JPH05218461A - Optical receiving module - Google Patents

Abstract

PURPOSE:To provide an optical receiving module where the height of a first wire bond has the same level as that of a second wire bond so as to lessen wire bonds in number and length. CONSTITUTION:A metal base 21 where an amplification integrated circuit 12 is mounted is set in height so as to enable a sub-carrier 13 where a photodetective element 11 is mounted to be level with the amplification integrated circuit 12. Furthermore, a metallized wiring metal on the sub-carrier 13 and the input pad of the amplification integrated circuit 12 are directly connected together with a wire bond 19 not through the intermediary of an HIC substrate 14. The substrate 14 as thick as the circuit 12 is arranged adjoining to the circuit 12. Furthermore, the output pad of the circuit 12 and a transmission line located on the substrate 14 are connected together with a wire bond 20 as short as possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical receiver module, and more particularly to an optical receiver module for optical communication whose signal transmission band exceeds 1 GHz.

[0002]

2. Description of the Related Art In a conventional optical receiving module, an amplifier integrated circuit is mounted on a HIC substrate as described in Japanese Patent Application No. 1-199620, for example, and an electric signal is connected or a DC bias is applied. The wire bond used for supply needs at least a length for connecting a step difference in substrate thickness of the amplifier integrated circuit.

Further, since a wire bond is once connected to the HIC substrate between the sub-carrier on which the light receiving element is mounted and the input pad of the amplification integrated circuit, between the sub-carrier and the HIC substrate and between the HIC substrate and the amplification integrated circuit. Two wire bonds were needed between the circuits.

FIG. 2 shows the conventional module described above. In the conventional optical receiving module, the light receiving element 51 is mounted on the subcarrier 52, and the amplifying element 53 is mounted on the HIC 54. The weak optical signal guided from the optical fiber 55 reaches the light receiving element 51 by the lens 56, is photo-electrically converted, and is input to the amplifying element 53. The output signal of the amplification element 53 is guided to the output of the package 60 of the module. Reference numeral 57 is a pipe, 58 is a metal plate, 59 is a metal base, and 60 is a package.

[0005]

However, according to the prior art, the output pad of the amplifier integrated circuit is replaced with the H
There is a drawback that the inductance due to the wire bond becomes large up to the transmission line for the signal of the IC, and the standing voltage ratio of the output voltage of the optical receiving module becomes large especially in the high frequency region of the transmission band.

Further, unnecessary peaking of LC resonance or dip of frequency characteristic is transmitted due to coupling between the inductance of the wire bond used for supplying the DC bias of the amplifier integrated circuit and the parasitic capacitance in the amplifier integrated circuit. There was a drawback that occurred within the band.

Similarly, the wire bond inductance between the light receiving element and the amplification integrated circuit, the wire bond inductance between the light receiving element and the subcarrier, the junction capacitance of the light receiving element, the capacitance of the subcarrier, and the parasitic capacitance. There is a drawback that unnecessary peaking of LC resonance or dip of frequency characteristic occurs in the transmission band due to the coupling with.

The present invention has been made in view of the above points. An object of the present invention is to suppress the inductance caused by wire bonds so that unnecessary peaking or dip in frequency characteristics does not occur in the transmission band, and thus to reduce the number of wire bonds and shorten the length of wire bonds. An object of the present invention is to provide an optical receiver module having a structure capable of improving the receiving sensitivity by matching the height of the first bond and the height of the second bond.

[0009]

The above object is to adopt a substrate having the same chip thickness as the HIC substrate for supplying a DC bias or transmitting an output signal of the amplifier integrated circuit. The HIC substrate and the amplification integrated circuit are mounted adjacent to each other on the same metal base, and the height of the signal output electrode pattern of the subcarrier of the light receiving element and the height of the input pad of the amplification integrated circuit are set. Directly wire-bonded between the sub-carrier and the input pad of the amplifier integrated circuit by arranging them to be the same, and between the output pad of the amplifier integrated circuit of the same height and the transmission line on the HIC substrate. Is achieved by wire bonding as short as possible.

[0010]

Generally, in an integrated circuit, the input / output pad is formed to have a small area in order to reduce the capacitance generated between the input / output pad and the back surface GND of the integrated circuit chip. Further, if the thickness of the integrated circuit chip is reduced, the wire bond length is shortened, and thus the inductance is reduced, but the capacitance is inversely proportional to the thickness, and conversely increases.

