WO2005112185A1

WO2005112185A1 - Feed-through structure and feed-through type optical module

Info

Publication number: WO2005112185A1
Application number: PCT/JP2005/008862
Authority: WO
Inventors: Tomoaki Kato
Original assignee: Nec Corporation
Priority date: 2004-05-14
Filing date: 2005-05-16
Publication date: 2005-11-24
Also published as: JPWO2005112185A1

Abstract

Transmission characteristics of feed-through are enhanced over a wide band. A feed-through optical module (100) comprising a dielectric substrate (1) on which a coplanar line with a rear surface conductor is formed and a high frequency component is mounted, and a frame (2) arranged thereon. A plurality of through electrodes (5, 6) are formed in the dielectric substrate (1) and the frame (2). Thicknesses of the dielectric substrate and the frame are respectively t1 and t2, arranging pitches of the through electrodes (5, 6) are respectively d1 and d2, dielectric constants of the dielectric substrate (1) and the frame (2) are respectively ϵr1 and ϵr2, the highest working frequency is f, and the speed of light is c0. The thickness t1 and t2 and the arranging pitch d1 and d2 satisfy the following expressions: t1<c0/(4f·(ϵr1-1)1/2), t2<c0/(4f·(ϵr2-1)1/2), d1<c0/(4f·ϵr11/2), and d2<c0/(4f·ϵr21/2).

Description

Feedthrough structure and feedthrough optical module

Technical field

The present invention relates to a feed-through structure and a feed-through type optical module.

Background art

[0002] With the explosive demand for broadband multimedia communication services such as the Internet, there is a demand for the development of larger capacity and higher performance optical fiber communication systems. The number of optical modules used in such large-scale communication network systems is steadily increasing with the size of the systems. Not to mention the size of the optical module itself, the cost of the optical module occupying the entire system and the mounting load cannot be ignored. For this reason, not only miniaturization of the optical module itself, 'high-performance integration', and cost reduction, but also realization of an easier-to-use electrical Z optical signal input / output interface is an important issue.

Conventionally, a communication optical module, particularly an optical module for a backbone system, has a big optical fiber coupled to a semiconductor optical element in a package via a lens or the like as an optical signal input / output interface. It has been known. In addition, there are also known ones that use a high-frequency compatible coaxial connector represented by a GPO connector or the like as an electric input / output interface (also called a butterfly module).

[0004] However, there are almost no small high-frequency coaxial connectors developed exclusively for optical modules, and currently available standard products tend to be larger than the optical module package dimensions. It is of course possible to partially change the shape of the coaxial connector according to the package, but this will result in increased costs and reduced versatility.

[0005] When mounting an optical module having a coaxial connector type electric input / output interface on a printed circuit board, it is necessary to consider a movable space of the coaxial connector and a space for routing a coaxial line. In addition, it is necessary to consider the movable range of the torque wrench for tightening the coaxial connector in advance, and to design a layout with a margin around the optical module mounting part, from the viewpoint of component mounting efficiency and layout flexibility. Is also not preferred.

[0006] In this regard, in this regard, a so-called simple attachment and detachment (snap- ) -Type coaxial connectors are also used in some cases. However, the high-frequency characteristics are slightly sacrificed, and the space for moving the coaxial connector itself and the space for running the coaxial line are still required. Even if an optical module can be automatically mounted on a printed circuit board using a robot, the coaxial connectors must be manually routed and removed. Therefore, there is a limit to the improvement of the throughput of the printed circuit board assembly process and the cost reduction effect.

[0007] "Feed-through" is known as an electric signal input / output interface, which is smaller and easier to use than a coaxial connector. In the past, attempts have been made to improve the feedthrough, which is originally a mechanism for supplying power to elements in a package, so that it can handle even higher frequency signals, and apply it to ultra-high-speed IC modules and optical modules for communication.

[0008] "Feed-through" is a general term for a power feeding mechanism in which a conductor penetrates the inside of a side wall of a package as the name implies. The feed-through type has a simple structure in which a metal rod is penetrated through a dielectric wall, and a structure based on a planar circuit (a microstrip coplanar device mainly using ceramic as a dielectric substrate). Waveguides). The above-described coaxial connector is also a feedthrough in a broad sense, and can be classified into the former.

