JP4798863B2 - Opto-electric wiring board - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
TECHNICAL FIELD The present invention relates to a base wiring board used in an optical communication module, and is a photoelectric circuit that can be assembled with a large capacity, a small size, and a high reliability by incorporating light receiving and emitting elements such as LD and PD and electronic elements for operating them. The present invention relates to a wiring board.
[0002]
[Prior art]
In recent years, optical fiber communication has become widespread in the fields of public communication and local area communication (LAN). Increasing the capacity of transmission systems has become an urgent issue as the amount of information transmitted increases. Conventionally, techniques such as high-density wavelength division multiplexing (DWDM) and parallel transmission (Parallel Link) have been used as techniques for increasing the capacity, and the transmission capacity has been dramatically expanded.
[0003]
However, on the other hand, as a problem in the optical mounting technology, increasing the density of wiring has become an issue in order to cope with the increase in the number of elements. In other words, in DWDM and Parallel Link, signals are multiplexed using a plurality of light emitting / receiving elements, and as the degree of multiplexing increases, the number of elements and the number of wirings increase, and the size and complexity of the wiring board increase. The problem is that assembly productivity due to the deterioration of the assembly.
[0004]
A conventional optoelectric wiring board will be described below with reference to the drawings.
[0005]
(1) A conventional optoelectric wiring board P1 is shown in FIG. A plurality of optical modules 100 in which light emitting and receiving elements are discretely mounted in a package and a driving IC 500 for operating them are mounted on a substrate to constitute an optoelectric wiring substrate. As a packaging structure of the optical module 100, a structure called a pigtail type in which a short fiber 300 of about several tens of centimeters is incorporated in a package called a butterfly type is common. Electric input / output is performed by lead terminals 702 arranged in a row on the side of the package. In particular, a coaxial connector 701 is used for a high-frequency terminal, and a high-frequency signal is transmitted to the inside of the package with low loss. is there.
[0006]
In the optical module 100 shown in FIG. 5, one optical element is packaged per package, and a plurality of such optical modules are usually mounted on a substrate 80, or such an opto-electric wiring board is mounted. By mounting a plurality of sheets on a gantry, a multi-channel opto-electrical wiring is realized.
[0007]
{Circle around (2)} Further, along with the improvement of the degree of integration of semiconductor chips and the improvement of manufacturing technology for large-scale chips, a parallel optical semiconductor module as shown in FIG. 6 in which a plurality of optical semiconductor elements are arrayed has been proposed.
[0008]
In FIG. 6, 200 is an optical semiconductor element array, 400 is a subcarrier, 300 is a fiber array for inputting / outputting light to / from the optical semiconductor element array 200, 720 is an electrical terminal, 101 is a package, and 501 is a driving IC.
[0009]
In the parallel transmission module shown in FIG. 6, the fiber array 300 can be aligned with high accuracy by the V-groove 401 formed on the subcarrier 400.
[0010]
Input / output light of the optical semiconductor element array 200 is coupled to the fiber array 300 arranged at the same pitch, and optically wired to the outside via the optical connector 600 formed on the side surface of the package 101. Since the fiber has almost no crosstalk with the adjacent line and has a small diameter, it can be wired at a narrow interval such as an interval of 0.125 mm.
[0011]
The optical semiconductor element array 200 is wired to the driving IC 501 mounted inside the package, and the electric wiring of the driving IC 501 is taken out to the substrate 800 from the lead terminals 720 arranged in a row on the side surface of the package 101. The lead terminal 720 is attached to the package 101 at a temperature higher than the melting temperature of PbSn solder or the like used for fixing to the package 800 such as gold brazing. In general, the driving IC 501 is configured such that a differential wiring (pair line) is used for each of the data signal and the clock signal, and four high-frequency wirings are formed for each element. In addition, a control line for adjusting the analog output and a power line of the IC itself are wired. In electrical wiring, pin spacing is determined in consideration of suppression of crosstalk to adjacent lines, matching of characteristic impedance, and mountability. For example, pin spacing of 1.25 mm pitch is used.
