JPH04133386A - Board for printed circuit - Google Patents

Abstract

PURPOSE:To effectively increase permittivity by employing a composite dielectric in which porous inorganic dielectric particles are dispersed in resin as a dielectric material. CONSTITUTION:As porous inorganic dielectric particles, 5-100mum of mean particle size, 0.3-7.0m<2>/gr of mean specific surface area are preferable. The particles may be secondary particles formed by aggregating primary particles, and it is desirable to be formed of compound of high permittivity composition having a Perovskite type crystalline structure.

Description

[Detailed description of the invention]

[0001]

[Industrial application field]

The present invention relates to a printed circuit board. [0002]

[Conventional technology]

As we enter the advanced information age, information transmission tends to become faster and more frequent. In new media such as mobile radios such as car telephones and personal radios, satellite broadcasting, satellite communications, and CATV, devices are becoming more compact, and as a result, microwave circuit elements such as dielectric resonators are becoming more compact. There is also a strong desire for miniaturization. [0003] The size of a microwave circuit element is based on the wavelength of the electromagnetic waves used. The wavelength λ of an electromagnetic wave propagating in a dielectric material with relative permittivity εr is λ=λa, where λa is the propagation wavelength in vacuum.
/ (εr)0°5. Therefore, the larger the dielectric constant of the printed circuit board substrate used, the smaller the device will be. In addition, when the dielectric constant of the substrate is large, electromagnetic energy is concentrated within the substrate, which is advantageous because there is less leakage of electromagnetic waves. Dispersed composite dielectrics have attracted attention, and many applications have been filed (for example, Japanese Patent Publication No. 49-25159, Japanese Patent Publication No.
-18754 etc.). Printed circuit board substrates using this composite dielectric as a dielectric material are superior in terms of cost and post-processing (cutting, hole-drilling, adhesion, etc.). [0005]

[Problem to be solved by the invention]

However, printed circuit boards using composite dielectrics containing inorganic dielectric particles have a problem in that it is difficult to provide a suitably large dielectric constant commensurate with the amount of inorganic dielectric particles added. Note that the dielectric constant of the composite dielectric used in the printed circuit board is an appropriate value (for example, relative permittivity εr=10 to several tens). If the dielectric constant is too large, the required width of the circuit becomes too narrow, making processing for forming the circuit difficult. [0006] There is a limit to increasing the amount of inorganic dielectric particles added, and it is not easy to develop new compounds for inorganic dielectric particles. Said Special Publication No. 49-25159, Special Publication No. 54-18754
In the invention described in the publication, the particle size effect of the particles to be dispersed is studied. However, the inventors' research results have found that simply increasing the particle size has little effect on ensuring a high dielectric constant with the same filling amount. [0007] In view of the above circumstances, the present invention has been developed to improve the ease of manufacturing the composite dielectric when it is made into a composite. An object of the present invention is to provide a printed circuit board that is effective and has a sufficient dielectric constant. [0008]

[Means to solve the problem]

