KR20120091994A

KR20120091994A - Optical module

Info

Publication number: KR20120091994A
Application number: KR1020110106050A
Authority: KR
Inventors: 강세경; 이준기; 허준영
Original assignee: 한국전자통신연구원
Priority date: 2011-02-10
Filing date: 2011-10-17
Publication date: 2012-08-20

Abstract

PURPOSE: An optical module is provided to reduce manufacturing costs by executing high speed operation without coating a plurality of insulating layers on a lead pin. CONSTITUTION: An optical module(100) comprises a stem(110), an optical device(120), a data signal lead pin, a printed circuit board(140), and a post part(150). The optical device is mounted at one surface of the stem. The data signal lead pin is connected to the optical device and passes through the stem. The data signal lead pin is projected to the other surface of the stem. A data signal transmission line for connection with the data signal lead pin is formed at one surface of the printed circuit board. A reinforcement part is projected at the other surface of the printed circuit board. The post part is projected on the stem. The post part is closely adhered to the reinforcement par and supports the printed circuit board. The post part comprises a coupling part combined with the reinforcement part.

Description

Optical module

The present invention relates to an optical module, and more particularly, to an optical module having an improved structure to enable high speed operation.

With the speed and miniaturization of optical communication systems, conventional optical modules in the form of Transistor Outline-CAN (TO-CAN) have electrical characteristics constraints for use at 10 Gbps or more. This is because most of the thio-can packages currently in use have a 90 degree bent signal flow when connected to a flexible printed circuit board (FPCB).

1 illustrates a connection structure between a thio-can package and a FPCB according to the related art. As shown in FIG. 1, a through hole 12 is formed in the transmission line 11 of the FPCB 10. Since the signal lead pin 21 of the thio-can package 20 is inserted into the through hole 12 and then bonded through soldering, the signal lead pin 21 is connected to the transmission line 11 of the FPCB 10. ) Is connected. Accordingly, the signal flow between the signal lead pin 21 and the transmission line 11 is 90 degrees. In this case, when the signal lead pin 21 is a data signal lead pin, an impedance discontinuity occurs due to a connection portion between the data signal lead pin and the through hole 12, which adversely affects signal integrity.

This can be confirmed through the graph shown in FIG. 2. Here, the FPCB 10 has a transmission distance of 12 mm and is designed to have a characteristic impedance of 50 Ω. As shown in FIG. 2, since the transmission loss (S21) increases in the high frequency band and the reflection value S11 increases, the structure is difficult to use in the high frequency band.

On the other hand, the thio-can package is an example in which the electrical properties are greatly improved by coating a plurality of insulating layers on the lead for high speed operation. However, the thio-can package described above may have a complicated structure, which may have a disadvantage in that manufacturing cost is increased.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical module that can be used at a higher transmission speed and can be configured at a low cost since the flow path of the data signal is not bent when the data signal lead pin and the printed circuit board are connected. .

Optical module according to the present invention for achieving the above object, a stem; An optical element mounted on one surface of the stem; Data signal lead pins connected to the optical device and protruding from the stem to the other surface of the stem; A printed circuit board having data signal transmission lines for connecting to the data signal lead pins on one surface thereof and having a reinforcing portion protruding in a portion of the other surface; And protruding from the other surface of the stem, wherein the data signal lead pins are connected to the reinforcement part so as to be connected in a straight line on the data signal transmission lines to support the printed circuit board. It includes a post portion having a coupling portion to be coupled.

According to the present invention, since the flow path of the data signal does not bend and forms a straight line, it may be advantageous in terms of frequency bandwidth limitation and signal integrity due to impedance discontinuity. Therefore, the present invention can be used even at a higher transmission speed than in the related art, and can be operated at high speed without covering a plurality of insulating layers on the lead pins, which may be advantageous in reducing manufacturing costs.

Further, according to the present invention, since the data signal lead pin and the data signal transmission line are connected without an air gap, the impedance discontinuity point in the high frequency band does not occur, and thus the signal distortion phenomenon may be prevented.