[0012]
The electrical wiring is characterized in that the number of wirings is four times more than the optical wiring and the wiring interval is wide.
[0013]
(3) Japanese Patent Laid-Open No. 2000-28871 also discloses a method in which electrical terminals are arranged in a lattice pattern on the lower surface of a package and mounted on a printed wiring board via solder bumps. In this method, both the electrical wiring and the optical wiring are similarly configured such that terminals are arranged in a lattice pattern on the lower surface of the package, and the access direction of the wiring is the same direction as the electrical wiring.
[0014]
[Problems to be solved by the invention]
However, in the optoelectric wiring board {circle around (1)}, since the area occupied by the package on the board is large, the number of elements that can be mounted per unit area is limited, and the mounting efficiency is extremely low.
[0015]
Further, it is difficult to automate the assembly of the connector 701, it takes time to manage the tightening torque, it takes time to process the extra length of the coaxial cable 700, the fiber pigtail 300 becomes an obstacle, and it is difficult to automate the mounting of the optical module 100. For example, assembly productivity is low.
[0016]
The photoelectric wiring board {circle around (2)} also has a low electrical wiring density and a low degree of optical element integration. That is, since the extraction of the lead terminal 720 is limited to the line on the outer periphery of the package 101, the mounting efficiency is low in the same size package. In addition, it is necessary to secure the mounting area of the lead terminals 101 on the substrate 800, and the size of the opto-electric wiring board is increased accordingly. Further, it is necessary to control the brazing process of the lead terminals 101 so that the connecting portions do not shift, and it is difficult to improve the wiring density by narrowing the pitch of the lead terminals 720. In general, since brazing is processed at a high temperature, when a thin film functional element is manufactured on the package 101, it is difficult to control the element characteristics, and the design range is limited.
[0017]
In the above-mentioned opto-electric wiring board (3), since there is generally a difference in thermal expansion coefficient between the printed wiring board and the package, the package is deformed due to a change in environmental temperature, and the alignment of the optical connection portion is shifted and light is emitted. There is a problem that connection characteristics become unstable. Also, since the optical wiring is in the same plane as the electrical wiring in the package, the electrical wiring density, which is a major factor for device integration, is reduced. Also, in order to connect to the fiber, the printed wiring board needs to be transparent and non-reflective coated with respect to the emitted light, which reduces the productivity of the printed wiring board and prevents electrical wiring in the light transmission part. The wiring density of the wiring decreases. Also, multilayer wiring is difficult. Further, since optical wiring is performed in a direction perpendicular to the printed wiring board, when a plurality of printed wiring boards are mounted on the housing, it is necessary to take a mounting interval by the fiber bending radius, and the mounting density does not necessarily increase. In addition, when a waveguide is formed on a printed wiring board and optical wiring is performed on the printed wiring board in the horizontal direction, 90-degree optical path conversion is required, which causes a problem of reduction in coupling efficiency and yield.
[0018]
Accordingly, the present invention has been proposed in view of the above-described conventional problems, and can be assembled with a large capacity, a small size, and a high reliability by incorporating a light emitting / receiving element such as an LD or PD and an electronic element for operating them. An object is to provide an optoelectric wiring board.
[0019]
[Means for Solving the Problems]
In order to achieve the above object, an optoelectric wiring board of the present invention is a base wiring board having a plurality of terminals arranged on the lower surface and having a recess on the upper surface, and an optical element substrate provided in the recess, An optical element substrate in which an optical semiconductor element electrically connected to a terminal is disposed on a disposition surface, and has a lower elastic modulus than that of the base wiring substrate and the optical element substrate, has a plate shape, and one main surface of the arrangement surface of the optical element substrate is fixed at one end and includes a lead-shaped plate member fixed to the periphery of said recess said a top surface of the base wiring board.
[0020]
Specifically, for example, an optical element substrate provided with an optical semiconductor element electrically connected to the ball-shaped terminals is disposed on the upper surface side of the base wiring board in which a plurality of ball-shaped terminals are arranged on the lower surface side. An optoelectric wiring board comprising: an optical element substrate fixed to a plate-like elastic member having a lower elastic modulus than the base wiring board and the optical element substrate, and the elastic member fixed to the base wiring board. It is characterized by.
