JP2000026988A - Au-Sn WELDING MEMBER AND ITS PRODUCTION - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an Au-Sn welding member used for the welding between a coated optical fiber and a ferrule. SOLUTION: This Au-Sn welding member 8 having a short size pipe shape as a whol shape and consisting of Au-Sn intermetallic compounds of an amorphous structure is produced by applying Au-Sn plating to a long size wire rod composed of an electrically conductive material to form an Au-Sn plated wire rod, cutting the Au-Sn plated wire rod to a desired length to form into a short size wire rod piece and moreover selectively removing the electrically conductive material forming the core part of the short size wire rod piece.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a welding Au-Sn member and a method for manufacturing the same, and more particularly, to a novel method for welding an optical fiber between a fiber core and a ferrule at the time of manufacturing an optical module. The present invention relates to a novel Au-Sn member for welding and a method for manufacturing the same by an electroplating method.

[0002]

2. Description of the Related Art In recent years, research and development of an optical module having a structure in which a light emitting device such as an LD is optically connected to the tip of an optical fiber and the entire optical connection portion is sealed. One example of such an optical module is shown in FIG.

In this optical module, a light-emitting device 2 is disposed in a housing 1, and the light-emitting device 2 is exposed to a predetermined length by stripping and removing a coating 3a. The tip of the fiber core 3b is optically connected.

In this case, a first ferrule 4 made of a material whose thermal expansion coefficient is similar to that of glass, for example, Kovar, is disposed in the light emitting device 2, and the tip of the fiber core wire 3 b is inserted through this ferrule 4. Thereafter, the space between the fiber core 3b and the ferrule 4 is hermetically fixed with a sealing material 5a, and the space between the first ferrule 4 and the light emitting device 2 is also hermetically fixed with another sealing material 5b. Thereby, a sealing structure in the optical connection portion is formed.

Further, a second ferrule 6 is disposed in the housing 1, an optical fiber is inserted through the second ferrule 6, and the sealing material 5 between the fiber core 3 b and the second ferrule 6 is provided.
a, and the space between the second ferrule 6 and the housing 1 is sealed with another sealing material 5c to form a sealing structure of the entire optical module.

Here, regarding the above-mentioned sealing structure, especially the sealing structure 5a in the optical connection portion, the light emitting device 2
It is necessary to have excellent airtightness in order to ensure the operation reliability of the optical fiber, and to have appropriate strength characteristics so that it will not be easily damaged even when an external force is applied to an optical fiber or the like. Is required.

Conventionally, in forming the above-mentioned sealing structure 5a, a paste made of Au powder and Sn powder has been used. However, since the Au-Sn paste contains an organic component, for example, as a binder, the organic component changes in quality or volatilizes due to heat generation from the light emitting device in the actual process of the optical module, and the sealing is completed in a short time. There has been a problem that the stop structure does not work.

[0008] For this reason, recently, it has become mainstream to form a sealing structure using an Au-Sn alloy foil. A typical example will be described for the case of the first ferrule 4.

For example, as shown in FIG. 5, after the fiber core 3b is inserted through the first ferrule 4, the Au-Sn alloy rolled foil is applied to the tip of the fiber core 3b protruding from the end face 4a of the ferrule 4. A plurality of sheets (4 in the figure)
) And overlaid on the end face 4a.

The ring foil 7 generally has an outer diameter of about 500 to 1000 μm, an inner diameter of about 150 μm, and a thickness of about 20 to 30 μm. The diameter of the fiber core 3b is usually 12
The protruding length of the core fiber from the surface 4a of the ferrule is usually about 400 μm.

Then, the four superposed ring foils 7 are melted by, for example, high-frequency induction heating and then cooled, and
Re-solidify the u-Sn alloy.

As a result, as shown in FIG. 6, a part of the gap between the fiber core 3b and the first ferrule 4 and a part of the gap between the hole of the ferrule and the fiber core is re-solidified Au-S.
The fiber core 3b is hermetically fixed to the ferrule by welding with a sealing material 5a made of n alloy.

By the way, in forming the above-mentioned sealing structure, a plurality of thin ring foils are used, but instead, a single ring foil having a thickness corresponding to the thickness of the number of sheets used is used. Seems to be more effective.

However, it is extremely difficult to produce a thick ring foil having a thickness of about several hundreds of μm from an Au—Sn alloy for the following reasons. The fact is that we have to do it. The reason will be described below.