1 is a side view showing a connection structure of a conventional thio-can package and FPCB.
FIG. 2 is a graph showing electrical characteristics of a thio-can package having a connection structure of FIG. 1. FIG.
3 is a side view of an optical module according to a first embodiment of the present invention;
Figure 4 is a perspective view of the structure shown in Figure 3, the printed circuit board is connected to the stem.
5 is an exploded perspective view of FIG. 4.
6 is a side cross-sectional view showing a connection state between a data signal lead pin and a data signal transmission line in FIG.
FIG. 7 is a perspective view of the mounting surface of the stem in FIG. 3; FIG.
8 is a graph showing the electrical characteristics of the optical module shown in FIG.
9 is a side view of an optical module according to a second embodiment of the present invention.
10 is an exploded perspective view of FIG. 9;

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

3 is a side view of an optical module according to a first embodiment of the present invention. 4 is a perspective view illustrating a structure in which a printed circuit board is connected to a stem in FIG. 3. 5 is an exploded perspective view of FIG. 4. 6 is a side cross-sectional view illustrating a connection state between a data signal lead pin and a data signal transmission line in FIG. 3.

3 to 6, the optical module 100 includes a stem 110, an optical device 120, data signal lead pins 130, a printed circuit board 140, and a post part. (post portion, 150).

The stem 110 functions as a base in the optical module 100. The optical device 120 is mounted on one surface of the stem 110. The electronic device 121 may be mounted on the mounting surface of the stem 110 in addition to the optical device 120. Sub-mounts (not shown) may be mounted on the stem 110, and an optical device 120 and an electronic device 121 may be mounted on the sub-mount.

If the optical module 100 is a module having a light receiving function, the optical device 120 is formed of a light receiving device such as a photo diode. Here, the electronic device 121 may include a trans-impedance amplifier (TIA) for amplifying a current signal output from the light receiving device into a voltage signal. If the optical module 100 is a module having a light transmission function, the optical device 120 is formed of a light emitting device such as a laser diode. Here, the electronic device 121 may include a photodiode for a monitor for monitoring the light output of the light emitting device.

The cap 101 may be mounted on the mounting surface of the stem 110 to surround and protect the optical device 120 and the electronic device 121. The cap 101 may have a structure having an inner space and opening at both sides. The cap 101 has one opening coupled to the mounting surface of the stem 110 in a state where the optical device 120 and the electronic device 121 are accommodated in the inner space. The lens 102 is mounted in the other opening of the cap 101. The lens 102 is for aligning between the optical fiber 103 and the optical device 120.

The data signal lead pins 130 penetrate the stem 110 and protrude toward the other surface of the stem 110, that is, the surface opposite to the mounting surface of the stem 110. The data signal lead pins 130 may protrude in a direction perpendicular to the other surface of the stem 110. The data signal lead pins 130 are connected to the optical device 120.

Data signal transmission lines 141 for connection with the data signal lead pins 130 are formed on one surface of the printed circuit board 140. The data signal transmission lines 141 may be arranged side by side at the same interval as that of the data signal lead pins 130 on the printed circuit board 140. A stiffener 145 protrudes from a portion of the other surface of the printed circuit board 140.

The post portion 150 protrudes from the other surface of the stem 110. When the printed circuit board 140 is inserted between the post part 150 and the data signal lead pins 130 with the other side of the printed circuit board 140 facing the post part 150, the post part 150 is filled with data. The signal lead pins 130 are in close contact with the reinforcement part 145 so as to be connected in a straight line on the data signal transmission lines 141 to support the printed circuit board 140.

In addition, the post part 150 includes a coupling part 151 coupled to the reinforcing part 145. When the coupling part 151 of the post part 150 is configured to be coupled to the reinforcement part 145 of the printed circuit board 140, the reinforcement part 145 is disposed on the post part 150 without the coupling part 151. Compared to the structure in close contact, the effect that the printed circuit board 140 is supported by the post unit 150 may be increased. Accordingly, the data signal lead pins 130 may be more stably connected to the data signal transmission lines 141.

As described above, since the data signal lead pins 130 are connected to each other in a straight line on the data signal transmission lines 141 of the printed circuit board 140, the flow paths of the data signals are not bent, and thus the straight line forms a straight line shape. Is achieved. This may be advantageous in terms of frequency bandwidth limitation and signal integrity due to impedance discontinuity at the connection portion of the data signal lead pin 130 and the data signal transmission line 141 as compared with the conventional structure shown in FIG. 1. Therefore, the above-described optical module 100 can be used at a higher transmission speed than in the related art, and can be operated at high speed without covering a plurality of insulating layers on the data signal lead pins 130, which can be advantageous in reducing manufacturing costs. .

