JP5140317B2 - Composite dielectrics and their use - Google Patents

Description

  The present invention relates to a composite dielectric having a high dielectric constant and a low dielectric loss tangent and use thereof.

  In recent years, in order to reduce the size of electronic equipment, to cope with high frequencies, and to reduce noise, a technology has been proposed in which electronic components, particularly capacitors (capacitors) are incorporated into a printed wiring board in the form of a sheet to form a multilayer board. This technology is expected to progress further in the future. Thus, the capacitor incorporated in the board is called an embedded capacitor, and various proposals and improvements have been made in recent years.

  In this way, the number of components that can be mounted on a wiring board with a built-in capacitor has increased dramatically, and since the capacitor is directly connected to the board without a lead wire, the capacitor as a conventional electronic component is connected with solder. Compared to the printed wiring board, the noise is greatly reduced. In addition, for a surface mount type wiring board in which electronic components are mounted on a substrate without lead wires, the wiring length for connecting the components is remarkably shortened by using the built-in capacitor method. Thus, in order to reduce the size of electronic devices, to cope with high frequencies, and to reduce noise, this built-in capacitor method has received much attention as an innovative technology.

  The progress of the built-in capacitor technology so far can be known from many patent documents (for example, see Patent Documents 1 to 9). For example, a green sheet containing dielectric ceramic powder such as barium titanate is formed on the substrate from the initial form in which the capacitor element is embedded in the substrate, and then fired at a high temperature of about 1000 ° C. Various forms are described, including those for forming a high dielectric element. However, according to these methods, in order to sinter the dielectric powder, it is necessary to apply a high temperature as high as 1000 ° C. to the substrate.

  On the other hand, a dielectric composite sheet in which a dielectric ceramic powder such as barium titanate or titanium oxide is dispersed in a binder polymer such as an epoxy resin or a phenol resin is sandwiched between copper foils on both sides. A method has been proposed in which an electrode is formed at a required location by performing a lithography process, and this is connected to a wiring board to form a built-in capacitor. However, in this case, the high dielectric constant of thousands of barium titanate is drastically reduced to several tens by forming a composite dielectric sheet. This is said to be because a binder polymer is interposed between the ferroelectric barium titanate powders, and a continuous sintered dielectric film is not formed at about the molding temperature of the resin.

  As described above, when the composite dielectric is used, the dielectric constant is lower than that of the high dielectric ceramics. However, in the multilayer wiring board, the noise reduction effect by the composite dielectric placed under the IC element is still clear. Is recognized. Thus, a composite dielectric sheet type capacitor that is easy in mass production process is a useful means for achieving a noise reduction effect even if it has a problem that the dielectric constant is low. Various proposals and improvements have been made to increase the dielectric constant as much as possible.

As already known (see Non-Patent Document 1), the dielectric constant of the composite dielectric is ε, the dielectric constant of the binder polymer is ε ₁ , and the dielectric of the filler (dielectric ceramic powder) If the rate is ε ₂ and the filling factor of the filler is f,
log ε = (1-f) log ε ₁ + f log ε ₂ … (1)
It is represented by

  Therefore, the higher the dielectric constant of the binder polymer, the higher the dielectric constant of the filler, and the higher the filling rate of the filler, the higher the dielectric constant of the resulting composite dielectric. That is, if the filler used has the same dielectric constant as the filling factor, the higher the dielectric constant of the binder polymer used, the higher the dielectric constant of the resulting composite dielectric. If the dielectric constant of the composite dielectric can be increased, the capacitance of the capacitor can be increased. As a result, the electrode area can be reduced, and thus the device can be reduced in size and density. Can contribute to noise reduction.

  In addition, in order to reduce the transmission loss of a signal transmitted through the wiring board, it is very practically important that the built-in capacitor has a low dielectric loss tangent (hereinafter referred to as tan δ). There has also been proposed an attempt to solve the problem by using it as a polymer (see Patent Document 9).

