JP2014179935A - Mode converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mode converter corresponding to thinning.SOLUTION: The mode converter at least includes: a flexible board; a ground conductor layer formed on front and rear faces of the flexible board; a connecting part formed on the front face side of the flexible board; micropores formed from the front face of the flexible board to a desired depth; and pins, composed of a conductor filled in the micropores, connected to the connecting part.

Description

  The present invention relates to a mode converter, and more particularly to a technique suitable for use in a waveguide used for communication using a millimeter wave signal or the like.

  In recent years, high-speed and large-capacity communication of several G [bps] using the millimeter wave band has been proposed, and a part thereof is being realized. In particular, wireless communication devices that operate in the 60 [GHz] band are becoming more important. In Japan, a wide frequency band from 59 [GHz] to 66 [GHz] can be used with specific power saving, so that it is expected to be widely used in the consumer field. Realization of is an urgent need.

  Patent Document 1 discloses a millimeter wave module using a waveguide (post wall waveguide antenna) by a printed circuit board. As shown in FIGS. 1 to 7 of Patent Document 1, in this technique, a side wall (metal wall) of a conventional waveguide is replaced with a through hole group (post group) of a printed circuit board. As shown in FIGS. 1 to 7 of Patent Document 1, a wireless communication IC (CMOS-IC) is mounted on a PWA, and wireless communication ICs (specifications of Patent Document 1 are described by wire bonding or bump connection). In the document, the millimeter wave signal output from the semiconductor chip 4 (hereinafter the same) is transmitted through a transmission line (indicated as a microstrip, coplanar, strip, or other line 24) by a planar circuit, and then a planar circuit / waveguide. It is finally led to the waveguide structure part (waveguide 2) through the conversion structure (center conductor 23 = pin). The center conductor (pin) 23 in Patent Document 1 is formed by forming a through hole in a printed board and copper plating the inner surface of the through hole.

  In a general high-frequency circuit, it is necessary to design so that impedance matching is obtained when the circuit A and the circuit B are connected. This means that the signal is transmitted without reflection at the connection point from the circuit A to the circuit B. That is, it is necessary to transmit the signal without reflection at the connection point of the planar circuit / transmission line as the circuit A and the waveguide as the circuit B. In the case of the conventional structure, by adjusting the pin length to a predetermined value in a predetermined frequency band, signal transmission with reduced reflection loss is realized to achieve impedance matching.

JP 2011-109438 A

R.Suga, et al. “Cost-Effective 60-GHz Antenna-Package With End-Fire Radiation from Open-Ended Post-Wall Waveguide for Wireless File-Transfer System,” 2011 IEEE MTT-S International Microwave Symposium, pp. 348 -351 T. Kai, et al., “A coaxial line to post-wall waveguide transition for a cost-effective transformer between a RF-device and a planar slot-array antenna in 60-GHz band,” IEICE Trans. COMMUN., E98 -B, no.5, pp. 1646-1653, May 2006.

  In recent years, there has been an increasing demand for mounting a mode converter on a portable terminal such as a mobile phone, and accordingly, there is a demand to reduce the size and thickness of the mode converter itself. For example, in order to reduce the size and thickness of the mode converter disclosed in Patent Document 1, it is necessary to make the substrate on which the waveguide is formed thinner. However, if the substrate is thinned, the substrate itself is easily deformed when an external force is applied. Then, stress is applied to the pin formed inside the micro hole, and the pin may be peeled off from the inner surface of the micro hole or the pin itself may be damaged. As a result, a desired high frequency signal cannot be injected. There was a problem.

  The present invention has been made in consideration of the above points, and an object of the present invention is to provide a mode converter that is reduced in size, particularly reduced in thickness, and has bending resistance corresponding to the reduction in thickness.

A mode converter according to claim 1 of the present invention includes a flexible substrate,
A ground conductor layer formed on one main surface and the other main surface of the flexible substrate;
A connecting portion formed on one main surface side of the flexible substrate;
Fine holes formed from one main surface of the flexible substrate to a desired depth;
A pin made of a conductor filled in the micropore and connected to the connecting portion;
It is characterized by having at least.

  According to the present invention, a flexible substrate, a ground conductor layer formed on one main surface and the other main surface of the flexible substrate, a connection portion formed on one main surface side of the flexible substrate, Thinner by providing at least a micro hole formed from one main surface of the flexible substrate to a desired depth and a pin made of a conductor filled in the micro hole and connected to the connection portion. Even when the flexible substrate is deformed by an external force or the like in the formed waveguide, since the pins are formed by the conductor filled in the fine holes, the stress resistance due to the deformation of the flexible substrate is improved. As a result, even if the flexible substrate is deformed, it is possible to prevent a problem that peeling occurs between the pin and the inner surface of the fine hole, or the pin itself is damaged, and the injection of a desired high-frequency signal in the mode converter is maintained. Can do.

  The mode converter according to claim 2 of the present invention is characterized in that the flexible substrate has a thickness of 300 μm or less.

  A mode converter according to claim 3 of the present invention is characterized in that the conductor is a porous body.

  The mode converter which concerns on Claim 4 of this invention is characterized by the said conductor being formed by heat-processing an electrically conductive paste.

  According to the present invention, even when the flexible substrate is deformed by an external force, since the pins are formed by the conductor filled in the fine holes, the stress resistance due to the deformation of the flexible substrate is improved. As a result, even if the flexible substrate is deformed, it is possible to prevent a problem that peeling occurs between the pin and the inner surface of the fine hole, or the pin itself is damaged, and the injection of a desired high-frequency signal in the mode converter is maintained. Can do.

