JP2009151053A - Light receiving module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light receiving module with excellent productivity without requiring transfer mold, by suppressing adverse affect on a high frequency signal and high speed response due to parasitic impedance. <P>SOLUTION: The light receiving module includes: a pre-amplifier circuit chip 3 in which a light receiving element 2 is mounted in a flip chip form; accommodation sections 8a and 8b for accommodating the light receiving element 2 and the pre-amplifier circuit chip 3; a package 4 including a transmission aperture 7 of signal light which the light receiving element 2 receives, wiring conductors and electrodes; and a sleeve 9 for connecting and holding an optical fiber. The pre-amplifier circuit chip 3 is mounted in the flip chip form on the electrodes of the package 4, and the sleeve 9 is adjusted so that the signal light from the optical fiber may be received by the light receiving element 2 and is fixed to the package 4. The package 4 is formed by stacking a plurality of ceramic substrates, and the transmission aperture 7 of the signal light is sealed by a sealing plate 5 which has translucency for a predetermined light wavelength. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a light receiving module used for optical fiber communication.

  In high-speed optical fiber communication, a light receiving element having high-speed response and high light receiving sensitivity is required. In particular, in order to realize high-speed response, a structure has been proposed in which the light receiving element is flip-chip mounted to reduce the inductance component due to the bonding wire, the propagation of the generated magnetic field, and the like. In addition, while satisfying the high-speed response of optical fiber communication, downsizing and cost reduction are also important.

In response to these requirements, for example, Patent Document 1 discloses that an optical element is flip-chip mounted on a substrate having a wiring film and a translucent resin film, thereby reducing the size and improving the high-frequency characteristics. An optical communication module having a structure hermetically sealed by a mold and protected is disclosed. Patent Document 2 discloses a light receiving element having a structure suitable for flip chip mounting. Further, Patent Document 3 discloses that a light receiving element and a light emitting element are flip-chip mounted on a circuit chip.
JP 2004-361630 A JP-A-5-37005 JP-A-10-112553

In the optical communication module disclosed in Patent Document 1, a plurality of optical elements are flip-chip mounted by alignment adjustment, and then divided into modules by dicing. However, due to its structure, a transfer mold for sealing is required, but mass productivity is poor because it is performed by a mold for each individual module. In order to increase mass productivity, it is necessary to transfer mold a plurality of modules at once, but this increases the size of the mold and increases the capital investment.
Further, as disclosed in Patent Document 3, a high-speed signal response can be expected by mounting a light receiving element or a light emitting element on a circuit chip by flip chip connection. However, there is room for improvement since the circuit chip and the wiring board have a wire connection structure.

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a high-productivity light-receiving module that suppresses adverse effects on high-frequency signals and high-speed responses due to parasitic impedance and does not require a transfer mold.

  The light-receiving module according to the present invention has a preamplifier circuit chip on which the light-receiving element is flip-chip mounted, a receiving portion for receiving the light-receiving element and the pre-amplifier circuit chip, a transmission port for signal light received by the light-receiving element, and a wiring conductor and A package having an electrode; and a sleeve for connecting and holding the optical fiber. The preamplifier circuit chip is mounted on the electrode of the package by flip chip mounting, and the sleeve is aligned and fixed to the package so that signal light from the optical fiber is received by the light receiving element. The package can be formed by stacking a plurality of ceramic substrates, and the signal light transmission port can be sealed with a sealing plate having a light-transmitting property with respect to a predetermined light wavelength.

  In the light receiving module according to the present invention, the light receiving element includes a condensing lens on a light incident surface side, and a light receiving portion and an electrode for flip chip mounting on a surface side opposite to the light incident surface. Can do. In addition, the preamplifier circuit chip can be configured to include an electrode for flip-chip mounting on the package and an electrode for flip-chip mounting the light receiving element in the same plane. Further, the housing space in which the preamplifier circuit chip is housed can be configured to be filled with sealing resin.

