JP4428963B2 - Electromagnetic wave absorber and high frequency circuit package using the same - Google Patents

Description

  The present invention relates to an electromagnetic wave absorber and a high frequency circuit package using the same.

  Usually, in a high frequency circuit package, airtight sealing is performed by attaching a rectangular parallelepiped package lid made of metal or ceramics to a package base.

  Accordingly, since a rectangular parallelepiped cavity is formed inside the high frequency circuit package, the high frequency circuit package has the same properties as the rectangular cavity resonator.

Therefore, at a higher frequency band than the cutoff frequency determined by the size of the air-dong, since they produce a cavity resonance, when mounting a high-frequency semiconductor element or other circuit elements that operate in this frequency band on the package for high frequency circuit, an empty dong by reducing the size, the cutoff frequency element are sufficiently higher than the frequency band to operate.

  However, this method has a problem that the frequency at which cavity resonance occurs is lower than the frequency band in which the element operates as the operating frequency of the element increases.

  In recent years, in order to solve this problem, a method of suppressing cavity resonance by mounting an electromagnetic wave absorber inside a high frequency circuit package and absorbing electric field energy or magnetic field energy at the time of cavity resonance has been adopted. It has become to.

For example, as an electromagnetic wave absorber used in the high frequency circuit package, an electromagnetic wave absorber 72 made of a ferrite sheet having a rectangular parallelepiped shape on the back surface of the package lid 71 as in the high frequency circuit package 70 of FIG. There are known ones that are mounted or those that are coated with a liquid ferrite paint (Patent Document 1).
JP-A-6-236935

  However, the ferrite sheet and liquid ferrite paint mounted in the high-frequency circuit package 70 require at least 20% by weight of synthetic resin, resulting in inferior flame resistance.

  Therefore, in order to solve this problem, it is generally performed to improve flame resistance by adding a flame retardant such as decabromodiphenyl oxide, TBA epoxy oligomer / polymer, TBA carbonate oligomer, etc. Since such a flame retardant is a compound containing Br and Cl elements, a desorption gas containing Br and Cl elements is generated when a temperature load is applied.

  When the electromagnetic wave absorber 72 containing such a flame retardant is mounted inside the high-frequency circuit package 70, the package lid 71 and the package base 73 are joined or the high-frequency circuit package 70 and the mother board (not shown) are joined. Since a temperature load is applied, the desorption gas containing Br and Cl elements fills the inside of the high frequency circuit package 40.

Since such a gas is corrosive, there is a problem that a semiconductor element (not shown) mounted inside the high frequency circuit package 70 , a transmission line (not shown) formed on the package base 73, and the like are corroded. was there.

Further, in order to suppress the generation of desorbed gas, functional ceramics, for example, Ni - Zn ferrite also contemplated for use in the electromagnetic wave absorber but, Ni - _Fe 2 _{O 3} constituting the Zn ferrite is usually 50 mol% It can be used only for an electromagnetic wave absorber intended for a frequency band of about several MHz.

  In addition, by arranging an electromagnetic wave absorber on the package lid 71, there is a possibility that even the microwave signal energy of the element is absorbed.

In contrast, in recent years, there has been a demand for an electromagnetic wave absorber used in a high frequency band of 10 GHz or higher. However, even if such Ni — Zn ferrite is used for an electromagnetic wave absorber intended for a high frequency band of 10 GHz or higher, it is desirable. There was a problem that the electromagnetic wave absorption characteristics of the film could not be obtained.

Therefore, the present invention is easy to manufacture, has good electromagnetic wave absorption characteristics, does not generate any desorbed gas, and can easily control the attenuation characteristics of electromagnetic waves, and mainly covers a high frequency band of 10 GHz or more. It is an object of the present invention to provide an electromagnetic wave absorber used for a high-frequency circuit package component and a high-frequency circuit package using the same.

