JP2004047822A - Optical module and optical module assembly using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical module and an optical module assembly that are suited to mounting of an optical element of surface type semiconductor element and excel in mass-productivity, and is compact and superior in high-frequency characteristic. <P>SOLUTION: The optical module M1 is provided with a VCSEL 2 and an optical waveguide body (optical fiber 42 and ferrule 41 housing the same) connecting electrically with the VCSEL 2 that is fitted th the arrangement surface 16 side of the VCSEL 2 of a substrate 1 where a wiring is formed to energize the VCSEL 2. Sides excluding the arrangement surface 16 of the VCSEL 2 of the substrate 1 and its rear surface 20, that is, any of sides of the substrate 1 is fixed onto an external circuit substrate (not illustrated) where an external wiring is formed to energize the VCSEL 2, thus electrically connecting the external wiring formed thereon with a wiring formed on the substrate 1. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a technology for mounting a surface-type optical semiconductor element such as a VCSEL (Vertical Cavity Surface Emitting Laser), a PIN type photodiode, or an avalanche photodiode. For example, the present invention relates to such a surface-type optical semiconductor element and its operation. The present invention relates to an optical module having a wide band, small size and high reliability, and an optical module assembly having the electronic component mounted on an external circuit board.
[0002]
[Prior art]
In recent years, large-capacity optical fiber communication has been widely spread and developed in the field of public communication and private communication (LAN). Accordingly, the transmission speed has been increased, and even at close distances of up to about 500 meters, high-speed optical transmission using optical fibers is required. In addition, the importance of very short-range (Very Short Reach; VSR) optical transmission and applications called Gigabit Ethernet (R) (GbE) is increasing. In these applications of VSR and GbE, an optical transmission speed of 10 gigabits per second is being required. In such transmission, an unspecified number and various kinds of uses are assumed, and a large amount of equipment is required as compared with the conventional one. It is considered that miniaturization and improvement of mass productivity are important in industry.
[0003]
In conventional optical communication systems, semiconductor lasers in the 1.55 micron or 1.33 micron band, in which the loss and dispersion of optical fibers are small, have been widely and generally used. As a new optical semiconductor device having excellent characteristics and capable of high-speed optical transmission, a surface light emitting element called VCSEL of 0.85 micron band has been used. On the other hand, a light receiving element such as a PIN photodiode and an avalanche photodiode are used as a light receiving element of a VCSEL in order to electrically convert a high-speed optical signal as in the related art.
[0004]
In a LAN or the like using Gigabit Ethernet (R), a form of an optical transceiver in which a transmitter and a receiver are packaged in one is generally used as disclosed in, for example, JP-A-2000-214351. The size is also standardized. In recent years, downsizing of optical transceivers has been progressing in order to downsize the entire device, and the configuration has been changed to a form called SFF (Small Form Factor) which is about half the size of the conventional one. In general, these surface-type optical semiconductor elements are housed in a cylindrical housing formed by a metal housing called a TO-CAN package and a lead pin to form an optical module, and an electronic module on which an electronic circuit for controlling the optical module is mounted. It is mounted and fixed on a circuit board.
[0005]
[Problems to be solved by the invention]
However, in the conventional TO-CAN type optical module package, when the lead pins of the optical module package are mounted on an electronic circuit board on which an electronic circuit is mounted, the lead pins are airborne between the optical module package and the electronic circuit board. Since the wires are wired, the discontinuity of the characteristic impedance of the wires is large, and the high-frequency characteristics are deteriorated.
[0006]
In order to solve this problem, it is conceivable to shorten the lead pins as much as possible so that the lead pins are not exposed to the air and mount them on an electronic circuit board. It is difficult to secure the period reliability, and the high frequency characteristics are not stable due to variations in the length of the lead pins and variations in the amount of solder when the optical module is mounted and fixed, resulting in poor mass productivity. Further, since the TO-CAN type optical module package is standardized to φ5.6 mm, further miniaturization is difficult.
[0007]
Also, since the lead pins are arranged concentrically from the center of the package, in order to mount them on an electronic circuit board, bend them in the middle of the lead pins, make holes in the electronic circuit board, insert the lead pins, and solder them. It is a structure that is not suitable for the electronic component mounting process and has poor mass productivity.