According to the present invention, the connection electrode surface of the light receiving element, the connection electrode surface of the preamplifier circuit chip, and the wiring conductor surface for chip mounting formed in the package can be configured to face the same surface. All electrical connections between these components can be flip-chip mounted. As a result, electrical connection by wire connection can be omitted, a decrease in high frequency response due to floating impedance can be suppressed, and a light receiving module having excellent high frequency characteristics can be realized.
In addition, since it does not require a transfer mold, it does not require the use of a mold, can be assembled in a matrix using a large package, and can provide an inexpensive and highly productive light receiving module. It becomes.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1A is a perspective view for explaining the outline of a light receiving module according to the present invention, and FIG. 1B is a sectional view thereof. In the figure, 1 is a light receiving module, 2 is a light receiving element, 3 is a preamplifier circuit chip, 4 is a package, 5 is a sealing plate, 6 is a sealing resin material, 7 is a signal light transmission port, and 8a and 8b are accommodating portions. , 9 is a sleeve, 9a is a flange portion, and 9b is an insertion hole of the optical connector.

  A light receiving module 1 according to the present invention includes a preamplifier circuit chip 3 on which a light receiving element 2 such as a photodiode (PD) is mounted, and a package 4 (hereinafter simply referred to as a package) having a wiring conductor and electrodes on which the preamplifier circuit chip 3 is mounted. And a sleeve 9 fixed to the package 4 by adhesion or the like. The preamplifier circuit chip 3 converts the photocurrent received by the light receiving element 2 into a voltage signal by the preamplifier circuit. This preamplifier circuit is required to have a low noise and a wide dynamic range, and usually a transimpedance preamplifier (TIA) in which a feedback resistor is inserted between the input part and the output part of the amplifier is used. . This TIA circuit is provided as a preamplifier circuit chip 3 as an integrated rectangular chip-shaped component.

  As will be described later, the light receiving element 2 has a shape that can be flip-chip mounted on the preamplifier circuit chip 3, and is connected and mounted on the central portion of the preamplifier circuit chip 3. The package 4 includes housing portions 8 a and 8 b for housing the preamplifier circuit chip 3 and the light receiving element 2, and includes a transmission port 7 for signal light received by the light receiving element 2. Further, the signal light transmission port 7 can be sealed with a sealing plate 5 made of a material that is transparent to a predetermined light wavelength.

  A wiring conductor is formed on the upper surface side of the step portion of the accommodating portion 8a provided in the package 4, and the preamplifier circuit chip 3 on which the light receiving element 2 is mounted is mounted on the wiring conductor by flip chip mounting. The housing portion 8a of the package 4 in which the preamplifier circuit chip 3 is housed can be hermetically sealed by being filled with a sealing resin material 6 as necessary. In addition, when the sealing resin material 6 has translucency with respect to a predetermined light wavelength, the light emitting element 2 is accommodated, and the accommodating portion 8b sealed with the sealing plate 5 can be filled. it can.

  The sleeve 9 is for fitting and holding an optical connector for connecting an optical fiber, and is fixed to the package 4 with an adhesive or the like by a flange portion 9a. A ferrule (not shown) of an optical connector attached to the end of the optical fiber is inserted into the optical connector insertion hole 9b of the sleeve 9, and signal light from an external device is emitted toward the light receiving element 2. Is done. When adhering to the package 4, the signal light emitted from the optical fiber is aligned and positioned so that the light receiving element 2 can efficiently receive the signal light.

  2A and 2B are diagrams for explaining the outline of the light receiving element and the preamplifier circuit chip. FIG. 2A is a diagram illustrating an example of the light receiving element, and FIG. 2B is a diagram illustrating a mounting surface of the preamplifier circuit chip. In the figure, 10 is a light receiving portion, 11a and 11b are electrode leads of the light receiving element, 12 is a solder bump of the light receiving element, 13 is a monolithic lens, 14 is an electrode of the circuit chip, and 15 is a connection electrode of the circuit chip.

