JP2007242708A - Light receiving subassembly - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light receiving module manufactured by the minimum number of components without changing arrangement of a lead pin with respect to an amplifier where various power terminals are arranged. <P>SOLUTION: A light receiving sub-assembly 100 has a metallized substrate 15 loading a light receiving element 20, and the amplifier 22 amplifying an output signal of the light receiving element. The metallized substrate comprises a dielectric substrate 28; and a first electrode 16, a second electrode 17, a pad electrode 18, and a resistor 19 are formed on an upper face. A lower face of the light receiving element is die-bonded to the first electrode. The pad electrode is connected to the first electrode through the resistor, and is connected to a first lead pin 14 by wiring. The second electrode 17 is connected to the power terminal of the amplifier by wiring, and is connected to a second lead pin 13 by wiring. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical receiving subassembly including a light receiving element and an amplifier.

An optical receiver used for optical communication amplifies the output of a receiver optical sub-assembly (ROSA) that performs photoelectric conversion and the sub-assembly, and monitors and controls the entire optical receiver. It is common to include a main circuit. The structure of the subassembly is disclosed in Patent Document 1 below, for example. The subassembly includes a light receiving element and a transimpedance amplifier (TIA), and a weak current converted from light by the light receiving element is amplified by the TIA and output to the outside of the subassembly. The subassembly itself is very small. Usually, a light receiving element, a TIA, a filter component for a bias line of the light receiving element, and the like are mounted on a stem having a diameter of about 4 mm to 6 mm.
JP 7-31430 A

  The specification of TIA varies depending on the chip on which the TIA is mounted, and the position of the power supply terminal on the chip is not shared. On the other hand, since the layout change of the main circuit board connected to the subsequent stage of the subassembly hinders mass production, it is desirable to make the arrangement of the lead pins of the subassembly common. For this reason, depending on the TIA chip, a wire connected to the power supply terminal of the TIA may be routed on a stem having a small mounting area, and a predetermined lead pin arrangement may be realized using an additional mounting component. .

  For example, as shown in FIG. 1, if the power terminal 24 of the TIA 22 is disposed relatively close to the power supply voltage lead pin 13, there is no need to use an additional mounting component. However, as shown in FIG. 2, when the power terminal 24 of the TIA 22 is far from the lead pins 13, it is necessary to add a metallized substrate 35 and perform mounting. However, adding a metallized substrate to route the wires within the subassembly is undesirable from the standpoint of reducing component and mounting costs.

  Therefore, an object of the present invention is to provide an optical receiver module that can be manufactured with a minimum number of parts without changing the arrangement of lead pins for amplifiers having various power terminal arrangements.

  An optical receiving subassembly according to the present invention has a pair of electrodes on an upper surface and a lower surface, a light receiving element that converts an optical signal incident on the upper surface into an electrical signal, a metallized substrate on which the light receiving element is mounted, and a light receiving element. An amplifier that receives and amplifies an electrical signal, a conductive stem on which the amplifier and the metallized substrate are mounted, and first and second lead pins that penetrate the stem and are insulated from the stem. The metallized substrate includes a dielectric substrate. The upper surface of the dielectric substrate is connected to the first resistor, the light receiving element connection electrode to which the lower surface of the light receiving element is die-bonded, and the light receiving element connecting electrode through the first resistor. A light receiving element external connection electrode connected to the first lead pin by the wiring, and an amplifier power supply terminal electrode connected to the power supply terminal of the amplifier by the wiring and connected to the second lead pin by the wiring. Is formed.

  By arranging the amplifier power supply terminal electrode between the power supply terminal of the amplifier and the second lead pin, the wire can be easily routed. For this reason, it is possible to appropriately wire the amplifiers having various power supply terminal arrangements without changing the arrangement of the lead pins. Since the amplifier power supply terminal electrode is formed on the metallized substrate on which the light receiving element is mounted, it is not necessary to install an additional mounting component on the stem. Therefore, the optical receiver module according to the present invention can be manufactured with a minimum number of parts.

  On the upper surface of the dielectric substrate, a shield electrode is further formed extending between the region where the light receiving element connection electrode, the first resistor and the light receiving element external connection electrode are formed, and the amplifier power supply terminal electrode. It may be. The shield electrode is connected to the stem by wiring.

  Depending on the thickness of the dielectric substrate included in the metallized substrate, there is a possibility that the amplifier power supply terminal electrode and the light receiving element connection electrode are capacitively coupled. However, the shield electrode shields the amplifier power supply terminal electrode from the first resistor, the light receiving element connection electrode, and the light receiving element external connection, thereby providing the amplifier power supply terminal electrode and the light receiving element connection electrode. Prevent direct capacitive coupling. Thereby, various inconveniences associated with this capacitive coupling can be avoided.

