JP2006309193A - Optical device and manufacturing method thereof - Google Patents

Abstract

To provide an optical device with higher reliability by suppressing deterioration of an antireflection film during bonding.
An optical device in which an optical element is fixed to a holder by a bonding material,
It the bonding material, SnO a _30~70mol%, P 2 _{O 5} and 20 to 50 mol%, a lead-free low-melting-point glass containing 5 to 30 mol% of MnO.
[Selection] Figure 1

Description

  The present invention relates to an optical device and a fixing method thereof, and more particularly to an optical device in which an optical element used in various modules for optical fiber communication is fixed to a holder and a manufacturing method thereof.

  When optical elements such as lenses, prisms, and optical crystals are incorporated into a specific device such as a module for optical fiber communication, these optical elements are fixed to a holder and used as an optical device that is easy to handle. The structure of a conventional optical device is shown in FIG. The optical element 1 is fixed to the holder 2 with a bonding material 3.

  Here, an adhesive or an alloy solder of lead and tin is used as the bonding material. However, when an adhesive is used, the adhesive generally has high hygroscopicity, so that it tends to be brittle depending on environmental conditions. Moreover, since the glass transition temperature is low, there is a problem that the operating temperature of the optical device using the adhesive becomes relatively narrow. In addition, since there is a problem that outgassing occurs, there is also a problem that long-term reliability is lacking.

On the other hand, since the alloy solder of lead and tin has a relatively low melting point, particularly when a load such as gravity is always applied to the solder joint, a creep phenomenon that the alloy solder is distorted with time tends to occur. For this reason, when the alloy solder is used, the position of the optical element 1 changes with time, and there is a problem that the stability of the optical system over a long period cannot be secured. Further, the alloy solder of lead and tin is 250 × 10 ⁻⁷ / ° C., which is a great difference from the thermal expansion coefficient 120 × 10 ⁻⁷ / ° C. of the optical element 1. Therefore, when fixing with this alloy solder, due to the difference in thermal expansion coefficient, stress is applied to the optical element during cooling of the alloy solder, which may cause problems such as cracking and birefringence. Also, if there is a change in ambient temperature due to a temperature change or heat generation of an electronic circuit, tensile and compressive stresses are repeatedly applied to the solder joint. Due to this thermal fatigue, there is a problem that the solder is cracked, the position of the optical element 1 is changed, and the optical axis is shifted.

On the other hand, a method of using a low-melting glass mainly composed of lead oxide as a bonding material has been proposed (for example, Patent Document 1), and a certain effect is obtained with respect to the above problem.
JP-A-2-281201

  In recent optical elements, an antireflection film is provided in order to prevent deterioration of optical characteristics due to a decrease in utilization efficiency of incident light. However, the heat resistance of a normal antireflection film is 400 ° C. or lower, which is lower than about 450 ° C., which is the firing temperature of lead oxide-based low-melting glass. There has been a problem that the antireflection film is deteriorated and the reliability of the optical characteristics of the optical device is lowered. In addition, from the viewpoint of environmental protection, there is also a problem that a joining method that does not use lead oxide is required.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an optical device that does not use lead oxide and a method for manufacturing the same while improving the reliability of optical characteristics.

In order to solve the above problems, an optical device of the present invention is an optical device in which an optical element is fixed to a holder with a bonding material, and the bonding material contains 30 to 70 mol% of SnO and 20 of P ₂ O ₅ . It is a lead-free low melting glass containing ˜50 mol% and MnO 5˜30 mol%.

Moreover, the total content of SnO and P ₂ O _{5 in} the bonding material is 70 mol% or more.

  Furthermore, the polarizer is provided on one side of the Faraday rotator, the optical elements of the analyzer are provided on the other side, the magnet is provided on the outer periphery of the Faraday rotator, and the side surfaces of the optical elements are made of the bonding material. It is joined to the holder.

  Moreover, an optical device manufacturing method in which an optical element is fixed to a fixing surface of a holder, wherein a bonding material made of lead-free low-melting glass is provided on at least one of the fixed surface of the optical element and the fixing surface of the holder. And a bonding step of fixing the optical element to the holder by heating the bonding material at a first temperature increase rate to a firing temperature or higher and then cooling at a first cooling rate. And an annealing step in which the temperature is raised to the firing temperature at a second heating rate faster than the temperature rate and then cooled at a second cooling rate faster than the first cooling rate.

