JP6366496B2 - Radio wave absorber and method of manufacturing radio wave absorber - Google Patents

Description

  The present invention relates to a radio wave absorber suitable for absorbing radio waves in the gigahertz band and a method for manufacturing the radio wave absorber.

  In the field of electronic devices, high frequency and high density mounting are progressing in order to achieve miniaturization and high performance. In particular, high-frequency devices house elements and circuit conductors in metal cases for each functional block of the circuit, protect the mounted elements and circuit conductors from the external environment, and prevent mutual radio wave interference with external circuits. .

  Mutual radio wave interference with the outside of the metal case can be prevented by completely covering the high frequency circuit with the metal case. However, self-interference due to unwanted radio waves generated in the metal case cannot be prevented, and in a high-frequency circuit including an amplifier, radiated radio waves generated from a high-frequency transmission line configured in the metal case are reflected in the metal case and are transmitted to the amplifier. It may oscillate with feedback. Further, the radiated radio wave may cause cavity resonance depending on the use frequency of the high frequency circuit and the size of the space inside the metal case. In order to suppress the cavity resonance, the design should take into account the cut-off frequency determined by the spatial dimensions. However, since there are many restrictions that must be satisfied at the same time, such as circuit scale, function, size, and weight, it is actually difficult to design with priority on the cut-off frequency.

  In order to suppress self-interference and cavity resonance due to these unnecessary radio waves in the metal case, it is effective to provide a radio wave absorber that absorbs the unnecessary radio waves generated in the metal case. Therefore, a method has been adopted in which a radio wave absorber using a magnetic material having a characteristic of absorbing a radio wave due to a magnetic loss such as soft magnetic metal or ferrite is applied to the metal case. . It is effective that the radio wave absorber is provided immediately above or in the vicinity of the high-frequency circuit, and can be provided in a sufficiently large area. Therefore, a configuration in which the radio wave absorber is attached to the inner surface of the case lid, which is a cover facing the high-frequency circuit, is common. It is.

  Ferrite widely used as a radio wave absorber material is sintered at a high temperature of 1000 ° C. or higher and is stable as a substance. However, ferrite has a small amount of absorption for electric field and magnetic field energy, and has sufficient absorption performance for radio waves in the gigahertz (GHz) band even though it is effective for absorbing radio waves in the megahertz (MHz) band. The cavity resonance cannot be suppressed. It is said that a soft magnetic metal is suitable for a radio wave absorber suitable for absorbing radio waves in the gigahertz band, and a sheet-like radio wave absorber in which soft magnetic metal powder is dispersed in a resin material is disclosed in Patent Document 1. . A general resin material generates corrosive gas for a semiconductor element, such as chlorine, bromine, ammonia, hydrogen, hydrocarbons, etc. as the temperature rises. For this reason, in patent document 1, the sheet-like electromagnetic wave absorber is formed using the resin material with few corrosive elements.

  Patent Document 2 discloses that a radio wave absorber is made of a sintered body that has a sufficient radio wave absorption performance in the gigahertz band and has almost no generation of corrosive gas and moisture.

Japanese Patent Laid-Open No. 2004-87686 JP 2005-72156 A

  However, in Patent Document 1, generation of moisture evaporating from the resin material is inevitable. The water vapor generated from the resin as the temperature rises condenses in the metal case as the temperature decreases, causing corrosion of the high-frequency circuit conductor and semiconductor element, and a short circuit. In addition, the resin component may be hydrolyzed by this moisture to generate corrosive ions. In particular, in an electronic device that requires hermetic sealing, a semiconductor bare chip is housed inside, so that a very small amount of water vapor generated from the resin sheet becomes a fatal factor. That is, there is a problem that the corrosion factor of the high frequency circuit cannot be completely eliminated when the radio wave absorber is provided in the metal case.

  Moreover, the sintered compact used for a radio wave absorber in patent document 2 is a kind of ceramics, and in manufacture, slurry of a material powder, drying, granulation or temporary baking, pulverization, granulation, molding, 1200 ° C to 1400 High temperature firing at 0 ° C., grinding and polishing processes are necessary, and there are many manufacturing processes. For this reason, there existed a problem that the manufacturing cost of a radio wave absorber became expensive.