On the other hand, as shown in Figure 6, the reinforcing portion 145 is extended to one end of the printed circuit board 140 so that one end is in close contact with the other surface of the stem 110, the coupling portion 151 is a post portion 150 While contacting the other end of the reinforcing portion 145 from the protruding end of the bent may be in contact with the other surface of the printed circuit board 140 may include a protruding portion (151a). For example, the bent portion 151a is formed integrally with the post portion 150, and the post portion 150 including the bent portion 151a may have an approximately 'L' shape.

Accordingly, one end of the reinforcement part 145 is in close contact with the other surface of the stem 110 and the other end is in close contact with the inner surface of the bent portion 151a and coupled to the post part 150, thereby providing one end of the printed circuit board 140. It may be supported in close contact with the other surface of the stem (110). Therefore, when the data signal transmission lines 141 extend to one end of the printed circuit board 140, the data signal lead pins 130 and the data signal transmission lines 141 may be connected without an air gap. As a result, an impedance discontinuity point in a high frequency band does not occur at the connection portion between the data signal lead pin 130 and the data signal transmission line 141, thereby preventing signal distortion.

When the reinforcement part 145 is formed to have a predetermined thickness, the post part 150 may have a flat surface in close contact with the reinforcement part 145 to stably support the printed circuit board 140. Although the post part 150 is illustrated in a shape in which a bent portion 151a is formed at the protruding end in the shape of a hexahedron, the post part 150 may also be formed in a shape in which the bent portion 151a is formed at the protruding end in the shape of a semicircle. When the post portion 150 is a semi-circular pillar shape, the flat surface of the semi-circular pillar is positioned to be in close contact with the reinforcement portion 145. In addition, the post part 150 may be located at various positions depending on the thickness of the printed circuit board 140 used and the input / output positions of the optical device / electronic device. For example, as will be described later, the post unit 150 may be positioned on the top surface of the dielectric 112 filled in the stem 110 to surround each circumference of the data signal lead pins 130.

The stem 110 may be made of a metal thio (TO) stem. In addition, the post part 150 may be formed of the same material as the stem 110. That is, the stem 110 and the post portion 150 may be made of a structure integrated with the same material. Therefore, the supporting effect of the printed circuit board 140 by the post unit 150 may be increased.

The ground portion 143 may be formed on the other surface of the printed circuit board 140, that is, the surface facing the post portion 150. In this case, the bent portion 151a may be bonded to the ground portion 143 by the soldering portion 181 formed by a soldering process. Accordingly, the printed circuit board 140 may be physically supported more firmly in contact with the other surface of the stem 110. In addition, when the post part 150 and the bent part 151a are made of a conductive metal material, the post part 150 may be electrically grounded.

The printed circuit board 140 may have ground pads 144 disposed on both sides thereof with the data signal transmission lines 141 interposed therebetween. The ground pad 144 is connected to the ground portion 143 through vias 144a. The ground pad 144 may reduce signal distortion at the outside of the data signal transmission line 141. The ground pad 144 is bonded to the other surface of the stem 110 by the soldering portion 182. Accordingly, the ground portion 143 of the printed circuit board 140 is connected to the ground of the stem 110, thereby reducing the inductance component on the carrier current path during signal transmission. In addition, the printed circuit board 140 may be connected more firmly in close contact with the other surface of the stem 110.

As such, when the printed circuit board 140 is closely attached to the stem 110 and joined by the soldering process, in the case of a flexible printed circuit board having a thickness of about 100 μm and having a very thin thickness, the flexible printed circuit board may have high flexibility ( Due to the high flexibility, it may be difficult to combine with the stem 110 as it is bent by the high temperature during the soldering process. At this time, the reinforcing part 145 is in contact with the other surface of the stem 110 and the other end is in close contact with the inner surface of the bent portion (151a) in the state seated on the post portion 150, the flexible printed circuit board without bending To be coupled in close contact with the stem 110. The reinforcement part 145 may be formed by coating the printed circuit board 140 with a polymer material or an electrically insulated material in order to increase the aforementioned effect.

The optical module 100 may include driving signal lead pins 160. The driving signal lead pins 160 protrude through the stem 110 and protrude toward the other surface of the stem 110, that is, the surface opposite to the mounting surface of the stem 110. The driving signal lead pins 160 may protrude in a direction perpendicular to the other surface of the stem 110. The driving signal lead pins 160 are connected to the optical device 120 or the electronic device 121. Here, the driving signal lead pins 160 may be connected to the optical device 120 or the electronic device 121 by wire bonding or the like. The driving signal lead pins 160 may transmit the supplied power or monitoring / control signal to the optical device 120 or the electronic device 121. The driving signal lead pins 160 may be disposed farther from the post portion 150 than the data signal lead pins 130.

