JP3010840B2 - Mixed nonwoven fabric for low dielectric constant printed circuit boards - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mixed nonwoven fabric comprising a fiber reinforcing material and polyetheretherketone (hereinafter referred to as "PEEK") short fibers, and more particularly to a mixed nonwoven fabric suitable for a printed circuit board having a low dielectric constant.

[0002]

2. Description of the Related Art As is well known, dielectric properties have recently come to the fore as quality characteristics required for printed circuit boards. As the operation speed of a computer increases, the transmission speed of a signal increases, so that a printed circuit board having high reliability and a low dielectric constant has been required even under high-speed operation. In response to such demands, thermoplastic resins having a low dielectric constant such as polytetrafluoroethylene resin, polysulfone, polyethylene, and polybutadiene have been studied on the resin side, and polytetrafluoroethylene fiber woven fabric or aromatic resin on the substrate side. A polyamide fiber woven fabric, a quartz fiber woven fabric and the like are being studied. However, these conventional printed circuit boards have problems in molding workability, reliability as a printed circuit board, and cost, and have not been able to sufficiently meet the demands.

[0003]

With the increase in the speed of information processing, delays in signal propagation speed, disturbances in signal waveforms, and the like have been regarded as problems, and printed wiring boards using low dielectric constant materials have been required. It has come to be. However, the development of the base material required for this has been delayed, and sufficient measures have not been taken. SUMMARY OF THE INVENTION It is an object of the present invention to provide a low-cost substrate for a printed circuit board, which is more versatile and can be used for a printed circuit board requiring low dielectric constant characteristics, as a high-speed arithmetic printed circuit board for information processing.

[0004]

Means for Solving the Problems The present inventors have made a non-woven fabric comprising a continuous fiber reinforcing material and short fibers containing PEEK short fibers, wherein the reinforcing materials are arranged in one direction, and the fibers in the non-woven fabric are arranged in one direction. It has been found that the contact between them can be solved by a mixed nonwoven bonded by a binder.
The continuous fiber reinforcing material used in the mixed nonwoven fabric of the present invention is a glass fiber or an alumina fiber having a fiber diameter of 5 to 5.
It is used in the form of a strand obtained by bundling 200 to 1000 30 μm fibers. The continuous fiber reinforcement is held in the nonwoven fabric in a state where a large number of continuous fiber reinforcements are aligned in parallel. The aligned continuous fiber reinforcement layer may be a single layer or a plurality of layers in the nonwoven fabric.

[0005] As short fibers constituting the nonwoven fabric of the present invention, PEEK fibers are mainly used. Further, other thermoplastic resin fibers may be used, or a mixture of PEEK fibers and other thermoplastic resin fibers may be used. Although the fiber diameter and length of the PEEK short fiber are not particularly limited, the fiber diameter is 20 to 50 μm.
m and a length of about 5 to 20 mm are preferable. PEE
When short K fibers and other thermoplastic resin short fibers are molded using a mixed nonwoven fabric, they are melted to become a matrix resin of a molded product. Short fibers for reinforcement, for example, glass fibers used as a continuous fiber reinforcement, may be mixed with the PEEK short fibers. E glass fiber, D glass fiber, S glass fiber and the like can be used as the glass fiber used for the continuous fiber reinforcing material and the short fiber, but from the point of the present invention, D glass fiber having a small dielectric constant is most suitable. In any case, the ratio of the reinforcing fiber is 30 to 65 vol%.
%, Preferably 45 to 60%. Within this range, the appearance of the molded product is good and the strength is high.