  In addition, both Patent Document 1 and Patent Document 2 are provided with a metal film for soldering, and it is necessary to use a thin film method involving a vacuum batch process. There was a problem that the price increased.

  Note that a method of adhering a radio wave absorber with an adhesive without using soldering is very commonly used. However, since the adhesive is a resin, there is a problem that the generation of moisture is unavoidable like the sheet-like wave absorber.

  The present invention has been made in view of the above, and it is an object of the present invention to provide an inexpensive radio wave absorber that is free from generation of corrosive gas and moisture, can be soldered, and is suitable for absorption of radio waves in the gigahertz band. And

In order to solve the above-described problems and achieve the object, a radio wave absorber according to the present invention includes a soft magnetic powder made of Fe-Si-Cr or Fe-Si-Al , which is an iron-silicon alloy , and 600 ° C. A glass pellet having the following melting point is mixed and solidified in a weight ratio of 6: 4 or more and 9: 1 or less, and a metal layer bonded to one side of the magnetic pellet. Prepare. Metal layer is sinterable at a temperature below the melting point of glass, Ri and Do a sintered body of a solderable metal material other metal member is a layer which is soldered to another metal member.

  According to the present invention, there is an effect that there is no generation of corrosive gas and moisture, soldering is possible, and an inexpensive radio wave absorber suitable for absorbing radio waves in the gigahertz band is obtained.

Sectional drawing which shows the structure of the electromagnetic wave absorber 1 concerning embodiment of this invention (A)-(c) is typical process explanatory drawing which shows the manufacturing method of the magnetic body pellet concerning embodiment of this invention. (A), (b) is process explanatory drawing which shows the manufacturing method of the metal layer concerning embodiment of this invention. Sectional drawing which shows the high frequency circuit module using the electromagnetic wave absorber concerning embodiment of this invention Schematic sectional view showing the configuration of a high-frequency circuit device for measuring the resonance suppression effect of the radio wave absorber according to the embodiment of the present invention The characteristic view which shows the frequency characteristic of the high frequency circuit device provided with the electromagnetic wave absorber concerning embodiment of this invention

  Hereinafter, a radio wave absorber and a method for manufacturing the radio wave absorber according to embodiments of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a cross-sectional view showing a configuration of a radio wave absorber 1 according to an embodiment of the present invention. In the radio wave absorber 1, a soft magnetic powder made of an iron-silicon alloy and glass having a melting point of 600 ° C. or lower were mixed and solidified in a weight ratio range of 6: 4 to 9: 1. A magnetic pellet 2 and a metal layer 3 bonded to one side of the magnetic pellet are provided. The metal layer 3 is made of a sintered body of a metal material that can be sintered at a temperature lower than the melting point of glass and can be soldered to another metal member.

  The magnetic material pellet 2 is a hybrid obtained by solidifying a mixed powder obtained by mixing a soft magnetic metal powder and a glass powder having a melting point of 600 ° C. or lower. The soft magnetic metal powders are bonded to each other by melting the glass powder and solidifying it again. The magnetic pellet 2 is made by joining glass and soft magnetic metal powder together so that the soft magnetic metal powders are joined together via glass.

  The soft magnetic metal powder is a powder of an iron-silicon (Fe—Si) alloy and is a material suitable for absorbing radio waves in the gigahertz band. Examples of the Fe—Si based alloy include Fe—Si—Cr and Fe—Si—Al ternary alloys. An example of the composition of Fe—Si—Cr is a composition having a weight ratio of Fe: Si: Cr = 90.5: 5.5: 4. An example of the composition of Fe—Si—Al is a composition having a weight ratio of Fe: Si: Al = 90.5: 5.5: 4. The Fe—Si alloy contains 90% by weight or more of the main component Fe and 4% by weight or more and 6% by weight or less of Si in order to improve the absorption of radio waves in the gigahertz band.

