JP2740357B2 - Printed circuit board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed circuit board.

[0002]

2. Description of the Related Art In an advanced information age, information transmission tends to be faster and higher in frequency. In mobile media such as mobile phones and personal radios, and in new media such as satellite broadcasting, satellite communications, and CATV, devices are being reduced in size, and microwave circuit elements such as dielectric resonators are being developed along with this. In addition, miniaturization is strongly desired.

The size of the microwave circuit element is based on the wavelength of the electromagnetic wave used. The wavelength λ of an electromagnetic wave propagating in a dielectric having a relative permittivity εr is λ = λa / (εr) ^0.5 , where λa is the propagation wavelength in vacuum. Therefore, the device becomes smaller as the permittivity of the printed circuit board used increases. In addition, when the dielectric constant of the substrate is large, electromagnetic energy is concentrated in the substrate, so that leakage of electromagnetic waves is small, which is convenient.

[0004] From the standpoint of improving the dielectric constant, a composite dielectric in which inorganic dielectric particles are dispersed in a resin has attracted attention.
Many applications have been filed (for example, Japanese Patent Publication No. 49-25159,
54-18754). A printed circuit board substrate using this composite dielectric as a dielectric material is also excellent in terms of cost, post-processing (cutting, drilling, bonding, etc.).

[0005]

However, a printed circuit board using the composite dielectric containing the inorganic dielectric particles has a moderately large dielectric constant corresponding to the added amount of the inorganic dielectric particles. The problem is that you can't do that. The dielectric constant of the composite dielectric used for the printed circuit board has an appropriate magnitude (for example, the relative dielectric constant ε).
r = 10 to several tens). If the dielectric constant is too large, the required width of the circuit becomes too narrow, and processing for forming the circuit becomes difficult.

There is a limit to increasing the amount of inorganic dielectric particles to be added, and it is not easy to develop a new compound for inorganic dielectric particles. In the inventions described in JP-B-49-25159 and JP-B-54-18754, the particle size effect of the dispersed particles is studied. However, the research results of the inventors have found that simply increasing the particle size is less effective in ensuring a high dielectric constant with the same filling amount.

If the particle size of the inorganic dielectric particles is large, sedimentation and separation are likely to occur. Therefore, the dielectric constant can be improved and the composite dielectric containing the inorganic dielectric particles can be easily formed at the same time as compounding. This is a problem that needs to be solved in a printed circuit board. In view of such circumstances, an object of the present invention is to provide a printed circuit board having a sufficient dielectric constant, in which inorganic dielectric particles having a high dielectric constant effectively exhibit a dielectric constant increasing effect.

[0008]

In order to solve the above problems, in a printed circuit board according to the present invention, a composite dielectric in which porous inorganic dielectric particles are dispersed in a resin is used as a dielectric material. I have to. These porous inorganic dielectric particles are particles having a large number of voids formed of holes, cracks, and the like that open toward the surface, and are in such a state that the resin can enter the voids.
The state is as shown in FIG. 1, for example. In FIG. 1, a spherical one represents porous inorganic dielectric particles, and a black background part represents resin. Porous inorganic dielectric particles are dispersed in the resin, and a part of the resin enters the voids of the particles.

The porous inorganic dielectric particles have an average particle size of 5 to 100 μm and an average specific surface area of 0.3 to 7.0 m ² / g.
r is preferred. If the particle size exceeds 100 μm, irregularities due to particles appear on the surface of the printed circuit board, resulting in poor smoothness, poor moisture resistance (water resistance) and poor dielectric loss characteristics, and also during manufacturing. There is a tendency that the particles are easily broken and the dielectric properties vary.
When the particle size is less than 5 μm, the effect of improving the dielectric constant tends to be insufficient.

When the specific surface area exceeds 7.0 m ² / gr,
There is a tendency that moisture resistance (water resistance) becomes inferior and dielectric loss characteristics deteriorate. When the specific surface area is less than 0.3 m ² / gr, the effect of improving the dielectric constant tends to be insufficient. The porous inorganic dielectric particles may be secondary particles formed by aggregation of primary particles. The secondary particles are porous due to voids between the primary particles. in this case,
The primary particles constituting the porous particles are preferably physically and chemically bonded to each other by sintering.

