JP5693486B2 - High frequency circuit case cover, method for manufacturing the same, and high frequency circuit module using the same - Google Patents

Description

  The present invention relates to a high-frequency circuit case cover, a manufacturing method thereof, and a high-frequency circuit module using the same.

  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 are housed in cases or the like made of metal or ceramic for each circuit functional block, and have a structure that protects mounted elements and circuit conductors and prevents mutual radio wave interference with external circuits. By completely covering the high-frequency circuit with a metal case, mutual radio wave interference with the outside of the case can be prevented. However, self-interference in the metal case cannot be prevented, and in a high-frequency circuit including an amplifier, the radiated radio wave generated from the high-frequency transmission line configured in the metal case is reflected in the case and returned to the amplifier for transmission. There is a case. Depending on the frequency used and the size of the space in the case, cavity resonance may occur. In order to suppress cavity resonance, it is desirable to design an electronic device in consideration of a cut-off frequency determined by a spatial dimension. However, since there are many restrictions that must be satisfied at the same time, such as circuit scale, function, size, etc., it is actually difficult to design with priority on the cutoff frequency.

  In order to suppress the self-interference in these cases, it is effective to provide a radio wave absorber that absorbs unnecessary radio waves generated in the case, and a radio wave absorber using ferrite (magnetic material) is attached to the case. The method has been adopted. This utilizes the electromagnetic wave absorption performance of ferrite. In particular, it is effective to be provided immediately above the high-frequency circuit, and since it can be applied to a sufficiently large area, a configuration of attaching to a cover (case cover surface) facing the high-frequency circuit is common.

  However, ferrite, which has been widely used as a magnetic material for conventional high-frequency magnetic fields, has a low absolute value of μ ″, which is a loss term of complex permeability, and the applicable frequency is up to several hundred MHz, which is a problem. In the GHz band, which is the frequency of the electromagnetic wave that is present, it does not have sufficient absorption performance. Since a soft magnetic metal is suitable for a radio wave absorber suitable for absorption in the GHz band, a sheet-like radio wave absorber in which a soft magnetic metal powder is mixed and dispersed in a resin material has been proposed (patented) Reference 1).

  General resin materials easily generate corrosive gases for semiconductor elements, such as chlorine, bromine, ammonia, hydrogen, and hydrocarbons, as the temperature rises. For this reason, a resin material that does not contain these corrosive elements is used as the sealing resin for the semiconductor device. However, as long as the resin material is used, the generation of moisture is unavoidable even though the amount is small. Water vapor generated as the temperature rises condenses in the electronic device case as the temperature decreases, causing corrosion of short circuits, high-frequency circuit conductors, and semiconductor elements. In particular, a trace amount of water vapor may be fatal in an electronic device that is hermetically sealed. Here, baking at a high temperature for a long time is effective for removing moisture generated from the resin. However, since the batch processing is performed for a long time, the production capacity is reduced, and the cost becomes high.

  In addition, an adhesive serving as a source of corrosive gas cannot be used for joining and fixing the sheet-shaped wave absorber and the cover. For this reason, soldering or low-temperature brazing is used, but for this purpose, a metal layer that gets wet with solder or low-temperature brazing material has to be formed on the radio wave absorber, which is also an expensive structure. . Soft magnetic metal is a very inexpensive material because it contains iron as its main component. However, when such a soft magnetic metal is affixed to a cover and configured as a radio wave absorber, there are many factors that make it expensive. there were.

  In addition, a method is disclosed in which a sintered body having sufficient radio wave absorption performance in the GHz band and almost no generation of corrosive gas or moisture is used as a radio wave absorber and is attached to a lid (Patent Document 2). . However, this radio wave absorber also forms a metal layer and is joined using a solder or brazing material as in the case of the above-described sheet-like radio wave absorber, and is expensive.