As described above, it is important to use a high dielectric polymer having a small tan δ as a binder in order to obtain a high dielectric composite. However, a high dielectric polymer often has a high tan δ and has conventionally been a dielectric. No binder polymer with a good balance between rate and tanδ is known. For example, cyanoethyl pullulan, which is well-known as a high dielectric polymer and has been studied in organic EL, has a very high dielectric constant but also a large tan δ. Therefore, in practice, it cannot be used for the production of composite dielectrics. .
JP-A-5-218615 JP-A-8-181453 Japanese Patent No. 3062413 Japanese Patent No. 3323083 Japanese Patent No. 3199664 Japanese Patent No. 3487728 Japanese Patent No. 3398351 Japanese Patent No. 3510227 JP 2005-29700 A '96 Conf. Of the IEEE Int. Symp. On Elect. Insul., “Effect of Fillers on the Dielectric Properties of Polymers”

  Accordingly, an object of the present invention is to provide a composite dielectric filled with a dielectric ceramic powder, in which tan δ is kept low while increasing the dielectric constant, and use thereof.

  According to the invention, the general formula (I)

(In the formula, m and n respectively represent the molar fractions of the quinonediimine structural unit and the phenylenediamine structural unit in the repeating unit, and 0 ≦ m ≦ 1, 0 ≦ n ≦ 1, and m + n = 1.)
There is provided a composite dielectric obtained by dispersing a dielectric ceramic powder in polyaniline having a repeating unit. In particular, according to the present invention, a composite dielectric sheet comprising the above composite dielectric is provided.

Further, according to the present invention, there is provided a capacitor having a conductive base material disposed on both sides of the composite dielectric sheet and a wiring board having the capacitor in the substrate.
The present invention also provides a composite dielectric slurry obtained by dispersing a dielectric ceramic powder in a polyaniline solution having the above general formula as a repeating unit.

  According to the present invention, a polydiline represented by the above general formula is used as a binder polymer, and a dielectric ceramic powder is dispersed therein, thereby obtaining a composite dielectric having a low dielectric constant and a low tan δ. it can.

  The polyaniline used as the binder polymer in the present invention has a general formula

(In the formula, m and n respectively represent the molar fractions of the quinonediimine structural unit and the phenylenediamine structural unit in the repeating unit, and 0 ≦ m ≦ 1, 0 ≦ n ≦ 1, and m + n = 1.)
As a repeating unit.

  For such a polyaniline, a polymer doped with a protonic acid is first obtained by the method described in JP-A-03-28229, and this is neutralized with a basic substance, that is, dedoped. Can be obtained as a polymer soluble in an organic solvent. The polyaniline soluble in the organic solvent thus obtained usually has an intrinsic viscosity [η] of 0.40 dl / g or more as measured in N-methyl-2-pyrrolidone at 30 ° C.

  Compared with many hitherto known polymers, the polyaniline has a low tan δ despite its high dielectric constant. That is, according to the measurement by the present inventors at 1 MHz, the polyaniline has a dielectric constant of 4.9 and tan δ of 0.030. On the other hand, polyimide (Rika Coat SN-20 manufactured by Shin Nippon Rika Co., Ltd.) has a dielectric constant of 3.9 and tan δ of 0.024, and polyamideimide (Bilomax HR11NN manufactured by Toyobo Co., Ltd.) is It has a dielectric constant of 4.3 and tan δ of 0.058. Polyamide (Conex, manufactured by Teijin Techno Products Co., Ltd.) has a dielectric constant of 5.2 and tan δ of 0.072. The aforementioned cyanoethyl pullulan has a dielectric constant of 15.4, but tan δ also has a high value of 0.182.