The electromagnetic wave absorber of the present invention is composed of a sintered body containing Fe ₂ O ₃ as a main component and NiO in the balance, and the NiO is present more in the peripheral portion than the central portion of the electromagnetic wave absorber , The main surface of the electromagnetic wave absorber is a processed surface, and the ratio of the peak intensity ratio A of NiFe ₂ O _{4 to} the peak intensity ratio B of Fe ₂ O ₃ in the X-ray diffraction of the processed surface, the value of A / B There it characterized the der Rukoto 1.0 or less.

  In the high frequency circuit package comprising a package base and a package lid attached on the package base, the electromagnetic wave absorber is mounted inside the high frequency circuit package.

  Further, in the high frequency circuit package comprising a package base and a package lid attached on the package base, the package lid is formed of the electromagnetic wave absorber.

According to the electromagnetic wave absorber of the present invention, Fe ₂ O ₃ is the main component, NiO is contained in the remainder, and the NiO is present more in the peripheral portion than in the central portion of the electromagnetic wave absorber. It is possible to obtain excellent electromagnetic wave absorption characteristics and to enable low-temperature firing.

Further, electromagnetic wave absorber by the working surface of the main surface, pressurization and the peak intensity ratio A of NiFe ₂ O ₄ phase in X-ray diffraction cumene, the ratio A between the peak intensity ratio B of _Fe 2 _{O 3} phase When the value of / B is 1.0 or less, good electromagnetic wave absorption characteristics can be obtained, and at the same time, the amount of attenuation can be controlled according to the amount of NiFe ₂ O ₄ phase removed. The degree of freedom in designing a package for a high-frequency circuit using an electromagnetic wave absorber can be increased.

Further, to obtain a package base, in a high-frequency circuit package comprising the attached package lid to the package base on, by wearing the electromagnetic wave absorber inside the package for high frequency circuit, good electromagnetic wave absorption properties At the same time, cavity resonance can be suppressed.

Furthermore, a package base, in a high-frequency circuit package comprising the attached package lid to the package base on, by forming the package lid by electromagnetic waves absorber, at the same time an electromagnetic wave absorption when the number of parts can be reduced The process for attaching the body can be eliminated, and the manufacturing cost can be reduced.

  Next, the best mode for carrying out the present invention will be described.

Electromagnetic wave absorber of the present invention is mainly composed of Fe ₂ O _3, a electromagnetic wave absorber made of a sintered body containing NiO in the remainder periphery than the center portion of the N iO is electromagnetic waves absorber It is important that there are many.

That is, the electromagnetic wave absorber of the present invention is composed mainly of Fe ₂ O _3, but containing NiO in the remainder, by the inclusion of NiO in the remainder, it is possible to reduce the volume resistivity of the electromagnetic wave absorber Therefore, good electromagnetic wave absorption characteristics can be obtained, and furthermore , the sintered body can be sintered at a low temperature.

And, in order to act electromagnetic wave absorption characteristics of the electromagnetic wave absorber more effectively, although the volume resistivity of the electromagnetic wave absorber that is has good low as possible, especially electromagnetic wave absorber surface layer of It is important that the volume resistivity value is small.

Therefore, by the amount of NiO contained in the electromagnetic wave absorber is determined, the more NiO than the center portion of the electromagnetic wave absorber is present in the periphery of the electromagnetic waves absorber volume The resistance value can be reduced.

Then, on how the presence of NiO in the present invention, it is necessary to more NiO is present in the peripheral portion than the central portion of the electromagnetic waves absorber, more preferably toward the peripheral portion from the central portion It is preferable that the slope increases continuously. Alternatively, it may be inclined in steps.

Further, regarding the abundance ratio of the NiO amount of the present invention, the ratio of the NiO amount to the Fe ₂ O ₃ of the electromagnetic wave absorber is measured by X-ray diffraction at each of three locations at the peripheral portion and the central portion, and the average value is used for the central portion The ratio of the peripheral edge with respect to is obtained, and the larger the value, the greater the amount of NiO at the peripheral edge.

