JP2001068691A - Package for housing optical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a package for housing an optical element which enables the high-speed modulation of light by using an optical element by preventing efficiently an optical element placed on a substrate from being curved and peeled off, improve a combination efficiency between the optical element and light by preventing the birefringence of a light transmitted through an optical fiber in a light-transmissive window member, and operate the optical element normally and stably for a long time by housing the optical element airtightly. SOLUTION: This package for housing an optical element is provided with a substrate l and a frame body 2 which are made of austenic stainless steel of which coefficient of thermal expansion is approximate to that of an optical element 6 made of lithium niobate, and a light-transmissive window member 4 is fitted to a frame body 2 by means of a circular member 3 having Young's modulus of 17000 kg/mm2 or less, thereby absorbing and releasing a thermal stress in the package. A combination efficiency between the optical element 6 and light is made appropriate, and the high-speed modulation characteristic of light in the optical element 6 is hard to be deteriorated and the optical element can be housed airtightly in the package.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical element housing package for housing an optical element.

[0002]

2. Description of the Related Art Conventionally, a package for housing an optical semiconductor element for housing an optical semiconductor element is generally made of iron-nickel-
It is made of a metal such as a cobalt alloy or a copper-tungsten alloy, and has a mounting portion on which the optical semiconductor element is mounted in the center of the upper surface.A plurality of external lead terminals are provided around the mounting portion with insulating members such as glass. A metal base fixed so as to penetrate from the upper surface to the lower surface, and a through hole formed on the side of the metal base so as to surround the optical semiconductor element mounting portion via a brazing material such as silver brazing. From a metal frame having a low melting point brazing material such as a gold-tin alloy having a melting point of 200 ° C. to 400 ° C. so as to cover the through holes of the metal frame. And a lid attached to the upper surface of the metal frame to hermetically seal the optical semiconductor element. The optical semiconductor element is mounted and fixed on the mounting portion of the metal base. At the same time, each electrode of the optical semiconductor element is externally connected via a bonding wire. The optical semiconductor device is electrically connected to the terminal, and the lid is joined to the upper surface of the metal frame so that the optical semiconductor element is airtightly accommodated, and the optical fiber is YAG-welded or carbon dioxide laser-welded to the through-hole of the metal frame. An optical semiconductor device as a product can be obtained by bonding.

In such an optical semiconductor device, an optical semiconductor element is optically excited by a drive signal supplied from an external electric circuit, and the excited light is transmitted to and received from an optical fiber through a light transmitting window member, and is transmitted through the optical fiber. By doing so, it functions as an optical semiconductor device used for high-speed optical communication and the like.

In addition, instead of the optical semiconductor element, an optical element storing package for accommodating an optical element that modulates light introduced into the package at a high speed has the same structure as the optical semiconductor element storing package. Similarly, it is used as an optical semiconductor device used for high-speed optical communication and the like.

[0005]

However, in the case of an optical element housing package for housing an optical element made of a material different from that of the optical semiconductor element, the optical element is made of lithium niobate having a thermal expansion coefficient of about 16 ppm / ° C. Since an optical waveguide chip consisting of: is used, as a base of an optical element housing package, like a conventional optical semiconductor element housing package,
Iron with a coefficient of thermal expansion of about 10 ppm / ° C (at room temperature to 800 ° C)
Nickel-cobalt alloy and thermal expansion coefficient about 7ppm / ℃
When a copper-tungsten alloy (at room temperature to 800 ° C.) is used, problems such as bending or peeling of the optical element may occur due to stress caused by a difference in thermal expansion between the base and the optical element. In addition, there is a problem that the high-speed modulation characteristic of light of the optical element is deteriorated such as the spread of the wavelength spectrum.

On the other hand, a frame made of an iron-nickel-cobalt alloy having a different coefficient of thermal expansion is joined to the upper surface of a base made of stainless steel having a coefficient of thermal expansion similar to that of an optical element with a brazing material such as silver brazing. Can be considered. However, even in this case, since the base is curved due to the difference in thermal expansion between them, when the optical element is adhered and fixed on the base, a problem such as the bending of the optical element occurs. There is a problem that the modulation characteristics are deteriorated.