The porous inorganic dielectric particles are preferably made of a compound having a high dielectric constant composition having a perovskite crystal structure. Hereinafter, the printed circuit board of the present invention will be described more specifically. In the present invention, as the composite matrix resin, a resin appropriately selected as necessary is used. For applications in a high frequency range, a resin having a low high frequency loss (low tan δ) is preferable. Polyphenylene oxide) resin, fluororesin (for example, polyfluoroethylene resin such as Teflon (trade name of DuPont)), polycarbonate, polyethylene, polyethylene terephthalate, polypropylene, and polystyrene. The relative permittivity εr of these resins is usually about 2.0 to 3.2. For other applications, polyester, epoxy, or PV with a large dielectric constant is slightly inferior in terms of high-frequency loss.
A resin such as DF (polyvinylidene fluoride) may be used.

As the porous inorganic dielectric particles, for example,
BaTiO ₃ system, SrTiO ₃ system, PbTi _1/2 Zr
_1/2 O ₃ system, Pb (Mg _2/3 Nb _1/3 ) O ₃ system, Ba
_{(Sn x Mg y Ta z)} O 3 system, Ba (Zr _x Zn _y T
a _z ) O ₃ -based or other perovskite-type crystal structures (or composite perovskite-type crystal structures), and inorganic compounds such as TiO ₂ , ZrO ₂ , and SnO ₂ alone and composite oxides thereof. No. The porous inorganic dielectric particles may have a shape or a block-like shape of various shapes, and the shape is not particularly limited.

The porous inorganic dielectric particles include, for example,
The inorganic dielectric block obtained by making the sintered density low and porous may be crushed, or the inorganic powder may be ground with a binder (for example, PVA = polyvinyl alcohol aqueous solution).
It can be obtained by, for example, dispersing and spraying in a dry atmosphere (for example, a temperature atmosphere of about 130 ° C.) to obtain a granular material, and firing it at a temperature of about 1100 ° C. In the latter case, various particle sizes can be selected as the inorganic powder, but in the case of sintering, in the granular material obtained by spraying, the powder in each granular material is physically and chemically Bonding occurs, especially when the starting material is fine particles, but grain growth occurs,
The process is performed to such an extent that the granular materials are easily separated from each other. The sintered particles are porous, having pores or cracks opened on the surface and voids formed inside.

At the time of sintering, a sintering aid may be used if necessary. As the sintering aid, any auxiliaries usually used when sintering such powders may be used, but if defined strictly, they do not destroy the dielectric composition, It is preferable to use a material which does not impair the characteristics and gives a sufficient reinforcing effect. The amount of the sintering aid used may be appropriately selected depending on the purpose and the type of the sintering aid, but is usually 0.1 to 5% by weight based on the inorganic dielectric particles. preferable. Any particle diameter of the sintering aid can be used as long as it is in the range of 0.01 to 100 μm, but it is preferably about 0.1 to 50 μm for uniform dispersion. The sintering aid may be added at any time during the preparation and firing steps of the inorganic dielectric compound. For example, when the inorganic powder is dispersed in the binder, the sintering aid is dispersed at the same time.

The use of a sintering aid not only has the effect of facilitating sintering, but also improves the strength of the porous particles as compared with the case where no sintering aid is used. The collateral effect of preventing the collapse of the porous dielectric particles at the time and the sintering at a relatively low temperature make it possible to form porous particles having a higher porosity and reduce the dielectric constant of the resin layer. Increasing the size may have additional effects such as an improvement in the dielectric constant of the printed circuit board.

The following are specific examples of the sintering aid. _{That, BaO-SiO 2 -B 2 O} 3, CaO
—SiO ₂ —B ₂ O ₃ , Li ₂ O—SiO ₂ —B ₂ O
_{3, Li 2 O-Al 2} O 3 -SiO 2, Na 2 O-Al
₂ O ₃ —SiO ₂ , Li ₂ O—GeO ₂ , CdO—Pb
_{O-SiO 2, Li 2 O} -SiO 2, B 2 O 3 -Bi 2
O ₃ , PbO—SiO ₂ —BaO, Na ₂ O—PbO—
Borate glass such as SiO ₂ , PbO—GeO ₂ , lead glass, bismuth glass, cadmium glass, lithium glass, CuO, Bi ₂ O ₃ , B ₂ O ₃ ,
CdO, Li ₂ O, PbO, WO ₃ , Pb ₅ Ge ₃
Oxides such as O ₁₁ and Li ₂ SiO ₃ and LiF;
It is a fluoride such as CuF ₂ , ZnF ₂ or CaF ₂ .

