JP2005072156A - Package lid for high-frequency circuit and its manufacturing method, and high-frequency circuit package using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a package for a high-frequency circuit which excels in transmission characteristics and reliability by suppressing cavity resonance. <P>SOLUTION: A package lid 10 for a high-frequency circuit has such a structure that a metallic substrate 11 formed with a metal film 11b on the surface, and an electromagnetic wave absorber 12 which consists of a sintered body mainly made of Fe<SB>2</SB>O<SB>3</SB>and containing NiO in the remaining portion and which is formed with a metal film 12b on the surface, are bonded together by a brazing material 13. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical element package used for high-speed information communication and high-frequency measurement, and a high-frequency circuit package lid used for a high-frequency circuit package and the like.

  In optical element packages and high-frequency circuit packages, a lid made of metal or ceramics is attached to a package base made of metal or ceramics to provide hermetic sealing to protect the semiconductor elements and transmission lines mounted inside. Do. Accordingly, since a substantially rectangular parallelepiped cavity is formed in these high-frequency circuit packages, the high-frequency circuit package has the same properties as the rectangular cavity resonator.

  Therefore, cavity resonance occurs in a frequency band higher than the cut-off frequency determined by the dimensions of the cavity, and transmission characteristics at high frequencies are deteriorated. Therefore, an optical element, a high-frequency semiconductor element or other circuit element operating in the frequency band is packaged. In the case of mounting, it is necessary to make the cutoff frequency sufficiently higher than the frequency band in which the element operates by reducing the size of the cavity.

  However, in the above method, as the operating frequency of the element increases, the frequency at which the cavity resonance occurs is lower than the frequency band in which the element operates. Therefore, the cavity resonance occurs in the vicinity of the operating frequency of the element. There is a problem that characteristics deteriorate.

  In particular, in recent years, demands for higher speeds of optical communication and wireless communication have increased, and the operating frequency of these elements has been increased more and more, and such a problem is inevitable.

  Furthermore, the high frequency circuit package may cause not only cavity resonance but also an oscillation phenomenon of an amplifier mounted in the high frequency circuit package.

  That is, radiation waves from the high-frequency transmission line formed in the high-frequency circuit package and the high-frequency semiconductor element are reflected by the lid, thereby causing feedback of unnecessary signals between the amplifier input / output lines and generating unnecessary oscillation. .

  As shown in FIG. 3, a conventional high-frequency circuit package includes a circuit board 32 made of ceramics or the like having a transmission line 38 and a semiconductor element 33 mounted on a metal package base 31 having terminal electrodes 35. After housing and connecting the semiconductor element 33, the terminal electrode 35, and the transmission line 38 with bonding wires 36, a metal lid 34 is joined by a method such as seam welding to form a sealed structure. Yes.

  However, in the case of such a structure, as the operating frequency of the semiconductor element 33 becomes higher, the cavity resonance occurs when the frequency band in which the element 33 operates becomes higher than the frequency at which the cavity resonance occurs. There was a problem that the characteristics deteriorated.

  This phenomenon occurs when radio waves in the signal frequency band are radiated from the semiconductor element 33, the bonding wire 36, the peripheral transmission line 38, and their connection parts, and the radiated radio waves are This is probably because a resonance phenomenon occurs at the coincident frequency, and as a result, transmission characteristics deteriorate.

  In order to solve these problems, as shown in FIG. 4, a metallized layer is formed on one surface of a radio wave absorber 46 made of a sintered body such as ferrite, and the inner surface of the metal lid portion 44 of the high frequency circuit package. A method of suppressing the reflection resonance of the microwave generated in the high frequency circuit package 40 by brazing with the brazing material 45 is proposed (Patent Document 1).

