JP3863597B2 - Optical component and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical component in which two or more optical elements are fixed, such as an isolator in which a polarizer, an analyzer, and a Faraday rotator are fixed to each other, and a method for manufacturing the same.
[0002]
[Prior art]
As a conventional optical element fixing method, a method of fixing a constituent element to a holder using an organic adhesive as described in JP-A-3-171029, and a Sn63 weight as described in JP-A-3-35213. Metal for fixing each component to the holder using eutectic alloy solder of% -Pb 37% by weight, or using solder of Au 80% by weight-Sn 20% by weight as described in JP-A-6-230314 There is a bonding method and a method of using both fixing of an element with an adhesive and fixing to a holder with solder.
JP-A-3-171029 discloses an optical isolator in which a polarizer, an analyzer, and a Faraday rotator are bonded with an organic adhesive. The fixing method using an organic adhesive has an advantage that productivity is remarkably improved because a large number of elements can be obtained by bonding a large-area polarizer, analyzer and Faraday rotator. However, there is a problem in reliability due to deterioration of fixing strength due to aging of the adhesive.
[0003]
On the other hand, Japanese Patent Laid-Open No. 3-35213 discloses an optical isolator in which a polarizer, a Faraday rotator, and a permanent magnet are fixed by fusion of Sn—Pb solder. This fixing method is said to be superior in long-term reliability compared to fixing using an organic adhesive, but it has low fatigue characteristics and creep characteristics, which are said to be caused by solder grain growth, and can be used for fixing optical elements. It is difficult to obtain sufficient strength reliability.
Further, JP-A-6-230314 describes an optical isolator in which each element is fixed to a holder with Au—Sn solder. Similarly, this technique is effective in preventing the deterioration of insertion loss after the heat cycle test of the optical isolator, in addition to the improvement in the adhesive strength between the elements and the reliability of the optical component. Since the solder is very expensive, the matching of the thermal expansion coefficient between the element and the bonding holder material and the bonding method is a method of heating the solder in an N ₂ inert gas atmosphere and an N ₂ + H ₂ mixed gas atmosphere. In addition, there is a problem that the running cost is expensive.
[0004]
Japanese Patent Application Laid-Open No. 5-232418 discloses an optical isolator in which two birefringent elements are fixed with an adhesive and then fixed to a holder with solder. In this method, workability and productivity are improved by using an adhesive, but there are problems with deterioration of the adhesive between optical elements and reliability of solder joint strength depending on the solder used. The present invention relates to an improvement of this scheme.
[0005]
[Problems to be solved by the invention]
In the optical industry, which is expected to expand further in the future, it is necessary to develop various optical components at low prices, and simplification of the component structure and manufacturing process is an important issue.
Therefore, the present invention is based on (1) after performing relative alignment of crystal orientations of each optical element having a large area, and then bonding these optical elements with an organic adhesive and cutting them into individual optical components. Introducing a multi-cavity process that stabilizes quality and reduces manufacturing costs, and (2) a plurality of optical elements bonded with an organic adhesive are bonded to a holder by using solder fusion. A method for facilitating the control of the joining operation and the joining position is adopted.
In this case, when an optical component is manufactured by the steps (1) and (2), the heat used in the soldering step (2) does not deteriorate the organic adhesive used in the step (1). It is necessary to perform joining by heating work.
[0006]
However, the solder of Au 80 wt% -Sn 20 wt%, which is often used for joining optical components in the past, requires a working temperature of about 300 to 320 ° C. because the melting point is 280 ° C. However, since the organic adhesive deteriorates at this working temperature, it is difficult to use the organic adhesive for joining optical elements.
Solder typified by Sn—Pb eutectic solder used for general electronic parts and the like has a low melting point and can be bonded at an operating temperature in a range where the organic adhesive does not deteriorate. However, this type of low-melting-point solder is inferior in long-term reliability of fixing strength when used for fixing optical elements, and may be deformed by external force due to the softness of the material. There is a possibility that problems such as deterioration of characteristics may occur due to the shaft misalignment.
The object of the present invention is to adhere (fuse) at a temperature lower than the heat-resistant temperature of the organic adhesive for adhering each optical element, and to fix the fixing strength between the holder and the optical element and to improve the long-term reliability of the optical characteristics. To provide an optical component in which a holder and an optical element are integrated.
[0007]
[Means for Solving the Problems]
The optical component of the present invention is an optical component in which a plurality of optical elements are fixed to a holder, the plurality of optical elements are fixed to each other with an organic adhesive, and the plurality of optical elements are Sn--to the holder. It is preferably fixed at a solder thickness of 3 to 40 μm with an Ag-based solder (typically an alloy composed of 96.5 wt% tin and 3.5 wt% silver and an alloy described below). .
