JP5419780B2 - Ferrule for fixing optical fiber and optical fiber fixture using the same - Google Patents

Description

  The present invention relates to an optical fiber fixing ferrule used for optical communication and the like, and an optical fiber fixing tool using the same.

  An optical fiber fixture may be used for a laser diode module for optical communication. For example, the optical fiber fixture is optically adjusted so that light emitted from a laser diode (hereinafter also referred to as LD) is collected by a rod lens and efficiently incident on the optical fiber in the optical fiber fixture. Used fixed in the optical package. The LD needs to be hermetically sealed in the optical package for output stability and prevention of deterioration. For this reason, an optical fiber fixing device in which an optical fiber is hermetically sealed with a ferrule may be further hermetically sealed in an optical package.

  In such an optical fiber fixture, solder excellent in hermetic sealing is used for joining the optical fiber and the ferrule. In this case, the melting point of the primary solder used for joining the optical fiber and the ferrule needs to be higher than the melting point of the secondary solder used for joining the optical fiber fixture and the optical package. When the melting point of the primary solder is lower than the melting point of the secondary solder, the primary solder is melted by heating when the optical fiber fixture is joined to the optical package, and the reliability of hermetic sealing may be reduced. Further, there is a possibility that a position shift occurs in the optical fiber whose optical axis is adjusted.

  Therefore, as the primary solder, conventionally, a so-called high-temperature solder having a melting point of about 270 ° C. to 300 ° C. such as gold-tin, lead-tin, lead-gold, tin-silver, etc. is used. As the secondary solder, a tin-lead solder (so-called eutectic solder) having a melting point of about 184 ° C. was used (see, for example, Patent Document 1 and Patent Document 2).

Japanese Utility Model Publication No. 5-27707 JP 2002-214478 A

However, in recent years, there has been RoHS (Restriction on Hazardous Substances) in Europe.
) In order to prevent adverse effects on the environment such as directives, it is becoming necessary to avoid the use of lead (so-called lead-free). Therefore, there is a need to provide an optical fiber fixing ferrule and an optical fiber fixture using solder instead of the conventional lead-based high-temperature solder.

Therefore, lead-free solders such as tin-silver solders and tin-silver-copper solders are frequently used as secondary solders in place of conventional tin-lead solders. Such lead-free solder has a relatively high melting point of about 220 ° C. or higher compared to conventional tin-lead solder. for that reason,
The primary solder is also required to have a higher melting point than before.

  As such solder, solder containing gold-tin, lead-gold, tin-silver, gold or silver is expensive. Furthermore, since the residual stress after sealing is large, there may be a problem that the optical fiber breaks inside the ferrule after joining with the primary solder.

  The present invention has been devised in view of such conventional problems, and an object of the present invention is to use a lead-free solder and a ferrule for fixing an optical fiber and an optical fiber that have high reliability in joining between an optical fiber and a ferrule. It is to provide a fixture.

  An optical fiber fixing ferrule according to an embodiment of the present invention has a through hole for inserting an optical fiber in a central portion, and a ferrule having a recessed portion in which the diameter of the through hole is increased at one end portion of the through hole. A metal layer formed on the inner wall surface of the recess, and a solder layer bonded to the metal layer so as to cover at least a part of the metal layer, the solder layer on the inner wall surface side of the recess A first solder layer having an alloy phase of tin and a metal component of the metal layer as a main component, and a melting point higher than that of the first solder layer having a bismuth phase as a main component and including a tin-bismuth alloy phase. And a low second solder layer.

  In the optical fiber fixing ferrule, the metal layer preferably contains nickel, cobalt, gold, or copper.

  An optical fiber fixture according to an embodiment of the present invention includes the optical fiber fixing ferrule, a second metal layer formed on the outer peripheral surface of the tip, inserted through the through-hole, and the second metal layer. And an optical fiber in which the second solder layer is bonded and hermetically sealed, and the solder layer mainly contains an alloy phase of tin and a metal component of the second metal layer, and the second A third solder layer having a melting point higher than that of the solder layer is formed.