When sintering the inorganic dielectric compound particles,
Generally, particle growth and control of electrical properties of a sintered body are performed by the action of additives. In the present invention, however, various conventionally known additives may be used for the same purpose. it can. As porous inorganic dielectric particles,
As described above, those having an average particle size of 5 to 100 μm and an average specific surface area of 0.3 to 7.0 m ² / gr are preferable. However, when the primary particles are aggregated into secondary particles, The particle size is, for example, about 0.1 to 5 μm.
This is, when the particles are spherical, d (particle size of primary particles),
ρ (true specific gravity of primary particles), Sw (specific surface area of secondary particles)
This is because d 6 / (ρ × Sw). Therefore, for example, in the case of barium titanate, the particle size of the primary particles is about 0.14 to 3.3 μm.

The printed circuit board of the present invention is usually
Reinforced with reinforcing material to improve mechanical strength and dimensional stability.
Examples of the reinforcing material include a cloth-like reinforcing material, a mat-like reinforcing material, and a fiber-like reinforcing material. The reinforcing material includes an inorganic material and an organic material, and examples thereof include a glass material, a ceramic material such as alumina and zirconia, and a cloth, mat, and fiber made of an organic material such as polyethylene and polyamide. The cloth or mat usually has a thickness of about 15 μm to 1.5 mm and a fiber diameter of about 0.5 to 20 μm. Fibers are typically 20-300 lengths
Use a fiber having a diameter of about μm and a fiber diameter of about 2 to 50 μm.

The printed circuit board of the present invention is manufactured, for example, as follows. A resin varnish in which porous inorganic dielectric particles are dispersed is made, impregnated with a reinforcing cloth, dried, and then a plurality of the cloths thus obtained are laminated (if necessary, a metal foil is formed). (Disposed on the surface) and then heat and press mold with a mold. The thickness of the printed circuit board of the present invention is usually 0.1 to 2 mm.
It is about. The mixing ratio of the matrix resin, the porous inorganic dielectric particles, and the reinforcing material used as needed in the printed circuit board of the present invention is usually the following:
25 to 95 vol% (vol%), porous inorganic dielectric particles:
5 to 75 vol%, and when a reinforcing material is used, the reinforcing material:
It is in the range of 0-70 vol%.

It goes without saying that the present invention is not limited to the compounds exemplified above, the numerical ranges or the processing methods.

[0021]

In the printed circuit board according to the present invention, the inorganic dielectric particles of the composite dielectric are porous. If the composite dielectric in which the porous particles are dispersed and the composite dielectric in which the non-porous particles are dispersed have the same weight ratio of the particles in the composite dielectric, the two composite dielectrics In the above, both the porous particles and the non-porous particles have the same true volume ratio, but in the former (the composite dielectric in which the porous particles of the present invention are dispersed), the porous inorganic dielectric particles are Since the particles are swollen and exist in the composite dielectric, the apparent volume of the particles occupying the inorganic dielectric is larger than that of the latter (a composite dielectric in which non-porous particles are dispersed). And since it is considered that the void portion of the porous inorganic dielectric particles also acts as a high dielectric constant region,
In the composite dielectric of the present invention, the dielectric constant is effectively improved.

Further, the porous inorganic dielectric particles are less likely to sink in the resin and cause less sedimentation than non-porous inorganic dielectric particles of the same size, thereby facilitating the production of the substrate. Furthermore, in the case of processing (cutting, opening a hole, etc.) a circuit board, the substrate is easily broken as compared with the non-porous inorganic dielectric particles having the same particle size, so that the processed surface is good and the deterioration of processing consumables is small. .

[0023]

EXAMPLES Next, specific examples of the present invention will be described. Example 1 30 vol% of porous BaTiO ₃ particles having an average particle diameter of 20 μm and an average specific surface area of 1.0 m ² / gr, and 70 vol of PPO resin
%, And 1.5 parts by volume of tricrene (manufactured by Toa Gosei Chemical Industry Co., Ltd., trichloroethylene) is added, and the mixture is stirred to completely dissolve the PPO resin and remove the varnish. Obtained. Then, this varnish was applied to a plain woven glass cloth (thickness: 100 μm, fiber diameter: 7 μm).
m, woven density: 60 lines in length and 58 lines in width per 25 mm) and dried at 50 ° C. The ratio of resin and BaTiO ₃ particles in the obtained varnish-impregnated glass cloth is 7
It was 3% by weight (about 70% by volume). Five varnish-impregnated cloths thus obtained were stacked, and copper foil (thickness: 17 μm) was disposed on the upper and lower sides, at a temperature of 250 ° C. and a pressure of 33 kg / cm.
^2. Press-molding was performed under molding conditions for 10 minutes to obtain a double-sided copper foil-clad printed circuit board substrate.