  The electrode for the amplifier power supply terminal includes a first portion connected to the power supply terminal of the amplifier by wiring and a second portion separated from the first portion and connected to the second lead pin by wiring. May be included. A second resistor connected between the first and second portions may be further formed on the upper surface of the dielectric substrate.

  The second resistor functions as a damping resistor inserted in the power supply line of the amplifier. This damping resistor enhances the filtering effect of the filter composed of the capacitance between the amplifier power supply terminal electrode and the stem and the wire inductor. As a result, high frequency noise is satisfactorily removed from the power supply voltage supplied to the amplifier.

  ADVANTAGE OF THE INVENTION According to this invention, the optical receiver module which can be manufactured with the minimum number of parts can be provided, without changing arrangement | positioning of a lead pin with respect to the amplifier of various power supply terminal arrangement | positioning.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

First Embodiment FIG. 3 is a plan view showing an upper surface of a stem of an optical transmission subassembly 100 according to a first embodiment. The stem 10 is a disk-shaped conductor, and lead pins 11 to 14 are attached thereto. The lead pins 11 to 14 penetrate the stem 10, and their tips protrude from the upper surface of the stem 10. Since an insulating sealing glass is interposed between the stem 10 and the lead pins 11 to 14, the stem 10 and the lead pins 11 to 14 are insulated.

  A metallized substrate 15 and a transimpedance amplifier (hereinafter “TIA”) 22 are mounted on the upper surface of the stem 10. Generally, a metallized substrate has a dielectric substrate as its base, an electrode formed entirely or partially on the upper surface of the dielectric substrate, and a solid metallized electrode that covers the entire lower surface of the dielectric substrate. is doing.

  FIG. 4 is a plan view showing the metallized substrate 15, where (a) shows the upper surface of the metallized substrate 15 and (b) shows the lower surface. The metallized substrate 15 includes a dielectric substrate 28 as its base. A first electrode 16, a second electrode 17, a pad electrode 18 and a damping resistor 19 are formed on the upper surface of the dielectric substrate 28. The lower surface of the dielectric substrate 28 is entirely covered with a solid metallized electrode 27. The first electrode 16 is connected to the pad electrode 18 via a damping resistor 19. The pad electrode 18 is connected to the lead pin 14 via the wire 40. The second electrode 17 is spaced from the first electrode 16, the pad electrode 18 and the damping resistor 19 and is therefore insulated from them.

  The electrode forming method on the upper surface of the metallized substrate 15 is as follows. First, a metal thin film made of a material such as NiCr, Ti, or Mo having excellent adhesion to the dielectric substrate 28 is partially formed on the upper surface of the dielectric substrate 28. For this formation, a mask method or an etching method is used. Thereafter, the portion corresponding to the electrode on the obtained metal thin film is plated with a metal (for example, Au) that is easy to wire and has a low electrical resistance. Thereby, the electrodes 16, 17 and 18 are formed. A portion that has not been plated becomes a damping resistor 19 because the electrical resistance is large.

  On the first electrode 16 of the metallized substrate 15, a photodiode (hereinafter “PD”) 20 is mounted as a light receiving element. The PD 20 has a chip shape, and one of an anode and a cathode is provided on the upper surface, and the entire lower surface is covered with the other of the anode and the cathode. The PD 20 converts an optical signal incident on its upper surface into an electrical signal. The lower surface of the PD 20 is die-bonded to the first electrode 16, whereby the electrode on the lower surface of the PD 20 is connected to the first electrode 16. As described above, the first electrode 16 is electrically connected to the lead pin 14, and a bias voltage necessary for driving the PD 20 is supplied from the lead pin 14 to the PD 20 via the pad electrode 18, the damping resistor 19, and the first electrode 16. Applied.

  The metallized substrate 15 also has a role of a capacitor inserted between the electrode (namely, bias terminal) on the lower surface of the PD 20 and the stem 10 (namely, ground potential).

  The TIA 22 receives and amplifies the electrical signal output from the PD 20. In an optical receiver used in optical communication, a main circuit is connected to the subassembly 100. The main circuit includes an amplifier that further amplifies the amplified electric signal. The TIA 22 is a first-stage amplifier in the series of amplifiers.

  The TIA 22 has a chip shape, and has four terminal electrodes 23 to 26 on the upper surface thereof. The terminal electrode 23 is a terminal for receiving an electrical signal from the PD 20, and is connected to the electrode on the upper surface of the PD 20 via the wire 41.