In order to solve the above problems, the printed circuit board according to the present invention uses a composite dielectric in which porous inorganic dielectric particles are dispersed in a resin as a dielectric material. These porous inorganic dielectric particles are particles that have many voids consisting of pores and cracks that open toward the surface.
The state is such that the resin can enter into this void. The state is as shown in FIG. 1, for example. In FIG. 1, the spherical part contains porous inorganic dielectric particles, and the black part contains resin. Porous inorganic dielectric particles are dispersed in a resin, and a portion of the resin enters into the voids of the particles. [0009] The porous inorganic dielectric particles have an average particle size of 5 to 100μ
m and an average specific surface area of 0°3 to 7.0 m2/gr are preferred. If the particle size exceeds 1100 At, unevenness will appear on the surface of the printed circuit board due to the particles, resulting in poor smoothness.
In addition to poor moisture resistance (water resistance) and poor dielectric loss properties, there is also a tendency for particles to break easily during manufacturing, resulting in variations in dielectric properties. When the particle size is less than 5 μm, there is a tendency that the effect of improving the dielectric constant becomes insufficient. [0010] Then, there is a tendency that the effect of improving the dielectric constant becomes insufficient. . These secondary particles have voids between the primary particles, making them porous. In this case, it is preferable that the primary particles constituting the porous particles are physically and chemically bonded (co-bonded) to each other by sintering. It is preferable that the compound be made of a compound having a high dielectric constant composition and having a structure (1). Below, the printed circuit board of the present invention will be explained in more detail. In this invention, as a composite matrix resin (
Depending on the required Q, a resin selected as appropriate is used, but for applications in the high frequency range, resins with low high frequency loss u) ((
Preferably, resins such as PP○ (polyphenylene oxide), fluororesins (for example, polyethylene resins such as Teflon (trade name of DuPont)), polycarbonate, polyethylene,
Examples include polyethylene terephthalate, polypropylene, and polystyrene. The dielectric constant εr of these resins is usually about 2.0 to 3.2. For other uses (such as polyester, which is somewhat inferior in terms of high frequency loss,
The epoxy (v) may be a resin such as PVDF (polyvinylidene fluoride), which has a large dielectric constant. [0012] Porous inorganic dielectric particles include, for example, BaTiO2
system, S r Ti ○3 system, PbTi Zr
O series, Pb(MgNb)○ series, Ba(S
nx1/2 1/2 3 2/3 1
/3 Those with trigonal crystal structure (or composite perovskite crystal structure), and other TiOZrOSn○
Inorganic compounds such as single oxides and their composite oxides 2.
2.2 etc. are specifically mentioned. The porous inorganic dielectric particles may be spherical or may have various block-like shapes, and the shape is not particularly limited. [0013] These porous inorganic dielectric particles can be produced, for example, by (1) crushing an inorganic dielectric block obtained by making the sintered density low and porous, or (2) inorganic powder inorganic powder (for example, PVA=polyvinyl alcohol aqueous solution) and sprayed in a dry atmosphere (for example, an atmosphere at a temperature of about 130°C) to obtain granules, which were then subjected to 11.
It can be obtained by firing at a temperature of about 00°C. In the latter case (2), various particle sizes can be selected as the inorganic powder, but sintering is a physical and chemical process in which the powders within each granule are physically and chemically bonded to each other in the granules obtained by spraying. Particularly when the starting material is fine particles, grain growth occurs, but this is done to the extent that the grains can easily separate from each other. The sintered particles have open pores and cracks on the surface and voids inside, making them porous. [0014] During this sintering, a sintering aid may be used as necessary. The sintering aid may be any aid as long as it is normally used when sintering such powders, but it must be defined as one that does not