  Examples of the shape of the soft magnetic metal powder include a spherical shape or a shape in which a sphere is stretched in one direction. Examples of the particle diameter of the soft magnetic metal powder include about 10 μm in the median diameter called D50. The soft magnetic metal powder can be selected from commercially available soft magnetic metal powders having desired radio wave absorption characteristics corresponding to the environment in which the radio wave absorber 1 is used based on magnetic characteristics. In particular, soft magnetic metal powder is suitable as a radio wave absorber material because it can be obtained at a very low cost and with a desired particle size.

  The glass powder only needs to have a melting point within a range in which the physical properties and magnetic properties of the soft magnetic metal powder can be maintained, and the options are wide. Glass powder is comprised with the glass material which has melting | fusing point of 600 degrees C or less. The reason for selecting a glass material having a melting point of 600 ° C. or lower is to avoid physical property modification of the soft magnetic metal powder in the firing process of the soft magnetic metal powder made of Fe—Si based alloy, as will be described later. is there. That is, in the case of a soft magnetic metal powder made of an Fe—Si alloy, when heated at a temperature exceeding 600 ° C., oxide crystals begin to be generated, and the magnetic characteristics change, and the radio wave absorption characteristics as the radio wave absorber 1 Changes. For this reason, it is necessary to suppress the firing temperature of the molded pellet 2P to 600 ° C. or lower. Accordingly, the glass powder needs to be made of a glass material having a melting point of 600 ° C. or lower.

  Examples of such a glass material include bismuth glass and zinc glass. In addition, when soldering the radio wave absorber 1 to a metal case or the like, heat of about 400 ° C. at the maximum is applied to the radio wave absorber 1 through the metal layer 3. For this reason, it is preferable that melting | fusing point is larger than 400 degreeC so that the glass powder contained in the magnetic body pellet 2 may not fuse | melt the glass powder.

  The weight ratio between the soft magnetic metal and the glass in the magnetic pellet 2 is such that the soft magnetic metal is in the range of 60% to 90% by weight and the glass is in the range of 10% to 40% by weight. is there. That is, the weight ratio between the soft magnetic metal and the glass is 6: 4 or more and 9: 1 or less. When the weight ratio of the soft magnetic metal is less than 60% by weight, the radio wave absorptivity as the radio wave absorber 1 is insufficient. When the weight ratio of the soft magnetic metal is larger than 90% by weight, the glass component is too small to become a solid in the firing process and cannot be handled.

  The magnitude | size of the magnetic-material pellet 2 is not limited, It can change suitably with use uses. The thickness of the magnetic pellet 2 is in the range of 0.5 mm or more and 2 mm or less. When the thickness of the magnetic pellet 2 is less than 0.5 mm and is too thin, it is easily broken during the formation process and handling, and sufficient radio wave absorption performance cannot be obtained. When the thickness of the magnetic pellet 2 is larger than 2 mm and is too thick, the electromagnetic wave absorbing performance is excessive, the weight is increased because iron is the main component, and the electronic device on which the electromagnetic wave absorber 1 is mounted. Its thickness and weight also increase. For this reason, it is preferable that the thickness of the magnetic pellet 2 is 0.5 mm or more and 2 mm or less, in which both the radio wave absorption performance and the weight are in an appropriate range.

  The metal layer 3 is a sintered body obtained by sintering an unfired low-temperature sintered metal powder 3F that is a metal that can be soldered to another metal member. The unsintered low-temperature sintered metal powder 3F is a fine metal particle having a particle size of 1 nm or more and 300 nm or less, a sintering temperature is less than 600 ° C., more preferably a sintering temperature is 400 ° C. or less, and These are fine metal particles of metal that can be sintered at a temperature lower than the melting point of the glass contained in the molded pellet 2P. As a material of the unfired low-temperature sintered metal powder 3F, any one metal material among metals such as gold (Au), silver (Ag), copper (Cu), nickel (Ni) is used.

  The radio wave absorber 1 absorbs radio waves in the gigahertz band because the magnetic pellet 2 contains soft magnetic metal that is a material suitable for absorbing radio waves in the gigahertz band. Thereby, for example, when it is arranged in a high-frequency circuit case, self-interference and cavity resonance in the high-frequency circuit case can be prevented, and the emission of unnecessary radio waves to the outside of the high-frequency circuit case can be prevented. The radio wave absorber 1 is composed of a metal material and glass. For this reason, there is no fear that corrosive gas and moisture are generated even when heated, and even if it is placed in a sealed case, the contained high-frequency circuit is not contaminated or corroded. In addition, the radio wave absorber 1 includes a metal layer 3 made of a sintered metal material that can be soldered to another metal member on one surface side of the magnetic pellet 2. It can be easily soldered.

