JP2003101115A - Package for optical semiconductor module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a package realizing an optical semiconductor module in which the size and power consumption can be reduced by reducing inflow of heat from the outside of the package as much as possible. SOLUTION: A package 10 for an optical semiconductor module comprises a frame 11 and a cover 14 formed of a material having a low thermal conductivity and a low thermal expansion coefficient, and a heat sink 13 formed of a material having a high thermal conductivity and a low thermal expansion coefficient. Since the frame 11 and the cover 14 are formed of a material having a low thermal conductivity, heat on the outside of the package 10 can be prevented from flowing through the frame 11 and the cover 14 even if the inside of the package 10 is cooled down below the room temperature. Furthermore, since the heat sink 13 is formed of a material having a high thermal conductivity, heat generated in the package 10 can be discharged efficiently to the outside. Consequently, the size and power consumption of the optical semiconductor module can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a package for accommodating an optical semiconductor module which is a coupler between a high-power optical semiconductor element (for example, a semiconductor laser) used in an optical communication device and an optical fiber.

[0002]

2. Description of the Related Art In recent years, with the rapid development of the Internet, the need for high-speed transmission of a large amount of data (information) has been increasing. Therefore, if data (information) is transmitted using an optical fiber network that has already been installed, high-speed transmission of data (information) will be possible. Therefore, in the last few years, the use of optical fiber networks will increase rapidly. Became. In this case, so-called WDM, which multiplexes channels by passing lights of different wavelengths into one optical fiber
(Wavelength Division Multiplexing)
Or DWDM (Dense Wavelength Division Multip
Lexing: high-density wavelength division multiplexing) and other wideband optical network technologies enable high-speed bidirectional transmission of large amounts of data. In WDM, a transmission technology of 10 Gigabits / second in total is being developed by multiplexing four channels having a transmission rate of 2.5 Gigabits / second per wavelength. On the other hand, in DWDM, it becomes possible to transmit data of gigabit to terabit in an extremely large capacity.

Here, the data (information) transferred through the optical fiber is a signal obtained by modulating laser light, and this signal is transmitted from an electronic device containing a semiconductor laser or the like called an optical semiconductor module. The optical semiconductor module is also used in a so-called optical amplifier that amplifies signal strength at an intermediate point where data (information) is transmitted using an optical fiber. By the way, since the oscillation wavelength of the semiconductor laser is greatly affected by the temperature, it is essential to strictly control the temperature when the semiconductor laser operates. An electronic device called an electronic cooler or a Peltier device is usually used for this temperature control. A container that houses electronic components such as a semiconductor laser and a Peltier device is generally called a package. For example, FIG. 7 shows components used in this type of package, and FIG. 8 shows a package 50 formed by assembling these components.

The main components forming the package 50 are a frame 51, a window holder 52, a heat sink 53 as a bottom plate, and a cover 54. Then, the window holder 52 is brazed to the one side wall of the frame 51 with the silver wax 52a, and the heat sink 53 serving as a bottom plate is brazed to the lower surface of the frame 51 with the silver wax 51a to fix them. Further, the ceramic feedthroughs 55, 55 are brazed with silver wax 55a, 55a to the notches formed in the pair of side walls of the frame 51 to fix them. In addition, these ceramic feedthroughs 55,
A pair of leads 56, 56 on top of 55, silver wax 55b, 55
These are fixed by brazing with b. In addition, a seal ring 57 is provided on the leads 56, 56 with a silver wax 57.
These are fixed by brazing with a. Then, electronic components such as a semiconductor laser and a Peltier element are mounted on the frame 51.
After being accommodated and fixed inside, the cover 54 is finally fixed by electric welding to form the package 50, and the optical semiconductor module is also formed.

[0005]

In the optical semiconductor module formed as described above, the heat generated by the semiconductor laser is finally radiated (exhausted heat) from the heat sink 53 to the outside of the package 50. Then, in order to improve the cooling efficiency by the Peltier element, it is necessary to quickly exhaust the heat generated by the semiconductor laser to the outside of the package 50. Therefore, normally, the heat sink 53
Is formed of a copper-tungsten material having good thermal conductivity. On the other hand, the frame 51 is F called Kovar
eNiCo alloy is used, and its coefficient of thermal expansion is
Thermal conductivity of about 17 W / m at 4.5 to 5.5 ppm / K
・ K.