The dielectric ceramic powder used in the present invention is preferably barium, lead, lithium, potassium, sodium, titanium, niobium, tantalum, zirconium, magnesium, calcium, strontium, aluminum, silicon, zinc, bismuth, tin, neodymium, samarium. An oxide powder of at least one element selected from lanthanum and manganese. Specific examples include, for example, BaTiO ₃ (barium titanate), PbTiO ₃ , LiNbO ₃ , KNbO ₃ , LiTaO ₃ , Ba ₂ NaNb ₅ O ₁₅ , NaNO ₂ , PbZrO ₃ —PbTiO ₃ -based solid solution, SiO ₂ , Al _2. Examples thereof include O ₃ , TiO ₂ , 3Al ₂ O ₃ .2SiO ₂ (mullite), CaTiO ₃ , SrTiO ₃ (strontium titanate), PbZrO ₃ , NaNbO ₃ , LaAlO ₃ , and LaMnO ₃ .

  Of these, barium titanate and strontium titanate can be preferably used in the present invention because of their high dielectric constant. Further, barium titanate nanoparticles described in JP-A-2004-339040 can also be suitably used.

  As described above, the composite dielectric has a higher dielectric constant when the filling factor of the dielectric ceramic powder is increased, and a lower dielectric constant when the filling factor is lowered. Therefore, the filling rate of the dielectric ceramic powder is appropriately selected according to the target dielectric constant value of the obtained composite sheet. In the present invention, the filling rate of the dielectric ceramic powder is usually The range is 1 to 90% by volume, preferably 20 to 80% by volume, and most preferably 30 to 70% by volume.

  In the composite dielectric according to the present invention, for example, the polyaniline represented by the above general formula is dissolved in an appropriate organic solvent as a binder polymer to form a solution, and the dielectric ceramic powder as described above is dispersed in the solution to obtain a uniform dielectric. A composite dielectric slurry is prepared, and the composite dielectric slurry is applied onto an appropriate substrate, and then the solvent is evaporated and removed in a dryer to obtain a sheet, that is, a composite dielectric sheet. Can do.

  The organic solvent used for the preparation of the composite dielectric slurry is not particularly limited as long as the polyaniline is dissolved. For example, N-methyl-2-pyrrolidone is preferably used.

  In order to disperse the dielectric ceramic powder in the binder polymer solution, for example, a suitable dispersing means such as a disperser type stirring device, a ball mill, a planetary rotary pot mill, a bead mill, a wet jet mill can be used. It is not limited.

  The composite dielectric sheet according to the present invention can be advantageously used for a capacitor or a wiring board having a capacitor in a substrate. The capacitor may be prepared, for example, by applying the slurry on an appropriate conductive substrate and then evaporating the solvent of the slurry in a dryer to produce a sheet on the conductive substrate. Thereafter, hot pressing may be performed as necessary. In order to apply the slurry to the conductive substrate, for example, the slurry is usually cast on the substrate, and then formed into a sheet with a predetermined thickness using an applicator, a wire bar, a doctor blade, or the like. is there.

  As another method for producing a capacitor, for example, the slurry is applied on a glass plate and dried to produce a composite dielectric sheet, which is then peeled off from the glass plate, and electrodes are produced on both sides by vapor deposition. May be. However, the method for manufacturing the capacitor is not limited to the above example.

  As described above, when the slurry is applied on an appropriate conductive substrate and then dried in a dryer, the temperature depends on the type of solvent and binder polymer used, but usually the boiling point of the solvent. Below, it is preferable to set it as the temperature below the melting point of a binder polymer. First, a composite sheet having a uniform surface can be obtained by heating and drying at a relatively low temperature, and then drying by increasing the temperature stepwise. For example, when the above-mentioned N-methyl-2-pyrrolidone solution of polyaniline is used as the binder polymer, the drying conditions can be, for example, about 1 hour at a temperature in the range of 80 to 140 ° C.

  EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

Example 1
(Production of doped polyaniline by oxidative polymerization of aniline)
First, polyaniline doped with protonic acid was prepared according to the method described in JP-A-03-28229. In a 10 L separable flask equipped with a stirrer, a thermometer, and a straight tube adapter, 6000 g of distilled water, 360 mL of 36% hydrochloric acid and 400 g (4.295 mol) of aniline were charged in this order to dissolve aniline. Separately, while cooling with ice water, 434 g (4.295 mol) of 97% concentrated sulfuric acid was added to 1493 g of distilled water in a beaker and mixed to prepare an aqueous sulfuric acid solution. This sulfuric acid aqueous solution was added into the separable flask, and the whole flask was cooled to −4 ° C. in a low-temperature thermostat.

  Next, 980 g (4.295 mol) of ammonium peroxodisulfate was added to 2293 g of distilled water in a beaker and dissolved to prepare an aqueous oxidizing agent solution.

  While cooling the whole flask in a low-temperature thermostatic bath, while maintaining the temperature of the reaction mixture at −3 ° C. or lower, 1 mL of the above ammonium peroxodisulfate aqueous solution from a straight tube adapter using a tubing pump to an acidic aqueous solution of aniline salt with stirring The solution was gradually added dropwise at a rate of not more than / min. Initially, the colorless and transparent solution changed from greenish blue to blackish green as the polymerization of aniline progressed, and then a blackish green powder precipitated. After 7 hours were required and the dropping of the aqueous ammonium peroxodisulfate solution was completed, the stirring was continued at a temperature of −3 ° C. or lower for an additional hour.

  The polyaniline powder thus obtained was filtered, washed with water, washed with acetone, and vacuum dried at room temperature to obtain 430 g of conductive polyaniline doped with sulfuric acid as a black-green powder. This conductive polyaniline powder was press-molded into a disk having a diameter of 13 mm and a thickness of 700 μm, and its conductivity was measured by the Juan del Po method. As a result, it was 14 S / cm.

(De-doping of conductive polyaniline with ammonia)
350 g of the doped conductive polyaniline powder was added to 4 L of 2N aqueous ammonia and stirred for 5 hours. The mixture changed from black-green to blue-violet. The powder was separated by filtration using a bruna funnel, washed repeatedly in distilled water until the filtrate became neutral while stirring in a beaker, and then washed with acetone until the filtrate became colorless. Thereafter, the powder was vacuum-dried at room temperature for 10 hours to obtain 280 g of black-brown dedope polyaniline powder.

  This polyaniline was soluble in N-methyl-2-pyrrolidone, and the solubility was 8 g (7.4%) with respect to 100 g of the same solvent. The intrinsic viscosity [η] measured at 30 ° C. as an N-methyl-2-pyrrolidone solvent was 1.23 dL / g.

  Next, as a result of GPC measurement of the polyaniline soluble in the dedoped N-methyl-2-pyrrolidone, the number average molecular weight was 2300 and the weight average molecular weight was 160000 (both in terms of polystyrene).

  The polyaniline powder thus obtained had a true density of 1.24, measured using acetone as an immersion liquid and a pycnometer with a thermometer of 50 mL. As the dielectric ceramic powder, barium titanate (BT-03 manufactured by Sakai Chemical Industry Co., Ltd.) was prepared, and the true density measured with a pycnometer using water as an immersion liquid was the same as the above polyaniline. It was 5.95.

  A composite dielectric sheet was produced as follows by setting the barium titanate filling rate to 40% by volume. That is, 26.55 g of N-methyl-2-pyrrolidone was charged in a polypropylene beaker having a capacity of 100 mL, and the polyaniline was first added and dissolved little by little while stirring at about 700 rpm using a high-speed stirrer with a disper blade. However, the rotation speed of the stirrer was increased little by little, and finally the stirring was continued at about 2000 rpm for 15 minutes to completely dissolve 3.45 g of polyaniline, and N-methyl-2-pyrrolidone of black-blue polyaniline A solution was obtained.

  After confirming that no particulate matter adhered to the inner wall surface of the beaker, when the barium titanate was added little by little to the polyaniline solution, the slurry changed from black blue to blue. When the total amount of 11.03 g of barium titanate had been added, the resulting slurry was a blue viscous slurry.