In the method of manufacturing an optical component according to the present invention, a plurality of optical elements are fixed to each other with an organic adhesive and then cut to a predetermined size, and a holder is made of Sn-Ag solder, preferably 3 to 40 μm solder. It is characterized by being fused by thickness.
[0008]
The holder is not particularly limited as long as it is made of a material having heat resistance that can withstand solder fusion, but it has little rusting and has heat resistance, austenitic stainless steel (represented by SUS304 type). And non-magnetic), ferritic stainless steel (represented by SUS430 and ferromagnetic), Kovar, Invar, Permalloy and the like are preferable.
[0009]
The optical element is a Faraday rotator made of magnetic garnet (oxide), a rutile plate, a polarizer or analyzer made of polarizing glass (oxide), a lens made of optical glass, etc., but is not necessarily an optical isolator. It is not limited to the combination of the optical elements which comprise.
[0010]
As the organic adhesive, a thermosetting epoxy resin having a high heat resistance and high adhesive strength is usually used. However, the present invention is not limited to this as long as the heat resistance and adhesive strength are equal to or higher than these.
[0011]
Sn-Ag solder is used for bonding the optical element and the holder. The alloy of 96.5 wt% Sn and 3.5 wt% Ag, which is an eutectic composition, is preferably used because it has a low melting point and is easily available. A composition shifted from the eutectic composition within a range of about ± 3% can also be used. Furthermore, an additive that increases the mechanical strength of the solder, such as Bi, Cu, Sb, In or the like (preferably Cu or Cu-In) can be included. When the additive is contained, the stability against the thermal shock cycle is increased, and the initial fixing position and angle are stably maintained. These additives are preferably contained at a ratio of about 3% or less so as not to raise the solder melting point. In addition, you may contain a very small amount of another element as an impurity.
Further, the thickness of the solder is preferably thick in order to relieve the stress at the joint, but is preferably set in the range of 3 to 40 μm in consideration of fluctuations in adhesive strength and insertion loss. If the thickness is smaller than this range, the coupling strength is lowered, and if it is thicker than this range, the variation in insertion loss, which is considered to be caused by the variation in the angle between the soldered optical elements, becomes large.
[0012]
When fixing using Sn-Ag solder, a metallized film is deposited in advance on the part of the optical element and the holder where the solder is fused by vapor deposition or sputtering in order to improve the wettability of the solder. It is preferable to keep it.
For example, in order to enable soldering of one optical element on the side in contact with the holder, a metallization process is performed in a predetermined pattern, and the other optical element is bonded to the opposite surface subjected to the metallization process using an organic adhesive. It is fixed to one functional optical element, and the bonded element is cut to a specified size along the metallized pattern. Using the above elements, the metallized surface is fused to the holder using Sn-Ag solder.
[0013]
[Action]
When the elements are bonded to each other using an epoxy-based resin, when heated to 300 ° C. or higher, spots of the adhesive layer and the like are generated. It is necessary to use melting point solder. In the present invention, the optical element is fused to the holder using Sn—Ag solder having a melting point of 221 ° C. and excellent creep resistance. In this case, a temperature higher by about 40 ° C. than the solder melting point is temporarily applied to the optical element by solder fusion, but since this temperature is lower than the heat resistant temperature of the organic adhesive, the adhesive between the optical elements deteriorates. There is nothing. Therefore, when manufacturing one optical component, long-term reliability of the fixing strength between the holder optical elements when the optical elements are fixed to the holder by soldering after bonding a plurality of optical elements with an organic adhesive. It is possible to obtain an optical component that is excellent in characteristics and has little characteristic deterioration due to optical axis deviation.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
The method of the present invention will be described with reference to FIG. FIG. 9 shows an optical component formed by fixing an optical element to a holder according to the present invention.
First, optical elements 1, 2, and 3 (for example, 1 is an analyzer, 2 is a magnetic garnet plate for a Faraday rotator, and 3 is a polarizer) to be configured as a functional optical element (for example, an isolator) are bonded to a holder 9 A metallized layer 6 is formed on the outer surface of the outermost optical element 3 to be metallized by vapor deposition of a metal as described in the embodiment.
Next, the optical elements 1, 2, and 3 are laminated by thermosetting and heat-resistant organic adhesives 4 and 5 such as epoxy resin and bonded together.
Further, the metallized layer 6 of the optical element 3 of the outermost layer of the laminated body is formed of a stainless steel holder 9 having an opening for forming an optical path portion 10 constituting the optical path portion using the Sn-Ag solder 7 of the present invention. Solder to the surface by reflow soldering. The holder 9 is preferably provided with a metallized layer 8.
[0015]
【Example】
Specific examples of the present invention will be described below.
