Patent Application
20240275034
The present disclosure relates to an antenna module, a communication device mounting the same, a dielectric substrate, and a manufacturing method of the antenna module, and more specifically, relates to a technique for preventing deformation of a dielectric substrate during the manufacturing process of the antenna module capable of radiating radio waves in two directions.
A configuration of an antenna module includes radiating elements disposed at flat portions in different normal directions from each other in a bent dielectric substrate.
In the configuration of the antenna module described above, in a case where the dielectric substrate is formed of a resin, a dielectric layer on which the resin material is laminated is bent from a flat state at room temperature, and then heat-treated and fired to be pressure-bonded and fixed.
Here, when the resin material is bent at room temperature, a residual stress having a non-uniform distribution is generated in a bending portion. In this state, when the dielectric substrate is heated due to an increase in ambient temperature in actual use or an increase in temperature of the attached IC circuit, the residual stress is released as the temperature rises due to the influence of residual stress and deformation occurs. As a result, the bending angle of the bending portion may be wider than the desired angle. Then, since the direction of the radiated radio waves is shifted from the design direction, this can be a factor in a deterioration of the antenna characteristics such as directivity.
The present disclosure is made to solve such a problem by, for example, suppressing deterioration in antenna characteristics due to deformation of a dielectric substrate in a manufacturing process in an antenna module.
An antenna module according to a first aspect of the present disclosure includes a dielectric substrate and a radiating element disposed on the dielectric substrate. The dielectric substrate includes a first flat portion and a second flat with a normal direction different from a normal direction of the first flat portion, and a bending portion that connects the first flat portion and the second flat portion. The bending portion has a bending region having a curvature. The first flat portion and the second flat portion have a straight region having no curvature. The radiating element is disposed in the first flat portion. In a Raman spectrum obtained by Raman scattering spectroscopic analysis of a cross section of the dielectric substrate, a wave number difference indicating a difference between a wave number which is a mode value in the straight region and a wave number which is a mode value in the bending region is 0.1 cm−1 or more.
A manufacturing method of an antenna module according to a second aspect of the present disclosure includes (disposing a radiating element on a dielectric substrate, bending the dielectric substrate, and performing an annealing treatment in a state where the dielectric substrate is held in a holding tool configured to fix a shape of the bent dielectric substrate.
In the antenna module and the manufacturing method thereof according to the present disclosure, after the dielectric substrate is bent, the annealing treatment is applied in a state where the dielectric substrate is held in the holding tool. Therefore, in the results of the Raman scattering spectroscopic analysis of the cross section of the dielectric substrate, the difference (wave number difference) between the wave number which is the mode value of Raman light (Raman spectrum) in the bending region and the wave number which is the mode value of Raman light in the straight region is 0.1 cm−1 or more. That is, the stress difference of the residual stress in the bending portion is reduced. Therefore, deformation of the dielectric substrate in the manufacturing process is suppressed, so that deterioration in antenna characteristics can be suppressed.
Hereinafter, exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. The same or corresponding portions in the drawings are denoted by the same reference numerals, and the description is not repeated.
Referring to
The antenna device 120 includes a dielectric substrate 105 having two flat portions 130A and 130B. At least one radiating element is disposed in each flat portion of the dielectric substrate 105. More specifically, m1 radiating elements 121A (first radiating elements) are disposed in the flat portion 130A, and n1 radiating elements (second radiating elements) are disposed in the flat portion 130B (m1≥1, n1≥1). The number m1 of the radiating elements 121A disposed in the flat portion 130A may be the same as or different from the number n1 of the radiating elements 121B disposed in the flat portion 130B.
In
The RFIC 110 includes switches 111A to 111H, 113A to 113H, 117A, and 117B, power amplifiers 112AT to 112HT, low noise amplifiers 112AR to 112HR, attenuators 114A to 114H, phase shifters 115A to 115H, signal synthesizer/distributors 116A and 116B, mixers 118A and 118B, and amplifier circuits 119A and 119B. Of these, the configuration of the switches 111A to 111D, 113A to 113D, and 117A, the power amplifiers 112AT to 112DT, the low noise amplifiers 112AR to 112DR, the attenuators 114A to 114D, the phase shifters 115A to 115D, the signal synthesizer/distributor 116A, the mixer 118A, and the amplifier circuit 119A is a circuit for a high frequency signal radiated from the radiating element 121A of the flat portion 130A. In addition, the configuration of the switches 111E to 111H, 113E to 113H, and 117B, the power amplifiers 112ET to 112HT, the low noise amplifiers 112ER to 112HR, the attenuators 114E to 114H, the phase shifters 115E to 115H, the signal synthesizer/distributor 116B, the mixer 118B, and the amplifier circuit 119B is a circuit for a high frequency signal radiated from the radiating element 121B of the flat portion 130B.