Recently, a technique of changing one semiconductor laser to several kinds of oscillation wavelengths by changing the control temperature of the semiconductor laser with a Peltier device, so-called tunable laser, has been developed. When such a technique is used, the use of one optical semiconductor module corresponding to different oscillation wavelengths is equivalent to the case of using a plurality of optical semiconductor modules corresponding to individual oscillation wavelengths. It is possible to reduce the number of pieces used. Further, it becomes possible to reduce the stock quantity of optical semiconductor modules for maintenance. To this end, there has been an increasing demand for reviewing the overall configuration of the package including the Peltier element and improving the package to have better cooling characteristics.

By the way, in the current optical network technology, for example, in WDM, the wavelength interval is 0.8.
It is multiplexed so as to be nm. When the temperature of the semiconductor laser changes by 1 ° C., the oscillation wavelength of the semiconductor laser changes by 0.1 nm. Therefore, if the oscillation temperature is changed by changing the control temperature of one semiconductor laser, 0.8 nm is required to support four wavelengths (four channels).
× 4 = 3.2 nm is required. When this is converted into a temperature change, 32 ° C. (3.2 (nm) /0.1 (nm /
℃)). The operating temperature of a semiconductor laser is usually 2
Since it is 5 ° C., considering this temperature as a reference, it is necessary to cool the semiconductor laser to −7 ° C.

However, when the temperature of the semiconductor laser is cooled to a temperature of several degrees Celsius or lower, the temperature inside the package becomes lower than the temperature outside the package (room temperature). In this case, if the thermal conductivity of the frame, the cover, etc. is about 17 W / m · K, as shown by the arrow in FIG. 8, the heat outside the package passes through the wall of the frame, the cover, etc. that constitutes the package. It comes to flow in. As a result, a situation arises in which heat including the heat flowing from the outside of the package through the wall surface (frame, cover, etc.) of the package must be exhausted (cooled) by the Peltier device together with the heat generated by the semiconductor laser. For this reason, Peltier elements are required to have higher performance and superior cooling characteristics than ever before.

However, in order to improve the cooling capacity of the Peltier device, there arises a problem that a large amount of power has to be supplied to the Peltier device. This causes a problem that it is not possible to meet the market demand for reducing the power input to the Peltier device to reduce the size and power consumption of this type of optical semiconductor module. For this reason, it is necessary to reduce the heat flowing from the outside of the package as much as possible. Therefore, the present invention has been made in order to solve the above problems, and provides an optical semiconductor module capable of downsizing and reducing power consumption by reducing heat flowing from the outside of the package as much as possible. It is intended to provide a package that can be used.

[0010]

In order to achieve the above object, in the package for an optical semiconductor module of the present invention, the frame and the cover are made of a material having a low thermal conductivity and a low coefficient of thermal expansion, and the heat sink has a high thermal conductivity and a low thermal conductivity. It is made of a material having a coefficient of expansion. Thus, if the frame and the cover are made of a material having a low thermal conductivity, even if the inside of the package is cooled to a temperature lower than room temperature, the heat outside the package can be prevented from flowing through the frame and the cover. Like Further, when the heat sink is made of a material having high thermal conductivity, the heat generated in the package can be efficiently released (exhausted heat) to the outside of the package. As a result, it becomes possible to reduce the size and power consumption of the optical semiconductor module using this package.

If the thermal expansion coefficients of the frame and the heat sink or between the frame and the cover are greatly different, thermal stress is applied to the joint interface after joining them, and in the worst case, there is a case where breakage occurs. Therefore, in the present invention, the frame and the cover are made of a material having a low thermal expansion coefficient, and the heat sink is also made of a material having a low thermal expansion coefficient. As a result, even if the frame and the heat sink or the frame and the cover are joined, it is possible to prevent thermal stress from being applied to the joint interface after joining, and the joint does not break.