Further, as shown in FIG. 5, the package base 51 on which the high-frequency circuit board 52 and the like are mounted, and the high-frequency circuit board 52 and the like on the approximate package base 51 are disposed on the package base so as to be sealed. A dielectric sealing plate 56 made of a dielectric material, a radio wave absorber 55 disposed outside the dielectric sealing plate 56, and the radio wave absorber 55 so as to shield the radio wave absorber 55 There has been proposed a structure (Patent Document 2) including a metal cap 54 disposed in an enclosed manner.
Japanese Utility Model Publication No. 2-33035 JP 2000-138495 A

  However, the frequency at which the cavity resonance is generated is generally in the range of quasi-millimeter wave and millimeter wave, and the conventional wave absorber 46 made of a sintered body such as ferrite as shown in FIG. The amount of absorption of the electric field and magnetic field energy at the time of the generated cavity resonance is small, and the generation of the cavity resonance cannot be suppressed.

  On the other hand, a radio wave absorber made of a composite material of resin and soft magnetic metal powder is suitable as a radio wave absorber suitable for absorbing electric field and magnetic field energy at the time of cavity resonance generated at frequencies in the quasi-millimeter wave and millimeter wave regions. It is said that.

  However, a radio wave absorber made of a composite material of such a resin and soft magnetic metal powder has low heat resistance, so that it deteriorates due to temperature rise during brazing or outgassing, so high reliability is required. The above-mentioned high-frequency circuit package cannot be used.

  Further, although a method for preventing the influence of outgas generated from the radio wave absorber 55 by a structure as shown in FIG. 5 has been proposed, the configuration of the high-frequency circuit package 50 becomes complicated, the price increases, There is a problem that it is difficult to reduce the size and height of the circuit package 50.

As a result of repeated studies on the above problems, the present invention provides at least a surface of a substrate made of metal or ceramics in a package lid for a high frequency circuit that forms a hermetic sealed package in combination with a package base that houses a high frequency circuit. and forming a metal film on a part, the main component Fe ₂ O _3, to form at least part of the metal film on the surface of the microwave absorber composed of a sintered body containing NiO in the remainder, to the substrate The electromagnetic wave absorber is fixed using a brazing material.

In the high frequency circuit package lid of the present invention, the radio wave absorber is characterized in that the content of Fe ₂ O ₃ is 70 to 95 mol%.

  Furthermore, the high frequency circuit package lid of the present invention is characterized in that the brazing material has a melting point of 100 ° C to 400 ° C.

  Further, in the method for manufacturing a package lid for a high frequency circuit of the present invention, the base and the radio wave absorber are laminated through the brazing material processed into a foil piece, and then in a nitrogen atmosphere having an oxygen concentration of 1000 ppm or less. In addition, the method includes a step of fixing by heating above the melting point temperature of the brazing material.

  Furthermore, the high-frequency circuit package of the present invention comprises the above-mentioned high-frequency circuit package lid and a package base that houses the high-frequency circuit.

According to the present invention, in a high frequency circuit package lid that forms a hermetic sealed package in combination with a package base that accommodates a high frequency circuit, a sintered body containing Fe ₂ O ₃ as a main component and NiO in the remaining portion. By forming a metal film on at least a part of the surface of the radio wave absorber made of, and fixing the radio wave absorber to the base using a brazing material, resonance and oscillation do not occur, and high frequency characteristics are excellent. Therefore, it is possible to obtain a high-frequency circuit package with excellent reliability.

  Hereinafter, a high frequency circuit package lid and a high frequency circuit package will be described as embodiments of the present invention.

  First, as shown in FIG. 1, a lid body 10 composed of a base body 11, a radio wave absorber 12, and a brazing material 13 for fixing both of them is configured.

  Then, for example, as shown in FIG. 2, the lid body 10 is attached to the upper part of the package base 21 on which the high frequency circuit board 22 on which the semiconductor element 23 is mounted, and brazing with an Au—Sn alloy, seam welding, or the like. The high frequency circuit package 20 is configured by hermetically sealing by a method.

The substrate 11 is made of a metal alloy plate such as an Fe—Ni—Co alloy or Fe—Ni alloy, and has a structure in which a metal film 11b comprising two layers of a base layer Ni and a surface layer Au is formed on the entire surface. . The radio wave absorber 12 is made of a sintered body containing Fe ₂ O ₃ as a main component and NiO in the remaining portion, and a metal film 12b is formed on the surface to be fixed to the base 11.