In addition, the driving signal transmission lines 142 for connection with the driving signal lead pins 160 are formed on the printed circuit board 140. In this case, the data signal transmission lines 141 may be arranged along the center of the printed circuit board 140, and the driving signal transmission lines 142 may be arranged along both edges of the printed circuit board 140.

The printed circuit board 140 may include a substrate extension 146. The substrate extension 146 is formed to be bent to extend to be in close contact with the other surface of the stem 110 toward the driving signal lead pins 160 from the end facing the stem 110 in the printed circuit board 140. The driving signal transmission lines 142 extend to the substrate extension 146 and are connected to the driving signal lead pins 160. In this case, the driving signal lead pins 160 penetrate the substrate extension part 146 and are respectively bonded to the driving signal transmission lines 142 by the soldering part 183. Accordingly, the substrate extension 146 may be firmly supported while being in close contact with the other surface of the stem 110.

The substrate extension 146 may be absent depending on the internal configuration of the optical module 100. The printed circuit board 140 may be made of a flexible printed circuit board, but is not limited thereto. In some cases, the printed circuit board 140 may be made of a rigid printed circuit board. In addition, the shape of the printed circuit board 140 may have various shapes according to the configuration and position of the driving signal lead pin 160.

Meanwhile, referring back to FIG. 5, an alignment ground lead pin 170 may be protruded from the other surface of the stem 110 to apply power to an external optical alignment device. Aligning ground lead pins 170 may be placed in various positions on the stem 110 as the case may be. The alignment ground lead pin 170 may be cut and removed if unnecessary after use.

As shown in FIG. 7, through holes 111 through which data signal lead pins 130 penetrate are formed in the stem 110, and respective circumferences of the data signal lead pins 130 are formed in the through holes 111. Dielectric 112 may be filled to surround the. Here, the data signal lead pins 130 may protrude from one surface of the stem 110 in accordance with the manufacturing situation, but should be manufactured so that the derived length is minimized. When the data signal lead pins 130 protrude from the dielectric 112, an impedance discontinuity occurs in a high frequency band, thereby causing distortion of the signal. In addition, through-holes 111 through which driving signal lead pins 160 penetrate are formed in the stem 110, and dielectrics 112 are formed in the through-holes 111 to surround respective circumferences of the driving signal lead pins 160. ) Can be charged.

The optical module 100 of the above-described configuration has excellent electrical characteristics compared to the prior art. This can be confirmed through the graph shown in FIG. 8. Here, the graph shows the results calculated using the HFSS simulation tool of ANSYS. As shown in FIG. 8, the transmission loss (S21) is -0.6 dB and the reflection value (S11, reflection) is -21 dB up to 40 dB. Therefore, when compared with the graph of Figure 2, it can be seen that the structure is advantageous for use in the high frequency band.

9 is a side view of an optical module according to a second exemplary embodiment of the present invention, and FIG. 11 is an exploded perspective view of FIG. 10. Here, the same reference numerals as in the above-described drawings are the same components having the same function, and thus detailed description thereof will be omitted.

10 and 11, when the optical module 200 according to the second embodiment of the present invention is compared with the optical module 100 according to the first embodiment, the printed circuit board 240 has a post portion 250. There is a difference in the structure of the That is, the coupling part 251 of the post part 250 includes a protruding pin 251a protruding to penetrate the reinforcing part 245 and the printed circuit board 240 adjacent to the other end of the reinforcing part 245.

The protruding pin 251a may be positioned adjacent to the protruding end of the post part 150 and may have a cylindrical shape having a predetermined height and diameter. Protruding pins 251a may be provided in two or more so as to be more firmly coupled with the reinforcement part 245. In this case, the protruding pins 251a may be spaced apart along the width direction of the post part 250.