Example 1
Using a 10mm x 10mm x 1.0mm rutile plate, masking the part where light passes, and depositing Cr, Ni, and Au films in order from the bottom so that the solder is easily wet only in the part where the solder is fused. Thus, a metallized film was formed.
In addition to this metallized rutile plate (polarizer) of 10 mm × 10 mm × 1.0 mm, a 10 mm × 10 mm × 0.4 mm magnetic garnet (Faraday rotator) and a 10 mm × 10 mm × 1.0 mm rutile plate ( (Analyzer) was prepared, the relative angle of the crystal orientation of the rutile plate was adjusted to a predetermined angle, and then the epoxy resin was applied to the entire bonding surface in this order and bonded together.
At this time, the thermosetting condition of the epoxy resin adhesive was maintained at 100 ° C. for 4 hours. After thermosetting, after cooling to room temperature, the bonded optical element was cut into 1.0 × 1.3 mm to obtain an optical element chip.
Next, SUS304 stainless steel (a kind of austenitic stainless steel) constituting the holder for fixing the optical element chip is formed with an opening through which light passes, and Cr, Ni, Then, an Au film was deposited to form a metallized film.
A Sn-Ag eutectic solder foil composed of 96.5% by weight of Sn and 3.5% by weight of Ag is sandwiched between the holder and the portion of the optical element chip where the solder is fused. It put into the reflow furnace set so that the maximum heating temperature might be 260 degree | times, and soldered it.
By cooling this and fixing the magnet, an optical isolator, one of the optical components, was completed. At this time, the thickness of the solder layer was 30 to 40 μm.
[0016]
Next, as an accelerated test for evaluating long-term reliability, a thermal cycle test was conducted to examine the fixing strength between the holder and the optical element fusion interface.
The test conditions were n = 20, and thermal shock (1 cycle 1 hour) with a temperature difference from −40 ° C. to 85 ° C. was performed 500, 1000, 1500, 2000 times and compared with the value before the test. The results are shown in FIG.
As a result, it can be seen that an adhesive strength of 1 kgf / mm ^{2 having} no practical problem can be obtained even after 2000 cycles.
[0017]
In the same way, after producing an optical isolator in which only the thickness of the solder layer at the joint between the optical element and the holder is changed in the range of 10 μm to 100 μm, optical fibers are coupled to both ends, and temperatures of −40 ° C. and 85 ° C. The insertion loss was investigated by putting it in a test tank of the difference thermal shock (1 cycle 1 hour). The results are shown in FIGS. For comparison, FIG. 4 shows the insertion loss of the both-end optical fiber coupling system without an optical element.
From the above results, if the thickness of the solder layer exceeds 40 μm, the variation in insertion loss after the thermal cycle test becomes large, and if it is less than 3 μm, the soldering surface becomes non-uniform and the adhesive strength decreases. The thickness is preferably in the range of 3 to 40 μm.
[0018]
Comparative Example 1
Instead of using the Sn—Ag eutectic solder of Example 1, Sn—Pb solder composed of 63 wt% Sn and 37 wt% Pb was used, and the maximum heating temperature of the reflow furnace was set to 230 ° C. Produced an optical isolator in the same manner as in Example 1, and conducted the same thermal cycle test as in Example 1. The results are shown in FIG.
As a result, a solder fixing strength of about 0 kgf / mm ² already occurs after 500 cycles. The cause is thought to be due to solder grain growth and fatigue.
[0019]
Comparative Example 2
Instead of using the Sn—Ag eutectic solder of Example 1, Sn—Bi—Pb solder composed of 60 wt% Sn, 3 wt% Bi and 37 wt% Pb (addition of Bi is a strength deterioration caused by solder grain growth) The optical isolator is manufactured in the same manner as in Example 1 except that the maximum heating temperature of the reflow furnace is set to 230 ° C. A thermal cycle test was conducted. The results are shown in FIG.
As a result, a solder fixing strength of about 0 kgf / mm ² already occurs after 2000 cycles and cannot be put to practical use.
[0020]
Example 2
The variation in insertion loss due to changes in solder over time was examined in detail below.
The variation in the insertion loss of the modularized element is considered to be due to the angle shift of the element fixed by soldering (the element moves), so a temperature cycle test of the element fixing angle change was performed using an autocollimator.
The element used was an element cut after bonding a rutile plate (polarizer), magnetic garnet, and rutile plate (analyzer) as in Example 1.
Solder used is 1) Sn 96.5 wt% and Ag 3.5 wt%, 2) Sn 95.75 wt%, Ag 3.5 wt% and Cu 0.75 wt%, 3) Sn 93 wt%, Ag 4 wt%, Cu 1.5 Three kinds of solders of wt% and In 1.5 wt% were used. The solder thickness was about 15 μm.