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

  As shown in Patent Document 1, ferrite has obtained absorption performance by a method of dispersing soft magnetic metal powder in a resin due to insufficient performance as a radio wave absorber in the GHz band, but the resin cannot avoid generation of moisture, The high-frequency circuit corrosion factor in the case cannot be completely eliminated. In addition, there is a problem that it takes time to manufacture such as a long baking process is necessary for removing moisture, resulting in high cost. In addition, it is essential to form a metal layer on the radio wave absorber for mounting the radio wave absorber, but it is also necessary to form a metal layer that can be soldered or brazed at a low temperature on the cover. There is.

  In Patent Document 2, moisture generation from the radio wave absorber itself is prevented by using the radio wave absorber as a sintered body. However, it is necessary to form a metal layer that can be soldered or brazed to the radio wave absorber and the cover. There is no change in the need for expensive manufacturing processes.

  The present invention has been made in view of the above, and provides a stable and inexpensive cover for a high-frequency circuit case, a manufacturing method thereof, and a high-frequency circuit module using the same without generating corrosive gas and moisture. Objective.

To solve the above problems and achieve the object, the cover for a high frequency circuit case of the present invention includes a soft magnetic material spherical powder of Fe-Si-B-based, free of SiO _2, and 400 ° C. or higher 600 ° C. A radio wave absorber made of a mixture of a Bi-based glass powder having a softening point of less than 8: 2 to 9: 1, a metal or ceramic cover body, the radio wave absorber, A low-temperature sintered metal press-sintered at a sintering temperature of less than 400 ° C. is provided together with the radio wave absorber and the cover main body between the cover main body and the cover main body.

According to the present invention, the radio wave absorber is a Fe-Si-B-based soft magnetic material in the form of spherical powder that absorbs GHz band radio waves generated from the high frequency circuit. It is possible to prevent radio wave leakage to the outside. In addition, a radio wave absorber that does not impair the properties of the soft magnetic material can be obtained by using Bi glass that does not contain SiO ₂ in order to solidify the soft magnetic material powder.

  Further, since both the radio wave absorber and the low-temperature sintered metal are sintered products, there is no generation of corrosive gas and moisture, and there is no fear of corroding the high-frequency circuit. Further, in joining with a low-temperature sintered metal, it is not necessary to provide a metal layer on the radio wave absorber surface and the cover surface, and there is an effect that the cost can be reduced. In order to maintain the characteristics of the soft magnetic material, the glass powder applied to the formation of the radio wave absorber is a low temperature glass material of 400 ° C. or higher and lower than 600 ° C. Since a metal is used, the glass for solidifying the radio wave absorber is not melted again, and a stable high frequency circuit cover with a radio wave absorber can be provided.

1 is a cross-sectional view showing a high-frequency circuit case cover according to Embodiment 1. FIG. FIG. 2 is a sectional view showing the high-frequency circuit module according to the first embodiment. FIG. 3 is a schematic diagram showing a method of manufacturing the radio wave absorber according to the first embodiment. FIG. 4 is a schematic diagram illustrating a method for manufacturing the high-frequency circuit cover according to the first embodiment. FIG. 5 is a graph showing the pass loss frequency characteristics of the Fe—Si—B soft magnetic spherical powder used in the first embodiment. FIG. 6 is a graph showing the pass loss frequency characteristics of the hexagonal ferrite of the comparative example. FIG. 7 is a graph showing the pass loss frequency characteristics of the Fe—Si—B soft magnetic material flat powder of the comparative example. FIG. 8 is a diagram showing the passing loss frequency characteristics of the radio wave absorber when the glass according to Embodiment 1 is added at a weight ratio of 20%. FIG. 9 is a diagram showing the pass loss frequency characteristics of the radio wave absorber when the glass of the comparative example is added by 40% by weight.

  Hereinafter, an embodiment of a high-frequency circuit case cover according to the present invention will be described with reference to the drawings.