In this case, if the thermal expansion coefficient of the frame and the cover is within the range of 2 ppm / K or more and 10 ppm / K or less, even if the frame and the heat sink or the frame and the cover are joined, the joining interface after joining is completed. It became clear that the addition of thermal stress to the can be prevented. In order to prevent heat from outside the package from flowing in through the frame and cover, it is sufficient to set the thermal conductivity of the frame and cover to 17 W / mK or less than the current situation, but the heat inflow is sufficient. In order to prevent the above, the thermal conductivity of the frame and the cover is desirably 10 W / m · K or less, preferably 5 W / m · K or less.
From these facts, a material having a low thermal conductivity and a low coefficient of thermal expansion has a thermal conductivity of 10 W / m · K or less, preferably 5 W.
/ M · K or less, thermal expansion coefficient of 2 ppm / K or more, 10p
It is preferable to use a material of pm / K or less.

As a material having both properties of low thermal conductivity and low coefficient of thermal expansion, it is desirable to use ceramics, and in particular, one selected from zirconium oxide, mullite, stearite, cordierite and fosterite.
It is preferable to use a ceramic containing three or more as a main component.
Further, if the frame and the cover are made of ceramic, it becomes difficult to bond and fix the frame and the cover. For this reason, it is desirable to dispose an iron-nickel-cobalt alloy or an iron-nickel alloy that has good bondability with the ceramic on the upper part of the frame. Alternatively, at least the peripheral portion of the cover is made of iron with good bondability with the ceramic.
You may make it arrange | position nickel-cobalt alloy or iron-nickel alloy.

A window made of a glass material, a ceramic material, or the like is provided on one side wall of the frame so that the laser light can be transmitted therethrough. Therefore, it is necessary to provide a window holder (window frame) for fixing the window on one side wall of the frame. Therefore, a window holder may be separately manufactured and bonded to the frame, but this is not preferable because a step of bonding the separately manufactured window holder is required.
Therefore, in the present invention, the window holder is formed integrally with the frame. This makes the manufacture of this type of package simple and easy. Further, the heat sink may be any material as long as it has a low coefficient of thermal expansion and high thermal conductivity, and examples of the material having a low coefficient of thermal expansion and high thermal conductivity include tungsten, copper-tungsten, copper-molybdenum, and aluminum nitride. It is desirable to select from materials selected from.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment of the present invention will be described with reference to FIGS. Note that FIG. 1 is an exploded perspective view showing components used in the package of the present embodiment, FIG. 2 is a perspective view showing a cover, and FIG.
FIG. 6 is a perspective view showing a package before a cover is attached to an assembly body formed by assembling these components.

1. Package for optical semiconductor module The components forming the package 10 of the present invention include a frame 11, a window holder 12, and a heat sink 1 serving as a bottom plate.
3 and the cover 14. The frame 11 and the window holder 12 are integrally formed by a method such as CIM (Ceramic Injection Molding). Then, the bottom surface of the frame 11 is fixed by brazing a heat sink 13 serving as a bottom plate. Further, ceramic feedthroughs 15 are fixed to the notches 11a formed in the pair of side walls of the frame 11 by brazing. In addition, these ceramic feedthroughs 1
A pair of leads 16 and 16 are fixed on the electrodes 5 and 15 by brazing. A seal ring 17 covering the frame 11 is fixed to the upper portion of the frame 11 by brazing. Then, after housing and fixing electronic components such as a semiconductor laser and a Peltier device in the frame 11,
Finally, the cover 14 is fixed by electric welding to form the package 10 and the optical semiconductor module.

