JPH08160271A - How to join optical components - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a method for strongly joining optical components by soldering. [Structure] A metal thin film is formed in multiple layers on the surface of a non-transmissive portion of the optical component 1 and / or on the surface of a holding member 5 of the optical component. The outermost layer 2 of the multi-layered metal thin film is made of 99.5% or more of gold, and the surface thereof is soldered to connect the optical parts.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for joining optical components incorporated in an optical isolator or the like used for optical communication.

[0002]

2. Description of the Related Art Various optical components such as a polarizer and an analyzer are used in optical communication systems and optical measuring instruments. These optical components are incorporated in an optical isolator or the like. The optical isolator is provided in the transmission path and transmits only the light traveling in the planned transmission direction and selectively blocks the reflected light returning to the light source. In order to improve the performance of the optical isolator, the incorporated optical components must be strongly bonded.

The optical isolator is usually used by being joined to an optical fiber or the like. Since the transmitted light is flowing through the optical fiber, the temperature of the fiber rises with the passage of time. As the temperature of the fiber rises, the temperature inside the optical isolator also rises.

The optical components in the optical isolator were bonded with an organic adhesive. Due to the temperature rise of the optical isolator or the temperature change of the outside, gas may be generated from the adhesive agent, or the adhesive agent may expand and the fixing position of the optical component may be displaced. For this reason, the temperature range in which the optical isolator can be effectively used is narrowed, and in recent years, instead of the adhesive, the optical components are joined with solder, which is an alloy of tin and lead.
Usually, a metal thin film is formed on the surface of the optical component,
Solder was attached to the surface of this metal thin film, and the optical components were joined together by the joining force of the solder.

However, when the optical components are joined by solder, creep may occur in the solder due to a change in external temperature. Furthermore, if the purity of the metal thin film bonded to the solder is low, the metal thin film will be altered by the heating when melting the solder, and it will not be possible to bond optical parts, or the bonding strength between the bonded optical parts will be low. turn into.

As one of means for strongly joining optical parts with solder, there is a method of adding a flux when melting the solder. However, the addition of the flux deteriorates the characteristics of the optical component. Furthermore, when an optical isolator is assembled with these optical components, the durability of the optical isolator becomes low due to the residue of the flux. In particular, rust occurs at high temperature and high humidity.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a method for strongly joining optical components by soldering.

[0008]

A method for joining optical components according to the present invention, which has been made to achieve the above object, will be described with reference to FIG. As shown in the figure, a metal thin film is formed in multiple layers on the surface of the light non-transmissive portion of the optical component 1 and / or the surface of the holding member 5 of the optical component. Outermost layer 2 of the multi-layer metal thin film is made of 99.5% or more of gold, and the surface thereof is solder
Attach 0 to connect the optical components. The outermost layer 2 is formed by gold plating, gold vapor deposition, and gold sputtering.

[0009]

The outermost layer 2 of the optical component 1 and the holding member 5 of the optical component is 99.5% or more of gold. Even when the solder 10 is heated and melted on the surface of the outermost layer 2, the outermost layer 2 has a high content of gold, and therefore the impurities precipitated on the surface by heat are extremely small. When the amount of precipitated impurities is small, the bonding force between the solder 10 and the outermost layer 2 becomes strong. Therefore, the solder 10 can strongly bond the optical component 1.

[0010]

FIG. 1 is a sectional view showing an embodiment of a method of joining optical parts to which the present invention is applied. As shown in the figure, a plurality of metal thin films are formed on the surface of the non-translucent portion of the optical component 1. The metal thin film which is the outermost layer 2 is 99.5.
% Or more of money. The layers other than the outermost layer 2 may be metal thin films, and any number of layers may be formed.

The holding member 5 of the optical component has a plurality of metal thin films formed on its surface. Similar to the optical component 1, the metal thin film serving as the outermost layer 2 is 99.5% or more of gold, and the layers other than the outermost layer 2 may be any metal thin film, and any number of layers may be formed.

Solder 10 is attached to the outermost layer 2, and the optical component 1 and the holding member 5 of the optical component are joined by the solder 10.

FIG. 2 is a sectional view of an embodiment of the optical component. As shown in the figure, the optical component 1 is made of a glass material, and three layers of metal thin films are formed in the non-light-transmitting portion.
The outermost layer 2 of the three-layered metal thin film is 99.5% or more of gold. The inner layer 3 that is in contact with the non-light-transmitting portion has chromium as a main component, and the intermediate layer 4 between the inner layer 3 and the outermost layer 2 has platinum as a main component.

FIG. 3 is a sectional view of an embodiment of a holding member for an optical component. As shown in the figure, the holding member 5 is made of a metal material and has a two-layer metal thin film formed on its surface. The outermost layer 2 of the two-layered metal thin film is 99.5% or more of gold. The inner layer 3 in contact with the surface portion contains nickel as a main component.

FIG. 4 is a sectional view of an optical isolator assembled by the method of joining optical components to which the present invention is applied. As shown in the figure, a polarizer 25, a Faraday rotator 23, and an analyzer 26 are sequentially arranged in the outer cylinder 21 from the light incident side. The Faraday rotator 23 is surrounded by the magnet 22. Polarizer 25, magnet 22 and analyzer 26
Are held by a holder 24. Polarizer 25,
Metal thin films (not shown) are formed on the non-light-transmitting portions of the Faraday rotator 23 and the analyzer 26. Each optical component and the holding member are joined by the solder 10.