Embodiment 1.
FIG. 1 is a cross-sectional view showing an example of a cover for a high-frequency circuit case with a radio wave absorber according to the first embodiment. A radio wave absorber 2 is attached to the surface of a cover body 1 made of metal or ceramic. FIG. 2 is a cross-sectional view showing a high-frequency circuit module using the high-frequency circuit case cover. The cover C for a high-frequency circuit case with a radio wave absorber according to the first embodiment includes a Fe—Si—B lossy soft magnetic spherical powder and a softening that does not contain SiO ₂ and is 400 ° C. or higher and lower than 600 ° C. Radio wave absorber 2 made of a mixture in which Bi-based glass powder having dots is mixed at a weight ratio of 8: 2 to 9: 1, metal or ceramic cover body 1, radio wave absorber 2 and cover body And a low-temperature sintered metal 3 having a sintering temperature of less than 400 ° C., which is press-sintered together with them. The radio wave absorber 2 is composed of a Fe-Si-B soft magnetic spherical powder with high high-frequency loss and Bi-based glass not containing SiO ₂ , and a low-temperature sintered metal 3 is sintered to cover the cover body 1. It is sintered and joined to the surface. Here, Fe-Cu-Nb-Si-B added with Cu and Nb is used as the soft magnetic spherical powder.

  In the high-frequency circuit module using the high-frequency circuit case cover, as shown in FIG. 2, a high-frequency circuit chip 6a and a signal processing circuit chip 6b are formed on a ceramic substrate 4 constituting a multilayer dielectric substrate. Are mounted on the case body 10 made of cylindrical metal. A high-frequency circuit case cover C is attached to the case body 10 so that the radio wave absorber 2 is located at a position opposite to the high-frequency circuit chip 6a. The high-frequency circuit chip 6 a and the circuit chip 6 b are electrically connected to the circuit pattern 5 formed on the ceramic substrate 4 through bonding wires 7. Usually, in a high-frequency circuit module, a transmission unit such as a waveguide is often mounted, but the description thereof is omitted here.

Next, a method for manufacturing the high frequency circuit case cover will be described. Prior to the description, a method for manufacturing the radio wave absorber 2 will be described first. FIG. 3 is an explanatory diagram of this process. As shown in FIG. 3 (a), mixing the Bi-based glass containing no soft magnetic spherical powder and SiO ₂ of Fe-Si-B system, to obtain the radio wave absorbent powder 2F is further mixed with an organic binder. Then, the radio wave absorber powder 2F is put into a molding die 100 having a desired size and shape, and is press-molded using the press device 200 to obtain a molded pellet 2P (FIG. 3B). At this time, the Fe-Si-B-based soft magnetic spherical powder and the Bi-based glass powder not containing SiO ₂ and having a softening point of 400 to 600 ° C. have a weight ratio of 8: 2 to 9: 1. Mix to be. For example, a cellulose resin is used as the organic binder.

  The radio wave absorber 2 is obtained by firing and sintering the formed pellets 2P. Glass has long been used as a sintering aid because it can be firmly bonded and solidified with metals and ceramics, and has been widely used as a means to solidify and bond functional materials such as conductive materials and resistance materials. In this embodiment, Fe—Si—B soft magnetic spherical powder is used as a functional material.

  Next, a method for joining the radio wave absorber 2 to the cover body 1 will be described. 4A to 4C are process explanatory views. The cover body 1 can be made of metal or ceramic, but here, ceramic is used. FIGS. 4A and 4B are views showing a joining process between the cover main body 1 and the radio wave absorber 2. First, as shown in FIG. 4A, an unfired low-temperature sintered metal 3P is applied to the cover body 1. The unsintered low-temperature sintered metal 3P is obtained by mixing a metal fine particle having a diameter of several nanometers to several micrometers with a solvent, or by drying the paste to form a sheet.