In a case where the high frequency signal is transmitted, the switches 111A to 111H and 113A to 113H are switched to the power amplifier 112AT to 112HT side, and the switches 117A and 117B are connected to the transmission side amplifiers of the amplifier circuits 119A and 119B. In a case where the high frequency signal is received, the switches 111A to 111H and 113A to 113H are switched to the low noise amplifier 112AR to 112HR side, and the switches 117A and 117B are connected to the receiving side amplifiers of the amplifier circuits 119A and 119B.
The signal transmitted from the BBIC 200 is amplified by the amplifier circuits 119A and 119B and up-converted by the mixers 118A and 118B. The transmission signal, which is an up-converted high frequency signal, is divided into four waves by the signal synthesizer/distributors 116A and 116B, passes through the corresponding signal paths, and is fed to different radiating elements 121A and 121B, respectively. By individually adjusting the phase shift degrees of the phase shifters 115A to 115H disposed in each signal path, the directivity of the radio wave output from the radiating element of each flat portion can be adjusted.
The received signal, which is the high frequency signal received by each of the radiating elements 121A and 121B, is transmitted to the RFIC 110, passes through four different signal paths, and is multiplexed in the signal synthesizer/distributors 116A and 116B. The multiplexed received signal is down-converted by the mixers 118A and 118B, amplified by the amplifier circuits 119A and 119B, and transmitted to the BBIC 200.
The RFIC 110 is formed as, for example, a one-chip integrated circuit component including the above-described circuit configuration. Alternatively, the device (switch, power amplifier, low noise amplifier, attenuator, and phase shifter) corresponding to each of the radiating elements 121A and 121B in the RFIC 110 may be formed as a one-chip integrated circuit component for each of the corresponding radiating elements.
Next, the details of the configuration of the antenna module 100 according to the present exemplary embodiment will be described with reference to
Referring to
For example, the dielectric substrate 105 is a multilayer resin substrate formed by laminating a plurality of resin layers made of a resin such as epoxy or polyimide, a multilayer resin substrate formed by laminating a plurality of resin layers made of liquid crystal polymer (LCP) having a lower dielectric constant, and a multilayer resin substrate formed by laminating a plurality of resin layers made of fluorine resin. The dielectric substrate 105 need not necessarily have a multilayer structure, and may be a single layer substrate.
In the antenna device 120 of the antenna module 100, the dielectric substrate 105 has a substantially L-shaped cross-sectional shape, and includes a flat plate-like flat portion 130A having the Z axis direction in
In the antenna module 100, four radiating elements are disposed in a row in the Y axis direction in each of the two flat portions 130A and 130B. In the following description, to make it easy to understand, an example in which the radiating elements 121A and 121B are disposed so as to be exposed on the surfaces of the flat portions 130A and 130B will be described, but the radiating elements 121A and 121B may be disposed inside the substrate of the flat portion 130A and 130B.
The flat portion 130A has a substantially rectangular shape, and four radiating elements 121A are disposed in a row on the surface thereof. In addition, a system in package (SiP) module 125 having a built-in RFIC 110, a power module IC, and the like, and the connector 140 are connected to the lower surface side (the surface in the negative direction of the Z axis) of the flat portion 130A. The flat portion 130A is mounted on the mounting substrate 20 by connecting the connector 140 to a connector 145 disposed on the surface 21 of the mounting substrate 20. The flat portion 130A may be mounted on the mounting substrate 20 by solder connection.