  Below, the manufacturing method of the electromagnetic wave absorber 1 is demonstrated. First, the manufacturing method of the magnetic body pellet 2 is demonstrated. Fig.2 (a)-FIG.2 (c) are typical process explanatory drawings which show the manufacturing method of the magnetic body pellet 2 concerning embodiment. A mixed powder 2F is obtained by mixing a soft magnetic metal powder made of an Fe-Si alloy, a glass powder, and a resin binder powder. Since a solid shape cannot be formed only by the soft magnetic metal powder and the glass powder, a resin binder powder is mixed in the mixed powder 2F. At this time, in the total weight of the soft magnetic metal powder and the glass powder, the ratio of the soft magnetic metal powder is in the range of 60 wt% or more and 90 wt% or less, and the ratio of the glass powder is 10 wt% or more and 40 wt% or less. The range. Glass is used as a bonding aid because it can be firmly bonded to a metal and solidified. As the resin binder powder, for example, a cellulose resin powder can be used.

  Then, as shown in FIG. 2A, the mixed powder 2 </ b> F is put into a molding die 100 having a desired size and shape, and the mixed powder 2 </ b> F is pressure-molded using a dry press apparatus 200. By pressing the mixed powder 2F under high pressure, the soft magnetic metal powder, the glass powder, and the resin binder powder in the mixed powder 2F are brought into close contact with each other and solidified as shown in FIG. Molded pellets 2P are obtained. The press pressure in the pressure molding is set to a pressing force at which the density of the mixed powder 2F is saturated. The press pressure is preferably in the range of 100 MPa to 300 MPa regardless of the types and particle sizes of the soft magnetic metal powder and the glass powder. By setting the range of the press pressure to 100 MPa to 300 MPa, the mixed powder 2F can be solidified and molded reliably.

  The forming pellets 2P are formed by mixing a soft magnetic metal powder, a glass powder, and a resin binder powder to produce a mixed powder 2F, a mold placing process of the mixed powder 2F into the mold 100, and a mixing process. This is a three-step process of pressing the powder 2F into a predetermined shape, and there are few steps, the process itself is simple, and no expensive equipment is required, so that the manufacturing cost can be kept low. Moreover, since the dry process which does not use solvents is performed, handling of the material is easy.

  Next, the glass melted between the soft magnetic metal powder and the soft magnetic metal powder is obtained by firing the molded pellet 2P at a temperature not lower than the melting point of the glass powder contained in the molded pellet 2P and not higher than 600 ° C. in a firing furnace. As a result, the glass and the soft magnetic metal powder are firmly bonded to each other, and the magnetic pellet 2 is obtained as shown in FIG. Here, the reason why the firing temperature is set to 600 ° C. or lower is to avoid the physical property modification of the soft magnetic metal powder made of the Fe—Si alloy. That is, in the case of a soft magnetic metal powder made of an Fe—Si alloy, when heated at a temperature exceeding 600 ° C., oxide crystals begin to be generated, and the magnetic characteristics change, and the radio wave absorption characteristics as the radio wave absorber 1 Changes. For this reason, it is necessary to suppress the firing temperature of the molded pellet 2P to 600 ° C. or lower.

  The inventor examined the change in the composition after heating by heating the soft magnetic metal powder made of Fe-Si alloy at a plurality of different temperatures. As a result, it has been confirmed that when the heating temperature exceeds 600 ° C., oxide starts to be generated in the soft magnetic metal powder made of the Fe—Si based alloy. In consideration of the temperature distribution and temperature variation in the firing furnace, the firing temperature is preferably 550 ° C. or lower in order to reliably prevent the formation of oxide crystals and the change in magnetic properties in the soft magnetic metal powder. .

