JP2014011769A - Radio frequency module board and manufacturing method for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radio frequency module board and a manufacturing method for the radio frequency module board which is capable of improving an antenna characteristic with a simple configuration and is easy to manufacture.SOLUTION: An antenna board unit 100 includes a dielectric layer 10 and a first insulating layer 20. The dielectric layer 10 is made of a porous material. An antenna pattern 11 having a square shape is formed in a predetermined region on the upper surface of the dielectric layer 10. The first insulating layer 20 is installed on the lower surface of the dielectric layer 10 so as to sandwich a ground pattern 21. The ground pattern 21 has a slot 21s as an aperture. The slot 21s is arranged so as to be opposite to the center part of the antenna pattern 11 while sandwiching the dielectric layer 10 between the slot 21s and the antenna pattern 11. A microstrip line 22a capable of supplying high-frequency power is formed on the lower surface of the first insulating layer 20. Relative permittivity of the dielectric layer 10 at frequency of 1 GHz is set to be equal to or smaller than 2.00.

Description

  The present invention relates to a radio frequency module substrate including an antenna element and a manufacturing method thereof.

  Development of an antenna-integrated RF (radio frequency) module capable of transmitting or receiving millimeter waves is in progress. For example, a planar antenna is used for such an RF module. The planar antenna has a configuration in which an antenna element is provided on a dielectric substrate.

  The size of the antenna element of the planar antenna is proportional to the wavelength of the radio wave transmitted or received, and inversely proportional to the square root of the relative dielectric constant of the dielectric substrate. The microwave has a wavelength of about 1 cm to about 1 m. In order to reduce the size of a microwave antenna element, it is known to increase the relative dielectric constant of a dielectric substrate.

  In contrast, millimeter waves have a wavelength of about 1 mm to about 10 mm or less. As described above, the size of the millimeter-wave antenna element is sufficiently smaller than the size of the microwave antenna element or the like. Therefore, it is not necessary to increase the relative dielectric constant of the dielectric substrate of the millimeter wave planar antenna. Therefore, in the antenna element for millimeter waves, it is preferable to lower the dielectric constant of the dielectric substrate in order to expand the frequency band of the antenna element and obtain a high gain.

  Patent Document 1 describes a dipole antenna substrate including a dipole antenna, a dielectric substrate, and a ground layer. A dipole antenna composed of a strip-shaped conductor layer is formed on the surface of the dielectric substrate, and a ground layer is formed on the back surface of the dielectric substrate. In this dipole antenna substrate, notches are formed in portions of the dielectric substrate located on both sides of the dipole antenna with respect to the central axis of the dipole antenna. Thereby, the effective dielectric constant of the dielectric substrate is reduced.

  Patent Document 2 describes an antenna device in which a gap is formed between a patch conductor and a ground conductor.

JP-A-10-335927 International Publication No. 2004/09539

  However, in the dipole antenna substrate described in Patent Document 1, it is necessary to form a notch with high accuracy in the dielectric substrate. Therefore, the number of manufacturing steps increases and the manufacturing process becomes complicated.

  In the antenna device described in Patent Document 2, the gap between the patch conductor and the ground conductor is formed by a spacer. Therefore, the number of parts in the antenna device increases and the configuration becomes complicated. Further, since the spacer needs to be manufactured with high accuracy, the manufacturing process becomes complicated.

  An object of the present invention is to provide a radio frequency module substrate that can improve antenna characteristics with a simple configuration and is easy to manufacture, and a method for manufacturing the same.

  (1) A substrate for a radio frequency module according to a first invention is formed on a first insulating layer having first and second surfaces facing each other, and a first surface of the first insulating layer, A grounding conductor layer having an opening, a dielectric layer formed of a porous material on the grounding conductor layer, an antenna element formed on the dielectric layer so as to overlap the opening of the grounding conductor layer, and a grounding conductor A conductor pattern formed on the second surface of the first insulating layer so as to overlap the opening of the layer, and the antenna element, the opening of the ground conductor layer, and the conductor pattern have high-frequency power applied to the conductor pattern. The antenna element is disposed so as to be electromagnetically coupled to the conductor pattern through the opening when supplied or received by the antenna element, and the dielectric constant of the dielectric layer at a frequency of 1 GHz is 2.00 or less It is.

  In the radio frequency module substrate, the antenna element is electromagnetically coupled to the conductor pattern through the opening of the ground conductor layer when the high frequency power is supplied to the conductor pattern. Thereby, a radio wave is radiated from the antenna element. Further, the antenna element is electromagnetically coupled to the conductor pattern through the opening of the ground conductor layer when the radio wave is received by the antenna element. Thereby, high frequency power is generated in the conductor pattern.

  In this case, since the relative dielectric constant of the dielectric layer at a frequency of 1 GHz is set to 2.00 or less by using the porous material, the radiation efficiency of the radio wave by the antenna element is improved. In addition, the frequency band of radio waves that can be radiated and received by the antenna element is expanded.

  Furthermore, by using a dielectric layer formed of a porous material, the relative dielectric constant of the region between the antenna element and the ground conductor layer can be easily reduced without using a complicated configuration.

  As a result, the antenna characteristics can be improved with a simple configuration, and the radio frequency module substrate can be easily manufactured.

  (2) The average hole diameter of the plurality of holes included in the dielectric layer may be 5 μm or less, and the ratio of the volume of the plurality of holes per unit volume of the dielectric layer may be 40% or more.

  In this case, when the average hole diameter of the plurality of holes is 5 μm or less, the dielectric constant of the dielectric layer can be lowered without reducing the mechanical strength of the dielectric layer. Further, since the volume ratio of the plurality of holes per unit volume of the dielectric layer is 40% or more, the plurality of holes are uniformly dispersed in the dielectric layer. Thereby, the occurrence of variations in the relative dielectric constant in the dielectric layer is suppressed.

  (3) The porous material may be made of a porous resin.

  The relative dielectric constant of the resin is lower than that of other materials such as glass and ceramic. Thereby, the dielectric constant of the dielectric layer can be sufficiently reduced.

  (4) The resin may be polyimide or polyetherimide.

  Polyimide and polyetherimide have a characteristic that the amount of dimensional change when temperature changes is small. Therefore, a highly reliable radio frequency module substrate can be manufactured.

  (5) The dielectric loss tangent of the dielectric layer at a frequency of 1 GHz may be 0.005 or less.

  In this case, dielectric loss due to the dielectric layer is reduced. This improves the radiation efficiency of radio waves when high-frequency power is supplied to the antenna element. In addition, the reception efficiency of radio waves by the antenna element is improved.

  (6) The radio frequency module substrate further includes a second insulating layer formed on the second surface of the first insulating layer so as to cover the conductor pattern, and the second insulating layer has high frequency power. There is a mounting area in which an electronic component having an output or input power terminal and a ground terminal can be mounted, and the mounting area of the second insulating layer is electrically connected to the conductor pattern and is a power terminal of the electronic component And a second terminal that is electrically connected to the ground conductor layer and that can be connected to the ground terminal of the electronic component.

  In this case, a small radio frequency module can be easily manufactured by mounting the electronic component on the mounting area of the radio frequency module substrate.

  (7) The electronic component further includes an external terminal for input or output of an external signal or supply of a power supply voltage, and a third insulating layer mounting region can be connected to the external terminal of the electronic component. And a wiring pattern extending from the third terminal to the outside of the mounting region may be formed on the second insulating layer.

  In this case, an external signal can be input or output through the wiring pattern to the electronic component mounted on the radio frequency module substrate, or the power supply voltage can be easily supplied.

  (8) A method for manufacturing a radio frequency module substrate according to a second aspect of the invention includes a laminated structure including a conductor pattern, an insulating layer, a ground conductor layer having an opening, a dielectric layer made of a porous material, and an antenna element in this order. The antenna element, the opening of the ground conductor layer, and the conductor pattern are electromagnetically connected to the conductor pattern through the opening when the high frequency power is supplied to the conductor pattern or when the antenna element receives radio waves. The relative permittivity of the dielectric layers arranged so as to be coupled and having a frequency of 1 GHz is 2.00 or less.

  According to the radio frequency module substrate manufacturing method, a laminated structure including a conductor pattern, an insulating layer, a ground conductor layer having an opening, a dielectric layer made of a porous material, and an antenna element in this order is formed. In this laminated structure, the antenna element is electromagnetically coupled to the conductor pattern through the opening of the ground conductor layer when high-frequency power is supplied to the conductor pattern. Thereby, a radio wave is radiated from the antenna element. Further, the antenna element is electromagnetically coupled to the conductor pattern through the opening of the ground conductor layer when the radio wave is received by the antenna element. Thereby, high frequency power is generated in the conductor pattern.

  In this case, since the relative dielectric constant of the dielectric layer at a frequency of 1 GHz is set to 2.00 or less by using the porous material, the radiation efficiency of the radio wave by the antenna element is improved. In addition, the frequency band of radio waves that can be radiated and received by the antenna element is expanded.