It is a perspective view which shows the waveguide in one Embodiment of the mode converter which concerns on this invention. It is a front sectional view showing one embodiment of a mode converter concerning the present invention. It is a perspective view showing one embodiment of a mode converter concerning the present invention. It is a front sectional view showing a GRD via in one embodiment of a mode converter concerning the present invention. It is a schematic plan view which shows the conductor pillar in one Embodiment of the mode converter which concerns on this invention. It is a schematic cross section which shows the example of the pin in one Embodiment of the mode converter which concerns on this invention. It is a schematic cross section for showing a process in one embodiment of a mode converter concerning the present invention. It is a schematic cross section which shows the other example of the pin in one Embodiment of the mode converter which concerns on this invention. It is a schematic top view which shows the other example of the waveguide in one Embodiment of the mode converter which concerns on this invention. It is a perspective view which shows the other example of the waveguide in one Embodiment of the mode converter which concerns on this invention. It is a schematic top view which shows the other example of the waveguide in one Embodiment of the mode converter which concerns on this invention. It is a schematic top view which shows the other example of the waveguide in one Embodiment of the mode converter which concerns on this invention. It is a schematic top view which shows the other example of the waveguide in one Embodiment of the mode converter which concerns on this invention. It is a schematic cross section which shows the other example of the conductor pillar in one Embodiment of the mode converter which concerns on this invention. It is a schematic cross section which shows the other example of the conductor pillar in one Embodiment of the mode converter which concerns on this invention. 1 is a schematic cross-sectional view showing an example of a millimeter wave communication module in an embodiment of a mode converter according to the present invention. It is a schematic sectional side view which shows the other example of the millimeter wave communication module in one Embodiment of the mode converter which concerns on this invention. It is a perspective view which shows the other example of the pin in one Embodiment of the mode converter which concerns on this invention. It is a perspective view which shows the mode converter which performed the simulation as an experiment example. It is an expansion perspective view which shows the planar circuit in the mode converter which simulated as an experiment example. It is a graph which shows the result of having simulated the frequency band in the mode converter of FIG. It is an expansion perspective view which shows the other example of the planar circuit in the mode converter which performed the simulation as an experiment example. It is a graph which shows the result of having simulated the frequency band in the mode converter of FIG. It is a photograph which shows the longitudinal cross-section of the pin manufactured in one Embodiment of the mode converter which concerns on this invention.

  Hereinafter, a first embodiment of a mode converter according to the present invention will be described with reference to the drawings. The following embodiments are described by way of example in order to better understand the gist of the invention, and do not limit the present invention unless otherwise specified. In addition, in the drawings used in the following description, in order to make the features of the present invention easier to understand, the main part may be enlarged for convenience, and the dimensional ratios of the respective components are the same as the actual ones. Not necessarily. In addition, in order to make the features of the present invention easier to understand, some parts are omitted for convenience.

[Configuration of mode converter]
The configuration of the mode converter 100 according to the present embodiment will be described with reference to FIGS. 1 is a perspective view showing a mode converter 100, FIG. 2 is a cross-sectional view schematically showing the mode converter 100, FIG. 3 is an enlarged perspective view showing a connecting portion, and FIG. 4 is GND. FIG. 5 is a schematic plan view schematically showing the conductor pillar 114 that is a reflection portion. In the figure, reference numeral 100 denotes a mode converter.

  As shown in FIGS. 1 and 2, the mode converter 100 of the present embodiment includes a waveguide 110 having pins (conductor pins) 123 provided on a substrate (flexible substrate) 101, and an upper substrate (flexible substrate) 124. And a transmission path (planar circuit) 122 serving as a connection part for high-frequency signal propagation, and the substrate 101 and the substrate 124 are bonded to each other.

  The waveguide 110 is a conductor pillar that is a ground conductor layer (conductor film) 111, 112 provided on the front and back surfaces of the substrate 101, and a plurality of post (pillar) walls erected between the ground conductor layers 111, 112. 114, and functions as a path through which an electromagnetic wave signal radiated from the pin 123 propagates. On one end side of the waveguide 110, the ground conductor layers 111 and 112 and the conductor pillars 114 are not arranged, but are openings through which electromagnetic wave signals are radiated. The side opposite to the opening is a reflecting portion 110A.

  The substrate 101 can have a thickness of about 500 μm, or about 300 μm, 200 μm, or 100 μm. Here, “degree” means having a thickness width of ± 50 μm. The constituent material of the substrate 101 is not particularly limited, but examples of flexible flexible substrates include polyimide resin, PEN (polyethylene naphthalate), PET (polyethylene terephthalate), glass epoxy resin, and epoxy resin. A substrate (FR4) containing glass cloth (fiber) can be used, and for example, a liquid crystal polymer (LCP) can be used.

