JP2001257415A - Optical semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve high frequency transfer characteristic of an optical semiconductor device. SOLUTION: In a field through part 28 which is engaged and bonded to an aperture part 29 of a metal vessel 21 of an optical semiconductor device, an I/O board 32 and a U-shaped surrounding wall 33 are collectively formed of ceramic like alumina. The surrounding wall 33 is formed in a U-shape so as to surround the outer periphery of a part in the I/O board 32 which part protrudes outside the metal vessel 21. An internal electrode 34 for connection with an optical semiconductor element 22 is formed on an upper surface of a part in the I/O board 32 which part is exposed in the metal vessel 21. An external electrode 37 for connection with a mother board 36 is formed on a lower surface of a part in the I/O board 32 which part protrudes outside the metal vessel 21. The external electrode 37 and the internal electrode 34 are connected with a viahole conductor 38 penetrating the I/O board 32. The external electrode 37 is connected with a connection electrode 40 of the mother board 36 via a bump 39.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical semiconductor device used for optical communication and the like, and more particularly to an optical semiconductor device having an improved connection structure with an external circuit board.

[0002]

2. Description of the Related Art An example of a conventional optical semiconductor device is shown in FIGS.
It will be described based on. The metal container 1 of the optical semiconductor device has a metal bottom plate 3 made of a highly heat-dissipating metal such as CuW in order to efficiently radiate heat generated by the optical semiconductor element 2 such as a laser diode or a photodiode housed therein. Metal container body 4, upper metal frame 5, and metal cap 6
Are joined. The optical semiconductor element 2 is mounted on the upper surface of the circuit board 7 housed in the metal container 1, and the Peltier element 8 is mounted on the lower surface of the circuit board 7, and the optical semiconductor element 2 is cooled (heat-absorbed) by the Peltier element 8. Is cooled within the stable operating temperature range. Then, the heat dissipation surface of the Peltier element 8 is joined to the metal bottom plate 3 to enhance heat dissipation, and the circuit board 7 is fixed on the metal bottom plate 3 by the Peltier element 8. An optical fiber introduction hole 9 for introducing an optical fiber (not shown) is formed in the front part of the metal container body 4, and the height of the center of the optical fiber introduction hole 9 is set at the center of the optical semiconductor element 2. Height position.

[0005] A convex field through portion 11 made of an insulator such as ceramic is fitted into and joined to openings 10 (see FIG. 8) formed on both side surfaces of the metal container body 4. . An internal electrode 12 (see FIG. 9) for connecting to the optical semiconductor element 2 is formed on an upper surface of a portion of the field through portion 11 exposed in the metal container 1. An external electrode 13 (see FIG. 9) is provided on the upper surface of the portion protruding outside the container 1.
Are formed on the external electrodes 13 and external circuit boards 16.
The lead 14 for connecting to the (mother board) is joined. As shown in FIG. 9, the internal electrode 12 and the external electrode 13 of the field through portion 11 are connected by an intermediate wiring pattern 15.

The reason why the field through portion 11 is formed in a convex shape is that the intermediate wiring pattern 15 connecting the internal electrode 12 and the external electrode 13 does not come into contact with the upper metal frame 5. This is for covering with the upper insulating layer 11a. The upper surface of the upper insulating layer 11a of the field through portion 11 is also used for height adjustment by polishing.

[0005] A metallized layer (not shown) for hermetic sealing is formed in a portion of the field through portion 11 which joins with the metal container 1, and this metallized layer extends around the intermediate wiring pattern 15. It is in a surrounding state. Since the potential of this metallization layer is a normal ground potential, the internal electrode 12 and the external electrode 13 exposed on the upper surface of the field through portion 11 become microstrip lines, and the intermediate wiring pattern 15 covered with the upper insulating layer 11a is formed.
Becomes a strip line. The line width of the intermediate wiring pattern 15 covered with the upper insulating layer 11a is smaller than the line width of the electrodes 12 and 13 connected to both ends thereof, for the purpose of achieving impedance matching.