  The light receiving element 2 has a shape capable of flip chip mounting as shown in FIG. 2A (for example, a light receiving element as disclosed in Patent Document 2). The light receiving element 2 has a light receiving part 10 at the center, and on the mounting surface 2a side where the light receiving part 10 is in contact, solder bumps 12 are formed at the end portions of the electrode leads 11a and 11b of the light receiving element. Or a printing method or the like. A monolithic lens 13 is formed as a condensing lens on the light incident surface 2b side where the signal light facing the light receiving unit 10 is incident, and the signal light from the optical fiber on the optical axis of the lens 13 is formed. Is condensed on the light receiving unit 10.

  The preamplifier circuit chip 3 is formed of, for example, a transimpedance type preamplifier (TIA) (circuit configuration is omitted), and an electrode 14 for directly mounting the above-described light receiving element 2 by flip chip connection at the center of the mounting surface 3a. Is formed. In addition, the mounting surface 3a of the preamplifier circuit chip 3 is further provided with a connection electrode 15 for connection to a next-stage amplifier circuit or the like via a package 4 described later. The connection electrodes 15 are formed of solder bumps in order to mount the preamplifier circuit chip 3 on the package 4 by flip chip connection.

  FIG. 3 is a diagram for explaining an example in which the preamplifier circuit chip 3 on which the light receiving element 2 described above is flip-chip mounted is mounted on the base substrate 20 stacked in the middle of the package 4 by flip-chip connection. As described with reference to FIG. 2B, the light receiving element 2 is flip-chip mounted on the preamplifier circuit chip 3 so as to protrude from the mounting surface 3 a of the preamplifier circuit chip 3. For this reason, the base substrate 20 on which the preamplifier circuit chip 3 is mounted is formed with an accommodation opening 20 a for accommodating the light receiving element 2.

  In addition, a wiring conductor 17 for connecting the preamplifier circuit chip 3 to an external circuit such as the next stage amplification is formed on the wiring conductor surface 16 of the base substrate 20. The electrode 17a inside the wiring conductor 17 is arranged around the receiving opening 20a in which the light receiving element 2 is accommodated, and the connection electrode 15 formed by the solder bump of the preamplifier circuit chip 3 is flip-chip connected. The electrode 17b outside the wiring conductor 17 is arranged on the periphery of the base substrate 20 and used for connection with an external circuit. The light receiving element 2 is accommodated in a floating state in the accommodating opening 20a.

According to the above configuration, the connection electrode surface (mounting surface 2 a) of the light receiving element 2, the connection electrode surface (mounting surface 3 a) of the preamplifier circuit chip 3, and the wiring conductor surface 16 are flush with the base substrate 20 of the package 4. Therefore, all the electrical connections between these components can be flip-chip connected as described above.
In addition, the wiring conductor 17 of the base substrate 20 is formed to have a predetermined characteristic impedance with a predetermined conductor width and thickness, and does not use a three-dimensional wiring such as wire connection. Degradation is reduced, and high-speed transmission with little signal degradation can be realized.

  FIG. 4 is a diagram illustrating a configuration example in which the above-described package is formed by stacking, in which 18 and 19 are side electrodes, 20 is a base substrate, 21 is a first support substrate, 21a is an accommodation opening, and 22 is The second support substrate, 23 is the first cover substrate, 23a is the accommodation opening, 24 is the second cover substrate, 24a is the accommodation opening, and the other symbols are the same as those used in FIGS. Therefore, the description is omitted.

  The package according to the present invention includes a wiring conductor, an electrode, and the like that are mounted on the package so as to be connectable to an external device while protecting the composite circuit chip and the like from an external force or the like. The package used in the present invention can be formed by stacking a plurality of substrates as shown in FIG. Each of the substrates to be stacked can be formed of, for example, a ceramic with good workability such as alumina, and a material with high thermal conductivity such as aluminum nitride with excellent heat dissipation.

  In the package 4, a substrate provided with the wiring conductor 17 and the electrodes 17 a and 17 b as described with reference to FIG. Then, a support substrate is laminated on the lower surface side, and a cover substrate is laminated on the upper surface side. When a ceramic substrate is used as the base substrate 20, the wiring conductor 17 is preferably formed of a thin film such as Ti / Pt / Au in consideration of adhesion to the ceramic substrate.

