JPH0980285A - Optical component and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture an optical component excellent in strength of fixation of the optical elements to the holder and in long term reliability of the optical characteristics by fixing plural optical elements which are fixed to each other with organic adhesives, to a holder with an Sn-Ag based solder. SOLUTION: In this manufacture, a functional optical device such as isolator consists of optical elements such as an analyzer 1, a magnetic garnet plate 2 for a Faraday rotator and a polarizer 3. Of these constituent optical elements of the device, the optical element 3 which is to be the outermost part of the device and to be joined to a holder 9, is provided with a metallization layer 6 formed on the outer surface of the element 3. Then, the optical elements 1 to 3 are successively laminated with thermosetting, heat resistant organic adhesives 4 and 5 such as epoxy resins to join them to each other. Further, the metallization layer 6 of the optical element 3, that is the outermost layer of the resulting laminate, is soldered to the surface of the stainless steel holder 9 having an opening for forming a constituent optical path part 10 of an optical path section with an Sn-Ag based solder 7 by a reflow soldering method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical component having two or more optical elements fixed, such as an isolator having a polarizer, an analyzer and a Faraday rotator fixed to each other, and a method for manufacturing the same. .

[0002]

2. Description of the Related Art As a conventional optical element fixing method, a method of fixing a constituent element to a holder by using an organic adhesive as described in JP-A-3-171029, and JP-A-3-171029.
-Sn 63 wt% as described in 35213-
A eutectic alloy solder containing 37% by weight of Pb is used, or Au80 is used as described in JP-A-6-230314.
There is a metal joining method of fixing each constituent element to the holder using solder of 20% by weight to 20% by weight, and a method of using both the fixing of the element with an adhesive and the fixing to the holder with solder. The above-mentioned JP-A-3-171029 discloses an optical isolator in which a polarizer, an analyzer and a Faraday rotator are bonded together with an organic adhesive. The fixing method using the organic adhesive has an advantage that a large number of devices can be obtained by bonding a large-area polarizer, an analyzer and a Faraday rotator and then cutting them, thereby significantly improving the productivity. But,
There is a problem in reliability due to deterioration of the fixing strength due to aging of the adhesive.

On the other hand, JP-A-3-35213 discloses an optical isolator in which a polarizer, a Faraday rotator and a permanent magnet are fixed by fusing Sn—Pb solder. It is said that this fixing method is superior in long-term reliability 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 is suitable for fixing optical elements. It is difficult to obtain sufficient strength reliability. Furthermore,
Japanese Unexamined Patent Publication No. 6-230314 describes an optical isolator in which each element is fixed to a holder with Au-Sn solder. This technique is also effective to prevent the insertion loss from being deteriorated after the heat cycle test of the optical isolator in addition to the improvement of the adhesive strength between the elements and the reliability of the optical component, and the Au-Sn. The solder is very expensive, and the matching of the thermal expansion coefficient between the element and the bonding holder material and the bonding method are N ₂ inert gas atmosphere and N ₂ + H ₂
Since this is a method of heating the solder in a mixed gas atmosphere, there is a problem that the equipment and running costs are high.

Japanese Patent 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, the workability and the productivity are improved by using the adhesive, but there are problems in the adhesive deterioration between the optical elements and the reliability of the solder joint strength depending on the solder used. The present invention relates to an improvement of this system.

[0005]

In the optical industry, which is expected to further expand in the future, it is necessary to develop various optical parts to reduce the cost, and it is important to simplify the parts structure and the manufacturing process. It is an issue. Therefore, the present invention provides (1) after performing relative alignment of crystal orientations of optical elements having a large area,
The quality is stabilized and the manufacturing cost is reduced by introducing a multi-cavity process in which these optical elements are bonded together with an organic adhesive and cut into individual optical components. (2) A method of facilitating the bonding work with the holder and the control of the bonding position of the plurality of optical elements bonded by the organic adhesive by using solder fusion is adopted. In this case, when the optical component is manufactured by the steps (1) and (2), the heat used in the soldering step of the step (2) does not deteriorate the organic adhesive used in the step (1). It is necessary to perform the joining by the heating work of.

However, since the solder of Au 80% by weight-Sn 20% by weight, which is often used for joining optical components in the related art, has a melting point of 280 ° C., a working temperature of about 300 to 320 ° C. is required. However, it is difficult to use the organic adhesive for joining the optical elements because the organic adhesive deteriorates at this working temperature. Solder typified by Sn—Pb eutectic solder used for general electronic components has a low melting point and can be bonded at a working 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 for use in fixing an optical element, and may be deformed by an external force because the material is soft,
In an optical coupling system of optical components, there is a possibility that a problem such as deterioration of characteristics may occur due to optical axis shift. An object of the present invention is to provide a method capable of bonding (fusing) at a temperature not higher than the heat-resistant temperature of an organic adhesive for bonding each optical element, and having excellent long-term reliability of fixing strength and optical characteristics between a holder and an optical element. An object is to provide an optical component in which a holder and an optical element are integrated.