  In the optical fiber fixture, it is preferable that the metal component of the second metal layer includes nickel, cobalt, gold, or copper.

  According to the ferrule for fixing an optical fiber according to one embodiment of the present invention, the center portion has a through hole for inserting the optical fiber, and the through hole has a recessed portion in which the diameter of the through hole is increased. It includes a ferrule, a metal layer formed on the inner wall surface of the recess, and a solder layer bonded to the metal layer so as to cover at least a part of the metal layer, and the solder layer is disposed on the inner wall surface side of the recess A first solder layer mainly composed of an alloy phase of tin and a metal component of the metal layer, and a second solder layer having a bismuth phase as a main component and having a melting point lower than that of the first solder layer including the tin-bismuth alloy phase. By comprising the solder layer, it is possible to provide a ferrule for fixing an optical fiber which is lead-free and has a high reliability of hermetic sealing of the joint between the optical fiber and the ferrule.

  That is, the first solder layer is mainly composed of an alloy phase of tin having a melting point exceeding 320 ° C. and the metal component of the metal layer, and the first solder layer has a second melting point at the remelting temperature of the second solder layer when the optical fiber is joined. 1 Solder layer is not remelted. On the other hand, since the second solder layer is a solder layer containing a tin-bismuth alloy phase and having a low melting point, it can be remelted at about 280 ° C. to 300 ° C. slightly higher than the melting point to join the optical fibers.

  Further, in the ferrule for fixing an optical fiber, when the metal layer formed on the inner wall surface of the concave portion of the ferrule contains nickel, cobalt, gold or copper, an alloy is formed with tin in the solder layer, and the melting point is 320. A first solder layer exceeding ℃ can be formed.

An optical fiber fixture according to an embodiment of the present invention includes the above-described ferrule for fixing an optical fiber, a second metal layer formed on the outer peripheral surface of the tip, inserted through a through hole, and a second metal layer and a second solder. And an optical fiber hermetically sealed by joining the layers, and the solder layer is mainly composed of an alloy phase of tin and the metal component of the second metal layer, and has a melting point higher than that of the second solder layer. Since the third solder layer is formed, when the optical fiber fixture is joined to the optical package using lead-free secondary solder, the third solder layer includes tin and the metal component of the second metal layer. The first solder layer is a high melting point alloy phase of tin and a metal component of the metal layer, and the remaining solder layer is mainly composed of a bismuth layer having a melting point of 271 ° C. Therefore, the solder layer melts during secondary soldering with a sealing temperature of about 250 ° C. It is not to be. Accordingly, it is possible to maintain the airtight reliability between the optical fiber and the ferrule.

  In the above optical fiber fixture, when the metal component of the metal material of the second metal layer formed on the outer peripheral surface of the optical fiber includes nickel, cobalt, gold and copper, tin in the solder layer An alloy can be formed to form a third solder layer with a melting point above 320 ° C.

It is sectional drawing which shows an example of embodiment of the ferrule for optical fiber fixation of this invention. It is sectional drawing which shows an example of embodiment of the optical fiber fixing tool of this invention.

  An example of an embodiment of an optical fiber fixing ferrule and an optical fiber fixture according to the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a cross-sectional view showing an optical fiber fixing ferrule 4 according to an embodiment of the present invention. In FIG. 1, the ferrule 1 has a cylindrical shape provided with a through hole 1a for inserting an optical fiber at the center axis position. At one end portion (left side in FIG. 1) of the through hole 1 a, a through hole 1 a having a large diameter is formed, and a concave portion 1 b opened on one end surface of the ferrule 1 is formed. A metal layer 2 is formed on the inner wall surface of the recess 1b. Furthermore, a solder layer 3 is joined so as to cover the metal layer 2 inside the recess 1b. In the example shown in FIG. 1, the other end side (the right side in FIG. 1) of the through hole 1a is formed with an optical fiber coating holding portion 1c having a thick inner diameter to hold the coating portion of the optical fiber. Yes.

