JP2002076496A - Optical module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical module of simple constitution, excellent in heat radiation, excellent in long term reliability and excellent in speed. SOLUTION: This optical module M is composed of a first base 3 for disposing an optical semiconductor element 1 and an optical waveguide 4 optically connected to the optical semiconductor element 1 and a second base 6 provided with a connection terminal 9 electrically connected to an external circuit. The first base 3 is disposed on one main surface of the second base 6, a base 21 for heat radiation is provided inside a recessed part 13 formed on the other main surface and a circuit element 8 connected to the optical semiconductor element 1 is mounted on the base 21 for heat radiation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical module used for transmitting and receiving optical transmission such as optical fiber communication and optical interconnection.

[0002]

2. Description of the Related Art In an optical module used for transmitting and receiving an optical signal, in order to ensure stable operation, a temperature rise due to heat generation of an optical semiconductor element or an electronic circuit is suppressed, and the temperature of the optical semiconductor element is kept low. And must be kept constant.

For example, in an optical module J shown in FIG.
A semiconductor laser 5 as an optical semiconductor element in a package 51;
A substrate 53 on which the circuit 2 is mounted and a substrate 55 on which the drive circuit 54 is mounted are mounted, respectively, and an optical fiber 56 is optically coupled to the semiconductor laser 52 via a lens 57.
The semiconductor laser 52 includes electrodes 58, 5 formed on a substrate 53.
9 and a driving circuit 54 mounted on a substrate 55 via a bonding wire 60 and driven (see Japanese Patent Laid-Open No.
The above driving circuit generates a current for driving and controlling the semiconductor laser, so that the driving circuit becomes high temperature and generates heat. Similarly, when a current is injected and light is output to the semiconductor laser, the heat generated by the drive circuit causes the semiconductor laser to further generate heat, which causes a change in the oscillation wavelength and a decrease in the optical output, thereby causing a failure of the semiconductor laser. In the optical module J, in order to solve this problem, a semiconductor laser and a substrate on which a drive circuit is mounted are separated.

[0004]

However, in a structure like the above-mentioned optical module, the substrate on which the optical semiconductor element is mounted and the substrate on which the drive circuit is mounted are mounted separately in the same package. Since the substrate to be mounted is the same, heat generated in the drive circuit and heat generated in the optical semiconductor element are transmitted to the package. At this time, if a package made of a material having a high thermal resistance (for example, a resin such as epoxy or glass) is used, the heat of the optical semiconductor element and the driving circuit cannot be efficiently dissipated, and a stable operation cannot be obtained. Or cause serious problems such as destruction due to temperature rise.

When a package made of a material having a low thermal resistance (for example, a metal such as copper or aluminum or a ceramic such as alumina or aluminum nitride) is used, heat generated in a driving circuit is transmitted to the optical semiconductor element. The heat generated in the elements is transmitted to the drive circuit, which may cause the respective temperatures to rise. This is relatively mitigated if the package is used in a low temperature atmosphere, but poses a problem when used in a high temperature atmosphere.

Further, in the optical module J, since the optical semiconductor element and the drive circuit must be mounted separately from each other, the electric wiring becomes long, and it is difficult to operate the optical semiconductor element at high speed. In addition, miniaturization of the optical module itself cannot be expected.

Furthermore, since the optical semiconductor element and the optical fiber are mounted on different substrates, there is a problem that the optical coupling characteristics fluctuate due to a difference in thermal expansion of the substrate due to a temperature change.

Accordingly, the present invention not only can prevent the above-described heat radiation problem with a simple configuration as much as possible, but also can accurately perform the optical connection between the optical fiber and the optical semiconductor element, and have the same level as the mounting substrate. It is an object of the present invention to provide an optical module that can be reduced in size and has excellent long-term reliability and high speed.

[0009]

In order to solve the above-mentioned problems, an optical module according to the present invention comprises: a first base on which an optical semiconductor element and an optical waveguide optically connected to the optical semiconductor element are provided; An optical module, comprising: a second base having a connection terminal electrically connected to a circuit, wherein the first base is disposed on one main surface of the second base, and the optical semiconductor element is disposed on the other main surface. A concave part that forms an electrical circuit for
A heat dissipation base connected to the electric circuit is provided in the recess.

[0010] In addition, a through hole is formed in the recess of the second base, and the heat dissipation base is accommodated in the through hole. Thereby, it becomes easy to release heat to the one main surface side of the second base, and it is possible to further enhance the heat radiation effect.

The first substrate is a silicon single crystal substrate,
The second substrate is a ceramic multilayer wiring substrate, and the heat-radiating substrate is a metal substrate. As a result, it is possible to expect an effect that heat radiation in the optical semiconductor element is improved and heat radiation in the electric circuit is also improved.

It is particularly preferable that the first base is made of a material having a good thermal conductivity and capable of anisotropic etching, and a groove for fixing the optical waveguide is precisely formed by anisotropic etching. And the optical waveguide can be accurately fixed, and as a result, a structure having excellent optical coupling characteristics can be obtained.

Further, the second base is made of ceramic such as alumina or aluminum nitride as a main raw material, and is a ceramic multilayer wiring board in which electric wiring is provided. The heat radiating base on which the drive circuit or the signal processing circuit is mounted is made of CuW, By using a metal, such as Al or Cu, having a higher thermal conductivity than the base 2, heat conduction to the base 2 can be prevented as much as possible.

In particular, the electric terminals, which are the external conductors of the driving circuit or the signal processing circuit, are formed in a ball grid array in which solder balls are arranged in an array, so that high-density surface mounting is possible and the signal line is provided. Can be minimized, and a source excellent in high-frequency electric characteristics can be obtained.

Further, the periphery of the optical waveguide which is optically connected to the optical semiconductor element mounted on the first base is sealed with a transparent resin having low water absorption, and is mounted in a concave portion provided on the second base. By sealing the periphery of the first base with an opaque resin, a highly reliable structure can be obtained.

In particular, since the transparent resin has a refractive index higher than that of the optical waveguide and smaller than that of the active layer of the optical semiconductor element, the reflection from the optical waveguide can be reduced, thereby increasing the coupling efficiency. be able to.

Particularly, the opaque resin has a Young's modulus of 5
By making it smaller than 000 N / mm ² , the stress on the periphery of the optical coupling part can be reduced, and the characteristic deterioration can be reduced.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is an exploded perspective view of an optical module M according to the present invention, and FIG. 2 is a perspective view showing a rear surface side of a second substrate which is a constituent element of the optical module M, and FIG. FIG. 4 is a perspective view of the optical module M, and FIG.
FIG.

The optical module M includes a first base 3 made of anisotropically-etchable silicon single crystal (thermal conductivity: 168 W / m · K) or the like having an optical semiconductor element and the like, wirings and the like. And a second base 6 made of ceramic or the like.

The first substrate 3 includes at least a light emitting element 1 such as a semiconductor laser as an optical semiconductor element, and the light emitting element 1.
Is provided with an optical fiber 4 which is an optical waveguide optically connected to the optical fiber.

The second base 6 is provided with solder balls 9 and 10 as a plurality of external conductors (that is, electrically connected to an external circuit (not shown)). Are connected to the electric wiring of the second base 6.

A light receiving element 2 for monitoring, such as a photodiode, is disposed on the first base 3 in the vicinity of the light emitting element 1, and monitors light emitted from the rear side from the light emitting element 1. The light emission intensity of the light emitting element 1 can be controlled. A V-groove 16 is formed on the front side of the light emitting element 1 by anisotropic etching or the like, and the optical fiber 4 is fixedly mounted on the V-groove 16 with a holding plate 5 made of quartz glass or the like. ing. Thus, highly accurate fiber mounting can be performed, and mass production can be performed easily and quickly by a wafer process.

On the first base 3, conductive patterns (electrode pads) 17a and 17b of the light emitting element 1 and conductive patterns (electrode pads) 18a and 18b of the light receiving element 2 are formed. , 17b, 18
In order to transmit and receive electric signals, a and 18b are formed by applying Au (gold) metallization by a thin film process or the like.

The light emitting element 1 has V on the conductive pattern 17a.
Au-Sn which is passively aligned at an accurate position with respect to the groove 16 and is formed in advance on the conductor pattern 17a
It is mounted and fixed by melting the alloy solder.
Similarly, the light receiving element 2 is mounted and fixed on the conductor pattern 18a. Further, each optical element is, for example, φ25μ.
A bonding wire such as an Au wire having a length of about m and a chip upper surface electrode of each optical element and the conductive patterns 17b and 18b
Are connected respectively.

Optical fiber 4 optically connected to light emitting element 1
For example, a quartz-based single mode optical fiber having a diameter of about 125 μm or the like is applied, and a part thereof is precisely molded with zirconia or the like for optically connecting to an external optical connector (not shown). An optical fiber stub supported and fixed by a ceramic ferrule 19 having a thickness of about 6 mm is mounted.

The second substrate 6 has electrodes and internal wiring patterns formed thereon, and is made mainly of alumina (thermal conductivity: 20 W / m · K) or aluminum nitride (thermal conductivity: 150 W / m · K). It is composed of a ceramic multilayer substrate or the like manufactured by laminating ceramic thin film sheets. As will be described later, a concave portion 29 for accommodating the first base 3 is provided on one main surface side, and a driving circuit which is a circuit element for driving the optical semiconductor elements 2 and 3 on the other main surface side. IC
The concave portion 13 in which the second base member 6 is mounted.
A heat dissipation base 21 having a higher thermal conductivity is provided in advance.

The second base 6 has a recess 29 for receiving the first base 3 and a recess 29 having a depth about the thickness of the base 3 and a recess 30 for fixing and supporting the ferrule 19. In the vicinity of the concave portion 29, an electrode pattern for making electrical connection with the first base 3, and electrode patterns 31a and 31b for mounting and fixing the electronic components 14 and 15 which are chip capacitors and chip resistors, and the like. Are formed. These electrode patterns are formed by a drive circuit IC formed on the second base 6 by the internal wiring pattern of the second base 6.
8 is connected to the electrode pattern formed in the concave portion 13 for mounting the same. Similarly, solder balls 9 and 10 as external conductors are also connected by the internal wiring pattern. The recess 13 has CuW (thermal conductivity: 250 W / m · K), aluminum (thermal conductivity: 240 W / m · K), and copper (thermal conductivity: 390 W /) having excellent heat dissipation for mounting and mounting the drive circuit IC 8. m, K) etc.
1 is previously formed on the second substrate 6 by brazing or soldering. The heat radiating base 21 is connected to an external heat radiator 7 made of aluminum or the like by a paste material mixed with an adhesive material excellent in heat conductivity or a metal powder excellent in heat conductivity in order to further improve the heat radiating property. Have been.

The recess 29 for accommodating the first base 3 is provided with a heat radiating pad made of Au for radiating heat generated in the first base 3. The heat radiating pad is connected in advance to a thermal via 23 connected to an external heat radiator 22 made of CuW.

The solder ball 10a, which is an external conductor, is connected to an electrode pad (not shown) formed in the recess 13 via the internal wiring patterns 24e and 25d, and is connected to the drive circuit IC8 by an Au bonding wire. . The conductor pattern 17a of the first base 3 is connected to the conductor pattern 31b of the base 6 by an Au bonding wire. An electronic component 15 such as a chip resistor or a chip capacitor is mounted and fixed on the conductor pattern 31b. The electronic component 15 is connected to the electronic component 14 via internal wiring patterns 24a, 25a and 24b. Recess 1 through 24c, 25b, 24d, 25c
3, and is electrically connected to the drive circuit IC8 by a bonding wire. A specific electrode of the drive circuit IC8 is similarly connected to the solder ball 10b via the internal wiring patterns 27 and 26, and transmits and receives signals to and from the outside.

The recess 13 of the second substrate 6 is sealed with a cap 28 of metal, glass, ceramic, or the like, or by filling and solidifying a resin.

A part of the optical fiber optically connected to the light emitting element 1, the light receiving element 2, and the part including the wiring are hardly permeable to humidity, and have a refractive index equal to or higher than that of the optical fiber. It is covered with a thermosetting type silicone resin (not shown) lower than the wave layer and solidified.

Then, the periphery of the mounting portion of the base 3 of the second base 6 is covered with, for example, an epoxy-based opaque resin 12 and solidified to complete the optical module M as shown in FIG.

The opaque resin has a Young's modulus of 5000 N /
By potting and solidifying with an opaque epoxy resin, acrylic resin, or silicone resin with a low stress of not more than mm ^{2, the} displacement between the light emitting element and the optical fiber in the optical coupling portion can be suppressed.

As described above, since the drive circuit IC 8 is mounted on the heat radiating base 21 in the recess formed in the second base 6, the high heat generated in the drive circuit IC 8 causes the optical semiconductor mounted on the first base 3. It can operate without transmitting to the elements 2 and 3. On the other hand, the heat generated by the optical semiconductor elements 2 and 3 of the first base 3 can be radiated by the external heat radiator through the heat radiating pad and the thermal via formed in the concave portion 29, so that the characteristic deterioration hardly occurs. It has a configuration.

Therefore, the heat generated in the optical semiconductor element does not stay inside, and a highly reliable optical module with good heat dissipation can be obtained.

The wiring pattern formed on the first base 3, the wiring pattern formed on the second base 6, and the internal wiring pattern are microstrip lines or coplanar lines having excellent high-frequency characteristics, and high-frequency characteristics such as ribbon wires are used. 10Gbp by performing excellent wiring
Higher frequencies such as s can be achieved.

Further, the periphery of the optical semiconductor element and the optical waveguide optically connected to the optical semiconductor element are protected by a transparent resin which is hardly permeable to humidity, and this is covered with a low-stress opaque resin, so that a very excellent hermetic sealing is achieved. It can be structured.

[0039]

According to the optical module of the present invention, the first base on which the optical semiconductor element and the optical waveguide to be optically connected to the optical semiconductor element are mounted, and the first base on one principal surface side are accommodated. A concave portion for mounting a circuit element such as a drive circuit or a signal processing circuit for driving the optical semiconductor element is provided on the other main surface side, and further, an electric terminal which is an external conductor of the circuit element is provided. The concave portion for accommodating the circuit element is provided with a heat radiating substrate having a higher thermal conductivity than the second substrate, and the circuit element is mounted and accommodated in the heat radiating substrate. It is possible to provide an optical module which is excellent in heat dissipation and has no characteristic deterioration without transmitting heat generated in the optical semiconductor element to the circuit element and heat generated in the circuit element to the optical semiconductor element.

Further, the first substrate provided with the optical semiconductor device and the optical waveguide optically connected thereto is mounted on the second substrate having a conductor electrically connected to the optical semiconductor device. By protecting the element and the periphery of the optical waveguide optically connected to it with a transparent resin that is not easily permeable to humidity, and covering this with a low-stress opaque resin, it is possible to obtain a very excellent hermetic sealing structure, An optical module with extremely high reliability can be provided.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view schematically illustrating an embodiment of an optical module according to the present invention.

FIG. 2 is an exploded bottom perspective view of FIG.

FIG. 3 is a perspective view schematically illustrating an embodiment of the optical module according to the present invention.

FIG. 4 is a sectional view of an optical module according to the present invention.

FIG. 5 is a perspective view illustrating a conventional optical module.

[Explanation of symbols]

 1: light emitting element (optical semiconductor element) 2: light receiving element (optical semiconductor element) 3: first base 4: optical fiber (optical waveguide) 5: optical fiber holding lid 6: second base 7: external radiator 8: Drive circuit IC (circuit element) 9: solder ball 10: solder ball 12: opaque resin 13: recess 14: electronic component 15: electronic component 16: V-groove 17: conductor pattern 18: conductor pattern 19: ferrule 20: external radiator 21: Internal heat dissipating substrate 22: External heat dissipating substrate 23: Thermal via 24: Internal wiring pattern 25: Internal wiring pattern 26: Internal wiring pattern 27: Internal wiring pattern 28: Cover for driving circuit IC sealing 29: Recess 30: Recess

Claims (2)

[Claims] 1. An optical module comprising: a first base provided with an optical semiconductor element and an optical waveguide optically connected to the optical semiconductor element; and a second base provided with a connection terminal electrically connected to an external circuit. The first base is provided on one main surface side of the second base.
An optical module comprising a base, a heat dissipation base provided in a concave portion formed on the other main surface side, and a circuit element connected to the optical semiconductor element mounted on the heat dissipation base. . 2. The optical module according to claim 1, wherein a through-hole is formed in a concave portion of the second base, and a heat-radiating base is accommodated in the through-hole.