[0008]
Therefore, the present invention has been proposed in view of the above-described problems, and is particularly suitable for mounting a surface-type optical semiconductor element, and has excellent mass productivity, small size, excellent high-frequency characteristics, and a reliable optical module. An object is to provide an optical module assembly using the same.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, an optical module according to the present invention comprises: a substrate having a surface-type optical semiconductor element provided thereon and a wiring formed thereon for supplying current to the surface-type optical semiconductor element; In addition to attaching an optical waveguide to be connected, an external wiring for energizing the surface optical semiconductor element was formed on a surface of the base except for the surface on which the surface optical semiconductor element was disposed and the back surface thereof. It is fixed to an external circuit board so that the external wiring formed on the external circuit board and the wiring formed on the base can be electrically connected.
[0010]
In the above structure, it is preferable that an internal wiring is formed in the base so as to electrically connect the surface type optical semiconductor element to an external wiring formed on the external circuit board. Further, it is preferable that a support made of metal for supporting the optical waveguide is provided on the surface of the base on which the planar optical semiconductor element is provided.
[0011]
The optical waveguide includes an optical fiber and a ferrule holding the optical fiber.
[0012]
Further, an optical module assembly according to the present invention is characterized in that any one of the above-mentioned optical modules is mounted on the external circuit board via solder.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of an optical module and an optical module assembly using the same according to the present invention will be described in detail with reference to the drawings schematically showing the embodiments.
[0014]
FIG. 1 is a perspective view of an optical module M1 according to the present invention, FIG. 2 is an exploded perspective view of the optical module M1, and FIG. 3 is a view for explaining a wiring structure and the like in a base 1 portion constituting the optical module M1 according to the present invention. FIG. 4 is a perspective view, FIG. 4 is a perspective view showing a VCSEL 2 which is a planar optical semiconductor element constituting the optical module M1, FIG. 5 is a perspective view showing a state of a base 1 part constituting the optical module M1, and FIG. It is sectional drawing cut | disconnected by the surface containing the optical axis of the optical waveguide which comprises the optical module M1.
[0015]
The optical module M1 of the present invention includes an optical waveguide (mainly an optical fiber 42 and an optical fiber 42) for optically connecting to the VCSEL 2 on the VCSEL 2 mounting surface 16 side of the base 1 on which the VCSEL 2 is provided and wiring for supplying electricity to the VCSEL 2 is formed. (Consisting of a ferrule 41 for accommodating and holding this). An external circuit (not shown) in which external wiring for supplying current to the VCSEL 2 is formed on a surface of the substrate 1 excluding the surface 16 on which the VCSEL 2 is disposed and the back surface 20, that is, any one of the side surfaces of the substrate 1. It is fixed to a substrate so that the external wiring formed on the external circuit board and the wiring formed on the base 1 can be electrically connected.
[0016]
Further, in the base 1, internal wirings (12b, 13b, 13c, 12c, 13d) for electrically connecting the VCSEL 2 and the external wiring formed on the above-mentioned external circuit board are formed as described later. ing. Further, the base 1 is provided on the surface 16 on which the VCSEL 2 is disposed, with a support made of metal for supporting the optical waveguide, that is, a metal fitting 17, a first metal protector 4, and a second metal protector. A body 9 is provided. Here, in the drawing, the lead electrodes 14, 15a, and 15b having a coplanar structure are provided on the surface 30 of the base 1 that is fixed to the external circuit board (the mounting surface of the optical module on the external circuit board). Instead of the lead electrodes, a terminal electrode group including a plurality of grid-shaped terminal electrodes may be formed in at least three regions. This terminal electrode group is formed along the optical axis direction of the optical waveguide.
[0017]
More specifically, as shown in the figure, in the optical module M1, the VCSEL 2 is disposed on one main surface 16 of the base 1, which is a base for mounting optical components, and the same main surface 16 of the base 1 surrounds the VCSEL 2 and forms a circle. An annular metal fitting 17 is provided, and a metal annular body 3 having the lens 34 provided at the center thereof is attached to the metal fitting 17 in a state in which a spherical lens 34 is closed in an upper opening of the metal fitting 17. The first metal protector 4 having a cylindrical shape and a flange portion 4a formed on one end side is disposed on the metal fitting 17 so as to cover the metal ring 3 over the metal fitting 17. It is arranged so that 4a is on the base 1 side. Further, a circle in which an optical fiber 42 for optically connecting to the VCSEL 2 is disposed inside a second metal protector 9 having a cylindrical shape and a flange 9a formed at one end in the same manner as the first metal protector 4. The columnar ferrule 41 is accommodated, and the second metal protector 9 is accommodated in the first metal protector 4. As described above, the first and second metal protectors 4 and 9 are provided with the flange portions 4a and 9a, so that an optical connector receptacle (not shown) can be fitted.