Example 2 A printed circuit board was manufactured in the same manner as in Example 1 except that porous BaTi _0.7 Zr _0.3 O ₃ particles having an average particle size of 15 μm and an average specific surface area of 1.5 m ² / gr were used. A substrate was obtained. The proportion of the resin and the porous inorganic dielectric particles in the obtained varnish-impregnated glass cloth was 72 wt% (about 70 vol%).

Example 3 A printed circuit board was prepared in the same manner as in Example 1 except that porous Ba _0.8 Sr _0.2 TiO ₃ particles having an average particle size of 25 μm and an average specific surface area of 2.5 m ² / gr were used. A substrate was obtained. The proportion of the resin and the porous inorganic dielectric particles in the obtained varnish-impregnated glass cloth was 72 wt% (about 70 vol%).

Example 4 A printed circuit board was manufactured in the same manner as in Example 1 except that porous BaTi _0.7 Zr _0.3 O ₃ particles having an average particle size of 5 μm and an average specific surface area of 5.2 m ² / gr were used. A substrate was obtained. The proportion of the resin and the porous inorganic dielectric particles in the obtained varnish-impregnated glass cloth was 73 wt% (about 70 vol%).

Example 5 A printed circuit board was prepared in the same manner as in Example 1 except that porous BaTi _0.7 Zr _0.3 O ₃ particles having an average particle size of 60 μm and an average specific surface area of 1.8 m ² / gr were used. A substrate was obtained. The proportion of the resin and the porous inorganic dielectric particles in the obtained varnish-impregnated glass cloth was 73 wt% (about 70 vol%).

Example 6 A printed circuit board was manufactured in the same manner as in Example 1 except that porous BaTi _0.7 Zr _0.3 O ₃ particles having an average particle diameter of 100 μm and an average specific surface area of 2.1 m ² / gr were used. A substrate was obtained. The proportion of the resin and the porous inorganic dielectric particles in the obtained varnish-impregnated glass cloth was 72 wt% (about 70 vol%).

Example 7 A printed circuit board was manufactured in the same manner as in Example 1 except that porous BaTi _0.7 Zr _0.3 O ₃ particles having an average particle size of 20 μm and an average specific surface area of 0.5 m ² / gr were used. A substrate was obtained. The proportion of the resin and the porous inorganic dielectric particles in the obtained varnish-impregnated glass cloth was 72 wt% (about 70 vol%).

Example 8 A printed circuit board was manufactured in the same manner as in Example 1 except that porous BaTi _0.7 Zr _0.3 O ₃ particles having an average particle size of 23 μm and an average specific surface area of 6.8 m ² / gr were used. A substrate was obtained. The proportion of the resin and the porous inorganic dielectric particles in the obtained varnish-impregnated glass cloth was 73 wt% (about 70 vol%).

Comparative Example 1 A non-porous BaTi _0.7 Zr _0.3 O ₃ powder having an average particle size of 1.0 μm and an average specific surface area of 1.8 m ² / gr was used.
A printed circuit board was obtained in the same manner as in Example 1. The proportion of the resin and the non-porous inorganic dielectric powder in the obtained varnish-impregnated glass cloth was 73 wt% (about 70 v
ol%). Comparative Example 2 A printed circuit board was prepared in the same manner as in Example 1 except that non-porous BaTi _0.7 Zr _0.3 O ₃ particles having an average particle diameter of 20 μm and an average specific surface area of 0.2 m ² / gr were used. Obtained. The proportion of the resin and the non-porous inorganic dielectric particles in the obtained varnish-impregnated glass cloth was 73 wt% (about 70 vol.
%)Met.

The porous inorganic dielectric particles in each of the examples are secondary particles obtained by the above-described method using a calcined inorganic powder having an average particle size of 0.1 μm as a starting material. Here, the calcined raw material having an average particle size of 0.1 μm has grown into primary particles of about 1 μm. Dielectric characteristics of each printed circuit board of the example and the comparative example were measured using an impedance analyzer. Table 1 shows the results.