  Furthermore, by using a dielectric layer formed of a porous material, the relative dielectric constant of the region between the antenna element and the ground conductor layer can be easily reduced without using a complicated configuration.

  As a result, the antenna characteristics can be improved with a simple configuration, and the radio frequency module substrate can be easily manufactured.

  (9) The step of forming the laminated structure includes a step of preparing an insulating layer having first and second surfaces facing each other, a step of forming a ground conductor layer on the first surface of the insulating layer, Forming a dielectric layer comprising: forming a conductor pattern on the second surface of the layer; forming a dielectric layer on the ground conductor layer; and forming an antenna element on the dielectric layer. A step of applying a composition containing a flowable resin and a phase separation agent for phase separation to the cured resin on the ground conductor layer, and a microphase on the ground conductor layer by curing the resin. A step of forming a resin film having a separation structure and a step of removing the phase separation agent from the resin film may be included.

  In this case, an insulating layer having first and second surfaces facing each other is prepared, and a ground conductor layer is formed on the first surface of the insulating layer. A conductor pattern is formed on the second surface of the insulating layer, and a dielectric layer is formed on the ground conductor layer. An antenna element is formed on the dielectric layer.

  At the time of forming the dielectric layer, a composition containing a flowable resin and a phase separation agent that phase-separates with respect to the cured resin is applied on the ground conductor layer, and then the resin is cured to form the ground conductor layer. A resin film having a microphase separation structure is formed above. Thereafter, the phase separation agent is removed from the resin membrane.

  In this way, the dielectric layer is formed on the ground conductor layer without using a bonding material such as an adhesive. Further, the antenna element is formed on the dielectric layer without using a bonding material such as an adhesive. As a result, the radio frequency module substrate can be easily manufactured while preventing an increase in the relative permittivity of the region between the antenna element and the ground conductor layer.

  (10) The step of removing the phase separation agent from the resin membrane may include a step of extracting the phase separation agent from the resin membrane by impregnating the resin membrane with a solvent.

  In this case, the phase separation agent phase-separated from the resin in the resin film is dissolved by the solvent. By extracting the dissolved phase separation agent, a plurality of pores are formed in the resin film.

  (11) The resin is a polyamic acid, and the step of forming the dielectric layer may further include a step of converting the polyamic acid to polyimide after the step of removing the phase separation agent from the resin film.

  As a result, a dielectric layer made of porous polyimide can be formed on the ground conductor layer. Polyimide has a characteristic that the amount of dimensional change when temperature changes is small. Therefore, a highly reliable radio frequency module substrate can be manufactured.

  (12) The step of forming the laminated structure includes a step of preparing an insulating layer having first and second surfaces facing each other, and a first conductor layer having an opening on the first surface of the insulating layer. Forming a conductive pattern on the second surface of the insulating layer, preparing a dielectric layer having third and fourth surfaces facing each other, and a second having an opening. The step of forming a conductor layer on the third surface of the dielectric layer, the step of forming an antenna element on the fourth surface of the dielectric layer, and joining the first conductor layer and the second conductor layer And forming a ground conductor layer.

  In this case, an insulating layer having first and second surfaces facing each other is prepared, a first conductor layer having an opening is formed on the first surface of the insulating layer, and the conductor pattern is the first layer of the insulating layer. 2 on the surface. A dielectric layer having third and fourth surfaces facing each other is prepared, a second conductor layer having an opening is formed on the third surface of the dielectric layer, and the antenna element is the first layer of the dielectric layer. 4 is formed on the surface. An antenna element is formed on the fourth surface of the dielectric layer. The ground conductor layer is formed by joining the first conductor layer and the second conductor layer.

  In this way, the second conductor layer having the opening is formed on the third surface of the dielectric layer without using a bonding material such as an adhesive. Further, the antenna element is formed on the fourth surface of the dielectric layer without using a bonding material such as an adhesive. As a result, the radio frequency module substrate can be easily manufactured while preventing an increase in the relative permittivity of the region between the antenna element and the ground conductor layer.

  According to the present invention, the antenna characteristics can be improved with a simple configuration, and the manufacture of the radio frequency module substrate can be facilitated.

(A) is a top view of RF module which concerns on one embodiment of this invention, (b) is a longitudinal cross-sectional view in the AA of (a). It is a schematic diagram which shows the manufacturing method of the antenna board | substrate part of FIG.1 (b). It is a schematic diagram which shows the manufacturing method of RF module using the antenna board | substrate part of FIG.2 (e). It is a schematic diagram which shows the other manufacturing method of the antenna board | substrate part of FIG.1 (b). It is typical sectional drawing which shows the manufacturing method of the three-layer base material of Fig.2 (a). 10 is a schematic diagram for explaining a configuration of a sample of Comparative Example 3. FIG. 10 is a schematic diagram for explaining a configuration of a sample of Comparative Example 5. FIG. It is a figure which shows the simulation result about the sample of Example 1 and Comparative Examples 1 and 2. FIG. It is a figure which shows the simulation result about the sample of Example 1 and Comparative Examples 3 and 4. FIG. It is a figure which shows the simulation result about the sample of Example 1 and Comparative Examples 5 and 6. FIG.

  Hereinafter, a radio frequency module substrate and a manufacturing method thereof will be described with reference to the drawings. In the following description, the radio frequency module is abbreviated as an RF module.

(1) Configuration of RF Module FIG. 1A is a plan view of an RF module according to an embodiment of the present invention, and FIG. 1B is a longitudinal sectional view taken along the line AA in FIG. It is. As shown in FIG. 1, the RF module 1 according to the present embodiment includes an RF module substrate 1A and an RFIC (radio frequency integrated circuit) 1B, and for example, millimeter waves (radio waves in a frequency band of 30 GHz to 300 GHz). Radiate or receive.

  The RF module substrate 1 </ b> A includes an antenna substrate unit 100. The antenna substrate unit 100 includes a dielectric layer 10 and a first insulating layer 20.

  Dielectric layer 10 is made of a porous material and has an upper surface and a lower surface. In the present embodiment, a porous resin is used as the porous material of the dielectric layer 10. An antenna pattern 11 having a square shape is formed in a predetermined region on the upper surface of the dielectric layer 10.

  A first insulating layer 20 is provided on the lower surface of the dielectric layer 10 with a ground pattern 21 interposed therebetween. The first insulating layer 20 has an upper surface and a lower surface. The ground pattern 21 has a rectangular slot 21s as an opening. The slot 21s is disposed so as to face the central portion of the antenna pattern 11 with the dielectric layer 10 interposed therebetween.

  A microstrip line 22 a and a ground pattern 22 b are formed on the lower surface of the first insulating layer 20. The microstrip line 22a is disposed so that a part of the microstrip line 22a faces the central portion of the antenna pattern 11 with the dielectric layer 10, the portion where the slot 21s is formed in the ground pattern 21 and the first insulating layer 20 interposed therebetween. Has been. A through hole 20 h is formed in the formation region of the ground pattern 22 b in the first insulating layer 20. The through hole 20h is filled with copper VC as a conductive material. Thereby, the ground pattern 21 and the ground pattern 22b are electrically connected.

  In the present embodiment, the laminated structure including the dielectric layer 10, the antenna pattern 11, the first insulating layer 20, the ground pattern 21, the microstrip line 22a, and the ground pattern 22b constitutes the antenna substrate unit 100. .

  A second insulating layer 30 is formed on the lower surface of the first insulating layer 20 of the antenna substrate portion 100 so as to cover the microstrip line 22a and the ground pattern 22b. The second insulating layer 30 has an upper surface and a lower surface. A mounting region 1BA in which the RFIC 1B can be mounted is provided on the lower surface of the second insulating layer 30. 1A and 1B, the mounting area 1BA is indicated by a two-dot chain line.

  On the lower surface of the second insulating layer 30, a plurality of electrode patterns 31a, 31b, and 31c are formed in the mounting region 1BA. A wiring pattern 31d is formed so as to extend from the electrode pattern 31c to the outside of the mounting area 1BA.

  Two through holes 30h are formed in the formation region of the two electrode patterns 31a and 31b in the second insulating layer 30, respectively. Each through hole 30h is filled with copper VC as a conductive material. Thereby, the microstrip line 22a and the electrode pattern 31a are electrically connected. The ground pattern 21 and the electrode pattern 31b are electrically connected through the ground pattern 22b.

  Three electrode terminals 40a, 40b, and 40c are formed on the three electrode patterns 31a, 31b, and 31c, respectively.

  Here, the RFIC 1B has a power terminal 50a, a ground terminal 50b, and an external terminal 50c. The power terminal 50a is used for outputting high frequency power from the RFIC 1B or inputting high frequency power to the RFIC 1B. The external terminal 50c is used for outputting an external signal from the RFIC 1B or inputting an external signal to the RFIC 1B. The external terminal 50c may be used for supplying a power supply voltage to the RFIC 1B.