  In order to set the firing temperature of the molded pellets 2P to 600 ° C. or lower for the above reason, the glass powder mixed with the mixed powder 2F is selected to have a melting point of 600 ° C. or lower. When the firing temperature is 550 ° C., the glass powder mixed with the mixed powder 2F is selected to have a melting point of 550 ° C. or lower. That is, a glass powder having a melting point of 600 ° C. or lower and a temperature lower than the firing temperature of the mixed powder 2F is selected.

  Since the firing temperature is low, the firing furnace does not need to be a high-temperature furnace for ceramic firing corresponding to a firing temperature of about 1000 ° C. to 2000 ° C., and the maximum firing temperature generally used for thick film firing is about 1000 ° C. Can be used. Therefore, the equipment expense of the baking furnace of the shaping | molding pellet 2P can be suppressed, and the increase in manufacturing cost can be suppressed.

  Next, a method for forming the metal layer 3 will be described. FIGS. 3A and 3B are process explanatory views showing a method for manufacturing the metal layer 3. First, as shown in FIG. 3A, an unfired low-temperature sintered metal powder 3F is applied on one surface of the magnetic pellet 2. The application of the unfired low-temperature sintered metal powder 3F is obtained by magnetizing a low-viscosity ink-like coating liquid obtained by dispersing unfired low-temperature sintered metal powder 3F composed of fine metal particles having a particle diameter of 1 nm or more and 300 nm or less in a solvent. It is performed by applying on one surface of the body pellet 2. Application methods such as spinner application and brush application using centrifugal force can be applied to the application liquid. The lower limit of the particle diameter of the fine metal particles is selected from the viewpoint of being relatively inexpensive and easily available, and the upper limit is set from the viewpoint that sufficient dispersibility can be obtained in the solvent.

  Then, the magnetic pellet 2 coated with the unfired low-temperature sintered metal powder 3F is fired in a firing furnace at a temperature lower than the melting point of the glass contained in the magnetic pellet 2 to burn the unfired low-temperature sintered metal powder 3F. Conclude. Thereby, as shown in FIG.3 (b), the metal layer 3 joined on one surface of the magnetic body pellet 2 is formed. Thereby, the electromagnetic wave absorber 1 is obtained.

  The unsintered low-temperature sintered metal powder 3F is composed of fine metal particles having a particle size of 1 nm or more and 300 nm or less, and thus has a feature of sintering at a temperature much lower than that of bulk metal. It is suitable for forming the metal layer 3 on the surface of the magnetic pellet 2.

  The firing temperature of the unfired low-temperature sintered metal powder 3F is in a range equal to or higher than the temperature at which the unfired low-temperature sintered metal powder 3F can be sintered. It can be controlled by adjusting the solvent to be contained in the particle-shaped and ink-like coating liquid. However, the firing temperature of the unfired low-temperature sintered metal powder 3F is included in the magnetic pellet 2 in order to avoid physical property modification of the soft magnetic metal powder made of the Fe—Si based alloy constituting the magnetic pellet 2 and to occur. In order not to melt the glass to be melted, the temperature is lower than the melting point of the glass contained in the magnetic pellet 2. That is, when the firing temperature exceeds 600 ° C., the physical property modification of the soft magnetic metal powder occurs, and the glass contained in the magnetic pellet 2 is composed of a glass material having a melting point of 600 ° C. or less. The firing temperature of the metal powder 3F is set to a temperature of less than 600 ° C. Further, in order to reliably prevent the glass contained in the magnetic pellet 2 from melting, it is preferable that the maximum temperature of the firing temperature of the unfired low-temperature sintered metal powder 3F is 400 ° C.

  Therefore, the unsintered low-temperature sintered metal powder 3F has a sintering temperature of less than 600 ° C., more preferably a sintering temperature of 400 ° C. or less, and a temperature lower than the melting point of the glass contained in the magnetic pellet 2. Sinterable metals can be used. The lower limit of the firing temperature of the unfired low-temperature sintered metal powder 3F is not particularly limited as long as it is a temperature at which the unfired low-temperature sintered metal powder 3F can be reliably sintered, and is set to 150 ° C., for example.