  The unsintered low-temperature sintered metal 3P is a metal having a characteristic that the fine particles are diffusion-bonded at a very low temperature because the metal particles are very small, and gold, silver, copper, etc. can be sintered at a low temperature. As representative. In addition, the unsintered low-temperature sintered metal 3P has a high diffusibility, so that it has a high bondability with other types of metals and ceramics, and a metal layer such as a plating layer to ensure wettability with solder and brazing material Is not necessarily required. Here, the diameter of the metal fine particles constituting the unfired low-temperature sintered metal 3P is set to several nanometers to several micrometers, and the lower limit is selected from the viewpoint of being relatively inexpensive and easy to obtain. The upper limit is set from the viewpoint that dispersibility can be obtained.

  In addition, the unsintered low-temperature sintered metal 3P has a melting point equal to that inherent to the metal element when the sintering is completed, and therefore may melt even if the sintering joining process temperature may be exceeded after sintering. No, it has completely different characteristics from solder and brazing material. In addition, since the raw materials do not contain resin components, there is no generation of gases and moisture that are corrosive to semiconductor devices, such as chlorine, bromine, ammonia, hydrogen, hydrocarbons, etc. There is no worry of contaminating the electronic device case. The sintering temperature can be selected depending on the size of the metal particles and the type of the solvent that suppresses the sintering and the dispersibility of the metal fine particles. In addition, since a glass having a softening point of about 400 to 500 ° C. is used, a glass adjusted to be sintered at less than 400 ° C. was selected. In this embodiment, an Ag nanoparticle paste fired at 300 ° C. in the atmosphere is used as the low-temperature sintered metal. In other words, the low-temperature sintered metal can be fired in the air, and the material is an inexpensive silver material, but the gold material that can be fired in the air or reduced to firing. An inexpensive copper material that requires an atmosphere is also applicable.

  By sandwiching a paste-like or sheet-like unfired low-temperature sintered metal 3P between the ceramic cover body 1 and the radio wave absorber 2, the radio wave absorber 2 is made of metal by heating and firing under pressure of several MPa or more. It joined to the cover main body 1 made from a product or a ceramic (FIG.4 (b)). Pressurization is not necessarily required for sintering of the low-temperature sintered metal, but pressurization is performed in order to achieve stronger bonding and a denser fired product. During sintering, no corrosive gas is generated from the low-temperature sintered metal itself, but sintered products with high porosity are easy to occlude gas and moisture. And prevent sudden increase in gas and moisture.

Since the radio wave absorber 2 is a sintered body, an oxide film is formed on the surface of the soft magnetic body exposed on the surface during firing. For this reason, in the low temperature sintering bonding, it is possible to obtain a stronger bonding by polishing and removing the oxide film and then performing the low temperature sintering bonding. The firing atmosphere must be selected according to the type of the unfired low-temperature sintered metal. For example, copper that requires a reducing atmosphere cannot be fired in air, but gold or silver can be fired in either air or an inert atmosphere. Bi ₂ O ₃ —ZnO—B ₂ O ₃ system (softening point 414 ° C., firing temperature 550 ° C., firing atmosphere is air) was used as the glass to be added.

  A case body 10 containing a high-frequency circuit chip 6a as shown in FIG. 2 is a cover C for a high-frequency circuit case formed by bonding the radio wave absorber 2 to a metal or ceramic cover body 1 with a low-temperature sintered metal 3. When this is applied, it is possible to absorb GHz band radio waves generated from the high frequency circuit chip 6a and prevent resonance within the case and emission of unnecessary radio waves to the outside of the case. In addition, since the radio wave absorber 2 and the low-temperature sintered metal 3 which is a bonding material thereof are sintered bodies, there is no risk of generating corrosive gas or moisture like a resin even when heated, and even a sealed case is accommodated. In addition, it is possible to obtain a highly reliable radio wave absorber 2 that does not contaminate or corrode the high frequency circuit chip 6a.