[0033]

[Table 1]

As can be seen from Table 1, all of the printed circuit boards of Examples 1 to 8 are suitable for use as substrates.
It has a relative dielectric constant of 0 or more and a loss (tan δ) within a range that can be sufficiently used. Comparing the values of the relative permittivity between the embodiment and the comparative examples 1 and 2, it can be clearly seen that the permittivity of the printed circuit board of the present invention is dramatically increased.

Next, an example of using porous inorganic dielectric particles obtained by adding a sintering aid and sintering will be described. Example 9 BaTi _0.7 Zr _0.3 O ₃ powder 5 having an average particle size of 0.1 μm
00g, borosilicate glass (Iwaki Glass Co., Ltd.) 2.5g
And 50 ml of a 5 wt% polyvinyl alcohol solution were thoroughly wet-mixed in 1 liter of ion-exchanged water, followed by spray granulation. Next, this was heat-treated at 1050 ° C. for 2 hours to obtain a granular material (secondary particle) as a porous inorganic dielectric particle composed of a plurality of primary particles. Table 2 shows the measurement results of the particle diameter, specific surface area and particle strength of the porous inorganic dielectric particles. The particle strength was measured using a PCT strength tester manufactured by Shimadzu Corporation.

Next, the porous BaTi _0.7 Zr _0.3 O
_{The three} particles were weighed so as to be 30 vol% and the PPO resin 70 vol%, and 1.5 times by volume of trichlene was added and stirred to completely dissolve the PPO resin to obtain a varnish. Was. Then, the varnish was applied to a plain woven glass cloth (thickness: 100 μm, fiber diameter: 7 μm, woven density: 2).
(60 lines vertically and 58 lines horizontally per 5 mm) and dried at 50 ° C. The proportion of the resin and the porous inorganic dielectric particles in the obtained varnish-impregnated glass cloth is 73% by weight (about 7%).
0 vol%). Five varnish-impregnated cloths thus obtained were stacked, copper foil (thickness: 17 μm) was placed on the upper and lower sides, and pressure molding was performed at a temperature of 250 ° C., a pressure of 33 kg / cm ² , and molding conditions for 10 minutes. A substrate for a double-sided copper foil-clad printed circuit board was obtained.

Table 3 shows the results of measuring the dielectric properties of this printed circuit board using an impedance analyzer. -. Except for using BaTi _{0 7} Zr _0.3 O ₃ powder of Example 10 the average particle diameter 0.1μm, the same procedure as in Example 9, to obtain a substrate for a printed circuit was examined dielectric properties. Table 2 shows the physical properties of the porous inorganic dielectric particles, and Table 3 shows the dielectric properties of the printed circuit board. The ratio of resin and porous inorganic dielectric particles in the obtained varnish-impregnated glass cloth was 73 wt.
% (About 70 vol%).

Example 11 A printed circuit board was obtained in the same manner as in Example 9 except that the amount of the borosilicate glass was changed to 5.0 g, and the dielectric properties were examined. The physical properties of the porous inorganic dielectric particles are shown in Table 2,
Table 3 shows the dielectric properties of the printed circuit board. The proportion of the resin and the porous inorganic dielectric particles in the obtained varnish-impregnated glass cloth was 73 wt% (about 70 vol%).
Met.

Example 12 A borosilicate glass was replaced with a bismuth borate glass.
Further, a printed circuit board was obtained and the dielectric characteristics were examined in the same manner as in Example 9 except that the heat treatment temperature was changed to 950 ° C. Table 2 shows the physical properties of the porous inorganic dielectric particles, and Table 3 shows the dielectric properties of the printed circuit board. The proportion of the resin and the porous inorganic dielectric particles in the obtained varnish-impregnated glass cloth was 72 wt% (about 70 vol%).

Examples 13, 14, and 15 In Example 9, three kinds of porous inorganic dielectric particles having different physical properties were obtained by changing the slurry concentration, spraying conditions and heat treatment temperature. Using these porous inorganic dielectric particles, a printed circuit board was prepared in the same manner as in Example 9, and the dielectric characteristics were examined. Table 2 shows the physical properties of the porous inorganic dielectric particles, and Table 3 shows the dielectric properties of the printed circuit board. The ratio of the resin and the porous inorganic dielectric particles in the obtained varnish-impregnated glass cloth was 73 wt% (about 70 vol%).