Here, the existence ratio of the peripheral portion with respect to the central portion of the NiO amount is set to be larger than 1. Was greater than 1 indicates that NiO is abundant in the peripheral portion than the central portion, is because good electromagnetic wave absorption characteristics can be obtained, NiO is increases less volume resistivity becomes 1 or less Therefore, the electromagnetic wave absorption characteristics are deteriorated.

  In addition, instead of X-ray diffraction, measurement may be performed by an analysis method such as fluorescent X-ray analysis (XRF), atomic absorption / emission analysis (ICP), or the like.

The amount of the thus NiO is to make sure that you are often present in the peripheral portion than the central portion of the electromagnetic waves absorber general, using the method of quantitative analysis of ceramic radiation absorbing What is necessary is just to measure the amount of NiO in the central part and the peripheral part in the cross section of the body. For example, the amount of NiO can be measured by an analysis method such as X-ray fluorescence analysis (XRF) or atomic absorption / emission analysis (ICP). That's fine. Furthermore, the more simply, by X-ray diffraction method, the ratio of numbers of NiO with respect to Fe ₂ O ₃ of the electromagnetic wave absorber were measured in the peripheral portion and the central portion, with respect to the ratio of the centered portion, the peripheral edge The value of the part ratio may exceed 1 in the range of the present invention.

Here, since the sintered body constituting the electromagnetic wave absorber of the present invention increases the content of Fe ₂ O ₃ as described above, the sinterability tends to deteriorate, but generally contains Fe ₂ O ₃ . The amount is preferably 70 to 95 mol%.

  And by containing a predetermined amount of NiO in this, a dense sintered body can be obtained at a low temperature, and such an electromagnetic wave absorber can obtain a large amount of attenuation of electromagnetic waves. It is preferable to contain 10 to 30 mol% of NiO with respect to the absorber.

Here, the content of Fe ₂ O ₃ is set to 70 mol% or more. Although electromagnetic wave absorption characteristics are good when the content is 50 mol% or more and less than 70 mol%, even if the content of Fe ₂ O ₃ is slightly different, This is because the sensitivity to the absorption characteristics is large, making it difficult to design a package for a high-frequency circuit.

On the other hand, the reason why the content of Fe ₂ O ₃ is set to 95 mol% or less is that when it exceeds 95 mol%, sintering becomes difficult and good electromagnetic wave absorption characteristics may not be obtained.

The distribution state of NiO in the electromagnetic wave absorber can also be controlled by the firing temperature and the holding time at the maximum temperature. The firing temperature is 1200 to 1400 ° C., from the viewpoint of greater attenuation of the electromagnetic wave is obtained, preferably important that a 1,250-1400 ° C.. 0-4 hours at retention times, preferably, important to a 2-4 hours.

That is, by the NiO in electromagnetic wave absorber but is trying to evaporate by moving the sintered body interior during firing, in the range of retention times described above in the firing temperature and the highest temperature at this time, NiO is moved toward the peripheral portion from the center portion of the electromagnetic wave absorber, with so abundant in the peripheral portion than the central portion of the electromagnetic wave absorber, retention time the longer in within range, have a tendency of inclination It will be.

  In addition, although the above-described inclination is generally continuous, a part or a step of continuous inclination is formed by sintering by previously forming a part where NiO is present partly before firing the electromagnetic wave absorber. Alternatively, it may be inclined.

The electromagnetic wave absorber major surface a working surface, and the peak intensity ratio A of NiFe ₂ O ₄ in the X-ray diffraction of the pressurized cumene, the ratio of the peak intensity ratio B of _Fe 2 _{O 3} A / The value of B is 1.0 or less.