  When the RFIC 1B is mounted on the mounting region 1BA of the second insulating layer 30, the power terminal 50a, the ground terminal 50b, and the external terminal 50c of the RFIC 1B are respectively connected to the electrode terminals 40a, 40b, and 40c via unillustrated solder. Connected. In this state, the sealing resin 41 is filled in the space between the lower surface of the second insulating layer 30 and the RFIC 1B.

  On the lower surface of the second insulating layer 30, a cover insulating layer 42 is formed so as to cover a part of the wiring pattern 31d. Solder balls 43 are provided on the portion of the wiring pattern 31 d exposed from the cover insulating layer 42.

  In the RF module 1 according to the present embodiment, high frequency power is supplied from the power terminal 50a of the RFIC 1B to the microstrip line 22a. Thereby, the antenna pattern 11 is electromagnetically coupled to the microstrip line 22a through the slot 21s of the ground pattern 21. Thereby, radio waves are radiated from the antenna pattern 11.

  In the RF module 1, the antenna pattern 11 is electromagnetically coupled to the microstrip line 22 a through the slot 21 s of the ground pattern 21 when the radio wave is received by the antenna pattern 11. Thereby, high frequency power is generated in the microstrip line 22a. The generated high frequency power is input to the power terminal 50a of the RFIC 1B.

  In the present embodiment, the frequency band of the radio wave radiated from the antenna pattern 11 and the radio wave received by the antenna pattern 11 is preferably 50 GHz or more and 80 GHz or less, and more preferably 55 GHz or more and 77 GHz or less.

(2) Manufacturing Method of Antenna Substrate 100 and RF Module 1 FIG. 2 is a schematic diagram showing a manufacturing method of the antenna substrate 100 of FIG. 2A to 2E, cross-sectional views corresponding to the cross-sectional view taken along the line AA of FIG. 1A are shown.

  First, as shown to Fig.2 (a), the three-layer base material 20x which consists of the 1st insulating layer 20 and the two conductor layers 21x and 22x is prepared. In the three-layer base material 20x, conductor layers 21x and 22x are formed on the upper surface and the lower surface of the first insulating layer 20, respectively.

  The first insulating layer 20 is made of, for example, a liquid crystal polymer or a porous resin. The first insulating layer 20 may be made of the same material as the dielectric layer 10 described later. In this example, the relative dielectric constant of the first insulating layer 20 at a frequency of 1 GHz is, for example, greater than 1.00 and 5 or less, and preferably greater than 1.00 and 3.5 or less.

  The dielectric loss tangent of the first insulating layer 20 at a frequency of 1 GHz is, for example, 0.01 or less, preferably 0.005 or less, and more preferably 0.004 or less.

  The thickness of the first insulating layer 20 is, for example, 20 μm or more and 150 μm or less, preferably 25 μm or more and 125 μm or less, and more preferably 50 μm or more and 100 μm or less.

  The conductor layers 21x and 22x are each made of copper. Each of the conductor layers 21x and 22x has a thickness equal to or greater than the skin depth of the conductor layers 21x and 22x at a frequency of 60 GHz. The thickness of each of the conductor layers 21x and 22x is, for example, not less than 0.5 μm and not more than 35 μm, preferably not less than 1 μm and not more than 20 μm, and more preferably not less than 3 μm and not more than 18 μm.

  Next, as shown in FIG. 2B, a slot 21s of FIG. 1 is formed in the conductor layer 21x by etching a partial region of one conductor layer 21x. Thereby, the ground pattern 21 is formed on the upper surface of the first insulating layer 20. Further, a partial region of the other conductor layer 22x is etched. Thereby, the microstrip line 22 a and the ground pattern 22 b are formed on the lower surface of the first insulating layer 20. Further, a through hole 20h is formed in the formation region of the ground pattern 22b, and copper VC is filled into the through hole 20h by electrolytic plating. In this way, the ground pattern 21 and the ground pattern 22b are electrically connected.

  Next, as shown in FIG. 2C, the dielectric layer 10 is formed on the ground pattern 21 with a porous resin. A method for forming the dielectric layer 10 will be described later. At the time of forming the dielectric layer 10, a part of the porous resin constituting the dielectric layer 10 is filled in the slot 21 s portion of the ground pattern 21.

  In the present embodiment, by using a porous resin for the dielectric layer 10, the relative dielectric constant of the dielectric layer 10 at a frequency of 1 GHz is set to be larger than 1.00 and not larger than 2.00. In this case, radio wave radiation efficiency and reception efficiency in the RF module 1 are improved. In addition, the frequency band of radio waves that can be radiated and received in the RF module 1 is expanded. In order to further improve these antenna characteristics, the dielectric constant of the dielectric layer 10 at a frequency of 1 GHz is preferably greater than 1.00 and less than or equal to 1.60, and greater than 1.00 and less than or equal to 1.50. It is more preferable that

  The relative dielectric constant of the porous material can be determined as follows. First, the complex dielectric constant of the porous material at a frequency of 1 GHz is measured by a cavity resonator tangent method. The real part of the measurement result is the relative dielectric constant of the porous material. For example, by using a cavity resonator with a frequency of 1 GHz (manufactured by Kanto Electronics Application Development Co., Ltd.) and a network analyzer (manufactured by Agilent Technologies; N5230C), a complex of a porous material at a frequency of 1 GHz by a cavity resonator contact method is used. The dielectric constant can be measured.

  The dielectric loss tangent of the dielectric layer 10 at a frequency of 1 GHz is, for example, 0.005 or less. In this case, dielectric loss due to the dielectric layer 10 is reduced, and radio wave radiation efficiency and reception efficiency in the RF module 1 are improved. In order to further improve the radiation efficiency and reception efficiency of radio waves in the RF module 1, the dielectric loss tangent of the dielectric layer 10 at a frequency of 1 GHz is preferably 0.004 or less.

  The thickness of the dielectric layer 10 is, for example, 20 μm or more and 150 μm or less, preferably 25 μm or more and 125 μm or less, and more preferably 50 μm or more and 100 μm or less. When the thickness of the dielectric layer 10 is 20 μm or more, dielectric loss due to the dielectric layer 10 is reduced, and radio wave radiation efficiency and reception efficiency in the RF module 1 are improved. Moreover, when the thickness of the dielectric layer 10 is 150 μm or less, generation of unnecessary higher-order modes in the RF module 1 is suppressed.

  The average hole diameter of the plurality of holes included in the dielectric layer 10 is, for example, larger than 0 μm and not larger than 5 μm, and preferably larger than 0 μm and not larger than 3 μm. When the average hole diameter of the plurality of holes is larger than 0 μm and not larger than 5 μm, the dielectric constant of the dielectric layer 10 is reduced without lowering the insulating property of the dielectric layer 10 and the mechanical strength of the dielectric layer 10. In addition, the dielectric loss tangent can be lowered.

  The average hole diameter of the plurality of holes included in the dielectric layer 10 can be obtained as follows. For example, an image of the cut surface of the dielectric layer 10 is obtained by observing the cut surface of the dielectric layer 10 using a scanning electron microscope. Image processing (binarization processing) is performed on the obtained image. Thereby, a plurality of hole images are extracted. The maximum value of the outer diameter of each hole image is measured for a part of the extracted hole images (about 50 holes from the largest outer shape in order). Based on the measurement result, the average hole diameter of the plurality of holes is calculated.

  The dielectric layer 10 has, for example, a closed cell structure or a semi-continuous semi-closed cell structure. The semi-continuous semi-closed cell structure is a structure in which a closed cell structure and an open-cell structure are mixed. The dielectric layer 10 preferably has a closed cell structure part of 80% or more, and more preferably has a closed cell structure part of 90% or more. According to the closed cell structure, the etching solution is prevented from penetrating into the dielectric layer 10 when the antenna pattern 11 described later is formed. The dielectric layer 10 may have an open cell structure.

  The volume ratio of the plurality of pores per unit volume of the dielectric layer 10 (hereinafter referred to as the porosity) is, for example, 40% or more, preferably 70% or more, and preferably 80% or more. Is more preferable. When the porosity of the dielectric layer 10 is 40% or more, the plurality of holes are uniformly dispersed in the dielectric layer 10. Thereby, the occurrence of variations in relative dielectric constant in the dielectric layer 10 is suppressed.

  The porosity of the dielectric layer 10 can be determined, for example, as follows. The specific gravity of the resin used for the dielectric layer 10 and not made porous is measured. Further, the specific gravity of the porous resin used for the dielectric layer 10 is measured. Then, when the specific gravity of the measured resin is D1 and the specific gravity of the measured porous resin is D2, the porosity P can be calculated using the following formula (1).