In manufacturing a ring foil of an Au-Sn alloy, first, a molten metal having a desired composition is prepared, for example, in a vacuum melting furnace, and the molten metal is cooled to form an ingot, and then the ingot is rolled, for example. To obtain a foil having a desired thickness. Then, the foil is usually processed into a ring shape by performing a punching process. Therefore, it is considered that a thick ring foil can be obtained by increasing the thickness of the foil during the above-mentioned roll rolling and performing punching on the foil.

However, an Au—Sn alloy is a brittle and difficult-to-work material because it is an intermetallic compound. Therefore, it is impossible as a practical problem to obtain a ring foil having a desired size and shape by punching a foil having a thickness of about several hundred μm.

For these reasons, the ring foil used for welding must be thin as described above, and in order to secure a sealing structure that is airtight and has excellent strength properties, the thin ring foil is used. You have to use more than one.

However, forming the sealing structure of the optical module in this manner is extremely complicated because it requires an operation of externally attaching a minute ring foil to the core fiber, and the manufacturing cost of the optical module is reduced. This leads to an increase and a decrease in yield.

[0019]

SUMMARY OF THE INVENTION The present invention provides an Au-Sn
It is possible to solve the above-described problem in the conventional method in which the fiber core wire and the ferrule are welded by using a plurality of thin ring foils of the alloy, and the welding can be sufficiently performed by using only one piece. It is an object of the present invention to provide a welding Au-Sn member and a method for manufacturing the same.

[0020]

In order to achieve the above-mentioned object, the present invention is characterized in that the whole shape is a short pipe shape and is made of an Au-Sn intermetallic compound having an amorphous structure. Au-Sn member for welding is provided.

Further, in the present invention, a step of performing Au-Sn plating on a long wire made of a conductive material to obtain an Au-Sn plated wire (hereinafter referred to as a first step);
a step of cutting the u-Sn plated wire into a desired length to obtain a short wire piece (hereinafter, referred to as a second step); and a step of removing the conductive material forming the core of the short wire piece (hereinafter, referred to as a second step). , A third step); a method for manufacturing a welding Au-Sn member, characterized by comprising:

[0022]

FIG. 1 shows an example of a member according to the present invention. The member 8 has a short pipe shape as a whole, and its material is an Au-Sn intermetallic compound having an amorphous structure manufactured by a method described later.

In this member 8, a through hole 8a is provided at the center.
Is formed, and the diameter r of the through hole 8a is large enough to insert the fiber core 3b shown in FIG. The outer diameter of the member 8 is smaller than the diameter of the end face 4a of the ferrule also shown in FIG. 5, and is usually about 50 to 100% of the diameter of the end face 4a.

Further, the length L of the member 8 is not particularly limited, but is selected to an appropriate value in relation to the thickness of the sealing structure to be formed.

This member 8 is characterized in that it is manufactured by using an Au-Sn electroplating method described later. Therefore, this member 8 is composed of Au and Sn as components, and its metal composition is mainly composed of an amorphous structure. Specifically, most of Au and Sn basically exist in an amorphous or microcrystalline state without having a predetermined crystal structure, and exist in a state where their aggregates are mixed with each other. are doing. Some Au and Sn exist in a predetermined crystal structure, respectively, and Au-Sn, AuSn ₂ , AuS
Although alloys such as n ₄ may be present, the amount of their formation is very small.
When X-ray diffraction is performed on the plating layer, no clear diffraction image is recognized in the profile, and the profile is recognized as an amorphous structure as a whole.

This member 8 is used during electroplating described later.
By changing the plating bath composition and plating conditions,
It can be adjusted to a desired component composition. Thus, the melting point of the member 8 can be set to a desired value.

This member 8 can be manufactured as follows.

In the first step, first, a long wire made of a conductive material is prepared. The wire diameter of the long wire rod is
The diameter r of the through hole 8a in the target member 8 needs to be set to be substantially the same as the diameter r, but the length is not particularly limited.

As the constituent material of the long wire, a material that can be selectively removed from the short wire piece obtained after the completion of the second step is used. For example, a metal or alloy having a lower melting point than the Au-Sn plating layer to be formed, or a material that can be selectively etched and removed using an etchant that does not dissolve the Au-Sn plating layer is used. In particular,
Wires such as Cu, Ni, Al, In, brass, nickel silver, and Monel can be given.

In the first step, Au is applied to the surface of the long wire.
-Sn plating is formed as follows.

First, a plating bath is built. In that case,
Since the difference between the standard monopolar potentials of Au and Sn is considerably large, the difference between the deposition potentials of Au and Sn during the actual electroplating operation also increases. Therefore, in order to deposit Au and Sn at the same time, it is necessary to appropriately select the types of the Au source and the Sn source, the composition of the plating bath, the plating conditions, and the like so that the deposition potentials of both are close to each other. become.