Then, _30~70mol% of SnO as a serial bonding _material, 20 to 50 mol% of P 2 _{O 5,} using the lead-free low-melting-point glass containing 5 to 30 mol% of MnO, that the melting temperature of the bonding material is 400 ° C. or less It is characterized by.

  Further, the Faraday rotator sandwiched between the polarizer on one side and the analyzer on the other side is joined to the holder by the joining material in a reducing atmosphere or a reduced pressure atmosphere.

And while impregnating the bonding material into the holder by ultrasonic vibration,
The method of manufacturing an optical device according to claim 4, wherein each of the polarizer, the analyzer, and the Faraday rotator is joined to a holder.

According to the present invention, the firing temperature of the bonding material is oxidized by using a bonding material made of lead-free low-melting glass containing 30 to 70 mol% of SnO, 20 to 50 mol% of P ₂ O ₅ and ₅ to 30 mol% of MnO. It can be reduced as compared with the case of lead-based low melting glass. Thereby, degradation of an antireflection film can be suppressed at the time of joining, and a more reliable optical device can be provided. Furthermore, since lead is not used for the bonding material, it is possible to provide an optical device that is friendly to the global environment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic cross-sectional view showing an example of the structure of the optical device according to the present embodiment. The optical device includes an optical element 1, a holder 2 that holds the optical element 1, and a low melting point glass 3 that fixes the optical element 1. Here, the antireflection film 4 is formed on the opposing main surface of the optical element 1.

  Although FIG. 1 shows an example in which a cylindrical glass lens is used as the optical element 1, various lenses such as a ball lens, a flat lens, and a square lens may be used depending on the application. Moreover, not only a lens but optical crystals such as an airtight window, a prism, and a polarizer, an optical crystal such as a birefringent glass, and a Faraday rotator can be used. In addition, it is desirable to use a material having a lead content of 0.1% by weight or less as a material for these optical components in order to prevent adverse effects on the environment.

  The holder can be selected according to the thermal expansion coefficient and mechanical strength of the various optical elements 1. Preferably, the material of the holder should be selected according to the method of attaching the optical device of the present invention to another device. In addition to the Fe—Ni alloy, any metal such as stainless steel, copper alloy, brass, aluminum alloy, and various ceramics such as alumina and zirconia can be selected. Preferably, Fe—Ni alloy and stainless steel are used from the viewpoint of bonding strength.

The antireflection film can be a single layer or a multilayer structure, and can be formed of a material such as MgF ₂ , SiO ₂ , Al ₂ O ₃ by a sputtering method, a vacuum evaporation method, or the like. The heat resistance of the antireflection film is 400 ° C. or lower because the bondability with the optical element is deteriorated.

The low melting point glass used in the present invention contains SnO, P ₂ O ₅ and MnO. By adding MnO to the low softening SnO—P ₂ O ₅ glass, firing at a lower temperature is possible compared to the lead oxide system, the firing temperature is lower than 400 ° C., and water resistance is improved and heat is reduced. The expansion coefficient can be reduced. This is because part of MnO is changed to Mn ₂ O ₃ , works as a trivalent cation oxide, and is incorporated into the network structure formed by P ₂ O ₅ , so that the structure becomes stronger, water resistance is improved, and heat is increased. It is thought that it contributes to the reduction of the expansion coefficient. Moreover, the effect which suppresses the valence change of a tin ion can be considered because manganese ion becomes a high oxidation number. As a result, generation of insoluble compounds can be suppressed, and a stable melt can be obtained.