[0009] Each feedthrough, if properly designed, functions as a practical electric signal input / output interface for high-frequency signals. In particular, the latter is advantageous in terms of miniaturization and low cost. If the package also becomes a conductive material, a highly airtight dielectric material such as ceramic is buried in the package side wall so that the signal line and the package do not short-circuit, and a lead wire or strip line is penetrated inside. Structure.

[0010] Feedthroughs have been improved in order to meet the demands for miniaturization and wideband applications required for application to ultra-high-speed ICs and optical modules for communication. For example, those based on coplanar waveguides or microstrip lines can already handle high-speed lOGbZs electrical signals.

[0011] A conventional configuration example of the feedthrough is disclosed in, for example, Japanese Patent Application Laid-Open No. 2002-190541. In the high-frequency circuit package described in the document, a frame having a dielectric force is laminated on a dielectric substrate on which high-frequency circuit components are arranged so as to surround the high-frequency circuit components. It is. Further, a lid is mounted on the frame, whereby high-frequency circuit components are packaged!

On the dielectric substrate, a line conductor (main line) for transmitting a high-frequency signal to a high-frequency circuit component and ground conductor layers (surface ground) provided on both sides thereof are formed as coplanar lines. ing. These conductors are extended to the end of the dielectric substrate. As described above, since the frame is mounted on the dielectric substrate, a part of the coplanar line is sandwiched between the dielectric substrate and the frame.

[0013] A lower conductor layer (back surface electrode) for grounding is formed on the entire back surface of the dielectric substrate. A metal film (upper electrode) such as gold is formed also on the upper surface of the frame. Both the back electrode and the top electrode are connected to the surface ground of the coplanar line by through electrodes (vias) penetrating the dielectric substrate and the frame in the thickness direction, respectively. Thus, the back electrode and the top electrode function as ground conductors. The cross-sectional shape of the ground conductor thus configured is annular, and the main line of the coplanar line is located substantially at the center of the annular conductor. Therefore, the configuration is a pseudo waveguide configuration.

Disclosure of the invention

Problems to be solved by the invention

However, the above document (Japanese Patent Application Laid-Open No. 2002-190541) does not sufficiently consider the effect of the provision of the upper electrode on the transfer characteristics. The problems with the proposed structure and their countermeasures are correctly indicated.

[0015] The problem is that the cross-sectional shape force of the structure around the feed-through described in the same document is in the form of a "symmetric strip line" (or an array thereof), that is, the main structure of the strip line is a parallel plate just filled with a dielectric. This is inevitably caused by adopting a form in which the electrode pattern is embedded. The signal transfer characteristics of the feedthrough in this document are expected to behave similarly to those of such a symmetrical strip line (and its derived structure).

[0016] Here, the problem in the "symmetric stripline" is as follows.

(1) Suppression of radiation when thickness symmetry is broken

(2) Suppression of propagation of higher-order modes in the thickness direction of the dielectric filling the gap between parallel plates (3) Propagation suppression of parallel plate mode

It can be roughly divided into three.

[0017] First, regarding (1), the dielectric (frame) covering the surface of the strip line is made of the same material as the high-frequency planar circuit board, and the thickness of both members is made relatively easy. It can be resolved. However, there is a difficulty that the degree of freedom in design is restricted because the thickness of the dielectric cannot be freely set.

Next, in order to suppress the propagation of the higher-order mode in the thickness direction in (2), at the maximum operating frequency of the module using the feedthrough, a single-mode condition must be satisfied in the thickness direction of the dielectric. Need to be satisfied. In addition, it is necessary to limit the thickness of the dielectric according to the relative permittivity of the dielectric and the maximum operating frequency.

Further, in order to suppress the propagation of the parallel plate mode of (3), the upper and lower conductors forming parallel plates, that is, the back surface conductor and the upper surface conductor of the high frequency planar circuit board are kept at the same potential. There are ways to suppress the existence itself. Alternatively, there is a method of preventing propagation by providing a periodic structure or the like.

[0020] In the former case, it is necessary to devise a structure in which both conductors forming the parallel plate are short-circuited at high frequency to each other. When the high-frequency planar circuit board is a coplanar waveguide with a back conductor, the front ground and the top electrode, and the front ground and the back conductor form a parallel plate. Therefore, a mechanism for short-circuiting these three conductors at high frequencies using, for example, through conductors is required. However, through-conductors (vias) widely used in high-frequency planar circuit boards have a skin thickness of less than 1 m in the millimeter-wave band even when gold (Au), a typical electrode material, is used. In addition, the parasitic inductance of the through conductor cannot be ignored. Therefore, the impedance increases with the frequency, and it is difficult to realize an ideal short-circuit state especially in the millimeter wave band.