  As the material of such unfired low-temperature sintered metal powder 3F, gold (Au), silver (Ag), copper (Cu), nickel (Ni) that can be soldered to other metal members and can be sintered at low temperature. ) And other metal materials can be used, and the choice of materials is wide. Among them, from the viewpoints of the solder material used when joining the radio wave absorber 1 to the metal case or the cover of the metal case, the difficulty of the soldering process, the cost, the presence or absence of corrosion, etc. Ag is suitable for the material of the sintered metal powder 3F. When the metal layer 3 is made of Ag, there are wide choices of solder materials such as tin (Sn) -based solder, lead (Pb) -based solder, gold-based solder, and the material cost does not become very expensive. .

  Moreover, the formation process of the metal layer 3 is a two-step process of applying the unfired low-temperature sintered metal powder 3F and a sintering process of the unfired low-temperature sintered metal powder 3F. . In addition, since the firing temperature of the unfired low-temperature sintered metal powder 3F is low, the maximum firing temperature generally used for thick film firing is about 1000 ° C., and not the firing furnace. Inexpensive equipment called a furnace can also be applied and the degree of freedom of the process is wide. And in formation of the metal layer 3, since an expensive apparatus like a thin film method is not required, manufacturing cost can be restrained low.

  The bonding mechanism between the magnetic pellet 2 and the unfired low-temperature sintered metal powder 3F is considered to be mainly the anchor effect. Since the magnetic pellet 2 is a composite of soft magnetic metal particles and glass, the surface state of the magnetic pellet 2 is microscopically uneven. The metal layer 3 becomes an adhesion layer in which the unfired low-temperature sintered metal powder 3F is in close contact with the irregularities on the surface of the magnetic pellet 2 filled with fine metal particles of the unfired low-temperature sintered metal powder 3F. Further, an alloy reaction between the soft magnetic metal particles of the magnetic pellet 2 and the fine metal particles of the unfired low-temperature sintered metal powder 3F occurs on a part of the surface of the magnetic pellet 2, and the magnetic pellet 2 and the unfired low-temperature fired It is considered that the adhesion with the metal powder 3F is improved. As a result, it is considered that the magnetic pellet 2 and the metal layer 3 are firmly bonded. Therefore, the glass used for the magnetic pellet 2 is not restricted from the viewpoint of composition in joining with the unfired low-temperature sintered metal powder 3F, and can be used regardless of the glass composition.

  Next, an example of a usage pattern of the radio wave absorber 1 will be described. FIG. 4 is a cross-sectional view showing a high-frequency circuit module using the radio wave absorber 1 according to the present embodiment. In the high-frequency circuit module using the radio wave absorber 1, as shown in FIG. 4, for example, a multilayer dielectric substrate on which a high-frequency circuit 6a on which a semiconductor bare chip is mounted and a circuit 6b on which a semiconductor chip is mounted is configured. A case body 10 made of a cylindrical metal is mounted on the ceramic substrate 4. The high-frequency circuit 6 a and the circuit 6 b are electrically connected to a circuit pattern 5 formed on the ceramic substrate 4 via bonding wires 7. A metal high frequency circuit case cover 9 is attached to the case body 10 to constitute a high frequency circuit case. And the electromagnetic wave absorber 1 is affixed on the inner surface of the high frequency circuit case cover 9 at a position facing the high frequency circuit 6a. In the radio wave absorber 1, the metal layer 3 is soldered to the inner surface of the high frequency circuit case cover 9 with a solder material 8.

  The radio wave absorber 1 absorbs gigahertz band radio waves generated from the high frequency circuit 6a, can prevent self-interference and cavity resonance in the high frequency circuit case, and can prevent unnecessary radio waves from radiating outside the high frequency circuit case. Further, since the radio wave absorber 1 is composed of a metal material and glass, there is no risk of generating corrosive gas and moisture even when heated, and even in a sealed case, the contained high frequency circuit and semiconductor device components are contaminated. No corrosion or corrosion.

  The radio wave absorber 1 includes a metal layer 3 made of a sintered metal material that can be soldered to another metal member on one surface side of the magnetic pellet 2. It can be easily soldered.