Here, SnO is a component that lowers the melting point of glass, and is 30 to 70 mol%, more preferably 40 to 60 mol%. When SnO is less than 30 mol%, the viscosity of the glass increases and the firing temperature increases, and when it exceeds 70 mol%, it does not vitrify. _Further, P 2 _{O 5} is a component for forming a glass, 20 to 50 mol%, more preferably 30~40mol%. P ₂ O ₅ is not vitrified less than 20 mol%, 50 mol% larger than the mechanical strength and weather resistance is lowered. Further, SnO and _P 2 _{O 5} is combined 70 mol%, and more preferably not less than 80 mol%. If it is less than 70 mol%, the viscosity of the glass is increased and the firing temperature is increased. Moreover, MnO is 5-30 mol%, More preferably, it is 10-20 mol%. This is because if MnO is less than 5 mol%, the mechanical strength becomes insufficient, and if it is more than 30 mol%, vitrification becomes difficult.

The following compounds can be used as starting materials for the production of the lead-free low-melting glass of the present invention. Examples of MnO raw materials include MnO ₂ , MnO, MnCO _{3 and the} like. Among them, MnO ₂ is not so preferable because it tends to generate SnO ₂ that oxidizes SnO to form an insoluble compound (SnP ₂ O ₇ ) with P ₂ O ₅ . MnO is preferable, and MnCO ₃ having a low decomposition temperature is more preferable in consideration of easiness of melting.

In addition, considering the ease of melting as compared with SnO, the SnO raw material may be metastannic acid having a lower decomposition temperature, but it is difficult to produce P ₂ O ₅ and an insoluble compound (SnP ₂ O ₇ ). For this purpose, SnO is more preferable.

In _addition, the raw material of _{P 2 O 5, P 2 O} 5, H 3 PO 4, NH 4 is H 2 PO can be given ₄ or the _like, P 2 _{O 5} is water absorption or _H 3 PO _4, Is not preferable considering that it is a liquid. In contrast, an ammonium salt of phosphoric acid (primary ammonium phosphate: ammonium dihydrogen phosphate (NH ₄ H ₂ PO ₄ ) or secondary ammonium phosphate: diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ) Is a solid, and it is preferable to use these because reductive ammonia gas generated during decomposition can suppress oxidation of SnO (change to SnO ₂ ).

  In addition, although the said raw material single-piece | unit may be mixed for manufacture of a lead-free low melting glass, you may use the various phosphate containing the said composition element. When these are used, volatilization of components during glass production is suppressed, and the composition variation is reduced.

  The container used for melting is not particularly limited, such as metal, quartz, alumina, mullite, carbon. In addition, although there may be a lid of the container used for melting, it is preferable that there is no lid from the viewpoint of promoting the release of cracked gas. The melting atmosphere may be an inert atmosphere, but the atmosphere is preferable in view of the complexity of the manufacturing process.

Furthermore, for the purpose of adjusting the firing temperature, thermal expansion coefficient, crystallization temperature, wettability with various materials, and adhesiveness, the firing temperature is not increased significantly, the water resistance is not significantly decreased, and the thermal expansion coefficient is increased. Within a total range of not more than 10 mol%, alkali metal, alkaline earth metal compound, transition metal compound, trivalent cation oxide such as alumina, iron oxide, gallium oxide, antimony oxide, B ₂ O _3. Additives such as SiO ₂ may be added.

  Here, it is desirable to use an inductively coupled plasma emission spectrometer (ICP emission analysis) for the composition analysis of the low melting point glass used in the present invention. ICP emission analysis is one of the typical inorganic element analyses. Not only can ppb-level high-sensitivity analysis be performed for many elements, but it is also less susceptible to coexisting substances than other analytical methods. Suitable for simultaneous multi-element analysis.

  Next, an example of a method for manufacturing an optical device of the present invention will be described. A bonding material made of lead-free low-melting glass is brought into contact with at least one of the fixed surface of the optical element and the fixing surface of the holder, and then the bonding material is used. A joining step in which the optical element is fixed to the holder by heating at a first temperature increase rate to a firing temperature or higher and then cooling at a first cooling rate, and then a second temperature increase higher than the first temperature increase rate. There is no particular limitation as long as it has an annealing step in which the temperature is raised to the firing temperature at a temperature rate and then cooled at a second cooling rate that is faster than the first cooling rate. In order to obtain the effect of annealing, which will be described later, the second temperature raising rate is at least 3 times, more preferably at least 5 times the first temperature raising rate. Further, the second cooling rate is 6 times or more, more preferably 10 times or more of the first cooling rate. In order to achieve the second cooling rate, for example, a method of blowing an air jet can be used. The low-melting glass is pasted with an organic vehicle that decomposes below the firing temperature and applied to the fixed surface of the optical element and the fixed surface of the holder, and then fired, or after being molded into a predetermined shape by press molding, It can also be arranged and fired at the joint between the optical element and the holder.