  FIG. 2 is a cross-sectional view of the optical fiber fixture 10 according to an embodiment of the present invention. An optical fiber fixture 10 shown in FIG. 2 is obtained by hermetically sealing an optical fiber 5 to the optical fiber fixing ferrule 4 of FIG. The optical fiber 5 has a second metal layer 6 formed on the outer peripheral surface of its tip. And the through-hole 1a and the solder layer 7 are penetrated, and the front end surface is exposed to one end surface of the ferrule 1. The optical fiber 5 was hermetically sealed to the ferrule 4 for fixing the optical fiber by the solder layer 7 that was cooled and solidified after the second solder layer 3b of the solder layer 3 was remelted and inserted into the recess 1b. Is. In addition, in FIG. 2, the end of the ferrule 1 has shown the example in which the diagonal grinding | polishing process is performed. In accordance with this, the surface of the solder layer 7 is also inclined obliquely with respect to the plane perpendicular to the axial direction of the ferrule 1.

  In FIG. 2, the solder layer 7 is located on the inner wall surface side of the recess 1 b and is formed on the first solder layer 3 a, the central axis side, or the outer periphery of the optical fiber 5 at the time of joining to the metal layer 2 of the ferrule 1. A third solder layer 7a which is located on the surface side and formed when the second solder layer 3b and the second metal layer 6 of the optical fiber 5 are joined together; and the first solder layer 3a and the third solder layer 7a; And the remaining solder layer (hereinafter referred to as the fourth solder layer 7b) formed by changing the components of the second solder layer 3b when the third solder layer 7a is formed. ing.

The ferrule 1 has a cylindrical shape having a through hole 1a. The through hole 1a has a recess 1b at one end and an optical fiber coating holding portion 1c at the other end. Ferrule 1 is, for example, a metal material such as ceramics such as an aluminum oxide sintered body, an aluminum nitride sintered body, or a zirconium oxide sintered body, an iron-nickel-cobalt alloy, an iron-nickel alloy, copper, and aluminum. Or made of resin or glass material.

  Note that the through-hole 1a of the ferrule 1 is formed with an inner diameter larger than the outer diameter of the second metal layer at the tip of the optical fiber 5 in order to pass the optical fiber 5 as described above. 1 and 2, the concave portion 1b is shown as a cylindrical hole, but it may be a curved surface or a linear cone shape whose diameter gradually increases toward one end surface of the ferrule 1.

  For example, if the ferrule 1 is made of an aluminum oxide sintered body, a paste formed by mixing aluminum oxide and an inorganic additive with a resin binder and a solvent is formed into a predetermined shape, and this ferrule 1 is obtained. It is formed by firing an unfired molded body. By applying a metal paste obtained by kneading a metal powder such as tungsten, molybdenum, or molybdenum-manganese together with an organic solvent and a binder to the inner wall surface of the recess 1b of the molded body, A metallized layer (not shown) is applied.

  Since this metallized layer has low solder wettability, it is preferable to deposit a metal such as nickel, cobalt, copper, or gold on the surface thereof by plating or the like. This plating layer becomes the metal layer 2. 1 and 2, the metal layer 2 is not formed on the bottom surface of the recess 1b (the surface facing the opening of the recess 1b). This is to reduce the possibility that the metal paste will sag inside the through hole 1a and the optical fiber 5 cannot be inserted when forming the metallized layer. Therefore, the metal layer 2 may be formed on the bottom surface of the recess 1b so that the metallized layer does not block the through hole 1a, or the metal layer 2 is formed on the outer peripheral side of the bottom surface of the recess 1b, It may not be formed on the center side. The metal layer 2 may be formed directly on the ceramic surface by, for example, a metal vapor deposition method without forming a metallized layer.