On the other hand, regarding the latter periodic structure, a method of periodically arranging through conductors at intervals of 1Z4 or less of the propagation wavelength of a dielectric in a medium is widely used as means for suppressing the propagation of the parallel plate mode. Have been. By the way, feedthroughs are originally useful as electrical input / output interfaces that are small enough to be embedded in the relatively thin sidewalls of the knockout. The propagation wavelength in the medium is thinner in the millimeter wave band than the thickness of the package side wall. Often. Therefore, it is not expected that the through conductors are arranged side by side so that periodicity is generated.

[0022] As described above, the structure of the feedthrough described in the above-mentioned conventional document has a problem in its transfer characteristics, and no measures have been taken for any means for solving the problem. Therefore, it is difficult to put the DC force into practical use as an ultra-wide band electric signal input / output interface over the millimeter wave band.

Accordingly, an object of the present invention is to overcome the problems of the conventional feed-through structure described in the above-mentioned conventional literature and to provide a feed-through structure and a feed-through structure having good transmission characteristics over a wide band. To provide a type module.

Means for solving the problem

[0024] In order to achieve the above object, a feed-through structure of the present invention is provided with a first dielectric substrate forming a coplanar line with a back electrode, and is disposed on the first dielectric substrate. At least an opening is formed on the coplanar line, and a second dielectric substrate having an upper surface electrode formed on an upper surface thereof, wherein the first dielectric substrate has a surface ground of the coplanar line. A plurality of first through conductors for short-circuiting the top electrode and the back electrode, and the second dielectric substrate includes a plurality of second through conductors for short-circuiting the surface ground and the top electrode; A feed-through structure formed on an end surface of the first dielectric substrate and intersecting in a direction along a main line of the line, the second end surface conductor short-circuiting the surface ground and the upper surface electrode; 1st and 1st The relative permittivity of the dielectric substrate of FIG. 2 is ε r and ε r, respectively, and the maximum operating frequency at which the main line propagates is f

1 2, when the speed of light is c, the thicknesses t and t of the first and second dielectric substrates, respectively.

0 1 2

And the respective arrangement pitch d of the first and second through conductors in the direction along the main line.

1, d is

2

t <c / (4f- (sr -1) ^1/2 )

1 0 1

t <c / (4f- (sr -1) ^1/2 )

2 0 2

d <c / (4f- ε r ^1/2 )

1 0 1

d <c / (4f- ε r ^1/2 )

2 0 2

Is satisfied. [0025] In the feed-through structure of the present invention, the arrangement pitch of the first through conductors and the arrangement pitch d of the second through conductors are the same, and the arrangement pitch at that time is the same.

2

d force d <c0 / (4f-ετ1 / ² ) (: or whichever is greater)

1 2

May be used. Further, the coplanar lines may be arranged in an array.

[0026] The feed-through structure of the present invention configured as described above is different from the above-described conventional literature in the following points (1) to (3). In other words, (1) the thickness of the second dielectric substrate sandwiched between the surface ground and the upper electrode is specified in accordance with the highest operating frequency, and (2) the input / output discontinuity of the feedthrough The point that the surface ground and the upper surface electrode are short-circuited by using the second end substrate provided in the section, and (3) the distance between the adjacent penetrating conductors with respect to the first and second penetrating conductors, It is specified in correspondence with the maximum operating frequency.

[0027] Accordingly, unnecessary modes that are likely to occur in a discontinuous waveguide structure such as a feedthrough (higher-order modes in the thickness direction propagating in the second dielectric substrate sandwiched between the surface ground and the upper surface electrode) And the parallel plate mode) are effectively suppressed. As a result, the transfer characteristics as an electrical signal input / output interface are dramatically improved.

[0028] The first reason is as follows. That is, in the present invention, the thickness of the second dielectric substrate sandwiched between the surface ground and the top electrode closest to the surface ground is suppressed to 1Z4 or less of the propagation wavelength in the medium at the highest operating frequency. . Therefore, the higher-order mode in the thickness direction is not propagated, and the higher-order mode is prevented from being coupled to the basic propagation mode of the strip line constituting the feedthrough.