The light incident on the optical isolator is a polarizer 25.
Through the Faraday rotator 23,
Rotate once. The rotation causes the plane of polarization of the light to coincide with the analyzer 26, so that the light can pass through the analyzer 26. After the reflected light enters the analyzer 26 from the opposite direction, the Faraday rotator 2
It is incident on 3. The Faraday rotator 23 rotates the polarization plane of the reflected light from the opposite direction by 45 degrees and is orthogonal to the polarization plane of the polarizer 25. Therefore, the reflected light is blocked by the polarizer 25.

The stainless steel 304 was processed to produce the magnet 22 and the holder 24, and nickel plating was applied to the surfaces of the magnet 22 and the holder 24 to produce the inner layer 3 of 3 μm. Further, the magnet 22 having the inner layer 3 formed thereon was dipped in a gold plating solution to perform gold plating to form the outermost layer 2 having a thickness of 1 μm. The gold content in the plating solution was 99.99% or more. When the outermost layer 2 was measured by fluorescent X-ray, the gold content was 99.9%. When Kovar is used as the base material instead of stainless steel, the inner layer 3 has a thickness of 4 μm and the outermost layer 2 has a thickness of 1.
It is preferably 5 μm.

Next, the glass was processed to prepare a polarizer 25 and a Faraday rotator 23. Faraday rotator 23
A liquid layer epitaxial garnet film is formed on the surface of the. Chromium was vapor-deposited to a thickness of 100 nm on the non-light-transmitting portion of each component to form the inner layer 3, and then platinum was vapor-deposited to a thickness of 200 nm on the inner layer 3 to form the intermediate layer 4.
Further, gold is deposited on the intermediate layer 4 to a thickness of 800 nm (0.8 μm).
m) was vapor-deposited to form the outermost layer 2. At this time, the gold content of the outermost layer 2 was 99.99% or more.

The solder 10 was heated and melted at 380 ° C. and adhered to the outermost layer 2 of the optical component. Solder 10 has 8 gold
8%, germanium 12% composition, melting point 35
6 ° C. Finally, after adjusting the relative angle between the polarizer 25 and the analyzer 26 to be 45 degrees, the outer tube 21 on the analyzer 26 side and the holder 24 were joined by the solder 10 to complete the optical isolator. At this time, the solder 10 is gold 8
The composition is 0%, tin is 20%, and the melting point is 280 ° C.
Met.

The joining of the respective parts by the solder 10 was carried out in the presence of an inert gas such as nitrogen or argon, or by mixing an inert gas with hydrogen gas. At this time, the flux which affects the optical characteristics was not added.

A shock resistance test was conducted using this optical isolator. The test conditions were changed to a high temperature (125 ° C.), a low temperature (−50 ° C.), a high temperature and high humidity (100 ° C., 90%), and an impact of 2000 grams was given to the optical isolator under each condition. No change in characteristics, deterioration, or discoloration of appearance was observed in the optical isolator.

By changing the content ratio of gold contained in the outermost layer,
An optical isolator was assembled in the same manner as described above, and the bonding strength, discoloration of appearance and durability of optical components were evaluated, and the results are shown in Table 1.

[0023]

[Table 1]

From Table 1, it can be seen that the bonding strength is lowered when the gold content is 99.4% or less. Content rate is 9
If the flux is added even at 9.4% or less, the joint strength between the components will be good, but the appearance will be discolored and the durability will be reduced. When the content of the outermost layer 2 was 89% when the content was 89%, cobalt, nickel and potassium were detected as impurities.

[0025]

As described above in detail, since the joining method of the present invention strengthens the joining force of the optical parts, the optical isolator can be easily assembled. Since the optical isolator, which has a strong bonding force for optical components, has excellent durability, it can be used for a long time under a wide range of temperature conditions.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a method of joining optical components to which the present invention is applied.

FIG. 2 is a sectional view of an example of an optical component.

FIG. 3 is a sectional view of an example of a holding member for an optical component.

FIG. 4 is a cross-sectional view of an optical isolator assembled by the method of joining optical components according to the present invention.

[Explanation of symbols]

1 is an optical component, 2 is an outermost layer, 3 is an inner layer, 4 is an intermediate layer, 5
Is a holding member for optical parts, 10 is solder, 21 is an outer cylinder, 22
Is a magnet, 23 is a Faraday rotator, 24 is a holder, 2
Reference numeral 5 is a polarizer, and 26 is an analyzer.

Claims (4)

[Claims] 1. A surface of a light non-transmissive portion of an optical component or /
And a metal thin film is formed in multiple layers on the surface of a holding member of the optical component, the outermost layer of the metal thin film of the multilayer is made 99.5% or more of gold, and the surface is soldered. Joining method. 2. The method for joining optical components according to claim 1, wherein the metal thin film serving as the outer layer is formed by gold plating. 3. The method for joining optical components according to claim 1, wherein the metal thin film serving as the outer layer is formed by vapor deposition of gold. 4. The method for joining optical components according to claim 1, wherein the metal thin film serving as the outer layer is formed by sputtering gold.