The frame 11 is made of a ceramic material having both low thermal conductivity and low thermal expansion coefficient, and the thermal expansion coefficient is 2 ppm / K or more and 10 ppm / K.
The thermal conductivity is 10 W / mK or less, preferably 5 or less.
The one with W / m · K or less is used. Ceramic materials having both of these low thermal conductivity and low coefficient of thermal expansion include zirconium oxide (ZrO ₂ ) and mullite (3A).
l ₂ O ₃ -2SiO _2), steatite (SiO-Mg
O), cordierite (2MgO-2Al ₂ O ₃ ), and fosterite (2MgO—SiO ₂ ), as a main component. In addition, aluminum oxide (Al ₂ O ₃ ) or magnesium oxide (Mg
_It is also possible to add a general ceramic material such as ₂ O ₃ ) so that the coefficient of thermal expansion is approximate to that of other parts.
The thermal conductivity and the thermal expansion coefficient of these ceramic materials have the values shown in Table 1 below. In addition, in Table 1 below, the thermal conductivity shows a value in the temperature range of 25 ° C to 250 ° C.

[0018]

[Table 1]

The heat sink 13 serving as the bottom plate is made of a material having a low coefficient of thermal expansion and high thermal conductivity, and is made of tungsten (W) or copper-tungsten (Cu-).
W), copper-molybdenum (Cu-Mo), aluminum nitride (AlN) or the like is desirable. Further, as the cover 14, as shown in FIG. 2A, a plate-like rectangular main body portion 14a made of the above ceramic material,
A quadrangular ring member 14b made of Fe-Ni-Co alloy (commonly called Kovar) and having an opening is integrated by brazing. Alternatively, FIG. 2 (b)
As shown in FIG. 2, a plate-shaped body portion 14a made of the above ceramic material and an Fe—Ni—Co alloy (common name: Kovar)
Alternatively, a frame member 14c having a rectangular shape and having no opening may be integrated by brazing.

The ceramic feedthrough 15 is made of a ceramic material having a predetermined wiring. For example, it is formed by forming a green sheet made of aluminum oxide (Al ₂ O ₃ ) and a binder into a predetermined shape and sintering a green sheet provided with a predetermined wiring. When the ceramic feedthrough 15 is not used, a hole may be formed in one side wall of the frame 11, and the metal lead 16 may be insulated and sealed in the hole with glass or the like. Further, the lead 16 and the seal ring 1
7 is formed of a Fe—Ni—Co alloy (commonly known as Kovar) or a copper alloy.

2. Example Next, a specific example of the package 10 having the above-described configuration will be described in detail below in the order of manufacturing steps. (1) Example 1 First, alumina (Al ₂ O ₃ ) powder and zirconia (ZrO ₂ ) powder having an average particle size of 2 μm were used as raw material powders.
Then, alumina was mixed at a mixing ratio of 57 mol% and zirconia at a mixing ratio of 43 mol% to obtain a ceramic mixture. Polystyrene (PS),
A mixed binder in which a thermoplastic resin such as polypropylene (PP) and a wax were mixed was added in an amount of 60% by mass and mixed and kneaded. At this time, using a pressure type kneader, the mixed binder is uniformly dispersed at 170 ° C. for 2 hours.
Time mixing and kneading were performed.

Next, after this kneaded product is pelletized by a pelletizer, the pelletized kneaded product is introduced into the hopper of the injection molding machine and injection molded so as to form a frame 11 having a predetermined shape as shown in FIG. And made it a green body.
At this time, injection molding was performed so that the frame 11 and the window holder 12 were integrally formed. Next, the obtained green body was placed in a binder removal furnace, and then the inside of the binder removal furnace was replaced with nitrogen gas. Thereafter, the inside of the binder removal furnace was heated at a temperature rising rate of 0.25 ° C. for 1 minute, and the temperature of 550 ° C. was maintained for 120 minutes.

As a result, the binder existing in the green body is removed to become a brown body. After cooling this brown body to room temperature, transfer it to a sintering furnace and
The heating was performed at a heating rate of 5 ° C. per minute, and the temperature of 1550 ° C. was finally maintained for 2 hours. As a result, the brown body is sintered to obtain the frame 11 as shown in FIG. After the furnace is cooled to room temperature, the sintered frame 11 is taken out of the sintering furnace to complete the manufacturing process of the frame 11. Alternatively, the frame 11 and the window holder 12 may be separately molded, and then the frame 11 and the window holder 12 may be plated with nickel and joined by brazing with silver brazing.