The ground conductor layers 111 and 112 are copper thin films or the like provided on the front and back surfaces of the substrate 101, and are provided on the entire surface of the substrate 101 excluding at least the peripheral region of the pin 123.
As shown in FIG. 1, the conductor pillar 114 has a cylindrical shape having the same diameter and is made of the same material as the ground conductor layers 111 and 112, and ends of the conductor pillar 114 are the ground conductor layer 111 and the ground conductor layer 112. And connected to. The plurality of conductor pillars 114 are arranged so as to be substantially rectangular except for one side which is a portion corresponding to the opening when the waveguide 110 is viewed in plan. The arrangement of the plurality of conductor pillars 114 is set so as not to reflect the high frequency signal oscillated from the pin 123 and leak outside. Specifically, when adjacent conductor pillars 114 are spaced apart, the center-to-center distance L is set to be smaller than twice the diameter d of the conductor pillars 114, as shown in FIG. . That is, the distance X between the re-adjacent positions of the conductor pillars 114 is set to be equal to or smaller than the diameter d of the conductor pillars 114. Further, none of the conductor pillars 114 are filled with a conductor. The cylindrical conductors forming the conductor pillars 114 are each made of a conductor film that is thinner than the ground conductor layers 111 and 112. In addition, the inside of the conductor pillar 114 can be filled with an insulator such as a resin or not filled at all.

  As shown in FIGS. 1 to 3, the mode converter 100 includes a pin 123 inserted into the waveguide 110 through an opening 111 a provided in the ground conductor layer 111 so as to be inherent in the substrate 101, and the pin 123. A planar circuit (transmission path) 122 connected to the outer base end portion and positioned outside the ground conductor film 111 is provided.

An upper substrate (substrate) 124 having a substantially uniform thickness is laminated on the ground conductor layer 111 and bonded through an adhesive layer 124a. The upper substrate 124 is provided with a through conductor 123A in a hole γ that penetrates the upper substrate 124 at the same position as the pin 123 in plan view. The outer end portion of the through conductor 123 </ b> A is a pin terminal (connection portion) 123 b located on the surface of the upper substrate 124, and is connected to one end side of the transmission path 122.
The upper substrate 124 is made of the same material as that of the substrate 101 and is, for example, a flexible substrate, and can have a thickness less than half that of the substrate 101, that is, a dimension less than the thickness of the pin 123.

A transmission path 122 as a connection portion is formed on the outer surface of the upper substrate 124. The transmission line 122 is provided so as to straddle at least the opening 111 a of the ground conductor layer 111, one end side is connected to the pin 123 via the pin terminal 123 b, and the other end side is a GSG pad (high frequency signal input terminal) 125 on the upper substrate 124. Connected to a microstrip line. As shown in FIG. 3, the GND pads 126 are spaced apart from both sides of the GSG pad 125 with respect to the transmission path 122 so as to be at both outer positions in the direction perpendicular to the extending direction of the transmission path 122 on the upper substrate 124. Arranged.

As shown in FIG. 3, the GND pad 126 is provided with GND vias 127 at both outer positions thereof, and the GND via 127 has the same configuration as the through conductor 123A. As shown in FIG. 4, the GND via 127 is provided so as to connect from the layer of the transmission path 122 on the upper substrate 124 to the layer of the ground conductor layer 111 on the surface of the substrate 124.

  As shown in FIG. 2, the pin 123 has a columnar shape having a diameter dimension H <b> 1, is in the substrate 101, and is, for example, about half of the substrate 101 so that the tip 123 a is not in contact with the conductor film 112. Thus, the length dimension H4 is set. The pin 123 is provided in the direction perpendicular to the surface of the ground conductor layers 111 and 112. As shown in FIGS. 2 and 3, on the base end side of the pin 123, a flange-like land 123 c made of the same material as the conductor film 111 is provided on the surface of the substrate 101 at the same level as the ground conductor layer 111. The An outer edge portion of the surface of the land 123c that has an annular shape in plan view is covered with the upper substrate 124 via an adhesive layer 124a. The base end side of the pin 123 is connected to the transmission line 122 via a through conductor 123A that is formed by extending the pin 123 toward the outside of the substrate 101.

  As shown in FIG. 3, the transmission path 122 extends on the surface of the upper substrate 124 that is substantially parallel to the ground conductor layer 111, and has a diameter dimension larger than that of the through conductor 123A at the outer end portion of the through conductor 123A. It is connected to a large pin terminal 123b. The transmission path 122 extends linearly from the pin terminal 123b to the GSG pad (high frequency signal input terminal) 125, and the width dimension thereof can be set equal to the diameter dimension of the through conductor 123A and the pin 123. The width dimension of the transmission path 122 can be appropriately adjusted as an input impedance matching unit, as will be described later.

On the transmission line 122, an open stub 122 b is provided on the side connected to the GSG pad (high frequency signal input terminal) 125 on the upper substrate 124 so as to extend in the direction orthogonal to the transmission line 122 on the surface of the substrate 124. ing. The open stubs 122b are provided on both sides of the transmission path 122 so as to have a predetermined distance from the GND pad 126, respectively. The width dimension of the open stub 122b is about half of the width of the transmission path 122.
The transmission path 122 is also provided with a narrow portion 122a that is narrower than the transmission path at a portion where the transmission path 122 and the GSG pad (high frequency signal input terminal) 125 are connected.

  The planar circuit including the transmission line 122, the open stub 122b, and the narrow portion 122a constitutes an input impedance matching unit. Here, the width dimension and the length dimension of the transmission line 122, the width dimension and the length (overhang) dimension of the open stub 122b, the separation shape with the GND pad 126 in the open stub 122b, the width dimension and the length dimension of the narrow portion 122a. The phase rotation amount, inductance, or capacitance is controlled by adjusting the length dimension of the through conductor 123A, and the input impedance is matched.

