in conventional printed circuit board manufacturing using a peel-and-develop photoresist, a solvent-developable photoresist, or an alkali-developable photoresist.

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

The multilayer printed wiring board of the present invention has metal layers integrally bonded to both surfaces of such an inner layer material via a low melting point fluororesin layer reinforced with a fiber base material.

This joining can be carried out by a heating and pressing method, at a temperature higher than the melting point of the low melting point fluororesin as the adhesive, and at a pressure of about 15 to 50 kg/c1j.

Next, the present invention will be explained in detail with reference to the drawings. FIG. 2 shows examples of inner layer materials used in the present invention, and 1.1 is a PTFE-impregnated fiber material obtained by impregnating a fibrous material with a thickness of about 50 to 800 μm with PTFE. Joined using heat and pressure method. Then, a metal layer 4.4 with a thickness of about 10 to 100 μm is adhered to each of these surfaces by a low melting point fluororesin layer 3.3 with a thickness of about 50 to 800 μm reinforced with a fiber base material (not shown). has been done.

In order to obtain a multilayer printed wiring board using this inner layer material, for example, the metal layer 4.4 is patterned as shown in FIG. The metal layer 6.6 is joined by the reinforced low melting point fluororesin layer 5.5.

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

Example I A. Production of inner layer material A glass cloth with a thickness of 50 μm is immersed in a dispersion containing 60% by weight of PTFE powder, 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 5% PTFE impregnated fiber material is obtained.

Next, three sets of the three PTFE-impregnated fiber materials are stacked one on top of the other. In addition, when stacking the sets, a PTFE sheet with a thickness of 60 μm was interposed between the sets.

Separately, a 70-μm-thick glass cloth-reinforced FEP sheet was prepared by dipping a 60-μm-thick glass cloth in dispersion with an FEP powder concentration of 60% by weight, pulling it up, and then heating it at 300°C for 2 minutes. get.

Then, a glass cloth reinforced FEP sheet and copper foil (thickness 70 μm) were arranged on both sides of the above stacked body, and the temperature was 385° C. and the pressure was 50 kg/cti (7).
By heating and pressurizing for a minute, an inner layer material having the same structure as that shown in FIG. 2 is obtained.

B. Manufacture of multilayer printed wiring board The copper foil on both sides of the inner layer material is patterned using an alkali-developable photoresist.

Next, glass cloth reinforcement F was placed on the patterned copper foil of the inner layer material.
EP sheets (the same ones used for manufacturing the inner layer material) and copper foil (thickness 18 μm) were stacked on top of each other and heated to a temperature of 300 µm.
By heating and pressurizing for 10 minutes at a temperature of 10 kg/cd, a multilayer printed wiring board having the same structure as that shown in FIG. 1 was obtained.

The dimensional change rate of this multilayer printed wiring board was 0.03%.

In addition, the dimensional change rate is determined by etching the copper foil on both sides of the inner layer material so that two circles with a diameter of 10 μm remain (distance A between the circles), and then adding a glass cloth reinforcing sheet and copper foil (thickness: 18 μm) on top of this. were stacked on top of each other and heated and pressed for 10 minutes at a temperature of 300°C and a pressure of 10kg/c4, and then the copper foil on the glass cloth reinforcing sheet was etched away.
Next, the distance (B) between the circles of the copper foil remaining on the surface of the inner layer material was measured and calculated using the following formula.

Comparative Example When manufacturing inner layer materials and multilayer printed wiring boards,
Instead of FEP sheet reinforced with glass cloth, thickness 70
A multilayer printed wiring board was obtained in the same manner as in the example except that a μm PTFE sheet was used and the temperature during production of the multilayer printed wiring board was 385°C.

The dimensional change rate of this multilayer printed wiring board was 0.05%.

(Effects of the Invention) The present invention is configured as described above, and by reinforcing the low melting point fluororesin layer as an adhesive with a fiber base material,
It has the characteristics that a multilayer printed wiring board with a low dielectric constant and a small rate of dimensional change can be obtained.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an example of a multilayer printed wiring board according to the present invention, and FIG. 2 is a sectional view showing an example of an inner layer material used in the invention. 1...PTFE-impregnated fiber material 3.5...Low melting point fluororesin layer 4.6...Metal layer

Claims (1)

[Claims] A metal layer is bonded to both sides of a polytetrafluoroethylene-impregnated fiber material or to both sides of two or more sheets of the impregnated fiber material joined by a polytetrafluoroethylene layer via a low-melting point fluororesin layer reinforced by a fiber base material. This multilayer printed wiring board is made by integrally bonding an inner layer material and a metal layer on both sides of the inner layer material with a low melting point fluororesin layer reinforced with a fiber base material.