  Further, for example, if the ferrule 1 is made of an iron-nickel-cobalt alloy or the like, it can be manufactured by subjecting this alloy material to processing such as lathe processing into a predetermined shape and size. Even when the ferrule 1 is formed of a metal material, it is preferable to deposit a plating layer of nickel, gold, copper or the like on the entire surface of the ferrule 1 to suppress oxidation of the ferrule 1.

  Next, the solder layer 3 is formed on the surface of the metal layer 2 by the following method. That is, a lead-free bismuth-tin solder paste (not shown) containing 6 to 10% by mass of tin is applied to the surface of the metal layer 2 such as nickel, cobalt, gold or copper in the recess 1b. And this paste is heated at 280-300 degreeC for about 1-2 minutes. Then, the tin component of the bismuth-tin solder and the metal component of the metal layer 2 form an alloy phase at the joint interface portion, and the first solder layer 3a is deposited. Further, the remaining portion of the solder layer 3 becomes an alloy layer containing about 2 to 5 mass% of the tin component, that is, the second solder layer 3b, by diffusing a part of the tin component into the first solder layer 3a.

  Note that the solder layer 3 may be used slightly more so as to rise from one end face of the ferrule 1. Such a shape is desirable when the end of the ferrule 1 and the front end surface of the optical fiber 5 are mirror-finished by polishing the front end obliquely after fixing the optical fiber 5.

The thickness of the metal layer 2 is preferably 5 to 20 μm. If the thickness is 5 μm or less, solder erosion due to the solder layer 3 occurs, and there is a tendency that airtightness cannot be secured. If the thickness is 20 μm or more, the amount of metal in the metal layer 2 increases, and most of the tin component in the solder layer 3 becomes the first solder layer 3a which is an alloy layer with the metal layer 2, and the melting point of the second solder layer 3b is low. There is a tendency to have a high melting point of about 270 ° C.

The first solder layer 3a is mainly composed of an alloy phase of tin and the metal component of the metal layer 2, and has a melting point exceeding 320 ° C., which is higher than the melting point 275 ° C. of the conventional lead-based high-temperature solder. Become. Note that the entire first solder layer 3 a may be composed of an alloy phase of a tin-metal component, or may include a bismuth phase or an alloy phase of bismuth and the metal component of the metal layer 2.

  Further, in the composition in which the second solder layer 3b includes about 2 to 5% by mass of a tin component and constitutes a bismuth-tin phase, the tin component is partially included as a tin phase or an alloy phase of tin and a metal material. It may be. The second solder layer 3b made of bismuth-tin solder having the above composition may contain an alloy phase of bismuth and the metal component of the metal layer 2. Here, since the second solder layer 3b contains bismuth, the melting point is 271 ° C., and the melting point is lower than that of the first solder layer 3a exceeding 320 ° C.

  Next, in the optical fiber fixture 10 of the present invention, the optical fiber 5 is joined to the recess 1b through the solder layer 7. The optical fiber 5 has a predetermined thickness obtained by depositing nickel, cobalt, gold, copper, or the like on the outer peripheral surface of the tip and performing a base treatment, and then plating the surface of the optical fiber 5 with nickel, cobalt, gold, copper, or the like. The second metal layer 6 is formed. Then, the second solder layer 3b of the optical fiber ferrule 4 is heated and melted, and the optical fiber 5 is inserted from the other end of the ferrule 1 so that the second metal layer 6 and the second solder layer 3b of the optical fiber 5 are inserted. It is produced by joining.

The fourth solder layer 7b containing the bismuth phase as a main component has a melting point close to the melting point 271 ° C. of bismuth. For example, the ferrule 1 and the optical fiber 5 can be joined without melting at a sealing temperature of 240 ° C. to 250 ° C. when a tin-silver-copper solder having a melting point of 223 ° C. is used as the secondary solder. . Even when the optical fiber fixture 10 is mounted on an optical package using a lead-free secondary solder such as a tin-silver system having a sealing temperature of 250 ° C., the fourth solder layer 7b does not melt.