The pin 123 can be formed of a conductor whose surface is at least the same as that of the ground conductor layer 111. In the present embodiment, the central portion of the pin 123 has a structure filled with a conductor having the same or different property as the surface. The Specifically, the surface of the pin 123 is a thin film of Cu, Ag, Au or the like formed by plating, and the central portion (inside) of the cylindrical pin 123 is filled with a conductive paste. Heated and fired conductor. The photograph which observed the cross-section of the pin 123 of this invention is shown in FIG.
The central portion (inside) of the pin 123 is a porous body including a large number of minute voids V inside the conductor, as schematically shown in the photograph of FIG. 24 and the circle enlarged in FIG. This is because the conductive paste was formed by heat treatment, as will be described later.
As described above, when the pin 123 is made of a conductor including a large number of minute gaps V, even if the flexible substrate 101 is deformed, peeling occurs between the pin 123 and the inner surface of the minute hole α, or the pin 123 itself is It is possible to prevent a problem such as breakage and to improve the stress resistance due to deformation of the flexible substrate 101. Further, in order to improve the stress resistance, the size and density (arrangement) of the gap V are controlled in a preferable state inside the pin 123.

FIG. 6 shows the tip shape of the pin 123 in another embodiment.
As shown in FIG. 6A, the pin 123 may have a rounded tip shape with a rounded tip 123a. Alternatively, as shown in FIG. 6 (b), the center of the pin tip 123a has an acutely sharp shape, or as shown in FIG. 6 (c), the peripheral side of the pin tip has an acutely sharp shape. Also good. The sharp tip shape as shown in FIGS. 6A to 6C is preferable because the control accuracy of the distance between the pin tip 123a and the ground conductor layer 112 is eased. In particular, a sharp tip shape as shown in FIGS. 6B and 6C is preferable because the control accuracy of the distance between the pin tip 123a and the ground conductor layer 112 is further relaxed. As a result, there is an advantage that impedance matching is easy in manufacturing.

The surface of the pin 123 and the conductor pillar 114 can have a film configuration in which a film made of titanium (Ti) or chromium (Cr) and a film made of copper (Cu) are sequentially laminated from the surface side of the substrate 101. The film made of Ti or Cr is preferably as thin as possible in a range where the adhesion accuracy with the substrate is not impaired by the skin effect of the electromagnetic wave in the millimeter wave band. For example, when the film made of Cu is 300 nm or more, the film made of Ti or Cr is desirably about 40 nm.
Similarly, the planar circuits such as the transmission path 122, the open stub 122b, and the narrow portion 122a are formed from a surface of the upper substrate 124 with a film made of titanium (Ti) or chromium (Cr) and a film made of copper (Cu). They can be stacked in order.
The ground conductor layer 111 and the ground conductor layer 112 can also be formed by sequentially laminating a film made of titanium (Ti) or chromium (Cr) and a film made of copper (Cu) from the surface side of the substrate 101.

  These are all in a state suitable for electromagnetic wave transmission in the millimeter wave band. For example, the copper portion can be a plated layer as described later. As the planar circuits such as the ground conductor layer 111 and the ground conductor layer 112 on the front and back surfaces of the substrate 101, the transmission path 122, the open stub 122b, and the narrow portion 122a on the surface of the upper substrate 124, a conductor film is formed on the substrate 101 and the upper substrate 124. A formed substrate can also be used.

[Manufacturing method of mode converter]
A method for manufacturing the waveguide 100 shown in FIGS. 1 to 5 will be described with reference to FIGS. FIG. 7 is a front cross-sectional view showing the main part of the substrate in the manufacturing process of the mode converter step by step in the order of the manufacturing process.

[Post-wall waveguide structure]
First, as a preparation step, as shown in FIG. 7A, a substrate 101 is prepared as a base material. For example, the substrate 101 is a flexible substrate having a thickness of about 100 μm to 500 μm. Here, “degree” means having a thickness width of ± 50 μm. Conductive layers 111 and 112 made of a copper thin film are formed on the front and back surfaces of the substrate 101.
The thickness of the ground conductor layers 111 and 112 is desirably at least greater than the skin depth of the millimeter wave band. Since the skin depth is 270 nm at 60 GHz, about 2 μm is sufficient.

Next, as shown in FIG. 7B, as a drilling step, a recess (cavity) α and a hole β are formed in the substrate 101 by a processing means such as laser ablation or a drill.
The recess α is formed to have a desired depth corresponding to the length H4 of the pin 123 and a thickness corresponding to the diameter dimension H1. The hole β is formed so as to penetrate the substrate 101 corresponding to the plurality of conductor pillars 114, and the hole β has a diameter d, and the distance X between the adjacent holes β is larger than the diameter d. It is formed to be smaller.

When the substrate 101 is a flexible substrate, for example, a liquid crystal polymer substrate (LCP substrate) is formed with a concave shape by irradiating the laser with a UV-YAG laser, a CO ₂ laser, etc. with adjusted laser intensity. To do.

As a result, as shown in FIG. 7B, a recess α and a hole β are formed in the substrate 101. The hole diameters of the concave portion α and the hole portion β, which are fine holes, can be appropriately set in the range of 10 μm to 300 μm depending on the application of the mode converter 100 to be manufactured.
In a mode converter using a thin substrate, the degree of influence of the pin length on the transmission characteristics increases as the thickness of the waveguide is reduced, that is, as the substrate on which the waveguide is formed is reduced. Therefore, it is necessary to design the pin length more precisely. For example, in a thin waveguide having a thickness of 300 μm or less, it is necessary to control the pin length at the 10 μm level.