Further, when the base and the frame are made of stainless steel, the light transmitted through the optical fiber becomes amorphous due to the stress generated by the difference in thermal expansion between the light transmitting window member and the frame. There has been a problem that birefringence occurs in a light-transmitting window member made of high-quality glass or the like, and the coupling efficiency between an optical element and light deteriorates. Further, finally, the stress causes cracks in the amorphous glass, which causes a problem that it is difficult to hermetically accommodate the optical element.

The present invention has been devised in view of the above problems, and has as its object to effectively prevent an optical element mounted on a substrate from being bent or peeled off, thereby enabling an optical element to emit light. High-speed modulation, and by effectively preventing light transmitted from the optical fiber from causing birefringence in the translucent window member, the coupling efficiency between the optical element and the light is improved. Another object of the present invention is to provide an optical element storage package that can operate the optical element normally and stably for a long period of time by hermetically storing the optical element.

[0009]

According to the present invention, there is provided an optical element storage package having a base having a mounting portion on which an optical element made of lithium niobate is mounted, and surrounding the optical element on the base. A frame having a through-hole on the side part attached to the frame, a translucent window member attached to the frame and closing the through-hole, and an air-tight element mounted on the top of the frame and sealing the optical element. A package for sealing an optical element, wherein the package and the frame have a coefficient of thermal expansion of 14 to 19 p.
pm / ° C., wherein the translucent window member is attached to the frame via an annular member having a Young's modulus of 17,000 kg / mm ² or less. is there.

According to the package for accommodating an optical element of the present invention, as a package structure for accommodating an optical element made of lithium niobate, an austenitic stainless steel having a coefficient of thermal expansion of 14 to 19 ppm / .degree. From about 16 ppm / ° C.
Almost no stress due to the difference in thermal expansion occurs between the optical element made of lithium niobate and the base and between the base and the frame, so that problems such as bending of the base and the optical element do not occur. As a result, it is possible to effectively prevent the deterioration of the high-speed modulation characteristic of light of the optical element, and it is possible to firmly join the base and the frame.

In addition, a light transmitting window member made of amorphous glass or the like having a thermal expansion coefficient of about 9 ppm / ° C. for condensing light transmitted from the optical fiber and a frame made of stainless steel are joined together. By joining an annular member having a Young's modulus of 17000 kg / mm ² or less between the translucent window member and the frame using a brazing material such as silver brazing, the translucent window member and the frame are joined together. The stress due to the difference in thermal expansion generated between them can be sufficiently relaxed, and does not cause birefringence or cracks in the translucent window member, thereby improving the coupling efficiency between the optical element and light. In addition, the optical element can be housed in an airtight manner and operated normally and stably for a long period of time.

[0012]

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

FIG. 1 is a cross-sectional view showing an example of an embodiment of an optical element storage package according to the present invention, and FIG. 2 is an enlarged cross-sectional view of a main part thereof. In these figures, 1 is a substrate, 2
Is a frame, 3 is an annular member, 4 is a translucent window member, 5 is a lid,
6 is an optical element. The base 1, the frame 2, the annular member 3, the translucent window member 4, and the lid 5 constitute a container for housing the optical element 6 therein.

The base 1 functions as a support member for supporting the optical element 6, and has a mounting portion 1a for mounting the optical element 6 at a substantially central portion of the upper surface thereof. Part 1
An optical element is bonded and fixed to a by an adhesive such as tin-lead solder.

The substrate 1 has, for example, a thermal expansion coefficient of about 16p.
Since the optical element 6 made of lithium niobate at pm / ° C. is adhered and fixed to the upper surface, stress due to a difference in thermal expansion occurs between the optical element 6 and the base 1, and the optical element 6 may be bent. In order not to cause a problem such as peeling or the like, a metal material that is close to the coefficient of thermal expansion of the optical element 6, that is,
It is preferably made of stainless steel having a coefficient of thermal expansion of 14 to 19 ppm / ° C (at room temperature to 400 ° C). Further, it is preferable that the stainless steel is made of austenitic stainless steel having more excellent corrosion resistance by containing nickel. Such a stainless steel has, for example, a thermal expansion coefficient of about 15 ppm / ° C. (room temperature to 40 ° C.).
(At 0 ° C) chromium 25 wt%-nickel 20 wt%-carbon 0.06 wt%-iron (SUS310S)
18 wt% chromium at 18 ppm / ° C. (at room temperature to 400 ° C.) — 10 wt% nickel—iron (SUS304), and 18 watts of chromium at a thermal expansion coefficient of about 17 ppm / ° C.
t% -nickel 12 wt% -molybdenum 2.5 wt% -carbon 0.06 wt% -iron (SUS316) can be suitably used. The base 1 made of stainless steel is manufactured by subjecting a stainless steel ingot of SUS304 to a conventionally known metal working method such as a rolling method or a punching method.