  Referring to FIG. 1, the optical element 1 is mounted on a holder 2 and a low-melting glass 3 formed in a ring shape is placed at the joint between the optical element and the holder and placed in a firing furnace capable of temperature control. The temperature is raised to the firing temperature or higher at 5 to 10 ° C./min (first heating rate), held at that temperature for 3 to 30 minutes, and then lowered to room temperature at 20 to 50 ° C./min (first cooling rate). And then remove from the firing furnace. The bonding method is not limited to this, and a paste in which a binder is mixed can be used as the low melting point glass 3. Moreover, not only a baking furnace but a high temperature apparatus with a heater such as a hot plate can be used. The temperature condition is not limited to the above, and can be changed according to the member used and the instrument.

  Next, a second uniform heating rate of 3 times or more of the first heating rate, that is, rapid uniform heating at 30 to 200 ° C./min, and then blowing an air jet to near the firing temperature again, Annealing is performed by quenching at a second cooling rate of 300 to 2000 ° C./min, which is 6 times or more the cooling rate of 1, and applying a compressive stress to the surface of the low melting point glass.

  By applying rapid heating to the low melting point glass, the surface temperature of the low melting point glass becomes higher than the internal temperature. At this time, the stress generated in the low melting point glass is compressed on the surface and pulled on the inside, so there is no risk of destruction of the low melting point glass itself. Next, when the entire low-melting glass reaches the maximum temperature uniformly and then rapidly cools, the surface first has a temperature drop faster than the inside, and the thermal stress is pulled on the surface and the inside is compressed. However, when the low-melting glass is at a high temperature close to the firing temperature, the thermal stress is relaxed in a very short time, and it becomes a stress-free state regardless of the existence of a temperature difference between the surface and the interior. And when the cooling rate is kept constant and the temperature difference between the surface and the interior is kept constant, the low melting point glass drops in temperature without stress, finally reaches room temperature, and when the temperature difference disappears, As the thermal stress caused by the temperature difference at high temperature is relaxed, the low-melting glass has a compressive stress and a tensile stress inside, thereby strengthening the low-melting glass.

According to the present embodiment, by using lead-free low-melting glass containing SnO, P ₂ O ₅ and MnO in a predetermined composition as a bonding material, the firing temperature is lowered as compared with conventional lead oxide-based low-melting glass. Therefore, the antireflection film provided on the optical element is not deteriorated. Thereby, the reliability of the optical device can be improved. In addition, since lead-free low-melting glass is used, an environmentally friendly optical device can be provided.

  The optical device of the present invention is applied not only to the optical element 1 to the holder 2 with the low melting point glass 3, but also to any optical device such as an optical isolator or optical filter composed of a combination of a polarizer and an analyzer. It is possible.

  FIG. 2 is a schematic cross-sectional view showing the structure of the optical device according to the present embodiment. Except that the covering member 5 is provided on the outside air exposed surface of the low melting point glass 3, it has the same structure as that of the first embodiment. The optical device according to the present embodiment has the following effects in addition to the effects of the first embodiment. That is, the covering member 5 can protect the surface of the low-melting glass 3 exposed to the outside air from those that may deteriorate the low-melting glass 3 such as humidity. Thereby, degradation of the optical device in a high humidity environment can be suppressed, and the reliability of the optical characteristics of the optical device can be further improved. This covering member 5 is ring-shaped and, like the holder 2, in addition to Fe—Ni alloy, any metal such as stainless steel, copper alloy, brass, aluminum alloy, and various ceramics such as alumina, zirconia, etc. In addition, it can be formed by a method such as vapor deposition of various metals.

  FIG. 3 is a schematic cross-sectional view showing the structure of an optical isolator which is another embodiment of the optical device according to the present embodiment.

