JP4070098B2 - Method of soldering ferrule and optical fiber - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for soldering a ferrule and an optical fiber, and more particularly to a method capable of soldering and fixing an optical fiber to a ferrule in a short time without causing thermal damage to the optical fiber coating.
[0002]
[Prior art]
In general, an optical module is assembled by disposing a light emitting device in a housing, introducing a tip portion of an optical fiber from the outside into the housing, and optically connecting the leading end to the light emitting device. In that case, the optical fiber tip is peeled off and the optical fiber core is bare, and the surface of the bare optical fiber is covered with, for example, Au plating. By being applied, it is in a metallized state.
[0003]
When the optical fiber and the light emitting device are optically connected, or at a place where the optical fiber is introduced into the housing, a ferrule made of, for example, Kovar whose thermal expansion coefficient is similar to that of glass is generally used, and the optical fiber is used for the ferrule. The optical fiber and the ferrule are fixed and integrated with, for example, a solder material, and the integrated product is fixed at a predetermined position.
[0004]
FIG. 4 shows an example of fixing work by soldering a ferrule and an optical fiber.
In FIG. 4, the optical fiber coating 1a at the tip is peeled and removed from the center through hole 2a of the ferrule 2 in which the center through hole 2a having a predetermined diameter is formed, and the surface is metalized with, for example, Au. An optical fiber 1 having an optical fiber core wire 1b is inserted. In this case, it is assumed that a part of the optical fiber coating 1a is also inserted into the central through hole 2a of the ferrule.
[0005]
Then, the solder material 3 is disposed on the upper end surface 2 b of the ferrule 2. Recently, Pb-free materials are used as the solder material 3 in consideration of environmental problems. For example, a ring foil made of an Au—Sn alloy (Sn: about 20 mass%) is generally used.
Next, the solder material 3 is generally heated and melted in the atmosphere and allowed to flow into the center through hole of the ferrule, and further cooled. To. And it is requested | required that the solder joint part of the integrated object manufactured in this way should be equipped with the outstanding airtight characteristic, and also the high joint strength simultaneously.
[0006]
By the way, the following methods are conventionally employ | adopted regarding the heat melting of the solder material 3. FIG.
The first method is a resistance heating method. In this method, as shown in FIG. 5, the optical fiber 1 is inserted into the V-shaped groove 4a of the fixing plate 4 made of ceramic, for example, in which the V-shaped groove 4a is formed, and the solder material 3 is placed on the upper end surface. The ferrule 2 is placed, and the upper end side of the ferrule 2 is pressed by a heating plate 5 made of, for example, a Mo steel plate and having a V-shaped notch, and in this state, the heating plate 5 is energized to generate resistance heat. The solder material 3 is heated and melted.
[0007]
The second method uses a lamp heater. In this method, as shown in FIG. 6, an optical fiber is inserted into the ferrule 2, a solder material 3 is disposed on the upper end surface of the ferrule, and a light source 6 such as a xenon lamp is disposed above the solder material 3. And a concave mirror 7 and a condenser lens 8 are arranged.
Then, the light source 6 is turned on, the light is condensed by the concave mirror 7 and the condensing lens 8 and irradiated to the solder material 3, and the solder material 3 is heated and melted.
[0008]
[Problems to be solved by the invention]
However, the conventional heating method described above has the following problems.
First, in the case of the resistance heating method, the time required for heating and melting the solder material is long, and the productivity of the soldering work is poor. In addition, only the solder material cannot be selectively heated, and the entire ferrule is heated. As a result, for example, when an optical fiber coating is inserted in the through hole of the ferrule, The fiber coating is thermally damaged, so that the strength of the optical fiber 1 is deteriorated.
[0009]
In the case of a heating method using a lamp heater, the solder material can be selectively heated by focusing at the time of condensing. However, due to variations in the reflectance and absorptance specified by the surface condition of the material to be heated, such as solder material and ferrule, the heating state of the solder material becomes non-uniform, and the solder material is melted uniformly. The problem of not doing arises.