[0029] If an electric signal is transmitted using a conventional structure that does not specify such a dielectric thickness, excitation and transmission of a higher-order mode in the thickness direction are performed from a point where a certain frequency is exceeded. May not be stopped. As a result, the transfer characteristic of the fundamental propagation mode of the strip line constituting the feedthrough is significantly impaired by the coupling with the higher-order mode.

[0030] The second reason is that the surface ground and the upper surface electrode are short-circuited at high frequency using the second end surface conductor formed in the feedthrough. This causes the high-frequency potentials of both conductors to be approximately equal, resulting in unwanted modes (in this case, surface ground and top conductor). Excitation of the parallel plate mode propagating between the body) is prevented.

[0031] If an electric signal is transmitted using a conventional structure having no end conductor for short-circuiting at high frequency, a high-frequency potential difference occurs between the surface ground and the upper conductor at the discontinuous boundary described above. . As a result, the parallel plate mode may be excited in the dielectric sandwiched between them. Then, if the transfer characteristics of the fundamental propagation mode of the strip line constituting the feedthrough are significantly impaired by the coupling with the parallel plate mode, there is a concern that inconvenience may be caused.

[0032] The third reason is that the second through conductors are arranged at intervals of 1Z4 or less of the propagation wavelength in the dielectric at the highest operating frequency, and the surface ground and the upper surface conductor are short-circuited at high frequency. As a result, even if the effect described in the second reason is insufficient and the parallel plate mode is excited, the propagation can be suppressed. Therefore, the parallel plate mode is prevented from being coupled to the fundamental propagation mode of the strip line constituting the feedthrough.

As described above, a feed-through having an ideal wide-band transfer characteristic over a direct-current millimeter-wave band can be realized only by combining all of the above (1) to (3). On the other hand, if any one of these conditions is not satisfied, the transfer characteristics are necessarily restricted, and it is difficult to function as a practical wideband feedthrough.

[0034] The above-described structural contrivance can be easily realized without making any change to the ceramic sheet multi-layer firing technique, which is a typical technique for manufacturing a conventional feedthrough. It is possible to use exactly the same process for the pattern jung of the electrode wiring. Regarding the restriction on the thickness of the dielectric substrate, it is only necessary to select a ceramic sheet having an appropriate thickness in advance. Also, the through conductor can be formed in exactly the same manner as the formation of the through conductor on the ceramic-based high-frequency planar circuit board. Further, the end face conductor can be cut by a dicing blade so as to cross the through conductor formed on the ceramic substrate, for example. As for the material, glass, a dielectric crystal, a resin material, or the like can be used in addition to ceramic.

[0035] Feed-through structure of the present invention, also, the first and the second dielectric board is even fulfills ^{t · sr 1/2 = t · ε} r 1/2 Good. [0036] Further, the first dielectric substrate is formed on an end face of the first dielectric substrate that intersects in a direction along a main line of the coplanar line, and connects the front surface ground and the rear surface electrode. It further has a first end face conductor to be short-circuited, wherein the first end face conductor is symmetrically arranged between the main lines in the end face of the first dielectric substrate, and Are arranged symmetrically with the main line therebetween in the end surface of the second dielectric substrate, and the distance d between the first end surface conductors is d.

11 and the distance d between the second end surface conductors are d ≤ c Z (2f ' _£ r ^1/2 ) and

12 11 0 1

It may satisfy d ≤c / (2f- ε r ^1/2 ).

12 0 2

[0037] Further, the first and second end face conductors may be provided by dividing a through conductor penetrating the first and second dielectric substrates.

Further, the first dielectric substrate and the second dielectric substrate have respective thicknesses t and t.

1 2 The same material may be made of the same material, and the material may be any one of ceramic, glass, and resin. Alternatively, it is preferable that both substrates have substantially the same linear expansion coefficient even if they are not the same material. More specifically, it is preferable that the materials of the first dielectric substrate and the second dielectric substrate have excellent airtightness and water resistance, and it is preferable that a metal material can be brazed.

[0039] Further, the coplanar line may be one in which at least a part of the main line and a surface ground is plated. Further, it is preferable that a force capable of wire bonding or a bump can be formed on the electrode surface. Also, a lead electrode may be provided on the electrode surface! /.