That is, electric and baked a wave absorber, but the surface of the sintered body is the layer having a NiFe ₂ O ₄ phase is precipitated, NiFe ₂ O ₄ phase is Fe having a corundum structure by having a spinel structure _When densified from ₂ O ₃ phase to prevent moisture and gas from adsorbing into the pores from the outside, and fixing the electromagnetic wave absorber inside the high frequency circuit package with solder as described later such as, for upper gel adhesion, usually, Cr layer on the abutment surface of the electromagnetic wave absorber, Ni layer and metallizing the order of Au layer, by precipitating a layer having a NiFe ₂ O ₄ phase, Ni layer, in metallization of Au layer alone, although there is an advantage that the adhesion can be ensured, however, while the NiFe ₂ O ₄ phase to adversely affect the electromagnetic wave absorption characteristics, it magnitude attenuation If wave absorber is required, it is preferable that the removal processing.

Then, the present inventors have intensive studies results, the NiFe ₂ O ₄ phase deposited on the surface of the sintered body grinding and / or by removing machining by grinding to obtain an excellent sintered body of electromagnetic waves absorption characteristics it it is, the polishing grinding and / or the amount of NiFe ₂ O ₄ phase remaining in the sintered body can be changed, to be able to adjust the attenuation of the electromagnetic wave as an electromagnetic wave absorber I found out.

In order to obtain such an effect, as shown in FIG. 3, the ratio of the peak intensity ratio A of NiFe ₂ O ₄ and the peak intensity ratio B of the surface of Fe ₂ O ₃ in X-ray diffraction is A. / well by obtaining the value of B, by the value of the a / B is 1.0 or less, but Ru can get a good sintered body having electromagnetic wave absorbing property, and when it exceeds 1.0, NiFe ₂ The O ₄ phase becomes the main crystal phase and good electromagnetic wave absorption characteristics cannot be obtained.

Further, as shown in FIG. 1, a high frequency circuit board 14 on which a semiconductor element (not shown) is mounted is attached, a package base 12 having a transmission line 15 formed on the surface thereof, and a package lid attached on the package base 12 the internal high-frequency circuit package 10 consisting of a body 11 Prefecture, N NiFe ₂ O ₄ phase is used in the main crystalline phase to the electromagnetic wave absorber obtained by surface many separate out easily cause cavity resonance, the electromagnetic wave absorber of the present invention When 16 is mounted, it is possible to suppress the air-dong resonance together the good electromagnetic wave absorption characteristics can be obtained.

In addition, it is important that the electromagnetic wave absorber 16 does not contain a compound containing Br, Cl, and S elements. Electromagnetic wave absorber 16 is Br, Cl, as containing compound containing S element, when mounting the electromagnetic wave absorber 16 package within 10 for high frequency circuit, a semiconductor element (not shown) and a transmission line 15, etc. This is because it corrodes. Since the electromagnetic wave absorber 16 of the present invention is made of a ferrite ceramic and does not essentially contain a compound containing Br, Cl, and S elements, it corrodes a semiconductor element (not shown), the transmission line 15 and the like. There is nothing.

However, the electromagnetic wave absorber 16 of the present invention, SiO ₂ and Ca, Al, Co, Cu, also contain several 100ppm metal elements such as Mn as an inevitable impurity, the semiconductor device (not shown) and a transmission line 15, etc. Since it does not corrode, there is no problem.

  Next, the electromagnetic wave absorber of the present invention is produced by the following method.

First, a raw material powder of 50 mol% or more of Fe ₂ O ₃ and a raw material powder of NiO are mixed with water in a ball mill or bead building, and then wet-mixed for 6 to 10 hours to obtain a slurry having a predetermined viscosity. .

Here, when the Fe ₂ O ₃ raw material powder or NiO raw material powder is charged into a ball mill or a bead building, known curing agents, curing aids, lubricants, plasticizers, dispersants, release agents are within the scope of the present invention. A small amount of a colorant, a colorant, and an extender (inorganic material) may be added.