The flat portion 130B is connected to the bending portion 135 bent from the flat portion 130A, and is disposed so that the surface on the inner side portion thereof (the surface in the negative direction of the X axis) faces the side surface 22 of the mounting substrate 20. The flat portion 130B has a configuration in which a plurality of notched portions 136 are formed on a substantially rectangular dielectric substrate, and the bending portion 135 is connected to the notched portions 136. In other words, at the portion of the flat portion 130B where the notched portion 136 is not formed, a protrusion portion 133 is formed that protrudes from the boundary portion 134 where the bending portion 135 and the flat portion 130B are connected in a direction toward the flat portion 130A (that is, the positive direction of Z axis) along the flat portion 130B. The position of the protruding end of the protrusion portion 133 is located in the positive direction of the Z axis with respect to the surface of the lower surface side (the side that faces the mounting substrate 20) of the flat portion 130A.
The flat portion 130B in the antenna module 100 of
The ground electrode GND is disposed on the inner layer of the surface that faces the mounting substrate 20 in the flat portions 130A and 130B and the bending portion 135. The high frequency signal is transmitted from the RFIC 110 in the SiP module 125 to the radiating element 121A of the flat portion 130A via the power supply wiring 170A. In addition, the high frequency signal is transmitted from the RFIC 110 to the radiating element 121B of the flat portion 130B via the power supply wiring 170B. The power supply wiring 170B is connected from the RFIC 110 to the radiating element 121B disposed in the flat portion 130B through the inside of each of the dielectric substrates of the flat portions 130A and 130B and the inside of the dielectric substrate of the bending portion 135.
As described above, in the antenna module in which the dielectric substrate is bent to form the two flat portions and radiates radio waves in two directions, residual stress is generated in the bending portion due to the bending of the dielectric substrate. In a case where ceramic is employed as the dielectric substrate, after the bending step, a heat treatment is applied to pressure-bonded and fire the ceramic. At this time, when there is residual stress in the bending portion, the residual stress is released when the bending portion is heated, and a force that tries to return to the shape before bending is generated. For example, in a case where the angle of the flat portion 130B with respect to the flat portion 130A in the bending process is set to 90° as illustrated in
When such deformation occurs due to heating, the radiation direction of the radio wave radiated from the radiating element 121B disposed on the flat portion 130B is shifted from the radiation direction at the time of design, and there is a possibility that antenna characteristics may deteriorate, such as deterioration of directivity and antenna gain, and interference with radio waves radiated from the radiating element 121A of the flat portion 130A.
In the present exemplary embodiment, in the manufacturing process of the antenna module, after the dielectric substrate is bent, the annealing treatment is applied in a state where the shape of the dielectric substrate is constrained, so that the residual stress at the bending portion is released while the shape of the dielectric substrate is maintained. As a result, even in a case where the heat treatment is applied in subsequent manufacturing steps, deformation due to the residual stress of the bending portion can be suppressed.
Next, a specific manufacturing process of the antenna module 100 according to the present exemplary embodiment will be described with reference to
First, in the step illustrated in
Next, in the step illustrated in
At the boundary portion between the portion which is the protrusion portion 133 and the portion which is the bending portion 135, a slit 150 that penetrates the dielectric substrate 105 in the thickness direction is formed by laser processing or router processing. The electrode 190 is not formed at the portion where the slit 150 is formed.
Thereafter, in the step illustrated in
In the step illustrated in
Next, in the step illustrated in
In the step illustrated in
As described above, after the dielectric substrate 105 is bent, the annealing treatment is applied in a state of constraining the dielectric substrate 105, so that the stress difference generated in the bending portion 135 is reduced and the stress distribution becomes uniform. Therefore, deformation of the bending portion 135 that occurs in the subsequent heat treatment can be suppressed. Therefore, the shift of the radiation direction of the radiating element 121B disposed in the flat portion 130B from the radiation direction at the time of design is reduced, so that deterioration in the antenna characteristics can be suppressed.
For example, in the example in which the annealing treatment is performed under the above conditions, the opening angle (return angle) of the bending portion 135 after the annealing treatment with respect to before the annealing treatment is less than 10°.
The stress distribution of the bending portion 135 can be confirmed by performing Raman scattering spectroscopic analysis. The Raman scattering spectroscopic analysis is a method of evaluating a material by using light having a different vibration (Raman scattered light) from the incident light that is generated according to the structure of the material when the material is irradiated with light. In a case where a stress distribution occurs in a material, the Raman scattered light generated by a change in the intermolecular structure of the material due to the difference in stress is shifted. Therefore, the state of the generated stress can be detected by detecting the wave number (reciprocal of the wavelength) at which the peak of the spectrum of the Raman scattered light occurs.