  The support substrate provided on the lower surface side of the base substrate 20 can be formed using, for example, two substrates, a first support substrate 21 and a second support substrate 22. The first support substrate 21 in contact with the base substrate 20 is formed with an accommodation opening 21 a communicating with and passing through the accommodation opening of the base substrate 20, and the second support substrate 22 is formed with a signal light transmission port 7. The The signal light transmission port 7 may be sealed with a sealing plate 5 made of a material that is transparent to a predetermined light wavelength.

  By sealing the signal light transmission port 7 with the sealing plate 5, the light receiving element 2 and the preamplifier circuit chip 3 mounted in the substrate are protected from being exposed to the surrounding air and moisture, and the deterioration is suppressed. It becomes possible to do. The sealing plate 5 is made of quartz, silicate glass, or other ceramic that is transparent to a predetermined light wavelength. The second support substrate 22 is formed of a ceramic that is transparent to a predetermined light wavelength, so that the formation of the transmission port 7 and the sealing plate 5 can be omitted.

  The cover substrate provided on the upper surface side of the base substrate 20 has a function of protecting the preamplifier circuit chip 3 mounted on the base substrate 20 from an external force. For example, the first cover substrate 23 and the second cover substrate 24 include It can be formed using two substrates. The first cover substrate 23 in contact with the base substrate 20 is formed with an accommodation opening 23a for accommodating the preamplifier circuit chip 3 mounted on the base substrate 20 at the center. The second cover substrate 24 is formed in the same shape as the first cover substrate 23, and similarly has an accommodation opening 24 a for the preamplifier circuit chip 3 at the center.

  Side electrodes 18 and 19 that form an electrical connection with the electrode 17b on the base substrate 20 can be formed in the semicircular recesses on the side edges of the first and second cover substrates 23 and 24, respectively. The side electrodes 18 and 19 are formed at positions corresponding to the electrodes 17b outside the wiring conductor 17 of the base substrate 20, and are electrically connected by a solder material or the like. The preamplifier circuit chip 3 is connected to the external circuit through the side electrodes 18 and 19. The number of stacked layers of the cover substrate is adjusted according to the height dimension of the preamplifier circuit chip 3 mounted on the base substrate 20.

  FIG. 5 is a diagram showing a state in which the light receiving element 2 and the preamplifier circuit chip 3 are mounted on the package 4. FIG. 5A shows a state in which the sealing resin material is not filled, and FIG. 2 is a view showing a form in which the light receiving element 2 and the preamplifier circuit chip 3 are hermetically sealed. FIG. Although it can be used in a form in which the sealing resin material is not filled, as shown in FIG. 5 (B), the signal light transmission port 7 is sealed with the sealing plate 5 and the first and second cover substrates. An adhesive sealing resin material 6 is filled in a space between the housing portion 8 a formed by the housing openings 23 and 24 and the preamplifier circuit chip 3.

  The sealing resin material 6 may be filled so as to reach at least the position of the exposed surface 3b of the preamplifier circuit chip 3, but may be filled so as to completely cover the exposed surface 3b of the preamplifier circuit chip 3. . Further, the light receiving element 2 and the preamplifier circuit chip 3 are completely hermetically sealed by bonding or adhering between the laminated surfaces of the plurality of substrates constituting the package 4. When a light-transmitting material is used for the sealing resin material 6, the sealing resin material 6 may also be filled into the housing portion 8 b of the light receiving element 2.

  6 to 8 are diagrams for explaining a configuration example suitable for adjusting the characteristic impedance of the signal line. 6 is a diagram showing an example in which both sides of a signal line are sandwiched between ground lines, FIG. 7 is a diagram showing an example in which a ground line for impedance adjustment is provided on a substrate adjacent to the substrate on which the signal line is formed, and FIG. It is a figure which shows the example which provides the ground line for impedance adjustment in the upper and lower board | substrates adjacent to the board | substrate with which the signal line is formed. In the figure, 26 is a base substrate, 27 is a support substrate, 28 is a cover substrate, 29 is a signal line, and 30a to 32 are ground lines.