The protruding pins 251a may be formed to penetrate the ground pad 144 to connect the ground portion 143 to the ground pad 144. In addition, the protruding pin 251a may be bonded to the ground pad 144 by the soldering portion 281. At this time, the soldering portion 281 to the protruding pin 251a is extended to bond the ground pad 144 to the other surface of the stem 110, so that both the protruding pin 251a, the ground pad 144, and the stem 110 are formed. Can be bonded together. Accordingly, when the printed circuit board 240 is a flexible printed circuit board having a thickness of about 100 μm, when the flexible printed circuit board is closely fixed to the stem 110, the flexible printed circuit board may be physically supported. Can be. In addition, when the post part 250 and the protruding pin 251a are made of a conductive metal material, the post part 250 may be electrically grounded.

By the above-described configuration, as in the above-described first embodiment, the data signal lead pins 130 are placed on a straight line on the data signal transmission lines 141 of the printed circuit board 140 to be stably connected. Can be. It can be seen that the calculation results of the transmission loss and the reflection value for the optical module 200 according to the second embodiment of the present invention are similar to the results for the optical module 100 according to the first embodiment of the present invention. .

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation and that those skilled in the art will recognize that various modifications and equivalent arrangements may be made therein. It will be possible. Accordingly, the true scope of protection of the present invention should be determined only by the appended claims.

110.Stem 120.Optical element
130. Data signal lead pins 140, 240 Printed circuit board
141. Data signal transmission line 142. Drive signal transmission line
150,250..Post 151a..Bent
160..Drive signal lead pin 151a..Protrusion pin

Claims

Stem;
An optical element mounted on one surface of the stem;
Data signal lead pins connected to the optical device and protruding from the stem to the other surface of the stem;
A printed circuit board having data signal transmission lines for connecting to the data signal lead pins on one surface thereof and having a reinforcing portion protruding in a portion of the other surface; And
Protruded from the other surface of the stem, the data signal lead pins are in close contact with the reinforcement portion so as to be connected in a straight line on the data signal transmission lines to support the printed circuit board, and coupled with the reinforcement portion A post portion having a coupling portion to be formed;
Optical module comprising a.

The method of claim 1,
The reinforcing portion extends to one end of the printed circuit board such that one end is in close contact with the other surface of the stem;
And the coupling part includes a bent part which is bent to contact the other surface of the printed circuit board while being in close contact with the other end of the reinforcing part from the protruding end of the post part.

The method of claim 2,
The stem is a metal thio (TO) stem;
And the post part is formed of the same material as the thio stem.

The method of claim 3,
A ground portion is formed on the other surface of the printed circuit board;
The bending part is bonded to the ground part by soldering.

The method according to claim 3 or 4,
A ground pad is formed on one surface of the printed circuit board to be connected to the ground portion through vias on both sides of the data signal transmission line;
And the ground pad is bonded to the other surface of the stem by soldering.

The method of claim 1,
One end of the reinforcement part extends to one end of the printed circuit board;
And the coupling part includes a protruding pin protruding to penetrate the reinforcement part and the printed circuit board adjacent to the other end of the reinforcement part.

The method of claim 6,
The stem is a metal thio (TO) stem;
And the post part is formed of the same material as the thio stem.

The method of claim 7, wherein
A ground portion is formed on the other side of the printed circuit board, and ground pads are formed on both sides of the printed circuit board with the data signal transmission lines interposed therebetween;
The protruding pin is formed to penetrate the ground pad to connect the ground portion with the ground pad;
And the ground pad is bonded to the other surface of the stem by soldering and bonded to the protruding pin.

The method of claim 1,
Drive signal lead pins connected to the optical device and protruding from the stem to the other surface of the stem;
The printed circuit board includes a substrate extension that is bent to extend to be in close contact with the other surface of the stem from the end facing the other surface of the stem toward the driving signal lead pins, and along both edges of the data signal transmission lines. And a driving signal transmission line connected to the driving signal lead pins to extend to the substrate extension part.

10. The method of claim 9,
And the driving signal lead pins are bonded to the driving signal transmission lines by soldering through the substrate extension.

The method of claim 1,
The other surface of the stem is an optical module, characterized in that the ground lead pin for alignment for applying power to the external optical alignment equipment protruding.

The method of claim 1,
Through holes are formed in the stem through the data signal lead pins;
And a dielectric is filled in the through holes to surround respective circumferences of the data signal lead pins.

The method of claim 12,
The data signal lead pins are formed so as not to protrude from the dielectric on one surface of the stem.

The method of claim 1,
The printed circuit board is an optical module, characterized in that the flexible (rigid) printed circuit board or a rigid (rigid) printed circuit board.