[0006]

However, in the above-described conventional configuration, the lead 14 as an external terminal is a major cause of deteriorating high-frequency transmission characteristics. That is, the lead 14 is connected to the wirings 12, 13, 1 of the field through portion 11.
Since the transmission line structure is different from that of No. 5, the characteristic impedance changes and the high-frequency transmission characteristics deteriorate. If the length of the lead 14 can be reduced, the effect is reduced, but the lead 14 bridges the external electrode 13 on the upper surface of the field through portion 11 and the electrode on the upper surface of the external circuit board 16. For this reason, the entire length of the lead 14 must be increased. That is, in order to secure the bonding strength of the bonding portions on both sides of the lead 14 with respect to the field through portion 11 and the external circuit board 16, the bonding length of both sides of the lead 14 is required to be at least about 1 mm, respectively. ,
The gap between the field-through portion 11 and the external circuit board 16 also needs to be at least about 0.5 mm in consideration of dimensional variations at the time of manufacturing. Therefore, the length of the lead 14 is at least about 2.5 mm. Is required and lead 14
The total length becomes longer. For this reason, the mismatch of the characteristic impedance due to the lead 14 cannot be ignored, and the lead 14 causes deterioration of the high-frequency transmission characteristics.

As shown in FIG. 9, in the conventional field through portion 11, the line width of the intermediate wiring pattern 15 covered with the upper insulating layer 11a is made smaller than the line width of both electrodes 12, 13. In this case, the transmission line structure is partially changed, and it is impossible to completely match the characteristic impedance. This mismatch in characteristic impedance also causes deterioration of high-frequency transmission characteristics, as in the case of the lead 14.

[0008] This mismatch of characteristic impedance is not a problem if the length of the intermediate wiring pattern 15 (strip line) having a small line width is negligibly short with respect to the wavelength of the operating frequency. Is determined by the thickness of the upper insulating layer 11a.
The thickness of the intermediate wiring pattern 15 is required to be at least about 1 mm because the thickness of the intermediate wiring pattern 15 is required to be at least about 1 mm because it is necessary to secure the bonding strength to the metal container 1. For this reason, in the high frequency range of 10 GHz or more, the mismatch of the characteristic impedance due to the intermediate wiring pattern 15 (strip line) cannot be ignored, and this strip line structure also causes the deterioration of the high-frequency transfer characteristic, like the lead 14. .

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and an object thereof is to provide an optical semiconductor device capable of improving high-frequency transmission characteristics.

[0010]

According to a first aspect of the present invention, there is provided an optical semiconductor device having at least an optical semiconductor element housed in a metal container and formed on a side surface of the metal container. A portion of the input / output board exposed in the metal container in a structure in which an input / output board formed with wiring for connecting the optical semiconductor element and an external circuit board is fitted into the opened opening. An internal electrode for connecting to the optical semiconductor element is formed on an upper surface of the optical semiconductor element, and a lower surface of a portion of the input / output substrate protruding outside the metal container is connected to the external circuit board. An external electrode is formed, and the external electrode and the internal electrode are connected by a via-hole conductor formed on the input / output substrate.

According to this configuration, the external electrodes on the lower surface of the input / output board can be connected to the connection electrodes on the upper surface of the external circuit board by the surface mounting method, thereby eliminating the need for leads. Thereby, the connection length between the electrodes is set to 0.1 to 0.2.
mm, and the characteristic impedance mismatch (deterioration of high-frequency transfer characteristics) due to the connection between the electrodes can be almost ignored.

In this configuration, since the internal electrodes for connecting to the optical semiconductor element are formed on the upper surface of the input / output substrate,
In order to connect the internal electrode on the upper surface of the substrate and the external electrode on the lower surface of the substrate, it is necessary to use a via-hole conductor penetrating the input / output substrate, and this via-hole conductor becomes a discontinuous portion (strip line portion) of the transmission line. By reducing the thickness of the input / output substrate through which the via-hole conductor penetrates, the length of the discontinuous portion (via-hole conductor) of the transmission line can be reduced. In general, the thickness of the input / output substrate can be set to 0.5 mm or less even when the strength is considered, and the length of the strip line portion of the conventional convex field through portion (about 1 m
m), which can be reduced to half or less of that of m), and mismatching of characteristic impedance (deterioration of high-frequency transmission characteristics) due to discontinuous portions (via-hole conductors) of the transmission line can be sufficiently reduced.

In this case, an enclosing wall portion made of an insulator is formed on the upper surface side of a portion of the input / output substrate protruding outside the metal container so as to surround the outer periphery thereof. It is preferable to form a via-hole conductor inside the portion. With this configuration, the internal electrodes on the upper surface of the input / output substrate do not need to be covered with the surrounding wall portion, and the transmission line on the upper surface of the input / output substrate does not need to have the stripline structure.

Further, it is preferable that the height of the surrounding wall is set within a range of 2 mm to 8 mm. With this configuration, the height positional relationship between the internal electrode (optical semiconductor element) on the upper surface of the input / output substrate and the optical fiber introduction hole of the metal container can be appropriately maintained.