[0010]
Moreover, although the above heating method is normally performed in air | atmosphere, in that case, the surface oxidation of molten solder advances and the wettability of solder deteriorates. This problem can be solved by using flux together.
However, if flux is used, the flux may remain in the assembled optical module, and the reliability of the optical module may be reduced.
[0011]
The present invention solves the above-mentioned problems when the conventional heating method is implemented, and can selectively heat and melt only the solder material in a short time, and thus does not cause thermal damage to the optical fiber coating. An object of the present invention is to provide a method for soldering an optical fiber and a ferrule.
[0012]
[Means for Solving the Problems]
In order to achieve the above-described object, in the present invention, after the metallized optical fiber core wire is inserted into the central through hole of the cylindrical metal ferrule, the metal ferrule and the optical fiber are used using a solder material. A method for soldering a ferrule and an optical fiber is provided, wherein the solder material is heated and melted by induction heating when soldering the core wire.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, the soldering and melting of the solder material is performed by a high frequency induction heating method. One example of the state in which the solder material is heated and melted by the method of the present invention is shown in FIG.
As shown in FIG. 1, the optical fiber 1 is inserted into the through hole of the ferrule 2, and the metallized optical fiber core wire 1 b is projected from the ferrule 2. Here, it is assumed that a part of the optical fiber coating 1a is also inserted into the through hole of the ferrule 2.
[0014]
Next, a ring-shaped solder material 3 is disposed on the upper end surface 2 b of the ferrule 2.
Here, in order to realize the joining of the optical fiber core wire 1b and the ferrule 2 in the absence of flux, it is preferable to use an Au—Sn alloy as the solder material 3, and to improve the solder joint strength and airtightness. Therefore, a three-layer metallized film made of, for example, Ti / Ni / Au is formed on the surface of the optical fiber core, and an electroless plating film made of, for example, Ni / Au is also formed on the surface of the ferrule 2 at the same time. It is preferable.
[0015]
Next, the high frequency coil 9 is arranged. As shown in FIG. 1, the high-frequency coil 9 has a planar positional relationship in which the center of the plane formed by the ring of the coil matches the axis of the optical fiber core 1b, and the vertical positional relationship. Then, it arrange | positions so that the center of the coil cross section and the thickness center of the solder material 3 may correspond substantially. By adopting such an arrangement, induction magnetism generated by the operation of the high-frequency coil 9 is efficiently introduced into the solder material 3, and only the solder material 3 is selectively heated without heating the ferrule 2 and the like. be able to.
[0016]
If the positional relationship described above is shifted even a little, a shift occurs in the location where the induction magnetism is intensively introduced and the time until the solder material 3 melts varies, so that the arrangement of the high frequency coil 9 is accurate. Should be done.
Here, the number of turns of the high-frequency coil 9 is not particularly limited. For example, when a high-frequency application with an oscillation frequency of 2 MHz and an output of about 400 W is assumed, if the number of turns is 1 turn, the solder material 3 can be obtained in a short time. It is possible to realize the heat melting of.
[0017]
If the inner diameter (d) of the high-frequency coil 9 is reduced, the solder material 3 can be easily heated and melted, and at the same time, the time required for melting is shortened. Variations in time will increase. On the contrary, when the inner diameter of the high frequency coil 9 is increased, the induction magnetism introduced into the solder material 3 is diffused, so that the heating range is widened, and accordingly, the time required for heating is increased and the productivity is lowered.
[0018]
In the present invention, the inner diameter (d) of the high-frequency coil 9 is preferably set to 40 to 100 times the diameter of the optical fiber core wire 1b. This is because the time required for heating is shortened and the variation in the heating time is also reduced.