destroy the dielectric composition, It is preferable to use a material that provides a sufficient reinforcing effect without impairing the properties. The amount of the sintering aid used may be appropriately selected depending on the purpose and the type of sintering aid, but usually 0.1 to 5% by weight based on the inorganic dielectric particles. preferable. Any particle size 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 to ensure uniform dispersion. The sintering aid may be added at any time during the preparation stage and firing stage of the inorganic dielectric compound. For example, when the inorganic powder is dispersed in the binder, the sintering aid is simultaneously dispersed. [0015] When a sintering aid is used, it is not only easier to sinter than when it is not used, but also because the strength of the porous particles is improved, making it easier to manufacture printed circuit boards. This has an additional effect of preventing porous dielectric particles from collapsing during heating, and since sintering can be performed at a relatively low temperature, it is possible to form porous particles with a higher porosity, and the dielectric constant of the resin layer Incidental effects may occur, such as increasing the dielectric constant of the printed circuit board. [0016] Specific examples of sintering aids include the following. That is, ■Ba〇-3i○2B203, Ca OS 102
B2O3, L 12O-3i○2-B2O3, LGe
OCaO-PbO-3iO, L 120-8iO2, B
203-Bi22゛20, PbO-3i○ -BaO, Na〇-Pb
OS 102, boric acid glass such as PbO-Ge02, lead glass, bismuth glass, cadmium glass, lithium glass, etc.CuOBi OB OC
d01L l 20ゝ 2 3ゝ 2 3 - Oxides such as PbO1W○, Pb Ge OLi SiO3, and ■35311ゝ 2 fluorides such as LiF, CuF, ZnF, CaF2. [0017] When inorganic dielectric compound particles are sintered, particle growth and electrical properties of the sintered body are generally controlled by the action of additives, but in this invention, conventionally known A variety of additives can be used for similar purposes. As mentioned above, the porous inorganic dielectric particles have an average particle diameter of 5 to 100 μm and an average specific surface area of 0.3 to 7.0 m2/
gr is preferable, but when primary particles are aggregated to form secondary particles, the primary particles have a diameter of, for example, about 0.1 to 5 μm. When the particles are spheres, d (particle diameter of primary particles) ρ (true specific gravity of primary particles)
Between Sw (specific surface area of secondary particles), d=67 (ρX
This is because there is a relationship of Sw). Therefore, for example,
In the case of barium titanate, the particle size of the primary particles is 0.14~
The thickness is approximately 3.3 μm. [0018] The printed circuit board of the present invention is typically reinforced with a reinforcing material to improve mechanical strength and dimensional stability. Examples of the reinforcing material include cross-shaped reinforcing material, mat-like reinforcing material, fiber-like reinforcing material, and the like. This reinforcing material includes both inorganic materials and organic materials, such as glass materials, ceramic materials such as alumina and zirconia, and cloths, mats, and fibers made of organic materials such as polyethylene and polyamide. The cloth or mat used 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 to 30
Use fibers with a diameter of about 0 μm and a fiber diameter of about 2 to 50 μm. [0019] The printed circuit board of the present invention is manufactured, for example, as follows. Create a resin face with porous inorganic dielectric particles dispersed,
A reinforcing cloth is impregnated with this and dried. Then, multiple pieces of the cloth thus obtained are laminated (with metal foil placed on the light surface if necessary) and heated and pressed in a mold. Let it form. The thickness of the printed circuit board of this invention is usually 0.1
It is about 2 mm. Further, in the printed circuit board of the present invention, the blending ratio of matrix resin, porous inorganic dielectric particles, and reinforcing material used as necessary is usually resin: 25 to 95% (volume %), porous Inorganic dielectric particles: 5 to 75 vol%, and when a reinforcing material is used, the reinforcing material: 0 to 70 vol%. [0020] It goes without saying that the present invention is not limited to the compounds, numerical ranges, or treatment methods exemplified above. [00213