  A Faraday rotator 11, a polarizer 12 on one side of the Faraday rotator 11, an analyzer 13 on the other side, a magnet 14 on the outer periphery of the Faraday rotator 11, a holder 15 for the Faraday rotator 11, and a polarizer 12 for the polarizer 12. The holder 16 and the analyzer 13 are respectively attached to a holder 17, and the holder 16 and the holder 17 are connected by a case 18. The Faraday rotator 11 uses, for example, a Bi-substituted garnet thick film, the polarizer 12 and the analyzer 13 are infrared polarizing glasses (product name: Polar Core), and the holder 16 and the holder 17 are nickel-iron. The low melting point glass of the present invention is used for the alloy, the low melting point glass G2 and G3, the nickel-iron alloy is used for the holder 15, and the low melting point glass of the present invention is used for the low melting point glass G1. The case 18, the holder 16 and the holder 17 are fixed by welding Y1 and Y2 joints with a YAG laser.

The low melting point glass used in the present invention contains SnO, P ₂ O ₅ and MnO. By adding MnO to the low softening SnO—P ₂ O ₅ glass, firing at a lower temperature is possible compared to the lead oxide system, the firing temperature is lower than 400 ° C., and water resistance is improved and heat is reduced. The expansion coefficient can be reduced. This is because part of MnO is changed to Mn ₂ O ₃ , works as a trivalent cation oxide, and is incorporated into the network structure formed by P ₂ O ₅ , so that the structure becomes stronger, water resistance is improved, and heat is increased. It is thought that it contributes to the reduction of the expansion coefficient. Moreover, the effect which suppresses the valence change of a tin ion can be considered because manganese ion becomes a high oxidation number. As a result, generation of insoluble compounds can be suppressed, and a stable melt can be obtained.

  Here, the Faraday rotator 11, the polarizer 12, and the analyzer 13 are brittle materials that are weak against tensile stress, and micro-scratches generated on the surface of the glass break down due to stress concentration even with a slight tensile force. Cause. However, the compressive force, on the other hand, is an advantage of the brittle material but has a very strong characteristic, and since the firing temperature of the low melting point glass of the present invention is lower than 400 ° C., the Faraday rotator 11, Since the polarizer 12 and the analyzer 13 are subjected to compressive force due to the contraction force of the holder, and a low melting point glass exists as a buffer material as an intermediate layer between the Faraday rotator 11, the polarizer 12 and the analyzer 13, The Faraday rotator 11, polarizer 12 and analyzer 13 are not destroyed by the compressive force.

  In some cases, an antireflection film may be formed on the optical surfaces of the Faraday rotator 11, the polarizer 12, and the analyzer 13, and the deterioration of the antireflection film may be suppressed.

Example 1
Hereinafter, the present invention will be described in detail using examples.

As an example, an optical element with an antireflection film is a cylindrical glass lens having an outer diameter of 1.8 mm and a thermal expansion coefficient of 88 × 10 ⁻⁷ / ° C., and a holder is Fe—Ni having a thermal expansion coefficient of 97 × 10 ⁻⁷ / ° C. Optical devices of Samples A to D were prepared using the low melting point glass of the present invention having a firing temperature of 330 to 380 ° C. as the alloy and the low melting point glass.

  As comparative examples, optical devices of Samples E and F were produced by the same method as in the Examples, except that low-melting glass containing lead oxide and having a firing temperature of 450 ° C. and 460 ° C. was used.

As evaluation results, 100 samples of each of the examples and comparative examples were produced, and the reflectance of the antireflection film after production was measured. Next, the sample was put into a constant temperature and humidity test at 85 ° C. and 85%, and the reflectance after 2000 hours was measured and converted into a reflectance fluctuation value from before the introduction. The results are shown in Table 1.

  As shown in Table 1, all the samples (Nos. A to D) using the low-melting glass within the scope of the present invention are suppressed to reflectivity fluctuations of 0.2% or less. In Nos. E and F), about half of the reflectance fluctuations exceeded 0.2%.

  As a result, the optical device of the present invention has less reflectance fluctuation and improved reliability as compared with the conventional optical device.