  Next, as shown in FIG. 7C, a conductor layer 121a and a conductor layer 121b made of a seed layer and a plating layer are formed inside the recess α and the hole β. The seed layer is made of, for example, Cr / Cu, Ti / Cu, etc., and has a thickness of 10 nm to 500 nm, and can be formed by sputtering. The plating layer is copper plating. The thickness of the copper plating layer is preferably at least greater than the skin depth of the millimeter wave band. Since the skin depth is 270 nm at 60 GHz, it is sufficient that the conductor layers 121a and 121b have a thickness of about 2 μm. At this time, conductor layers equivalent to the conductor layers 121 a and 121 b may be simultaneously formed on the ground conductor layers 111 and 112 on the front and back surfaces of the substrate 101.

  Next, as shown in FIG. 7D, a region corresponding to the opening 111a around the recess α is removed by etching to form a land 123c. At this time, by forming a resist other than the opening 111a and performing etching, the portion of the conductor layer 111 excluding the resist is removed, and the opening 111a and the land 123c are formed. The step of forming the opening 111a can be wet etching using an acid solution such as ferric chloride solution or cupric chloride solution.

Next, as a filling step, as shown in FIG. 7E, a paste-like conductive material is filled into the recess α by means such as screen printing.
First, a sheet-like cover is attached to the entire surface of the substrate 101, and only a portion corresponding to the recess α is removed to form a through hole. In this state, a conductive paste is applied to the entire surface of the substrate 101 by screen printing to fill the recess α. Thereafter, the sheet is removed, and as shown in FIG. 7E, the opening 111a is not filled with paste, but is filled only with the recess α.
As the cover, for example, a metal mask made of stainless steel or aluminum alloy is used.
As for the formation of the through hole, it is possible to use laser processing or the like in which energy is adjusted in the metal mask as in the formation of the hole β.

The paste-like conductive material includes conductors such as copper (Cu), silver (Ag), gold (Au), tin (Sn), and bismuth (Bi). Etc. can also be included.
The paste conductor does not need to be completely filled in the fine hole α, but it is desirable that the paste conductor is completely filled in the fine hole α when airtightness is required. In this way, a post wall waveguide structure is formed.
In order to reduce the size and thickness as in the mode converter of the present invention, it is inevitably necessary to make the pin small, and for that purpose, the high aspect ratio hole (fine hole) in which the pin is formed is further reduced. There is a need to. However, it is difficult to form a conductor inside the smaller the hole.
Since the present invention fills the inside of the fine holes of the conductive paste using a printing method, it is possible to fill the conductive paste to the inside of the fine holes, and stably pin the desired length. Can be formed.

[Upper transmission structure]
First, as a preparation process, as shown in FIG. 7F, an upper substrate 124 is prepared as a base material. The upper substrate 124 is made of the same material as the substrate 101 and is a flexible substrate that is half the thickness of the substrate 101. A conductive layer 122A made of a copper thin film is formed on the surface of the upper substrate 124.
The thickness of the conductor layer 122A is desirably at least greater than the skin depth of the millimeter wave band. Since the skin depth is 270 nm at 60 GHz, about 2 μm is sufficient.

Next, as shown in FIG. 7G, planar circuits such as a transmission path 122, an open stub 122b, a narrow portion 122a, a GND pad 126, and a GSG pad (high frequency signal input terminal) 125 are formed on the upper substrate 124 surface. . At this time, a resist patterned into a planar circuit shape is formed, and the other conductive layer 122A is removed by etching to form these planar circuits. Thereafter, the resist is removed with a resist stripping solution. This addition can also be performed by RIE (Reactive Ion Etching) process with CF ₄ gas and _{0 2} gas.
At this time, each dimension in each planar circuit is set to match the input impedance. Specifically, the width dimension and the length dimension of the transmission path 122, the width dimension and the length dimension of the open stub 122b, the separation shape of the open stub 122b from the GND pad 126, the width dimension and the length dimension of the narrow portion 122a, A length dimension of the through conductor 123A can be exemplified. In the figure, only the transmission path 122 is shown as a planar circuit.

Next, as illustrated in FIG. 7H, an adhesive layer 124 a is formed on the entire back surface of the upper substrate 124.
As the adhesive layer 124a, an epoxy or acrylic adhesive or an LCP adhesive layer is used for the substrate 124 made of an LCP film or polyimide.

  Next, as shown in FIG. 7 (i), a hole γ is formed in the upper substrate 124 by a processing means such as laser ablation. The hole γ corresponds to the through conductor 123A and the GND via 127, and a formation position and a formation dimension are set. The hole γ does not penetrate the planar circuit such as the transmission path 122 and the GND pad 126 on the surface (upper side) of the upper substrate 124, and penetrates the adhesive layer 124 a on the back surface (lower side) of the upper substrate 124. Formed. These are adjusted by setting the laser irradiation conditions.

Next, as a filling step, as shown in FIG. 7 (j), a paste-like conductive material is filled into the holes γ by means such as screen printing.
At this time, a paste-like conductive material is applied to the entire back surface of the upper substrate 124 and then pressed with a squeegee or the like to fill the holes γ. In this case, for example, the printing pressure is 0.25 MPa to 0.5 MPa.
The printing speed can be 5 mm / sec to 30 mm / sec.
The through conductor 123A does not have to be completely filled in the hole γ, but it is desirable that the hole γ is completely filled when airtightness is required. Thus, the upper transmission structure is formed.