[Function] In the printed circuit board of the present invention, the inorganic dielectric particles of the composite dielectric are porous. In the case where a composite dielectric material in which porous particles are dispersed and a composite dielectric material in which non-porous particles are dispersed have the same weight ratio of particles in the composite dielectric material, both composite dielectric materials have the same weight ratio. However, in the former (composite dielectric material in which porous particles of this invention are dispersed), the porous inorganic dielectric particles are Since the particles exist in the composite dielectric in a swollen state, the apparent volume occupied by the particles in the inorganic dielectric is larger than in the latter (composite dielectric in which non-porous particles are dispersed). Since the voids in the porous inorganic dielectric particles are also considered to act as high dielectric constant regions, the dielectric constant of the composite dielectric of the present invention is effectively improved. [0022] In addition, porous inorganic dielectric particles are less likely to sink in the resin than non-porous inorganic dielectric particles of the same size, making it difficult for sedimentation separation to occur, making it easier to manufacture the substrate.
When processing circuit boards (cutting, drilling holes, etc.), they break easily compared to non-porous inorganic dielectric particles of the same particle size.
The machined surface is also good, and there is little deterioration of processing consumables. [0023]Examples Next, specific examples of the present invention will be described. Example 1 - average particle size 20 μm, average specific surface area 1.0 m2/gr (
7) Weigh both porous BaTiO3 powder 30vol 1% and PP○ resin 70vol 1%, and the volume is 1.5
By adding twice as much trichlorethylene (manufactured by Toagosei Kagaku Kogyo Co., Ltd., trichlorethylene) and stirring, PP
A varnish was obtained by completely dissolving the O resin. Next, apply this varnish to a plain-woven glass cloth (thickness: 1100 At, fiber diameter near μm, weave density: 60 vertically, 58 horizontally per 25 mm).
The material was impregnated into a 100% polyester resin and dried at 50°C. The ratio of resin and BaTi○3 powder in the obtained varnish-impregnated glass cloth was 73 wt% (about 70 vol%). Five sheets of the varnish-impregnated cloth obtained in this way were stacked, copper foil (thickness 17 μm) was arranged on the top and bottom, and the temperature was 250°C and the pressure was 33°C.
Pressure molding was performed under molding conditions of kg/Cm2 for 10 minutes to obtain a printed circuit board substrate with copper foil on both sides. [0024] Example 2 - Average particle size 15 μm, average specific surface area 1.5 m/gr
A printed circuit board was obtained in the same manner as in Example 1, except that the porous BaTio, 7Zro, and 303 powders were used. The ratio of resin and inorganic dielectric powder in the obtained varnish-impregnated glass cloth was 72 wt% (about 70 vol%). [0025] Example 3 - Average particle size 25 μm, average specific surface area 2. b m /gr
Porous B ao, s S r o, 2Ti03
A printed circuit board was obtained in the same manner as in Example 1 except that powder was used. The ratio of resin and inorganic dielectric powder in the obtained varnish-impregnated glass cloth was 72 wt% (approximately 70 wt%).
vo1%). [0026] Example 4 - Porous BaTio, 7Zr with an average particle size of 5 μm and an average specific surface area of 5.2 m2/gr. The ratio of resin and inorganic dielectric powder in the obtained varnish-impregnated glass cloth was 73% by volume (approximately 70% by volume). [0027] Example 5 - Porous B a T io, rt Z r with an average particle size of 60 μm and an average specific surface area of 1.8 m 2 /gr. The ratio of resin and inorganic dielectric powder in the obtained varnish-impregnated glass cloth was 73 wt% (about 70 vol%). [0028] Example 6 Average particle size 1100 At, average specific surface area 2.1 m2/gr
Porous BaTio, 7Zro. A printed circuit board was obtained in the same manner as in Example 1 except that 303 powder was used. The ratio of resin and inorganic dielectric powder in the obtained varnish-impregnated glass cloth was 72 wt% (about 70 vol%). [0029] Example 7 - Average particle size 20 μm, average specific surface area 0.5 m/gr
A printed circuit board was obtained in the same manner as in Example 1, except that the porous B a T io, 7Z rO, 303 powder was used. The ratio of resin and inorganic dielectric powder in the obtained varnish-impregnated glass cloth was 72wt% (approximately 70vo
1%). [00303 Example 8 - Porous BaTio, 7Zr0.303 powder with an average particle size of 23 pm and an average specific surface area of 6.8 m/gr was used.
A printed circuit board was obtained in the same manner as in Example 1. The ratio of resin and inorganic dielectric powder in the obtained varnish-impregnated glass cloth was 73 wt% (about 70 vol%). [0031] - Comparative Example 1 - Average particle size 1.0 prn, average specific surface area 1.8 m/
A printed circuit board was obtained in the same manner as in Example 1, except that gr non-porous BaTio, 7Z r O, 303 powder was used. Comparative Example 2 - A printed circuit board was prepared in the same manner as in Example 1, except that non-porous B a T 1 o, 7Zro, 303 powder with an average particle size of 20 μm and an average specific surface area of 0.2 m/gr was used. I got it. [0032] The porous inorganic dielectric particles of each example had an average particle size of 0.
．． These are secondary particles obtained by the method described above using a calcined product of inorganic powder with a size of 1 μl as a starting material. Here, the average particle size is 0
．． The calcined material of 1 μm has grown into primary particles of around 1 μm. Regarding each printed circuit board of Examples and Comparative Examples,
Dielectric properties were measured using an impedance analyzer. The results are shown in Table 1. [0033]