[0021]
Further, a V-shaped groove provided in the bearing surface of the front Symbol photonic device substrate, provided in the V-groove, and characterized by further comprising a said optical semiconductor element and optically coupled to an optical fiber To do.
[0022]
Further, the front cut over de shaped plate body, a lead for a high-frequency wiring between a ground conductor formed on the surface in contact with the lower surface of the optical device substrate in the recess, and the lead and the ground conductor And a dielectric block provided on the substrate .
[0024]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of an optoelectric wiring board according to the present invention will be described in detail based on the drawings.
[0025]
The optoelectric wiring board M1 is shown in FIG. The optoelectric wiring board M1 accommodates a subcarrier 4 which is an optical element substrate on which an optical semiconductor element array 2 and an optical fiber (array) 3 are mounted, a package 1 on which a driving IC 5 is mounted, and a subcarrier 4. A cavity 41, a plurality of ball terminals 80 mounted on the lower surface of the package 1, a bonding wire 70 for wiring the optical connector 6 and the driving IC 5, and a bonding wire for wiring the optical semiconductor element 2. 71, and an elastic body 10 which is an elastic member for buffering the distortion of the package 1.
[0026]
The package 1 is preferably made of a ceramic material made of a dielectric (eg, Al 2 O 3, glass, AlN) having excellent high frequency characteristics, and has a multilayer structure. That is, a wiring pattern is formed for each layer, and the layers are wired with through-hole electrodes. As a result, electric wiring between the input / output terminals of the ball-shaped terminal 80 and the driving IC 5 is formed. Further, other electronic components for operating the driving IC 5 are also mounted on the mounting surface of the driving IC 5 to form a circuit. Further, the wiring is provided from the output terminal of the driving IC 5 to the optical semiconductor element array 2 on the subcarrier 4.
[0027]
In the cavity 41, a ground electrode is formed on the surface where the lower surface of the subcarrier 4 contacts, a microstrip line as a high-frequency transmission line is formed on the subcarrier 4, and a wide-band electrical wiring is formed up to the optical semiconductor element array 2. The
[0028]
The ball-shaped terminals 80 can be arranged on the entire lower surface of the package 1, thereby improving the wiring density by N / 4 times (N is the number of wirings per side) compared to the case where wiring is provided around the package 1.
[0029]
The optical input / output from the optical semiconductor element array 2 is coupled to a fiber 3 aligned by a V-groove formed in advance at a predetermined position on the subcarrier 4 and further coupled to a farther fiber by an optical connector 6 and optical wiring. Is formed. Single crystal Si is suitable for the material of the subcarrier 4. By adopting single crystal Si, a high-precision V-groove can be formed on the subcarrier 4. The subcarrier 4 is mounted inside a cavity 41 formed in the package 1 and fixed by the elastic body 10.
[0030]
The fiber 3 is drawn horizontally from the opening formed in the upper part of the package 1 to the package mounting surface. Thereby, the optical wiring and the electrical wiring can be alternately mounted in a thin layer shape, and the mounting density is increased.
[0031]
The elastic body 10 is preferably made of a material having a lower modulus of elasticity than the material of Si and the package 1 used for the subcarrier 4 and close to the thermal expansion coefficient of the package 1. For example, a commonly used Al ₂ O ₃ FeFeCo alloy In order to facilitate the bonding to the package 1, Au / Ni plating is applied to the surface. The elastic body 10 has a thin plate-like structure so as to be easily elastically deformed, and is pressed by the joint portion 11 and joined to the package 1. AuSn solder can be used for bonding. Further, welding may be performed without using solder or the like. The subcarrier 4 is fixed only by friction caused by pressing load. By making the bending of the subcarrier 4 more rigid than the elastic body 10, the distortion of the package 1 is buffered by the elastic body 10 and the distortion of the subcarrier 4 is suppressed.