Next, the post wall waveguide structure formed on the substrate 101 shown in FIG. 7E and the upper transmission structure formed on the upper substrate 124 shown in FIG. Bonding is performed by aligning, bonding, and heat-pressing.
The heating and pressurizing treatment for bonding the substrate 101 and the upper substrate 124 can be, for example, a heating temperature of 180 ° C., a pressure of 1 MPa, and a heating time of 60 minutes. In this heating and pressurizing process, the adhesive layer 124a is bonded to the surface of the ground conductor layer 111, and the conductors formed from the conductive paste filled in the recess α and the hole γ may be connected to each other. The processing conditions are such that no deformation occurs.

  By such a process, the mode converter 100 can be formed.

In the present embodiment, a fine hole (concave portion) α having a depth of about half the thickness of the substrate 101 is formed by laser ablation, and a paste-like conductor is filled therein, so that sputtering, plating, etc. Compared with the case where the pin 123 is formed, the length of the pin 123 can be accurately set even when the size is reduced. Therefore, it is possible to accurately realize the excitation pin length that minimizes signal reflection. That is, it is possible to manufacture the mode converter 100 that can effectively transmit the millimeter wave signal transmitted from the wireless communication IC through the planar circuit (transmission path) 122 without loss.
Further, since the pin 123 is formed by filling the conductor paste, the input impedance matching can be easily maintained without being electrically deformed even when an external force is applied to the pin 123.

  Moreover, although it is thought that an impedance matching condition is influenced also by the diameter of the pin 123, since the diameter of the recessed part (alpha) used as the pin 123 can be adjusted with etching conditions, it has high adjustment capability.

  Further, the waveguide 110 of the present embodiment is formed by laminating a plurality of substrates, and in the single substrate 101 as compared with the prior art in which via-via connection is performed in the middle of the pin 123 by the land structure of the laminated interface. Therefore, a land structure in the middle of the pin 123 is not required inside the waveguide 110, and the adverse effect of signal reflection due to a change in the pin diameter can be reduced.

  According to the manufacturing method of the present embodiment, since the pins 123 and the plurality of conductor pillars 114 that become the reflecting portions 110 can be formed simultaneously in parallel, the number of processes required for manufacturing is reduced and the number of processes is reduced. It is possible to reduce working time and manufacturing cost.

  According to the manufacturing method of the present embodiment, the post-wall waveguide structure formed on the substrate 101 shown in FIG. 7E and the upper transmission structure formed on the upper substrate 124 shown in FIG. Since they are formed separately, the length of the pin 123 can be adjusted after the mode converter 100 is manufactured.

  According to the present embodiment, the planar circuit is formed on the surface of the upper substrate 124, that is, the outermost surface of the mode converter 100, and shape adjustment (trimming) of the planar circuit can be easily performed from the outside of the mode converter. . For example, even if the pin 123 cannot be formed with a designed length and a desired characteristic cannot be obtained, the transmission characteristic can be adjusted by trimming the planar circuit after the mode converter 100 is manufactured. .

  According to the present embodiment, since a flexible substrate is used for the substrate 101 and the upper substrate 124, a light-weight and low-loss waveguide can be realized. At the same time, having flexibility allows a variety of uses.

  In the embodiment described above, as shown in FIG. 2, the diameter dimension of the excitation pin 123 is set to be uniform from the base end portion 123b to the tip end portion 123a. However, the tip end portion 123a has an angle so that the side surface has an angle. The diameter can be reduced as compared with the base end portion 123b. In this case, the metal adhesion effect inside the recess α can be improved, and the certainty in the formation of the seed layer and the copper plated conductor film 121a and the formation of the pin 123 by filling the conductive paste can be improved.

Further, in the present embodiment, the planar circuit including the transmission line 122, the open stub 122b, and the narrow portion 122a is configured as shown in FIG. 3 as the input impedance matching unit, but other configurations may be employed.
When the open stub 122b is provided so as to have the same overhanging length only on one side of the transmission line 122, it has the same effect as the line length of the transmission line 122 is increased. The open stub 122b is preferably provided symmetrically with respect to the central axis in which the transmission path 122 extends. Further, it can be asymmetrical on both sides of the transmission path 122. As described above, the shape and arrangement of the open stub 122b have an extremely large effect on the input impedance.

  Furthermore, in the present embodiment, the waveguide 110 has a plurality of conductive pillars 114 as shown in FIG. 1, but as shown in FIG. 9, it is rectangular in plan view and emits radio waves from the mode converter. The side that becomes the rear wall facing the opening 102 is a plurality of conductive pillars 114, and the two sides that extend in the direction from the pin 123 toward the opening 102 are continuous slit walls 141 in that direction. The hole β1 can also be formed. In this way, by setting the side wall as the plurality of conductor pillars 140, even if a problem such as electrical openness occurs in some conductor pillars, the remaining conductor pillars are connected to the ground conductor layer. If it is connected to, the function can be maintained. Further, by using the side wall reflecting portion as the slit wall 141, leakage of electromagnetic waves can be more effectively prevented than the conductor pillar.

In the present embodiment, as shown in FIG. 1, the substrate 101 is disposed outside the opening 102 of the waveguide 110. However, as shown in FIG. 9, the slit wall 141 is provided to the end of the substrate 101. It can also be formed. In this case, since the back side of the pin 123 is the waveguide 110 composed of the plurality of conductor pillars 140, even when the long hole β1 is formed in the substrate 101, the substrate 101 is not separated.
With such a configuration, since the side wall in the electromagnetic wave traveling direction is a continuous wall, it is possible to prevent disturbance of the electromagnetic wave form due to discontinuous conductor arrangement.