  The terminal electrode 24 is a power supply terminal for receiving a power supply voltage, and is connected to the second electrode 17 on the metallized substrate 15 through a wire 42. The second electrode 17 is also connected to the lead pin 13 via another wire 43. The lead pin 13 thus electrically connected to the terminal electrode 24 is connected to a power supply outside the subassembly 100 and supplies a power supply voltage to the TIA 22.

  The terminal electrodes 25 and 26 are differential output terminals for outputting an electric signal amplified by the TIA 22, where the terminal electrode 25 is a positive phase output terminal and the terminal electrode 26 is a negative phase output terminal. The terminal electrodes 25 and 26 are respectively connected to the lead pins 11 and 12 by wiring. The electric signal amplified by the TIA 22 is output from the lead pins 11 and 12.

  On the upper surface of the stem 10, a cap with a lens (not shown) that covers the tips of the lead pins 11 to 14, the metallized substrate 15, and the TIA 22 is installed. The optical receiving subassembly 100 further includes an optical fiber (not shown) optically connected to the light receiving portion of the PD 20 and a ferrule (not shown) that holds the tip of the optical fiber. The ferrule is accommodated in a sleeve (not shown) fixed to the stem 10 or the cap. The PD 20 receives the optical signal transmitted through the optical fiber and converts it into an electrical signal.

  As described above, the second electrode 17 for the power supply line of the TIA 22 is provided on the metallized substrate 15 juxtaposed to the TIA 22 in addition to the first electrode 16 for the bias line of the PD 20. In the present embodiment, the terminal electrode 24 is not directly wire-bonded to the lead pin 14, but the terminal electrode 24 and the electrode 17, and the electrode 17 and the lead pin 14 are connected by separate wires 42 and 43, respectively. Accordingly, it is possible to wire the wires without crossing the wires or straddling the upper part of the light receiving portion of the PD 20 regardless of the position of the terminal electrode 24. It should be noted that the intersection of the wires reduces the reliability of the subassembly 100. In addition, the wire straddling the light receiving unit lowers the optical signal power that can be received by the PD 20.

  For comparison, an example of a conventional metallized substrate is shown in FIG. Here, (a) shows the upper surface of the conventional metallized substrate 55, and (b) shows the lower surface. In the prior art, an electrode 16 for applying a bias voltage to the PD 20, a pad electrode 18, and a damping resistor 19 are formed on almost the entire upper surface of the dielectric substrate 28.

  In contrast, in the metallized substrate 15 used in the present embodiment, the bias voltage application electrode 16 to the light receiving element 20 and the power supply voltage application electrode 17 to the TIA 22 are provided at two positions on the upper surface of the metallized substrate 15. Is formed. The metallized substrate 15 can be manufactured by the same method as the conventional metallized substrate 55 by changing the metal mask for the upper surface. Therefore, the manufacturing cost of the metallized substrate 15 is exactly the same as that of the conventional metallized substrate 55.

  Thus, by arranging the second electrode 17 between the terminal electrode 24 and the lead pin 13, the wire can be easily routed. For this reason, it is possible to appropriately perform the wiring without changing the arrangement of the lead pins 11 to 14 with respect to TIA having various power terminal arrangements. Since the second electrode 17 is formed on the metallized substrate 15 on which the PD 20 is mounted, it is not necessary to install an additional mounting component on the stem 10. Therefore, the optical receiving module 100 can be manufactured with a minimum number of parts.

  Another advantage is that the power supply filter of the TIA 22 is formed by wire bonding the second electrode 17 on the metallized substrate 15 to the lead pin 13. The electrode 17 is capacitively coupled to the stem 10 (ground potential) via the dielectric substrate 28. The capacitance between the electrode 17 and the stem 10 forms an inductor of the wire 43 and an LC filter. Thereby, a large filtering effect is obtained, and high frequency noise can be appropriately removed from the power supply voltage supplied to the TIA 22.

Second Embodiment FIG. 6 is a plan view showing an upper surface of a stem of an optical transmission subassembly 100a according to a second embodiment. FIG. 7 is a plan view showing the metallized substrate 15a used in the optical transmission subassembly 100a, where (a) shows the upper surface of the metalized substrate 15a and (b) shows the lower surface.

  In the first embodiment, depending on the thickness of the metallized substrate 15, there is a possibility that the bias line for the PD 20 and the power line for the TIA 22 are capacitively coupled. The TIA 22 induces noise in the power supply line. However, when the bias line and the power supply line are coupled, the noise may be input to the input terminal of the TIA 22, that is, the terminal electrode 23 through the junction capacitance of the PD 20. Even if the TIA 22 does not induce noise in the power supply line, if the bias line and the power supply line are coupled, a kind of feedback circuit is formed, and the system may oscillate.