  FIG. 5 is a schematic cross-sectional view showing the configuration of the high-frequency circuit device 21 for measuring the resonance suppression effect of the radio wave absorber 1 according to the present embodiment. The high-frequency circuit device 21 has an airtight configuration in which a metal cover 23 is attached to a metal device case 22. The high-frequency circuit device 21 has a spatial design having a resonance point at 12.5 GHz. A radio wave absorber 1 on which a metal layer 3 is formed is attached to a cover 23 with a solder material 8.

  In the formation of the magnetic pellet 2 of the radio wave absorber 1, an Fe—Si based alloy powder having a Fe weight ratio of 90% or more was used as the soft magnetic metal powder. Further, two types of magnetic pellets 2 were produced using glass A and glass B having the same melting temperature but different compositions. The melting points of glass A and glass B are both greater than 400 ° C. Two types of magnetic pellets 2 were both formed by firing at 550 ° C. In forming the metal layer 3, sintering was performed by sintering at 400 ° C. using Ag as an unfired low-temperature sintered metal. A high frequency circuit device including the radio wave absorber 1 using the glass A is referred to as a device A, and a high frequency circuit device including the radio wave absorber 1 using the glass B is referred to as a device B. The radio wave absorber 1 was soldered to the cover 23 with an inexpensive Sn-based solder.

  A signal pin 24 and a signal pin 25 are inserted into the bottom of the device case 22 from the outside. The signal pin 24 is connected to a radio wave transmitter (not shown). The signal pin 25 is connected to a radio wave detector (not shown).

  The high-frequency circuit device 21 has a minimum configuration necessary for measuring the resonance suppression effect of the radio wave absorber 1 and is not equipped with a circuit such as a semiconductor element. As described above, for the solder joint between the metal layer 3 and the cover 23, a solder material such as Sn-based solder, Pb-based solder, or Au-based solder can be used as the solder material 8. Therefore, it is possible to obtain a radio wave absorber that can be used even in an airtight device.

  Further, although the metal layer 3 is a low-temperature sintered body, it has a melting point corresponding to the element itself after sintering, and if Ag, the melting point exceeds 900 ° C. For this reason, when soldering the radio wave absorber 1, it is not necessary to match the melting point of the solder material, and soldering may be performed at a temperature at which the glass constituting the magnetic pellet 2 does not melt. Wide range of options. Even when 400 ° C. is selected as the maximum soldering temperature at which the melting of the glass constituting the magnetic pellet 2 can be reliably suppressed, the soldering temperature of the Sn-based solder, Pb-based solder, and Au-based solder having a soldering operation temperature of less than 400 ° C. Either can be used.

  FIG. 6 is a characteristic diagram showing a high-frequency pass loss characteristic of the high-frequency circuit device 21 including the radio wave absorber 1 according to the present embodiment. FIG. 6 shows the S parameter S21 which is the pass characteristic between the signal pin 24 and the signal pin 25 in the high frequency circuit device 21 shown in FIG. Here, the passage characteristic of the radio signal that passes through the signal pin 25 when the radio signal is input from the signal pin 24 is shown. Moreover, the frequency characteristics of the device C having the same configuration as that of the high-frequency circuit device 21 except that the radio wave absorber 1 is not attached are also shown in FIG. A large amount of passage loss, that is, a small numerical value on the vertical axis in FIG. 6 means that the radio wave absorber has high radio wave absorption performance.

  In the device C to which the radio wave absorber 1 is not mounted, resonance peaks in the high-frequency circuit device 21 are seen around 12.5 GHz and 18 GHz set to resonate. On the other hand, in the devices A and B to which the radio wave absorber 1 is attached, the resonance in the high frequency circuit device 21 is suppressed near 12.5 GHz and other frequencies set so as to resonate. It turns out that the electromagnetic wave absorption effect is demonstrated.

  Moreover, as a result of comparing the frequency characteristics of the device A and the device B, even if the glass composition contained in the magnetic pellet 2 is different, the high-frequency pass loss characteristics are almost the same if the firing temperature is the same. Further, the metal layer 3 could be formed regardless of the type of glass contained in the magnetic pellet 2.