In view of the above, the plating bath according to the present invention uses, for example, potassium potassium cyanide (I) as an Au source and an organic source typified by tin citrate or tin sulfonic acid as a Sn source. Tin (II) acid is used.

The plating bath is mixed with a conductive organic acid such as sodium sulfamate, sodium citrate, and sodium acetate in an amount of about 50 to 100 g / L, so that Sn ions are divalent to tetravalent. Can be prevented from being oxidized, so that Sn can be efficiently deposited.

The melting point of the Au—Sn plating layer formed by changing the bath composition at this time can be set to a desired value. That is, first, a target melting point is set. Cuilik. J. et al., “J. Alloys and Compou
nds "191. (1993). Au-S disclosed in pp. 71-78.
The composition of Au and Sn corresponding to the melting point is read from the n-binary system phase diagram, and a plating bath containing the above-mentioned Au source and Sn source is constructed so as to enable electrodeposition of the composition ratio. Electroplating may be performed. Although a slight variation occurs from the target melting point, basically, an Au having an approximate melting point is used.
-The formation of a Sn plating layer is possible.

At the time of electroplating, an insoluble electrode such as a Pt-coated Ti plate and the above-mentioned long wire are immersed in the above-mentioned plating bath, and each is supplied with a power source so that the insoluble electrode becomes an anode and the long wire becomes a cathode. Connect to

At this time, the pH of the plating bath is 3.0 to 6.0.
0 and the bath temperature is 20-60
It is preferable to set the temperature in the range of ° C. If the pH is too low, the Au—Sn plating layer formed on the surface of the long wire has a composition in which the Au deposition ratio is large, and if the pH is too high, the surface of the plating layer tends to become cloudy. Because it increases. If the bath temperature is too low, the Au—Sn plating layer becomes a film having a large stress, and if the bath temperature is too high, the plating bath starts to deteriorate or decompose.

Next, electroplating is performed by supplying a current while stirring the plating bath. At this time, the current density is 0.1 to 1.0.
A / dm ² is preferably set. If the current density is too low, a film having a composition in which the Au deposition ratio is large is formed. If the current density is too high, the surface of the plating layer starts to powder.

Thus, when the first step is completed, as shown in FIG. 2, Au and Sn are simultaneously electrodeposited on the surface of the long wire material 9 to form the Au—Sn plating layer 10.
The u-Sn plated wire A1 is obtained. At this time, by selecting a plating time, the Au—Sn plating layer 10 is formed to have a thickness such that the entire diameter becomes R shown in FIG.

Next, in the second step, the Au-Sn plated wire A1 is cut to the length L of the member shown in FIG.
A plurality of short wire pieces are manufactured. For cutting, for example, wire electric discharge machining can be applied. As a result, as shown in FIG. 3, a short wire piece A2 in which the core is filled with the constituent material of the long wire is obtained.

In the third step, the conductive material of the core is selectively removed from the short wire rod A2 thus obtained.

The selective removal of the conductive material can be easily realized by immersing the short wire piece A2 in a ferric chloride solution when the conductive material is, for example, Cu. In the case of a material having a lower melting point than the Au-Sn plating layer like In, the short wire A2 can be heated to a temperature slightly higher than the melting point to melt and remove the core.

Thus, the member 8 of the present invention shown in FIG. 1 is obtained.

After the member manufactured in this way is externally fitted to the tip end protruding portion of the fiber cable inserted through the ferrule,
Heat to a predetermined temperature and continue to cool. This member is re-solidified after melting, and a sealing structure is formed between the fiber core and the ferrule. At this time, Au-
Sn plating converts from an amorphous structure to a crystalline structure similar to that of a rolled foil.

[0044]

EXAMPLES (1) Production of Member A Cu fine wire having a wire diameter of 130 μm and a length of 150 mm was prepared.
After washing the surface of the Cu fine wire with alkali, wash with water,
Au-Sn plating was performed as follows.

First, a plating bath having the following composition was prepared.

Potassium cyanide (I) potassium: 10 g / L, tin (II) citrate: 4 g / L, sodium citrate: 100
g / L.

Here, a Cu thin wire was immersed to form a cathode, a Pt-coated Ti plate was placed at the counter electrode, and electroplating was performed under the following conditions while stirring the plating bath.

Current density: 0.5 A / dm ² , bath temperature: 40 ° C.
pH: 4.2, plating time: 60 minutes.