In order to ensure sinterability, it is preferable to use Fe ₂ O ₃ raw material powder or NiO raw material powder having an average particle size of 1 μm or less, preferably 0.85 μm or less.

Further, from the viewpoint of enabling molding at a lower pressure, it is preferable to add at least one raw material powder of ZnO ₂ , CuO ₂ , Bi ₂ O ₃ , and the total addition amount is 5 to 10 mol%. In particular, Ru suitable der. By doing in this way, the cost reduction of the apparatus used for shaping | molding can be measured, and the electromagnetic wave absorber of a complicated shape can also be produced now.

Then, using a spray dryer, drying the slurries, after granulation, the desired forming means The obtained granulated powder, for example, by powder compression molding method to obtain a molded body of arbitrary shape.

Alternatively, a material obtained by drying the slurries do calcined synthesized at about 700 to 900 ° C., ground in a ball mill or beads mill, dried again with a spray drier, a desired forming means, such as a powder pressing You may produce the molded object of arbitrary shapes by the method.

Here, in the case of using a powder compression molding method, the molding pressure may be, for example, 98～298MPa.

Then, the formed feature 1200 to 1400 ° C., after keeping time has fired at 0-4 hours, the electromagnetic wave absorber of the present invention can be obtained by cooling at 300 to 500 ° C. / hour.

After firing, grinding and / or to remove the NiFe ₂ O ₄ phase of the outermost surface portion subjected to processing such as polishing.

Thus obtained electromagnetic wave absorber of this is not limited to a rectangular parallelepiped, cylinder, cone, triangular prism, a triangular pyramid, a combination thereof or may be present void portion therein electromagnetic wave absorber. Further, the position where the electromagnetic wave absorber is mounted may be anywhere inside the high frequency circuit package as long as the characteristics of the high frequency circuit package are not affected and the cavity resonance can be suppressed.

When mounting the electromagnetic wave absorber 16 of the present invention within the package 10 for high frequency circuits, to the package lid 11, may be fixed to the electromagnetic wave absorber 16 with a thermosetting resin adhesive of solder or publicly known . When using a thermosetting resin adhesive, it is particularly preferable to use an epoxy resin.

  Here, it is important that the solder or the thermosetting resin adhesive does not contain a compound of Br, Cl, and S elements. As described above, if a compound of Br, Cl, S element is included, it causes corrosion of the semiconductor element (not shown), the transmission line 15 and the like.

Moreover, using solder, when fixing the electromagnetic wave absorber 16 to the package lid 11, in order to improve adhesion, metallization in order of advance Ni layer, Au layer on the abutment surface of the electromagnetic wave absorber of the present invention It is preferable to keep it.

Alternatively, a thermosetting resin-based adhesive (hereinafter, simply referred to as an adhesive.) When fixing the electromagnetic wave absorber 16 to the package lid 11 with a Young's modulus of the adhesive 10GPa or less, especially 5GPa below Preferably there is. This is because the material of the package lid 11 and the material of the electromagnetic wave absorber 16 usually have different linear expansion coefficients. Therefore, when the Young's modulus of the adhesive is greater than 10 GPa, the stress generated in the electromagnetic wave absorber 16 is sufficiently increased. This is because the high frequency circuit package 10 is destroyed without being able to be relaxed.

  As an adhesive satisfying these conditions, an epoxy resin is preferable, and a bisphenol A type epoxy resin is particularly preferable.

  In addition, the electromagnetic wave absorber 16 is bonded to the package lid 11 by printing and applying an adhesive on the electromagnetic wave absorber 16 or the package lid 11 in advance, and then contacting the electromagnetic wave absorber 16 and the package lid 11. In this state, it is obtained by heat treatment at a predetermined temperature.