The substrate 1 has a metal having excellent corrosion resistance on its outer surface and good wettability to a brazing material, specifically, a nickel layer having a thickness of 2 to 6 μm and a gold layer having a thickness of 0.5 to 5 μm. If the layers are sequentially applied by plating, the substrate 1 can be effectively prevented from being oxidized and corroded, and the optical element 6 can be firmly adhered and fixed to the upper surface of the substrate 1. Therefore, when the substrate 1 effectively prevents oxidative corrosion and firmly adheres and fixes the optical element 6, a nickel layer having a thickness of 2 to 6 μm and a thickness of 0.5 to 5 μm are formed on the outer surface thereof.
It is preferable that a gold layer of μm is sequentially applied by a plating method.

The base 1 has a plurality of external lead terminals 7 penetrating the base 1 fixed around a mounting portion 1a on which the optical element 6 is mounted via an insulating member 8 such as glass. .

The external lead terminal 7 has a function of electrically connecting each electrode of the optical element 6 to an external electric circuit. One end of the external lead terminal 7 is connected to the electrode of the optical element 6 via a bonding wire 11. The other end is connected to an external electric circuit via a low-temperature brazing material such as solder.

The external lead terminal 7 is made of a metal material such as an iron-nickel-cobalt alloy or an iron-nickel alloy, and is fixed to the base 1 by forming a hole having a diameter slightly larger than that of the external lead terminal 7 in the base 1. In this case, the ring-shaped insulating member 8 made of glass and the external lead terminal 7 are inserted through the hole, and then the insulating member 8 made of glass is heated and melted.

The external lead terminal 7 is provided with a plating metal layer having excellent corrosion resistance such as a nickel plating layer and a gold plating layer on its surface and having good wettability with a brazing material in a range of 1.0 μm to 20 μm.
If it is applied to a thickness of m, oxidation corrosion of the external lead terminal 7 can be effectively prevented and the connection between the external lead terminal 7 and the bonding wire 11 can be made strong. Therefore, the external lead terminal 7 is provided with a plating metal layer having excellent corrosion resistance such as a nickel plating layer and a gold plating layer on its surface and having good wettability with a brazing material in an amount of 1.0 μm to 20 μm.
It is preferable that the film is adhered to a thickness of 10 mm.

A frame 2 is joined to the upper surface of the base 1 so as to surround the mounting section 1a on which the optical element 6 is mounted. The optical element 6 is housed inside the frame 2. A space is formed to allow for

The frame 2 can be effectively bonded to the base 1 by effectively preventing stress due to a difference in thermal expansion from the base 1, and has a thermal expansion similar to that of the base 1 so as to have corrosion resistance. It is preferably made of austenitic stainless steel having a coefficient of 14 to 19 ppm / ° C (at room temperature to 400 ° C).
The frame 2 made of stainless steel is, for example, a base 1
It is formed by pressing a stainless steel ingot having the same composition as that of the above into a frame shape by press working. The attachment to the base 1 is performed by brazing the upper surface of the base 1 and the lower surface of the frame 2 through a brazing material such as silver brazing. Done by

A through hole 2a is formed in the side of the frame 2. The through-hole 2a functions as a transmission hole for transmitting light excited outside to the optical element 9 housed therein after being transmitted through the optical fiber 9 and condensed by the translucent window member 4. The body 2 is formed into a predetermined shape by performing a conventionally known drilling process on the side portion.

Further, an annular member 3 such as a circular ring or a square ring is attached to the inner surface around the through hole 2a with a brazing material, and the translucent window member 4 is further attached to the annular member 3 with a brazing material. Has been attached.