  Here, since the lid 10 has a configuration in which the radio wave absorber 12 is fixed to the base 11 via the brazing material 13, deterioration of high frequency characteristics due to cavity resonance, feedback oscillation, or the like can be prevented.

  Here, considering the wettability with the brazing material 13, the metal films 11b and 12b use metals such as Au, Ag, Al, Sn, Zn, Pd, Cu, Ni, and Fe, and alloys containing these metals. Is preferable, and it may have a structure of one layer or two or more layers. Au is preferable as the surface layer because of its high chemical stability. However, it is preferable that the surface layer is made of Au and its underlying layer is Ni because of its high wettability with solder and high reliability of sealing and bonding.

  Further, in the metal film 12b formed on the radio wave absorber 12, Au is preferable as the surface layer because of its high chemical stability, but the surface layer is particularly high because of its high wettability with solder and high reliability of bonding. Au and its underlayer are preferably Ni, and a Cr layer is preferably provided between them for the purpose of improving the adhesion between the Ni layer and the radio wave absorber.

  The substrate 11 may be made of ceramics such as alumina, steatite, cordierite, etc. instead of a metal plate such as Fe—Ni—Co alloy or Fe—Ni alloy. In this case, the lid 10 and the package are used. As a joining method of the base 21, a metal film is formed in advance by Mo-Mn metallization, then Ni plating, and further Au plating on a ceramic sealing portion, and brazed with a package base and an Au-Sn alloy. You can use this method.

It is important that the radio wave absorber 12 is a sintered body containing Fe ₂ O ₃ as a main component and NiO in the balance.

By making the radio wave absorber 12 a sintered body containing Fe ₂ O ₃ as a main component and NiO in the balance, the radio wave absorber 12 has excellent radio wave absorption characteristics with respect to electromagnetic waves in the quasi-millimeter wave and millimeter wave regions. Therefore, it becomes excellent in heat resistance, and when joining parts by heat treatment, there is little alteration, deformation and strength deterioration, and generation of degassing can be eliminated.

Here, when the content of Fe ₂ O ₃ is less than 50 mol%, the radio wave absorber 12 cannot obtain radio wave absorption characteristics in the quasi-millimeter wave band and the millimeter wave band, and radiates electromagnetic waves generated inside the package. It cannot suppress the cavity resonance phenomenon and the feedback oscillation phenomenon of the amplifier.

In addition, the wave absorber 12 is more preferable that the content of _Fe 2 _{O 3} is 70~95mol%.

The content of Fe ₂ O ₃ is set to 70 mol% or more. When the content of Fe ₂ O ₃ is 50 mol% or more and less than 70 mol%, the radio wave absorption characteristics in the quasi-millimeter wave band and the millimeter wave band are good, but the content of Fe ₂ O ₃ This is because it is difficult to design a high-frequency circuit package because the radio wave absorption characteristics change greatly due to slight fluctuations.

On the other hand, if the content of Fe ₂ O ₃ is 95 mol% or less, if it exceeds 95 mol%, it becomes difficult to sinter depending on the pressure during shaping, and good radio wave absorption characteristics cannot be obtained, This is because the yield decreases.

  In addition, if NiO is not contained at all in the remainder, the volume resistivity of the radio wave absorber increases, and good radio wave absorption characteristics cannot be obtained, and sintering is performed at a low temperature. This is because it becomes difficult.

  The radio wave absorber 12 of the present invention is produced by the following method.

_First, the raw material powder of Fe ₂ O 3 50mol% or more of the raw material powder and NiO, after turning formulated into a ball mill or bead building with water, by performing 6-10 hours wet mixed to obtain a slurry having a predetermined viscosity .

Here, when Fe ₂ O ₃ raw material powder or NiO raw material powder is charged and prepared in a ball mill or bead building, known curing agents, curing aids, plasticizers, dispersants, mold release agents, coloring agents within the scope of the present invention. There is no problem even if a small amount of an agent or a bulking agent (inorganic material) is 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.

Furthermore, from the viewpoint of enabling molding at a lower pressure, it is preferable to add at least one raw material powder of ZnO, CuO, Bi ₂ O ₃ , and the total addition amount is 5 to 10 mol%. This is particularly suitable, and by doing so, it is possible to reduce the cost of an apparatus used for molding, and it is also possible to produce an electromagnetic wave absorber having a complicated shape.