  The electromagnetic wave absorber 16 preferably has open pores. If there are open pores on the surface in contact with the package lid 11, when the electromagnetic wave absorber 16 and the package lid 11 are bonded, the adhesive enters the open pores of the electromagnetic wave absorber 16 to increase the adhesive strength. Can do. Since there are voids, pores, and the like inside the electromagnetic wave absorber 16, open pores can be obtained by grinding the surface.

  In order to obtain such open pores, the porosity of the electromagnetic wave absorber 16 is preferably about 2% to 15%.

  Such an electromagnetic wave absorber 16 can suppress cavity resonance and unnecessary radiant waves generated from the semiconductor element inside the high frequency circuit package 10, and can be corrosive from the electromagnetic wave absorber 10 and the adhesive. Since no outgassing occurs, a highly reliable high frequency circuit package 10 can be obtained.

  As another embodiment of the present invention, as shown in FIG. 2, in a high frequency circuit package 10 comprising a package base 12 and a package lid 11 attached on the package base 12, the package lid 11 is The electromagnetic wave absorber 16 of the present invention may be formed, and not only can suppress cavity resonance and unnecessary radiation generated from the semiconductor element, but also can reduce the number of components and at the same time for mounting the electromagnetic wave absorber. The process can be abolished, and the manufacturing cost can be reduced.

Incidentally, in the case of forming a package lid 11 in the electromagnetic wave absorber 16 of the present invention, the electromagnetic wave absorber 16 to the characteristics of the package lid, it is preferable that the dense sintered body of less than 2% porosity .

  Examples of the present invention will be described below. The present invention is not limited to the following examples unless it exceeds the gist.

Example 1
First, what was weighed so that the raw material powders of Fe ₂ O ₃ and NiO were in the ratio shown in Table 1 was used as a starting material. The starting material was mixed with water in a ball mill and then wet mixed for 8 hours to obtain a slurry having a predetermined viscosity.

  Next, after drying and granulating the slurry using a spray dryer, the obtained granulated powder was molded at a molding pressure shown in Table 1 by a powder pressure molding method to obtain a molded body.

Then, the formed configuration by grinding after firing the firing conditions shown in Table 1, the outer diameter dimension sample for evaluation was obtained in 3mm × 7mm × 0.4mm. The reason why this dimension is used is that it is attached in the cavity of the package lid 11 shown in FIG.

  The attenuation of electromagnetic waves obtained by mounting the electromagnetic wave absorber 16 was measured as follows.

First, as shown in FIG. 4, the electromagnetic wave absorber 16 was placed on the package base 12 on which the transmission line 15 was formed so as to cover the transmission line 15. Here, the external dimensions of the package base 12 were 10 mm × 10 mm × 0.5 mm .

Next, the probe 17 is pressed against the transmission line 15, and the power reflection coefficient S ₁₁ and the power transmission are transmitted in a frequency band of 10 to 40 GHz by a network analyzer (not shown) connected from the probe 17 via a coaxial cable (not shown). the coefficient _{S 21} was measured.

The attenuation amount of the electromagnetic wave obtained by mounting the electromagnetic wave absorber 16 was calculated by substituting the power reflection coefficient S ₁₁ and the power transmission coefficient S ₂₁ into the following formula.

Attenuation (dB) = | S ₂₁ / (1-S ₁₁ ) |
Here, the package base 12 itself shown in FIG. 4, the power transmission coefficient _{S 21} was used more than -1.5 dB.

Regarding the effect of suppressing the resonance of the electromagnetic wave absorber 16, as shown in FIG. 5, the package base 12 on which the transmission line 15 is formed, and the cavity is attached on the package base 12 and has a cavity of 8 mm × 8 mm × 0.8 mm. Evaluation was performed using a high frequency circuit package 10 including a package lid 11 made of Kovar with Au plating (KOV : Kovar is a registered trademark ).

The electromagnetic wave absorber 16 was joined to the inside of the package lid 12 with a low melting point solder before the package lid 11 was attached to the package base 12.