[0018]
In the base 1, electrode patterns 12a and 13a for transmitting an electric signal to the VCSEL 2 are formed on the arrangement surface 16 of the VCSEL 2. These electrode patterns 12a, 13a are electrically connected by via conductors 12b, 13b, 13c of internal wiring formed inside the base 1. Further, lead electrodes 14, 15a, 15b, which are external pads for electrical connection to the outside, are provided on a surface 30 that is the lower surface side when the base 1 is erected, and are electrically connected to each of these lead electrodes. External conductive patterns 18 and 19 are formed on a surface 30 of the base 1 on the side provided on the external circuit board. Each of these external conductive patterns 18 and 19 is connected to internal conductor patterns 12c and 13d formed inside the base 1, and these internal conductor patterns 12c and 13d are connected to the via conductors 12b, 13b and 13c, respectively. It is connected to the.
[0019]
The electrode patterns 12a and 13a, the via conductors 12b, 13b and 13c, and the internal conductor patterns 12c and 13d are high-frequency lines for transmitting 10 Gbps electric signals. In particular, the electrode patterns 12a and 13a and the internal conductor patterns 12c and 13d is a coplanar electric wiring whose impedance is matched to 25Ω or 50Ω or the like, and the lead electrodes 14, 15a and 15b are formed in a grid array in which three electrodes of a ground electrode, a signal electrode and a ground electrode are arranged. It is preferable to use a coplanar electrode, and this configuration enables high-speed transmission of 10 Gbps.
[0020]
Here, by using a ball-shaped grid array to which solder balls are added instead of the lead electrodes 14, 15a, and 15b, the convenience in mounting the optical module M1 can be further improved.
[0021]
The base 1 has a multilayer wiring structure in which a ceramic material such as alumina or aluminum nitride is laminated, and the electrode patterns 12a and 13a and the internal conductor patterns 12c and 13d are made of Au, Ni, W, or the like. A conductor thick film containing at least is formed by printing or the like, or is made of metallization such as Cu, and the via conductors 12b, 13b, 13c are made of W or the like.
[0022]
The metal fitting 17 is made of Kovar or the like, and is brazed to the base 1. Further, the metal annular body 3 provided with a lens 34 made of Kovar or stainless steel or the like has a hermetically sealed structure easily by resistance welding or the like to the metal fitting 17 after the VCSEL 2 is mounted. Thus, the VCSEL 2 can be protected for a long life.
[0023]
The VCSEL 2 includes an active layer 21 which is a light emitting portion on the surface, and electrodes 22, 23a and 23b made of Ti / Pt / Au metal or the like in a lower layer / upper layer for applying an electric signal to the active layer 21; Alignment markers 24a and 24b made of Au metal or the like used for mounting on the base 1 are formed.
[0024]
The VCSEL 2 has an active layer 21 mounted on the optical semiconductor element mounting surface 16 of the base 1. The electrodes 22, 23a, 23b of the VCSEL 2 are electrically connected to the electrode patterns 12a, 13b, which are coplanar electric wiring of the base 1, through ribbons 31, 32, 33 such as Au ribbons. Thus, an optical signal can be generated from the active layer 21 by inputting an electric signal to the lead electrodes 14, 15a, and 15b, which are coplanar electrodes of the base 1.
[0025]
The first metal protectors 4 and 9 are made of Kovar or stainless steel.
[0026]
In this embodiment, the light emitting module using the VCSEL has been described. However, by using a light receiving semiconductor element such as a PIN photodiode or an avalanche photodiode as a surface type optical semiconductor element, it is also possible to function as a light receiving module. it can.
[0027]
Thus, according to the optical module M1 of the present embodiment, the optical waveguide that is optically connected to the VCSEL 2 is attached to the substrate 1 on which the VCSEL 2 is disposed, and the surface 16 on which the VCSEL 2 is disposed of the substrate 1 and the rear surface 20 thereof are connected. The surface to be removed was fixed to an external circuit board on which external wiring for supplying electricity to the VCSEL 2 was formed, so that the external wiring formed on the external circuit board and the wiring formed on the base 1 could be electrically connected. Therefore, a simple configuration can be achieved, the assembly is simplified, and good optical connection can be efficiently performed.