  Next, after drying and granulating the slurry using a spray dryer, the obtained granulated powder is obtained into a desired shape by, for example, a powder pressure molding method.

  Alternatively, the dried slurry is subjected to calcining synthesis at about 700 to 900 ° C., pulverized with a ball mill or bead mill, and dried again with a spray dryer, and then desired molding means, for example, powder pressure molding You may produce the molded object of arbitrary shapes by the method.

  Here, when using the powder pressure molding method, the molding pressure may be, for example, 100 to 300 MPa.

  And after baking the said molded object at 1000-1400 degreeC and holding time 0-2 hours, the electromagnetic wave absorber 12 of this invention is obtained by temperature-falling at 300-500 degreeC / hour.

  Further, the brazing material 13 may be an alloy of two or more kinds of metals such as Sn, Zn, Au, Bi, Cu, Pb, In, and Ag, but wettability with the metal films 11b and 12b. In consideration of the melting point temperature, an alloy such as Au—Sn, Sn—Pb, Sn—Ag—Cu, Sn—Bi—Ag, or In—Sn is preferably used.

  By doing so, the base body 11 and the radio wave absorber 12 are firmly fixed, and the lid body 10 can be used even when the lid body 10 is joined to the package base 21 or when the temperature rises under use conditions. Thus, the radio wave absorber 12 does not fall off and no organic adhesive or the like is used, so that no outgas is generated and the deterioration of the characteristics of the semiconductor element or the like enclosed therein can be prevented.

  At the time of joining, a seam welding method is usually used, and the temperature of the lid 10 rises to near 100 ° C. Therefore, the melting point of the brazing material 13 is preferably 100 ° C or more, and is appropriately selected according to joining conditions. I can do it.

  If the melting point of the brazing material 13 is too high, the metal film 11b on the surface of the base 11 and the metal film 12b on the surface of the radio wave absorber 12 are partially peeled off or the fastening strength is lowered. The melting point of is preferably 400 ° C. or lower.

  Next, a method for manufacturing the high frequency circuit package will be described.

  In the high frequency circuit package lid 10 of the present invention, the base body 11 and the radio wave absorber 12 are laminated through the brazing material 13 previously processed into foil pieces, and the oxygen concentration is controlled to 1000 ppm or less. It is obtained by fixing the base body 11 and the radio wave absorber 12 through the brazing material 13 by heating at a temperature equal to or higher than the melting point temperature of the brazing material 13 in a nitrogen atmosphere.

  Next, a high frequency circuit package 20 using the high frequency circuit package lid 10 of the present invention will be described. As shown in cross-sectional views in FIGS. 1 and 2, the high-frequency circuit package 20 is made of a package base 21 containing a circuit board 22 on which a semiconductor element 23 is mounted, and the lid 10 of the present invention is made of Au—Sn alloy. The inner space 27 is joined so as to be hermetically sealed by attaching or seam welding. A radio wave absorber 12 is fixed to the inner space side of the lid 10 via a metal layer 12b and a brazing material 13, and the semiconductor element 23 is connected to a transmission line 24 on the circuit board 22 by a bonding wire 26 or the like. Further, the transmission line 24 and the terminal electrode 25 on the circuit board 22 are connected by a bonding wire 26 or the like.

  As a result, the radio frequency circuit package 20 is configured so that the radio wave from the semiconductor element 23, the transmission line 24, the bonding wire 25, and the connection portions thereof is absorbed and attenuated by the radio wave absorber 12. As a result of suppressing internal reflection, cavity resonance and oscillation phenomenon are suppressed, and it becomes possible to achieve excellent frequency characteristics at high frequencies.

  As shown in FIGS. 1 and 2, a lid 10 in which a metal base 11 and a radio wave absorber 12 are fixed to a package base 21 mounted with a circuit board 22 on which a semiconductor element 23 is mounted by a brazing material 13. A high frequency circuit package 20 was produced by hermetic sealing by seam welding. Here, the terminal electrode 25 of the high frequency package 20 and the transmission line 24 formed on the circuit board 22 are connected by a bonding wire 26.