[0006] The mixed nonwoven fabric of the present invention is obtained as follows. The PEEK long fiber having a fiber diameter of 20 to 50 μm is used as a short fiber (chopped strand) having an appropriate length. At this time, the length of the short fiber is preferably 5 to 20 mm. The reason is that the dispersibility when short fibers are dispersed in water is good as described later. Next, this P
EEK staple fiber is put into water, and it is opened and dispersed in a filament while stirring. Here, it is preferable to use an appropriate dispersant in order to disperse the short fibers well in water and to keep the dispersed state. As the dispersant, a surfactant-based dispersant which is generally commercially available, for example, Marpomerse PT or Sondes KV (both from Matsumoto Yushi Kogyo Co., Ltd.)
And its concentration is suitably from 0.1 to 0.3%. The dispersion concentration of PEEK is 0.02 to 0.2
%, Preferably 0.05 to 0.1%. When it is desired to mix short fibers other than PEEK short fibers into the short fibers constituting the nonwoven fabric, the short fibers are also introduced into water and dispersed.

[0007] Next, the PEEK staple fibers in this dispersion are deposited on a drainage substrate using a papermaking technique to form fiber mats. This process can be performed by either a batch system or a continuous system. The batch system using a paper machine shown in FIG. 1 will be described as an example. A paper machine generally designated by reference numeral 1 comprises a paper machine main body 3 adapted to accommodate a dispersion 2, a bottom 5 holding the paper machine main body 3 rotatably by a hinge 4, and a paper machine main body 3. A fixing member 6 fixed to the bottom 5,
It has a drainage substrate 7 attached to the upper surface of the bottom 5 and a drain pipe 8 and a valve 9 connected to the lower end of the bottom 5. The dispersion is charged into the paper machine 1 and PEEK
With the short fibers uniformly dispersed in water, the valve 9 is opened to drain the liquid. As a result, the water contained in the dispersion liquid 2 passes through the drainage substrate 7 and is discharged from the drainage pipe 8, and the PEEK short fibers are captured on the drainage substrate 7. Thus, when the water in the dispersion liquid 2 charged into the paper machine 1 has almost completely passed through the filterable base material 7, a fiber mat composed of PEEK short fibers is uniformly formed on the filterable base material. Here, as the drainage base material 7 to be used, it is preferable to use a net having many small meshes. Although the net varies depending on the length and the fiber diameter of the PEEK short fiber used, the size of the mesh is 0.26 to 0.2 mm for a fiber diameter of 20 to 50 μm and a fiber length of 5 to 20 mm.
It is suitable that the aperture ratio is about 30 mm and the aperture ratio is about 50 to 60%. If the mesh is too large, the speed of the liquid passing through the net increases, and the speed of forming the fiber mat increases.However, the amount of short fibers passing through the mesh increases, and the yield decreases. The resulting fiber mat becomes uneven. On the other hand, if the mesh is too small, the net tends to be clogged, and it takes time to form the fiber mat. Furthermore, when short fibers having different specific gravities are mixed and dispersed in the dispersion, if the formation of the fiber mat takes a long time, the short fibers having a large specific gravity increase in the lower layer of the dispersion, and the fibers to be formed are formed. Among the mats, the proportion of short fibers having a large specific gravity in the lower layer of the fiber mat increases. Therefore, the size of the mesh is selected so that these disadvantages do not occur.

After the fiber mat is formed on the drainage substrate 7 as described above, a continuous fiber such as a large number of glass fiber strands is placed on the aluminum frame 10 on the fiber mat as shown in FIG. The reinforcing materials 11 are arranged in one direction, and the reinforcing material 11 is placed thereon, and the short fiber dispersion is put into the paper machine 1 again. At this time, it is necessary to pay attention such as gently feeding the fiber mat along the wall of the paper machine 1 so that the previously formed fiber mat is not broken by the re-feeding of the dispersion liquid. After charging the dispersion, the valve 9 is opened again to drain the liquid. As a result, a fiber mat is formed in which the continuous fiber reinforcement arranged in one direction on the drainage base material is sandwiched between upper and lower PEEK short fibers. The weight per unit area of the laminated sheet thus formed is 50 to 50% after drying.
It is possible in the range of 500 g / m ² . The aluminum frame 1
It is preferable that the continuous fiber reinforcing material 11 set to 0 has low Tex or is sufficiently opened. After forming a fiber mat in which a continuous fiber reinforcement is sandwiched on the drainage base material 7, the paper machine body 3 is rotated about the hinge 4 in the direction of the arrow,
The fiber mat is taken out together with the drainage substrate 7. Then, excess moisture is removed from the fiber mat, and the binder is sprayed uniformly when the fiber mat contains some water. The binder used here is preferably an aqueous binder because it has better permeability to a fiber mat containing some water. Thereafter, the fiber mat is dried to remove water, and a nonwoven fabric in which PEEK short fibers and a unidirectionally arranged continuous fiber reinforcing material are mixed is obtained. As described above, the method of producing the mixed nonwoven fabric according to the present invention is described by using a batch method. However, it is also possible to employ a continuous method by utilizing the equipment of a paper machine.