  In the above embodiment, the cellulose resin is applied as a binder component used for solidifying the magnetic powder and functioning as a radio wave absorber, but is not particularly limited, and cellulose such as ethyl cellulose or methyl cellulose. An acrylic resin such as a methyl resin or methyl methacrylate or ethyl methacrylate can be used.

  The Fe—Si—B-based soft magnetic spherical powder is a lossy magnetic material that absorbs radio waves in the GHz band and is the basic composition of the radio wave absorber 2. In determining the material composition and configuration of the radio wave absorber 2, S21: passage loss (S parameter) when the lossy magnetic material was put on the high-frequency circuit conductor pattern was measured. For measurement, in order to solidify the magnetic powder and function as a radio wave absorber, a binder component and a solvent were mixed to form a paste, which was printed over a high-frequency circuit conductor pattern formed on a ceramic substrate, and fired. Here, since the properties of the magnetic material are purely compared and the strength as a radio wave absorber is not required, glass as a sintering aid is not mixed.

  FIG. 5 shows high-frequency transmission loss characteristics when Fe-Si-B soft magnetic spherical powder is used, and FIG. 6 shows high-frequency transmission loss when hexagonal ferrite that has been conventionally used as a radio wave absorber is used. The characteristics are shown. As shown in FIGS. 5 and 6, the Fe—Si—B soft magnetic material has a larger passage loss than the hexagonal ferrite. A large amount of passage loss means that the radio wave absorption performance is high. As shown in FIG. 5, the Fe-Si-B soft magnetic spherical powder is recognized to be effective in radio wave absorption performance in the GHz band. It was. The hexagonal ferrite shown in FIG. 6 has a small amount of passing loss in the GHz band and has a very low radio wave absorption performance and is not effective.

  Next, in order to investigate the influence of the particle shape of the Fe-Si-B soft magnetic powder on the passage loss, the high-frequency circuit conductor is used when the particle shape of the Fe-Si-B soft magnetic material is a flat powder. S21 when the pattern was covered with a lossy magnetic material: Passage loss was measured. Again, since the properties of the magnetic material are purely compared and the strength as a radio wave absorber is not required, glass as a sintering aid is not mixed. The flat powder is a flat powder obtained by crushing a spherical powder. FIG. 7 shows the result of measuring the passage loss when the lossy magnetic material is put on the high-frequency circuit conductor pattern. FIG. 7 shows the high-frequency passage loss when the particle shape is a flat powder. Compared with the high-frequency passage loss when the soft magnetic material shown in FIG. 5 is a spherical powder, flat powder has a passage loss amount in the GHz band. It was confirmed that the smaller spherical powder was more effective as a radio wave absorbing performance. In the case of flat powder, the high-frequency passage loss is small because of the flat shape, the powder distribution direction with respect to high-frequency radio waves passing therethrough is inappropriate, and the thickness of the soft magnetic material is insufficient.

Next, the mixing amount of the glass powder for forming the radio wave absorber will be described. As the glass powder, Bi-based glass powder not containing SiO ₂ and having a softening point of 400 ° C. or higher and lower than 600 ° C. is used. Glass sintering is used to bind the Fe-Si-B soft magnetic powder and solidify it as the radio wave absorber 2, but the amount of Bi glass powder to be mixed (glass amount) and the mixing ratio of the soft magnetic powder. Therefore, the loss of magnetic material as a radio wave absorber was formed by changing the amount of glass mixed with the radio wave absorber powder 2F (see FIG. 3), and the passage loss was measured. Here, S21: Passing loss when this lossy magnetic material was put on the high-frequency circuit conductor pattern was measured. 5, FIG. 8, and FIG. 9 show the relationship between the passing loss with respect to the mixing weight ratio of the Bi-based glass powder, and FIG. 5 shows the case where the mixing weight ratio of the glass is 0% as described above. Shows a case where the mixing weight ratio of glass is 20%, and FIG. 9 shows a case where the mixing weight ratio of glass is 40%. As can be seen from FIGS. 5, 8, and 9, when the glass mixing weight ratio is 0%, the passage loss amount is the largest, and as the glass mixing ratio increases, the passage loss amount decreases, and the glass mixing weight shown in FIG. When the ratio was 40%, the high-frequency loss characteristics almost disappeared. The high-frequency loss characteristics were recognized to be effective up to a glass mixing weight ratio of 20% as shown in FIG. 8, but when the glass mixing weight ratio was less than 10%, it was difficult to bond and solidify soft magnetic powder. is there. From the above results, the mixing weight ratio of glass is optimally 10 to 20% having frequency loss characteristics.