P (%) = [1- (D2 / D1)] × 100 (1)
In order to measure the specific gravity of the resin that has not been made porous and the specific gravity of the porous resin, for example, a hydrometer (manufactured by Alpha Mirage; MD-300S) can be used.

  Next, a seed layer made of a laminated film of chromium and copper is formed on the upper surface of the dielectric layer 10 by sputtering, for example. The seed layer is not limited to a laminated film of chromium and copper, but may be a single layer film of chromium, for example. The seed layer may be formed by electroless plating. Thereafter, as shown in FIG. 2D, a conductor layer 11x made of, for example, copper is formed on the entire seed layer by electrolytic plating using a plating solution such as copper sulfate. In FIG. 2D, illustration of the seed layer is omitted.

  Next, as shown in FIG. 2E, the conductor layer 11x and a partial region of the seed layer are etched. Specifically, a resist film such as a photosensitive dry film resist is formed on the conductor layer 11x. Thereafter, the resist film is exposed in a predetermined pattern and then developed using a developer such as sodium carbonate to form an etching resist. Subsequently, the portion of the conductor layer 11x exposed from the etching resist and the portion of the seed layer exposed are etched using an etchant such as ferric chloride. Thereafter, the etching resist is removed from a stripping solution such as sodium hydroxide. Thereby, the antenna pattern 11 including the conductor layer 11x and the seed layer is formed on the upper surface of the dielectric layer 10. Thus, in this example, the antenna pattern 11 is formed by the subtractive method. Thereby, the antenna substrate part 100 is completed.

  The antenna pattern 11 is made of copper. The thickness of the antenna pattern 11 is greater than or equal to the skin depth of the antenna pattern 11 at a frequency of 60 GHz. The thickness of the antenna pattern 11 is, for example, not less than 0.5 μm and not more than 35 μm, preferably not less than 1 μm and not more than 20 μm, and more preferably not less than 3 μm and not more than 18 μm.

  FIG. 3 is a schematic diagram showing a method for manufacturing the RF module 1 using the antenna substrate 100 of FIG. 3A to 3D are cross-sectional views corresponding to the cross-sectional view taken along the line AA in FIG.

  As shown in FIG. 3A, the second insulating layer 30 is formed on the lower surface of the first insulating layer 20 of the antenna substrate portion 100 so as to cover the microstrip line 22a and the ground pattern 22b.

  The second insulating layer 30 is made of, for example, a liquid crystal polymer or a porous resin. The thickness of the second insulating layer 30 is, for example, 20 μm to 150 μm, preferably 25 μm to 125 μm, and more preferably 50 μm to 100 μm.

  When a sheet member made of a liquid crystal polymer or a porous resin is used as the second insulating layer 30, the sheet member is bonded to the lower surface of the first insulating layer 20 by thermocompression bonding. Thereby, the second insulating layer 30 is formed on the lower surface of the first insulating layer 20.

  The second insulating layer 30 may be made of the same material as the dielectric layer 10. When the same material as that of the dielectric layer 10 is used as the second insulating layer 30, the second insulating layer 30 is formed on the lower surface of the first insulating layer 20 by the same method as that for forming the dielectric layer 10 described later. Is formed.

  Next, as shown in FIG. 3B, three electrode patterns 31a, 31b, 31c and a wiring pattern are formed in a predetermined region on the lower surface of the second insulating layer 30 by an additive method, a semi-additive method, a subtractive method, or the like. 31d is formed. Further, two through holes 30h are formed in the formation regions of the two electrode patterns 31a and 31b, respectively, and copper VC is filled in the through holes 30h by electrolytic plating. In this way, the microstrip line 22a and the electrode pattern 31a are electrically connected, and the ground pattern 22b and the electrode pattern 31b are electrically connected. On the lower surface of the second insulating layer 30, a region including the three electrode patterns 31a, 31b, and 31c is set as the mounting region 1BA of the RFIC 1B in FIG.

  The thicknesses of the plurality of electrode patterns 31a and wiring patterns 31d are, for example, not less than 0.5 μm and not more than 35 μm, preferably not less than 1 μm and not more than 20 μm, and more preferably not less than 3 μm and not more than 18 μm.

  Next, as shown in FIG. 3C, three electrode terminals 40a, 40b, and 40c are formed on the three electrode patterns 31a, 31b, and 31c, respectively. As a material of the electrode terminals 40a, 40b, and 40c, a metal material such as gold, silver, or an alloy thereof can be used.

  Further, an insulating cover layer 42 is formed on the lower surface of the second insulating layer 30 so as to cover a part of the wiring pattern 31d. As the material of the insulating cover layer 42, a resin such as polyimide can be used. Further, solder balls 43 are provided on the portion of the wiring pattern 31 d exposed from the cover insulating layer 42.

  Finally, as shown in FIG. 3 (d), the first insulating layer 20 so that the power terminal 50a, the ground terminal 50b, and the external terminal 50c of the RFIC 1B are connected to the three power terminals 40a, 40b, and 40c, respectively. The RFIC 1B is mounted on the mounting area 1BA. Further, a sealing resin 41 is filled in the space between the lower surface of the second insulating layer 30 and the RFIC 1B. Thereby, the RF module 1 of FIG. 1 is completed. As the sealing resin 41, polyimide, epoxy resin, or the like can be used.

(3) Dielectric layer 10
(3-a) Method for Forming Dielectric Layer 10 An example of a method for forming the dielectric layer 10 shown in FIG. The porous resin used for the dielectric layer 10 is preferably a thermosetting resin having heat resistance, engineering plastic or super engineering plastic. The resin for forming the dielectric layer 10 is preferably a resin having a 5% weight reduction temperature of 250 ° C. or higher, and more preferably a resin having a 5% weight reduction temperature of 280 ° C. or higher. When a thermoplastic resin is used as the resin for forming the dielectric layer 10, it is preferable to use a thermoplastic resin having a glass transition temperature of 150 ° C. or higher.

  As the resin for forming the dielectric layer 10, engineering plastics such as polyamide, polycarbonate, polybutylene terephthalate, polyethylene terephthalate, or cyclic polyolefin can be used. Moreover, as resin for forming the dielectric layer 10, super engineering plastics, such as polyphenylene sulfide, polysulfone, polyethersulfone, polyetheretherketone, polyamideimide, polyimide, or polyetherimide, can be used, for example. In addition, as a resin for forming the dielectric layer 10, epoxy resin, phenol resin, melamine resin, urea resin (urea resin), alkyd resin, unsaturated polyester resin, polyurethane, thermosetting polyimide, silicone resin or diallyl A thermosetting resin such as a phthalate resin can be used. As the resin for forming the dielectric layer 10, one of the plurality of resins may be used alone, or a mixture of two or more types of resins may be used.

  Polyimide and polyetherimide have a characteristic that the amount of dimensional change when temperature changes is small. Therefore, it is more preferable to use polyimide and polyetherimide among the above thermoplastic resins as the resin for forming the dielectric layer 10. As a result, a highly reliable RF module substrate 1A (FIG. 1) can be manufactured.

  The polyimide can be obtained, for example, by reacting an organic tetracarboxylic dianhydride and a diamino compound to synthesize a polyimide precursor (polyamic acid), and subjecting the synthesized polyimide precursor to a dehydration ring-closing reaction. Polyetherimide can be obtained, for example, by a dehydration ring-closing reaction between an aromatic bisether anhydride such as 2,2,3,3-tetracarboxydiphenylene ether dianhydride and a diamino compound.

  Hereinafter, a case where polyimide is used as the resin for forming the dielectric layer 10 will be described.

  In this case, examples of the organic tetracarboxylic dianhydride include pyromellitic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,2-bis (2,3- Dicarboxyphenyl) -1,1,1,3,3,3-hexafluoropropane dianhydride, 2,2-bis (3,4-dicarboxyphenyl) -1,1,1,3,3,3 -Hexafluoropropane dianhydride, 3,3 ', 4,4'-benzophenone tetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, bis (3,4 monodicarboxyphenyl) ) A sulfone dianhydride or a mixture of two or more of these organic tetracarboxylic dianhydrides can be used.

  Examples of the diamino compound include m-phenylenediamine, p-phenylenediamine, 3,4′-diaminodiphenyl ether, 4,4′-diaminophenyl ether, 4,4′-diaminodiphenyl sulfone, and 3,3′-diamino. Diphenylsulfone, 2,2-bis (4-aminophenoxyphenyl) propane, 2,2-bis (4-aminophenoxyphenyl) hexafluoropropane, 1,3-bis (4-aminophenoxy) benzene, 1,4- Bis (4-aminophenoxy) benzene, 2,4-diaminotoluene, 2,6-diaminotoluene, diaminodiphenylmethane, 4,4′-diamino-2,2′-dimethylbiphenyl, 2,2′-bis (trifluoro) Methyl) -4,4′-diaminobiphenyl or their diamination It can be a mixture of any two or more of the diamino compound of the object.