[Table 1] 1st year Kaihei 4-+33agb (12) [0034] As can be seen from Table 1, the printed circuit boards of Examples 1 to 8 all have a dielectric constant of about 10 or more, which is suitable for a board. At the same time, the loss (tan δ) is also within a sufficiently practical range. Comparing the relative dielectric constant values between Example and Comparative Example 1.2, the printed circuit board of this invention has
It is clearly seen that the dielectric constant has increased dramatically. [0035] Next, an example will be described in which porous inorganic dielectric particles obtained by adding a sintering aid and sintering are used. Example 9 - 500 g of BaTio, 7Zro, 303 powder with an average particle size of 0.1 μm, borosilicate glass (manufactured by Ijo Glass Co., Ltd.)2.
5 g and 50 ml of a 5 wt % polyvinyl alcohol solution were thoroughly wet-mixed in 1 liter of ion-exchanged water, and then sprayed and granulated. Next, this was heat treated at 1050° C. for 2 hours to obtain granules (secondary particles) which were porous inorganic dielectric particles consisting of a plurality of primary particles. Table 2 shows the results of measuring the particle diameter, specific surface area, and particle strength of this granule. Note that a PCT strength testing machine manufactured by Shimadzu Corporation was used for grain strength measurement. [0036] Next, this porous B a T 1 o, 7Z , r
o, 303 granules 30vo1%, PP○ resin 70v
Both were weighed so that the concentration was 1%, 1.5 times the volume of trichlorethylene was added, and the mixture was stirred to completely dissolve the PP○ resin to obtain a varnish. Then, this varnish was impregnated into a plain-woven glass cloth (thickness 1100 μm, fiber diameter near μm, weave density: 9a 60 pieces per 25 mm, 58 widths) and dried at 50°C. The ratio of resin and particulate matter in the obtained varnish-impregnated glass cloth was 73 wt% (
It was about 70vo1%). Five sheets of the varnish-impregnated cloth obtained in this way were stacked on top of each other, and copper foil (thickness: 17 μm) was placed on top and bottom.
m), temperature 250℃, pressure 33kg/Cm2
．． Pressure molding was performed under molding conditions for 10 minutes to obtain a printed circuit board substrate covered with copper foil on both sides. [0037] Acrylic Ag paste was applied and cured on the front and back surfaces of this printed circuit board to form electrodes, and the dielectric properties were measured using an impedance analyzer. Table 3 shows the results. Example 1 - A printed circuit board was obtained in the same manner as in Example 9, except that Bao, 7Sro, and 3Ti03 powders with an average particle size of 0.1 μm were used, and the dielectric properties were examined. Table 2 shows the physical properties of the granules.
The dielectric properties of the printed circuit board are shown in Table 3. In addition, the ratio of resin and particulate matter in the obtained varnish-impregnated glass cloth was 73 wt% (about 70 vol%). [0038] Example 11 - A printed circuit board was obtained in the same manner as in Example 9, except that the amount of borosilicate glass was changed to 5.0 g, and its dielectric properties were examined. Table 2 shows the physical properties of the granules, and Table 3 shows the dielectric properties of the printed circuit board. The ratio of resin and particulate matter in the obtained varnish-impregnated glass cloth was 73wt.
% (approximately 70vol%). [0039] Example 12 - Replacing borosilicate glass with bismuth borate glass,
Further, a printed circuit board was obtained in the same manner as in Example 9 except that the heat treatment temperature was 950° C., and its dielectric properties were examined. Table 2 shows the physical properties of the granules, and Table 3 shows the dielectric properties of the printed circuit board. The ratio of resin and inorganic dielectric powder in the obtained varnish-impregnated glass cloth was 7'2.
wt% (approximately 70vol%). [0040] In Examples 13, 14, and 15 and 9, three types of granules with different physical properties were obtained by changing the slurry concentration, spraying conditions, and heat treatment temperature. A printed circuit board was produced using these granules in the same manner as in Example 9, and its dielectric properties were examined. Table 2 shows the physical properties of the granules, and Table 3 shows the dielectric properties of the printed circuit board. In addition, the ratio of resin and particulate inducer in the obtained varnish-impregnated glass cloth was 73 wt%.
(approximately 70vO1%). [0041] Example 16 - In Example 9, the borosilicate glass was Curl, 7
g, and the heat treatment temperature was 1000°C.
A printed circuit board was obtained in the same manner as in Example 9, and its dielectric properties were examined. Table 2 shows the physical properties of the granules, and Table 3 shows the dielectric properties of the printed circuit board. The ratio of resin and particulate matter in the obtained varnish-impregnated glass cloth was 7.
It was 2wt% (approximately 70vol%). [0042,] Example 17 - In Example 9, borosilicate glass was LiF2.5
g, and the heat treatment temperature was 800℃.
In the same manner as in Example 9, the dielectric properties of the printed circuit board were examined. Table 2 shows the physical properties of the granules, and Table 3 shows the dielectric properties of the printed circuit board. In addition, the ratio of resin and particulate matter in the obtained varnish-impregnated glass cloth was 72
wt% (approximately 70vol%). [0043]