By the way, when the solder material of the Au—Sn alloy is melted, oxidation of the molten solder proceeds rapidly and its wettability becomes extremely poor. Therefore, the molten solder in such a state does not flow into the through hole of the ferrule 2 and the solder joint between the ferrule and the optical fiber core wire 1b is not realized.
[0019]
In order to prevent such a problem from occurring, in the present invention, it is preferable to operate the high-frequency coil 9 in a state where the periphery of the solder material 3 is in a non-oxidizing atmosphere. Specifically, heating and melting may be performed while a non-oxidizing gas such as nitrogen, argon, or helium is blown onto the solder material 3 from a nozzle (not shown).
In addition, the Au—Sn alloy is gradually oxidized even in the atmosphere at room temperature. Therefore, it is preferable that the surface of the Au—Sn alloy used in the present invention is subjected to ultrathin Au plating. This is because when used as a solder material, the surface is not oxidized, so that heat-melting is stabilized.
[0020]
In addition, it is preferable to add about 5 vol% of hydrogen to the gas when the gas is blown. This is because even when the surface of the solder material is already oxidized, stable soldering can be realized by reducing the oxide film with hydrogen during heating and melting.
[0021]
【Example】
Example 1
An optical fiber having an optical fiber core wire of 125 μm in diameter and made of Ti / Ni / Au metallized with a thickness of 0.8 μm, and a Kovar ferrule with an inner diameter of 0.3 mm, a diameter of 1 mm, and a length of 10 mm (on the surface) Ni / Au electroless plating) and a ring solder material made of Au-20% Sn and having an inner diameter of 0.3 mm, an outer diameter of 1 mm, and a thickness of 0.1 mm were prepared.
[0022]
On the other hand, a high-frequency coil having a pipe diameter of 1 mm, an inner diameter (d) of 9 mm, and one turn was prepared. These are arranged in the positional relationship as shown in FIG. 1, and simultaneously, nitrogen is blown from a nozzle with a diameter of 5 mm (not shown) to the solder material 3 at a flow rate of 10 L / min. A high frequency of 400 W was applied.
After application of the high frequency, melting of the solder material 3 started in about 0.5 seconds, the molten solder flowed into the ferrule 2 in about 1 second, and the soldering operation was completed.
[0023]
Soldering was performed 10 times in the manner described above. In any case, thermal damage of the optical fiber coating did not occur, and at the same time, the hermetic property at the solder joint was 1.0 × 10 ⁻¹⁰ Pa / m ³ · s or less, and the joint strength was 10 N or more. .
[0024]
Example 2
In Example 1, the time required for soldering was examined by changing the type of gas sprayed onto the solder material 3 and the type of solder material.
Here, the time required for soldering means the time from the start of heating until the solder material melts and flows into the ferrule. The results are shown in FIG.
[0025]
In FIG. 2, only the N ₂ (flow rate 10 L / min) is sprayed with ◆, and the solder material is Au-20% Sn alloy material, and only the N ₂ (flow 10 L / min) is sprayed with ■ When the material is Au-20% Sn alloy surface with ultra-thin Au plating, Δ is sprayed with Ar only (flow rate 10L / min), and solder material is Au-20% Sn alloy material □ indicates the case where a gas containing N ₂ containing H ₂ (about 5 vol%) is blown, and the solder material is an Au-20% Sn alloy material.
[0026]
As is apparent from FIG. 2, when a solder material plated with Au is used, the soldering time is shortened and the variation is also reduced. In addition, when H ₂ is included in the gas to be blown, the same good results are obtained.
[0027]
Example 3
In Example 1, soldering was performed using high frequency coils having different inner diameters (d), and the time required for melting the solder material at that time was examined. The results are shown in FIG.
In FIG. 3, ♦ indicates that the inner diameter (d) is 30 times the diameter of the optical fiber core 1b, and □ indicates that the inner diameter (d) is 40 times the optical fiber core 1b. Indicates that the inner diameter (d) is 70 times the diameter of the optical fiber core 1b, x indicates that the inner diameter (d) is 100 times the optical fiber core 1b, and * indicates the inner diameter (d). The case where it is 150 times the diameter of the optical fiber core wire 1b is shown.