According to a fourth aspect of the present invention, a bump is formed on the lower surface of the external electrode on the lower surface of the input / output substrate, and the external electrode is connected to the connection electrode formed on the upper surface of the external circuit board by the bump. It is good to In this case, the operation of mounting the optical semiconductor device on an external circuit board becomes easy, and the mounting efficiency can be improved.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIG.
4 through FIG. The metal container 21 of the optical semiconductor device has a metal bottom plate 23 made of a highly heat-dissipating metal such as CuW in order to efficiently radiate heat generated by the optical semiconductor element 22 such as a laser diode or a photodiode housed therein. The metal container body 24, the upper metal frame 25, and the metal cap 26 are joined together. The metal container main body 24 has the same shape as the conventional metal container main body 4 shown in FIG.
An optical fiber introduction hole 27 for introducing an optical fiber (not shown) is formed, and the height position of the center of the optical fiber introduction hole 27 matches the height position of the center of the optical semiconductor element 22. Openings 29 for attaching a U-shaped field through portion 28 to be described later are formed on both side surfaces of the metal container main body 24.

Although the shape of the upper metal frame 25 is more complicated than that of the conventional upper metal frame 5 shown in FIG. 8, since the thickness thereof is thin, the same process as the conventional one can be easily performed by mechanical punching. It can be formed without increasing the cost.

The optical semiconductor element 22 is mounted on the upper surface of the circuit board 30 accommodated in the metal container 21 with bonding wires 41 and the like, and the Peltier element 31 is mounted on the lower surface of the circuit board 30. The optical semiconductor element 22 is cooled to a stable operating temperature range by the heat absorption. And this Peltier element 31
The heat dissipation surface is joined to the metal bottom plate 23 to enhance heat dissipation, and the circuit board 30 is fixed on the metal bottom plate 23 by the Peltier element 31.

Next, the structure of the field through portion 28 which is fitted into and joined to the opening 29 of the metal container 21 will be described. The field through portion 28 is formed by integrally forming an input / output substrate 32 and a U-shaped surrounding wall portion 33 with ceramics such as alumina, and the surrounding wall portion 33 is provided outside the metal container 21 of the input / output substrate 32. It is formed in a U-shape so as to surround the outer periphery of the protruding portion. The height of the surrounding wall portion 33 is set in the range of 2 mm to 8 mm, whereby the gap between the internal electrode 34 (optical semiconductor element 22) on the upper surface of the input / output substrate 32 and the optical fiber introduction hole 27 of the metal container 21 is formed. The height positional relationship is maintained properly. Then, by polishing the upper end surface of the surrounding wall portion 33, the height of the field through portion 28 is adjusted, and the height position of the upper end surface of the surrounding wall portion 33 is adjusted to the height position of the upper end surface of the metal container body 24. And the upper metal frame 25 is joined to the upper end surfaces of both. Metal container 21 in field through portion 28
A metallized layer (not shown) for hermetic sealing is formed by printing or the like at a portion to be joined.

As shown in FIGS. 1 and 4, the input / output board 3
On the upper surface of the portion of the second portion exposed in the metal container 21,
An internal electrode 34 for connecting to the optical semiconductor element 22 is formed by printing or the like, and the internal electrode 34 and a wiring pattern (not shown) on the upper surface of the circuit board 30 are bonded to a bonding wire 35.
Connected by External electrodes 37 for connecting to a motherboard 36 (an external circuit board) are provided on the lower surface of a portion of the input / output board 32 protruding outside the metal container 21.
Are formed by printing or the like, and the external electrodes 37 and the internal electrodes 34 are formed.
Are connected by a via-hole conductor 38 formed through the input / output board 32. A bump 39 is formed on the lower surface of the external electrode 37, and the external electrode 37 is connected to the connection electrode 40 formed on the upper surface of the mother substrate 36 and the bump 3.
9.

According to the embodiment described above, the metal container 2 of the input / output board 32 of the field through portion 28
An external electrode 37 is formed on the lower surface of a portion protruding to the outside of the device 1, and the external electrode 37 and the internal electrode 34 on the upper surface of the input / output substrate 32 are connected by a via hole conductor 38 penetrating the input / output substrate 32. I / O board 32
The external electrodes 37 on the lower surface are connected to the connection electrodes 4 on the upper surface of the motherboard 36.
It can be connected to the bumps 39 so as to face 0, and leads are not required. As a result, the connection length between the electrodes 37 and 40 can be greatly reduced from the conventional 2.5 mm to about 0.1 to 0.2 mm, and the characteristics of the connection portion (bump 39) between the electrodes 37 and 40 can be reduced. Impedance mismatch (deterioration of high-frequency transfer characteristics) can be almost ignored.