[0007]

The optical component of the present invention is an optical component in which a plurality of optical elements are fixed to a holder, wherein the plurality of optical elements are fixed to each other with an organic adhesive and the plurality of optical elements are fixed. S the element to the holder
n-Ag solder (typically 96.5 wt% tin and 3.
An alloy composed of 5 wt% of silver and an alloy described below) are preferably fixed with a solder thickness of 3 to 40 μm. In the method for manufacturing an optical component of the present invention, a plurality of optical elements are fixed to each other by an organic adhesive and then cut into a predetermined size, and the holder is Sn-Ag solder, preferably 3 to 40 μm. It is characterized in that the thickness is fused.

The holder is not particularly limited as long as it is made of a heat-resistant material that can withstand solder fusion, but it is austenitic stainless steel (typically represented by SUS304 system) that has little rust and has heat resistance. Used for non-magnetic, ferritic stainless steel (SUS
430 system represented by ferromagnetism), Kovar, Invar, Permalloy and the like are preferable.

Optical element means magnetic garnet (oxide)
A Faraday rotator, a rutile plate, or a polarizer or analyzer made of polarizing glass (oxide), a lens made of optical glass, or the like, but is not necessarily limited to a combination of optical elements forming an optical isolator. Not a thing.

As the organic adhesive, a thermosetting epoxy resin-based adhesive having high heat resistance and high adhesive strength is usually used. However, it is not limited to this as long as it has heat resistance and adhesive strength equal to or higher than these.

Sn-A is used to bond the optical element and the holder.
g-based solder is used. Eutectic composition 96.5 wt% S
Since alloys of n and 3.5 wt% Ag have low melting points and are easily available, it is preferable to use them. A composition deviated from the eutectic composition within a range of about ± 3% can also be used. Further, additives such as Bi, Cu, Sb, In, etc. (preferably Cu or Cu—In) that increase the mechanical strength of the solder can be included. The inclusion of the additive increases the stability against thermal shock cycling and maintains a stable initial fixed position and angle. These additives are preferably contained in a proportion of about 3% or less, which does not increase the solder melting point. Note that an extremely small amount of another element may be contained as an impurity. Further, the thickness of the solder is preferably thick in order to relieve the stress at the joint portion, but it is preferably set in the range of 3 to 40 μm in consideration of the fluctuation of the adhesive strength and the insertion loss. If the thickness is less than this range, the bonding strength will decrease, and if the thickness is more than this range, the fluctuation of the insertion loss, which is considered to be caused by the fluctuation of the angle between the soldered optical elements, increases.

When the Sn-Ag type solder is used for fixing, a metallized film is previously vapor-deposited or sputtered on the portion of the optical element and the holder where the solder is fused to improve the wettability of the solder. It is preferable to attach it at. For example, one of the optical elements on the side in contact with the holder has been metallized in a predetermined pattern to enable soldering, and the other optical element is bonded to the opposite surface that has been metallized using an organic adhesive. It is fixed to form a single functional optical element, and the adhered element is cut along the metallized pattern to a specified size. Using the above elements, the metallized surface is fused to a holder using Sn—Ag solder.

[0013]

[Function] When the elements are bonded together by using the epoxy resin, if they are heated to 300 ° C. or higher, stains or the like of the adhesive layer will occur. It is necessary to use a solder having a melting point lower than that of the solder. In the present invention, the optical element is fused to the holder by 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 melting point of the solder is temporarily applied to the optical element by the solder fusion, but this temperature is lower than the heat resistant temperature of the organic adhesive, so that the adhesive between the optical elements deteriorates. Never. Therefore, in the case of manufacturing one optical component, when the optical elements are fixed to the holder by solder fusion after bonding the multiple optical elements with the organic adhesive, the long-term reliability of the fixing strength between the holder optical elements It is possible to obtain an optical component which is excellent in characteristics and has little characteristic deterioration due to the optical axis shift.