  Further, when the long hole β1 is formed in this way, as shown in FIG. 10, it is also possible to form a long hole β1 formed continuously so as to overlap many cylinders in plan view.

Further, as shown in FIG. 11, three long sides other than the opening 102 in the rectangular waveguide 110 are formed as continuous long holes β2 to form a U-shaped continuous slit wall 142 and separated only in the vicinity of the opening 102. The conductor pillars 140 can be formed so that the waveguide 110 is separated.
Further, as shown in FIG. 12, holes β1 and β3 that are continuous on three sides of the rectangular waveguide 110 other than the opening 102 are formed to form corresponding slit walls 141 and 143, and portions where the sides intersect. In this case, a conductor post 140 can be provided to form a state in which the waveguide 110 is separated.
Further, as shown in FIG. 13, long holes β1 and β3 that are continuous on three sides of the rectangular waveguide 110 other than the opening 102 are formed to form corresponding slit walls 141 and 143, and the sides intersect. The part can be provided with a conductor post 140 to form a state in which the reflecting part 110 is separated. In this case, since the discontinuous portion is only one post, the disturbance of the electromagnetic wave form in the discontinuous portion can be minimized, and the structure is more mechanically stable than the structure shown in FIG. It can be. As described above, the waveguides 110 are separated from each other, and the substrate is formed in a continuous state on the inner side and the outer side of the waveguide 110 serving as the mode converter 100, so that the substrate 101 is not separated.

  In addition, as shown in FIG. 13, a slit wall 144 in a state where the reflecting portion is widened can be provided outside the opening 102. In this case, an H-plane fan type horn antenna can be formed, and the antenna gain can be improved.

  As described above, a part of the conductor pillar 114 having a gap has a structure having the slit walls 141, 142, 143, and 144, so that the waveguide 110 between the conductor films 111 and 112 forming the waveguide 100 is large. The portion can be replaced with slit walls 141, 142, 143, and 144. As a result, the leakage of electromagnetic waves can be greatly suppressed as compared with the conventional case, and it is possible to contribute to the improvement of the radiation efficiency of the antenna and the reduction of the radiation loss of the waveguide. Further, since the area through which the current flows is larger than when all the conductor pillars 114 are used by adopting the slit wall, the electrical connection between the post wall 114 and the conductor films 111 and 112 that may occur in the case of all the post walls 114 is achieved. It becomes possible to greatly reduce the risk and failure of the transmission mode due to non-conduction.

  In the above-described embodiment, as shown in FIGS. 1 and 2, the diameter of the conductor pillar 114 is set to be uniform from the ground conductor layer 111 to the ground conductor layer 112 on the back surface, but as shown in FIG. In addition, the diameter can be reduced from the front surface 101a toward the back surface 101b so as to have an angle θ5. In this case, the metal adhesion effect inside the hole β can be improved, and the seed layer and the copper-plated conductor 121a can be reliably formed. In this case, it is possible to improve the metal adhesion effect inside the fine hole β, and to surely form the conductive pillar 114 by the seed layer and copper plating. Further, by having the angle θ5, it is possible to improve the metal adhesion effect inside the fine hole α and to reliably form the ground conductor layer 111 by the seed layer and the copper plating.

  Furthermore, as shown in FIG. 15, the diameter can be increased after the diameter is reduced from the front surface 101 a toward the back surface 101 b so as to have an angle θ <b> 6 and an angle θ <b> 7. By having the angle θ6 and the angle θ7, it is possible to improve the metal adhesion effect inside the fine hole α and to reliably form the seed layer 121a and the copper-plated ground conductor layer 111.

The mode converter 100 of this embodiment can be a millimeter wave communication module substrate 200 as shown in FIG.
The millimeter wave communication module substrate 200 includes a mode converter 100 and a wireless communication IC (semiconductor chip) 210 having a wireless transmission / reception functional element flip-chip connected to the upper surface side as an example of the mode converter 100. The millimeter wave communication module substrate 200 is provided with a ground conductor layer 111 serving as GND and a transmission path 122 on the upper substrate 124 on the surface of the substrate 101 on which the waveguide 100 is formed, and at the same level as the transmission path 122. The GSG pad 125 at the end of the transmission line 122 and the terminal 211 of the wireless communication IC (semiconductor chip) 210 are connected. At high frequencies such as millimeter waves, the influence of parasitic inductance becomes very large, so short-distance mounting with bumps is preferable to wire bonding.

The mode converter 100 of the present embodiment can be a millimeter wave communication module substrate 200A as shown in FIG.
The millimeter wave communication module substrate 200A shown in FIG. 17 is different from the millimeter wave communication module substrate 200 shown in FIG. 16 in that the pin terminal (connection portion) 123b is a GSG pad 125, and the pin terminal 123b A terminal 211 of a wireless communication IC (semiconductor chip) 210 is connected.
Corresponding components other than this are denoted by the same reference numerals and description thereof is omitted. The terminal 212 of the wireless communication IC (semiconductor chip) 210 is connected to the GND pad 126 connected to the GND via 127. In this manner, a planar circuit that does not include the transmission path 122, the open stub 122b, the narrow portion 122a, or the like can be used. Even in the millimeter wave communication module substrate 200A, the terminals 211 and 212 are greatly affected by the parasitic inductance at a high frequency such as millimeter waves.