In this configuration, since the internal electrode 34 for connecting to the optical semiconductor element 22 is formed on the upper surface of the input / output substrate 32, the internal electrode 34 on the upper surface of the substrate and the external electrode 37 on the lower surface of the substrate are connected. It is necessary to use a via-hole conductor 38 penetrating the input / output substrate 32, and this via-hole conductor 38 becomes a discontinuous portion (strip line portion) of the transmission line. By reducing the thickness, the length of the discontinuous portion of the transmission line (via hole conductor 38) can be reduced. In general, the thickness of the input / output substrate 32 can be set to 0.5 mm or less even in consideration of the strength, and the length of the strip line portion of the conventional convex field through portion 11 (about 1
mm), and the characteristic impedance mismatch (deterioration of high-frequency transfer characteristics) due to the discontinuous portion (via hole conductor 38) of the transmission line can be sufficiently reduced.

Further, a U-shaped surrounding wall portion 33 is formed on the upper surface side of a portion of the input / output board 32 protruding outside the metal container 21 so as to surround the outer periphery thereof.
3, the internal electrode 34 on the upper surface of the input / output substrate 32 is
3, so that the transmission line on the upper surface of the input / output substrate 32 does not need to have the stripline structure.

As described above, in the optical semiconductor device of the present embodiment, the lead and the long strip line portion, which have caused the conventional characteristic impedance mismatch, are eliminated.
Even in a high frequency range of 0 GHz or more, the problem of characteristic impedance mismatch can be solved, and high-frequency transfer characteristics can be greatly improved. In addition, by eliminating the leads, it is possible to satisfy the demands for downsizing the optical semiconductor device and improving the mounting density.

The conventional field through portion 11 shown in FIG. 9 has a structure in which the intermediate wiring pattern 15 connecting the internal electrode 12 and the external electrode 13 is covered with the upper insulating layer 11a. It was necessary to manufacture the part 11 by a green sheet laminating method. That is,
At the time of manufacturing the field through portion 11, a wiring pattern is printed on the surface of the ceramic green sheet with a conductive paste, the ceramic green sheet is punched into a predetermined shape, a plurality of these ceramic green sheets are laminated, and these are simultaneously fired. The field through portion 11 is manufactured. However, in this green sheet laminating method, since the field through portion 11 contracts considerably during firing, it is difficult to accurately match the size of the field through portion 11 with the size of the opening 10 of the metal container 1. For this reason, in order to secure the dimensional accuracy of the field through portion 11, it is necessary to polish the field through portion 11 after sintering to adjust the dimensions, and there is a disadvantage that the manufacturing efficiency is reduced and the cost is increased.

On the other hand, in the present embodiment, since the wiring pattern (electrodes 34 and 37) of the field through portion 28 is not covered with the surrounding wall portion 33, the field through portion 28 can be formed by an integral molding method. That is, at the time of manufacturing the field-through portion 28, the shape of the field-through portion 28 is integrally formed of a ceramic material, and then the via-hole conductor 38, the internal electrode 34, and the external electrode 37 are printed with a conductive paste, and these are simultaneously fired. The field through portion 28 is manufactured. This integrated molding method requires less or less firing shrinkage than the green sheet laminating method, and requires less or less polishing steps for dimensional adjustment, thereby improving manufacturing efficiency and reducing manufacturing costs. can do.

However, in the present invention, the field through section 28
May be manufactured by a green sheet laminating method, and even in this case, the intended object of the present invention can be sufficiently achieved. In the present embodiment, the external electrodes 37 of the input / output board 32 and the connection electrodes 40 of the mother board 36 are connected by the bumps 39. However, instead of the bumps 39, other surface mounting methods such as reflow soldering are used. The connection may be made by using.

Next, another embodiment of the field through section 43 will be described with reference to FIG. In FIG. 5, only the input / output board 44 is shown without illustration of the surrounding wall.
On the upper surface of the input / output substrate 44, an internal electrode 45 and a ground electrode 46 surrounding the internal electrode 45 are formed by printing or the like. Although not shown, an external electrode and a ground electrode surrounding the external electrode are formed on the lower surface of the input / output substrate 44 by printing or the like. The internal electrodes 45 on both sides of the input / output board 44 and the external electrodes are connected by via-hole conductors 47 penetrating the input / output board 44. Similarly, the ground electrodes 46 on both sides of the input / output board 44 It is connected by a plurality of via-hole conductors 48 penetrating through 44. In this case, the surrounding wall portion (not shown) may be formed on the outer periphery of the ground electrode 46, or may be formed by being laminated on the ground electrode 46. In the former case, it can be manufactured by an integral molding method, but in the latter case, it is necessary to form it by a green sheet laminating method.