[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 in which an optical element is fixed to a holder according to the present invention. First, one of the 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) that should constitute a functional optical element (for example, an isolator) is 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 examples.
Next, the optical elements 1, 2 and 3 are laminated with thermosetting and heat resistant organic adhesives 4 and 5 such as epoxy resin and bonded to each other. Further, the metallized layer 6 of the optical element 3 which is the outermost layer of the laminated body is formed by using the Sn—Ag solder 7 of the present invention. Solder on the surface by reflow soldering method. It is preferable that the holder 9 is also provided with the metallized layer 8.

[0015]

EXAMPLES Specific examples of the present invention will be described below. Example 1 A rutile plate having a size of 10 mm × 10 mm × 1.0 mm was used, a mask was applied to a portion through which light passed, and Cr, Ni, and Au were sequentially arranged from the bottom so that the solder was easily wetted only in a portion to be fused with solder.
The film was vapor-deposited to form a metallized film. 10 mm x 10
In addition to this metallized rutile plate (polarizer) of mm x 1.0 mm, a magnetic garnet (Faraday rotator) of 10 mm x 10 mm x 0.4 mm and 10 mm x 10 mm
A rutile plate (analyzer) having a size of 1.0 mm was prepared, and the relative angle of the crystal orientation of the rutile plate was adjusted to a predetermined angle, and then the whole bonding surface was coated with an epoxy resin and bonded. At this time, the thermosetting condition of the epoxy resin adhesive is 10
It was kept at 0 ° C. for 4 hours. After heat-curing and cooling to room temperature, the laminated optical element was 1.0 x 1.3 m.
It cut | disconnected to m and obtained the optical element chip. Next, SUS304 forming a holder for fixing the optical element chip
Stainless steel (a type of austenitic stainless steel)
A metallized film was formed by sequentially depositing Cr, Ni, and Au films from the bottom to a substrate having an opening through which light passes so that the solder is easily wetted. 96.5% by weight of Sn and 3.5 was added to the solder-bonded portion of the holder and the optical element chip.
A foil of Sn-Ag eutectic solder composed of Ag by weight was sandwiched, and the foil was placed in a reflow furnace set to a maximum heating temperature of 260 ° C. in the atmosphere to fuse the solder. By cooling this and fixing the magnet, an optical isolator, which is one of the optical components, was completed. At this time, the thickness of the solder layer was 30 to 40 μm.

Next, as an accelerated test for evaluating long-term reliability, a thermal cycle test was conducted to examine the fixing strength of the fusion interface between the holder and the optical element. The test conditions were n = 20, and the thermal shock (1 cycle 1 hour) of the temperature difference from -40 ° C to 85 ° C was 500, 1000, 1500, 2000.
It was repeated and compared with the value before the test. The results are shown in FIG. As a result, 1k, which is practically no problem even after 2000 cycles
It can be seen that an adhesive strength of gf / mm ² is obtained.

In the same manner, 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 within the range of 10 μm to 100 μm, optical fibers are coupled to both ends, and the optical isolator is at −40 ° C. and 85 Insertion loss was investigated by placing the test tank in a thermal shock (1 cycle, 1 hour) with a temperature difference of ° C. The results are shown in FIGS. For comparison, FIG. 4 shows the insertion loss of the both-end optical fiber coupling system without the optical element. From the above results, when the thickness of the solder layer exceeds 40 μm, the fluctuation of the insertion loss after the thermal cycle test becomes large, and 3
If the thickness is less than μm, the soldering surface becomes non-uniform and the adhesive strength decreases, so the thickness of the solder layer is preferably in the range of 3 to 40 μm.

Comparative Example 1 Instead of using the Sn—Ag eutectic solder of Example 1, 63
An optical isolator was prepared and implemented in the same manner as in Example 1 except that Sn-Pb solder composed of wt% Sn and 37 wt% Pb was used and the maximum heating temperature of the reflow furnace was set to 230 ° C. The same thermal cycle test as in Example 1 was performed. The results are shown in FIG. As a result, solder fixing strength of about 0 kgf / mm ² is already generated after 500 cycles. The cause is considered to be due to solder grain growth and fatigue.

Comparative Example 2 Instead of using the Sn—Ag eutectic solder of Example 1, 60
S consisting of wt% Sn, 3 wt% Bi and 37 wt% Pb
n-Bi-Pb solder (addition of Bi is known to prevent strength deterioration due to solder grain growth) was used, except that the maximum heating temperature of the reflow furnace was set to 230 ° C. An optical isolator was manufactured in the same manner as in Example 1, and the same thermal cycle test as in Example 1 was performed. The results are shown in FIG. As a result, after 2000 cycles, a solder fixing strength of about 0 kgf / mm ² is already generated, which cannot be put to practical use.