Further, copper-tungsten alloy (10 wt%
Cu-90 wt% W) block is machined
It was cut into a flat plate shape as shown in FIG. 1 to obtain a flat plate-shaped bottom plate. Then, the obtained flat plate-shaped bottom plate was immersed in a plating bath for electroless plating to form a nickel plating layer having a thickness of 5 μm on the surface of the flat plate-shaped bottom plate, and the flat plate-shaped heat sink 13 was produced. It should be noted that mounting portions are formed at the four corners of the heat sink 13, and openings are provided in the mounting portions to form fixing holes.

A kneaded material of aluminum oxide (Al ₂ O ₃ ) and a binder was injection molded to form a green sheet. At this time, injection molding was performed so that a predetermined wiring was formed on the surface. The obtained green sheet was sintered in the same manner as above to produce a ceramic feedthrough 15 having a shape as shown in FIG. In addition, Fe-Ni-Co
A rolled plate made of an alloy (commonly known as Kovar) was processed into a predetermined shape by chemical etching to produce a lead 16. Furthermore, Fe-Ni-Co alloy (common name: Kovar)
The rolled plate made of was processed into a predetermined shape by chemical etching to produce a seal ring 17.

Next, the frame 1 produced as described above
1, heat sink 13, ceramic feedthrough 1
5, lead 16, seal ring 17 and Mo-Mn
A brazing material (not shown) made of gold is placed as shown in FIG.
Made of carbon or alumina
It was placed on the jig. Then, this jig is replaced with 40% hydrogen (H
₂) Containing nitrogen (N₂) In a gas reflow furnace,
Placed on a belt with a moving speed of 30 mm / min, the maximum temperature
Reflow condition that the material is heated at 900 ℃ for 20 minutes
It heat-processed by (temperature rising profile).

As a result, the frame 11 and the heat sink 13 are joined together, the notch 11a of the frame 11 and the ceramic feed through 15 are joined together, the ceramic feed through 15 and the lead 16 are joined together, and the ceramic feed through 15 and the seal ring 17 are joined together. The assembly main body 10a is formed by being joined and integrated. Further, the frame 11 may be partially or entirely plated. As a result, a part of the electrode terminals of the ceramic feedthrough 15 can be grounded. As the brazing material, a brazing material other than the Mo-Mn alloy described above may be used.

On the other hand, as shown in FIG. 2 (a), there was prepared a body portion 14a made of a ceramic material and having an outer shape slightly smaller than the outer shape of the frame 11. In addition, a quadrangular ring member 14b formed of an Fe-Ni-Co alloy (commonly called Kovar) whose outer shape matches the outer shape of the frame 11 and whose inner shape is slightly smaller than the inner shape of the frame 11. Prepared. Then,
The main body 14a was placed on the ring member 14b, and a brazing material made of a Mo—Mn alloy was interposed between them to place it on a jig made of carbon or alumina. Then, this jig was placed on a belt having a moving speed of 100 mm / min in a reflow furnace in an atmosphere of nitrogen (N ₂ ) gas containing 40% hydrogen (H ₂ ), and the maximum temperature was 850.
The heat treatment was performed under the reflow condition (heating profile) such that heating was performed at 20 ° C. for 20 minutes. Thereby, the main body portion 14a
The ring member 14b and the ring member 14b are integrated to produce the cover 14.

It is desirable that the whole or a part of the cover 14 be nickel-plated or gold (Au) surface-finished nickel-plated. By providing such a plated portion, the corrosion resistance of the ring member 14b can be improved, and the bondability between the cover 14 and the seal ring 17 can be improved. Also,
As shown in FIG. 2B, a main body portion 14a made of a ceramic material and having an outer shape slightly smaller than the outer shape of the frame 11, and a Fe—Ni—Co alloy (common name:
It is also possible to prepare a quadrangular frame member 14c whose outer shape is the same as the outer shape of the frame 11 by Kovar) and to integrally form these by brazing to form the cover 14 in the same manner as described above.