[0040] Further, the feed-through structure of the present invention includes at least one of the outer peripheral surfaces of the first dielectric substrate and at least one of the outer peripheral surfaces of the second dielectric substrate. In this case, a plurality of bumps are formed on each of the outer peripheral surfaces of the first and second dielectric substrates in the same plane. The plurality of bumps are configured to conduct to the first and second end surface conductors and a high-frequency circuit component disposed in the opening of the second dielectric substrate, May be used. Further, the outer peripheral surface on which the plurality of bumps are formed may be parallel to a direction along the main line. [0041] By arranging a high-frequency circuit component in the feed-through structure of the present invention on the first dielectric substrate and in the opening of the second dielectric substrate, the feed through structure of the present invention can be obtained. A through-type optical module is obtained.

The invention's effect

As described above, according to the feed-through structure and the feed-through type optical module of the present invention, the following effects can be obtained by the following (1) to (3). That is, according to the present invention, (1) the thickness of the second dielectric substrate sandwiched between the surface ground and the upper surface electrode is defined in accordance with the maximum operating frequency, and (2) the input / output discontinuity of the feedthrough The surface ground and the top electrode are short-circuited using the second end board provided in the section, and (3) the distance between the adjacent penetrating conductors is set to the maximum operating frequency for the first and second penetrating conductors. It is stipulated correspondingly. As a result, even when using elements that handle ultra-high-speed signals, such as ultra-high-speed ICs and optical communication devices, it is possible to obtain ideal broadband transmission characteristics from DC to millimeter-wave bands. .

Brief Description of Drawings

FIG. 1A is a perspective view showing a feed-through type optical module according to a first embodiment of the present invention.

FIG. 1B is a sectional view showing the feed-through type optical module according to the first embodiment of the present invention.

FIG. 2A is a top view showing a feed-through type optical module according to a second embodiment of the present invention.

FIG. 2B is a side view showing the feed-through type optical module according to the second embodiment of the present invention.

FIG. 3A is a graph showing a small signal frequency response characteristic of the feed-through type optical module. FIG. 3B is a graph showing a small signal frequency response characteristic of the feed-through type optical module.

[0044] 1 Dielectric substrate 2 Frame

5, 6 Through electrode

10, 11 End electrode

21 Back electrode

22 Surface ground

23 Top electrode

25 main tracks

100, 101 feed-through type optical module

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First Embodiment)

FIG. 1 shows a feed-through type optical module according to a first embodiment of the present invention. FIG. 1A is a perspective view of a feed-through type optical module, and FIG. 1B is an enlarged cross-sectional view of the periphery of the feed-through of the same module cut in the longitudinal direction (the “signal propagation axis” direction in the drawing).

The feed-through type optical module 100 has a dielectric substrate 1 and a frame 2 disposed on the dielectric substrate 1. In the package (on the dielectric substrate 1), forces not shown are mounted, for example, high-frequency circuit components such as optical devices, electronic circuits for controlling them, and lenses for coupling signal light to optical devices. ing.

[0048] The dielectric substrate 1 is made of a sheet-shaped dielectric member (relative permittivity ε substrate thickness t), a part of which is hollowed out. On the surface of the dielectric substrate 1, a main line 25 for transmitting a high-frequency signal to a high-frequency circuit component and surface grounds 22 disposed on both sides thereof are formed. Thus, (gap g, the characteristic impedance z between the width w, the main line path 25 and the surface ground 22 of the main line 25) ₀ back of the dielectric substrate 1 in the form of a coplanar line

0

A back surface electrode 21 for grounding is formed on the entire surface.

[0049] In the portion where the main line 25 is hidden under the frame 2, the width w of the main line 25 is smaller than the width w of the main line 25. The width of the main line 25 is gradually reduced from the width w to the width w '. As a result, the characteristic impedance of the coplanar line is It keeps constant in the direction!

[0050] Note that high-melting-point conductive materials are used for these electrodes constituting the coplanar line. This makes it difficult for the sheet-shaped dielectric member to deteriorate when it is fired. After firing, plating is performed for the purpose of improving conductivity and preventing corrosion.

The frame 2 is made of a sheet-like dielectric member similar to the dielectric substrate 1 (relative permittivity ε r, substrate thickness t

2

) Is hollowed out. On the upper surface of the frame 2, an upper electrode 23 is provided.

2

It is formed over the entire surface. The thickness t of the dielectric substrate 1 is the same as the thickness t of the frame 2.