SUS304Se stainless steel (thermal expansion coefficient 180 × 10 ⁻⁷ / ° C.) and SUS430F stainless steel (a kind of ferritic stainless steel, thermal expansion coefficient 104 × 10 ⁻⁷ / ° C.) were used as the material for the element bonding holder member.
The test results are shown in FIG. From this figure, it can be seen that when the material of the solder bonding surface of the optical element is rutile, the combination of used solder Sn95.75 / Ag3.5 / Cu0.75 and SUS430F stainless steel is optimal.
[0021]
In addition, although the Example demonstrated the optical isolator fixed with an organic adhesive in order of a polarizer, a magneto-optical element (magnetic garnet), and an analyzer, other optical components (for example, a polarizer, an electro-optical element, an analyzer) It is obvious that the same effect can be obtained with a light modulator or the like that is fixed with an organic adhesive in this order.
[0022]
【The invention's effect】
As is clear from the above, according to the present invention, in an optical component in which a plurality of optical elements are bonded together using an organic adhesive, and the combined optical elements are fixed to the holder by soldering, the change over time The strength deterioration between the optical element and the holder due to can be prevented.
Therefore, this optical component has a large number of optical elements aligned at a time by aligning the optical axes of a plurality of optical elements at the time of manufacture, bonding them with an organic adhesive, and cutting them to a predetermined size. The conventional method of obtaining the optical chip is adopted, and at the same time, Sn-Ag solder is used for fixing to the holder, so that an optical component having higher reliability in terms of mechanical loss and insertion loss than before is obtained. Can do.
Furthermore, according to the present invention, variation in insertion loss due to changes over time can be reduced by suppressing the thickness of the solder for joining the optical element to the holder within a small range.
[Brief description of the drawings]
FIG. 1 is a graph showing solder fixing strength between an optical element and a holder in an optical component according to the present invention.
FIG. 2 is a graph showing solder fixing strength of an optical element and a holder in an optical component according to a comparative example.
FIG. 3 is a graph showing solder fixing strength between an optical element and a holder in an optical component according to a comparative example.
FIG. 4 is a graph showing the relationship between the number of thermal shock cycles and insertion loss in the case of no element.
FIG. 5 is a graph showing the relationship between the number of thermal shock cycles and the insertion loss when the solder thickness is 80 to 100 μm in the optical component having the structure of the present invention.
FIG. 6 is a graph showing the relationship between the number of thermal shock cycles and the insertion loss when the solder thickness is 50 to 60 μm in the optical component having the structure of the present invention.
FIG. 7 is a graph showing the relationship between the number of thermal shock cycles and the insertion loss when the solder thickness is 30 to 40 μm in the optical component having the structure of the present invention.
FIG. 8 is a graph showing the relationship between the number of thermal shock cycles and the insertion loss when the solder thickness is 10 to 20 μm in the optical component having the structure of the present invention.
FIG. 9 is a schematic view showing the structure of the optical component of the present invention.
10 is a graph showing a change of a fixed angle of the optical element of Example 2 with respect to a temperature cycle. FIG.
[Explanation of symbols]
1, 2, 3 Optical element 4, 5 Organic adhesive 6, 8 Metallized layer 7 Sn-Ag solder layer 9 Holder 10 Optical path portion

Claims (10)

In an optical component in which a plurality of optical elements are fixed to a holder, the plurality of optical elements are fixed to each other with an organic adhesive, and the plurality of optical elements are fixed to the holder with Sn-Ag solder. Optical component characterized by being made. The optical component according to claim 1, wherein the Sn—Ag solder is an Sn—Ag alloy or an Sn—Ag alloy to which Cu or Cu—In is added. 3. The optical component according to claim 1, wherein the solder is an alloy made of 96.5 wt% tin and 3.5 wt% silver. The optical component according to claim 1, wherein the solder has a thickness of 3 to 40 μm. 5. The optical component according to claim 1, wherein the solder-fixed surface of the holder is made of ferritic stainless steel, and the optical-fixed surface of the optical element is rutile. In an optical component in which a plurality of optical elements are fixed to a holder, the plurality of optical elements are fixed to each other with an organic adhesive, and then cut to a predetermined size and fixed to the holder with Sn-Ag solder. An optical component manufacturing method characterized by the above. The manufacturing method according to claim 6, wherein the Sn-Ag solder is an Sn-Ag alloy or an alloy obtained by adding Cu or Cu-In to an Sn-Ag alloy. The method of manufacturing an optical component according to claim 6, wherein the solder is made of 96.5 wt% tin and 3.5 wt% silver. The method for manufacturing an optical component according to claim 6, wherein the solder has a thickness of 3 to 40 μm. The method of manufacturing an optical component according to claim 6, wherein a material of the surface of the holder to which the solder is fixed is ferritic stainless steel, and a material of the surface of the optical element to which the solder is fixed is rutile.

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