[0032]
The subcarrier 4 needs to have increased rigidity in the thickness direction so that the optical axes of the optical semiconductor element array 2 and the fiber 3 do not shift. However, if the thickness of the subcarrier 4 is increased in order to increase the rigidity, the thickness of the package 1 is also increased, and the high frequency characteristics of the through-hole electrode are deteriorated. For example, the thickness of the subcarrier 4 is preferably 0.5 to 1.0 mm for 10 Gbps transmission.
[0033]
FIG. 2 shows an optoelectric wiring board M2 which is another embodiment.
[0034]
The optoelectric wiring board M2 shown in FIG. 2 includes a subcarrier 4 which is an optical element substrate on which the optical semiconductor element array 2 and the optical fiber 3 are mounted, a package 1 on which a driving IC 5 is mounted, and a ball mounted on the lower surface of the package 1. The bonding wire 70 for wiring the optical terminal 6, the optical connector 6, and the driving IC 5, the bonding wire 71 for wiring the optical semiconductor element 2, and the holding fitting 12 that is an elastic member.
[0035]
Wiring of the opto-electric wiring board M2 is performed in the same manner as the opto-electric wiring board 1, and has a structure in which the subcarrier 4 is mounted on a holding metal fitting 12 used as an elastic member. The holding metal 12 has a structure in which the lower surface of the region where the subcarrier 4 is mounted is disposed on the air layer, and is joined to the package 1 in the region other than the lower surface. For joining, brazing (for example, Au) or soldering (for example, AuSn) can be used. A material close to the thermal expansion coefficient of the package 1 is suitable for the holding metal 12. For example, an FeNiCo alloy can be suitably used for commonly used Al 2 O 3, and Au / Ni plating is applied to the surface to facilitate bonding to the package 1. Is done. The subcarrier 4 is stably connected in the package 1 without being distorted by the rigidity of the holding metal 12. The holding metal fitting 12 is connected to the ground electrode of the package, and functions as a ground electrode of the subcarrier 4 to constitute a microstrip line that is a high-frequency transmission line. As a result, a wide-band electrical wiring to the optical element is formed.
[0036]
FIG. 3 shows an optoelectric wiring board M3 which is another embodiment.
[0037]
The optoelectric wiring board M3 shown in FIG. 3 includes a subcarrier 4 which is an optical element substrate on which the optical semiconductor element array 2 and the optical fiber 3 are mounted, a package 1 on which a driving IC 5 is mounted, and a ball mounted on the lower surface of the package 1. And a lead wire 72 that is a lead plate as an elastic member and a bonding wire 70 for wiring the optical connector 6 and the driving IC 5.
[0038]
Wiring of the opto-electric wiring board M2 is performed in the same manner as the opto-electric wiring board 1, and has a structure in which the subcarrier 4 is mounted on the package 1 supported by leads 72 used as elastic members. The lead 72 is brazed (for example, Au) at a high temperature to an electrode pad or a conductor (for example, an Au / Cr, Au / Cr / Ni, Au / Pt / Ti electrode in the upper layer / lower layer) on the subcarrier 4, and the package 1 Is soldered (for example, AuSn). In addition to brazing and soldering, the lead 72 may be joined by using an adhesive or glass. The subcarrier 4 is stably connected in the package 1 without being distorted by the elasticity of the leads 72. A dielectric block 42 is disposed below the high-frequency wiring lead 72 as a dielectric of a microstrip line. The characteristic impedance of the width of the lead 72 for high frequency wiring, the thickness of the dielectric block 42, and the relative dielectric constant is adjusted. As a result, wide-band electrical wiring to the optical element is formed, and at the same time, the electromagnetic field concentrates inside the dielectric block 42, so that crosstalk with adjacent lines is suppressed.
[0039]
FIG. 4 shows a schematic state when the photoelectric wiring board M3 is distorted.
[0040]
Usually, in many cases, a glass epoxy copper-clad substrate is used as a substrate on which a multilayer ceramic package is mounted. However, the difference in coefficient of thermal expansion of these substrates differs by about an order of magnitude, and when connected by ball-shaped terminals, the package is distorted due to thermal stress, and the amount of distortion varies due to variations in ambient temperature. The shape and arrangement of the balls affect the amount of distortion and the mounting reliability of the ball joint. Therefore, in order to optimize them and ensure mounting reliability, it is necessary to suppress distortion of the optical element substrate independently of the distortion amount. In the photoelectric circuit board M3, the distortion of the package 1 is buffered by the leads 72, so that the rigidity of the subcarrier 4 that is an optical element substrate can be maintained, and a stable optical connection state is maintained. The same applies to the photoelectric wiring boards M1 and M2. Since a material higher than the elastic modulus of the package 1 and the subcarrier 4 is selected as the elastic member, the elastic member is elastically deformed and the subcarrier 4 acts without distortion.
Therefore, this enables high-density optoelectronic wiring on one substrate.
[0041]
【The invention's effect】
According to the optoelectric wiring board of the present invention, the following remarkable effects can be obtained.
・ High-density mounting of optical elements by increasing the density of electrical terminals is possible. As a result, the size and capacity can be dramatically increased.
-Since the optical wiring and electrical wiring are arranged in the planar, the function can be efficiently expanded by mounting a plurality of pieces in a spatially vertical direction.
-It is possible to suppress the elastic distortion of the subcarrier that is the optical element substrate with a simple structure. As a result, a stable optical connection state can be maintained without being affected by ambient temperature conditions.
Good structure can be hermetically sealed with a simple structure.
The thermal resistance at the contact point between the package and the subcarrier can be increased, and the heat generated from the electronic circuit is prevented from flowing into the subcarrier. Thereby, characteristics such as an operating point and an optical spectrum of the optical element are stabilized.
This is a simple assembly process with a small number of parts.
[0042]
With the above effects, it is possible to provide an optoelectric wiring board having a large capacity, a small size, high reliability, and excellent mass productivity.
[Brief description of the drawings]
1A and 1B are a plan view and a cross-sectional view schematically illustrating an optoelectric wiring board according to a reference example .
2A and 2B are a plan view and a cross-sectional view schematically illustrating another optoelectric wiring board according to a reference example .
FIGS. 3A and 3B are a plan view and a cross-sectional view schematically illustrating still another photoelectric wiring board according to the present invention. FIGS.
FIG. 4 is a cross-sectional view schematically showing an optoelectric wiring board according to the present invention, and is a view for explaining how a package is distorted.
FIG. 5 is a plan view schematically illustrating a conventional optoelectric wiring board.
FIG. 6 is a plan view schematically illustrating a conventional optoelectric wiring board.
[Explanation of symbols]
1: Package 2: Optical semiconductor element array 3: Fiber 4: Subcarrier 5: Driving IC
6: Optical connector 10: Elastic body 11: Connection portion 12: Holding metal fitting 41: Cavity 42: Dielectric block 70, 71: Bonding wire 72: Lead 80: Ball-shaped terminal 100: Optical module 200: Optical semiconductor element array 300: Optical fiber 400: subcarrier 500, 501: driving IC
600: Optical connector 700: Coaxial cable 701: High-frequency connector 702: Lead P1: Conventional opto-electric wiring boards M1, M2, M3: Opto-electric wiring boards

Claims (3)

A base wiring board having a plurality of terminals arranged on the lower surface side and a recess on the upper surface side;
An optical element substrate provided in the recess, the optical element substrate having an optical semiconductor element electrically connected to the terminal disposed on an arrangement surface;
The elastic modulus is lower than that of the base wiring substrate and the optical element substrate, and is in the form of a plate, fixing the arrangement surface of the optical element substrate at one end of one main surface , and And a lead plate fixed to the periphery of the recess ,
An opto-electric wiring board comprising: A V-groove provided on the arrangement surface of the optical element substrate;
An optical fiber provided in the V-groove and optically coupled to the optical semiconductor element;
Photoelectric circuit board according to claim 1 Symbol mounting further comprising. The lead plate is a lead for high frequency wiring,
A ground conductor formed on a surface of the recess that contacts the lower surface of the optical element substrate;
A dielectric block provided between the lead and the ground conductor;
Photoelectric circuit board according to claim 1, further comprising a.

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