  When polyimide is used as the resin for forming the dielectric layer 10, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride is used as the organic tetracarboxylic dianhydride, and the diamino compound is used. Preference is given to using a mixture of p-phenylenediamine and 4,4′-diaminophenyl ether.

  A polyimide precursor is obtained by, for example, reacting an organic tetracarboxylic dianhydride and a diamino compound for a predetermined time (1 hour or more and 24 hours or less) in an organic solvent of 0 ° C. or more and 90 ° C. or less. As the organic solvent, for example, a polar solvent such as N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide or dimethyl sulfoxide can be used. As the organic solvent, aromatic hydrocarbons such as toluene or xylene may be used, alcohols such as methanol, ethanol or isopropyl alcohol may be used, and ketones such as methyl ethyl ketone or acetone may be used. May be. It is preferable to mix 100 parts by weight or more and 500 parts by weight or less of any one of the above organic solvents with respect to 100 parts by weight of the polyimide precursor, and 300 parts by weight or more of any one of the above organic solvents with respect to 100 parts by weight of the resin. It is more preferable to mix 500 parts by weight or less.

  The dehydration cyclization reaction of the polyimide precursor is performed, for example, by heating the polyimide precursor at a temperature of 300 ° C. or higher and 400 ° C. or lower, or by allowing a dehydrating cyclizing agent such as a mixture of acetic anhydride and pyridine to act on the polyimide precursor. .

  In addition, instead of the above example, polyimide produces a polyamic acid silyl ester by reacting an organic tetracarboxylic dianhydride and an N-silylated diamine, and the produced polyamic acid silyl ester is heated. It can also be obtained by ring-closing reaction.

  When producing a porous polyimide, a phase separation agent is mixed with the polyimide precursor obtained as described above. In the present embodiment, the phase separation agent is a compound that is compatible with the fluid polyimide precursor and has the property of phase separation from the cured polyimide precursor.

  As such a phase separation agent, for example, polyalkylene glycol such as polyethylene glycol, tripropylene glycol or polypropylene glycol can be used. Moreover, as a phase-separation agent, the polymethylene glycol one-end methyl blockade may be used, and the polyalkyleneglycol both-end methyl blockade may be used. Moreover, as a phase-separation agent, the poly (alkylene glycol) terminal block (meth) acrylate blockade may be used, and the polyalkyleneglycol both ends (meth) acrylate blockade may be used. A urethane prepolymer may be used as the phase separation agent. Phase separation agents include phenoxy polyethylene glycol (meth) acrylate, ε-caprolactone (meth) acrylate, trimethylolpropane tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, urethane (meth) acrylate, epoxy (Meth) acrylate compounds such as (meth) acrylate or oligoester (meth) acrylate may be used. Moreover, as a phase-separation agent, 1 type of materials may be used among said materials, and 2 or more types of materials may be mixed and used.

  In this example, a fine microphase separation structure can be obtained by using the above phase separation agent. The weight average molecular weight of the phase separation agent is preferably, for example, from 100 to 10,000, and more preferably from 100 to 2,000. When the weight average molecular weight of the phase separation agent is 100 or more, the polyimide precursor and the phase separation agent can be reliably phase separated. Further, when the weight average molecular weight of the phase separation agent is 10,000 or less, the average pore diameter of the plurality of pores contained in the porous polyimide prepared from the polyimide precursor can be easily reduced to 5 μm or less. it can.

  In the present embodiment, the porosity of the dielectric layer 10 is, for example, 40% or more. In order to set the porosity of the dielectric layer 10 to 40% or more, for example, 100 parts by weight of a polyimide precursor is mixed with 25 parts by weight or more and 300 parts by weight or less of a phase separation agent. More preferably, 50 parts by weight or more and 200 parts by weight or less of a phase separation agent is mixed with 100 parts by weight of the polyimide precursor.

  As described above, when a polyimide precursor is used to obtain a porous polyimide, it is preferable to use polyalkylene glycol as a phase separation agent.

  When forming the dielectric layer 10, for example, a composition obtained by mixing the polyimide precursor, the phase separation agent, and the organic solvent is applied onto the ground pattern 21 using a coating machine.

  Next, the phase separation agent is insolubilized with respect to the polyimide precursor by curing the polyimide precursor in the composition. In this state, the organic solvent in the composition applied on the first insulating layer 20 is evaporated. Thereby, a film of a polyimide precursor (hereinafter referred to as a polyamic acid film) is formed on the ground pattern 21 in a state where a microphase separation structure is formed in the composition. When evaporating the organic solvent, the temperature of the composition is preferably adjusted to, for example, 10 ° C. or more and 250 ° C. or less, and more preferably adjusted to 60 ° C. or more and 200 ° C. or less.

  Next, the phase separation agent is extracted from the polyamic acid membrane using a solvent. As the solvent, a solvent that is a good solvent for the phase separation agent and does not dissolve the cured resin (polyamide acid film in this example) is used. As such a solvent, for example, organic solvents such as toluene, ethanol, ethyl acetate and heptane can be used. As the solvent, liquefied carbon dioxide, subcritical carbon dioxide, supercritical carbon dioxide, or the like can be used.

  When liquefied carbon dioxide, subcritical carbon dioxide, or supercritical carbon dioxide is used as a solvent, the temperature and pressure in the pressure vessel are adjusted to those of carbon dioxide after the laminate including the polyamic acid film is accommodated in the pressure vessel. Adjust the temperature and pressure in the pressure vessel so that it is above the critical point. In this case, the atmosphere in the pressure vessel is preferably set to a temperature of 32 ° C. to 230 ° C. and a pressure of 7.3 MPa to 100 MPa, and a temperature of 40 ° C. to 200 ° C. and a pressure of 10 MPa to 50 MPa. More preferably, it is set to.

  In this state, liquefied carbon dioxide, subcritical carbon dioxide or supercritical carbon dioxide is continuously supplied into the pressure vessel, and the atmosphere in the pressure vessel is discharged. Thereby, a solvent osmose | permeates a polyamic-acid membrane and the phase-separation agent in a polyamic-acid membrane is extracted. As a result, the phase separation agent is removed from the polyamic acid film, and a porous polyamic acid film is obtained.

  Finally, the polyamic acid is converted to polyimide by heating the porous polyamic acid film at a temperature of 300 ° C. or higher and 400 ° C. or lower. In this manner, the dielectric layer 10 made of porous polyimide can be formed on the ground pattern 21 without using a bonding material such as an adhesive.

  In the present embodiment, dielectric layer 10 is not limited to resin, and may include an additive. As an additive, a plasticizer, a lubricant, a colorant, an ultraviolet absorber, an antioxidant, a filler, a reinforcing agent, a flame retardant, an antistatic agent, or the like can be used.

(3-b) Specific Example of Method for Forming Dielectric Layer 10 A specific example of the method for forming the dielectric layer 10 will be described. First, 785.3 g of N-methyl-2-pyrrolidone (NMP), 44.1 g of p-phenylenediamine and 20.4 g of 4,4′-diaminodiphenyl ether are placed in a 1000 ml four-flask, and these mixtures are mixed at room temperature. Stir. Thereby, p-phenylenediamine and 4,4′-diaminodiphenyl ether are dissolved in N-methyl-2-pyrrolidone.

  Next, 150.2 g of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride is added to the composition in the four-flask, and p-phenylenediamine, 4,4′-diaminodiphenyl ether, 3 ′, 4,4′-biphenyltetracarboxylic dianhydride is reacted at 25 ° C. for 1 hour. Thereafter, the composition in the four-flask is heated at 75 ° C. for 25 hours. Thereby, a polyamic acid solution (solid content concentration 20 wt%) having a solution viscosity of 160 Pa · s is obtained as the polyimide precursor. The solution viscosity of the polyamic acid solution is measured by, for example, a B-type viscometer.

  To the obtained polyamic acid solution, 120 parts by weight of polypropylene glycol having a weight average molecular weight of 400 as a phase separation agent is added with respect to 100 parts by weight of the polyamic acid solution, and the mixture is stirred to obtain a uniform and transparent composition. obtain.

  The obtained composition is applied onto the ground pattern 21 using a coating machine. The N-methyl-2-pyrrolidone is then evaporated by heating the composition at 110 ° C. for 3 minutes. In this way, a polyamic acid film is formed on the ground pattern 21.

  Next, the laminate including the polyamic acid film is placed in a pressure vessel, and the atmosphere in the pressure vessel is adjusted to 25 ° C. and 25 MPa. Then, while maintaining the pressure in the pressure vessel at 25 MPa, carbon dioxide is continuously supplied into the pressure vessel at a flow rate (gas flow rate) of about 15 L / min for 5 hours, and the atmosphere in the pressure vessel Is discharged. Thereby, a porous polyamic acid film is obtained.