1 2, whereby the propagation of higher-order modes in the thickness direction inside the frame 2 is prevented.

Each of the through electrodes 5 and 6 is made of a conductive material that penetrates the frame 2 and the dielectric substrate 1 in the thickness direction thereof. The through electrode 5 short-circuits the top ground electrode 22 and the top electrode 23 of the coplanar line, and the through electrode 6 short-circuits the front ground 22 and the back electrode 21. The through electrodes 5 and 6 are arranged in the frame 2 and the dielectric substrate 1 at predetermined arrangement pitches d and d, respectively, in the direction along the signal propagation axis (the horizontal direction in FIG. 1B).

1 2

ing. Further, the through electrodes 5 and 6 are both symmetrically arranged with the signal propagation axis therebetween in a plane orthogonal to the signal propagation axis.

[0053] End surface conductors 10, 11 are formed on the end surface of the dielectric substrate 1 and the end surface of the frame 2, respectively. Each of the end face conductors 10 and 11 is a half-divided through electrode. Therefore, the end face conductor 10 short-circuits the front ground 22 and the back electrode 21, and the end face electrode 11 short-circuits the front ground 22 and the top electrode 2.

In the feed-through type optical module 100 of the present embodiment, the thickness t of the dielectric substrate 1, the thickness t of the frame 2, the arrangement pitch d of the through electrodes 5 and 6, d 1s With dimensions that satisfy

2 2 1

Is provided.

t <c / (4f- (sr -1) ^1/2 )

1 0 1

t <c / (4f- (sr -1) ^1/2 )

2 0 2

d <c / (4f- ε r ^1/2 )

1 0 1

d <c / (4f- ε r ^1/2 )

2 0 2

(Where c is the speed of light and f is the highest operating frequency used in this module.) In the feed-through type optical module 100 of the present embodiment, the thicknesses t and t of the dielectric substrate 1 and the frame 2 and the arrangement pitches d and d of the through electrodes 5 and 6 are defined as described above. . Further, the surface ground 25 and the upper surface electrode 22 are short-circuited by the end surface conductor 11. As a result, excitation and propagation of a higher-order mode and a parallel plate mode in the thickness direction propagating in the frame 2 are suppressed. As a result, the frequency response characteristics can be effectively improved. In addition, since the feedthrough is used as an electrical signal input / output interface, the module itself is smaller, has higher performance, and is less costly than a configuration that uses a coaxial connector that is large and is not suitable for automatic mounting. Done. Moreover, it can be expected to reduce the cost of mounting the module on the board. Specifically, this module 100 using feedthroughs can be expected to reduce costs and improve mass productivity by eliminating the need for additional components such as coaxial connectors and being able to be integrated with the package. .

(Second Embodiment)

FIG. 2 shows a feed-through type optical module according to a second embodiment of the present invention. FIG. 2A is a top view of the feed-through type optical module, and FIG. 2B is a side view thereof.

The feed-through type optical module 101 has a plurality of bumps 8 on the side wall surface of the package in addition to the configuration shown in FIG. Note that the side wall surface of the knockout is configured by positioning the outer peripheral surface of the dielectric substrate and the outer peripheral surface of the frame in the same plane. The side wall surface is formed parallel to the signal propagation axis (see Fig. 1). The bump 8 is electrically connected to a main line 25 and a surface ground 22 of a coplanar line, an optical element (not shown) and an electronic circuit (not shown) in the package via an electric wiring (not shown). RU

[0057] The plurality of bumps 8 are provided substantially in a lattice pattern at a predetermined pitch on the side wall surface.

Further, in order to secure the bonding strength with the printed circuit board, the bumps 8 are arranged at the same size and pitch as other bumps, and are not electrically connected to a specific signal line (not shown). The bumps 8 that are electrically connected to the signal lines are quasi-electromagnetically shielded by being surrounded by the bumps 8 having the same potential as the ground conductor.

The feed-through type optical module 101 configured as described above has the following advantages, unlike the conventional configuration in which bumps are formed on the bottom surface of the module. That is, Since no through-electrode (via) is interposed in the electric wiring connecting the element or the like in the semiconductor device and the bump 8, the effect of the discontinuity on the electric signal is further reduced.