It is necessary that the fiber reinforcing material used in the present invention has a surface coated with a sizing agent having compatibility or affinity with the thermoplastic resin to be the matrix resin after molding. As the sizing agent, in the case of glass fiber, a material obtained by modifying an epoxy resin as a film forming component by addition of an amine or ethylene oxide is suitable, and a material provided with a silane coupling agent, a lubricant, and a softener is used. The silane coupling zy is appropriately selected from epoxy silane, amino silane, methacryl silane, vinyl silane, cationic silane, chlorosilane and the like. Further, it is required that the binder used in the nonwoven fabric of the present invention has compatibility or affinity with the matrix resin and does not adversely affect various characteristics of the printed circuit board as a final product. There is no particular limitation as long as it satisfies the above conditions, but those obtained by adding epoxy or amine oxide to water-soluble epoxy resin satisfy this condition.

[0010]

The PEE is obtained by laminating a plurality of the mixed nonwoven fabrics of the present invention, further laminating copper foils on both sides thereof, and hot pressing.
The K fibers are melted to become a matrix resin, and a printed board having a continuous fiber reinforcing material layer arranged in one direction can be obtained. The printed circuit board obtained in this manner can reduce the dielectric constant of the entire substrate by using PEEK resin having a small dielectric constant as a matrix and using D glass fiber having a small dielectric constant as a fiber reinforcing material. The printed circuit board has a continuous fiber reinforcing material layer arranged in one direction.
Since it is controlled in the range of 65%, it is unlikely that the reinforcing material layer is washed away or distorted. By arranging short fibers of the reinforcing material on both sides of the continuous fiber reinforcing material layer, the deformation of the continuous fiber reinforcing material can be further suppressed. By shifting the direction of the continuous fiber reinforcement arranged in one direction in the direction perpendicular to each layer when laminating the mixed nonwoven fabric,
The arrangement direction of the continuous fiber reinforcing materials in the molded substrate can be arranged in the longitudinal direction and the lateral direction of the substrate, and the directionality of the mechanical properties of the substrate can be reduced. Further, since PEEK having excellent heat resistance is used as the matrix resin, a printed circuit board having good heat resistance can be obtained. Further, when short fibers of the reinforcing material are arranged on both sides of the continuous fiber reinforcing material layer, the short fibers form a layer in a filament state, so that the surface smoothness of the molded substrate can be improved.

The production of a printed circuit board is generally carried out by impregnating a woven fabric of reinforcing fibers with a resin varnish such as an epoxy resin or a polyimide resin to form a prepreg, laminating the prepreg, and heating and pressing the prepreg. If a mixed nonwoven fabric is used, the weaving step of the woven fabric is not required, the prepreg step is not required, and the time of the heating press can be shortened because it is not a curing reaction. In short, a printed circuit board having substantially the same performance as a conventional printed circuit board and also having low dielectric constant characteristics can be easily obtained in a form in which steps are omitted.