The first solder layer 3a of the solder layer 7 is formed when the optical fiber fixing ferrule 4 is manufactured. Since the melting point of the first solder layer 3a and the third solder layer 7a is higher than 320 ° C., the first solder layer 3a and the third solder layer 7a are not melted when mounted on the optical package using the secondary solder. Therefore, it is possible to provide the optical fiber fixture 10 with high reliability of hermetic sealing of the solder layer 7.

  The third solder layer 7a is mainly composed of an alloy phase of tin and the metal component of the second metal layer 6, and all of it may be composed of an alloy phase of a tin-metal component. Further, it may contain a bismuth phase of about several mass% or an alloy phase of bismuth and the above metal component.

  The fourth solder layer 7b is formed by moving the tin component of the second solder layer 3b to the third solder layer 7a. That is, the bismuth phase is the main component and the melting point is changed to a refractory metal that is about the melting point of bismuth. As a result, the optical fiber fixing device 10 can maintain the hermetic sealing reliability even when secondary soldering is performed. The fourth solder layer 7b may be entirely formed of a bismuth phase, or may include a metal component of the metal layer 2 or an alloy phase of the metal component of the second metal layer 6 and bismuth.

  Here, if the configuration of the second solder layer 3b of the ferrule 4 for fixing an optical fiber includes, for example, about 2 to 5% by mass of a tin component, the heating condition in the heating furnace is set to 280 to 300. What is necessary is just to set to about 1-2 minutes at ° C. The tin component of the second solder layer 3b reacts with the metal component of the second metal layer 6 to form an alloy phase, and the fourth solder layer 7b after joining has a composition mainly composed of the bismuth phase as described above. be able to.

In this case, since the tin-bismuth alloy phase and the tin phase are present in the second solder layer 3b, the joining is started from a relatively low heating temperature, and the wettability of the second solder layer 3b to the second metal layer 6 is improved. Rise. Thereafter, when solidified, the fourth solder layer 7b having a melting point higher than that of the second solder layer 3b is obtained. When the metal component of the metal layer 2 and the metal component of the second metal layer 6 are at least one of nickel, cobalt, gold and copper, the melting points of the first solder layer 3a and the third solder layer 7a are increased. The reliability of the optical fiber fixture 10 for hermetic sealing can be further increased. Further, it is possible to provide the optical fiber fixture 10 having good practicality.

  Here, the thickness of the second metal layer 6 is desirably 5 to 10 μm. If the thickness is 5 μm or less, solder erosion occurs due to the solder layer, and airtightness tends not to be ensured. If it is 10 μm or more, it tends to be difficult to form the second metal layer 6 uniformly on the outer periphery of the optical fiber 5, and it becomes difficult to place the center of the optical fiber 5 at the center of the through hole 1a.

  Further, according to the optical fiber fixture 10 according to the embodiment of the present invention, the fourth solder layer 7b is a buffer layer because the fourth solder layer 7b is disposed between the optical fiber 5 and the ferrule 1. The possibility of breakage due to internal stress applied to the optical fiber 5 during solder bonding can be reduced.

  As described above, by using the ferrule 4 for fixing an optical fiber and the optical fiber fixture 10 according to one embodiment of the present invention, it becomes possible to perform sealing with lead-free solder instead of the conventional lead solder for sealing, It is possible to provide the optical fiber fixture 10 having a high hermetic sealing reliability with less possibility of breaking the optical fiber 5 at the time of joining.

A cylindrical ferrule 1 having a recess 1b having a diameter of 1.5 mm is prepared at the tip of an aluminum oxide sintered body, and a metal paste containing molybdenum-manganese is applied to the inner peripheral surface of the recess 1b and simultaneously fired. What prepared the nickel plating of thickness 10micrometer on the layer surface was prepared. A bismuth-tin solder paste containing 6% by mass of tin is applied to the recess 1b.
The solder layer 3 was joined to the ferrule 1 by heating at 0 ° C. for 1 minute.