As shown in FIG. 5, the outer periphery of the internal electrode 45 and the external electrode is surrounded by a ground electrode 46, and the input / output substrate 44
A plurality of via-hole conductors 4 between the ground electrodes 46 on both sides of the
The connection at 8 strengthens the ground, facilitates impedance control, and can further improve high-frequency transfer characteristics.

[0030]

As is apparent from the above description, according to the first aspect of the present invention, the inner surface for connecting to the optical semiconductor element is provided on the upper surface of the portion of the input / output substrate exposed in the metal container. An electrode is formed, and an external electrode for connecting to an external circuit board is formed on a lower surface of a portion of the input / output substrate that protrudes to the outside of the metal container, and the external electrode and the internal electrode are connected to via holes. Since the connection is made by conductors, no lead is required, the connection length between the electrodes can be significantly reduced, and the problem of characteristic impedance mismatch due to the connection between the electrodes can be eliminated. Characteristics can be improved.

According to a second aspect of the present invention, a surrounding wall portion is formed on the upper surface side of a portion of the input / output substrate protruding outside the metal container so as to surround the outer periphery thereof, and a via hole conductor is formed inside the surrounding wall portion. Is formed, the transmission line on the upper surface of the input / output substrate does not need to have a stripline structure, and the high-frequency transmission characteristics do not need to be reduced.

According to the third aspect of the present invention, the height of the surrounding wall is set in the range of 2 mm to 8 mm, so that the internal electrode (optical semiconductor element) on the upper surface of the input / output substrate and the optical fiber introduction hole of the metal container can be provided. Height positional relationship can be properly maintained.

According to a fourth aspect of the present invention, a bump is formed on the lower surface of the external electrode on the lower surface of the input / output substrate, and the external electrode is connected to a connection electrode of an external circuit board by the bump. As a result, the optical semiconductor device can be efficiently mounted on an external circuit board, and the mounting cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional front view of an optical semiconductor device showing an embodiment of the present invention.

FIG. 2 is a front view of the optical semiconductor device according to the embodiment;

FIG. 3 is an exploded perspective view of the metal container according to the embodiment;

FIG. 4 is an enlarged perspective view showing a part of the field through portion of the embodiment in a cutaway manner.

FIG. 5 is an enlarged perspective view showing only an input / output board portion of a field through portion of another embodiment.

FIG. 6 is a longitudinal sectional front view of a conventional optical semiconductor device.

FIG. 7 is a front view of a conventional optical semiconductor device.

FIG. 8 is an exploded perspective view of a conventional metal container.

FIG. 9 is an enlarged perspective view of a conventional field through portion.

[Explanation of symbols]

Reference Signs List 21 metal container, 22 optical semiconductor element, 23 metal bottom plate, 24 metal container body, 25 upper metal frame, 26 metal cap, 27 optical fiber introduction hole, 28 field through part, 29 opening Reference numeral 30, a circuit board, 31 a Peltier element, 32 an input / output board, 33 an enclosure, 34
Internal electrode, 36 ... mother board (external circuit board), 37
... external electrodes, 38 ... via-hole conductors, 39 ... bumps, 4
0 ... connection electrode, 43 ... field through part, 44 ... input / output board, 46 ... ground electrode, 47, 48 ... via hole conductor.

Claims (4)

[Claims] At least an optical semiconductor element is accommodated in a metal container, and wiring for connecting the optical semiconductor element to an external circuit board is formed in an opening formed in a side surface of the metal container. An optical semiconductor device having the input / output substrate fitted therein, wherein an internal electrode for connecting to the optical semiconductor element is formed on an upper surface of a portion of the input / output substrate exposed in the metal container, and An external electrode for connecting to the external circuit board was formed on the lower surface of a portion of the output board that protruded outside the metal container, and the external electrode and the internal electrode were formed on the input / output board. An optical semiconductor device characterized by being connected by a via-hole conductor. 2. A surrounding wall portion made of an insulator is formed on an upper surface side of a portion of the input / output substrate protruding outside of the metal container so as to surround an outer periphery thereof, and the via-hole conductor is formed of the surrounding wall. The optical semiconductor device according to claim 1, wherein the optical semiconductor device is formed inside the portion. 3. The height of the surrounding wall is from 2 mm to 8 mm.
3. The optical semiconductor device according to claim 2, wherein the distance is within the range of mm. 4. A bump is formed on a lower surface of the external electrode, and the external electrode is connected to a connection electrode formed on an upper surface of the external circuit board by the bump. 4. The optical semiconductor device according to any one of 3.