In
In the straight region RG1, since the residual stress due to the bending step is not generated, the stress distribution before and after the annealing treatment does not change significantly as illustrated in
Here, when the absolute value of the difference between the wave numbers which is the mode values of the intensity in the Raman spectrum is defined as a “wave number difference” WD, the wave number difference before and after the annealing treatment in the straight region RG1 is approximately 0.05 cm−1. The mode value of the intensity in the Raman spectrum indicates the wave number which is a peak in the wave number distribution of the Raman spectrum illustrated in
The wave numbers of the straight region RG1 and the bending region RG2 before the annealing treatment are substantially the same (zero wave number difference), but after the annealing treatment, the wave number difference between the straight region RG1 and the bending region RG2 is 0.3 cm−1. As described above, in the bending region RG2, where the residual stress is generated in the bending step, since the residual stress is relaxed by the annealing treatment, deformation caused by the subsequent heat treatment can be suppressed. At this time, as a result, the wave number which is the mode value in the Raman spectrum is shifted compared to the straight region RG1, and the wave number difference between the straight region RG1 and the bending region RG2 increases.
As illustrated in
As described above, although the shift direction of the wave number which is the mode value in the Raman spectrum is different, even in the case of the benzene ring, the residual stress in the bending region RG2 is relaxed by the annealing treatment, and the wave number difference between the straight region RG1 and the bending region RG2 after the annealing treatment is increased.
The reason why the shift direction of the wave number due to the relaxation of residual stress is different between the carbonyl group and the benzene ring will be described with reference to
In this state, when the dielectric substrate 105 is bent in the bending step, as illustrated in the upper stage of
On the other hand, the double coupling between carbon and oxygen of the carbonyl group exists in a state inclined in the V direction. Therefore, in the bending step, the compressive stress acts on the carbonyl group. As a result, before the annealing treatment, the Raman spectrum is shifted to the high wave number side from a state where no stress acts due to the influence of the residual stress. When the annealing treatment is applied, the intermolecular coupling between carbon and oxygen extends in the V direction where the thermal expansion coefficient is large, and the compressive stress is relaxed. As a result, it is considered that the Raman spectrum after the annealing treatment shifts from the state before the annealing treatment to the low wave number side.
As described above, the shift direction of the Raman spectrum, when stress is relaxed by the annealing treatment, differs depending on the arrangement structure of the molecules constituting the substrate material, but as the residual stress is relaxed by the annealing treatment, the wave number difference between the straight region where the influence of residual stress is small and the bending region where the influence of residual stress is large increases.
As described above, in the manufacturing process of the antenna module that can radiate radio waves in two different directions by bending the dielectric substrate, by performing annealing treatment in a state where the shape of the dielectric substrate after bending is constrained and uniformizing the stress distribution generated in the bending portion, deformation of the dielectric substrate during the subsequent heat treatment can be suppressed. At this time, by setting the wave number difference between the straight region and the bending region in the stress distribution obtained by Raman scattering spectroscopic analysis of the bending portion to be 0.1 cm−1 or more by the annealing treatment, the deformation of the dielectric substrate can be suppressed.
In the above description, the antenna module in which the radiating element is disposed on the dielectric substrate is described, but the features of the present disclosure can also be applied to a single dielectric substrate having a bending portion on which a ground electrode, power supply wiring, and the like are disposed for supplying a high frequency signal to a radiating element placed on a separate substrate or housing. In this case, the deformation of the dielectric substrate can be suppressed by setting the wave number difference between the straight region and the bending region in the dielectric substrate to be 0.1 cm−1 or more.
The exemplary embodiment disclosed herein is required to be considered to be an example and not restrictive in all respects. The scope of the present disclosure is indicated by the claims rather than the description of the above-described exemplary embodiment, and is intended to include all changes within the meaning and range of equivalents to the claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-175678 | Oct 2021 | JP | national |
This application is a continuation of international application no. PCT/JP2022/037406, filed Oct. 6, 2022, and which claims the benefit of priority to Japanese application no. 2021-175678, filed Oct. 27, 2021. The entire contents of both prior applications are hereby incorporated by reference in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2022/037406 | Oct 2022 | WO |
| Child | 18647185 | US |