On the other hand, when the diameter of the wire bond is increased, the inductance is reduced, but it is necessary to increase the pad area of the integrated circuit chip, and the capacitance between the back surface GND is increased.

In the above, a method of mounting the integrated circuit on the HIC and increasing the number of wire bonds can be considered. However, even if two wire bonds are connected in parallel with each other in the same length, the total inductance is reduced to about 70% of the case of one wire. Since it occurs, it has a negative effect when considered comprehensively.

Further, the capacitance value is a factor that narrows the band of the optical receiving module due to the time constant determined by the product of the resistance value, and therefore it must be reduced as much as possible. Therefore, it is customary to design the light-receiving element and the integrated circuit so that the capacitance value is reduced even at the expense of the negative surface where the inductance due to wire bonding is slightly increased.

From the above, in order to prevent unnecessary peaking or frequency characteristic dips in the transmission band, the wire bond should be as short as possible and LC
If the resonance frequency is set to a high frequency region which is at least about twice as high as the transmission band, it is possible to prevent deterioration of the reception sensitivity of the optical receiving module due to deterioration of the frequency characteristic.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing an embodiment of the present invention.

In FIG. 1, the weak optical signal transmitted through the optical fiber 15 is condensed by the lens 16 to be received by the light receiving element 1.
Reach 1. After being photo-electrically converted by the light receiving element 11, the wire electrode 18 is connected to the metal electrode of the subcarrier 13 on which the light receiving element is mounted. It is further connected to the amplifier integrated circuit 12 by a wire bond 19 through a wiring metal metalized on the subcarrier. Amplification integrated circuit 1
2 is mounted on the same metal base 21 adjacent to the HIC board 14. Usually, the chip thickness of the amplifier integrated circuit is 0.6 mm in consideration of the pad capacitance or the manufacturing process. If you select the same HIC substrate as this chip thickness,
High-frequency signal is transmitted and the compatibility with wire bonds makes it possible to use a ceramic substrate made of alumina with a thickness of 0.635 mm.
Thick ones are suitable. The output signal amplified by the amplifier integrated circuit 12 is connected to the transmission line on the HIC substrate 12 by the wire bond 20. The output signal that has passed through the transmission line is connected to the output terminal of the package 22 and guided to the circuit at the subsequent stage. A pipe 17 holds the optical fiber 15 and the lens 16.

[0018]

As described above, according to the present invention, in order to improve the receiving sensitivity, the heights of wire-bonding the sub-carrier of the light receiving element and the amplification integrated circuit are made the same, and the amplification integrated circuit and the HIC substrate are made. To provide an optical receiver module receiving circuit having a structure in which the number of wire bonds can be reduced and the length can be shortened by making the same wire-bonding heights, and the inductance can be reduced. You can

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the structure of the prior art.

[Explanation of symbols]

11 ... Light receiving element, 12 ... Amplification integrated circuit, 13 ... Subcarrier, 14 ... HIC substrate, 15 ... Optical fiber, 16 ... Lens, 17 ... Pipe, 18, 19, 20 ... Wire bond, 21 ... Metal base, 22 ... Package, 51 ... Light receiving element of prior art example, 52 ... Sub carrier of prior art example,
53 ... Amplifying element of prior art example, 54 ... HI of prior art example
C, 55 ... Optical fiber of prior art example, 56 ... Lens of prior art example, 57 ... Pipe of prior art example, 58 ... Metal plate of prior art example, 59 ... Metal base of prior art example, 60 ... Conventional art example Package.

Claims (1)

[Claims] 1. A light-receiving element, at least one integrated circuit for amplifying a weak signal converted into an electric signal by the light-receiving element without S / N deterioration, and for supplying a DC bias of the amplification integrated circuit. HI for transmitting output signals
In a light receiving module including a C substrate, an optical fiber for guiding an optical signal to a light receiving element, and an optical component for guiding the light signal to the light receiving element, the subcarrier on which the light receiving element is mounted and the amplification integrated circuit are at the same height. By arranging so that the amplification integrated circuit and the HIC substrate are arranged at the same height, it is possible to suppress the inductance due to the wire bond used for the connection of electric signals or the DC bias supply. Optical receiver module characterized by structure.