Regarding the evaluation of resonance suppression of the electromagnetic wave absorber 16, the probe 17 is pressed against the transmission line 15, and power transmission at 10 to 40 GHz is performed by a network analyzer (not shown) connected from the probe 17 via a coaxial cable (not shown). the coefficient _{S 21} measured, good absolute value △ _{S 21} the effect of resonance suppression what was less than 0.05dB of the difference between the power transmission coefficient _{S 21 (o)} when not wearing the electromagnetic wave absorber 16 ◎, ◯ 0.05 dB or more and less than 0.1 dB, △ 0.1 dB or more and less than 0.2 dB △, 0.2 dB or more having no resonance suppression effect As x.

Then by X-ray diffraction for the content of NiO in the present invention, the ratio of Fe ₂ O ₃ and NiO amount of electromagnetic wave absorber, the ratio of the average values measured each three places in the peripheral portion and the central portion in the cross section Table 1 shows. The larger this ratio, the greater the amount of NiO at the periphery.

  In addition, instead of X-ray diffraction, measurement may be performed by an analysis method such as fluorescent X-ray analysis (XRF), atomic absorption / emission analysis (ICP), or the like.

  Table 1 shows the calculation result of the attenuation amount of the electromagnetic wave at the frequency of 40 GHz and the evaluation result of the resonance suppression at 10 to 40 GHz.

  As is clear from the results in Table 1, sample no. No. 16 had a small NiO content ratio and was difficult to sinter at a low temperature. Since a dense sintered body could not be obtained, a large amount of attenuation could not be obtained, and resonance of 0.2 dB or more occurred.

  On the other hand, sample No. 1, 3, 7, 8, and 13 because the sintering temperature was as low as 1150 ° C., and a dense sintered body was not obtained, the abundance ratio of NiO in the peripheral portion with respect to the central portion was as low as 1.0 or less, Only attenuation of less than 5 dB was obtained, and resonance of 0.1 dB or more and less than 0.2 dB occurred.

Sample No. contrast, an embodiment of the present invention 2, 4-6, 9-12, 14, and 15 have a firing temperature of 1250 ° C. or higher, and the ratio of NiO in the peripheral portion to the central portion exceeds 1.0, so an attenuation of 5 dB or more is obtained. Although resonance occurs at 0.05 dB or more and less than 0.1 dB, it is at a level that causes no problem in practice.

As a result of the sample of the present invention a high-frequency circuit package and work made using the package lid and designed evaluated as 6, Sample No. With respect to the high frequency circuit package using the materials 2, 4 to 6, 9 to 12, 14, and 15, good electromagnetic wave absorption characteristics were obtained, and cavity resonance could be suppressed.

(Example 2)
First, what was weighed so that the raw material powders of Fe ₂ O ₃ and NiO were in the ratio shown in Table 2 was used as the starting material. The starting material was mixed with water in a ball mill and then wet mixed for 8 hours to obtain a slurry having a predetermined viscosity.

Next, obtain using a spray dryer, drying the slurries after granulation, the resulting granulated powder with powder compacting method, a molded body by molding at a molding pressure shown in Table 2 It was.

Then, the formed configuration by grinding after firing the firing conditions shown in Table 2, the outer diameter dimension sample for evaluation was obtained in 3mm × 7mm × 0.4mm. The reason why this dimension is used is that it is attached in the cavity of the package lid 11 shown in FIG.

Then, measure the attenuation of the resulting electromagnetic wave by the mounting of the electromagnetic wave absorber 16, the evaluation of the resonance suppressing effect was carried out in the same manner as in Example 1.