On the surface of the Cu fine wire, A having a thickness of about 20 μm
The u-Sn plating layer was formed.

Next, the obtained Au—Sn plated wire was subjected to wire electric discharge machining to produce a short wire piece having a length of 1000 μm. A total of 140 short wire pieces were obtained.
Then, these short wire rod pieces were put into an aqueous solution of ferric chloride having a concentration of 3 mol / L (liquid temperature: 20 ° C.) for 0.5 hours while slowly stirring the liquid, and then taken out. Outer diameter 170μ
m, 140 members having a through hole diameter of 130 μm and a length of 1000 μm were obtained.

(2) Properties of Member The components of this member were analyzed by plasma emission spectroscopy. As a result, Au: 78% by weight, Sn: 22% by weight
Met.

2. Further, this member was subjected to differential thermal analysis under the following conditions, and its melting point was measured.

Reference substance: alumina, heating rate: 10 ° C./min from room temperature to 1200 ° C., range: ± 50 μV, chart speed: 2.5 mm / sec.

As a result, an endothermic peak was observed at a temperature of 312 ° C.

3. Further, the crystal structure of this member was identified by an X-ray diffraction method. As a result, a slight diffraction image of Au was observed at around 2θ: 77 °, but as a whole it was a halo diffraction image, and it was confirmed that this material was mainly composed of an amorphous structure. Was.

The same X-ray diffraction was performed on the material for which the differential thermal analysis was completed.
A sharp diffraction image corresponding to the u-Sn alloy was observed. That is, the material was converted from an amorphous structure to a crystalline alloy by melting.

(3) Welding with Ferrule A Kovar ferrule having a length of 5 mm, an outer diameter of 1.0 mm, and a center hole diameter of 150 μm was prepared. An electroless Ni plating layer having a thickness of 2 to 3 μm and an Au electroless plating layer having a thickness of 0.1 to 0.2 μm are formed on the surface of the ferrule in this order. A fiber core having a fiber diameter of 125 μm was inserted through the ferrule, and its tip was positioned so as to protrude by about 400 μm.

Then, after the member of the present invention is externally fitted to the end of the fiber core, a high-frequency induction heating coil is arranged on the outer periphery of the ferrule, and the fiber core and the ferrule are heated to a temperature of 33 °.
After heating at 0 ° C. for 10 seconds, it was allowed to cool to room temperature.

A built-up portion having a height of 300 μm was formed at the boundary between the fiber core and the ferrule, and a sealing structure in which the two were welded together was formed.

Then, the ferrule was fixed and the fiber core wire was pulled, and the strength of the welded portion was examined.
Until the load of 5 kg was applied, damage to the welded portion did not occur.

[0061]

As is apparent from the above description, the use of one member of the present invention can form a sealing structure having sufficiently excellent strength characteristics. This is to greatly simplify the welding operation as compared with the case where welding is performed using a plurality of thin ring foils.

In the case of the member of the present invention, the outer diameter, the diameter of the through hole, and the length can be easily selected, and furthermore, a large number of members can be manufactured by one electroplating. The production method is highly productive and has an extremely high industrial value.

[Brief description of the drawings]

FIG. 1 is a perspective view showing one example of a welding Au-Sn member of the present invention.

FIG. 2 is a partial cross-sectional view showing an Au—Sn plated wire A1 which is an intermediate material of the present invention.

FIG. 3 is a cross-sectional view showing a short wire piece A2 as an intermediate material of the present invention.

FIG. 4 is a sectional view schematically showing an optical module.

FIG. 5 is a partially cutaway sectional view for explaining welding of a ferrule and a fiber core;

FIG. 6 is a sectional view showing a state after welding.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Housing 2 Light emitting device 3 Optical fiber 3a Coating of optical fiber 3 3b Fiber core wire 3c Spherical lens 4 First ferrule 4a End face of ferrule 4 5a, 5b, 5c Sealing material 6 Second ferrule 7 Au-Sn alloy Ring foil 8 Au-Sn member for welding 8a of the present invention 8a Through hole of member 8 9 Long wire rod 10 Au-Sn plating layer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01S 5/30 H01S 3/18

Claims (2)

[Claims] 1. The overall shape is a short pipe shape,
A welding Au-Sn member comprising an Au-Sn intermetallic compound having an amorphous structure. 2. A long wire made of a conductive material is made of Au-S.
n-plating to obtain an Au-Sn-plated wire; cutting the Au-Sn-plated wire to a desired length to obtain a short wire piece; and forming the core of the short wire piece. A method of manufacturing a welding Au-Sn member, comprising: removing a material.