Example 16 In Example 9, the borosilicate glass was changed to CuO1.7.
g, and the heat treatment temperature was 1000 ° C.
In the same manner as in Example 9, a printed circuit board was obtained, and its dielectric properties were examined. Table 2 shows the physical properties of the porous inorganic dielectric particles, and Table 3 shows the dielectric properties of the printed circuit board. The proportion of the resin and the porous inorganic dielectric particles in the obtained varnish-impregnated glass cloth was 72 wt% (about 70 v
ol%).

Example 17 In Example 9, the borosilicate glass was changed to LiF2.5.
g, and except that the heat treatment temperature was 800 ° C.
In the same manner as in Example 9, a printed circuit board was obtained, and its dielectric properties were examined. Table 2 shows the physical properties of the porous inorganic dielectric particles, and Table 3 shows the dielectric properties of the printed circuit board. The proportion of the resin and the porous inorganic dielectric particles in the obtained varnish-impregnated glass cloth was 72 wt% (about 70 v
ol%).

[0043]

[Table 2]

[0044]

[Table 3]

As can be seen from Tables 2 and 3, Examples 9 to 17 were used.
All of the circuit substrates described above exhibit a sufficiently large relative permittivity, and tan δ is within a sufficiently practical range. By comparing these Examples 9 to 17 with Example 2 described above, the particles (porous inorganic dielectric particles) used in the present invention almost change the relative dielectric constant and tan δ of the printed circuit board. It can be seen that the grain strength was dramatically increased without any problem.

[0046]

As can be seen from the above description, the printed circuit board according to claims 1 to 7 of the present invention is:
Since the inorganic dielectric particles are porous, the effect of improving the dielectric constant by the particles is effectively exhibited, and furthermore, the sedimentation separation phenomenon hardly occurs, and the production thereof is easy. Further, the processing (cutting, opening of holes, etc.) is relatively easy.

In the printed circuit board according to the second aspect, since the porous inorganic dielectric particles have an average particle size of 5 to 100 μm and an average specific surface area of 0.3 to 7.0 m ² / gr, the dielectric constant is high. The improvement effect is more remarkably exhibited. In the printed circuit board according to the third aspect, the porous inorganic dielectric particles are secondary particles obtained by assembling the primary particles, and the porous particles are easily manufactured, and as a result, the porous inorganic dielectric particles are easily manufactured. Has become.

In the printed circuit board according to the fourth aspect, since the primary particles of the porous inorganic dielectric particles are bonded to each other by sintering, the effect of improving the dielectric constant is more remarkably exhibited. In the printed circuit board according to claim 5,
Since the strength of the porous inorganic dielectric particles is improved, the particles are not broken in the compounding step, stable performance can be expected, and the particles can be easily manufactured.

In the printed circuit board according to the sixth aspect, since the porous inorganic dielectric particles are made of a compound having a perovskite crystal structure, the effect of improving the dielectric constant is more remarkably exhibited. In the printed circuit board according to the seventh aspect, since it is reinforced by the reinforcing material, mechanical properties such as dimensional stability are good.

[Brief description of the drawings]

FIG. 1 is a magnification of about 2 showing an example of the structure of a porous inorganic dielectric particle in a printed circuit board according to the present invention.
It is a scanning electron microscope photograph of 500 times.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kiyotaka Furumori 1048 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Works, Ltd. References JP-A-63-173633 (JP, A) JP-A-62-68853 (JP, A)

Claims (6)

(57) [Claims] A composite dielectric comprising porous inorganic dielectric particles having an average particle diameter of 5 to 100 μm and an average specific surface area of 0.3 to 7.0 m ² / gr dispersed in a resin is used as a dielectric material. Printed circuit boards. 2. The printed circuit board according to claim 1, wherein the porous inorganic dielectric particles are secondary particles obtained by assembling primary particles. 3. The printed circuit board according to claim 2, wherein the secondary particles are formed by bonding primary particles to each other by sintering. 4. The printed circuit board according to claim 3, wherein the sintering is performed by adding a sintering aid. 5. The printed circuit board according to claim 1, wherein the porous inorganic dielectric particles are made of a compound having a perovskite crystal structure. 6. The method according to claim 1, which is reinforced with a reinforcing material.
The printed circuit board according to any one of the above.