  As shown in FIG. 6, ground lines 30 a and 30 b are arranged so that the signal line 29 is sandwiched from both sides on the base substrate 26 by wiring conductors formed on the base substrate 26 on which the preamplifier circuit chip and the like are mounted. By changing the separation distance between the signal line 29 and the ground lines 30a and 30b, the capacitance of the signal line 29 can be adjusted and impedance matching with an external circuit can be achieved.

  In addition, as shown in FIG. 7, a ground line 31 is provided on a support substrate 27 bonded to the lower surface side of the base substrate 26 on which the signal line 29 is formed so as to face the signal line 29, thereby providing a microstrip line. Form. By changing the width or the like of the ground line 31, the capacitance of the signal line 29 can be adjusted to achieve impedance matching with an external circuit.

  In addition, as shown in FIG. 8, a ground line 31 is provided on the support substrate 27 bonded to the lower surface side of the base substrate 26 on which the signal line 29 is formed so as to face the signal line 29, and the base substrate 26 is provided. A ground line 32 is provided on the cover substrate 28 bonded to the upper surface side of the cover substrate 28 so as to face the signal line 29 to form a microstrip line. By changing the width or the like of the ground lines 31 and 32, the capacitance of the signal line 29 can be adjusted to achieve impedance matching with an external circuit.

  FIG. 9 is a diagram illustrating a configuration example in which electromagnetic shielding is performed on a preamplifier circuit chip mounted in a package. In the figure, 4 'is a package, 26' is a base substrate, 27a and 27b are support substrates, 28a and 28b are cover substrates, 33a and 33b are surface layer ground lines, and 33c is an inner layer ground line.

  As shown in FIG. 9, the package 4 'includes a base substrate 26', first and second support substrates 27a and 27b, and first and second cover substrates 28a and 28b, as described in FIG. Are stacked, and a ground line (ground conductor) is formed in the periphery of each of the stacked substrates. A surface ground line 33a is formed on the entire surface of the support substrate 27b, which is the outermost substrate, excluding the signal light transmission port, and the cover substrate 28b, which is the other outermost substrate, is similarly formed. A surface ground line 33b is formed on almost the entire surface excluding the accommodation opening of the preamplifier circuit chip 3.

In each substrate of the package 4 ′, an inner layer ground line 33 c is formed in a loop shape around the substrate (not necessarily closed) on either one of the substrates to be laminated on the laminated surface that is not exposed to the outer surface. Is done. The surface layer ground lines 33a and 33b and the inner layer ground line 33c formed on each substrate are electrically connected by a via hole 34 or the like penetrating each substrate.
Thereby, the light receiving element 2 and the preamplifier circuit chip 3 mounted in the package 4 ′ can be electromagnetically shielded, and it is possible to eliminate malfunction by absorbing electromagnetic noise from the outside. Further, it is possible to suppress leakage of a signal generated in the preamplifier circuit chip 3 outside the package 4 ′.

In addition, in FIG. 1 to FIG. 9 described above, the example in which the light receiving module product is individually manufactured has been described.
A large-sized substrate having each laminated substrate (20 to 21 or 26 'to 28b) arranged in a matrix is laminated, and a large number of packages 4 and 4' are formed in a matrix. Next, this is divided into individual packages by dicing, and the sealing plate 5 is attached through the package receiving openings 21a, 23a, and 24a. Further, the preamplifier circuit chip 3 on which the light emitting element 2 is mounted is mounted on the base substrates 20 and 26 'through the housing openings 23a and 24a, and then the sealing resin material 6 is filled into the housing openings to form a light receiving module. In addition, the part used as the side electrode of the cover substrates 23 and 24 is formed by a through conductor (a through hole or a via hole), and becomes a side electrode by cutting.

  In addition, before dividing into individual packages as described above, the sealing plate 5, the preamplifier circuit chip 3, and the sealing resin material 6 are filled to integrally form a plurality of light receiving module products. Next, it may be cut into individual light receiving module product units by dicing, and then an optical fiber connecting sleeve may be attached to form a finished product. According to this method, it is possible to provide a light receiving module that is inexpensive and has high productivity.