Example 2 The variation of the insertion loss due to the change with time of the solder was examined in detail below. Since it is considered that the variation in the insertion loss of the modularized element is due to the angle deviation of the element fixed by solder (the element moves), the temperature cycle test of the change in the element fixing angle was performed using an autocollimator. The element used is a rutile plate (polarizer) as in Example 1,
The element was a magnetic garnet and a rutile plate (analyzer) that were cut after bonding. 1) Sn 96.5% by weight and Ag 3.5% by weight, 2) Sn 95.75% by weight, Ag
3.5% by weight and 0.75% by weight Cu, 3) 93% by weight Sn, 4% by weight Ag, 1.5% by weight Cu and In1.5
Weight% of three types of solder was used. Solder thickness is about 15 for each
μm. The material of the element joint holder member is SUS3
04Se stainless steel (coefficient of thermal expansion 180 × 10 ^-7 /
C.) and SUS430F stainless steel (a type of ferritic stainless steel having a thermal expansion coefficient of 104.times.10.sup.- ⁷ / .degree. C.). The test results are shown in FIG. From this figure, when the material of the solder bonding surface of the optical element is rutile, the solder Sn used
95.75 / Ag3.5 / Cu0.75 and SUS43
It can be seen that the combination of 0F stainless steel is optimal.

In the embodiment, the optical isolator in which the polarizer, the magnetic optical element (magnetic garnet) and the analyzer are fixed in this order with the organic adhesive has been described, but other optical components (for example, the polarizer and the electro-optical element). It is self-evident that the same effect can be obtained by an optical modulator in which the analyzer is fixed in this order with an organic adhesive.

[0022]

As is apparent from the above, according to the present invention, after bonding a plurality of optical elements using an organic adhesive, an optical element in which the bonded optical elements are fixed to a holder by solder fusion is used. Optical elements due to aging in parts
It is possible to prevent strength deterioration between holders. Therefore, in this optical component, a plurality of optical elements having a large area are aligned at the time of manufacture, then they are bonded with an organic adhesive and cut into a predetermined size, so that a large number of optical elements with uniform optical characteristics can be obtained at one time. The conventional method of obtaining an optical chip is adopted, and at the same time, Sn-Ag solder is used for fixing to the holder, so that it is possible to obtain an optical component that is more reliable mechanically and in terms of insertion loss than before. You can Further, according to the present invention, by suppressing the thickness of the solder for bonding the optical element to the holder within a small range, it is possible to reduce the variation in insertion loss due to aging.

[Brief description of 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 between 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 the 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 diagram showing the structure of the optical component of the present invention.

FIG. 10 is a graph showing changes in the fixed angle of the optical element of Example 2 with respect to temperature cycles.

[Explanation of symbols]

 1, 2, 3 Optical element 4, 5 Organic adhesive 6, 8 Metallization layer 7 Sn-Ag solder layer 9 Holder 10 Optical path part

Claims (10)

[Claims] 1. An optical component in which a plurality of optical elements are fixed to a holder, wherein the plurality of optical elements are fixed to each other with an organic adhesive, and the plurality of optical elements are Sn- with respect to the holder. An optical component characterized by being fixed with Ag-based solder. 2. The optical component according to claim 1, wherein the Sn—Ag based solder is a Sn—Ag alloy or a Sn—Ag alloy to which Cu or Cu—In is added. 3. The solder is 96.5 wt% tin and 3.
The optical component according to claim 1 or 2, which is an alloy composed of 5% by weight of silver. 4. The optical component according to claim 1, wherein the solder has a film thickness of 3 to 40 μm. 5. The material of the solder-fixed surface of the holder is ferritic stainless steel, and the material of the solder-fixed surface of the optical element is rutile.
Any of the optical components. 6. An optical component comprising a holder and a plurality of optical elements fixed to the holder, the plurality of optical elements being fixed to each other by an organic adhesive, and cut into a predetermined size, and then Sn-Ag is attached to the holder. A method for manufacturing an optical component, which comprises fixing with a system solder. 7. The Sn-Ag solder is Sn-Ag alloy, S
The method according to claim 6, which is an alloy obtained by adding Cu or Cu-In to an n-Ag alloy. 8. The solder comprises 96.5% by weight tin and 3.
The method for manufacturing an optical component according to claim 6, which comprises 5% by weight of silver. 9. The method for manufacturing an optical component according to claim 6, wherein the solder has a film thickness of 3 to 40 μm. 10. The material of the solder-fixed surface of the holder is ferritic stainless steel, and the material of the solder-fixed surface of the optical element is rutile.
9. The method for manufacturing an optical component according to any one of 9 above.