(Example 2)
Next, a Faraday rotator 11 shown in FIG. 3, a polarizer 12 on one side of the Faraday rotator 11, and an analyzer 13 on the other side, a magnet 14 on the outer periphery of the Faraday rotator 11, and the Faraday rotator 11 are The holder 15 and the polarizer 12 are attached to the holder 16, and the analyzer 13 is attached to the holder 17. The holder 16 and the holder 17 are connected by a case 18.

  The Faraday rotator 11 uses, for example, a Bi-substituted garnet thick film, the polarizer 12 and the analyzer 13 are infrared polarizing glasses (product name: Polar Core), and the holder 16 and the holder 17 are nickel-iron. The low melting point glass of the present invention is used for the alloy, the low melting point glass G2 and G3, the nickel-iron alloy is used for the holder 15, and the low melting point glass of the present invention is used for the low melting point glass G1. The case 18 and the holder 16 and the holder 17 were fixed by creating a sample of an optical isolator in which the joints of Y1 and Y2 were welded with a YAG laser.

  Here, there are two types of low melting point glass, one using the sample C of the above example 1 as an example of the present invention and one using the sample E of the above example 1 as a comparative example. 50 pieces each were produced with a firing temperature of 354 ° C. and 450 ° C.

The generation of cracks in the Faraday rotator 16, polarizer 17 and analyzer 18 of the prepared sample was confirmed with a 100-fold metal microscope. The results are shown in Table 2.

  As described above, in the optical isolator using the sample E of the comparative example, 8 out of 50 cracks could be confirmed, but in the optical isolator using the sample C of the embodiment of the present invention, there was no occurrence of 50 internal cracks. It was.

It is a schematic cross section which shows an example of the structure of the optical device which concerns on Embodiment 1 of this invention. It is a schematic cross section which shows an example of the structure of the optical device which concerns on Embodiment 2 of this invention. It is a schematic cross section which shows an example of the structure of the optical isolator which concerns on Embodiment 1 of this invention. It is a schematic cross section which shows an example of the structure of the conventional optical device.

Explanation of symbols

1: Optical element 2: Holder 3: Bonding material 4: Antireflection film 5: Cover member 11: Faraday rotator 12: Polarizer 13: Analyzer 14: Magnet 15: Holder 16: Holder 17: Holder 18: Case

Claims (7)

An optical device in which an optical element is fixed to a holder by a bonding material,
The bonding material, _30~70mol% of _SnO, 20 to 50 mol% of P 2 _{O 5,} the optical device is a lead-free low-melting-point glass containing 5 to 30 mol% of MnO. The optical device according to claim 1, wherein the total content of SnO and P ₂ O _{5 in} the bonding material is 70 mol% or more. Having a polarizer on one side of the Faraday rotator and an analyzer on the other side,
Having a magnet on the outer periphery of the Faraday rotator,
The optical device according to claim 1, wherein a side surface of each optical element is bonded to the holder by the bonding material. An optical device manufacturing method in which an optical element is fixed to a fixed surface of a holder,
After a bonding material made of lead-free low-melting glass is brought into contact with at least one of the fixed surface of the optical element and the fixing surface of the holder, and then the bonding material is heated to a firing temperature or higher at a first heating rate. A bonding step of cooling at a first cooling rate and fixing the optical element to the holder;
And an annealing step in which the temperature is raised to the firing temperature at a second heating rate faster than the first heating rate and then cooled at a second cooling rate faster than the first cooling rate. Production method. SnO and _{30~70mol%, 20~50mol%} of P 2 _{O 5,} the lead-free low-melting-point glass containing MnO 5 to 30 mol% used as the bonding material,
The method for manufacturing an optical device according to claim 4, wherein the melting temperature of the bonding material is 400 ° C. or less. 6. The Faraday rotator sandwiched by a polarizer on one side and an analyzer on the other side is joined to the holder by the joining material in a reducing atmosphere or a reduced pressure atmosphere. Optical device manufacturing method. While impregnating the bonding material into the holder by ultrasonic vibration,
The method of manufacturing an optical device according to claim 4, wherein each of the polarizer, the analyzer, and the Faraday rotator is joined to a holder.

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