[Table 2] JP-A-4-+3a; (8b (1B)

[Table 3] JP-A-4-13:5a86(20) [0045] As can be seen from Table 2.3, the granules of Examples 9 to 17 all had high grain strength and sufficient tan δ. It is within the practical range. By comparing these Examples 9 to 17 with the above-mentioned Example 2, it was found that the granules used in this invention dramatically increased the granule strength without almost changing the dielectric constant and tan δ of the printed circuit board. It can be seen that this has increased significantly. [0046]

【Effect of the invention】

As can be seen from the above, in the printed circuit board according to claims 1 to 7 of the present invention, since the inorganic dielectric particles are porous, the effect of improving the dielectric constant by the particles is effectively exhibited. In addition, it is difficult to cause sedimentation and separation, and its production is easy. In addition, its processing (cutting, hole punching, etc.) is relatively easy. [0047] In the printed circuit board of claim 2, the porous inorganic dielectric particles have an average particle diameter of 5 to 100 μm and an average specific surface area of 0.
Since it is of 3 to 7.0 m2/gr, the effect of improving the dielectric constant is more significantly exhibited. In the printed circuit board according to claim 3, the porous inorganic dielectric particles are secondary particles formed by aggregation of primary particles, and since the porous particles are easy to produce, they are easy to manufacture as a result. It has become. [0048] In the printed circuit board according to the fourth aspect, since the primary particles in the porous inorganic dielectric particles are bonded to each other by sintering, the effect of improving the dielectric constant is more prominently exhibited. In the printed circuit board according to claim 5, since the strength of the porous inorganic dielectric particles is improved, particle destruction does not occur in the composite process, stable performance can be expected, and the particles can be easily manufactured. . [0049] 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 significantly exhibited. In the printed circuit board according to the seventh aspect, since it is reinforced with a reinforcing material, mechanical properties such as dimensional stability are good.

[Brief explanation of the drawing]

FIG. 1 is a scanning electron micrograph at a magnification of approximately 2500 times showing an example of the structure of porous inorganic dielectric particles in a printed circuit board according to the present invention.

【Document name】

drawing

[Figure 1]

Claims (7)

[Claims] 1. A printed circuit board in which a composite dielectric consisting of porous inorganic dielectric particles dispersed in a resin is used as a dielectric material. [Claim 2] The porous inorganic dielectric particles have an average particle size of 5 to 5.
100pm, average specific surface area 0.3-7.0m^2/gr
2. The printed circuit board according to claim 1. 3. The printed circuit board according to claim 1, wherein the porous inorganic dielectric particles are secondary particles formed by aggregation of primary particles. 4. The printed circuit board according to claim 3, wherein the secondary particles are primary particles bonded to each other by sintering. 5. The printed circuit board according to claim 4, wherein the sintering is performed by adding a sintering aid. 6. The printed circuit board according to claim 1, wherein the porous inorganic dielectric particles are made of a compound having a perovskite crystal structure. [Claim 7] Claims 1 to 6 reinforced with a reinforcing material.
The printed circuit board described in any of the above.