[0012]

EXAMPLE A P having a filament diameter of 30 μm and a fiber length of 6 mm was used.
The EEK staple fiber was dissolved in water in which 0.1% of a dispersant Marpomerse PT (manufactured by Matsumoto Yushi Kogyo Co., Ltd.) was dissolved.
2.2 g of short fiber is charged to prepare a dispersion of about 0.1%, and this dispersion is charged to the paper machine 1 shown in FIG. The drainage substrate 7 of the paper machine 1 is a 65 mesh stainless steel net having an opening of 0.28 mm and an opening ratio of 51.
%, A size of 22 cm × 22 cm was used. The valve 9 was opened, the water passing through the drainage substrate 7 was drained through a drain pipe, and PEEK staple fibers were deposited on the drainage substrate 7 to form a fiber mat. Next, as shown in FIG.
A set of 528 glass fiber strands (D-Glass: manufactured by Nippon Electric Glass Co., Ltd.) over a width of 22 cm was prepared, placed on the fiber mat previously made, and then carefully again PEEK. A dispersion containing 2.2 g of short fibers was charged, and PEEK short fibers were deposited as in the previous case. Thus, a sandwich-like one-way reinforcing fiber mat in which the continuous fiber reinforcing material was set with PEEK short fibers from the upper and lower surfaces was obtained. After forming the fiber mat, an epoxy resin (Epicoat 828: manufactured by Shell Chemical Co., Ltd.)
An aqueous solution containing 1% of an epoxy resin made water-soluble by adding 1 mol of diethanolamine to the water-soluble epoxy resin as an active ingredient was used as a binder to uniformly spray and dry the fiber mat. Three mixed nonwoven fabrics obtained by the above method were laminated and heated and pressed under the following conditions to obtain a laminated plate. Temperature 390 ° C Pressure 10 kg / cm ² Time 10 minutes

[0013]

Comparative Example 18.4 Tex glass fiber yarn (D-glass fiber: manufactured by Nippon Electric Glass Co., Ltd.) weaving density Warp direction 6
A woven fabric woven at 0/25 mm and 58/25 mm in the weft direction is applied to a polyimide varnish obtained by mixing a polyimide resin (Kelimide # 601: manufactured by Nippon Polyimide Co., Ltd.) and a reagent N-methyl-2-pyrrolidone at 50:50. Impregnated to make prepreg. Five prepregs are laminated,
Heat and pressure were applied to obtain a laminate.

The dielectric constants of the laminates obtained in Examples and Comparative Examples were measured. Table 1 shows the measurement results.

[Table 1] Laminate thickness Dielectric constant (1 MHz) Example 0.48 mm 3.26 Comparative Example 0.51 mm 4.04

[0015]

The printed circuit board obtained by laminating the mixed nonwoven fabric of the present invention using D-glass fiber as a fiber reinforcing material, and applying heat and pressure to the laminate is made of D-glass, which has been conventionally used as a low dielectric constant substrate. The dielectric constant can be further reduced as compared with a polyimide-based printed circuit board. Also, PEEK
High heat resistance because the resin is a matrix resin,
Further, there is an advantage that a weaving step and a prepreg step are not required in the process, and a low dielectric constant printed board can be easily and inexpensively obtained.

[Brief description of the drawings]

FIG. 1 shows an apparatus 1 for producing the mixed nonwoven fabric of the present invention.
Schematic sectional view showing an example.

FIG. 2 is a perspective view showing a state in which a continuous fiber reinforcing material to be put in a fiber mat is set in an aluminum frame.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Paper machine 2 Dispersion liquid 3 Paper machine main body 4 Hinge 5 Bottom part 6 Fixing member 7 Filtration base material 8 Drainage pipe 9 Valve 10 Aluminum frame 11 Continuous fiber reinforcement

Claims (1)

(57) [Claims] 1. A nonwoven fabric comprising a continuous fiber reinforcing material and short fibers including polyetheretherketone short fibers, wherein the continuous fiber reinforcing material is arranged in one direction, and a contact point between fibers in the nonwoven fabric is: A mixed nonwoven fabric for a low-permittivity printed circuit board, which is bonded with a binder.