[0028]
In particular, since the internal wiring (12b, 13b, 13c, 12c, 13d) for electrically connecting the VCSEL 2 to the external wiring formed on the external circuit board is provided in the base 1, the electric wiring is short. It is possible to reduce the electric transmission loss, and to obtain the emission and reception of the optical signal capable of high output and high speed transmission.
[0029]
In particular, a support (metal fitting 17, metal ring 3, metal support) made of metal for supporting an optical waveguide (optical fiber 42 and ferrule 41 accommodating the optical fiber 42) is provided on the surface 16 of the base 1 on which the VCSEL 2 is disposed. Since the first metal protector 4 and the second metal protector 9) are provided, the optical waveguide can be metal-welded, and a structure that can easily obtain high reliability and high efficiency optical coupling characteristics can be obtained. And stable emission / reception characteristics can be obtained over a long period of time.
[0030]
In particular, a terminal electrode group including a plurality of terminal electrodes arranged in a grid shape is formed on at least three regions on the surface of the base 1 fixed to the external circuit board. , Ground (for grounding), signal (for signal), and ground (for grounding), and a high-speed optical transmission characteristic exceeding 10 Gbps can be easily obtained. Further, by forming the lead electrode and the terminal electrode group along the optical axis direction of the optical waveguide, the external circuit board surface for mounting the optical module and the position for emitting and receiving optical signals are flush with each other. Thus, a compact and low-profile optical module can be obtained.
[0031]
In addition, since the optical waveguide is made of an optical fiber and a ferrule for holding the optical fiber, a receptacle structure for attaching and detaching and connecting with an optical connector can be easily obtained, and the operability of the optical module is excellent.
[0032]
Next, the optical module assembly will be described. As shown in FIG. 7, the optical module assembly includes a light emitting module T in which a VCSEL is mounted as a surface optical semiconductor element and a PIN photodiode as a surface optical semiconductor element on one end side of a mounting base 8 which is an external circuit board. A light receiving module R mounted thereon; a driver IC 5 for driving the light emitting module T; a TIA (transimpedance amplifier) 6 for amplifying and waveform shaping an electric signal obtained from the light receiving module R; It comprises a mounting base 8 on which additional electronic devices 7 such as resistors and resistors are mounted.
[0033]
In this manner, by adopting a structure in which the electrodes are arranged at positions parallel to the optical axes of the light emitting module T and the light receiving module R, solder such as cream solder is applied to the mounting electrodes of the mounting base 8 in advance, and the light emitting module T By disposing the light receiving module R, the electronic device 7, the driver IC 5, the TIA 6, and the like, a solder reflow process at about 260 ° C. can be performed, and the optical module assembly mounted and fixed collectively is completed.
[0034]
Further, by forming a gap 10 (space) between the optical module and the mounting base 8, it is not necessary to form an insulating layer in the gap 10 to perform impedance matching.
[0035]
Here, as shown in FIG. 8, a step portion 11 is formed on the base 1 of the optical module M2, and an external electrode pad 82 for connecting the step portion 11 is substantially parallel to the optical axis and is an external circuit board. By disposing it substantially horizontally with respect to the mounting substrate 81 and at one end of the mounting substrate 81 on which the electronic device 71 and the control IC 61 are mounted, the mounting surface of the mounting substrate 81 and the optical axis can be positioned horizontally. In addition, it is possible to provide an optical module assembly with a reduced height.
[0036]
As described above, according to the optical module assembly of the present embodiment, the optical module can be assembled together with the additional electronic circuit on the external circuit board by automated reflow soldering or the like, which is excellent in mass productivity and is consequently excellent in mass productivity. And an inexpensive optical module assembly can be provided.
[0037]
【The invention's effect】
According to the optical module and the optical module assembly of the present invention, the following remarkable effects can be obtained.