The annular member 3 may be attached to the outer surface around the through hole 2a with a brazing material, as shown in an enlarged sectional view of a main part in FIG. In the case of this example, the attachment of the annular member 3 to the frame 2 and the attachment of the translucent window member 4 to the annular member 3 are very easy because they are attached from outside the package. The brazing for accommodating the inside of the package in an airtight manner can be stably performed. FIG.
When a recess is formed in the outer surface around the through hole 2a of the frame body 2 as shown in (1) and the translucent window member 4 attached via the annular member 3 is accommodated therein, Since the concave portion of the frame 2 supports the translucent window member 4, the translucent window member 4 does not cause extreme displacement, and the optical fiber 9
Good transmission of light from the light transmitting member to the translucent window member 4 can be secured.

Further, since the translucent window member 4 is completely accommodated in the concave portion of the frame 2 without protruding outside the package, the package can be reduced in size.

The annular member 3 relieves the stress generated due to the difference in thermal expansion between the frame 2 and the light-transmitting window member 4 and, at the same time, prevents the inside of the package from leaking at 17,000 k.
g / mm ² or less, specifically, a metal material such as an iron-nickel-cobalt alloy or an iron-nickel alloy, for example, nickel 29 wt% -cobalt 17 wt% -manganese 0.5 wt% or less- Silicon 0.2 w
t% or less-Carbon 0.06wt%-Iron alloy and iron 50wt%-
It is formed by forming an ingot of a nickel 50 wt% alloy into a circular ring or a rectangular ring by pressing.

The Young's modulus of the annular member 3 is 13500 kg.
In the case of a metal material of less than / mm ² , it tends to be difficult to make the inside of the package airtight. In particular,
The frame 2 and the translucent window member 4 have too large thermal expansion coefficients.
There is a tendency that it is difficult to form a good bond with the transparent window member 4, and it is difficult to bond the translucent window member 4 with high precision due to extremely large deformation. On the other hand, the Young's modulus
In the case of a metal material exceeding kg / mm ² , there is a tendency that the stress due to the difference in thermal expansion between the frame 2 and the translucent window member 4 cannot be sufficiently reduced.

The annular member 3 functions as a base fixing member for fixing the translucent window member 4 to the frame 2 and also has a thermal expansion generated between the frame 2 and the translucent window member 4. One principal surface side is attached to the outer surface or inner surface around the through hole 2a of the frame 2 via a brazing material such as silver brazing, and the other principal surface is provided. On the side, a metal film previously attached to the outer peripheral portion of the translucent window member 4
10 is attached via a brazing material such as a gold-tin alloy.

The translucent window member 4 has a thermal expansion coefficient of 4 to 12 pp.
It is made of sapphire or amorphous glass at m / ° C. (at room temperature to 400 ° C.), and acts as a light condensing member when light excited outside is transmitted through the optical fiber 9 to the inside of the container. The collected light is transmitted to the optical element 6. For example, in the case of an amorphous glass having no crystal axis, a lead-based material containing silicon oxide and lead oxide as main components and a borosilicate-based material containing boric acid and silica sand as main components are used.

Further, even if the translucent window member 4 has a different thermal expansion coefficient from that of the frame 2, the annular member 3 absorbs and relaxes the stress due to the difference in thermal expansion, so that the crystal axis has a stress due to the stress. In addition, it does not cause a change in the refractive index of light by aligning in a certain direction.

Therefore, the light that is excited outside and propagates through the optical fiber 9 and is condensed by the translucent window member 4 is transmitted to the optical element 6 without causing birefringence.
The coupling efficiency between light and light can be increased.

As shown in FIG. 4, the light transmitting window member 4 is attached to the annular member 3 by, for example, previously attaching a metal film 10 to the outer periphery of the light transmitting window member 4. This is performed by brazing the metal film 10 and the annular member 3 via a brazing material such as a gold-tin alloy. In this case, since the attachment of the translucent window member 4 to the annular member 3 is performed by brazing with a gold-tin alloy or the like, the attachment is highly reliable. Airtight sealing of the container accommodating the optical element 6 at the attachment portion with the window member 4 is completed, and the optical element 6 accommodated in the container can be normally and stably operated for a long period of time.