Next, in determining the type of glass to be mixed with the soft magnetic powder, the correlation between the firing temperature and the change in physical properties of the Fe-Si-B soft magnetic spherical powder material was examined. Fe-Si-B-based soft magnetic spherical powder material is a sintered product having a firing temperature of 1500 ° C. or higher, but if the temperature is raised again to a temperature exceeding 600 ° C., the crystallization reaction and oxidation reaction proceed, and the high frequency loss performance is improved. Since it is known that the temperature is lowered, it is necessary to select a temperature at which these reactions do not occur as the firing temperature, and a glass having a low softening temperature is selected. Specifically, it is Bi-based glass that does not contain SiO ₂ , is composed of Bi ₂ O ₃ , ZnO, B ₂ O _3, and can be sintered at a softening point of about 400 to 500 ° C. and less than 600 ° C. Glass is suitable. Since the glass containing SiO ₂ has a high softening point even if it is Bi-based, it is not suitable for sintering without impairing the high-frequency loss characteristics of the Fe—Si—B-based soft magnetic material. The softening point of the Bi-based glass used here is preferably about 400 to 500 ° C. from the viewpoint of maintaining the high-frequency loss characteristics of the Fe—Si—B based soft magnetic material. That's fine.

In this way, the selected material structure, Fe-Si-B system soft magnetic spherical powder material and SiO ₂ and Bi-based glass powder that does not contain 8: 2 to 9: 1 were mixed in a weight ratio, an organic binder To prepare a radio wave absorber powder 2F. As shown in FIG. 3, the radio wave absorber powder 2F is put into a molding die 100 having a desired size and shape, and 50 MPa or more (powder is solid) using a press apparatus 200. The molded article 2P was formed by pressurizing with a pressing force of 2), and the molded pellets 2P were formed and fired and sintered to produce the radio wave absorber 2.

  The radio wave absorber 2 thus obtained is placed on a metal or ceramic cover body with an unsintered low-temperature sintered metal 3P having a sintering temperature of less than 400 ° C. and sintered at less than 400 ° C. Since the cover is made, it is possible to provide a low-cost cover for a high-frequency circuit with a radio wave absorber that is inexpensive, does not generate corrosive gas and moisture, and does not have a risk of corroding the high-frequency circuit.

  In addition, as the unfired low-temperature sintered metal, metal fine particles that can be fired in the air were used as a paste or a sheet obtained by drying the paste, and this was sandwiched between the radio wave absorber and the cover body. When the unsintered low-temperature sintered metal is made into a paste, it may be applied to the required thickness and adjustment is easy. On the other hand, in the case of a sheet, it is easy to handle because it only needs to be sandwiched.

  In the above embodiment, the radio wave absorber 2 is formed only in the region of the cover body 1 facing the high frequency circuit chip 6a. However, the radio wave is almost entirely covered by the cover body 1 so as to reach the circuit chip 6b. The absorber 2 may be formed.

  As described above, according to the present embodiment, it is possible to provide a high-frequency circuit case cover having excellent high-frequency performance and having a long life and a high-reliability high-frequency circuit module using the same.

  In the above embodiment, the ceramic substrate constituting the multilayer dielectric substrate is used as the substrate on which the high-frequency circuit chip is mounted. Needless to say, a single-layer dielectric substrate may be used, but a metal or ceramic substrate is used. Can be used. The cover body 1 can also be made of metal or ceramic.