  The radio wave absorber 12 was produced by the following method.

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 the starting material. This starting material was put into a ball mill together with water and prepared, and then wet mixing was performed for 8 hours to obtain a slurry having a predetermined viscosity.

  Next, after drying and granulating the slurry using a spray dryer (spray dryer), the resulting granulated powder was molded at a molding pressure of 100 MPa by a powder pressure molding method to obtain a molded body. . And the electromagnetic wave absorber 12 was obtained by baking the said molded object in 1300 degreeC atmosphere in the air.

  Further, a metal film of a base Ni and a surface layer Au is formed on one main surface of the obtained radio wave absorber 12 by a thin film method, and separately Ni and Au are further formed on the surface of the base 11 made of an Fe—Ni—Co alloy. After the metal film was formed by the electrolytic plating method, it was joined using a brazing material so that the radio wave absorber 12 was on the inner space 27 side, and the lid body 10 was obtained.

  Note that the high-frequency circuit package 20 has a substantially rectangular parallelepiped cavity 27 having a size of 10 mm × 10 mm and a height of 5 mm.

First, in order to verify the optimum range of the content of Fe ₂ O ₃ and NiO of the radio wave absorber 12, a lid body was produced using the radio wave absorber 12 with each content changed, and the attenuation amount and the cavity The presence or absence of the effect of suppressing resonance was verified.

  Attenuation is achieved by connecting the port 1 and port 2 of the network analyzer to both ends of a transmission line designed to transmit a high-frequency signal in the measurement range in advance via a coaxial cable and a probe, and covering the transmission line. The amount of change in the power transmission coefficient S21 at 10 GHz when the absorber 12 was placed was measured and used as the attenuation.

  The effect of suppressing the cavity resonance is measured by using a network analyzer, connecting the terminal electrodes 25 on the high frequency input side and output side of the high frequency circuit package 20 to the ports 1 and 2, respectively, In a state where the lid body joined with the sealant was sealed and joined to the high-frequency circuit package 20, the transmission characteristics up to 10 MHz to 70 GHz were measured, and the presence or absence of the cavity resonance suppression effect was confirmed.

As a result, no. 2-No. 6 has the effect of suppressing cavity resonance in the quasi-millimeter wave and millimeter-wave bands, whereas the comparative example does not contain Fe ₂ O ₃ as a main component. 1. No. containing no NiO 7 was inferior in radio wave absorption characteristics and could not suppress cavity resonance in the quasi-millimeter wave and millimeter wave bands, and was difficult to use as the radio wave absorber 12 of the present invention.

More preferably, by making the content of Fe ₂ O ₃ in the range of 70 to 95%, it becomes possible to manufacture in a region where the attenuation of electromagnetic waves is stable against changes in the content of Fe ₂ O _3. This is advantageous because the manufacturing conditions can be easily managed and stable characteristics can be obtained as a radio wave absorber, which improves the yield and facilitates the design of the high-frequency circuit package.

  Next, the presence or absence of a resonance suppression effect when using a conventional lid made of only metal, a lid secured to a conventional radio wave absorber, and the lid 10 of the present invention was confirmed.

  Furthermore, the gas component in the package internal space was measured by the method described in MIL-STD 883E.

  As a result, when the conventional lid made of only metal is used (No. 9), the cavity resonance occurs near 10 GHz and the frequency characteristics of the high-frequency circuit package deteriorate, whereas the lid of the present invention. When the body 10 was used (No. 8), it was confirmed that the cavity resonance was suppressed by the action of the radio wave absorber 12, and the high frequency circuit package 20 having excellent frequency characteristics was obtained.

  In addition, the generation of corrosive gas was not confirmed in the gas component measurement results inside the package, and it was found that the reliability of the semiconductor element was not affected.

  Next, a conventional lid body (No. 10) is used, in which a metal film is formed on the surface of a ferrite plate, and is fixed to a base made of a metal plate with a metal alloy fixing material as in the present invention. As a result of the measurement, ferrite was inferior in the absorption characteristic with respect to the frequency at which the cavity resonance occurs, and therefore the cavity resonance could not be prevented.