Further, the frame 2 is provided on its upper surface with, for example, iron-
A lid 5 made of a metal material such as a nickel-cobalt alloy or an iron-nickel alloy is joined, thereby forming a container comprising the base 1, the frame 2, the annular member 3, the light transmitting window member 4, and the lid 5. The optical element 6 can be hermetically sealed inside.

The joining of the lid 5 to the upper surface of the frame 2 is performed by, for example, welding such as a seam welding method.

Thus, according to the optical element housing package of the present invention, the optical element 6 made of lithium niobate is mounted and fixed on the optical element mounting section 1a of the base 1, and each electrode of the optical element 6 is bonded to the bonding wire 11 Is electrically connected to the external lead terminal 7 through the outer peripheral surface of the annular member 3 on the outer surface of the side portion or the inner surface of the side portion around the through hole 2a provided on the side portion. On the other main surface side, a metal film 10 attached to the outer peripheral portion of the translucent window member 4 in advance via a brazing material is attached via a brazing material such as a gold-tin alloy. The lid 5 is bonded to the upper surface of the frame 2 having a structure of a side portion, and the base 1, the frame 2, the annular member 3, and the light-transmitting window member 4
The optical element 6 is accommodated in a container composed of the lid 5 and the optical element 6, and finally, the optical fiber 9 is attached and connected to the side of the frame 2, thereby forming an optical element device as a final product. The light excited outside propagates through the optical fiber 9 and is condensed by the translucent window member 4 made of amorphous glass or the like.
It is used for high-speed optical communication etc. by being transmitted to.

[0037]

According to the optical device housing package of the present invention, as the package structure for housing the optical device made of lithium niobate, the base and the frame are made of austenite having a thermal expansion coefficient of 14 to 19 ppm / ° C. The thermal expansion coefficient is about 16ppm / ℃
Almost no stress due to the difference in thermal expansion occurs between the optical element made of lithium niobate and the base and between the base and the frame, so that problems such as bending of the base and the optical element do not occur. As a result, it is possible to effectively prevent deterioration of the high-speed modulation characteristic of light of the optical element, and it is possible to firmly join the base and the frame.

In addition, a light transmitting window member made of amorphous glass or the like having a thermal expansion coefficient of about 9 ppm / ° C. for condensing light transmitted from an optical fiber and a frame made of stainless steel are joined together. By joining an annular member having a Young's modulus of 17000 kg / mm ² or less between the translucent window member and the frame using a brazing material such as silver brazing, the translucent window member and the frame are joined together. The stress due to the difference in thermal expansion generated between them can be sufficiently relaxed, and does not cause birefringence or cracks in the translucent window member, thereby improving the coupling efficiency between the optical element and light. In addition, the optical element can be housed in an airtight manner and operated normally and stably for a long period of time.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of an embodiment of an optical element storage package according to the present invention.

FIG. 2 is an enlarged sectional view of a main part of the optical element housing package shown in FIG.

FIG. 3 is an enlarged sectional view of a main part of an example in which the annular member and the translucent window member shown in FIG. 2 are attached to a side outer surface of a frame body.

FIG. 4 is an enlarged sectional view of a main part showing an example in which a metal film is applied to a light transmitting window member.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Base 1a ... Placement part 2 ... Frame 2a ... Through-hole 3 ... Annular member 4 ... Translucent window member 5 ... Lid 6 ... ... Optical elements

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) H01L 23/06 H01L 23/06 B 31/0232 33/00 M 33/00 31/02 C

Claims (3)

[Claims] 1. A base having a mounting portion on which an optical element made of lithium niobate is mounted on a top surface, and a frame mounted on the base so as to surround the optical element and having a through hole on a side portion. An optical element housing package comprising a body, a translucent window member attached to the frame body to close the through hole, and a lid attached to the upper surface of the frame body to hermetically seal the optical element. And
The optical element, wherein the base and the frame are made of stainless steel, and the translucent window member is attached to the frame via an annular member having a Young's modulus of 17000 kg / mm ² or less. Package for storage. 2. The stainless steel has a coefficient of thermal expansion of 14 to 14.
2. The package for housing an optical element according to claim 1, wherein the package is made of austenitic stainless steel at 19 ppm / .degree. 3. The package for housing an optical element according to claim 1, wherein the annular member is made of an iron-nickel alloy or an iron-nickel-cobalt alloy.