A configuration in which the bumps 8 are provided on the side surfaces of the module as in the present embodiment is proposed, for example, in Japanese Patent Application Laid-Open No. 39037Z83. However, compared to the configuration of the document, the feed-through type optical module 101 of the present embodiment has a structure that reduces the characteristic deterioration caused by the parallel plate mode and the higher-order mode in the thickness direction generated by the feed-through. . Therefore, an improvement in frequency response characteristics can be expected due to their synergistic effect. Furthermore, when arranging the IC in the knockage, the plurality of bumps 8 provided on the side surface of the module as described above are advantageous in the following points. That is, since heat can be efficiently released from the back surface of the package, it is more advantageous than the conventional optical module with bumps in terms of improving the reliability as a module.

(Example 1)

In Example 1, based on the first embodiment described above, a 40 Gb / s receptacle-type receiving module was manufactured using a waveguide-type photodiode as an optical element. The package contained a waveguide-type pin photodetector, preamplifier IC, lens, and bias circuit.

[0061] Dielectric substrate 1 is made of a 95% pure alumina (a relative dielectric constant ε r) previously processed into a sheet shape.

= 9, substrate thickness t = 380 m). Alumina having a purity of 95% (relative permittivity εr = 9, substrate thickness t = 380 m) was used for the frame 2 as in the dielectric substrate 1. Here, the substrate thicknesses t and t are the same as the maximum used frequency of 50 GHz in the receiving module of the present embodiment.

1 2

The design is such that high-order modes do not occur in the thickness direction of the substrate inside each substrate. The thickness of the portion of the peripheral wall of the frame 2 that covers the coplanar line is 1.2 mm. That is, the coplanar line is partially covered with the frame 2 over a length of 1.2 mm in the longitudinal direction.

[0062] As the coplanar line, the width w of the main line 25 was 104 µm, the gap g was 58 µm, the characteristic impedance z was 50 Ω, and tungsten was used for the electrode as a high melting point conductive material.

0

. After plating, gold plating with a thickness of Lm was applied.

[0063] Tungsten was used for the through electrodes 5 and 6, the diameter φ was 150 µm, and the arrangement intervals d and d were used. Was set to 600 μm.

Further, in order to keep the characteristic impedance of the coplanar line constant in the longitudinal direction, near the portion where the main line 25 is hidden under the frame 2, the width w of the main line 25 is set to 108 m and the gap g ′ 7 with 56 μm.

FIG. 3B shows the small signal frequency response characteristics of the feedthrough in the receiving module configured as described above. The transmittance I S I indicated by the solid line is almost constant from DC to 50 GHz.

twenty one

It is flat and the insertion loss is within -ldB. In addition, the reflectance | s

Similarly, 11 I was 15 dB or less over DC power of 45 GHz, and practically sufficient wideband characteristics were obtained for mounting 40GbZs communication optical elements and ICs. On the other hand, a similar feedthrough structure was prototyped by removing only the upper conductor of frame 2, and its small signal frequency response characteristics were evaluated. As shown in Fig. 3A, the transmittance | S

21 I, reflectance I S

35 for both 11 I

A remarkable dip was observed near GHz. The characteristics of the receiving module itself are

, Bandwidth 40 GHz, transimpedance 6 (ΜΒΩ, light sensitivity 0.8 AZW), which also achieved sufficient characteristics for 40 GbZs applications.

(Example 2)

In Example 2, a receptacle-type receiving module similar to that of Example 1 was manufactured based on the above-described second embodiment. Note that the other configuration except for the bump 8 is the same as that of the first embodiment, and a description thereof will be omitted.

[0067] The diameter of each of the bumps 8 was set to 100 Pm, and the pitch between the adjacent bumps 8 in each of the two grid-like directions was set to about 500 m. The bumps 8

, The waveguide type pin photodetector and preamplifier I

It was configured to conduct to C, lens, bias circuit and the like.

[0068] The characteristics of the feed-through and the receiving module itself in the receiving module configured as described above are also the same as those in the first embodiment.