  Subsequently, the laminate including the porous polyamic acid film is taken out from the pressure vessel, and the taken-out laminate is put into a vacuum oven. In this state, the pressure in the vacuum oven is reduced to 5 Torr or less, and the temperature in the vacuum oven is increased to 340 ° C. in 60 minutes. Thereafter, the polyamic acid is converted into polyimide by maintaining the pressure in the vacuum oven at 5 Torr or less and the temperature in the vacuum oven at 340 ° C. for 10 minutes. In this manner, the dielectric layer 10 made of porous polyimide is formed on the ground pattern 21.

(4) Other Manufacturing Method of Antenna Substrate 100 In the example of FIG. 2, the antenna substrate 100 is manufactured by applying a polyimide precursor on the ground pattern 21 and generating porous polyimide.

  However, the present invention is not limited to this, and the antenna substrate unit 100 may be manufactured as follows. FIG. 4 is a schematic view showing another manufacturing method of the antenna substrate unit 100 of FIG. 4A to 4E, cross-sectional views corresponding to the cross-sectional view taken along the line AA of FIG. 1A are shown.

  First, as shown in FIG. 4A, a sheet member made of a resin porous material is prepared as the dielectric layer 10. As the porous material of this example, ePTFE (expanded polytetrafluoroethylene) is used. ePTFE has continuous pores (open cell structure). The average pore diameter of ePTFE is, for example, 0.05 μm or more and 1.0 μm or less.

  Also in this example, the thickness of the dielectric layer 10 is, for example, 20 μm or more and 150 μm or less, preferably 25 μm or more and 125 μm or less, and more preferably 50 μm or more and 100 μm or less.

  Next, a seed layer made of a laminated film of chromium and copper is formed on the upper and lower surfaces of the dielectric layer 10 by, for example, sputtering. The seed layer may be formed by electroless plating. Thereafter, as shown in FIG. 4B, a conductor layer 11x made of, for example, copper is formed on the upper surface of the dielectric layer 10 by electrolytic plating using a plating solution such as copper sulfate on the entire seed layer. Similarly, a conductor layer 211 x made of, for example, copper is formed on the lower surface of the dielectric layer 10. In FIG. 4B, illustration of the seed layer is omitted.

  Next, as shown in FIG. 4C, the conductor layers 11x and 211x and a partial region of the seed layer are etched by a method similar to the etching performed in the step of FIG. In this way, the antenna pattern 11 is formed on the upper surface of the dielectric layer 10 by the subtractive method, and the predetermined conductor pattern 211 is formed on the lower surface of the dielectric layer 10. In the conductor pattern 211, a slot 21s is formed in a partial region facing the central portion of the antenna pattern 11 with the dielectric layer 10 interposed therebetween.

  Next, as shown in FIG. 4D, the conductive pattern 211 formed on the lower surface of the dielectric layer 10 is formed on the first insulating layer 20 in FIG. It joins on the ground pattern 21 formed on the upper surface. Thereby, as shown in FIG.4 (e), the antenna board | substrate part 100 is completed.

  In the antenna substrate portion 100 of FIG. 4E, the conductor pattern 211, the bonding member 90, and the ground pattern 21 function as a ground conductor layer. As the joining member 90, a conductive adhesive or a solder paste can be used.

  ePTFE has higher water repellency than other resins such as polyimide. Therefore, even when the etching solution enters the continuous hole of ePTFE during the etching for forming the antenna pattern 11 and the ground pattern 21, the etching solution is prevented from remaining in the continuous hole.

(5) One manufacturing example of the three-layer base material 20x in FIG. 2 (a) When the first insulating layer 20 of the three-layer base material 20x in FIG. 2 (a) is made of the same material as the dielectric layer 10 May produce the three-layer base material 20x as follows.

  FIG. 5 is a schematic cross-sectional view showing a method for manufacturing the three-layer base material 20x of FIG. First, as shown to Fig.5 (a), copper foil is prepared as the conductor layer 21x.

  Next, as shown in FIG. 5B, a first insulating layer 20 made of a porous resin is formed on one surface of the conductor layer 21x by the same method as the method of forming the dielectric layer 10 described above.

  Next, as shown in FIG. 5C, a seed layer is formed on the first insulating layer 20, and a conductor layer 22x made of copper is formed on the seed layer by electrolytic plating. In FIG. 5C, illustration of the seed layer is omitted. In this way, a three-layer base material 20x composed of the first insulating layer 20 and the two conductor layers 21x and 22x can be obtained without using a bonding material such as an adhesive.

(6) Effect In the RF module substrate 1A, the dielectric layer 10 made of porous resin is used, so that the relative dielectric constant of the dielectric layer 10 at a frequency of 1 GHz is set to 2.00 or less. Is done. Thereby, radio wave radiation efficiency and reception efficiency in the RF module 1 are improved. In addition, the frequency band of radio waves that can be emitted and received by the RF module 1 is expanded.

  Furthermore, by using the dielectric layer 10 formed of a porous resin, the relative permittivity of the region between the antenna pattern 11 and the ground pattern 21 can be easily reduced without using a complicated configuration. it can.

  As a result, the antenna characteristics can be improved with a simple configuration, and the RF module substrate 1A can be easily manufactured.

  The relative dielectric constant of the resin is lower than that of other materials such as glass and ceramic. Therefore, the relative dielectric constant of the dielectric layer 10 is sufficiently reduced.

  In the RF module substrate 1A, the antenna pattern 11 is formed on the upper surface of the dielectric layer 10 without using a bonding material such as an adhesive. Similarly, the ground pattern 21 is formed on the lower surface of the dielectric layer 10 without using a bonding material such as an adhesive. This prevents an increase in the relative dielectric constant of the region between the antenna pattern 11 and the ground pattern 21 due to the bonding material.

(7) Other Embodiments (7-a) In the above embodiments, the antenna pattern 11 is formed by the subtractive method. However, the antenna pattern 11 may be formed by the semi-additive method. .

  In this case, for example, a seed layer made of a laminated film of chromium and copper is formed on the upper surface of the dielectric layer 10 in FIG. The seed layer is not limited to a laminated film of chromium and copper, but may be a single layer film of chromium, for example. The seed layer may be formed by electroless plating. Thereafter, a resist film is formed on the seed layer with a photosensitive dry film resist or the like, and the resist film is exposed with a predetermined pattern.

  Subsequently, the exposed resist film is developed using a developer such as sodium carbonate to form a plating resist on the seed layer.

  Next, a conductor layer made of, for example, copper is formed on the seed layer by electrolytic plating using a plating solution such as copper sulfate, except for the plating resist region.

  Next, the plating resist is removed with a stripping solution such as sodium hydroxide, and the exposed portion of the seed layer is removed by etching using an etching solution such as ferric chloride. As a result, the antenna pattern 11 including the conductor layer and the seed layer is formed on the upper surface of the dielectric layer 10.

  (7-b) The material of the antenna pattern 11, the ground pattern 21, the microstrip line 22a, the ground pattern 22b, the plurality of electrode patterns 31a, 31b, 31c, and the wiring pattern 31d is not limited to copper, but is gold, silver, aluminum Other metal materials such as phosphor bronze, copper-beryllium alloy, and iron-nickel alloy may be used. However, millimeter-wave band signals are transmitted to the antenna pattern 11, the ground pattern 21, and the microstrip line 22a. Therefore, it is preferable to use a metal material having an electric conductivity equal to or higher than that of copper for the antenna pattern 11, the ground pattern 21, and the microstrip line 22a.

  (7-c) In the above embodiment, the antenna pattern 11, the ground pattern 21, the microstrip line 22a, the ground pattern 22b, the plurality of electrode patterns 31a, and the wiring pattern 31d are formed by electrolytic plating. Instead, the antenna pattern 11, the ground pattern 21, the microstrip line 22a, the ground pattern 22b, the plurality of electrode patterns 31a, and the wiring pattern 31d may be formed by other methods. In this case, the seed layer may not be formed.

  (7-d) In the above embodiment, a porous resin is used as the porous material of the dielectric layer 10. However, the porous material is not limited to the porous resin, but may be porous glass or ceramic whose dielectric constant of the dielectric layer 10 at a frequency of 1 GHz is 2.00 or less. It may be used.

  In the above embodiment, a liquid crystal polymer or a porous resin is used as a material for the first insulating layer 20 and the second insulating layer 30. However, the material of the first insulating layer 20 and the second insulating layer 30 is not limited to this, and glass, ceramic, or the like may be used instead of the liquid crystal polymer or the porous resin. Alternatively, porous glass or ceramic may be used.

  (7-e) In the above embodiment, the antenna pattern 11 has a square shape. However, the antenna pattern 11 may have other shapes such as a circular shape, a rectangular shape, or a belt shape.

  In the above embodiment, the slot 21s of the ground pattern 21 has a rectangular shape. Not limited to this, the slot 21s may have other shapes such as a circular shape, a rectangular shape, or a belt shape.