  As described above, the radio wave absorber 1 according to the present embodiment includes the soft pellets obtained by solidifying the soft magnetic metal powder by mixing the glass powder and the resin binder powder into the unfired low-temperature sintered metal. The powder 3F is fired and joined to the magnetic pellet 2. Therefore, the radio wave absorber 1 does not generate corrosive gas and moisture even when used in a high-temperature usage environment in a high-frequency device, and contaminates or corrodes high-frequency circuits and semiconductor device components housed in the case. There is nothing to do.

  Moreover, since the electromagnetic wave absorber 1 can use the solder which is a metal as a joining material, even if it uses in a high frequency device, it does not generate | occur | produce a corrosive gas and a water | moisture content, and the high frequency circuit and semiconductor which were accommodated in the case Does not contaminate or corrode device parts.

  That is, the radio wave absorber 1 does not generate corrosive gas and moisture in both the radio wave absorber 1 itself and the bonding material for bonding to other members. It is highly effective when used in a high-frequency circuit device that is hermetically sealed.

  In addition, the magnetic pellets 2 and the metal layer 3 constituting the radio wave absorber 1 have few manufacturing processes, the manufacturing process itself is simple, and the firing temperature is low, so no expensive equipment is required. An inexpensive radio wave absorber 1 can be realized.

  Therefore, according to this embodiment, there is no generation of corrosive gas and moisture even under a high temperature use environment, and soldering is possible, and an inexpensive radio wave absorber suitable for absorbing radio waves in the gigahertz band can be obtained.

  The configuration described in the above embodiment shows an example of the contents of the present invention, and can be combined with another known technique, and can be combined with other configurations without departing from the gist of the present invention. It is also possible to omit or change the part.

  1 radio wave absorber, 2 magnetic pellet, 2F mixed powder, 2P molded pellet, 3 metal layer, 3F unfired low temperature sintered metal powder, 4 ceramic substrate, 5 circuit pattern, 6a high frequency circuit, 6b circuit, 7 bonding wire , 8 Solder material, 9 Cover for high frequency circuit case, 10 Case body, 21 High frequency circuit device, 22 Device case, 23 Cover, 24, 25 Signal pin, 100 Mold, 200 Dry press machine.

Claims (6)

A soft magnetic powder composed of Fe-Si-Cr or Fe-Si-Al, which is an iron-silicon alloy , and a glass having a melting point of 600 [deg.] C. or less, a weight ratio of 6: 4 or more and 9: 1 or less. Magnetic pellets mixed and solidified with
A metal layer bonded to one side of the magnetic pellet;
With
The metal layer is sinterable at a temperature below the melting point of the glass, and Ri Do a sintered body of a solderable metal material other metal member, a layer which is soldered to the other metal member that is,
An electromagnetic wave absorber characterized by. The metal material is any one of gold, silver, copper and nickel;
The radio wave absorber according to claim 1. The soft magnetic material powder made of Fe-Si-Cr or Fe-Si-Al, which is an iron-silicon alloy , and the glass powder having a melting point of 600 ° C. or less have a weight ratio of 6: 4 or more and 9: 1 or less. A first step of firing the mixed powder mixed in the range of at least a melting point of the glass at a temperature of 600 ° C. or less to form a magnetic pellet;
A second step of applying a powder of a metal material that can be sintered at a temperature lower than the melting point of the glass and solderable to another metal member to one surface of the magnetic pellet;
A layer that is fired at a temperature equal to or higher than the temperature at which the metal material can be sintered and lower than the melting point of the glass, and is then soldered to the other metal member. A third step of joining the metal layer sintered with the metal material to one surface of the magnetic pellet;
A method for producing a radio wave absorber, comprising: The second step includes a step of applying a coating liquid in which a powder of the metal material having a particle size of 1 nm or more and 300 nm or less is dispersed in a solvent to one surface of the magnetic pellet;
The manufacturing method of the electromagnetic wave absorber of Claim 3 characterized by these. The metal material is any one of gold, silver, copper and nickel;
The method for manufacturing a radio wave absorber according to claim 3 or 4, wherein: The first step includes
Forming a molded pellet obtained by press molding the mixed powder obtained by adding a resin binder powder to the soft magnetic powder and the glass powder;
Firing the molded pellets at a temperature not lower than the melting point of the glass and not higher than 600 ° C .;
The method for manufacturing a radio wave absorber according to any one of claims 3 to 5, wherein: