JP4029369B2 - Optical transmission module - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a transmitter, a receiver, and a composite thereof used for optical communication, that is, a so-called optical transmission module.
[0002]
The so-called optical transmission module has various names such as an optical data link, an optical transceiver, and an optical transmission / reception module. In the present invention, the so-called optical transmission module is collectively referred to as an “optical transmission module”. The optical transmission module includes a light emitting element (LED, LD), a light receiving element (PIN-PD, APD), and a drive IC or amplifier, a signal processing circuit, and an optical fiber for operating these components. A certain optical connector or the like is used in combination, and is used, for example, to communicate with light having a wavelength of 1.3 μm using an optical fiber.
[0003]
[Prior art]
In order to realize a multimedia society, optical communication systems for subscribers are being actively studied. In the optical communication system, it is necessary that the transmission part does not emit noise to the outside and the reception part does not pick up noise from the outside. For this reason, conventional optical transmission modules are mainly housed in metal cases or metallized ceramic cases.
[0004]
With the development of optical communication technology, miniaturization of optical receiver modules is required. In particular, low-priced optical modules are indispensable for constructing optical subscriber systems, and electronic modules such as general-purpose ICs. It must be surface mountable on the equipment board. Therefore, a dual in-line package (DIL-PKG) type as shown in FIG. 2, which is easy to mount on a board of an electronic device from the conventional coaxial type structure as shown in FIG. 1, or as shown in FIG. There has been a demand for such a GAL-wing type and SOP. 1 to 3, reference numeral 1 denotes an optical fiber, 2 denotes a lead, 3 denotes a package (PKG), and 4 denotes a cap.
[0005]
In order to reduce the price of the optical transmission module, it is effective to use a resin molded body (herein sometimes referred to as “resin mold”) molded with resin without using PKG. A resin mold module as shown in FIG. 4 having a lead 2 and a resin mold 5 has been proposed.
[0006]
[Problems to be solved by the invention]
However, since this resin mold type module does not have a shielding effect like a conventional module using PKG, there is a drawback in that it easily receives electrical or magnetic noise from the outside and lowers reception sensitivity. For example, if the reception sensitivity is reduced by 1 dB, the transmission distance is shortened by several km according to the conversion from the transmission loss of the fiber.
[0007]
In order to avoid a decrease in reception sensitivity, the module may be inserted into a metal PKG after being molded with resin, but this is more expensive than a module using a conventional PKG. On the other hand, even if a metal cap is put on the PD or amplifier before molding with resin, it becomes expensive.
[0008]
Therefore, there has been a demand for a module with noise countermeasures while taking advantage of the low cost of the resin mold molding technology, but a module that can satisfy both has not been realized.
[0009]
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an optical transmission module that is low in cost and has noise countermeasures.
[0010]
[Means for Solving the Problems]
An optical transmission module of the present invention includes at least one of a light emitting element, a light receiving element, and an amplifier, and has a connection means for ensuring electrical connection with the outside. At least one of them and the connection means are fixed with a resin mold, the resin mold is covered with a conductive cover, and the conductive cover is connected with at least one connection portion of the connection means. Features.
[0012]
The connecting part may be a fitting part.
[0013]
Here, the fitting portion can have a connecting projection.
[0014]
The conductive cover may be a metal cover.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
The optical transmission module of the present invention is covered with a conductive cover so as to shield the upper part and the left and right parts of the module. In the module, the base portion of the lead frame is grounded, and the lead terminals are electrically connected to the conductive cover and the connecting portion .
[0019]
In the present invention, the connection portion includes a lead terminal and a grip portion of a conductive cover that is fitted to the lead terminal . Moreover, it may consist of a lead terminal having a protruding shape or the like and a fitting portion fitted to the lead terminal, or may be brought into contact by fitting them.
[0020]
The conductive cover is a metal cover .
[0021]
【Example】
Hereinafter, the present invention will be described in more detail with reference to the drawings.
[0022]
FIG. 5A is a plan view showing a structure of an embodiment of an optical transmission module referred to in the present invention, and FIG. 5B is a cross-sectional view of the optical transmission module of FIG. 5A taken along the line AA ′. It is. The lead frame base 12 is resin-molded, and the module body 13 molded with the resin is covered with a metal cover 14. Four protrusions 11 connected to the ground are arranged at the four corners of the metal cover, and are soldered and connected to four of the four lead terminals 15 of the base of the lead frame. An aspect is shown .
[0023]
The outline of the internal structure of the optical transmission module of the present invention is illustrated in FIG. 6, but the present invention is not particularly limited by the difference in internal structure. In FIG. 6, a V-groove is formed in a Si bench 22 having a thickness of 1 mm, and a single-mode optical fiber 21 housed in a ferrule 23 is fixed to the V-groove with an epoxy resin. However, the optical fiber is not limited to a single mode fiber. Next, the Si bench to which the optical fiber is fixed is fixed to the base 24 of the copper lead frame with epoxy resin or the like, and InGaAs placed on the Al ₂ O ₃ submount 25 in the vicinity of the light emitting end face of the optical fiber is used as the light receiving layer. A photodiode (PIN-PD) 26 is soldered with AuSn. An amplifier 27 is fixed behind the photodiode (PD) with a conductive epoxy resin. The amplifier Si-MOS-IC has a function of amplifying a weak signal converted from an optical signal into an electric signal by a photodiode. The terminals of the PD, the amplifier and the lead frame are ball-bonded and electrically connected with an Au wire (not shown) having a diameter of 30 μm. Thereafter, the whole is molded with an epoxy resin.
[0024]
The outline of the receiving circuit of the module after resin molding is illustrated in FIG. Here, the lead terminals 15 at the four corners are grounded. The outer shape is about 10 mm in length, about 15 mm in width, and about 3 mm in height.
[0025]
FIG. 8 shows a state in which a thin copper cover 28 having a thickness of about 0.1 to 0.2 mm is soldered thereon. However, SnPb soldering was used to attach the thin cover.
[0026]
FIGS. 9A to 9C show the optical transmission module of the present invention in which the connecting portion is composed of a fitting portion. FIG. 9B shows an enlarged view of the connection portion 33 in FIG. 9A. Instead of the embodiment shown in FIG. 9B, the connecting portion shown in FIG. 9C may be used. That is, as shown in FIG. 9B, the conductive cover and the lead terminal may be connected so that the grip portion 34 is formed on the conductive cover 31 and the lead terminal 32 is sandwiched between them. As shown in FIG. 9 (c), there is a bulging portion 36 instead of the gripping portion, and it may be connected by being engaged with the concave portion of the lead terminal. Or as shown to Fig.10 (a)-(c), the projection part 37 may be formed in the connection part of an electroconductive cover, and it may connect so that this may get entangled with lead terminal 32 ', or FIG. As shown in a) and (b), the connecting portion of the conductive cover 31 is formed so as to hold the lead terminal 32 ', and a bulging portion that can be fitted to the tip of the lead terminal is provided. You may connect by inserting. Here, FIG. 10A shows the appearance of an optical module in which the connecting portion of the present invention is composed of a fitting portion, FIG. 10B shows an enlarged portion of the connecting portion 33, and FIG. The enlarged view of the connection part of lead terminal 32 'connected to the electroconductive cover in lead terminal 32, 32' is shown. FIG. 11 (a) shows a plan view of an optical module in which the connecting portion of the present invention is constituted by a fitting portion, and FIG. 11 (b) is a cross-section taken along the line BB ′ in FIG. 11 (a). Represents the main part of The reference numerals used here have the same functions unless otherwise specified.
[0027]
Next, the receiving sensitivity was measured using the optical receiving module A with the metal cover shown in FIG. 8 and the optical receiving module B similar to the module of FIG. 7 except that the metal cover was not attached, and the values were compared. . That is, when an optical signal of 155 Mbps was generated using an LD light source with a wavelength of 1.3 μm and the minimum reception sensitivity with a code error rate of 10 ⁻⁹ was measured, it was −39 dBm in the module A with a metal cover. However, a difference of -35 dBm was confirmed in module B without a metal cover .
[0028]
In addition, the optical transmission module of the present invention is a module in which at least one lead terminal is sandwiched by a grip portion of an inexpensive metal cover after being molded with a resin mold, and a metal PKG is not used for the shield. Was able to keep costs low.
[0029]
【The invention's effect】
As described above in detail, according to the present invention, it is possible to realize an optical transmission module that can easily block external noise by using an inexpensive manufacturing technique called resin molding.
[0030]
In addition, although the said Example demonstrated the case of the receiver, this invention exhibits an effect also in a transmitter, and in the case of a transmitter, there exists an effect which does not diverge an electrical signal outside. In addition, the transmitter and receiver are often placed close to each other, but by covering each with an inexpensive conductive cover, mutual interference can be eliminated, and not only miniaturization and cost reduction, but also the whole It is also possible to exert a great effect on downsizing the space.
[Brief description of the drawings]
FIG. 1 is a perspective view of a conventional coaxial module.
FIG. 2 is a perspective view of a conventional DIL-PKG type module.
FIG. 3 is a perspective view of a conventional GAL-wing type module.
FIG. 4 is a perspective view of a conventional resin mold module.
5A is a plan view showing an embodiment of an optical transmission module referred to in the present invention, and FIG. 5B is a cross-sectional view of the optical transmission module .
FIG. 6 is a conceptual diagram showing an internal structure of an optical transmission module according to the present invention.
FIG. 7 is a conceptual diagram of a circuit when optical transmission is performed using the optical transmission module of the present invention.
FIG. 8 is a plan view showing a state where a copper cover is attached to the optical transmission module referred to in the present invention.
9A is a perspective view of the optical transmission module of the present invention, FIG. 9B is a cross-sectional view showing one embodiment of a connection portion between a lead terminal and a conductive cover, and FIG. 9C is a lead terminal. It is sectional drawing which shows another aspect of the connection part of an electroconductive cover.
10A is a plan view of an optical transmission module of the present invention, FIG. 10B is a perspective view showing a connection portion between a lead terminal and a conductive cover, and FIG. It is an enlarged plan view which shows a connection part with a cover.
11A is a plan view of an optical transmission module according to the present invention, and FIG. 11B is a cross-sectional view showing a main part of a cross section showing a connection portion between a lead terminal and a conductive cover.
[Explanation of symbols]
1 Optical fiber 2 Lead 3 PKG
4 Cap 5 Resin Mold 11 Ground Pin 12 Lead Frame Base 13 Resin Molded Module Body 14 Metal Cover 15 Lead Terminal 16 Solder Part 21 Optical Fiber 22 Si Bench 23 Ferrule 24 Lead Frame Base 25 Submount 26 PD ( Photodiode)
27 Amplifier 28 Copper Cover 31 Conductive Covers 32, 32 ′ Lead Terminal 33 Connection Portion 34 Holding Portion 35 Module Body 36 Swelling Portion 37 Protrusion Portion

Claims (1)

A lead frame having connection means for securing an electrical connection with the outside including a connection portion with at least one conductive cover on which at least one of a light emitting element, a light receiving element and an amplifier is mounted ;
A resin mold in which the lead frame and at least one of a light emitting element, a light receiving element and an amplifier mounted thereon are integrated and molded;
A metal conductive cover covering the resin mold;
An optical transmission module comprising :
The provided mutually engageable convex portions or concave portions of the conductive grip of the cover and the connecting portion of the lead frame, the gripping portion of the conductive cover by sandwiching the connecting portion of the lead frame, the conductive The conductive cover covering the resin mold and the lead frame are electrically connected to each other, and the convex part or the concave part provided in the conductive cover is fitted into the concave part or the convex part provided in the connecting portion of the lead frame, and the machine is mutually connected. Optical transmission module, characterized in that the optical transmission module is fixed .

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