Furthermore, the result of measurement using a lid made by bonding a conventional radio wave absorber made of rubber and added with magnetic metal powder with an epoxy adhesive (No. 11), suppression of cavity resonance Good frequency characteristics were obtained, but the gas analysis results in the internal space of the package confirmed the occurrence of corrosive outgas, and the reliability of the semiconductor device is expected to be reduced. Is not suitable as a lid for sealing a high-frequency package that is required.

  Next, in order to confirm the optimum range of the oxygen concentration when the base member 11 and the radio wave absorber 12 are fixed by the brazing material 13, experiments were performed with various oxygen concentrations changed (No. 12 to No. .16).

  The bonding state was confirmed by pulling the radio wave absorber 12 upward in a state where the base 11 was fixed on the lower side, and measuring the stress when the both were peeled off to obtain the bonding strength.

  As a result, in the range exceeding the oxygen concentration of 1000 ppm (No. 12, No. 13), the wettability between the brazing material 13 and the metal films 11b and 12b was poor, and the bonding strength was low even if it was not possible at all.

  On the other hand, in the range of oxygen concentration of 1000 ppm or less (No. 14 to No. 16), the bonding strength was sufficiently high.

  For this reason, it is preferable that the oxygen concentration at the time of fixation is 1000 ppm or less, and considering the strength after the fixation, it can be said that the oxygen concentration is more preferably 500 ppm or less.

  INDUSTRIAL APPLICABILITY The present invention can be applied to an optical element package used for high-speed information communication and high-frequency measurement, and a high-frequency circuit package lid used for a high-frequency circuit package, and as a result, improves the characteristics of various packages. Is possible.

It is sectional drawing of the package cover body for high frequency circuits of this invention. It is sectional drawing of the high frequency circuit package of this invention. It is sectional drawing of the conventional high frequency circuit package. It is sectional drawing of the high frequency circuit package using the conventional electromagnetic wave absorber. It is sectional drawing of the high frequency circuit package using the conventional electromagnetic wave absorber.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... High frequency circuit package cover 11 ... Base | substrate 11b ... Metal film 12 ... Radio wave absorber 12b ... Metal film 13 ... Brazing material 20 ... High frequency circuit package 21 ... Package base 22 ... Circuit board 23 ... Semiconductor element 24 ... Transmission line 25 ... Terminal electrode 26 ... Bonding wire 27 ... Internal space 30 ... High frequency circuit package 31 ... Package base 32 ... Circuit board 33 ... Semiconductor element 34 ... Cover 35 ... Terminal electrode 36 ... Bonding wire 37 ... Internal space 38 ... Transmission line 41 ... Package base 42 ... Circuit board 43 ... Semiconductor element 44 ... Lid 45 ... Brazing material 46 ... Sintered wave absorber 50 ... High frequency circuit package 51 ... Package base 52 · The circuit board 53 ... semiconductor device 54 ... lid body 55 ... radio wave absorber 56 ... dielectric sealing plate

Claims (5)

In a package lid for a high-frequency circuit that forms a hermetic sealed package in combination with a package base that houses a high-frequency circuit, a metal film is formed on at least a part of the surface of a base made of metal or ceramic, and Fe ₂ O ₃ is A metal film is formed on at least a part of the surface of a radio wave absorber made of a sintered body containing NiO as a main component and the balance is fixed to the radio wave absorber using a brazing material on the base. A high-frequency circuit package lid. _2. The high frequency circuit package lid according to claim 1, wherein the electromagnetic wave absorber has a content of Fe ₂ O ₃ of 70 to 95 mol%. The high frequency circuit package lid according to claim 1, wherein the brazing material has a melting point of 100C to 400C. A step of laminating the base body and the radio wave absorber through the brazing material processed into a foil piece, and then heating and fixing the base material and the brazing material in a nitrogen atmosphere with an oxygen concentration of 1000 ppm or less. The manufacturing method of the package cover body for high frequency circuits in any one of Claims 1 thru | or 3 containing these. A high frequency circuit package comprising: the high frequency circuit package lid according to any one of claims 1 to 3; and a package base that houses the high frequency circuit.

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