(8) Correspondence between each component of claim and each part of embodiment The following describes an example of the correspondence between each component of the claim and each part of the embodiment. It is not limited.

  In the above embodiment, the RF module substrate 1A is an example of a radio frequency module substrate, the first insulating layer 20 is an example of a first insulating layer, and the upper surface of the first insulating layer 20 is the first one. 1 is an example of a surface, the lower surface of the first insulating layer 20 is an example of a second surface, and the slot 21s is an example of an opening.

  Also, the ground pattern 21 in FIGS. 1 to 3 and the laminate composed of the conductor pattern 211, the bonding member 90, and the ground pattern 21 in FIG. 4E are examples of the ground conductor layer, and the dielectric layer 10 is a dielectric. The antenna pattern 11 is an example of an antenna element, the microstrip line 22a is an example of a conductor pattern, and the second insulating layer 30 is an example of a second insulating layer.

  Further, RFIC 1B is an example of an electronic component, mounting area 1BA is an example of a mounting area, power terminal 50a is an example of a power terminal, ground terminal 50b is an example of a ground terminal, and external terminal 50c is an external terminal. It is an example.

  The electrode terminal 40a is an example of the first terminal, the electrode terminal 40b is an example of the second terminal, the electrode terminal 40c is an example of the third terminal, and the wiring pattern 31d is an example of the wiring pattern. is there.

  As each constituent element in the claims, various other elements having configurations or functions described in the claims can be used.

(9) Example and Comparative Example The antenna characteristics of the sample of Example 1 and Comparative Examples 1 to 6 were evaluated by simulation. First, the structure of the sample of Example 1 and Comparative Examples 1-6 is demonstrated.

(9-a) Example 1
The sample of Example 1 has the same configuration as the antenna substrate unit 100 of FIGS. 1 and 2 (e). In the sample of Example 1, it is assumed that the dielectric layer 10 is made of a porous resin. The thickness of the dielectric layer 10 is set to 100 μm. The relative dielectric constant of the dielectric layer 10 at a frequency of 1 GHz is set to 1.50, and the dielectric loss tangent is set to 0.003.

  The thickness of the first insulating layer 20 is set to 100 μm. The relative dielectric constant of the first insulating layer 20 at a frequency of 1 GHz is set to 3.50, and the dielectric loss tangent is set to 0.

  Further, each of the antenna pattern 11, the ground pattern 21, and the microstrip line 22a is made of copper having a thickness of 10 μm.

  The length AL (FIG. 1A) of one side of the antenna pattern 11 is set to 1.76 mm. The length SL (FIG. 1 (a)) of the slot 21s in the ground pattern 21 is set to 0.65 mm, and the width SW (FIG. 1 (a)) of the slot 21s is set to 0.2 mm. The width MW (FIG. 1A) of the microstrip line 22a is set to 200 μm, and the characteristic impedance of the microstrip line 22a is set to 50Ω. Further, in the extending direction of the microstrip line 22a, the distance d1 (FIG. 1 (a)) from the open end of the microstrip line 22a arranged so as to overlap the antenna pattern 11 to the center of the slot 21s is set to 0.65 mm. Is done.

(9-b) Comparative Example 1
The sample of Comparative Example 1 has the same configuration as the sample of Example 1 except for the following points. In the sample of Comparative Example 1, the dielectric constant of the dielectric layer 10 at a frequency of 1 GHz is set to 3.50, and the dielectric loss tangent is set to 0.002. The length AL (FIG. 1A) of one side of the antenna pattern 11 is set to 1.15 mm. The length SL (FIG. 1A) of the slot 21s in the ground pattern 21 is set to 0.5 mm.

(9-c) Comparative Example 2
The sample of Comparative Example 2 has the same configuration as the sample of Example 1 except for the following points. In the sample of Comparative Example 2, the relative dielectric constant of the dielectric layer 10 at a frequency of 1 GHz is set to 9.50, and the dielectric loss tangent is set to 0.0005. Also, the length AL (FIG. 1A) of one side of the antenna pattern 11 is set to 0.707 mm. The length SL (FIG. 1A) of the slot 21s in the ground pattern 21 is set to 0.3 mm.

(9-d) Comparative Example 3
The sample of Comparative Example 3 has the same configuration as the sample of Example 1 except for the following points. FIG. 6 is a schematic diagram for explaining the configuration of the sample of Comparative Example 3.

  As shown in FIG. 6, in the sample of Comparative Example 3, an adhesive layer 71 is provided between the dielectric layer 10 and the ground pattern 21.

  The dielectric layer 10 is made of a porous resin. In this example, the thickness t1 of the dielectric layer 10 is set to 85 μm. On the other hand, the thickness t2 of the adhesive layer 71 is set to 15 μm. The relative dielectric constant of the adhesive layer 71 at a frequency of 1 GHz is set to 3.50, and the dielectric loss tangent is set to 0.02. The length AL (FIG. 1A) of one side of the antenna pattern 11 is set to 1.69 mm. The length SL (FIG. 1A) of the slot 21s in the ground pattern 21 is set to 0.65 mm.

(9-e) Comparative Example 4
The sample of Comparative Example 4 has the same configuration as the sample of Comparative Example 3 except for the following points. In the sample of Comparative Example 4, the thickness t1 of the dielectric layer 10 is set to 70 μm. On the other hand, the thickness t2 of the adhesive layer 71 is set to 30 μm. The length AL (FIG. 1A) of one side of the antenna pattern 11 is set to 1.64 mm. The length SL (FIG. 1A) of the slot 21s in the ground pattern 21 is set to 0.6 mm.

(9-f) Comparative Example 5
The sample of Comparative Example 5 has the same configuration as the sample of Example 1 except for the following points. FIG. 7 is a schematic diagram for explaining a configuration of a sample of Comparative Example 5.

  As shown in FIG. 7, in the sample of Comparative Example 5, an adhesive layer 71 is provided between the dielectric layer 10 and the ground pattern 21, and an adhesive is provided between the dielectric layer 10 and the antenna pattern 11. A layer 72 is provided.

  The dielectric layer 10 is made of a porous resin. In this example, the thickness t1 of the dielectric layer 10 is set to 70 μm. On the other hand, the thicknesses t2 and t3 of the adhesive layers 71 and 72 are set to 15 μm, respectively. The relative dielectric constants of the adhesive layers 71 and 72 at a frequency of 1 GHz are set to 3.50, and the dielectric loss tangent is set to 0.02. The length AL (FIG. 1A) of one side of the antenna pattern 11 is set to 1.59 mm. The length SL (FIG. 1A) of the slot 21s in the ground pattern 21 is set to 0.6 mm.

(9-g) Comparative Example 6
The sample of Comparative Example 6 has the same configuration as the sample of Comparative Example 5 except for the following points. In the sample of Comparative Example 6, the thickness t1 of the dielectric layer 10 is set to 40 μm. On the other hand, the thicknesses t2 and t3 of the adhesive layers 71 and 72 are set to 30 μm, respectively. The length AL (FIG. 1A) of one side of the antenna pattern 11 is set to 1.42 mm. The length SL (FIG. 1A) of the slot 21s in the ground pattern 21 is set to 0.55 mm.

  As described above, in the samples of Example 1 and Comparative Examples 1 to 6, the length AL of one side in the antenna pattern 11 and the length SL of the slot 21s in the ground pattern 21 are different from each other. Table 1 below shows a list of the length AL and the length SL in the samples of Example 1 and Comparative Examples 1 to 6.

(9-h) Evaluation With respect to the samples of Example 1 and Comparative Examples 1 to 6, when high frequency power of a frequency of 60 GHz is supplied to the microstrip line 22a, the H plane when radio waves are radiated from the antenna pattern 11 ( In this example, the radiation pattern in a plane perpendicular to the axis of the microstrip line 22a and including the central portion of the antenna pattern 11 is obtained by simulation. For the simulation, software called Microwave Studio manufactured by Computer Simulation Technology was used.

  FIG. 8 is a diagram showing simulation results for the samples of Example 1 and Comparative Examples 1 and 2. FIG. In FIG. 8, the vertical axis indicates the absolute gain of the radio wave at a position 1 m away from the center of the antenna pattern 11, and the horizontal axis indicates the angle on the H plane with respect to the axis orthogonal to the center of the antenna pattern 11.

  In FIG. 8, a thick solid line L1, a thick alternate long and short dash line L11, and a thick broken line L12 indicate simulation results for the samples of Example 1 and Comparative Examples 1 and 2, respectively.

  According to FIG. 8, the maximum value of the absolute gain of the radio wave radiated from the sample of Example 1 is about 6.5 dB. On the other hand, the maximum value of the absolute gain of the radio wave radiated from the sample of Comparative Example 1 is about 3.5 dB, and the maximum value of the absolute gain of the radio wave radiated from the sample of Comparative Example 2 is about 2.5 dB.