  In order to avoid these disadvantages, in the second embodiment, a conductive guard pattern 30 is formed on the metallized substrate 15a as a shield electrode. The guard pattern 30 has a rectangular pad portion 30a and an elongated extension portion 30b extending from the pad portion 30a. The pad portion 30 a is connected to the stem 10 by a wire 32. The pad portion 30 a and the extension portion 30 b extend between the second electrode 17 and the region where the first electrode 16, the damping resistor 19 and the pad electrode 18 are formed.

  Thus, the guard pattern 30 surrounds the second electrode 17 from three directions, thereby shielding the second electrode 17 from the first electrode 16, the damping resistor 19, and the pad electrode 18. As a result, direct capacitive coupling between the electrodes 16 and 17 can be prevented, and the above-mentioned various disadvantages can be avoided.

  The present invention has been described in detail based on the embodiments. However, the present invention is not limited to the above embodiment. The present invention can be variously modified without departing from the gist thereof.

  In the first and second embodiments, the damping resistor is provided only on the bias line of the PD 20, but it is easy to provide the damping resistor also on the power supply line of the TIA 22. Specifically, the second electrode 17 is formed as two parts separated from each other, one part is connected to the terminal electrode 24 by wiring, and the other part is connected to the lead pin 13 by wiring. Further, a damping resistor connected between these two portions is formed on the upper surface of the metallized substrate 15 or 15a. Thus, a larger filtering effect can be obtained by inserting a damping resistor on the power supply line of the TIA 22. As a result, high frequency noise can be further removed from the power supply voltage supplied to the TIA 22.

  In the above embodiment, a photodiode is used as the light receiving element and a transimpedance amplifier is used as the amplifier. However, other light receiving elements and amplifiers may be used.

It is a top view which shows the stem upper surface of the conventional optical transmission subassembly. It is a top view which shows the stem upper surface of the conventional optical transmission subassembly. It is a top view which shows the stem upper surface of the optical transmission subassembly which concerns on 1st Embodiment. It is a top view which shows the upper surface and lower surface of the metallization board | substrate which concern on 1st Embodiment. It is a top view which shows the upper surface and lower surface of the conventional metallization board | substrate. It is a top view which shows the stem upper surface of the optical transmission subassembly which concerns on 2nd Embodiment. It is a top view which shows the upper surface and lower surface of the metallization board | substrate which concerns on 2nd Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Stem, 11-14 ... Lead pin, 15, 15a ... Metallized board, 16 ... 1st electrode, 17 ... 2nd electrode, 18 ... Pad electrode, 19 ... Damping resistance, 20 ... Light receiving element, 23-26 ... Terminal electrode 27 ... Metallized electrode, 28 ... Dielectric substrate, 30 ... Guard pattern, 32 ... Wire, 35 ... Metalized substrate, 40-43 ... Wire, 55 ... Metallized substrate, 100, 100a ... Optical receiving subassembly

Claims (3)

A light receiving element having a pair of electrodes on an upper surface and a lower surface, and converting an optical signal incident on the upper surface into an electrical signal;
A metallized substrate on which the light receiving element is mounted;
An amplifier for receiving and amplifying the electrical signal from the light receiving element;
A conductive stem carrying the amplifier and the metallized substrate;
First and second lead pins penetrating the stem and insulated from the stem;
An optical receiver subassembly comprising:
The metallized substrate includes a dielectric substrate, and on the upper surface of the dielectric substrate,
A first resistor;
A light receiving element connection electrode to which the lower surface of the light receiving element is die-bonded;
A light receiving element external connection electrode connected to the light receiving element connecting electrode via the first resistor and connected to the first lead pin by wiring;
An amplifier power supply terminal electrode connected to the power supply terminal of the amplifier by wiring and connected to the second lead pin by wiring;
An optical receiver subassembly is formed.   On the upper surface of the dielectric substrate, a shield extending between the region for forming the light receiving element connection electrode, the first resistor, and the light receiving element external connection electrode and the amplifier power supply terminal electrode The optical receiver subassembly of claim 1, further comprising an electrode, wherein the shield electrode is connected to the stem by wiring. The amplifier power supply terminal electrode is:
A first portion connected to the amplifier power supply terminal by wiring;
A second portion spaced from the first portion and connected to the second lead pin by wiring;
Contains
3. The optical receiving subassembly according to claim 1, wherein a second resistor connected between the first and second portions is further formed on an upper surface of the dielectric substrate.

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