FIG. 10 is a diagram showing an example of usage of the light receiving module according to the present invention. The light receiving module 1 according to the present invention is completed by fixing a sleeve 9 to the package 4 with an adhesive as described with reference to FIG. When the sleeve 9 is bonded and fixed, with the ferrule of the optical connector inserted in the insertion hole 9b of the sleeve 9, the package 4 is slid on the flange portion 9a of the sleeve 9 so that the light receiving element can obtain high optical coupling. To align. As the adhesive, it is desirable to use an ultraviolet curable adhesive so that it can be bonded and fixed immediately after alignment.
The completed light receiving module 1 may be directly mounted on a circuit board or the like, but may be electrically connected using a flexible circuit board 25.

It is a figure explaining the outline of the light reception module by this invention. It is a figure explaining the light receiving element and preamplifier circuit chip which are used by this invention. It is a figure explaining the base substrate and mounting example which are used by this invention. It is a figure explaining the structural example of the package in this invention. It is a figure which shows the state which mounted the light receiving element and the preamplifier circuit chip in the package in this invention. It is a figure which shows the structural example which adjusts the characteristic impedance of a signal wire | line in this invention. It is a figure which shows the other structural example which adjusts the characteristic impedance of a signal wire | line in this invention. It is a figure which shows the other structural example which adjusts the characteristic impedance of a signal wire | line in this invention. It is a figure which shows the structural example which electromagnetically shields by this invention. It is a figure which shows an example of the usage condition of the light reception module by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Light receiving module, 2 ... Light receiving element, 2a ... Mounting surface, 2b ... Light incident surface, 3 ... Preamplifier circuit chip, 3a ... Mounting surface, 3b ... Exposed surface, 4, 4 '... Package, 5 ... Sealing plate, 6 ... sealing resin material, 7 ... signal light transmission port, 8a, 8b ... accommodating portion, 9 ... sleeve, 9a ... flange portion, 9b ... insertion hole, 10 ... light receiving portion, 11a, 11b ... electrode lead, 12 DESCRIPTION OF SYMBOLS ... Solder bump, 13 ... Monolithic lens (condensing lens), 14 ... Electrode, 15 ... Connection electrode, 16 ... Wiring conductor surface, 17 ... Wiring conductor, 17a ... Inner electrode, 17b ... Outer electrode, 18, 19 ... Side electrodes, 20 ... base substrate, 21 ... first support substrate, 21a ... accommodation opening, 22 ... second support substrate, 23 ... first cover substrate, 23a ... accommodation opening, 24 ... second cover substrate, 24a ... accommodating opening, 25 ... flexible circuit board, 6, 26 '... base substrate, 27, 27a, 27b ... supporting substrate, 28, 28a, 28b ... cover substrate, 29 ... signal line, 30A～33b ... ground line, 34 ... via hole.

Claims (7)

A preamplifier circuit chip on which a light receiving element is flip-chip mounted, a receiving part for receiving the light receiving element and the preamplifier circuit chip, a package having a transmission port for signal light received by the light receiving element, and a wiring conductor and an electrode; A sleeve for connecting and holding the optical fiber,
The preamplifier circuit chip is mounted on the electrode of the package by flip chip mounting, and the sleeve is aligned and fixed to the package so that signal light from an optical fiber is received by the light receiving element. Receiving module.   The light receiving module according to claim 1, wherein the package is formed by stacking a plurality of ceramic substrates.   The light receiving module according to claim 1, wherein the signal light transmission port is sealed with a sealing plate having a light transmission property with respect to a predetermined light wavelength.   The light receiving module according to claim 1, wherein the light receiving element includes a condensing lens on a light incident surface side.   The light receiving module according to claim 4, wherein the light receiving element includes a light receiving portion and a flip chip mounting electrode on a surface opposite to the light incident surface.   6. The preamplifier circuit chip includes an electrode for flip-chip mounting on the package and an electrode for flip-chip mounting the light receiving element in the same plane. The light receiving module according to item 1.   The light receiving module according to claim 1, wherein a sealing resin is filled in the housing portion in which the preamplifier circuit chip is housed.

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