  Further, the excitation pin structure 120 of the present embodiment is a microstrip line as shown in FIG. 3, but may be a coplanar as shown in FIG. In this case, the signal line 132 is formed in the same layer as the ground conductor layer 111 which becomes the upper surface GND layer of the PWA.

<Experimental example>
Hereinafter, experimental examples according to the present invention will be described.

  FIG. 19 is a simulation model of a printed circuit board post wall waveguide (PWW) that is thinned by the mode converter according to the present invention. In this type, the openings of the printed circuit board post-wall waveguide (PWW) 100 are arranged to face each other. The signal input / output ports are a port 125 and a port 125 at the end of the microstrip line 122, and the microstrip transmission mode (TEM mode) is converted into a TE10 mode which is a waveguide transmission mode through the pin terminal 123b. The distance between the centers of the pins 123 was set to 10 mm.

  Three-dimensional electromagnetic field analysis software HFSS was used for the simulation. The thickness of the substrate 101 was set to 175 μm. In high frequency circuit design, the reflection coefficient is desirably -15 dB or less.

  FIG. 20 is an enlarged perspective view of the planar circuit portion. In the model shown in FIG. 20, the narrow portion 122 a is not provided, but has an open stub 122 b and a connection portion 122 A having a width dimension equivalent to that of the transmission path 122.

FIG. 21 is a simulation result of the reflection coefficient of the printed circuit board post-wall waveguide using a simulation model corresponding to the mode converter having the planar circuit formed as the wide connection portion shown in FIG.
The distance between the pin and the rear post wall 110A was optimized at 60 GHz. The length of the pin 123 is half the thickness of the substrate 101, and the thickness of the upper substrate 124 is a value corresponding to 2/3 of the length of the pin 123. This microwave circuit is preferably designed so that the reflection loss is lower than -15 dB. The optimization of the distance between the pin 123 and the rear post wall 110A is not λ / 4 that is normally used for the wavelength λ corresponding to the use frequency of 60 GHz, but λ / 2 corresponding to the thinning of the substrate 101. As optimized.

In this graph, a frequency region where S11 <−15 dB is defined as a band.
From the results shown in FIG. 21, it can be seen that since the distance between the pin 123 and the rear post wall 110A is optimized at a use frequency of 60 GHz, it is less than −115 dB over a bandwidth of about 1 GHz around 60 GHz. That is, the band is about 2 GHz.

However, since the bandwidth used for the specific power-saving wireless communication at 60 GHz is 7 GHz to 9 GHz, the planar circuit model in which the open stub 122b is provided in the transmission path 122 does not satisfy the specification of this application. Become.
This is presumably due to the fact that the planar circuit configuration shown in FIG. 20 does not provide sufficient input impedance matching.

FIG. 22 is a model in which a narrow portion 122a is provided at the connection portion between the transmission line 122 and the GSG pad (high frequency signal input terminal) 125 with respect to the planar circuit shape shown in FIG.
FIG. 23 shows a simulation result after the impedance mismatching problem is adjusted by adding impedance matching means as the narrow portion 122a.
Since the task of impedance matching is performed, it can be seen that the bandwidth is significantly widened up to 5 GHz. In addition to this, by adjusting the width dimension and length dimension of the transmission path 122, the width dimension and length dimension of the open stub 122b, and the separation state between the open stub 122b and the GSG pad (high frequency signal input terminal) 125, It is possible to sufficiently satisfy the license-free 60 GHz band of each country set in the range of 57 to 66 GHz.

Further, in the simulation model corresponding to the mode converter shown in FIG. 22, the simulation is performed by changing the substrate thickness. Similarly, the frequency region where S11 <−15 dB is calculated as a band, and the bandwidth is 7 GHz˜ A case where the frequency is 9 GHz is described as “excellent”, a case where the bandwidth is 5 GHz to 7 GHz is described as “good”, and a case where the bandwidth is 5 GHz or less is described as “bad”. As a result, the thickness of the substrate 101, that is, “excellent” when the waveguide 110 thickness is 175 μm, “excellent” when 250 μm, “good” when 300 μm, “bad” when 400 μm, “bad” when 500 μm, When it was 550 μm, it was “bad”.
From this result, it can be seen that the present invention can obtain a sufficient band when the waveguide thickness is thin.

  The present invention can be widely applied as a device for high-speed and large-capacity communication of several Gbps using the millimeter wave band.

100 ... mode converter, 101 ... substrate (flexible substrate),
101a ... front surface, 101b ... back surface, 111a ... opening,
110 ... waveguide, 111, 112 ... ground conductor layer, 114 ... conductor pillar,
120 ... excitation pin structure, 122 ... planar circuit (transmission path), 123 ... pin,
123A ... through conductor, 124 ... upper substrate (flexible substrate), 123b ... pin terminal (connection part), 123c ... land, 125 ... GSG pad (high frequency signal input terminal),
126 ... GND pads, 127 ... GND vias,

Claims (4)

A flexible substrate;
A ground conductor layer formed on one main surface and the other main surface of the flexible substrate;
A connecting portion formed on one main surface side of the flexible substrate;
Fine holes formed from one main surface of the flexible substrate to a desired depth;
A pin made of a conductor filled in the micropore and connected to the connecting portion;
A mode converter characterized by comprising at least.   The mode converter according to claim 1, wherein the flexible substrate has a thickness of 300 μm or less.   The mode converter according to claim 1, wherein the conductor is a porous body.   The mode converter according to claim 1, wherein the conductor is formed by heat-treating a conductive paste.