  As described above, the radio frequency circuit cover with a radio wave absorber according to the present invention can be formed into a radio wave absorber having a structure free from corrosive gas and moisture generation. high. In addition, since it is a sintered body, the material is hardly deteriorated even in a high humidity environment, and stable high frequency radio wave absorption performance can be exhibited in a wide range of installation environments. If the wave absorber is less than 400 ° C, the structure of the sintered body is maintained, the low-temperature sintered metal does not remelt at about 400 ° C, and if the soft magnetic material is less than 600 ° C, the wave absorption performance is impaired. Therefore, it can be used as a radio wave absorber in a high temperature environment of less than 400 ° C.

C Cover for radio frequency circuit case with radio wave absorber 1 Cover body 2 Radio wave absorber 2F Radio wave absorber powder 2P Molded pellet 3 Low temperature sintered metal 3P Unsintered low temperature sintered metal 4 Ceramic substrate 6a High frequency circuit chip 6b Circuit chip 10 Case body 100 Mold 200 Pressing device

Claims (6)

Fe-Si-B-based soft magnetic spherical powder and Bi-based glass powder not containing SiO ₂ and having a softening point of 400 to 600 ° C. are mixed at a weight ratio of 8: 2 to 9: 1. An electromagnetic wave absorber made of a sintered body of a mixture,
A metal or ceramic cover body;
A high-frequency circuit case with a radio wave absorber comprising a low-temperature sintered metal pressure-sintered and bonded at a sintering temperature of less than 400 ° C. between the radio wave absorber and the cover body. cover.   The radio wave absorber is a sintered body obtained by adding a binder component to the soft magnetic spherical powder and the glass powder, press molding, and sintering at a temperature of less than 600 ° C. The cover for a high-frequency circuit case with a radio wave absorber according to claim 1. Preparing a cover body made of metal or ceramic;
Fe-Si-B-based soft magnetic spherical powder and Bi-based glass powder not containing SiO ₂ and having a softening point of 400 to less than 600 ° C. were mixed at a weight ratio of 8: 2 to 9: 1. Sintering the mixture to form a radio wave absorber;
A step of adjusting a low-temperature-sinterable green low-temperature sintered material having a sintering temperature of less than 400 ° C .;
For a high-frequency circuit case with a radio wave absorber, including a step of sandwiching the unsintered low-temperature sintered material between the radio wave absorber and the cover main body and pressurizing and sintering together with the non-fired low-temperature sintered material Manufacturing method of the cover.   The step of forming the radio wave absorber includes a step of adding a binder component to the soft magnetic spherical powder and the glass powder, press molding, and sintering at a temperature of less than 600 ° C. 4. A method for manufacturing a cover for a high-frequency circuit case with a radio wave absorber according to 3.   The step of adjusting the low-temperature sintering material includes a step of forming metal fine particles having a diameter of several nanometers to several micrometers that can be fired in the form of a paste or a sheet obtained by drying the paste. A method for producing a cover for a high-frequency circuit case with a radio wave absorber according to 3 or 4. The case body,
A high frequency circuit chip mounted on a dielectric substrate and housed in the case body;
A high frequency circuit module including a radio frequency circuit case cover with a radio wave absorber,
The cover for the high-frequency circuit case with the radio wave absorber is,
Fe-Si-B-based soft magnetic spherical powder and Bi-based glass powder not containing SiO ₂ and having a softening point of 400 to less than 600 ° C. were mixed at a weight ratio of 8: 2 to 9: 1. An electromagnetic wave absorber made of a sintered body of a mixture;
A metal or ceramic cover body;
A high-frequency circuit module comprising: a low-temperature sintered metal pressure-sintered and bonded at a sintering temperature of less than 400 ° C. between the radio wave absorber and the cover body.

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