Claims

The scope of the claims

[1] A first dielectric substrate forming a coplanar line with a back surface electrode, and an opening is formed on at least the coplanar line disposed on the first dielectric substrate, and an upper surface electrode is formed on an upper surface. And a second dielectric substrate formed,

The first dielectric substrate includes a plurality of first through conductors that short-circuit the surface ground of the coplanar line and the back surface electrode,

The second dielectric substrate includes a plurality of second through conductors that short-circuit the surface ground and the upper surface electrode, and a plurality of second through conductors that intersect in a direction along a main line of the coplanar line. A feed-through structure formed on an end face and including a second end face conductor that short-circuits the surface ground and the upper surface electrode,

The relative dielectric constants of the first and second dielectric substrates are εr, εr,

1 2 f is the maximum operating frequency that the line propagates, and c is the speed of light

When set to 0,

Thicknesses t and t of the first and second dielectric substrates, respectively, and the main line

1 2

The respective arrangement pitches d, d of the first and second through conductors in the direction along the road are:

1 2

t <c / (4f- (sr -1) ^1/2 )

1 0 1

t <c / (4f- (sr -1) ^1/2 )

2 0 2

d <c / (4f- ε r ^1/2 )

1 0 1

d <c / (4f- ε r ^1/2 )

2 0 2

A feed-through structure characterized by satisfying the following.

[2] The arrangement pitch of the first through conductor and the arrangement pitch d of the second through conductor are the same, and the arrangement pitch d at that time is:

2

d <c / (4f- ε r ^1/2 ) (ε r: whichever is greater, ε r or ε r)

0 1 2

The feed-through structure according to claim 1, which satisfies the following.

[3] The first and second dielectric substrates are:

, 1/2. 1/2

t · ε r = t · ε r

1 1 2 2

3. The feed-through structure according to claim 1, which satisfies the following.

[4] The first dielectric substrate, wherein the first dielectric substrate intersects in a direction along the main line. A first end surface conductor formed on an end surface of the substrate and short-circuiting the front surface ground and the back electrode, further comprising:

The first end surface conductor is symmetrically disposed within the end surface of the first dielectric substrate with the main line therebetween.

The second end surface conductor is symmetrically arranged within the end surface of the second dielectric substrate with the main line therebetween.

The distance d between the first end face conductors and the distance d between the second end face conductors are:

11 12 Each

d ≤c / (2f-ε r ^1/2 )

11 0 1

d ≤c / (2f-ε r ^1/2 )

12 0 2

Satisfy, claim 1! 3. The feed-through structure according to any one of items 1 to 3 above.

5. The feedthrough according to claim 4, wherein the first and second end surface conductors are provided by dividing a through conductor penetrating the first and second dielectric substrates. One structure.

[6] Any one of claims 1 to 5, wherein the first dielectric substrate and the second dielectric substrate have the same thicknesses t, t and are made of the same material. Described in

2

Feedthrough structure.

7. The feed-through structure according to claim 6, wherein the first dielectric substrate and the second dielectric substrate are also made of any one of ceramic, glass, and resin.

[8] The feed-through structure according to any one of claims 1 to 5, wherein the first dielectric substrate and the second dielectric substrate have substantially equal linear expansion coefficients. .

9. The method according to claim 1, wherein the first dielectric substrate and the second dielectric substrate are made of a material excellent in airtightness and water resistance. Feedthrough structure.

[10] The feed according to claim 1, wherein the first dielectric substrate and the second dielectric substrate also have a material strength capable of brazing a metal material. Through structure.

[11] The feed-through structure according to claim 1, wherein a plating is applied to at least a part of the main line and the surface ground of the coplanar line. body.

[12] The feed-through structure according to claim 1, wherein a force enabling wire bonding or a bump can be formed on the electrode surface.

[13] The feed-through structure according to any one of claims 1 to 12, wherein a lead electrode is provided on the electrode surface.

[14] At least one of the outer peripheral surfaces of the first dielectric substrate and at least one of the outer peripheral surfaces of the second dielectric substrate are in the same plane. The feed-through structure according to item 1.

[15] A plurality of bumps are formed on each of the outer peripheral surfaces of the first and second dielectric substrates in the same plane,

15. The feed-through structure according to claim 14, wherein the plurality of bumps are configured to conduct to a high-frequency circuit component disposed in the opening of the second dielectric substrate.

16. The feed-through structure according to claim 15, wherein the outer peripheral surface on which the plurality of bumps are formed is parallel to a direction along the main line.

[17] The feed-through structure according to any one of claims 1 to 16, wherein the coplanar lines are arranged in an array.

[18] The feed-through structure according to any one of claims 1 to 17, and

A feed-through type optical module, comprising: a high-frequency circuit component disposed on the first dielectric substrate and in the opening of the second dielectric substrate.