Then, in order to seal the glass window or the alumina window to the window holder 12, the low melting glass and the window were set in the window holder 12 and joined in a reflow furnace. The bonding conditions, with 100% nitrogen (N ₂₎ in a reflow furnace in an atmosphere of gas, the moving speed is disposed on the 100 mm / min belt, maximum temperature reflow conditions as heated at 500 ° C. 10 minutes ( It heat-processed by the temperature rising profile.
As a result, the glass window or the alumina window is sealed to the window holder 12. If gold plating is applied to the entire assembly main body 10a or the window holder 12, a commonly used AuSn solder is used.
A glass window or an alumina window can be bonded to the window holder 12. In this case, it is necessary to preliminarily subject the glass window or the alumina window to the metallization treatment of gold at the joint.

Finally, a cooling body (TEC) composed of a Peltier device, a laser device composed of a semiconductor laser, a lens system and the like are fixed in the assembly body 10a manufactured as described above. After that, the optical axis of the lens is adjusted, the cover 14 is arranged on the upper part of the assembly main body 10a, and these are electrically welded to form the package 10, and
An optical semiconductor module is formed. The package 10 manufactured in this manner is referred to as the package A of Example 1.

(2) Example 2 As a raw material powder, mullite (3Al having an average particle diameter of 2 μm) was used.
_A frame 11 made of a sintered body having a shape as shown in FIG. 1 was produced in the same manner as in Example 1 except that ₂ O ₃ −2SiO ₂ ) powder was used. Also in this case, the frame 11 and the window holder 12 are integrally formed.
In addition, the frame 11 and the heat sink 13 are joined to each other in the same manner as in the first embodiment described above, and the cutout portion 11 of the frame 11 is formed.
a and the ceramic feedthrough 15 are joined, the ceramic feedthrough 15 and the lead 16 are joined, and the ceramic feedthrough 15 and the seal ring 17 are joined and integrated to form an assembly body 10b.

Then, in the same manner as in the first embodiment described above,
A low melting glass and a glass window or an alumina window were set in the window holder 12, and these were joined in a reflow furnace to seal the glass window or the alumina window to the window holder 12.
Lastly, a cooling body (TEC) composed of a Peltier element, a laser device composed of a semiconductor laser, a lens system and the like are fixed in the assembly body 10b. Thereafter, the optical axis of the lens is adjusted, and the cover 14 manufactured in the same manner as in the above-described first embodiment is electrically welded to the upper portion of the assembly body 10b to form the package 10 and the optical semiconductor module. To be done. The package 10 manufactured in this manner was used as the package B of Example 2.

3. Exhaust heat test of package Next, in order to verify the exhaust heat effect of the packages A and B manufactured as described above, an exhaust heat test was conducted as follows with a measurement system as shown in FIG. 4 assembled. For comparison, the package X of the conventional example (package 5 of FIG.
0) was also used. Then, the bottom surface of the Peltier device 20 was joined to the inner bottom surfaces of these packages A, B, and X with PbSn solder. In addition, the Peltier device 20
A thermocouple 22 for checking the cooling temperature of the Peltier device was attached on the upper substrate 21.

Then, instead of the semiconductor laser, a heater 2 having a heat generation amount (400 mW) equivalent to that of the semiconductor laser is used.
3 was used as the heat source. A wire 24 for supplying electric power to the heater 23, a wire 25 for supplying electric power to the Peltier element 20, and a wire 26 for supplying electric power to the thermocouple 22 are provided as pads of the ceramic feedthrough 15 (not shown). Connected to. The cover 14 was then electrowelded in a nitrogen atmosphere as in a normal package. Then, the measurement system thus constructed was installed in an oven (not shown) controlled at 70 ° C.

Since a typical environmental temperature in the system in which the optical semiconductor module is installed is 70 ° C., such a measuring system is heated to 70 ° C. so as to be equal to the environmental temperature in a normal use condition. I am trying to become. Next, in order to investigate the relationship between the temperature of the upper substrate 21 of the Peltier device 20 and the current Itec supplied to the Peltier device 20, the current Itec supplied to the Peltier device 20 is changed, and the upper substrate of the Peltier device 20 at this time is changed. A temperature of 21 was measured. The measurement results are shown in Table 2 below.
In addition, when the results of Table 2 are represented by a graph, the results are as shown in FIG.