[0028]
As is clear from FIG. 3, when the inner diameter (d) is 40 to 100 times the diameter of the optical fiber core wire, the time required for heating is short and the variation is small.
[0029]
Comparative Example 1
Using the optical fiber, ferrule, and solder material used in Example 1, soldering was performed by the resistance heating method shown in FIG. At this time, N ₂ (flow rate: 10 L / min) was sprayed on the solder material to prevent the molten solder from being oxidized.
The heating plate 5 was energized to generate heat up to a temperature of 300 ° C. It took 10 seconds until the temperature reached 300 ° C. Further, it took about 10 seconds for the solder material to finish flowing into the ferrule while maintaining the temperature at 300 ° C. The cooling took 5 to 10 seconds.
[0030]
When the above operation was performed 10 times, the time until the solder material finished flowing into the ferrule varied from 5 to 15 seconds. Further, when the optical fiber was observed after the soldering was completed, deformation of the fiber coating was observed, and when the optical fiber was pulled, it was easily broken.
[0031]
Comparative Example 2
Using the optical fiber, ferrule, and solder material of Example 1, soldering was performed by the heating method using the lamp heater shown in FIG. At this time, N ₂ was sprayed on the solder material to prevent oxidation.
About 0.5 seconds after the start of light irradiation, the solder material began to melt. However, the melting method was non-uniform, and no uniform inflow into the ferrule was observed.
[0032]
In addition, soldering was performed 10 times, and the airtight characteristics and the bonding strength of the solder joint at that time were measured. As a result, the airtight characteristics were both 1.0 × 10 ⁻¹⁰ Pa / m ³ · s or more and Three of them satisfied the characteristic of strength of 10N or more.
[0033]
【The invention's effect】
As is apparent from the above description, according to the method of the present invention, the optical fiber and the ferrule can be soldered in a state with excellent hermetic properties and bonding strength in a short time without causing thermal damage to the optical fiber coating. Therefore, the method of the present invention is effective when applied at the time of assembling the optical module.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram for explaining an example of an induction heating method according to the present invention.
FIG. 2 is a graph showing the results of Example 2.
3 is a graph showing the results of Example 3. FIG.
FIG. 4 is a partially cutaway sectional view showing a state in which an optical fiber is inserted through a ferrule.
FIG. 5 is a schematic view showing a conventional resistance heating method.
FIG. 6 is a schematic view showing a heating method using a conventional lamp heater.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Optical fiber 1a Optical fiber core wire 1b Fiber coating 2 Ferrule 2a Through-hole 2b of ferrule 2 Upper end surface 3 of ferrule 2 Solder material 9 High frequency coil

Claims (4)

After the metallized optical fiber core wire is inserted into the central through hole of the cylindrical metal ferrule, when the metal ferrule and the optical fiber core wire are soldered using a solder material, the induction heating method is used. In the ferrule and optical fiber soldering method that heats and melts the solder material ,
A ferrule and an optical fiber soldering method , wherein an inner diameter of a high-frequency coil used in the induction heating method is 40 to 100 times a diameter of the optical fiber core wire . After the metallized optical fiber core wire is inserted into the central through hole of the cylindrical metal ferrule, when the metal ferrule and the optical fiber core wire are soldered using a solder material, the induction heating method is used. In the ferrule and optical fiber soldering method that heats and melts the solder material ,
The method of soldering a ferrule and an optical fiber, wherein the solder material is an Au-Sn alloy material having a surface plated with Au . 3. The method for soldering a ferrule and an optical fiber according to claim 1, wherein soldering is performed in a non-oxidizing atmosphere around the solder material. The method for soldering a ferrule and an optical fiber according to claim 3 , wherein the non-oxidizing atmosphere contains hydrogen.

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