  The resulting slurry was transferred to a vacuum bell jar and slowly degassed while degassing with a vacuum pump. Six sheets of polyimide adhesive tape with a thickness of 60 μm are laminated on both sides of the glass plate to make a guide, and the defoamed slurry is cast on the glass plate between the guides, and the slurry is put in a glass tube having a diameter of 8 mm. Got it. Thus, the glass plate which apply | coated the slurry is heat-dried at 80 degreeC for 1 hour and 140 degreeC for 1 hour in a dryer, and after that, a glass plate is immersed in ion-exchange water, and the obtained sheet | seat is glass I peeled it off the board. The composite dielectric sheet thus obtained had a brown color.

  Gold was vapor-deposited on both surfaces of this composite dielectric sheet using a vacuum vapor deposition apparatus to prepare a sample. The dielectric constant and tan δ of this sample were measured by changing the frequency using an impedance analyzer (Agilent 4194A). The results are shown in Figure 1. The dielectric constant at 1 MHz was 53 and tan δ was 0.03.

Comparative Example 1
Instead of the polyaniline solution in N-methyl-2-pyrrolidone, 25.2 g of the N-methyl-2-pyrrolidone solution of the polyamideimide (Vilomax R11NN manufactured by Toyobo Co., Ltd.) having a concentration of 15% by weight was used. A composite sheet was prepared in the same manner as in Example 1, and the dielectric constant and tan δ were measured in the same manner. The dielectric constant at 1 MHz was 30, and tan δ was 0.06.

4 is a graph showing frequency characteristics of dielectric constant of composite sheets having a barium titanate filling rate of 40% by volume obtained in Example 1 and Comparative Example 1. 4 is a graph showing frequency characteristics of tan δ of composite sheets having a barium titanate filling rate of 40% by volume obtained in Example 1 and Comparative Example 1.

Claims (10)

Formula (I)

(In the formula, m and n respectively represent the molar fractions of the quinonediimine structural unit and the phenylenediamine structural unit in the repeating unit, and 0 ≦ m ≦ 1, 0 ≦ n ≦ 1, and m + n = 1.)
A composite dielectric obtained by dispersing a dielectric ceramic powder in polyaniline having a repeating unit.   At least the dielectric ceramic powder is selected from barium, lead, lithium, potassium, sodium, titanium, niobium, tantalum, zirconium, magnesium, calcium, strontium, aluminum, silicon, zinc, bismuth, tin, neodymium, samarium, lanthanum and manganese The composite dielectric according to claim 1, which is a powder of an oxide of one kind of element.   The composite dielectric according to claim 1 or 2, wherein a filling rate of the dielectric ceramic powder is in a range of 1 to 90% by volume. The composite dielectric according to claim 1, wherein the dielectric ceramic powder is barium titanate or strontium titanate. Composite dielectric sheet comprising the composite dielectric according to any one of claims 1 to 4. A capacitor comprising a conductive base material disposed on both sides of the composite dielectric sheet according to claim 5 . A wiring board having the capacitor according to claim 6 in a substrate. Formula (I)

(In the formula, m and n respectively represent the molar fractions of the quinonediimine structural unit and the phenylenediamine structural unit in the repeating unit, and 0 ≦ m ≦ 1, 0 ≦ n ≦ 1, and m + n = 1.)
A composite dielectric slurry in which a dielectric ceramic powder is dispersed in a polyaniline solution containing as a repeating unit. A method for producing a composite dielectric, comprising: casting the composite dielectric slurry according to claim 8 on a substrate, and then removing the solvent in the slurry. Formula (I)

(In the formula, m and n respectively represent the molar fractions of the quinonediimine structural unit and the phenylenediamine structural unit in the repeating unit, and 0 ≦ m ≦ 1, 0 ≦ n ≦ 1, and m + n = 1.)
A method for producing a composite dielectric slurry, comprising dispersing a dielectric ceramic powder in a polyaniline solution having a repeating unit as a repeating unit.

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