The investigation of the crystal structure by X-ray diffraction shows that the X-ray (CuKα ray) is incident on the electromagnetic wave absorber and the reflection angle of the reflected X-ray that is emitted from the electromagnetic wave absorber (incidence of the incident angle). the horizontal axis of the 2 [theta] (°) when formed into a theta, also is indicative of the peak intensity on the vertical axis, the (311) (NiFe ₂ O _4, for example PDF # 10-0325) NiFe ₂ O ₄ surface the ratio between the peak intensity ratio a, and _Fe 2 _{O 3} (e.g., PDF # _Fe 2 _{O 3} of 33-0664) of (104) plane peak intensity ratio of B of, determine the value of a / B.

  Table 2 shows the calculation result of the attenuation amount of the electromagnetic wave at a frequency of 40 GHz and the evaluation result of resonance suppression at 10 to 40 GHz.

As is clear from the results in Table 2, the sample No. Nos. 18, 20, 22-26, and 28-30 have A / B of 1.0 or less, and the Fe ₂ O ₃ phase is the main phase, so that a large attenuation can be obtained. 17, 19, 21, and 27 are not polished, so there are many NiFe ₂ O ₄ phases on the outermost surface, and since A / B exceeds 1.0, a large amount of attenuation cannot be obtained and resonance occurs. resonance of less than 0.2 dB _{S 21} is 0.1dB or more occurs in suppressing evaluation.

Sample No. 31 has low content ratio of NiO, to dense sintered body could not be obtained, a large amount of attenuation can not be obtained, S ₂₁ resonance than 0.2dB occurs.

Incidentally, the high-frequency circuit package using the samples of the present invention to a package lid as shown in FIG. 2 was created made, the result of the implementation were evaluated, Sample No. For the high frequency circuit package using the materials of 18, 20, 22-26, and 28-30, good electromagnetic wave absorption characteristics were obtained, and cavity resonance could be suppressed.

  The present invention can be used for an electromagnetic wave absorber and a package for a high frequency circuit using the same.

It is sectional drawing of the package for high frequency circuits provided with the electromagnetic wave absorber of this invention. It is sectional drawing of the package for high frequency circuits which used the electromagnetic wave absorber of this invention for the package cover body. The peak intensity in X-ray diffraction of the NiFe ₂ O ₄ and _Fe 2 _{O 3} of the electromagnetic wave absorber of the present invention. FIG. It is sectional drawing of the apparatus which measures the attenuation amount of the electromagnetic waves obtained by mounting | wearing with the electromagnetic wave absorber of this invention. It is sectional drawing for evaluating the resonance suppression of the package for high frequency circuits using the electromagnetic wave absorber of this invention. It is sectional drawing of the package for high frequency circuits using the conventional electromagnetic wave absorber.

DESCRIPTION OF SYMBOLS 10 ... Package for high frequency circuits 11 ... Package lid body 12 ... Package base 13 ... Ground 14 ... High frequency circuit board 15 ... Transmission line 16 ... Electromagnetic wave absorber 17 ... Probe 20 ... Device for measuring electromagnetic wave attenuation 70 ... Package for high frequency circuit 71 ... Package lid 72 ... Electromagnetic wave absorber 73 ... Package base 80 ... Main surface of electromagnetic wave absorber 81 ... Inside 82 ... Section

Claims (3)

An electromagnetic wave absorber made of a sintered body containing Fe ₂ O ₃ as a main component and NiO in the balance thereof, wherein the NiO is present more in the periphery than the central portion of the electromagnetic wave absorber, and the electromagnetic wave absorption The main surface of the body is a processed surface, and the value of A / B, which is the ratio between the peak intensity ratio A of NiFe ₂ O ₄ and the peak intensity ratio B of Fe ₂ O ₃ in the X-ray diffraction of the processed surface, is electromagnetic wave absorber according to claim 1.0 or less der Rukoto. A high-frequency circuit package comprising a package base and a package lid attached on the package base, wherein the electromagnetic wave absorber according to claim 1 is mounted inside the high-frequency circuit package. For package. A high frequency circuit package comprising a package base and a package lid mounted on the package base, wherein the package lid is formed of the electromagnetic wave absorber according to claim 1. .

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