[0038]
According to the optical module of the first aspect, an optical waveguide for optically connecting to the surface-type optical semiconductor element is attached to a substrate on which a surface-type optical semiconductor element is provided and wiring for supplying electricity to the surface-type optical semiconductor element is provided. The surface excluding the surface on which the surface-type optical semiconductor element is disposed and the rear surface thereof are fixed to an external circuit board on which external wiring for supplying power to the surface-type optical semiconductor element is formed, and formed on the external circuit board. Since the external wiring and the wiring formed on the base can be electrically connected, a simple configuration can be achieved, the assembly is simple, and good optical connection can be efficiently performed.
[0039]
According to the optical module of the second aspect, the internal wiring is formed in the base so as to electrically connect the surface-type optical semiconductor element and the external wiring formed on the external circuit board. This makes it possible to reduce the electric transmission loss, and to emit and receive an optical signal capable of high output and high speed transmission.
[0040]
According to the optical module of the third aspect, since the support made of a metal for supporting the optical waveguide is provided on the surface of the base on which the surface-type optical semiconductor element is provided, the optical waveguide is subjected to metal welding. This makes it possible to easily obtain a highly reliable and highly efficient optical coupling characteristic, so that stable emission and light reception characteristics can be obtained over a long period of time.
[0041]
According to the optical module of the fourth aspect, since the optical waveguide is made of an optical fiber and a ferrule for holding the optical fiber, a receptacle structure that can be easily attached and detached with an optical connector can be easily obtained. Excellent.
[0042]
According to the optical module assembly of the fifth aspect, the optical module can be assembled on the external circuit board together with the additional electronic circuit by automated reflow by solder reflow or the like, which is excellent in mass productivity and consequently inexpensive. A module assembly can be provided.
[Brief description of the drawings]
FIG. 1 is a perspective view schematically illustrating an embodiment of an optical module according to the present invention.
FIG. 2 is an exploded perspective view of the optical module in FIG.
FIG. 3 is a perspective view for explaining a wiring structure and the like in a base portion constituting the optical module in FIG. 1;
FIG. 4 is a perspective view of a surface type optical semiconductor device constituting the optical module in FIG. 1;
FIG. 5 is a perspective view of a base portion constituting the optical module in FIG. 1;
FIG. 6 is a view for explaining the optical module in FIG. 1, and is a cross-sectional view cut along a plane including an optical axis of an optical waveguide constituting the optical module.
FIG. 7 is a perspective view schematically illustrating an embodiment of the optical module assembly according to the present invention.
FIG. 8 is a side view schematically illustrating another embodiment of the optical module assembly according to the present invention.
[Explanation of symbols]
1: Base 2: VCSEL (surface type optical semiconductor element)
3: Lens 4: First metal protector (constituting support)
5: Driver IC
6: TIA
7, 71: Electronic device 8, 81: Mounting base (external circuit board)
9: Second metal protector (constituting support)
12 to 13, 18, 19: electric wiring 12b, 13b, 13c: internal wiring 14 to 15, 82: external electrode pad (lead electrode)
16: Arrangement surface of the planar optical semiconductor element 17: Metal fitting (constituting a support)
20: Back surface 21: Active layers 22 to 23: Electrode pattern 24: Alignment marker 30: Mounting surface of optical module on external circuit board 31 to 33 Ribbon 41: Ferrule (constituting optical waveguide)
42: Optical fiber (constituting optical waveguide)
61: Control IC
M1, M2: Optical module R: Light receiving module (optical module)
T: Light emitting module (optical module)

Claims (5)

An optical waveguide that is optically connected to the surface-type optical semiconductor element is attached to a substrate on which a surface-type optical semiconductor element is provided and wiring for energizing the surface-type optical semiconductor element is formed. The surface excluding the surface on which the surface-type optical semiconductor element is disposed and the rear surface thereof are fixed to an external circuit board on which external wiring for supplying electricity to the surface-type optical semiconductor element is formed, and formed on the external circuit board. An optical module, wherein an external wiring and a wiring formed on the base can be electrically connected. 2. The optical module according to claim 1, wherein an internal wiring is formed in said base so as to electrically connect said surface type optical semiconductor element and an external wiring formed on said external circuit board. 2. The optical module according to claim 1, wherein a support made of metal for supporting the optical waveguide is provided on a surface of the base on which the planar optical semiconductor element is provided. The optical module according to claim 1, wherein the optical waveguide includes an optical fiber and a ferrule holding the optical fiber. 5. An optical module assembly, wherein the optical module according to claim 1 is mounted on the external circuit board via solder.

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