[0037]

[Table 2]

In Table 2 and FIG. 5, the required temperature means the temperature at which the semiconductor laser can stably oscillate at a predetermined oscillation wavelength. As is clear from the results in Table 2 and FIG. 5, when the measurement system is heated to 70 ° C. (that is, the environmental temperature is 70 ° C.),
It can be seen that the package X of the conventional example can be cooled only to -4.1 ° C. On the other hand, in the package A of the first embodiment, the supply current Ite to the Peltier device 20 is
It can be seen that when c is 2.2 mA or more, the temperature of the upper substrate 21 of the Peltier device 20 is cooled to the required temperature of -6.2 ° C or less. In the package B of the second embodiment, the current Itec supplied to the Peltier device 20 is 1.9 m.
In A, it can be seen that the temperature of the upper substrate 21 of the Peltier element 20 has already been cooled to the required temperature of -6.2 ° C or less.

This means that, in the package A of the first embodiment and the package B of the second embodiment, even if the environment is as high as 70.degree. It means that it can oscillate at a predetermined oscillation wavelength. This is because, in the package A and the package B, the frame 11 and the cover 14 are made of a ceramic (alumina (Al ₂ O ₃ ) + zirconia (Z) having a low thermal conductivity of 10 W / m · K or less.
rO ₂ ) or mullite (3Al ₂ O ₃ -2SiO ₂ ))
Therefore, as shown by the arrow in FIG. 3, even in a high temperature environment, a small amount of heat can flow into the packages A and B, and most of the heat can be blocked. Probably because it was possible.

On the other hand, in the package X of the conventional example, the frame 51 and the cover 54 are made of a Fe-Ni-Co alloy (common name: Kovar) having a high thermal conductivity of 17 W / mK or less. Since it is formed, it is considered that a large amount of heat has flowed into the package X from the high temperature environment as indicated by the arrow in FIG. Therefore, it is considered that in the package X of the conventional example, the cooling capacity of the Peltier device 20 is lowered due to the high temperature environment of 70 ° C.

The environmental temperature in the system in which the optical semiconductor module is installed may rise to 75 ° C. in the worst case. Therefore, the measurement system is installed in an oven (not shown) controlled at 75 ° C., and the Peltier device 20 is
Temperature of the upper substrate 21 and supply current I to the Peltier device 20
The relationship with tec was measured. Then, the results shown in Table 3 below were obtained. Then, when the results of Table 3 are represented by a graph, the results are as shown in FIG.

[0042]

[Table 3]

As is clear from the results of Table 3 and FIG. 6, when the measurement system is heated to 75 ° C. (that is, the ambient temperature is 75 ° C.), the package A of Example 1 is used.
In, it can be seen that the cooling can be performed only to -2.8 ° C. On the other hand, in the package B of the second embodiment, when the supply current Itec to the Peltier device 20 becomes 2.3 mA or more, the temperature of the upper substrate 21 of the Peltier device 20 is cooled to the required temperature of -6.2 ° C or less. I understand. This means that in the package B of Example 2, the cooling capacity of the Peltier device 20 is sufficiently exhibited even in a high temperature environment of 75 ° C., and the semiconductor laser can oscillate at a predetermined oscillation wavelength. ing.

In the package B, the frame 11 and the cover 14 have a thermal conductivity of 3.5 W / m.multidot.m.
Mullite with low thermal conductivity (3Al ₂ O ₃ -2SiO ₂ )
It is considered that it is possible to prevent the heat outside the package B from flowing into the package B because it is formed of the ceramics. On the other hand, since the package A of Example 1 is formed of a composite ceramic composed of alumina (Al ₂ O ₃ ) and zirconia (ZrO ₂ ) having a low thermal conductivity of 9.8 W / m · K. It is considered that the heat outside the package A could not be sufficiently prevented from flowing into the package A.