The first solder layer 3a of the solder layer 3 is mainly composed of a tin-nickel alloy phase, and the second solder layer 3b is made of bismuth containing 3.8% by mass of tin in addition to the bismuth phase according to WDS analysis. It contained an alloy phase. When confirmed by the SEM image, the first solder layer 3a and the second solder layer 3b were observed in different shades, and the boundary could be clearly confirmed.

In addition, a silica-glass single-mode optical fiber 5 having a core diameter of 10 μm and a cladding diameter of 125 μm is prepared, and 0.1 μm thick copper is vapor-deposited on the outer periphery of the tip, and then 0.8 μm thick nickel is vapor deposited on the surface A second metal layer 6 having a nickel plating thickness of 8 μm was formed. Then, the prepared optical fiber fixing ferrule 4 is heated to 290 ° C., the second solder layer 3b is remelted, the optical fiber 5 is inserted from the rear end of the ferrule 1, and maintained for 1 minute. It was naturally cooled to 25 ° C over a period of minutes.

  Thereafter, the tip end portion of the ferrule 1 was obliquely polished and mirror-finished to produce 100 optical fiber fixtures 10.

The optical fiber fixture 10 used was tin-silver-copper solder as a secondary solder, and hermetically sealed in an optical package at 250 ° C. for 1 minute was checked for sealing performance by a helium leak test. Further, in order to confirm whether or not the optical fiber 5 was broken, it was confirmed by looking through the front end surface of the optical fiber 5 with a 400 × metal microscope that there was no damage inside.

As a comparative example, an optical fiber 5 and a ferrule 1 using a lead-tin solder having a melting point of 183 ° C.
10 optical fiber fixtures were prepared, and hermetically sealed with a lead-tin high melting point solder containing 90% lead as in the above example, and the reliability of the sealing performance was confirmed.

As a result, in the 100 optical fiber fixtures 10 tested, no leak failure occurred,
It was confirmed that the reliability of hermetic sealing was high. Further, the breakage of the optical fiber 5 could not be detected. In addition, although the optical fiber fixing device of the comparative example did not cause a leak failure, 5 of the 20 optical fibers were broken.

  The present invention is not limited to the above-described embodiments and examples, and various modifications can be made without departing from the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Ferrule 1a ... Through hole 1b ... Recess 1c ... Optical fiber coating holding part 2 ... Metal layer 3 ... Solder layer 3a ... First solder layer 3b ... Second solder layer 4 ..Ferrule 5 for fixing an optical fiber ... Optical fiber 6 ... Second metal layer 7 ... Solder layer 7a ... Third solder layer 7b ... Fourth solder layer 10 ... Optical fiber fixing tool

Claims (4)

A ferrule having a through hole for inserting an optical fiber in the center, a recess having an enlarged diameter of the through hole at one end of the through hole, a metal layer formed on the inner wall surface of the recess, A solder layer bonded to the metal layer so as to cover at least a part of the metal layer, the solder layer being disposed on the inner wall surface side of the recess, and an alloy of tin and a metal component of the metal layer A light comprising: a first solder layer having a phase as a main component; and a second solder layer having a bismuth phase as a main component and having a melting point lower than that of the first solder layer including a tin-bismuth alloy phase. Ferrule for fixing fiber. 2. The ferrule for fixing an optical fiber according to claim 1, wherein the metal layer contains nickel, cobalt, gold, or copper. The ferrule for fixing an optical fiber according to claim 1 or 2, a second metal layer is formed on the outer peripheral surface of the tip, and the second metal layer and the second solder layer are joined while being inserted through the through hole. A third solder having a melting point higher than that of the second solder layer, the main component of which is an alloy phase of tin and a metal component of the second metal layer. An optical fiber fixture having a layer formed thereon. The optical fiber fixture according to claim 3, wherein the metal component of the second metal layer includes nickel, cobalt, gold, or copper.

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