  The absolute gain of the radio wave radiated from the sample of Example 1 is larger than the absolute gain of the radio wave radiated from the samples of Comparative Examples 1 and 2 in the range of about −70 ° to about 70 °.

  From these, it can be seen that the antenna substrate portion 100 including the dielectric layer 10 having a low relative dielectric constant at a frequency of 1 GHz has higher radiation characteristics. As a result, it has been clarified that the radiation characteristics of the antenna substrate 100 are sufficiently improved by using the dielectric layer 10 having a relative dielectric constant of 2.00 or less at a frequency of 1 GHz.

  FIG. 9 is a diagram showing simulation results for the samples of Example 1 and Comparative Examples 3 and 4. FIG. Also in FIG. 9, the vertical axis represents the absolute gain of the radio wave at a position 1 m away from the center of the antenna pattern 11, and the horizontal axis represents the angle on the H plane with respect to the axis orthogonal to the center of the antenna pattern 11.

  In FIG. 9, a thick solid line L1, a thick alternate long and short dash line L21, and a thick broken line L22 indicate simulation results for the samples of Example 1 and Comparative Examples 3 and 4, respectively.

  According to FIG. 9, the maximum value of the absolute gain of the radio wave radiated from the sample of Example 1 is about 6.5 dB. On the other hand, the maximum absolute gain of the radio wave radiated from the sample of Comparative Example 3 is about 5.8 dB, and the maximum absolute gain of the radio wave radiated from the sample of Comparative Example 4 is about 5.5 dB.

  Further, the absolute gain of the radio wave radiated from the sample of Example 1 is larger than the absolute gain of the radio wave radiated from the sample of Comparative Examples 3 and 4 in the range of about −70 ° to about 70 °.

  From these, it can be seen that the antenna substrate portion 100 having a smaller thickness t2 of the adhesive layer 71 provided between the dielectric layer 10 and the ground pattern 21 has higher radiation characteristics. As a result, it has been clarified that the radiation characteristic of the antenna substrate 100 is sufficiently improved by not providing the adhesive layer 71 between the dielectric layer 10 and the ground pattern 21.

  FIG. 10 is a diagram showing simulation results for the samples of Example 1 and Comparative Examples 5 and 6. FIG. Also in FIG. 10, the vertical axis indicates the absolute gain of the radio wave at a position 1 m away from the center of the antenna pattern 11, and the horizontal axis indicates the angle on the H plane with respect to the axis orthogonal to the center of the antenna pattern 11.

  In FIG. 10, a thick solid line L1, a thick alternate long and short dash line L31, and a thick broken line L32 show the simulation results for the samples of Example 1 and Comparative Examples 5 and 6, respectively.

  According to FIG. 10, the maximum value of the absolute gain of the radio wave radiated from the sample of Example 1 is about 6.5 dB. On the other hand, the maximum value of the absolute gain of the radio wave radiated from the sample of Comparative Example 5 is about 5.3 dB, and the maximum value of the absolute gain of the radio wave radiated from the sample of Comparative Example 6 is about 4.0 dB.

  The absolute gain of the radio wave radiated from the sample of Example 1 is larger than the absolute gain of the radio wave radiated from the samples of Comparative Examples 5 and 6 in the range of about −70 ° to about 70 °.

  Accordingly, the antenna has a small thickness t2 of the adhesive layer 71 provided between the dielectric layer 10 and the ground pattern 21, and a thickness t3 of the adhesive layer 72 provided between the dielectric layer 10 and the antenna pattern 11. It can be seen that the substrate unit 100 has higher radiation characteristics.

  As a result, it has been clarified that the radiation characteristics of the antenna substrate 100 are sufficiently improved by not providing the adhesive layers 71 and 72 between the dielectric layer 10 and the ground pattern 21.

  The present invention can be used for various electric devices or electronic devices.

1A Substrate for RF module 1B RFIC
1BA mounting area 10 dielectric layer 11 antenna pattern 20 first insulating layer 21, 22b ground pattern 21s slot 22a microstrip line 20h, 30h through hole 211 conductor pattern 30 second insulating layer 31a, 31b, 31c electrode pattern 31d wiring Pattern 40a, 40b, 40c Electrode terminal 41 Sealing resin 42 Cover insulating layer 43 Solder ball 50a Power terminal 50b Ground terminal 50c External terminal 90 Joining member 100 Antenna substrate part VC Copper

Claims (12)

A first insulating layer having first and second surfaces facing each other;
A grounding conductor layer formed on the first surface of the first insulating layer and having an opening;
A dielectric layer formed of a porous material on the ground conductor layer;
An antenna element formed on the dielectric layer so as to overlap the opening of the ground conductor layer;
A conductor pattern formed on the second surface of the first insulating layer so as to overlap the opening of the ground conductor layer;
The antenna element, the opening of the ground conductor layer, and the conductor pattern are arranged so that the antenna element is electromagnetically coupled to the conductor pattern through the opening when high-frequency power is supplied to the conductor pattern or when radio waves are received by the antenna element. Arranged to be combined,
A substrate for a radio frequency module, wherein a dielectric constant of the dielectric layer at a frequency of 1 GHz is 2.00 or less. The average pore diameter of the plurality of pores contained in the dielectric layer is 5 μm or less,
The printed circuit board according to claim 1, wherein a volume ratio of the plurality of holes per unit volume of the dielectric layer is 40% or more. The printed circuit board according to claim 1, wherein the porous material is made of a porous resin. The printed circuit board according to claim 3, wherein the resin is polyimide or polyetherimide. The radio frequency module substrate according to any one of claims 1 to 4, wherein a dielectric loss tangent of the dielectric layer at a frequency of 1 GHz is 0.005 or less. A second insulating layer formed on the second surface of the first insulating layer so as to cover the conductor pattern;
The second insulating layer has a mounting region in which an electronic component having a power terminal and a ground terminal to which high-frequency power is output or input can be mounted.
In the mounting region of the second insulating layer, a first terminal electrically connected to the conductor pattern and connectable to a power terminal of the electronic component, and electrically connected to the ground conductor layer; The radio frequency module substrate according to claim 1, wherein a second terminal connectable to a ground terminal of the electronic component is formed. The electronic component further has an external terminal for input or output of an external signal or supply of a power supply voltage,
In the mounting region of the second insulating layer, a third terminal that can be connected to the external terminal of the electronic component is further formed,
The radio frequency module substrate according to claim 6, wherein a wiring pattern extending from the third terminal to the outside of the mounting region is formed on the second insulating layer. A step of forming a laminated structure including a conductor pattern, an insulating layer, a ground conductor layer having an opening, a dielectric layer made of a porous material, and an antenna element in this order;
The antenna element, the opening of the ground conductor layer, and the conductor pattern are arranged so that the antenna element is electromagnetically coupled to the conductor pattern through the opening when high-frequency power is supplied to the conductor pattern or when radio waves are received by the antenna element. Arranged to be combined,
The manufacturing method of the board | substrate for radio frequency modules whose relative dielectric constant of the said dielectric material layer in the frequency of 1 GHz is 2.00 or less. The step of forming the laminated structure includes
Providing the insulating layer having first and second surfaces facing each other;
Forming the ground conductor layer on the first surface of the insulating layer;
Forming the conductor pattern on the second surface of the insulating layer;
Forming the dielectric layer on the ground conductor layer;
Forming the antenna element on the dielectric layer,
The step of forming the dielectric layer includes
Applying a composition comprising a flowable resin and a phase separation agent for phase separation to the cured resin on the ground conductor layer;
Forming a resin film having a microphase separation structure on the ground conductor layer by curing the resin;
The method of manufacturing the board | substrate for radio frequency modules of Claim 8 including the process of removing the said phase separation agent from the said resin film. The step of removing the phase separation agent from the resin membrane,
The manufacturing method of the board | substrate for radio frequency modules of Claim 9 including the process of extracting the said phase separation agent from the said resin film by impregnating the said resin film with a solvent. The resin is a polyamic acid;
The step of forming the dielectric layer includes
The method for manufacturing a substrate for a radio frequency module according to claim 9 or 10, further comprising a step of converting polyamic acid into polyimide after the step of removing the phase separation agent from the resin film. The step of forming the laminated structure includes
Providing the insulating layer having first and second surfaces facing each other;
Forming a first conductor layer having an opening on the first surface of the insulating layer;
Forming the conductor pattern on the second surface of the insulating layer;
Providing the dielectric layer having third and fourth surfaces facing each other;
Forming a second conductor layer having an opening on the third surface of the dielectric layer;
Forming the antenna element on the fourth surface of the dielectric layer;
The method for manufacturing a substrate for a radio frequency module according to claim 8, further comprising a step of forming the ground conductor layer by bonding the first conductor layer and the second conductor layer.

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