From the above, in order to prevent the inflow of heat, the heat conductivity of the frame 11 and the cover 14 is 10%.
It can be said that it is desirable to set it to W / m · K or less. In addition, it can be said that the thermal conductivity of the frame 11 and the cover 14 is preferably 5 W / m · K or less in order to sufficiently prevent the inflow of heat. If the thermal expansion coefficient of the frame 11 and the cover 14 is in the range of 2 ppm / K or more and 10 ppm / K or less, even if the frame 11 and the heat sink 13 or the frame 11 and the cover 14 are joined, It becomes possible to prevent thermal stress from being applied to the bonding interface. From this, it can be said that it is preferable to use the frame 11 and the cover 14 having a coefficient of thermal expansion of 2 ppm / K or more and 10 ppm / K or less. The frame 11 and the cover 1
The material forming 4 is not limited to the above-mentioned ceramic, but may be formed using a material that satisfies the above-described conditions of thermal conductivity and thermal expansion coefficient.

[0046]

As described above, in the present invention, since the frame 11 and the cover 14 are made of a material having a low thermal conductivity, even if the inside of the package 10 is cooled to a temperature lower than room temperature, The external heat is the frame 11
And it becomes possible to prevent the inflow through the cover 14. Further, since the heat sink 13 is made of a material having high thermal conductivity, the heat generated in the package 10 can be efficiently released (exhausted heat) to the outside of the package 10. As a result, this package 10
It is possible to reduce the size and power consumption of the optical semiconductor module using the.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing components used in a package of the present invention.

FIG. 2 is a perspective view showing a cover of the present invention.

FIG. 3 is a perspective view showing a package before a cover is attached to an assembly main body formed by assembling the components shown in FIGS. 1 and 2.

[Fig. 4] In order to verify the heat exhaustion effect of the packages A and B, an exhaust heat test is performed by assembling a measurement system as shown in Fig. 4.

FIG. 5 Heater heat (W) and thermoelectric cooler (TEC)
It is a figure which shows the relationship of the making electric current (A) to.

FIG. 6 Heater heat (W) and thermoelectric cooler (TEC)
It is a figure which shows the relationship of the making electric current (A) to.

FIG. 7 is a perspective view showing components used in a conventional package.

FIG. 8 is a perspective view showing a package formed by assembling the components shown in FIG.

[Explanation of symbols]

10 ... Package, 10a, 10b ... Assembly body, 11 ...
Frame, 11a ... Notch, 12 ... Window holder, 13 ... Heat sink, 14 ... Cover, 14a ... Main body, 14b ...
Ring member, 14c ... Frame member, 15 ... Ceramic feed through, 16 ... Lead, 17 ... Seal ring, 20 ...
Peltier element, 21 ... Upper substrate, 22 ... Thermocouple, 23 ... Heater, 24 ... Wiring, 25 ... Wiring, 26 ... Wiring

Claims (6)

[Claims] 1. A package for an optical semiconductor module, comprising a frame accommodating an optical semiconductor module, a heat sink serving as a bottom plate of the frame, and a cover hermetically covering the frame, wherein the frame and the cover have low thermal conductivity. And a heat sink made of a material having a low coefficient of thermal expansion, and the heat sink is made of a material having a high coefficient of thermal conductivity and a low coefficient of thermal expansion. 2. The material having a low thermal conductivity and a low thermal expansion coefficient,
Thermal conductivity of 10 W / mK or less, thermal expansion coefficient of 2 ppm
/ K or more and 10 ppm / K or less, The package for optical-semiconductor modules of Claim 1 characterized by the above-mentioned. 3. The material having a low thermal conductivity and a low coefficient of thermal expansion is
The package for an optical semiconductor module according to claim 1 or 2, which is a ceramic containing at least one selected from zirconium oxide, mullite, stearite, cordierite, and fosterite as a main component. 4. The optical semiconductor module according to claim 1, wherein an iron-nickel-cobalt alloy or an iron-nickel alloy is arranged on the upper portion of the frame. package. 5. The optical semiconductor according to claim 1, wherein an iron-nickel-cobalt alloy or an iron-nickel alloy is arranged on at least a peripheral portion of the cover. Module package. 6. A window holder for fixing a window member that transmits light to one side wall of the frame is provided, and the window holder is formed integrally with the frame. Item 5. An optical semiconductor module package according to any one of items 5.